Month: January 2024

Oh et al. showed that US consumers are willing to pay higher prices if the fruit were grown locally in a wild friendly farming way that conserve birds.Birds can also play a detrimental role in agroecosystems, specially species of blackbirds , cardinals , doves and parakeets . These species can take advantage of the concentration of food resources in agricultural fields causing reduction in yields .The degree of crop damage may be related to the type of crop grown and other habitat features. For example, in Argentina monk parakeets were found to prefer sunflower instead of corn . According to Fuller-Perrine and Tobin major grape damage in North American vineyards is caused by European starlings , American crows , House finches and Common grackles . Somers and Morris reported that grape damage in Canadian vineyards was related mainly to the presence of the exotic European starling that were found in flocks from 5-200 individuals/daily, although some other native birds were also found but in reduced numbers and just a few times during the season. The same study showed that American crows were also found in large numbers but they did not forage in vineyards. There is spatial localization of bird grape consumption, where upper vine tiers and vineyard edges exhibited more damage than lower tiers and grapes growing at the center of the vineyard . In California, bird damage was estimated to cause profit loss in nuts of 9.6%, in grapes of 9%,best grow pots in berries of 5.7%, and in fruit orchards of 5% . Different techniques have been employed in order to reduce the damage caused by birds to crops.

Berge et al. reported that one effective method was the utilization of electronic devices that emit alarm sounds and distress calls that drive off birds. Although netting the crops was the most effective method to avoid bird damage, it is expensive. The use of nets that cover grapes was proposed as an effective way to control bird grape consumption , but other studies did not find this method to be as effective . Baldwin et al. reported that the most common methods used to avoid bird damage in California were frightening devices, exclusionary devices, and shooting.Agriculture has transformed nearly 40% of the earth’s surface , causing direct effects on wildlife populations, among them birds. Intensive agriculture is considered one of the main threats to biodiversity . Agricultural intensification has been linked with wildlife decline . For example, Karp et al. found in tropical agroecosystems that beta diversity is reduced by 40% under intensive agriculture.Implications of land use change are related not only to habitat loss, fragmentation and lack of connectivity in the agricultural matrix, but direct impacts on species. Global vertebrate extinction has increased significantly since the rise of industrial society when compared to historic and prehistoric times . This process of “defaunation” corresponds not only to a loss of species but also to shifts in species composition, function and interactions that impact the provision of ecosystem services and human well-being . Land use change is one of an interacting group of drivers of extinction . A worldwide multi-taxon study reported strongly negatively impacts on composition and diversity of species by land conversion from primary vegetation to agricultural landscapes, forest plantations, and urban areas . In a global analysis of local diversity affected by increased human population and land use change scenarios from the Intergovernmental Panel on Climate Change. Newbold et al. showed that by the end of the century the within-the same land use of the most impacted habitats species richness will be reduced by 76.5% on average, total abundance by 39.5% and rarefied richness by 40.3% of 47 taxonomic terrestrial groups .

These impacts are more likely to disproportionally occur in countries with high biodiversity but economic poverty although this projection could change if there is sufficient social pressure to revert trends . For example, in Mexico the rate of crop expansion over native grasslands/shrubland in the Chihuahua desert, negatively impacted the overwintering habitat of 28 migratory species in North America . Pan-tropical bird occurrence and abundance decreases along a anthropogenic land use intensity gradient compared to undisturbed habitats . In Germany, models predict that conversion from agriculture to bio-fuel production in order to reduce carbon dioxide emissions will have negative effects on biodiversity. A loss of 10% of the present farmland bird population by 2050 is estimated with expansion of bio-fuel monocultures . In another case study of land use change and bio-energy crops, Everaas et al. modeled the impact on bird breeding of changes from current farms to bio-energy monoculture crops, and reported negative impacts for the majority of species analyzed, suggesting that biodiversity impacts of the spread of intensive monocultures in Germany cannot be mitigated only by conserving 10% of land surface set aside within farms, a current European agro-scheme practice.Under current global scenarios of land use change and scaling rates of per capita consumption, reconciling agricultural production and biodiversity conservation goals is a priority . Different approaches have been proposed in order to achieve these goals. One of the most debated questions is how can we best produce crops to enhance food security while conserving natural areas . Land sharing and land sparing strategies as well as a combination of both have been proposed . The land sharing approach proposes agroecology as a strategy to spatially, temporally, and biologically diversify farms and to increase the value of the agricultural matrix for wildlife habitat . This approach values the relationship of humans with nature and integrates traditional knowledge into management of agroecosystems .

The main contention of the land sharing approach is that low yields from non-intensive agriculture will promote agricultural expansion detrimental to natural areas . However, this yield gap argument has been contested by Ponisio et al. by meta-analysis showing that diversification of organic agriculture can reduce the yield gap between conventional and organic agriculture from ~19% to ~8%. Land sparing proponents have favored high agrochemical input levels aimed at enhancing crop yields and argue that with high production in target crop areas, natural areas land surface will be spared from conversion to crop production . However, current agrochemical use can impact non-target wildlife species. For example pesticide applications in arable farms decrease arthropods that are consumed by Yellowhammer in the reproductive season, negatively impacting their breeding performance . Use of highly toxic pesticides have a direct effect on bird population in US grasslands . Intensive systems proposed by land sparing proponents are characterized by low levels of biodiversity and low heterogeneity of agricultural landscapes . Monocultures can affect the bird species guild in different ways and deplete bird diversity . The land sparing approach assumes that current natural areas will be preserved by preventing further land use conversion to agriculture, but this theoretical assumption does not always hold due to market-driven economic incentives ,plants in pots ideas that promote land use changes linked to the expansion of bio-fuels and land-grabbing initiatives . A third approach for biodiversity conservation in agricultural landscapes proposes an integrated strategy where elements of land sparing and land sharing can be useful for conservation, depending on factors such as the levels of fragmentation, the socio-political conditions, and the level of previous disturbance of the environment . For example, spatial prioritization for conservation in South America shows that when the top 17% of priority areas were analyzed, the land sharing alternative resulted in a better conservation outcome than the land sparing alternative , although in some areas a mixed strategy better matched conservation priorities . In southeastern Australia, Michael et al. found that land sharing strategies were successful for birds, many of which are of conservation concern. However, land sharing had limited effects on conservation of other vertebrates , suggesting that mixed alternatives should be explored .Natural ecosystems provide irreplaceable biotic and abiotic conditions for birds, in particular for highly specialized forest-dependent birds, pollinators birds, migratory species, and endemics . Forest patches and fragments can contribute to higher bird diversity within the agricultural matrix and increase ecosystem services provided by birds . In Madagascar, Martin et al. compared a biological corridor of native vegetation and the surrounding agricultural matrix and found higher species richness in the agricultural mosaic of crops than in the corridor. In particular, some functional groups such as carnivores, terrestrial and sallying insectivores, and granivores were significantly more abundant within the agricultural mosaic, although the majority of these species were generalists and the endemic species remain associated to forest.

It should be emphasized that the agricultural mosaic is defined as a complex diversified system of different crops, where scattered trees, small forest patches, and other secondary habitats support various species. In a fragmented native forest in southern Chile, Carneiro et al. found that isolated native trees supported the abundance of the endemic parakeet within agricultural landscapes. Scattered trees provide key resources for refuge, roosting, nesting, feeding and connectivity within agroecosystems . Riparian corridors within a mosaic of low intensity managed crops provided significant habitat and connectivity for two forest specialist frugivorous birds in Costa Rica . Mangnall and Crowe found in South Africa that retaining native vegetation within a landscape with arable crops could increase bird species richness in comparison with monoculture crops. In the agricultural landscapes of the US Midwest, fragment size of riparian forest was positively related with the occupancy by Neotropical migratory bird species and species richness Forest edges represent ecotones between agroecosystems and native vegetation. These transition zones can host different bird species. In the North American Corn Belt Best et al. , reported that abundance of birds was higher along forest edges adjacent to corn fields in comparison with grassland edges or the center of cornfields. The same study, also stablished that bird abundance decreased in larger corn fields , which fits the patterns of land intensification suggested by Sauerbrei et al. . Similar results were recovered by Terraube et al. , who reported that the bird abundance of insectivores, under story gleaners, resident and migratory birds, cavity nesters and under story nesters increased in the interior of forest edges. Floristic composition and habitat structure were relevant for bird abundance and composition within the forest edges . Ecological and biological traits as well as natural history of different birds influence the adaptability of the different species to anthropogenic environments. For example, Figure 1 shows a number of different species enhanced by agricultural land cover in central Chile, where species composition changed between crop types but also between seasons . Examples of these varying associations of birds with crops, agricultural land cover, management, and ecosystem type are summarized in Table 1.Some bird species have a direct relationship with pastures and are considered grassland obligates, thus depending on agricultural management for their conservation . Cattle stocking at high density directly decrease habitat quality and influence the abundance of arthropods in prairie systems, which in turn influence the availability of prey for insectivorous birds . In a grazing experiment in Florida , Willcox et al. found that along with the loss of structural diversity in more intensively managed grasslands, total richness and abundance of birds decreased in monoculture grassland, although analysis by subgroups showed that some increased with the grazing intensity. Grasslands can also provide alternative feeding habitats, as in the case of the Austral Thrush in central southern Chile. Austral thrushes are considered frugivorous forest birds that, due to conversion of forest to grassland for cattle, were favored by the increase in soil annelids which complement their diet when fruit sources are scarce due to seasonal variation . In the case of the native grasslands of the southern cone of South America, the Pampas, land use change has converted most of the Pampas to rangeland or croplands . In the Pampas, vegetation structure was the main driver of the bird community composition . In terms of grazing pressure, low rates of nest destruction were found in Canada, although the nest destruction was positively correlated with grazing pressure . Silvopastoral systems combines grazing lands with trees and can be considered within the agroecological strategies of improve the agricultural matrix to support biodiversity . In Spain and Portugal ancient cork oaks known as “dehesa” and “montado” forest respectively, are used for different purposes but also can provide biodiversity and ecosystem services . In a “montado” systems, silvopastoral areas with higher heterogeneity supported high richness of bird guilds .

To draw these conclusions, we need to recall the conditions under which the model predicts conflict to occur. First, the model suggests that conflict is likely if aid causes a large shift in the balance of power between governments and insurgents. It should therefore be possible to avoid conflict by making sure that development projects do not affect this balance of power. One way of achieving this is to cooperate with both governments and insurgents in designing the project and delivering the aid. An example of this approach is a recent cooperation of Japan’s International Cooperation Agency with the MILF in extending aid to parts of Mindanao in the southern Philippines. However, while cooperating with insurgents can be a successful strategy in some cases, there are many contexts in which it may not be feasible or ethical. In these cases, we turn to the second condition under which our model predicts conflict: if insurgent attacks have a large negative effect on the probability that the project will be successful. This suggests that violence can be minimized by focusing aid on a small number of projects and heavily defending them. This would make it harder for insurgents to sabotage the projects and thus help deter violent attacks. In addition, it may be desirable to weaken insurgents’ capacity before the start of the project by military means, following a “clear, hold, build” strategy. While more research on the precise mechanism through which development projects cause conflict is needed, our research shows that by combining careful empirical and theoretical analyses,large plastic garden pots we can identify the causal effects of development interventions and use this information to draw conclusions for development policy.It has been over 30 years since China abandoned its large communal farms. Each “farm” had thousands of workers, assigned to production brigades.

The communes were run by inefficient and corrupt top-down management, and state monopolies procured farm production at fixed prices. The communal farming system was a complete disaster, underscored by the 1959–61 famine when an estimated 30 million Chinese residents starved to death. The communes were broken up in the late 1970s in favor of small, family-run plots with profit incentives tied to production and market-determined prices. The economic reforms that started in China’s agricultural sector in the late 1970s then spread to other parts of the economy and we all know the rest of the story. China has enjoyed very strong income growth and has emerged as a main driver of global economic growth. Deng Xiaoping moved China from a top-down planned economy to a market economy, and the results have been nothing short of phenomenal.Today, China produces 18% of the world’s cereal grains, 29% of the world’s meat, and 50% of the world’s vegetables. This success makes China the world’s largest agricultural economy, and it ranks as the largest global producer of pork, wheat, rice, tea, cotton, and fish. In fact, the value of China’s agricultural output is twice the U.S. total. See Figure 1 for China’s share of world food production across various commodities. With only 9% of the global sown area, today China produces about 20% of the world’s food—a miraculous turnaround since the struggles faced by China’s agriculture in the 1960s and 1970s under the collective farms. Despite predictions that China was going to starve the world, instead China has been able to balance its domestic grain supply and demand, with the exception of oil seeds.

