On bialgebras associated with paths and essential paths on ADE graphs

We define a graded multiplication on the vector space of essential paths on a graph $G$ (a tree) and show that it is associative. In most interesting applications, this tree is an ADE Dynkin diagram. The vector space of length preserving endomorphisms of essential paths has a grading obtained from the length of paths and possesses several interesting bialgebra structures. One of these, the Double Triangle Algebra (DTA) of A. Ocneanu, is a particular kind of quantum groupoid (a weak Hopf algebra) and was studied elsewhere; its coproduct gives a filtrated convolution product on the dual vector space. Another bialgebra structure is obtained by replacing this filtered convolution product by a graded associative product.It can be obtained from the former by projection on a subspace of maximal grade, but it is interesting to define it directly, without using the DTA. What is obtained is a weak bialgebra, not a weak Hopf algebra

Differential adaptation strategies by agro-ecological zones in African livestock management

This paper examines how farmers have adapted their livestock operation to the current climate in each agro-ecological zone in Africa. The authors examine how climate has affected the farmer's choice to raise livestock or not and the choice of animal species. To measure adaptation, the analysis regresses the farmer's choice on climate, soil, water flow, and socio-economic variables. The findings show that climate does in fact affect the farmer's decision about whether to raise livestock and the species. The paper also simulates how future climates may alter these decisions using forecasts from climate models and the estimated model. With a hot dry scenario, livestock ownership will increase slightly across all of Africa, but especially in West Africa and high elevation agro-ecological zones. Dairy cattle will decrease in semi-arid regions, sheep will increase in the lowlands, and chickens will increase at high elevations. With a mild and wet scenario, however, livestock adoption will fall dramatically in lowland and high latitude moist agro-ecological zones. Beef cattle will increase and sheep will fall in dry zones, dairy cattle will fall precipitously and goats will rise in moist zones, and chickens will increase at high elevations but fall at mid elevations. Livestock adaptations depend on the climate scenario and will vary across the landscape. Agro-ecological zones are a useful way to capture how these changes differ from place to place.Livestock&Animal Husbandry,Wildlife Resources,Peri-Urban Communities,Rural Urban Linkages,Dairies&Dairying

Long-term adaptation : selecting farm types across agro-ecological zones in Africa

Using economic data from more than 8,500 household surveys across 10 African countries, this paper examines whether the choice of farm type depends on the climate and agro-ecological zone of each farm. The paper also studies how farm type choice varies across farmers in each zone, using a multinomial logit choice model. Farmers are observed to choose from one of the following five types of farms: rainfed crop-only, irrigated crop-only, mixed rainfed (crop and livestock), mixed irrigated, and livestock-only farming. The authors compare current decisions against future decisions as if the only change were climate change. They focus on two climate scenarios from existing climate models: the Canadian Climate Centre scenario, which is hot and dry, and the Parallel Climate Model scenario, which is mild and wet. The results indicate that the change in farm types varies dramatically by climate scenario but also by agro-ecological zone. Policy makers must be careful to encourage the appropriate suite of measures to promote the most adapted farm type to each location.Crops&Crop Management Systems,Climate Change,Agriculture&Farming Systems,Livestock&Animal Husbandry,Rural Development Knowledge&Information Systems

Differential adaptation strategies to climate change in African cropland by agro-ecological zones

This paper quantifies how African farmers have adapted their crop and irrigation decisions to their farm's current agro-ecological zone. The results indicate that farmers carefully consider the climate and other conditions of their farm when making these choices. These results are then used to forecast how farmers might change their irrigation and crop choice decisions if climate changes. The model predicts African farmers would adopt irrigation more often under a very hot and dry climate scenario but less often with a mild and wet scenario. However, farms in the deserts, lowland humid forest, or mid elevation humid forest would reduce irrigation even in the very hot and dry climate scenario. Area under fruits and vegetables would increase Africa-wide with the very hot and dry climate scenario, except in the lowland semi-arid agro-ecological zone. Millet would increase overall under the mild and wet scenario, but decline substantially in the lowland dry savannah and lowland semi-arid agro-ecological zones. Maize would be chosen less often across all the agro-ecological zones under both climate scenarios. Wheat would decrease across Africa. The authors recommend that care must be taken to match adaptations to local conditions because the optimal adaptation would depend on the agro-ecological zone and the climate scenario.Crops&Crop Management Systems,Climate Change,Food&Beverage Industry,Renewable Energy,Rural Poverty Reduction

Riverine ecosystem services and the thermoelectric sector: strategic issues facing the Northeastern United States

