2,902 research outputs found

    Ensemble inequivalence: A formal approach

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    Ensemble inequivalence has been observed in several systems. In particular it has been recently shown that negative specific heat can arise in the microcanonical ensemble in the thermodynamic limit for systems with long-range interactions. We display a connection between such behaviour and a mean-field like structure of the partition function. Since short-range models cannot display this kind of behaviour, this strongly suggests that such systems are necessarily non-mean field in the sense indicated here. We further show that a broad class of systems with non-integrable interactions are indeed of mean-field type in the sense specified, so that they are expected to display ensemble inequivalence as well as the peculiar behaviour described above in the microcanonical ensemble.Comment: 4 pages, no figures, given at the NEXT2001 conference on non-extensive thermodynamic

    Extending General Equilibrium to the Tariff Line: U.S. Dairy in the DOHA Development Agenda

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    Market access has been at the core of eight negotiating rounds of the General Agreement on Tariffs and Trade (GATT). Yet, agricultural trade remains a heavily protected sector, characterized by higher tariffs relative to industrial goods, large tariff dispersions, numerous specific tariffs and systems of tariff-rate-quotas. This has made the analysis of trade liberalization a formidable task among policy analysts. Previous studies of agricultural trade liberalization have used partial or general equilibrium models of trade. However, each of these modeling strategies has their drawbacks. General equilibrium (GE) models have been criticized because they face serious aggregation issues and miss much of the policy detail that occurs at the tariff line. Partial equilibrium (PE) models on the other hand are often more disaggregated but lack internal consistency and have nothing to say about the economy-wide effects from trade reform. The purpose of this paper is threefold. One, we develop a methodology that combines PE and GE modeling techniques permitting us to extend GE to the tariff line. Two, we introduce a fully disaggregated U.S. dairy sector and compare PE and GE liberalization results from global dairy reform, thereby offering some insight into the potential errors implicit in current GE studies. Finally, we illustrate how our methodology allows for an explicit treatment of tariff rate quotas in the U.S. dairy sector on a bilateral basis for narrowly defined product lines.agricultural trade, mixed-complementarity problem, partial equilibrium, general equilibrium, Doha Development Agenda, WTO, International Relations/Trade, Livestock Production/Industries, F01, F17, Q17, Q18,

    Growth, globalization, and gains from the Uruguay Round

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    Emphasizing the importance of evaluating the Uruguay Round in the context of a changing world economy, the authors base their projections on a model that incorporates certain economic shifts: 1) that the center of economic gravity will shift toward the South and toward Asia (a shift that is already under way and shows no signs of abating), and 2) that the pattern of comparative advantage will continue to change, with the East Asian economies gaining comparative advantage in the production of physical and human-capital-intensive products. The authors argue that these changes in the global economy significantly affect their analysis of the Uruguay round reforms, for two reasons. First, with the global distribution of trade and production shifting toward Asia, the deeper Uruguay Round cuts inthat region become more important, giving rise to a 17 percent increase in the proportionate welfare gain after implementation of tariff cuts. Second, without the Round, almost all of the bilateral quotas associated with the Multifibre Arrangement (MFA) would have become more binding and the resulting distortion would have been significantly greater. In this analysis, the global gain from MFA reform is 60 percent greater than it would have been without taking into account the effects of growth. Of course, procedures for implementation of the MFA reforms are more complex than they have conveyed for purposes of analysis. In practice, one must also consider the impact of accel quota growth under the Agreement on Textiles and Clothing. But even when the Agreement on Textiles and Clothing is implemented over the period for which projections were made, quota rents rise for many bilateral flows. This is a consequence both of shifts in comparative advantage toward the supplying countries and of simultaneous cuts in tariffs on textiles and clothing. The projections approach used here may be viewed as a logical extension of the growing econometric literature seeking to explain the determinants of economic growth through regression analysis. By offering a bridge between econometric evidence and computable general equilibrium modeling, the authors hope to combine the two approaches to help shed light on the interaction between trade reform and economic growth.Payment Systems&Infrastructure,Economic Theory&Research,Environmental Economics&Policies,Export Competitiveness,Globalization and Financial Integration,Environmental Economics&Policies,Trade and Regional Integration,Achieving Shared Growth,Economic Theory&Research,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT

    Cognitive Habits and Memory Distortions in Anxiety and Depression

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    When anxious or depressed people try to recall emotionally ambiguous events, they produce errors that reflect their habits of interpreting ambiguity in negative ways. These distortions are revealed by experiments that evaluate performance on memory tasks after taking interpretation biases into account—an alternative to the standard memory-bias procedure that examines the accuracy of memory for clearly emotional material. To help establish the causal role of interpretation bias in generating memory bias, these disortions have been simulated by training interpretation biases in nondisordered groups. The practical implications of these findings for therapeutic intervention are discussed; future directions are described

    Crosstalk between nanotube devices: contact and channel effects

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    At reduced dimensionality, Coulomb interactions play a crucial role in determining device properties. While such interactions within the same carbon nanotube have been shown to have unexpected properties, device integration and multi-nanotube devices require the consideration of inter-nanotube interactions. We present calculations of the characteristics of planar carbon nanotube transistors including interactions between semiconducting nanotubes and between semiconducting and metallic nanotubes. The results indicate that inter-tube interactions affect both the channel behavior and the contacts. For long channel devices, a separation of the order of the gate oxide thickness is necessary to eliminate inter-nanotube effects. Because of an exponential dependence of this length scale on dielectric constant, very high device densities are possible by using high-k dielectrics and embedded contacts