Will this continue? After joining the WTO in 2001, China has played a greater role in world agricultural trade. China dramatically increased its trade dependence in agriculture, and it is currently the fifth largest exporter and fourth largest importer of agricultural products in the world. China’s substantial increase in fruit and vegetable production was a major factor behind its agricultural export growth. With imports growing faster than exports during the post-WTO accession years, China reversed its long-time status as a net agricultural exporting country to that of a net importing country since 2004. As expected, with liberalized trade and market forces at work, China increased its imports of land-intensive agricultural products. Most of the increased imports came from soybeans and cotton. Today cotton and soybeans account for 43% of China’s agricultural imports, a very concentrated portfolio. China is the world’s largest importer of soybeans and cotton, accounting for 60% of global soybean imports and 40% of cotton imports. China’s agriculture is supporting a population of over 1.3 billion people today, compared to about 500 million in 1950, on a relatively fixed agricultural land base and shrinking water supply. The tale of China’s agricultural success in meeting this challenge is two-fold. First, China has enjoyed very strong agricultural productivity growth, measured as the difference between growth of agricultural output and the growth of all inputs aggregated. Second, China has poured on farm inputs. China’s annual agricultural productivity growth rate was 2.5% from 1970– 2007, even higher than Brazil’s and much higher than in the United States . At the same time, China’s farmers have intensively applied more chemicals and fertilizer to their crops to try and overcome the limitations of scarce land and water. In the 1980s and 1990s agricultural production in China grew by 5.3% per year, much higher than in other populous countries such as India and Indonesia. Most of this growth came through yield gains rather than through increases in planted area. China boosted grain production by more than 50% during this time period. Grain production in 2010 was 80% above the 1978 level.

Per capita food supply in China rose from 2,328 calories per day in 1980 to 3,029 calories in 2000, a 30% increase in just 20 years. China’s chemical fertilizer use has roughly doubled over the past two decades while pesticide use and mechanized inputs have increased even faster. China has slightly less agricultural land than the United States, but its chemical fertilizer use is now double that of the United States. China uses about one-third of the world’s nitrogen fertilizer and 31% of phosphate fertilizer on its 9% share of the world’s agricultural land. Unfortunately, the strong growth in chemical input use has resulted in considerable agricultural pollution.Let us not forget that China remains a developing country. In China 36% of the population still lives on less than $2 per day and most of these poor are in the countryside. Even though economic reform started in agriculture, non-agricultural economic growth has left the farm population to fall behind. The image we have of the new affluent Chinese consumers buying Gucci handbags in modern boutique shops does not apply to the nation’s farmers. China’s farms remain very small and the work remains highly labor-intensive and difficult. Almost 300 million workers remain in agriculture,raspberry plant pot and most farmers remain very poor, with per capita incomes about $1,000/yr—less than one-third of the average urban income. The proportion of agriculture in China’s GDP dropped from 28.1% in 1978 to 11.8% in 2010. Yet 38% of the labor force remains in agriculture , a ratio that is far too high given China’s level of development. As a result, labor productivity in agriculture remains low. Raising farmers’ incomes is one of the major policy challenges facing China’s policy makers today. This may require relaxing a long-standing policy goal of food self-sufficiency. National food security goals require a very high grain self-sufficiency percentage, and farmers typically earn less money growing grain compared to other higher-valued crops. Between 1981 and 2005, the percentage of people living below the poverty line dropped from 84% to 16.3%. This was part of the success story. But the challenge is that China’s Gini coefficient grew from 29 in 1990 to 42 in 2007, reflecting a strong increase in income disparity within a relatively short period of time. Income inequality in China is now similar to that in Mexico, but the irony is that China is a communist country.Income growth and urbanization, and the resulting changes in dietary patterns, particularly in developing countries like China, have important implications for food consumption and agricultural trade. Urbanization leads to a decrease in calorie consumption per person, but greater demand for processed food products. Low-value staples, such as cereals, account for a larger share of the food budget of the poor while high-value food items, such as dairy and meat, are a larger share of the food budget of the rich. So rising incomes are usually associated with increased demand for meat, horticultural, and processed food products.

In turn, increased demand for meat will result in increased demand for feed grains and protein meals. For instance, China’s per capita incomes have more than tripled in the past 20 years and, as a result, some dramatic changes in food consumption have taken place in that country. Per capita meat consumption has more than doubled in the last 20 years in China. Meeting increased demand for meat and other dietary changes will continue to be a challenge for China. This will require more water supplies because it takes about 2,000 liters of water to produce 1kg of wheat, compared to about 16,000 liters of water for 1kg of beef. Today, much of China’s agriculture is very irrigation-dependent. With 20% of the world’s population and 7% of its fresh water, China faces important water issues. Agriculture uses 76% of the country’s water, but it is facing greater competition from urban areas. In the relatively dry northern region, the water availability per person is only a quarter of that in the south. Yet the north is where almost half China’s population lives, and where most of its maize, wheat, and vegetables are grown. Groundwater is intensively used in the north, but not in the south. This means that water efficiency must be improved in the north. Pricing of surface water and groundwater could play a greater role in the allocation. China’s farmland essentially belongs to local governments, a holdover from the commune era. This means that land cannot be bought or sold by farmers, only leased. This raises a number of policy issues with respect to the transition of China’s agricultural sector towards a more modern industry. Lack of land ownership discourages investment and consolidation into larger and more efficient farms. Land-use rights are now attached to village residency, discouraging permanent out-migration from agriculture and keeping farm incomes low.Agriculture is arguably the sector of the economy most directly exposed to climate and thus likely to be affected by climate change. To date, however, there exists considerable disagreement about the magnitude of potential impacts. Disagreement stems from differences in both methodology and empirical measurement. The recent paper by Deschˆenes and Greenstone , henceforth DG, is an important contribution to the climate impact literature and to the debate on economic methodology. DG’s findings and conclusions hinge on two key factors: how they navigate the distinction between climate and weather, and the metrics they use for measuring both weather effects and economic impacts. In this paper we revisit DG in an attempt to reconcile differences between their work and our own. Climate scientists emphasize the distinction between weather and climate. Weather is what occurs at a particular moment in time – typically, precipitation and temperature. Due to natural variability, weather fluctuates from one hour to another, one day to another, one month to another, and one year to another. Climate, by contrast, is the long-run pattern of weather over time. To climate scientists, therefore, climate change has a very different significance from weather change. A change in weather is inherently short-run, while climate change is a shift in the long-run pattern. Because these are different phenomena, it is not surprising that they also have different economic implications. Differences between weather and climate have implications for the choice of an economic metric. When dealing with climate, the appropriate metric is some measure of the long-run profitability of using the land for agriculture – the equivalent of the permanent income from farming. This is an economic rather than an accounting measure, and it generally has to be inferred through some proxy.

The direct effect of disembodied technical change in the food processing industries, possibly induced by changing output demand, has clearly been MA-saving, even adapted for the conflicting forces from innovation, and rigidities in the agricultural sector, that have affected the virtual prices of agricultural materials and capital.Our goal is to evaluate costs, input demand , and output price behavior in the U.S. food processing industries, and their dependence on various pecuniary and technological forces. A cost function specification recognizing virtual prices, and augmented by an output pricing equation, provides the foundation for this exploration. Such a framework assumes that cost minimizing input demand behavior based on observed input prices and output demand characterizes firms in the food processing industries. The potential for imperfect markets from quasi-fixity and deviations from perfect competition is incorporated through the virtual price specification. The resulting cost structure representation allows us also to characterize profit maximizing output prices and quantities through an equality of the associated marginal cost and marginal revenue. More formally, the technology and cost-minimizing behavior underlying the observed production structure are typically represented by a total cost specification of the form TC, where Y is output, p is a vector of variable input prices, and r is a vector of exogenous technological determinants. Impacts on this cost relationship of changes in components of the p and r vectors,plastic seedling pots and thus on the implied overall costs and input-specific demands, can be derived via 1st- and 2nd-order elasticities with respect to these arguments of the cost function. The ability to reach minimum possible production costs, as implied from such a cost function specification, is often recognized to be restricted by adjustment costs, which severs the equivalence of the observed input price, pk, and its true economic return.

Alternatively, something that looks like internal adjustment costs may stem from increased factor prices due to some other type of input market imperfection. This could arise from, for example, imperfect competition in the factor market, external adjustment costs or unmarketed characteristics.This representation is particularly appealing if the interaction terms from the former model seem uninformative, but an imperfect market gap, lk seems to exist .If instead Zk appears well approximated by pk, or lk» 0, one can reasonably assume that rigidities or other input market imperfections are not binding constraints on, or determinant of, measured cost structure patterns. We have adopted such a virtual price framework as that most consistent with our data, from preliminary investigation of estimation patterns. Evidence was found, however, for deviations between observed and effective or virtual prices for capital and agricultural materials . The virtual price of capital was therefore defined as p*K=pK+l K, with lk¹ 0 potentially attributable to capital rigidities or unmeasured taxation or quality impacts. Various forms for the deviation between pK and ZK=p*K were tested to establish their empirical justification in terms of significance of the parameters, robustness of the overall results, and plausibility of resulting elasticities. The finding that lMA¹ 0 is plausible for a variety of reasons. In particular, if the processing industries perceive some control over MA prices, the marginal than average price drives MA input demand behavior and lMA>0. This is of interest since the potential for processing facilities to depress prices paid to farmers, has often been recognized as a policy concern. In reverse, embodied technical change could imply lower effective prices of agricultural materials compared to their measured values . The variables in the r vector reflecting the industry’s technological base include the time counter t, as well as t2, to represent disembodied technical change trends and further structural change shifts in the 1980s as compared to the 1970s .

A capital equipment to structures ratio, , is also used to represent technology embodied in the capital stock.6 And dummy variables for the different industries, DI , are included to capture fixed effects.Output supply/pricing decisions are also accommodated in this cost-based model by specifying a pricing mechanism that allows for a difference between output price and marginal costs, or average and marginal cost. This extension of the cost function framework is founded on imposing the standard profit maximizing condition underlying output choice, MR = MC , and assuming that any gap between output price pY and MR results from a dependency of pY on output levels; pY. Alternative treatments with lY specified as a function of other exogenous variables were also tried, with no significant impact.10 To empirically implement this model of the production structure of the U.S. food processing industries, we use a panel of input and output quantities and prices we have constructed from the Census of Manufactures, the NBER productivity database, the Bureau of Labor Statistics, and the U.S. Department of Agriculture. In particular, we distinguished cost shares for three materials aggregates – agricultural materials, food materials , and other materials. To accomplish this, we used Census of Manufactures data to calculate the share of each materials aggregate in the industry value of shipments for which cost information is available.These shares were then adjusted in two ways to arrive at our final estimated materials shares. First, in some food industries, the industry value of shipments includes substantial amounts of materials resales – materials that are purchased but not processed before being resold. We subtracted resales from the value of shipments, to better capture manufacturing output. Second, some small establishments are not required to separately report individual materials purchases, but instead report all materials in an “n.s.k.” category.

We assumed that these establishments allocated n.s.k. shipments to agricultural, food, and other materials categories in proportions equivalent to those reported by the larger institutions. Materials input price series were constructed primarily from commodity PPIs from the Bureau of Labor Statistics. In cases where an industry consumed several specific agricultural or food materials, an aggregated materials price index was constructed from the constituent materials indexes, with each price index weighted by its expenditure share in the Census aggregate. In the few cases where PPI indexes were not available, we constructed indexes from average price series maintained by USDA’s National Agricultural Statistics Service. The resulting data panel covers 5-year intervals from 1972 through 1992, for the 40 4- digit SIC industries in the U.S. food processing sector . The remaining data on output and input prices and quantities were taken from the 4-digit manufacturing NBER productivity database, which is often used as a foundation for production structure studies. Although instrumental variables procedures are often used in the literature on which this study is based, to accommodate potential endogeneity or measurement errors in the data, we did not rely on them for a variety of reasons. First, IV techniques require a somewhat arbitrary specification of instruments, which can be problematic. In addition, models of this form are typically estimated with time series data, and often use lagged values of the observed arguments of the function as instruments. But this is not conceptually appealing for our application due to the short time series,container size for raspberries as well as the 5-year gaps between data points. Although some preliminary investigation was carried out to determine the sensitivity of the results to other IV specifications, the results from these models were more volatile and not as plausible as those from the basic SUR model, which was therefore relied on for the final estimation. Our specification of the arguments of the r vector also warrants additional comment. Including ES as a determinant of the cost structure in addition to the standard time trend t initially seemed important for explaining cost and input demand patterns; the ES parameters, interpreted as the impact of technical change embodied in the capital stock, tended to be significant and plausible. When t2 was also included to capture the potential impact of structural changes in the 1980s, the t2 parameters became statistically significant but the ES parameters tended to be less definitive. Both variables thus seem to capture changes in the 1980s – perhaps toward greater capital- or high-tech- intensity of production. Since the ES parameters remained jointly statistically significant, however, they were retained in the final specification. The parameters estimated from the cost-based model specification TC are presented in Appendix Table 1. The dummy terms are not included in the table since there are too many to be illuminating, but they are primarily statistically significant.