Major strategic issues facing the global thermoelectric sector include environmental regulation, climate change and increasing electricity demand. We have addressed such issues by modeling thermoelectric generation in the Northeastern United States that is reliant on cooling under five sensitivity tests to evaluate losses/gains in power production, thermal pollution and suitable aquatic habitat, comparing the contemporary baseline (2000–2010) with potential future states. Integral to the analysis, we developed a methodology to quantify river water availability for cooling, which we define as an ecosystem service. Projected climate conditions reduce river water available for efficient power plant operations and the river\u27s capacity to absorb waste heat, causing a loss of regional thermoelectric generation (RTG) (2.5%) in some summers that, compared to the contemporary baseline, is equal to the summertime electricity consumption of 1.3 million Northeastern US homes. Vulnerabilities to warm temperatures and thermal pollution can be alleviated through the use of more efficient natural gas (NG) power plants that have a reduced reliance on cooling water. Conversion of once-through (OT) to cooling tower (CT) systems and the Clean Water Act (CWA) temperature limit regulation, both of which reduce efficiencies at the single plant level, show potential to yield beneficial increases in RTG. This is achieved by obviating the need for large volumes of river water, thereby reducing plant-to-plant interferences through lowering the impact of upstream thermal pollution and preserving a minimum standard of cooling water. The results and methodology framework presented here, which can be extrapolated to other regional assessments with contrasting climates and thermoelectric profiles, can identify opportunities and support decision-making to achieve more efficient energy systems and riverine ecosystem protection

A ricardian analysis of the distribution of climate change impacts on agriculture across agro-ecological zones in Africa

This paper examines the distribution of climate change impacts across the 16 agro-ecological zones in Africa using data from the Food and Agriculture Organization combined with economic survey data from a Global Environment Facility/World Bank project. Net revenue per hectare of cropland is regressed on a set of climate, soil, and socio-economic variables using different econometric specifications"with"and"without"country fixed effects. Country fixed effects slightly reduce predicted future climate related damage to agriculture. With a mild climate scenario, African farmers gain income from climate change; with a more severe scenario, they lose income. Some locations are more affected than others. The analysis of agro-ecological zones implies that the effects of climate change will vary across Africa. For example, currently productive areas such as dry/moist savannah are more vulnerable to climate change while currently less productive agricultural zones such as humid forest or sub-humid zones become more productive in the future. The agro-ecological zone classification can help explain the variation of impacts across the landscape.Climate Change,Global Environment Facility,Common Property Resource Development,Rural Poverty Reduction,Transport and Environment

Decreasing Liability Contracts

Like constructing a building, performance on many contracts occurs in phases. As time passes, the promisor sinks more costs into performance and less expenditure remains. For phased performance, we show that optimal liability for the breaching party decreases as the remaining costs of completing performance decrease. In brief, efficiency requires a decreasing liability contract. To implement such a contract, we recommend deducting past expenditure on incomplete performance from liability. We show that progress payment contracts, which are commonplace in some industries, are materially equivalent to decreasing liability contracts. Our analysis should prove useful for elucidating progress payment contracts and for drafting and litigating phased contracts

Can Restitution Save Fragile Spiderless Networks?

This Article examines the dramatic increase in business networks in recent decades and considers whether the law can play a useful role in supporting the efficient functioning of these inter-firm relationships for coordination and cooperation. Repeat play, reputational sanctions, and norms of trust and reciprocity are the common explanations for the flourishing of networks in many industries and places. But the evidence also shows that a certain class of networks often fails to survive or function effectively and beneficial cooperation among these network members is impaired. These fragile networks develop organically without a controlling party or hierarchy at the center of the network to facilitate network formation. Lacking a controlling entity, they are webs without any spider. Clusters of industrial districts are traditional examples of this class of networks. More recently, the information revolution has stimulated a dramatic increase in another type of spiderless network: networks of strategic alliances are now a common means of organizing collaborations among firms in high technology and R&D intensive settings. In both types of spiderless networks there are no legal mechanisms to control moral hazard and free riding risks during the period of network formation and operation. We show how in theory the law could support spiderless networks by allowing firms who externalize benefits to other firms in the network to recover for those benefits. Practical considerations may limit the implementation of a full-blown right of restitution. Nevertheless, by recognizing a limited right to recover for uncompensated costs and benefits in appropriate cases, the law can function as a background norm for sharing costs and benefits among network members, motivating them to overcome daunting coordination problems. We consider several implementation issues, show how they might be resolved, and apply our analysis to a set of well-known spiderless networks

Can China continue feeding itself ? the impact of climate change on agriculture

Several studies addressing the supply and demand for food in China suggest that the nation can largely meet its needs in the coming decades. However, these studies do not consider the effects of climate change. This paper examines whether near future expected changes in climate are likely to alter this picture. The authors analyze the effect of temperature and precipitation on net crop revenues using a cross section consisting of both rainfed and irrigated farms. Based on survey data from 8,405 households across 28 provinces, the results of the Ricardian analysis demonstrate that global warming is likely to be harmful to China but the impacts are likely to be very different in each region. The mid latitude region of China may benefit from warming but the southern and northern regions are likely to be damaged by warming. More precipitation is beneficial to Chinese farmers except in the wet southeast. Irrigated and rainfed farmers have similar responses to precipitation but not to temperature. Warmer temperatures may benefit irrigated farms but they are likely to harm rainfed farms. Finally, seasonal effects vary and are offsetting. Although we were able to measure the direct effect of precipitation and temperature, we could not capture the effects of change in water flow which will be very important in China. Can China continue feeding itself if climate changes? Based on the empirical results, the likely gains realized by some farmers will nearly offset the losses that will occur to other farmers in China. If future climate scenarios lead to significant reductions in water, there may be large damages not addressed in this study.Climate Change,Crops&Crop Management Systems,Global Environment Facility,Common Property Resource Development,Rural Development Knowledge&Information Systems