    Ensemble inequivalence in systems with long-range interactions

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    Ensemble inequivalence has been observed in several systems. In particular it has been recently shown that negative specific heat can arise in the microcanonical ensemble in the thermodynamic limit for systems with long-range interactions. We display a connection between such behaviour and a mean-field like structure of the partition function. Since short-range models cannot display this kind of behaviour, this strongly suggests that such systems are necessarily non-mean field in the sense indicated here. We illustrate our results showing an application to the Blume-Emery-Griffiths model. We further show that a broad class of systems with non-integrable interactions are indeed of mean-field type in the sense specified, so that they are expected to display ensemble inequivalence as well as the peculiar behaviour described above in the microcanonical ensemble.Comment: 12 pages, no figure

    Biofuels and their By-Products: Global Economic and Environmental Implications

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    The biofuel industry has been rapidly growing around the world in recent years. Several papers have used general equilibrium models and addressed the economy-wide and environmental consequences of producing biofuels at a large scale. They mainly argue that since biofuels are mostly produced from agricultural sources, their effects are largely felt in agricultural markets with major land use and environmental consequences. In this paper, we argue that virtually all of these studies have overstated the impact of liquid biofuels on agricultural markets due to the fact that they have ignored the role of by-products resulting from the production of biofuels. Feed by-products of the biofuel industry, such as Dried Distillers Grains with Solubles (DDGS) and biodiesel by-products (BDBP) such as soy and rapeseed meals, can be used in the livestock industry as substitutes for grains and oilseed meals used in this industry. Hence, their presence mitigates the price impacts of biofuel production on the livestock and food industries. The importance of incorporating by-products of biofuel production in economic models is well recognized by some partial equilibrium analyses of biofuel production. However, to date, this issue has not been tackled by those conducting CGE analysis of biofuels programs. Accordingly, this paper explicitly introduces DDGS and BDBP, the major by-products of grain based ethanol and biodiesel production processes, into a worldwide CGE model and analyzes the economic and environmental impacts of regional and international mandate policies designed to stimulate bioenergy production and use. We first explicitly introduce by-products of biofuel production into the GTAP-BIO database, originally developed by Taheripour et al. (2007). Then we explicitly bring in DDGS and BDBP into the Energy-Environmental version of the Global Trade Analysis Project (GTAP-E) model, originally developed by Burniaux and Truong (2002), and recently modified by McDougall and Golub (2007) and Birur, Hertel, and Tyner (2008). The structure of the GTAP-E model is redesigned to handle the production and consumption of biofuels and their by-products, in particular DDGS, across the world. Unlike many CGE models which are characterized by single product sectors, here grain based ethanol and DDGS jointly are produced by an industry, named EthanolC. The biodiesel industry also produces two products of biodiesel and BDBP jointly. This paper divides the world economy into 22 commodities, 20 industries, and 18 regions and then examines global impacts of the US Energy Independence and Security Act of 2007 and the European Union mandates for promoting biofuel production in the presence of by-products. We show that models with and without by-products demonstrate different portraits from the economic impacts of international biofuel mandates for the world economy in 2015. While both models demonstrate significant changes in the agricultural production pattern across the world, the model with by-products shows smaller changes in the production of cereal grains and larger changes for oilseeds products in the US and EU, and the reverse for Brazil. For example, the US production of cereal grains increases by 10.8% and 16.4% with and without by-products, respectively. The difference between these two numbers corresponds to 646 million bushels of corn. In the presence of by-products, prices change less due to the mandate policies. For example, the model with no by-products predicts that the price of cereal grains grows 22.7% in the US during the time period of 2006 to 2015. The corresponding number for the model with by-products is 14%. The model with no by-products predicts that the price of oilseeds increases by 62.5% in the EU during 2006-2015. In the presence of by-products, this price grows 56.4%. Finally, we show that incorporating DDGS into the model significantly changes the land use consequences of the biofuel mandate polices.Resource /Energy Economics and Policy, Environmental Economics and Policy,

    The medial malleolar network: A constant vascular base of the distally based saphenous neurocutaneous island flap

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    Summary: Based on 30 fresh cadaver dissections a detailed anatomic study of the medial malleolar network is presented with particular attention to the anastomoses between the latter and the vascular axis that follows the saphenous nerve. The medial malleolar network is formed by the anterior medial malleolar artery, branches from the medial tarsal arteries, the posterior medial malleolar artery and branches from the medial plantar artery. A distinct anterior medial malleolar artery and posterior medial malleolar artery could be identified in 80 and 20%, respectively, as well as constant additional small branches arising from the anterior tibial or posterior tibial artery. A constant anastomosis was found between the arcade formed by the medial tarsal arteries and the medial plantar a. in 60%, and the medial branch of the medial plantar artery in 40%, respectively. This anastomosis always gave rise to branches to the medial malleolar network. In the perimalleolar area and with regard to the great saphenous v. a larger anterior and a smaller posterior branch of the saphenous nerve was found in 100 and 90%, respectively. In all dissections, for both branches of the saphenous nerve two to four small, but distinct anastomoses between the medial malleolar network and the perineural vascular axis were identified. These constant anastomoses represent a new and reliable vascular base for the distally-based saphenous neurocutaneous island flap. Thus, the pivotal point of the flap can be chosen in the area of the medial malleolus without respecting the most distal septocutaneous anastomosis between the perineural vascular axis and the posterior tibial artery. Additionally, an illustrative clinical case is presente
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