The overall explanatory power of the model is indicated by the high R2 ’s for the estimating equations, including the TC equation which was not estimated but was fitted to determine the implied R2 . Also, many parameter estimates that are not individually statistically significant are jointly significant, such as the ES parameters mentioned above.These estimates were used to construct the cost, input demand, and output supply elasticity and contribution estimates from the decompositions outlined in the modeling section. The measures were averaged across the whole sample, and separately for 1972-1982 and 1982- 1992, and by 3-digit industry, to distinguish temporal and industrial patterns. The elasticity estimates were constructed by computing the indicators for each data point and then averaging across the sample under consideration. Statistical significance of these measures was imputed by constructing elasticity estimates instead over the averaged data; values significantly different from zero at the 5% level are indicated by an asterisk. In most cases the significance implications were not data-dependent, although for some estimates the data point at which the measure was evaluated contributed to evidence of significance. To begin our investigation of agricultural materials use in U.S. food processing industries, we first assess MA demand implications from the decomposition presented in the first panel of Table 1 for the full sample . Recall that such a decomposition weighs the estimated elasticities by the observed changes in the arguments of the function to determine their contribution to observed changes in the dependent variable .First consider the elasticities. The largest MA demand elasticity as well as contribution is from its own price. The own elasticity of eMA,pMA = –1.138 for U.S. food processing industries implies MA demand is fairly elastic; pMA increases have motivated a movement up the demand curve to a lower MA demand level that more than compensated for the price change in proportional terms. Based on observed pMA price changes, this provided a negative contribution of CMA,pMA = -0.062% to the overall observed increase in MA use of 0.038 ; other factors outweighed the negative own-demand effect.By contrast, if the indirect implications from the deviation between the effective and observed input prices are taken into account this effect appears quite a bit smaller; p*MA changed by only 0.036% as compared to the pMA change of 0.055%,21 so the total contribution weighted by this price change would be C*MA,pMA = -0.041. The lesser apparent growth in p*MA than pMA could derive from various factors – including augmented quality that is not captured in the measured values – but is inconsistent with increases in market power.That is, l MA appears to capture some form of technical change or productivity embodied in MA, that represents the impact of technical innovation in agricultural markets transferred to the next level of the food chain – food processing.This effect will be evaluated more explicitly below in the context of the indirect components of the t impact within the CMA,t decomposition. All other inputs are substitutable with MA, as is apparent from their positive price elasticities, and the observed increases in these input prices over the sample period thus imply positive shift effects on MA demand that in sum seem to more than compensate for the own price effect. In particular, MA seems somewhat substitutable with both MF and MO, but the contributions of pMF and pMO changes to observed MA demand adaptations are not substantial since the price changes have not been large; CMA,pMF=0.0035 and CMA,pMO=0.016. Rising relative prices of labor and energy – which have been experienced in these industries for most of the recent past – have also had positive effects on MA use, although their contributions are limited by smaller substitution elasticities; CMA,pL=0.012 and CMA,pE=0.004. The statistically insignificant elasticities for pL and pMF suggest that MA-MF substitution is driven more by demand than price impacts. The contribution of pK increases to MA demand is much greater than the price effects associated with other inputs, especially if adjustments in effective pK, p*K, are recognized.

The carryover of fire activity from forest clearing into subsequent years is a cumulative process, such that total high-frequency fire activity in any year represents burning for multiple years of forest loss . For example, elevated fire activity during 2004 in Mato Grosso is the product of deforestation rates during 2002–2005 and high fire frequencies in 2004 for cropland and pasture deforestation. In general, fire frequency is highest for the year in which the deforestation was mapped. For cropland deforestation, fire frequency is similar in the year before and following deforestation mapping. For pasture deforestation, fire frequency is consistently higher in the year following deforestation mapping than the year before detection of deforestation. The number of days on which fires are detected at the same ground location is higher for areas undergoing deforestation than for other fire types in Amazonia, and fires on 3 or more days at the same ground location are almost exclusively linked with forest conversion. During 2003–2007, more than 40% of all high-confidence MODIS fire detections within Amazonia were associated with deforestation. Within this subset of repeated fire detections, container growing raspberries variations in fire frequency suggest that carbon losses from deforestation vary with postclearing land use. Deforestation for cropland may involve burning on as many as 15 days during the same dry season as woody fuels are piled and re-burned to prepare the land for mechanized agricultural production.

Forest conversion for pasture is characterized by fewer days of burning during the dry season, on average, and fewer years of high-frequency fire detections than conversion to cropland. Forests without evidence for cropland or pasture usage following deforestation detection have the lowest fire activity. Higher fire frequency associated with mechanized deforestation suggests greater combustion completeness of the deforestation process compared with less intensive clearing methods. Whereas the first fire following deforestation may consume 20–62% of the forest biomass depending on fuel moisture conditions , piling and burning trunks, branches, and woody roots many times in the same dry season may increase the combustion completeness of the deforestation process to near 100% . Based on published combustion completeness estimates of 20% or 62% per fire, repeated burning during the deforestation process could eliminate initial forest biomass after 5–22 fire events. Combustion completeness and fire emissions from recent deforestation may be higher than previous estimates for deforestation carbon losses. Mechanized equipment can remove stumps and woody roots in preparation for cropland such that both above and below ground forest biomass are burned. Burning woody roots may increase the fire affected biomass by as much as 20% . Fires that burn piled wood are likely to be at the high end of the published range for combustion completeness, given field measurements of high fire temperature and longer duration of flaming and smoldering stages of combustion in piled fuels compared with pasture or initial deforestation fires . High fire frequency for recent deforestation also generates higher total fire emissions compared with previous estimates that assume that a majority of carbon is lost as CO2 from heterotrophic respiration of unburned biomass .

These attributes of fire use for mechanized deforestation in Amazonia challenge the basic assumptions that monitoring deforested area and estimating above ground biomass of tropical forests are sufficient to estimate carbon emissions from deforestation . Failure to consider the evolving roles of post clearing land use on combustion completeness could introduce substantial uncertainty into calculated reductions in carbon emissions from declines in deforestation rates. Findings in this study suggest that average combustion completeness for recent deforestation may be two to four times greater than that estimated for deforestation during 1989–1998 , increasing per-area gross fire emissions for the current decade by a similar magnitude in regions where mechanized deforestation is common. Deforestation for highly capitalized, intensive agricultural production may also reduce the rates of land abandonment to secondary forest compared with previous periods of Amazon colonization, reducing the offset of gross fire emissions from regrowing forests . In addition to further field measurements, we are currently developing a detailed model representing variations in forest biomass, combustion completeness of new deforestation, and offset of fire emissions from regrowing vegetation to more accurately quantify the influence of agricultural intensification on carbon emissions in the region. The use of heavy equipment to manage forest biomass may also change the nature of trace-gas emissions from deforestation. Emissions factors for CO2 are relatively similar for flaming and smoldering phase combustion, but emissions of CH4, CO, and some VOCs from the smoldering stage of deforestation fires are nearly double than that during the flaming phase . The balance between flaming and smoldering phase combustion for 2nd–Nth fires during the forest conversion process is unknown. If emissions ratios do change during the course of the deforestation process as a function of the size or moisture content of woody fuels, the frequency of satellite-based fire detections provides one method to characterize time-varying trace gas emissions for Amazonia. Combining daytime and night-time observations from multiple sensors may better characterize the duration of individual fires to allow more direct interpretation of satellite data for trace gas emissions.Interannual differences in total and high-frequency fire activity highlight trends in both economic and climate conditions across Amazonia.

Concentrated fire activity in Mato Grosso state during 2003–2004 is consistent with peak deforestation for cropland, driven, in part, by high prices for soybean exports . Carryover of fire activity from previous years’ deforestation also contributes to high fire detections during 2003–2005 in Mato Grosso. Thus, reductions in fire intensive cropland deforestation during 2005 do not result in a shift in fire intensity away from central Mato Grosso state until 2006. Regional differences in concentrated fire activity also highlight the role of climate in mediating human caused fires. Roraima, Acre, and Tocantins states in Brazil show dramatic differences in fire activity during 2003, 2005, and 2007. During drought periods in 2003 and 2005, Roraima and Acre had approximately seven and four times as many fires as under normal climate conditions, respectively. The fraction of high-frequency fires was also highest during these drought years, supporting the results from recent studies showing anomalous fire activity and large areas of burned agricultural land and forest in drought affected areas . Future work to verify the detection of active forest burning by satellites is needed to quantify the contribution of forest fires to the regional patterns of high-frequency fire in drought years. In 2007,raspberries for containers anomalous fire activity was driven primarily by low-frequency fires concentrated in southeastern Amazonia and a return to 2004 levels of deforestation fire activity in southeastern Bolivia and the Brazilian states of Mato Grosso and Para´. These examples suggest that even localized drought conditions can spur anomalous fire activity in the presence of anthropogenic ignition sources for deforestation and agricultural land management with important consequences for gross fire emissions. The timing of fires for forest conversion may influence the likelihood of fires escaping their intended boundaries and burning neighboring forest and Cerrado vegetation. Deforestation for pasture contributes more fires during the late dry season when forests in Mato Grosso state may be most flammable after 3–5 months with little rainfall. More even distribution of fires for cropland clearing throughout the dry season may reduce the risk of forest fires. Different timing for cropland and pasture deforestation fires is consistent with management practices for intensive agriculture; mechanized crop production with chemical fertilizers is less reliant on the ash layer from deforestation fires for soil fertility than cattle pasture or smallholder agriculture land uses. However, deforestation fires for both cropland and pasture in Mato Grosso state were common during July and August of 2003–2005 despite local regulations prohibiting fires during these months to minimize the risk of unintended forest fires . Because the most frequent fire detections are indicative of mechanized deforestation and post clearing land use for intensive agricultural production, monitoring cumulative fire frequency could aid the rapid detection of mechanized forest clearing. Improved geolocation and fire detection capabilities of the MODIS sensors compared with previous satellite instruments enable a higher resolution investigation of these patterns of repeated fire activity.

Despite the moderate resolution of the MODIS sensors, information on fire frequencyat 1-km resolution is commensurate with clearing sizes for mechanized crop production in Amazonia that average 3.3 km2 . Active fire information has not previously been merged with land cover change estimates for deforestation monitoring.Our approach to quantify the contribution of deforestation to satellite-based fire activity and characterize individual forest conversions in terms of fire frequency is intentionally conservative. Because of issues of both omission and commission of fires by the MODIS sensors, it is not possible to determine the exact timing or frequency of all fires for the conversion process. We begin with a high-confidence subset of active fire detections to reduce data errors from spurious fire detections over tropical forest . Next, we link deforestation fire activity to high-frequency fire detections, such that fires must be detected at the same ground location on 2 or more days, despite omission of fires from MODIS attributable to fire size , orbital coverage , and the diurnal cycle of fire activity . Despite well-defined changes in land cover, 12% of cropland and 27% of pasture deforestation events in 2004 showed no fire activity in the high-confidence subset of fire detections. Therefore, low-frequency and omitted fires likely increase the fraction of total fire activity in Amazonia linked to deforestation. Because of omission of active fires by MODIS, a more robust method to estimate combustion completeness of the deforestation process may be to combine active fire detections from multiple sensors with other satellite data on deforestation or vegetation phenology to follow the fate of cleared areas over time.A phenomenon that I term REDD Out Ahead is a recurring theme for both REDD negotiators and REDD policy advocates, but for different reasons. For negotiators, REDD out ahead is indicative of a fear that of a lack of coordination between REDD and other elements of the climate schemes. Several of my interview subjects sees this as stemming in part from a lack of capacity for some parties to monitor all streams of the negotiation. A related concern is the unwillingness or inability to assign sufficiently competent staff to the REDD negotiations themselves. On the flip side, some advocates frame the rapid progress of REDD as a point of pride and evidence that the UNFCCC is a viable venue for climate policy. Another set of advocates and scholars, meanwhile argue that the rapid progress of REDD is indicative of the market orientation of REDD and attendant concerns about issues of environmental justice.Every one of my interview subjects spoke of drivers in a way that evoked agriculture. Despite that fact that agriculture is not at present mentioned in the REDD text, the interviewees suggest that the term “drivers of deforestation” is very nearly a proxy for agriculture. Some subjects see this is development as foundational for the future of REDD. Generally speaking, this camp argues that “stove piping” of land use issues is to be avoided. The concern is that this is inefficient for monitoring, and that “you can’t get there from here”, meaning that reducing tropical deforestation appreciably cannot occur without addressing agricultural issues. However, an even larger portion of the party representatives I interviewed see agriculture as what one interviewee described as the “third rail” of international governance in general and in particular environmental governance. “I know we can’t get there from here without agriculture,” one subject told me, “but look, I am as big an advocate for a new treaty as they come and with agriculture in the mix it’ll never happen.” When pressed, the rationale is that the agriculture deforestation link inherently involves grappling with international trade of agricultural commodities. One respondent described this as a, “$100 billion dollar issue.” Among, advocates, however, there is a strong push to get agriculture on the REDD bandwagon. One advocate describes REDD as the last best chance to revive overseas development assistance for agriculture .For several interviewees, the drivers theme heralds a broader trend in decentralizing the principles and content of REDD. These feelings closely cohere with how Boyd describes the emerging polycentricity of REDD.

