Composite electric S-brane solutions with maximal number of branes

In this paper we consider (n+1)-dimensional cosmological model with scalar field and antisymmetric (p+2)-form. Using an electric composite Sp-brane ansatz the field equations for the original system reduce to the equations for a Toda-like system with n(n-1)/2 quadratic constraints on the charge densities. For certain odd dimensions (D = 4m+1 = 5, 9, 13, ...) and (p+2)-forms (p = 2m-1 = 1, 3, 5, ...) these algebraic constraints can be satisfied with the maximal number of charged branes ({\it i.e.} all the branes have non-zero charge densities). These solutions are characterized by self-dual or anti-self-dual charge density forms Q (of rank 2m). For these algebraic solutions with the particular D, p, Q and non-exceptional dilatonic coupling constant \lambda we obtain general cosmological solutions to the field equations and some properties of these solutions are highlighted (e.g. Kasner-like behavior, the existence of attractor solutions). We prove the absence of maximal configurations for p =1 and even D (e.g. for D =10 supergravity models and those of superstring origin).Comment: 19 pages JHEP format, references adde

Using biochar from sewage sludge and other feedstocks in european agroforestry: opportunities and challenges

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Elicitation of expert knowledge on controlling Salmonella in the pork chain

Salmonella is one of the most important risks for food safety, and pork is one of the sources of human salmonellosis. A chain approach is essential to reduce Salmonella in pork products. A survey was carried out among Dutch and Danish experts in the field of Salmonella to evaluate the entire pork supply chain. The aims of the survey were to determine and rank possible management interventions (such as adjusted or new procedures, technical adjustments and control measures), and to estimate the details of the course of infection and contamination. An additional objective was to compare the opinions of experts from different countries and different backgrounds. The two stages in which it was expected that management interventions to improving food safety with respect to Salmonella in pork would be most effective were the the finishing stage (by preventing the spread of Salmonella within the farm) and the slaughtering stage (by preventing cross-contamination). The differences in the opinions of respondents from different backgrounds were mainly reflected by the relative importance they attached to the specific management interventions. For instance, the Danish respondents attached more importance to the purchase of Salmonella-free piglets in the finishing stage and to logistic slaughter. Respondents with a research background seemed to attach most importance to interventions that were also presented in recent literature, such as feeding non-heated grain to finishing pigs. For issues in which multiple stages of a supply chain are involved, a solid basic knowledge about the conditions per stage with respect to the issue is necessary

Multi-energy techniques for radiographic monitoring of chemical composition

A theoretical model of multi-energy radiography (MER) are proposed. It is shown that, as distinct from the conventional radiography, MER allows identification of organic substances and control of their chemical composition. Broad prospects are noted for MER application, specifically, for detection of prohibited substances (explosives, drugs, etc.) during customs and anti-terrorist safety inspection.Comment: 4 pages, 1 figure, RMA-2002 Conference, Ann Arbor, Michigan, US

Cosmological solutions in multidimensional model with multiple exponential potential

A family of cosmological solutions with $(n+1)$ Ricci-flat spaces in the theory with several scalar fields and multiple exponential potential is obtained when coupling vectors in exponents obey certain relations. Two subclasses of solutions with power-law and exponential behaviour of scale factors are singled out. It is proved that power-law solutions may take place only when coupling vectors are linearly independent and exponential dependence occurs for linearly dependent set of coupling vectors. A subfamily of solutions with accelerated expansion is singled out. A generalized isotropization behaviours of certain classes of general solutions are found. In quantum case exact solutions to Wheeler-DeWitt equation are obtained and special "ground state" wave functions are considered.Comment: 22 pages, 1 figur

Physical model of quantum-well infrared photodetectors

A fully quantum mechanical model for electron transport in quantum well infrared photodetectors is presented, based on a self-consistent solution of the coupled rate equations. The important macroscopic parameters like current density, responsivity and capture probability can be estimated directly from this first principles calculation. The applicability of the model was tested by comparison with experimental measurements from a GaAs/AlGaAs device, and good agreement was found. The model is general and can be applied to any other material system or QWIP design

Composite p-branes on Product of Einstein Spaces

A multidimensional gravitational model with several scalar fields, fields of forms and cosmological constant is considered. When scalar fields are constant and composite p-brane monopole-like ansatz for the fields of forms is adopted, a wide class of solutions on product of n+1 Einstein spaces is obtained. These solutions are the composite p-brane generalizations of the Freund-Rubin solution. Some examples including the AdS_m x S^k x... solutions are considered.Comment: 11 pages, Late

The costs and benefits of providing open space in cities

We use the monocentric model of a city to derive a simple cost-benefit rule for the optimal provision of open space. Although many researchers have investigated the value of open space in cities, few of them have compared it to the costs of providing this amenity. The rule derived here is essentially the Samuelson-condition for the optimal provision of a public good, with the price of land as the appropriate indicator for its cost. The condition is made operational by computing the willingness to pay for public and private space on the basis of empirical hedonic price functions for three Dutch cities. The conclusions with respect to the optimal provision of open space differ between the three cities. Further investigation reveals that willingness to pay for parks and public gardens increases with income, although not as fast as that for private residential space.

A Comparative Analysis of Production and Marketing of Bt Cotton and Hybrid Cotton in Saurashtra Region of Gujarat State

The study has revealed that the total cost per hectare is higher in Bt cotton than hybrid cotton. The cost of seeds has been found higher in Bt cotton, whereas hybrid cotton growers incur more cost on insecticides/ pesticides. This shows the effectiveness of the new technology (Bt cotton) for insect resistance. The average total cost of production as well as the bulk line cost have been found lower in Bt cotton. This depicts a reduction in the unit cost of Bt cotton, which is the distinct advantage of the new technology. A higher yield of 29 per cent has been obtained by the Bt cotton farmers over the hybrid cotton growers. The study has identified the constraints in production, and marketing of Bt cotton in the area. Bt cotton has been found a superior technology to hybrid cotton, as it gives higher yield and has low cost of production.Agricultural and Food Policy,