Average total nitrogen was similar across all hydrologic zones and decreased with depth. The C:N ratio ranged from 8.9 to 11.7 and was relatively consistent with depth in all hydrologic zones . Average KCl-extractable NO3 and NH4 were highest in the flow path zone and generally decreased with depth.There was no significant difference in DNP for any wetland zone between ambient conditions and glucose C-source amendment. However, adding glucose and nitrate significantly increased DNP in all three hydrologic zones . The largest increase was seen in the flow path zone soils at 10 cm . In the upper 10 cm, it is also notable that the maximum measured DNP under non N-limiting conditions was much higher in the flowpath zone. DNP was relatively low and similar for the 50- and 100-cm depths for all hydrologic zones and amendments. Amending the 50- and 100-cm depth soils with glucose or nitrate produced no significant response in DNP. When glucose and nitrate were added there was a slight increase in DNP in a few instances .The first statistical model tested was the most complex and hypothesized that log10 DNP was the result of wetland zone, sample depth, amendment, and soil organic carbon content. The two-way interactions of depth and hydrologic zone, depth and amendment,blueberry pot and hydrologic zone and amendment were also included in this preliminary model. Soil organic carbon content had no significant effect on DNP. There were also no significant interaction effects between depth and hydrologic zone, or zone and amendment.

Depth had a highly significant effect on DNP . DNP was an order of magnitude higher at 10 cm than at the 50- or 100- cm depths for all treatment/wetland zone combinations . There was no significant difference in DNP between the 50- or 100-cm depths. Because of the huge disparity in DNP among depths, the 10-cm depth was separated from the 50- and 100-cm depths for further analysis. At the 10-cm depth, both wetland zone and amendment had a significant effect on DNP, but there was no significant interaction between amendment and wetland zone.With all amendments, DNP showed the following pattern among hydrologic zones: flow path > fingers > uplands . This same pattern was observed with the nitrate removal rates that were calculated from piezometer/pore water depth profiles. The calculated removal rates were similar in magnitude to DNP removal rates.The wetland was highly effective at removing nitrate with an estimated 75% total NO3-N removal efficiency for surface and subsurface flow paths combined . The wetland received 5127 kg of NO3-N from input water originating from agricultural return flows and exported 714 kg of NO3-N in output water during the 6-month irrigation season . Approximately 4122 kg NO3-N infiltrated into the wetland soil as seepage, and of this amount, 547 kg NO3-N was lost as seepage below 100 cm. Thus, 3866 kg of the in flowing NO3-N load was either immobilized biologically via plant and microbial uptake or lost from the system via biotic and abiotic transformations . Patterns of N loading from inflows were similar among zones; increasing in the middle of the season. Outflow N loads were consistently low throughout the study period .

NO3 loads lost via deep seepage were low during the beginning of the season and remained low in flow path and upland zones. In the finger zone, however, a dramatic increase in NO3 seepage loads occurred from late June through September . Seasonal retention efficiencies for NO3-N loads in seepage water were 95, 81, and 70% for the flow path, finger, and upland zones, respectively . A moderate decrease in surface water NO3-N concentration between inflow and outflow locations indicates some NO3-N removal via surface processes , however, high measured rates for DNP in surface soil and significantly lower pore water NO3- N concentrations at 50- and 100-cm depths indicate that subsurface denitrification was a dominant nitrogen removal mechanism . Notably, the NO3-N removal rate estimated via non-nitrate limited DNP values considering all wetland zones was similar to that calculated from the mass balance. Considering all hydrologic zones, NO3-N removal estimated from DNP was 5085 kg NO3-N. This estimate was slightly higher than the estimate of NO3-N removed via the mass balance .Despite the large amount of water lost as vertical seepage , overall NO3-N removal washigh in this restored wetland and comparable to that of other regions with temperate climates. Other studies of wetlands receiving agricultural runoff report NO3-N removal efficiencies ranging from0toashigh as99%.Comparisons of wet land-Ntreatment capability, however, is challenging in agricultural settings, because climate, flow characteristics , N species and N load vary across a wide range of temporal and spatial scales. Wetland characteristics also vary widely . The fact that there was no significant difference between NO3 concentrations at the 50- and 100-cm depths for a given wetland zone suggests that nearly all NO3 removal in this system occurred at depths above 50 cm.

Depth profiles suggest that nitrate removal is uniformly low at depth across all wetland zones . Trends in DNP for N-unlimited conditions were consistent with the nitrate losses observed in piezometer water samples.Denitrification potentials in this wetland were highly variable depending on amendment, depth and wetland environment. DNP measured in this study, ranged from non-detectable to over 15,000 mg NO3-N m 2 d 1 , which spans the range of DNP rates reported by several studies . Average DNP in the main flow path zone was higher than rates reported from wetlands receiving agricultural runoff in other regions, however, DNP in fingers and uplands was similar to that in other studies . Wetland soil properties that influence spatial patterns in denitrifying bacterial communities are pH, redox potential, temperature, soil texture, labile organic carbon, and nitrogen . With the exception of KCl-extractable N these properties were similar throughout the wetland in the upper 10 cm, so it is hard to assess the apparent differences in denitrifier activity based on these soil properties alone . Organic carbon, KCl-extractable N, and pore water nitrate were substantially lower at the 50- and 100-cm depths, so it is possible that denitrifier activity was limited at the lower depths by lack of substrate. The observed lower denitrification potentials at depth are consistent with other studies of constructed wetlands . Some studies in constructed wetlands have found DNP to be spatially uniform . In contrast, we found large differences in space,nursery pots with DNP being higher in the main flow path. Differences in DNP between hydrologic zones at the 10-cm depth may be explained by spatial variability in organic carbon content, differences in redox potential, sedimentation and organic matter quality. Highly variable inflow water fluxes resulted in fluctuating water depths across the wetland, with brief dry-down periods in the finger zones and long dry periods in the upland zones . Higher redox potentials in the upland and finger zones may have contributed to spatial differences in DNP . Many studies report that DNP is more strongly correlated with available carbon rather than total organic carbon . Only organic carbon was measured for this study, so it is possible that there may be substantial differences in carbon availability between the environments that may affect DNP. Also, DOC, which may serve as an important energy source for denitrifiers, was relatively constant across hydrologic zones and soil depths. Sediment deposition in the flow path zone was substantially higher than in the fingers or upland zones, which offers a possible explanation for the disparities in DNP despite similar soil conditions . Areas of active sediment deposition may receive organic matter of different quality compared to that of the native soil from which the wetland was constructed . It is also possible that the sediment, which originated from surrounding farmland, is a seed source of denitrifying bacteria. In fact, studies have shown that frequently tilled agricultural soils in the region have more facultative anaerobes and higher denitrification rates compared to untilled soils .

Since this wetland has only received tail waters for two seasons, it is plausible that we are witnessing the initial stages of recruitment of microbial populations and the associated evolution of wetland bio-geochemical processes. Thus, in older wetlands DNP may be expected to be more uniform. Other studies have shown that spatial variation in denitrification corresponds to patterns in nitrate concentration, increasing in areas of high N loading . Hernandez and Mitsch found higher denitrification potentials in constructed wetland soils where emergent macrophytes were present, when compared to unvegetated constructed wetland sediments. Since vegetation was sparse in both the finger and the flowpath zones, it is unlikely that the relative amount of vegetation had much effect on the observed denitrification potentials. A disproportionately high amount of the nitrogen was removed in the flow path zone compared to the fingers and uplands . This trend was a result of higher nitrate loading rates and significantly higher DNP rates in the flow path compared to other hydrologic zones. The higher mean N-amended DNP rates in the flow path suggest a larger denitrifier microbial population in this zone. The finger zone, although accounting for 40% of seepage, is responsible for the majority of NO3-N lost via deep seepage. This was the result of significantly lower DNP rates relative to the flow path zone and significantly higher pore water NO3-N concentrations at the 100-cm depth . As with any biological process, temperature strongly regulates denitrification rate . Lab incubations were performed at the mean field temperature , which was similar to the mean temperature of the flow path and 0.5 C higher than that of the fingers . Warm daytime temperatures are likely to substantially increase denitrification rate over diurnal timescales.Other NO3-N removal pathways may play an important role in this wetland. NH4 accumulation in pore water, and elevated KCl-extractable NH4 concentrations in the soil at 10 cm suggests that sulfur or ferrous iron-driven nitrate reduction may play a role in nitrogen cycling in this system . Redox potential frequently reached the sulfate reduction level  suggesting the presence of free sulfide. Anecdotal evidence such as H2S smell in groundwater samples, as well as visual identification of iron monosulfides in the sediment verifies the presence of sulfide in the system . At high concentrations, free sulfide is known to inhibit the final two reduction steps in the denitrification sequence, which may drive the reduction to ammonium rather than N2O and N2 . Sorption of ammonium from seepage water to cation exchange sites in the soil may also account for accumulation of ammonium in the upper 10 cm of sediment . Equilibrium with the sediment bound ammonium would result in elevated ammonium concentrations in the associated pore water. Despite the predominately unvegetated main flow path, plant uptake may play a substantial role in nitrogen cycling in this wetland. There may be diffusion of NO3-N from surface water into the upland areas via the shallow water table in the upland zone located approximately at the same elevation as the wetland water surface. The dense vegetation in the upland areas may assimilate a significant amount of N thereby increasing N removal rates.This study demonstrated that soils of recently restored wetlands have the capacity to remove large nitrate loads from vertically percolating water with low risk to groundwater in California’s Central Valley. Bio-geochemical processes in this wetland facilitated significant removal of nitrate inputs from agricultural tail waters. The active flow path of the wetland had the highest DNP at the 10-cm depth under all N amended conditions, and also experienced the greatest sediment deposition rates, nitrogen load and seepage volume . While the flow path had a significantly higher DNP relative to the other zones; the finger environments had a significantly higher DNP relative to the upland environments. These significant differences in DNP between zones may have resulted in the substantial differences in NO3 removal efficiencies, with 95, 81 and 70% reduction in NO3 seepage load in the flow path, finger and upland zones, respectively . Nevertheless, high NO3 removal efficiency in the flow path resulted in a high overall net decrease of NO3 load from seepage water for the entire wetland.

Stream N2O concentrations are often correlated with dissolved nitrogen concentrations ; however, variability in this relationship is often observed between sites . In this study, N2O concentrations were not correlated with microbial community composition, but rather, N2O production was likely elevated in streams indirectly due to high rates of denitrification in response to NO3 pollution. We demonstrate that head water stream microbial communities and ecosystem processes, such as microbial carbon and nitrogen transformations, respond to gradients in land use and stream conditions. Regional differences in stream microbial communities and the observed distance-decay relationships are further evidence that stream communities are seeded from the surrounding landscape. Across geographic regions, microbial community composition varied in streams with high urban, agricultural, and forested land use, and changes in microbial diversity and land use correlated with stream community respiration, linking changes in biodiversity to changes in ecosystem function. Our results suggest that certain microbial groups respond to land use similarly across ecosystems, making them potential candidate taxa to be used in the development of a microbial index of stream conditions.There is much debate about the potential effects of phased reductions in governmental intervention in U. S. agriculture. Unfortunately, growing blueberries in pots there is little evidence that this debate has taken into account the linkages of the agricultural sector with the balance of the U. S. and international economies.

The purpose of the analysis presented in this paper is to give a structural interpretation to the macroeconomic linkages-both forward and backward between the agricultural sector and the aggregate economy; to review and criticize the structural exploration of macroeconomic time series concerning the agricultural sector and the aggregate economy, and to draw out the implications of alternative macroeconomic shocks on the phased reduction of governmental intervention in agriculture. The substantial variation in exchange rates, inflation rates, relative farm prices, and agricultural incomes since the early 1970s has induced a new stream of research on the relationships between macroeconomic policy and the agricultural sector [. In all of these studies, the exchange rate has been recognized as an important determinant of real farm prices through its effects on the trade balance . A series of theoretical and empirical studies on the effect of exchange rates has shown, for instance, the importance of an overvalued currency on U. S. agriculture production and exports . Studies on relative prices and aggregate inflation have supported the hypothesis that the variability in real farm income and prices increases with the general price level variability . At the core of this research is the idea that, if an unanticipated exogenous shock occurs, all the price and interest rate adjustments will happen in some sectors earlier than in others. Assuming prices adjust more quickly in competitive markets than in imperfectly competitive markets, farm prices can be expected to rise faster than non-farm prices, provided of course that agricultural markets are indeed more competitive. Various explanations for these relative price movements have included differences in the supply and demand elasticities of specific products and, more recently, the effects of contract length on the speed of adjustment .

According to Bordo, a change in money supply causes a faster response for farm commodity prices than industrial prices and a faster response for non-durable than durable prices. The existence of nominal influences on real variables in agricultural markets has been tested in a numerous studies . In a more general setting, Fischer has studied three sets of hypotheses linking aggregate price changes to relative price variability: the adjustment cost hypothesis, the rational expectation unanticipated disturbance hypothesis, and the asymmetric price response hypothesis. The first two hypotheses imply that relative price variability is affected by macroeconomic disturbances; the third hypothesis implies that autonomous relative disturbances have macroeconomic effects. Under the first two hypotheses, both price level changes and relative price variability are caused by the same aggregate supply and demand interactions. The third hypothesis is based on the assumption that prices respond asymmetrically to disturbance, for instance, they may be downward inflexible. Under this hypothesis, as Fischer notes , “If the disturbances that move relative prices were primarily supply side, resources should be moving out of the industries where prices have risen towards the industries where prices have yet to fall. If the disturbance were demand side, resources should be moving towards the higher prices sectors.” Hence, differential responses in prices in this case are due to more than price stickiness alone. In Fischer’s empirical work, the available evidence is not totally supportive of the first two hypotheses and the third hypothesis could not be rejected. A number of other studies address the broader macroeconomic scenario. In some cases, this broader perspective includes an examination of the linkages with agricultural commodity prices .

Stemming from Dornbusch’s overshooting models of exchange rate determination, these studies attempt to capture the linkages among exchange rates, money, interest rates, and commodity prices. This work begins with the fixed/flex price specification , modelling the farm sector as a set of auction markets while the non-farm sector is characterized by gradual adjustment of prices. In this framework, agricultural market dynamics is studied, taking into account not only the real demand and supply forces directly related to the farm sector but also the effects of monetary and fiscal policies. The results show that monetary and fiscal policies can have substantial effects on prices and income in the agricultural sector over the short run, whereas sector-specific policies appear to have more significant influences in the long run. Regardless, both sets of policies can have dramatic effects on the dynamic path of the agricultural sector. Unfortunately, the “state of the art” in examining macroeconomic linkages and the role of monetary, fiscal, and commodity-specific policies on the performance of the U. S. agricultural sector is still unsatisfactory. This is, in large part, because not all linkages have been either conceptually or empirically investigated. In particular, the fix/flex specification neglects the structure of commodity-specific policies which limit the downward movement in many agricultural prices. Moreover, the major emphasis in this work has been on what can be referred to as the forward linkages, i.e., those effects that run from the aggregate economy to the agricultural sector. The backward linkages have been almost completely neglected. As noted above, one of the purposes of our analysis is to identify and analyze the backward linkages in conjunction with the forward linkages. Although Gardner might have been correct when he stated, “A fully specified model is not necessary to identify macroeconomic effects upon agriculture; because agriculture is a small part of the general economy ,” there are many other reasons why agriculture could have significant feedback effects on the monetary side of the economy. In particular, a sufficiently large subsidization program for some commodities can have a significant effect on governmental budgets and, thus, fiscal policy. A priori, the fiscal policy effect can in turn influence monetary policy, especially if the monetary authorities’ reaction function is not completely exogenous. With the above motivation as background,drainage gutter we first turn to a theoretical framework that formally incorporates the major features of agricultural policy in the dynamics of commodity, exchange rate, interest rate, money, and manufacturing good markets. This provides the basis for the specification of a vector error correction model with exogenous variables which is empirically estimated in section 3. Based on tests of specific hypotheses regarding identifying restriction as well as forward and backward linkage relationships, a policy simulation model is constructed. This policy simulation model is used to investigate different rates of reduction in governmental subsidization of commodity markets in the face of alternative macroeconomic shocks. From these policy simulation results, a number of concluding remarks and insights are offered in section 6.

The theoretical structural model developed here is a two-sector model in which a number of interactions between the money and foreign exchange markets and the goods market are potentially present. These interactions are both direct and indirect and operate through several different channels. In the analysis, the entire set of interactions are admitted-both direct and indirect and among money, exchange rate, and prices-in a full comprehensive model incorporating all the relevant exogenous variables. The major theoretical features of the model can be’summarized as follows. Manufacturing output is demand determined, while farm output is partly demand detennined and pardy supply detennined where the supply conditions depend on the degree of intervention of the government in agriculture. Prices adjust slowly to changes in money. A balance-of-payment equation detennines the rate of accumulation of reserves as a fraction of the total money stock. Since capital mobility is imperfect, either the capital account or the current account balances can be nonzero in the short run. The monetary authority intervenes on the foreign exchange market in order to keep the rate of depreciation of the exchange rate in line with the domestic trend of monetary growth. Total money supply growth is given by the rate of credit creation and the rate of accumulation of reserves . Price inflation in the two sectors depends on excess demand pressures and on the money growth rate. In the long run, price inflation is equal in the two sectors and is equal to the rate of monetary growth. This is equal to the target rate of credit creation, as well as to the rate of exchange depreciation. Price inflation and output growth in the two sectors, money growth, and the exchange depreciation rate are the endogenous variables. The money stock, the price levels in the two sectors, and the exchange rate level, as well as interest rates, foreign prices , total farm stocks, and government expenditure in agriculture, are exogenously given. Changes in the exchange rate have a direct effect on prices since they imply changes in relative prices. They also have indirect effects, through the foreign exchange intervention rule, since the latter implies a change in domestic supply; a consequent change in income; and, thus, a pressure on prices. Changes in money also have an effect on prices , since they induce changes in domestic demand. Thus, money is non-neutral in the short run. Changes in money supply have an indirect effect also through the change in interest rates, the change in the capital account balance, the consequent pressures on the exchange rate, and therefore on relative prices. Finally, changes in money also have depreciating effects on the exchange rate through the non sterilized foreign exchange intervention.An exogenous supply shock to the entire economy which has stagflation effects, induces changes in the terms of trade and results in changes in the trade balance; in domestic output; and, hence, in money demand. An accommodating monetary policy and a “leaning against the wind” foreign exchange policy will let the changes in prices be fully reflected in changes in money and exchange rates. Sectoral changes in prices, due to autonomous supply shifts, also have effects on money and exchange rates through the trade balance and domestic demand. Within the two-sector model, we incorporate the effects of government farm support programs on the dynamics of agricultural prices in response to changes in monetary and exchange rate policy. The effect of the target price is such that, if the government fully “protects” agriculture, then all downward changes in relative prices are paid back to domestic producers. Thus, changes in market prices are dampened; and the supply reduction measure helps producers adjust to exogenous falls in demand and to alleviate excessive stock accumulation. Reducing excess supply thus has dampening effects on inflation variability. In the limit, if the agricultural output is kept at the market-clearing level, price inflation in the farm sector is equal to general trend inflation. The two policy variables can be proxied by two variables whose actual effect turns out to be even more composite-total farm stocks and government expenditure in agriculture. With no intervention policy in agriculture, following an exogenous reduction in the foreign price of agricultural products we would have a shift of internal demand from domestic to foreign goods, a trade balance deficit, and thus depreciating pressure on the exchange rate. The monetary authority would then intervene on the foreign exchange market by contracting the supply of domestic money in the world market according to the intervention rule.

It is possible that PFAS effects YAP/TAZ localization via cytoskeleton integrity. These connections between adipose tissue maturation and cytoskeletal remodeling are a potential avenue for PFAS perturbation and how it effects lipid profiles and fat development. In obesity, adipocytes are hypertrophic and the expression of the adipokine leptin increases and inflammatory cytokines are increased while adiponectin and lipoprotein lipase are decreased. There are also increases in angiogenesis, immune cell infiltration, and adipose inflammation. These changes are characteristics of insulin resistance, hyperglycemia, dyslipidemia, hypertension, and obesity/adiposity and could be common ground for PFAS associations with obesity in humans. Based on these observations, we hypothesize that PFAS may be mechanistically perturbing the cell cytoskeleton and working through the Hippo pathway resulting in abnormal developmental outcomes in children. In the current study, we have evaluated PFAS’ effects on skin epithelial and adipose derived stem cell lines. We performed in vitro experiments to determine if the cytoskeleton is modulated by PFAS in two types of cells and investigated dysregulation of f-actin and acetylated tubulin. Functional effects on cell survival of both cell types and differentiation of adipose was evaluated in response to PFAS exposure. To investigate if the Hippo signaling effector, YAP, is modulated by PFAS, we quantified YAP expression and localization. Further, we have shown that damaged phenotypes due to PFAS effect the wound healing processes of keratinocyte skin cells and adipose derived mesenchymal stem cells and that some doses of PFAS chemicals induce higher amounts of adipogenesis as determined by lipid droplet staining and qPCR. PFAS effect on the differentiation process of adipose derived mesenchymal stem cells into adipogenic phenotype was also investigated.

Adipogenic differentiation was induced via media,greenhouse ABS snap clamp as completed previously. Adipogenic induction media was DMEM supplemented with 10% FBS and 1% P/S, 500 µM 3-isobutyl-1-methylxanthine , 1 µM Dexamethasone , 10 µg/mL Insulin , and 10 µg/mL indomethacin . To examine how PFAS effected these processes, ASC52telo cells were plated at a density of 25,000 cells/coverslip in 24 well plates on 12 mm glass slides and cultured in adipogenic conditions. After initial seeding in routine culture media, at 48 hours PFOA [100 and 125 µM ] and PFOS [20, 30, 40 µM] were added to well plates. Control media was Adipogenic Induction media. Cultures were carried out for 19 days, at endpoint, all wells were fixed with 4% PFA for 15 minutes then washed x 3 with PBS . Plates were either stored at 4 °C or were immediately exposed to oil-red-o staining for adipogenesis assessment. To assess adipogenesis, lipid content was assayed using Oil Red O staining which marks lipids secreted by adipocytes. ORO staining was completed similar to previous studies. Briefly, a 0.5% lab stock was made up by dissolving 0.2 g Oil Red O in 40 mL Isopropanol . After dissolving overnight, a working stock was made up by diluting the lab stock 2:3 with culture grade water to yield a 0.2% solution in 40% Isopropanol. The 0.2% solution was made up immediately before exposure then filtered before use with a 0.2 µm sterile syringe filter. Each 24 well was filled with 0.5 mL ORO and incubated for 30 minutes at room temperature. After exposure, coverslips were washed 5x with autoclaved distilled water. Phase Contrast imaging at 10x was performed to evaluate adipogenesis and oil-red-o accumulation. For oil-red-o analysis, 3 images were taken per coverslip for each replicate set. For RNA isolations, ASC52telo cells were plated at a density of 500,000 cells/60 mm tissue culture plate then grown up for 48 hours in their routine culture media. At 48 hours, adipogenesis was induced via media and cells were cultured in adipogenic conditions for 19 days with experimental chemical doses. At day 19, mRNA was isolated using the Thermo GeneJet RNA Purification Kit .

All RNA isolations were carried out as outlined by the manufacturer. Assays were completed to assess for adiponectin, leptin, PPARγ, CEBP, and CTGF, using the housekeeping gene GAPdh. Primer sequences given in supplementary data Table 5.1 Primer Sequences used for qPCR. . Quantitative polymerase chain reaction was performed via SensiFAST™ SYBR No-ROX One-Step mastermix from Bioline. All reactions were performed in triplicate. qPCR reactions were completed using a Mic Real Time PCR Cycler at 10 minutes at 45 °C then 2 minutes at 95 °C then 40 3-step cycles of 95 °C for 5 seconds, 60 °C for 20 seconds, and 72 °C for 10 seconds and a melt from 72 °C to 95 °C at 0.3 °C/s. For quantification of mRNA, n = 4. Following culture, coverslips were fixed and permeabilized in place for 20 minutes via 4% paraformaldehyde and 0.25% triton x 100. After fixation, coverslips were washed with PBS x 3 and either stored at 4 °C in PBS or blocked and stained immediately. Samples were first blocked for one hour then stain solution of primary antibodies was added . All stain solutions were made up in blocking buffer except DAPI which was made up in 1 x PBS. Primary antibodies and chemical stains used include: YAP-1, Acetylated Tubulin, Ki67, Phalloidin, DAPI ; antibody specifications given in supplemental data Table 5.2. Coverslips were exposed overnight at 4 °C to primary stain solution then removed, washed x3 with 1x PBS, then exposed overnight to the secondary solution . DAPI was used to mark nuclei and coverslips were exposed for 20-30 minutes at room temperature in 1x PBS, after initial staining was complete. All coverslips were mounted to glass slides using gelvitol allowed to dry, then cleaned with 70% ethanol prior to imaging. Confocal imaging was performed using a Leica TCS SPEII confocal, sCMOS camera attachment. Imaging parameters remained the same for each coverslip in order to compare intensities; each coverslip was imaged using a 20-25 position tilescan and a 1 micron voxel size. Confocal volumes were assessed via custom algorithms designed in MATLAB . Briefly, maximum projections of each tile-position per sample was filtered and segmented which enabled antibody intensity quantification and cell colony health evaluations.

YAP intensity at nuclei and cytosol was quantified in N/TERT-1 and ASC52telo and the number of nuclei per sample was also quantified as an indication of cellcolony health after PFAS exposure. For ASC52telo cells, Ki67 was quantified at nuclei as an indication of proliferation. To evaluate dysregulation of the cytoskeleton of N/TERT-1 cells, expression of phalloidin and acetylated tubulin were quantified using concentric annular rings. Cells were identified using the phalloidin stain then two regions were indicated. A peri-nuclear region and a peripheral nuclear region was identified for each cell and the intensities of phalloidin and acetylated tubulin were quantified within the segments. For all analysis, each experimental condition quantification was based on at least 20 positions per coverslip, intensities were averaged per position per coverslip. For all analysis of confocal images, n = 3 for N/TERT-1 cells for each timepoint and n = 4 for all ASC52telo cells for each time point. For quantification of adipogenesis,snap clamps ABS pvc pipe clip custom MATLAB algorithms were written to assess pixel area of ORO present in each control and dosed coverslips. Three phase contrast images were taken per well; cell coverage and ORO content was determined via image segmentation and averaged for each sample then ORO content was normalized to both the cell coverage of the sample and to the control of each experiment group . PFAS chemicals have stable and bio-accumulative properties which makes them particularly dangerous to biological membrane structures and to the environment in general. Previous work has shown that higher maternal serum concentration of PFAS are associated with decreased birthweight but increased adiposity in infants and in pediatric/young adults, but the mechanism of these changes and toxicity of PFAS chemicals are still largely unknown. Work in animal models has shown that PFAS chemicals have toxic effects and that in some cases these follow nonmonotonic responses. Generally, there is a discrepancy in research doses of PFAS and environmental exposure and detection of PFAS. The U.S Environmental Protection Agency set federal drinking water guideline limits for PFAS at 70 ng/L but, as of 2019 only seven states developed guidelines varying from 13-1000 ng/L. Several states do not have any guidelines at all or only have guidelines for one of many PFAS chemicals. Although the PFAS doses administered in this work are higher than the limitations set , the bio-accumulative properties of PFAS are an important consideration. Guidelines set by the EPA cannot account for bioaccumulation and only apply to drinking water even though humans are exposed to PFAS through many avenues including high amounts from contaminated aquatic species. Thus, there is a mismatch between what guidelines say are safe to consume and what humans are actually consuming or being exposed to. Further, bio-accumulative properties of PFAS chemicals are difficult to model in vitro and hard to discern in vivo because of environmental and body variability.

In the experiments completed here, samples were given the same doses for each time point and were only dosed a single time. For example, the 72 h time point experiments did not get exposed to more PFAS toxicant than the 24 hr time point, but the cells were exposed longer. For the adipogenesis assays, cells were exposed to PFAS at every media feeding, and therefore may have modeled bio-accumulation in a different way than the N/TERT-1s and undifferentiated ASC52telos. To help understand underlying mechanisms of PFAS toxicity in human cells, we studied PFAS effects on cell monolayers. The data presented here show that PFAS effects cell and colony health, as determined by nuclear counts . Interestingly, ASC52telo cell monolayers that were exposed to PFAS remained stable 48 h after exposure and there was not a significant difference in cell number. To understand if PFAS had detrimental effects on proliferation of ASC52telos, we quantified the proliferative marker, Ki67 but concluded that these doses of PFOS and PFOA do not have significant effects on proliferative capacity of ASCs either. However, in agreement with past literature that investigated PFAS effects in the African clawed frog, we show that PFOS and PFOA treatments induce significant declines in cell number of N/TERT-1 cells, and that these declines are greater at longer time points . Additionally, we similarly show that higher PFOS doses produce the greatest cell decreases but our results from PFOA exposure do not follow nonmonotonic relationships as previously shown in the African clawed frog cell monolayers. Importantly, the high dose of PFOS used here is similar to the frog study where the high PFOA and PFOS dose was 10 µM. However, the low dose used for both chemicals from the frog study is not similar to our PFOA doses . More investigation is required to understand if low doses of PFOA produce nonmonotonic effects in human cells. PFAS chemicals have been found to disrupt f-actin, microtubules, and gap junctions of the cell cytoskeleton. We have demonstrated that PFOA and PFOS disrupt the cytoskeletal components, acetylated tubulin and f-actin, in two human cell lines. Increased intensities and shifts in expression of acetylated tubulin and f-actin support cytoskeletal disruption by PFAS that has been reported in other studies. As seen through f-actin fibers , there were also differences in N/TERT-1 cell edges with increased presence of filipodia and prominent protrusions. It could be argued that these cytoskeletal changes are largely due to cell death and colony disruption due to PFAS toxicity, but we have demonstrated that there are cytoskeletal disruptions in ASC52telo cell lines as well. ASC cell lines were resistant to the cytotoxic effects of PFAS exposure and the number of cells and their proliferative capacities did not change after 48 h of exposure. Additionally, the cell death at 24 h seen with the high dose of PFOS did not correspond with radial distribution changes of cytoskeletal components. It is likely that cell death does play a part in the cytoskeletal disruption since colonies themselves are disrupted, but it does not seem to be the only mechanism here. PFAS likely perturbs the cytoskeleton independently of cell death, but this mechanism of action still requires more investigation.Disruption has been demonstrated through actin filament remodeling, central actin stress fiber formation, microtubule and gap junction disorganization, and formation of lamellipodia and filipodia structures at cell periphery. PFOS has been explicitly linked to disruption of blood testi barriers established by Sertoli cells in human and animal studies and thus, accumulation of testicular PFOS.

While in vivo and traditional cell culture models remain important tools, there is increasing interest in more physiologically relevant culture models, and there is a growth in recent studies employing organotypic skin models . Organotypic Skin Models Researchers have used organotypic models to study skin biology since the 1980s. OSCs are also commonly referred to as human skin equivalents or full-thickness skin models; they typically have dermal and epidermal layers with proper stratification of the epidermis. These models have proven useful for studying skin development, evaluating cytotoxicity, studying wound healing, and more recently as disease and aging models. OSCsare highly customizable and allow for control of organotypic cell populations, genotypes, and culture conditions to enable carefully controlled studies on tissue-level biology. OSCs have the capacity to be used for in depth aging studies without the dangers of human trials or expensive animal models; with long-term culture stability for chronic studies. Most commonly, OSCs contain dermal fibroblasts and keratinocytes and are cultured at an air-liquid interface for epidermal differentiation and stratification. However, with the growth of interest in heterogeneous cell-cell communication, an increasing number of models have been demonstrated with additional cell populations. These include vascular endothelial cells, immune cells, adipose derived stem cells and adipocytes from adipose derived stem cells, embryonic stem cells, melanocytes and melanocytes derived from induced pluripotent stem cells. With this customizability and a growing number of accessible protocols, OSCs represent a useful tool for studying skin aging; exemplar applications are discussed below,drainage planter pot first for disease generally and then with aging specifically.

OSCs have been used in a number of disease studies, both directly and as “hybrid” studies where a humanized OSC is grafted onto immunodeficient mice. Additionally, models have been shown useful for testing potential therapeutic techniques for debilitating skin disorders or injuries. OSC skin disorder models include: psoriasis, recessive dystophic epidermolysis bullosa , xeroderma pigmentosum, vitiglio, Forlin syndrome, lamellar ichthyosis, Netherton syndrome, congenital pachyonychia, Junctional epidermolysis bullosa, and fibrosis. Of these disease models, the fibrosis model by Varkey et al. is especially interesting for its potential to be adapted to use as an aging model. In this study, OSCs were generated using either deep dermal fibroblasts or superficial dermal fibroblasts in combination with normal human keratinocytes. They found that the antifibrotic properties of deep dermal fibroblasts and the fibrotic properties of superficial fibroblasts can influence OSC characteristics. Authors found that when compared to constructs with superficial or mixed fibroblast populations, OSCs with deep fibroblasts had higher levels of interleukin-6, reduced TGF-β1 production, higher PDGF expression, and epidermal formation was less defined and less continuous. This model is potentially interesting as a platform for aging research, as TGF-β is implicated in skin aging through regulation of matrix metalloprotease activity. The work of Varkey et al. highlights the usefulness of OSCs to study signaling between specific cellular subpopulations in a controlled way; an approach that could be readily adapted to aging studies. While there is a great deal of room for OSCs to be used to study the processes of aging in isolation or in combination with disease, several researchers have applied OSCs to aging. Organotypic Skin Models to study aging As OSCs are stable for long culture periods , using the extended culture time to study intrinsic aging is perhaps one of the most straightforward techniques and can be combined with other aging models and/or cell types 20.

With this model, authors demonstrated that extended culture exhibited several age-related aspects similar to those that occur with in vivo aging, including decreases in epidermal thickness, decreases in hyaluronin expression, increases of the aging biomarker p16Ink4a, decreases in keratinocyte proliferation over time, loss of expression of healthy epidermal markers, and basement membrane alterations. Another straightforward application of OSCs in aging is studying the impact of senescent cells. A number of studies have incorporated senescent fibroblasts into OSCs to generate models that recapitulate many of the features of in vivo aged skin. Diekmann and colleagues induced senescence in human dermal fibroblasts and keratinocytes using Mitomycin-C treatment and incorporated the cells into OSCs 84. When compared to mitotic OSCs, the senescent models demonstrated changes similar to aged in vivo skin, including a more compact stratum corneum of the epidermis, reduced dermal fibroblast population, decreased collagen type I and III fiber content, decreased elastin expression and looser elastin structures, increases in MMP1, and disordered epidermal differentiation. Authors also isolated fibroblasts after OSC cultures to re-validate their senescence through aging markers and showed senescent morphology, increased senescence associated β-galactosidase , lower proliferative activity determined by Ki67 expression, upregulated p53 activity, upregulated ROS, and increased concentrations of MMP1 as compared to mitotic fibroblasts. A similar study involving senescent fibroblasts used healthy fibroblasts that were exposed to H2O2 to induce senescence and then cultured the senescent fibroblasts in skin equivalents with healthy keratinocytes. Aging phenotypes were again characterized by changes in proliferation, differentiation of suprabasal epidermal layers, impairments of skin barrier function, and surface property modification. Further, authors found that fibroblasts exhibited senescence-associated secretory phenotype markers including IL-6, GmCSF, and IL-1α, however, this response was blunted in the 3D culture with keratinocytes.

Lower levels of IL-6 were also measured in OSCs generated with fibroblast that underwent doxorubicin induced senescence. Interestingly, Weinmueller et al. observed more Ki67 positive epidermal cells when senescent fibroblasts were present. More research is required to understand senescence in the dermis and how it may effect keratinocyte homeostasis. Serial passaging of fibroblasts has also been employed to simulate aging in OSCs, showing that constructs generated with late passage fibroblasts were similar to in vivo aged skin. OSCs were generated with 15-20% SA-β-gal positive fibroblasts cells in 2D culture prior to 3D seeding. Authors observed few changes in the epidermal compartment while the dermal component of OSCs presented a thinner dermis and increased MMP1, similar to in vivo aged skin. Defects in epidermal-dermal junction in these OSCs were not observed and keratinocytes exhibited a healthy phenotype. Although not shown, authors noted that when greater than 30% Beta-gal positive fibroblast cells in 2D were used to generate OSCs, the fibroblasts did not produce ECM and constructs were not viable likely due to ineffective support for keratinocytes. As Janson et al. found, generating an OSC using senescent cells is technically challenging since the percentage of senescent cells used to generate an OSC can alter skin structure and long-term culture health . Similar studies focused on the aging of the keratinocyte population have also been done. In OSCs generated from primary cells isolated from donors,plant pot with drainage cell donor age is an option for simulating intrinsic aging in vitro . OSCs generated with either keratinocytes isolated from aged individuals or serially passaged keratinocyte cells have been used to examine the effects of replicative senescence. Constructs generated with older keratinocytes exhibited thinner epidermis compared to cells from 1-year old donors. Additionally, there were differences in epidermal organization, where constructs generated with young keratinocytes were well organized with better stratification, while older cells produced more disorganized and less complete stratification. This study also investigated amounts of epidermal stem cell markers. They found that when keratinocytes were pass aged over six times , there was a loss of stemness, indicated by high expression of α6 integrin and low expression of CD71. Likewise, in constructs generated with young keratinocytes, α6 integrin expression was observed in basal cells of epidermis while in constructs generated with adult and elderly cells there was faint andabsent α6 integrin expression . These OSC findings demonstrated in both intrinsic aging and in vitro senescence induced by serial passaging results in depletion of stem cells in the epidermis of skin 86 . Epidermal changes associated with aging have also been shown in models generated through genetically altering expression of key components, for example p16Ink4a 87 . In vivo chronological human aging markers, p16Ink4a and its repressor BM1, are established markers of in vitro aging tissue. p16Ink4a is an inhibitor of cyclin-dependent kinases that blocks the progression from G1 phase to S phase of the cell cycle and promotes senescence onset. In vitro aged skin models can be generated from young donor keratinocytes cells by p16Ink4a overexpression. Conversely, aging phenotypes observed in old donor keratinocytes can be rescued through silencing p16Ink4a.

Aged models resulted in thinner epidermis, loss of stratum corneum , and atrophy. OSCs also allow for studies of matrix and cell-matrix interactions in aging skin. Expression patterns of glycosaminoglycans and proteoglycans are important in skin tissue mechanical integrity, and aging-related changes contribute to frailty in both intrinsically and extrinsically aged skin. Glycation and the presence of advanced glycation end products increase in aging skin, and this has been leveraged in OSCs to create an aged skin model. In this model, collagen was glycated in vitro prior to construction of the OSC. This simulated intrinsic aging of the construct, resulting in modified integrin patterns in the suprabasal epidermal layers, activation of the dermal fibroblasts to increase the production of metalloproteinase, type III procollagen, and type IV collagen 14,32. Authors found that these morphological and molecular changes in the epidermis and dermis could be partially rescued by antiglycation agents such asaminoguandine. More investigation is necessary to understand exactly how GAGs and PGs are affected during skin aging. Open questions include how sex specific hormones may affect concentrations 8 and what downstream effects GAGs and PGs have on the expression of cytokines and growth factors. Building off of the previous OSCs, multi-cellular skin models can help to elucidate aging mechanisms regarding GAGs and PGs and their effect on skin homeostasis. CXyloside is a xyloside derivative that has been investigated as therapeutic to improve dermal-epidermal junction morphology in aging skin. Sok et al. exposed OSCs to CXyloside and investigated the resulting DEJ morphology. C-Xyloside exposure resulted in higher basement membrane protein concentrations, specifically collagen IV, laminin, and collagen VII, and a structure more similar to the microanatomy of healthy human skin. Further, C-Xyloside increased concentrations of dermal proteins such as pro-collagen I and fibrillin, which are key ECM proteins for the maintenance of skin elasticity. Since defects in the basement membrane, DEJ, or elasticity contribute to skin fragility in aging, this model has potential as a test bed for other aging therapeutics. This body of work builds on the framework that previous organotypic skin models have developed and importantly demonstrates further customization through incorporation of different cell types and photoaging studies. We have generated protocols for establishing fully vascularized human skin equivalents alone, and additionally to establish adipose and vascularized human skin equivalents. These OSCs have been analyzed volumetrically and thus, protocols for volumetric imaging of this in vitro skin tissue were developed for optical coherence tomography and confocal microscopy. Although it is an improvement upon the classic histological analysis that OSCs traditionally undergo,volumetric imaging introduces new challenges of analysis, which we have addressed through automated image analysis based on custom algorithms. These end-to-end processes are novel contributions to the tissue engineering field and they importantly enable aging studies because of the skin’s stability over time. Through the generation and analysis of in vitro skin models, multiple image analysis techniques were developed for three-dimensional structures. Specifically, through these algorithms, we were also able to analyze cell monolayers which is demonstrated in chapter 4. PFAS chemicals, or perfluooalkyl substances are very abundant and stable molecules that tend to accumulate in biological systems, or bio-accumulate . These chemicals are especially dangerous in fetal development and have been linked to decreased birthweight but increases in adiposity, and altered lipid profiles in youth and young adults. Through the skills learned in adipose tissue development and automated image analysis, we were able to study the effects that PFAS has on epidermal cell monolayers, adipose derived stem cell monolayers, and the differentiation process of adipose derived stem cells to mature fat cells, adipocytes. This work presents a novel contribution in understanding PFAS mechanistic actions on human cells and how specifically PFAS acts on adipogenesis. Additionally, we have elucidated action of PFAS chemicals on human cells through cytoskeletal disruption.Human skin performs many essential biological functions including acting as an immune/mechanical barrier, regulating body temperature, participating in water retention and sensory roles.

Our study reveals the induction of channels allowing for the nuclear egress of the progeny viruses across the host chromatin. Moreover, this work used a new combination of methods in the study of virus-cell interactions.Language production appears to be a largely incremental process: speakers plan an utterance as they are producing it, simultaneously integrating multiple sources of information . One apparent effect of this incrementality is availability effects in language production: the fact that speakers will often choose to produce words which are easily accessible or available to them earlier in an utterance, or to include such words when they are optional, or even to use a highly-available word in place of a more communicatively accurate but less available word . The fact that available words tend to go earlier has been attributed to a greedy, ‘easy-first’ language production strategy . Here I present an account of availability effects within a computational-level model of language production based on a recently developing theory of the complexity of action selection from the fields of computational neuroscience and information theory. This theory, the rate–distortion theory of control , holds that actions are selected to maximize value subject to constraints on the use of information. The theory originates in the economics literature where it operationalizes bounded rationality , and it has been developed and applied in the literature on physics, robotics, optimal control,25 liter pot computational neuroscience, reinforcement learning, cognitive psychology, and linguistics .

RDC uses the mathematical theory of lossy compression to impose informational constraints on the perception–action loop. It has also been termed rational inattention and policy compression. I develop a proof-of-concept model of language production within the RDC framework, based on an informational constraint identifiable as a channel capacity limit on cognitive control . I show that this model provides an account of availability effects in language production, and I validate this account by examining experimental data from two previous sets of experiments: Levy & Jaeger on relative clause complementizers in English, and Zhan & Levy on noun classifier choice in Mandarin Chinese. In contrast with existing models of language production which are primarily situated at Marr’s algorithmic level of analysis or at more concrete levels, the RDC model is at the computational level: it directly describes the inputs, outputs, and goals of the language production system, without committing to an algorithmic implementation. The high level of abstraction means that it is possible to see how simple underlying computational constraints give rise to a variety of different behaviors. Hard disks consume a significant amount of power. In general purpose computing, hard disks can be responsible for as much as 30% of a system’s power consumption. This percentage will only increase as current CPU trends lean toward increasing the number of cores versus the single core clock rate, hard disks use faster rotational speeds, and multiple hard disks per system become more prevalent. In large storage systems, hard disks can dominate system power consumption: 86% and 71% of the total power consumption in EMC and Dell storage servers, respectively.

As a result, there are several motivations to decrease the power consumed by hard disks, from increasing battery lifetime in mobile systems to reducing financial costs associated with powering and cooling large storage systems. To reduce hard disk power consumption, spin-down algorithms are used, which put a disk in a low-power mode while it is idle. In a low-power mode, such as standby, the platter is not spinning and the heads are parked, reducing power consumption. Researchers have proposed several spin-down algorithms, which are very efficient at reducing hard disk power consumption. These algorithms are typically time-out driven, spinning down the disk if the time-out expires before a request occurs. Adaptive spin down algorithms vary the time-out value relative to request inter-arrival times. They are very effective and approach the performance of an optimal off-line algorithm which knows the inter-arrival time of disk requests a-priori. Although spin-down algorithms are effective at reducing hard disk power consumption, pathological workloads can completely negate a spin-down algorithm’s power saving benefit, prematurely causing a disk to exceed its duty cycle rating, and significantly increasing aggregate spin up latency. Such pathological workloads, which periodically write to disk, are not uncommon. Both Windows and UNIX systems exhibit such behavior. For example, Figure 1 shows the periodic disk request pattern of an idle Windows XP system. In UNIX systems, applications such as task schedulers , mail clients, and CUPS periodically write to disk. Upcoming hybrid disks will place a small amount of flash memory logically next to the rotating media, as shown in Figure 2. The first hybrid disks will either have 128MB or 256MB of NVCache in a 2.5 in form factor 1.

A host can exploit the NVCache to achieve faster random access and boot time because it has constant access time throughout its block address space as shown in Figure 3, while rotating media suffers from rotational and seek latency. Access time for this particular device is roughly equal to c+bs÷bs off, where c is a 2.2ms constant overhead, bs is the desired blocksize, and bs off is 4KB. In addition to the potential performance increase, hybrid disks can potentially yield longer spin-down durations— the NVCache can service I/O while the disk platter andarm are at rest, such as the write requests from Figure 1. Note that because flash memory is non-volatile, NVCachestored data is persistent across power loss. To exploit the underlying media characteristics of hybrid hard disks for improved power management, we present four enhancements to increase power savings, reliability, and reduce observed spin-up latency: Artificial Idle Periods that extend idle periods relative to observed I/O type; a Read-Miss Cache that stores NVCache read-miss content in the NVCache itself; Anticipatory Spin-Up that spins the rotating media up in anticipation of an I/O operation not serviceable by the NVCache; and, NVCache WriteThrottling that limits the reliability impact imposed on the NVCache because of I/O redirection.We now present an overview of a hybrid disk and how its NVCache can be managed by a host operating system using a modified set of ATA commands,25 liter plant pot according to the T13 specification for hybrid disks. The four enhancements are presented in Section 3. Sectors stored in the NVCache are either pinned or unpinned, which when referred to as a collection are known as the pinned and unpinned set, respectively. The host manages the pinned set, while the disk manages the unpinned set. Hybrid disks will also have a new power mode, NV Cache Power Mode, which can be set and unset by the host. In this mode, I/O is directed to the NVCache unpinned set while the disk “aggressively” tries to keep the rotating media spun-down. Defining and implementing “aggressive” is left to the drive vendor’s discretion. Although the hybrid disk controls the spin-down policy, the host controls the minimum time rotating media must remain spinning after a spin-up, providing the host with some control over the underlying spin-down algorithm. The host controls I/O to the NVCache pinned set. Sectors can be pinned in the NVCache, and pinned sectors can be removed or queried.

The pinned attribute feature is intended to increase random access performance, although it can also facilitate better power management. The host can flush a specific amount of unpinned content to rotating media to make room for more pinned sectors. However, pinned sectors cannot be evicted to create unpinned space. Addressing multiple sectors at a time is possible using an extents-based mechanism called LBARange Entries. A host can also specify the source when adding pinned sectors to the NVCache: host or rotating media, by setting a Populate Immediate bit. This capability gives the host control over NVCache functionality: better random access or spin-down performance. A host has additional control over a hybrid disk. It can query the disk for spin-up time, read/write NVCache throughput, and the maximum pinnable sectors.We now discuss the mechanism in which a host can leverage a hybrid disk to provide power management functionality. The host controls rotating media state with traditional power management commands, and NVCache commands to manage the pinned set. Fine-grain spin-down algorithms can be implemented because the host is informed when rotating media power state changes occur. While the rotating media is spun-down, the host should use the NVCache store, query, and read commands to redirect I/O to the NVCache. If the NVCache does not have the requested read data, or it is full before a write, the rotating media must be spun-up, the request satisfied, and NVCache content flushed to disk using both pinned set removal and traditional disk I/O commands. The host can put the disk in standby mode again when the spin-down algorithm deems it desirable to do so. We assume this method because it provides us with complete control over a hybrid disk, allowing us to implement a fine-grain adaptive spin-down algorithm and I/O subsystem enhancements to exploit a hybrid disk’s media characteristics. Alternatively, a host could rely on the NV Cache Power Mode to provide all aspects of power management. However, there are several limitations with this approach: the minimum high-power time is not dynamic, it assumes the disk controller implements the correct spin-down policy, and the NVCache may not be a suitable I/O destination for certain workloads. A host could implement its own coarse-grain spin-down algorithm, by repeatedly entering and exiting the NV Cache Power Mode, recording I/O response times to implicitly infer when the rotating media is spun-up. In this way, a host can utilize its own spin-down algorithm, but still has no control over NVCache management. Note that we omit pinned and unpinned references for the remainder of this work as we no longer refer to the unpinned set.Mean Time To Failures and Mean Time Between Failures are widely used metrics to express disk reliability. However, disk manufacturers also provide a duty cycle rating. Duty cycle rating is the number of times rotating media can be spun down before the chances of failure increase to more than 50% on drive spin-up. When controlling a disk’s power state with a spin-down algorithm, the duty cycle metric is potentially more important than either MTBF or MTTF because a spin-down algorithm results in an accelerated consumption of duty cycles. In addition to duty cycles, hybrid disks also have flash memory reliability—flash memory blocks have a rated number of erase cycles they can endure before errors are expected. Today’s hard disks generally consume 5–10 times more energy while in active than in standby mode. As a result, adaptive spin-down algorithms are very aggressive— it is more efficient to spin-down after only a few seconds of idle time. With such short idle times the number of duty cycles increases dramatically. Duty cycle terminology varies, depending on drive class and technology. Typically, 3.5 in drives refer to duty cycles as Contact Start/Stop Cycles , where the head comes to rest on a landing zone on the platter during a power-down. An alternate technology, ramp load/unload, is typically used in notebook drives, where the head comes to rest off the side of the platter. Drives using CSS technology have duty cycle ratings in the range of 50,000, while drives with ramp load/unload technology are in the range of 500,000, mostly due to reduced stiction effects. With current compact flash specifications, the number of erase operations per block is typically rated at 100,000 with 256KB sized erase blocks. A hybrid disk containing a 256MB NVCache can keep its rotating media spun-down while up to 256MB of data is written to it. With optimal wear-leveling and a write-before-erase architecture, a 256MB device can endure over 100 million erase operations before becoming unerasable. An optimal wear-leveling algorithm spreads all writes across the entire device’s physical address space while write-before erase architecture always writes data corresponding to the same LBA to an empty physical location to ensure data corruption does not occur on a bad overwrite. By exceeding the block erase rating, flash memory blocks may become unerasable, but are still readable. To a host, a hybrid disk with unerasable NVCache blocks should appear as a traditional disk.Spin-down algorithms which control the power state of traditional hard disks are efficient at reducing disk power consumption. There is little room for improvement of such algorithms, which dynamically adjust to the most power efficient time-out using machine learning techniques.

Tracing the development of Chinese American Orientalism from the Chinese Village at the World Columbia Exposition in 1893 through the its presentation in China City and New Chinatown on the eve of the Second World War, I demonstrate how this counter-hegemonic discourse eventually was incorporated back into mainstream Orientalism and used to justify the needs of a diversifying nation-state.This dissertation makes important contributions to a number of areas of study including racial representations in Hollywood film, Asian American participation in the film industry, the history of California and the American West, and the sociology of race. As an interdisciplinary project produced in the Ethnic Studies Department at U.C. Berkeley, the dissertation remains in conversation with disciplines including film and media studies, U.S. history, and urban sociology. First and foremost though, this project is grounded in the political and epistemological imperatives of Asian American studies. While the field of film studies has had a robust and wide-ranging engagement with Asian cinema, film studies work on Asian Americans relationship to the Hollywood film industry has remained much more limited. Due in part to the paradigm of national cinema, it seems at times as if the field of film studies has difficulty comprehending an Asian American subjectivity outside of the lens of Diaspora. That is to say that film studies scholars are often more comfortable seeing film and media representations produced by people of Chinese descent in North American as part of cultural Diaspora grounded in East Asia,square pot than they are of seeing these works alongside those of African American, Native American and Latinx cultural producers engaged with concepts of race, difference, and social power.

Because of this, the limited scholarship on race and cinema in film studies has developed primarily through a focus on African American engagement with film, leaving work on Asian American, Native American, and Latinx film participation much less developed. Given this paradigm, it should not be surprising that the earliest scholarship on Asian Americans and film developed not out of film studies but rather out of the field of Ethnic Studies in the 1970s. At a moment when film studies was dominated by questions of psychoanalytic film theory with its focus on the cinematic apparatus and its effects of film on the subjectivity of the film spectator, Asian American activists, media makers, and academics were forging the foundations of the scholarship on Asian Americans and film. While there were no essays on film or video included in the earliest Asian American studies reader Roots published by UCLA Asian American Studies center in 1971, the follow up reader Counterpoint published in 1976 contains a section on “Communication and Mass Media” with an essay by Judy Chu on Anna May Wong.Around the same time the author Frank Chin along with members of the Combined Asian American Research began the process of interviewing Asian American actors and others who associated with the film industry.The decade also witnessed the publication of the first monograph devoted to the topic in Eugene Wong’s On Visual Media Racism. Developing out of this earliest scholarship, Asian American studies has advanced its own academic narrative on Asian American engagement with film. This scholarship begins by focusing primarily on issues of Asian American representation on screen during the silent film and classical Hollywood periods. This scholarship on Asian American representation during the silent and classical periods is supplemented by work on well-known Asian American performers such as Anna May Wong, Philip Ahn, and Sessue Hayakawa.The focus of the field then shifts to examine Asian Americans as media producers beginning in the 1970s with the advent of Asian American Asian American media collectives such as Visual Communications and Asian Cinevisions .

In this way the scholarship in Asian American studies on film moves broadly from a focus on Asian Americans as an object of the cinematic gaze in the period before 1970 and then shifts to focus on film as a medium for Asian American self-representation in the period after 1970. Work on Chinatown in the silent and classical film periods follows this trend by focusing on Chinese Americans as objects of representation. There exists a number of essays on the D.W. film Broken Blossoms, studies of Fu Manchu and Charlie Chan Films, and essays and books about Anna May Wong.There are a handful of exceptions to this, most notably work by Ruth Mayer and Bjorn A. Schmidt.Schmidt’s book examines cinematic depictions of Chinese Americans as productive forces that shaped immigration laws and policies in the period between 1910s and the 1930s. In two chapters devoted to Chinatown films, Schmidt shows first the way that Chinatown films constructed dominant conceptions of an old Chinatown as an underground site of violent crime against representations of a new Chinatown as modern and built for tourists. Bjorn then moves on to discuss the ways that many silent Chinatown films replicated the tourist gaze of the Chinatown tour. Mayer in her essay on Chinatown films demonstrates the importance of the curio store to silent cinematic representations of Chinatown during a moment when consumer culture in the United States was both consolidating and diversifying. This dissertation contributes to and departs from this recent scholarship in that it shifts the focus away from the ways that film represented Chinatowns and instead focuses on the Chinatown residents as cultural producers. While drawing heavily on scholarship within film studies on Asian American representations and stars, this project foregrounds the way members of the ethnic enclave utilized Chinatown as a medium of cultural production. Los Angeles Chinatown’s proximity to the film industries magnified the opportunities for local Chinese Americans to utilize Chinatown to mediate dominant ideas of race, gender, and nation, but the film industry did not create these opportunities. Chinese American merchants in New York and San Francisco beginning in the late nineteenth and early twentieth centuries began using Chinatown as a medium of cultural production to advance their own depictions of Chinese people.

The rising popularity of film as one of the most popular forms of leisure ensured that by the 1930s, Chinese Americans in Los Angeles possessed a greater ability to shape the national idea of Chinatown than Chinese Americans in New York and San Francisco. Given this focus on the development of race and gender as social categories within the United States, this dissertation is also in conversation with the literature within the field of sociology on Chinatowns as ethnic enclaves. Whereas the topic of Asian American engagement with film has remained somewhat marginal to film studies,drainage collection pot the topic of Chinatown was central not only to the development of sociological theories of ethnic enclaves in the first half of the twentieth century but more broadly to the development of the entire field of urban sociology around the same period. Many early sociological studies on Chinese Americans were influenced by the work by Robert Park and his Chicago School of urban sociology and his work from the first half of the twentieth century. Park argued in his race relations cycle that when two ethnic or racial groups come in contact with one another these groups go through a four-stage cycle of contact, conflict, accommodation, and eventually assimilation.This and other ideas within the Chicago School of sociology were deeply rooted in notions of human ecology, which is the study of the ways humans relate to one another and to their environment. Park believed that human life was divided into two levels the biotic and the cultural and that social organizations of cities were a direct result of the competition for resources.Focusing on human biology as a basis for difference, scholars in the Chicago School largely rejected earlier continental thinkers like Max Weber, Karl Marx, and George Simmel, who saw the larger social and economic forces of capitalism as being fundamental to understanding human interaction.As such, these early sociologists were not interested in offering a systemic critique of American nationalism, racism, or empire, nor were they concerned in any but the most marginal ways with determining how these and other forms of power structured the lives of Chinese Americans. Rather sociologists studying Chinese Americans influenced by the Chicago School asked a much less critical set of questions about the extent to which Chinatowns facilitated the assimilation of Chinese Americans into US society.The earliest scholarship on Los Angeles Chinatown developed out of this framework and was produced by a handful of Chinese American graduate students in the Sociology Department at the University of Southern California between the 1930s and 1950s. Master’s theses by Kit King Louis, Mabel Sam Lee, and Kim Fong Tom as well as a doctoral dissertation by Wen-hui Chen all addressed issues of Chinese American assimilation and generational differences in Chinese American ethnic enclave in Los Angeles. In addition to these studies in sociology, Master’s theses by Charles Ferguson in Political Science at UCLA , Edwin Bingham in History at Occidental College , and by Shan Wu in the business school at USC from this same period represent some of the earliest scholarship on Chinese Americans in Los Angeles.

While the model advanced by Park is no longer the central lens used by urban sociologists, the way that scholars in this tradition define Chinatown has remained surprisingly similar to this earlier generation of ethnic enclave scholars. Scholars in sociology continue to use the term Chinatown to mean Chinese American ethnic enclave and in the process these sociologists foreground ties of ethnicity and culture over ties of place and geography. For example in 1992 sociologist Min Zhou wrote, “I treat Chinatown as an economic enclave embedded in the very nature of the community’s social structure offering a positive alternative to immigrant incorporation.”She goes on to explain that this enclave “is not so much a geographical concept as an organizational one.”Zhou is clear that this economic enclave must be distinguished from an ethnic neighborhood. While most of the businesses in Zhou’s enclave are concentrated in Manhattan’s Chinatown, many are situated elsewhere. Using this definition, she further excludes from her study non-Chinese owned businesses that are based in Chinatown.Peter Kwong was a scholar who was openly critical of many of the arguments advanced by Min Zhou, and yet he nonetheless worked from a similar definition of Chinatown as an ethnic enclave tied together by social and economic relationships.Thus one of the Chicago School’s most long lasting influences on the study of Chinese Americans may be a definition of Chinatown as an ethnic enclave, loosely connected by place and bound primarily by social and ethnic ties. At it’s best this ethnic enclave literature remind us that Chinatowns are not homogenous but rather socially stratified collections of individuals, institutions, and organizations. Works in this ethnic enclave tradition like Judy Yung’s Unbound Feet along with the Chinese Historical Society of Southern California’s Linking our Lives focus on how gender stratifies and influences the lives of women in San Francisco and Los Angeles Chinatown respectively.Other scholars have taken a more global approach. Work by Peter Kwong foregrounds nationality as opposed to race while discussing divisions of class in New York Chinatown. Jan Lin’s Reconstructing Chinatown shows how global capital interacted with national, and local forces to shape the nature of Chinatown. Regardless of whether these scholars focus primarily on the stratification within the ethnic community in a way that is US-centric or on stratification within the ethnic community in a way that links the global, national, and the local, these and other works in the ethnic enclave tradition remind us that power structures Chinese ethnic enclaves just as it structures the rest of society. While there have not been many recent academic studies that look at Los Angeles Chinatown in the first half of the twentieth century, key historical studies have focused on the Los Angeles Plaza and the other areas that make up the core of Los Angeles. This project builds on this growing literature on the multiethnic history of Los Angeles. As part of his broader exploration of the Los Angeles Plaza, William Estrada looks at the development of China City in relationship to Olvera Street contrasting Christine Sterling’s roles in the two projects.Mark Wild looks at Chinese as one group that lived in what he calls the central districts of Los Angeles in the first three decades of the twentieth century.