14,859 research outputs found

    Polymeric compositions and their method of manufacture

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    Filled polymer compositions are made by dissolving the polymer binder in a suitable sublimable solvent, mixing the filler material with the polymer and its solvent, freezing the resultant mixture, and subliming the frozen solvent from the mixture from which it is then removed. The remaining composition is suitable for conventional processing such as compression molding or extruding. A particular feature of the method of manufacture is pouring the mixed solution slowly in a continuous stream into a cryogenic bath wherein frozen particles of the mixture result. The frozen individual particles are then subjected to the sublimation

    Sintering characteristics and properties of PuS and PuP are determined

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    Report on the preparation of plutonium monosulphide and plutonium monophosphide includes a description of the sintering characteristics and properties of these high-temperature compounds. data on weight loss, microstructure, density, melting point, thermal expansion, microhardness, Seebeck coefficient, and thermal diffusion are included

    Integrability of V. Adler's discretization of the Neumann system

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    We prove the integrability of the discretization of the Neumann system recently proposed by V. Adler.Comment: 9 pp., LaTe


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    Although rice accounts for approximately forty-four percent of land under cultivation and forty-six percent of caloric intake in Madagascar, most farmers cannot produce enough rice to feed their families. Total rice production increased little in the country during the 1990s, and yields were stagnant and well below world average yields. Because of the importance of rice for both family income and nutrition and because of the significant role upland rice cultivation plays in deforestation in Madagascar, intensification of lowland rice production has been a major focus of many development interventions. The System of Rice Intensification (SRI) is a method that has been promoted and closely followed in Madagascar for more than ten years. SRI is remarkable for its dramatic increases in yields achieved without external inputs. While the method is more labor intensive, the doubling or even tripling of yields would appear to make the method extremely profitable. Despite its apparent potential and intensive extension efforts in some areas, adoption rates have generally been low, and the average rate of disadoption (the percentage of households who have tried the method and who no longer practice it) for study area was 40 percent. Using survey data from five communities in Madagascar, a sample selection model and a probit model were used to study three related choices farmers must make concerning the SRI. The first is whether to try the method, and then, conditional on having tried the method a farmer must decide how much of his lowland rice area to put in the SRI. Finally, for all subsequent years, a farmer must decide whether to continue using the method. While many adoption studies have looked at the role of liquidity and labor, few have done so in a dynamic setting. We take advantage of reliable recall data and NGO records on technology use to construct a panel data set, which was used to analyze the effects of learning, labor, liquidity, and social benefits over a five-year period. Learning has been the focus of several recent adoption studies, but this study tries to separate the learning effects from the effects of compliance with authority figures and with social and cultural norms. The results show that planting-season labor and liquidity constraints are extremely important factors in the adoption decisions of Malagasy farmers. Although the method is low-external input, the poorest farmers are not able to take advantage of the technology. This result is very important for development policy-makers in Madagascar who have often seen rice intensification as the most important means by which to alleviate rural poverty in Madagascar.Farm Management,

    Better Technology, Better Plots or Better Farmers? Identifying Changes in Productivity and Risk Among Malagasy Rice Farmers

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    In assessing the productivity gains of a new technology, it is often difficult to determine the extent to which observed output gains are due to the technology itself, rather than to the skill of the farmer or the quality of the plot on which the new technology is tried. This problem of attribution is especially important when technologies are not embodied in purchased inputs such as seed or machinery but result instead from changed farmer cultivation practices. Using data based on observations of farmers in Madagascar who simultaneously practice both a newly introduced and traditional rice production methods, we introduce a method for properly attributing observed productivity and risk changes among new production methods, farmers and plots by controlling for farmer and plot heterogeneity using differential production and yield risk functions. Our results help resolve several outstanding puzzling associated with observed low and incomplete uptake and high rates of disadoption of the new system of rice intensification (SRI) in spite of consistent, sharp yield increases on small farmers' fields without application of additional external inputs.Productivity Analysis,

    The beauty and the boost: A Higgs boson tale:Measurements of Higgs boson production at high energy in decays to bottom quarks and their interpretations with the ATLAS experiment at the LHC

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    Precision measurements of the Higgs boson’s properties are a powerful tool to look for deviations from the predictions of the Standard Model (SM) of particle physics. The 139 fb−1^{-1} of proton-proton collision data which have been collected by the ATLAS experiment during Run 2 of the LHC, offer an opportunity to investigate rare Higgs-boson topologies, which are particularly sensitive to new physics scenarios but experimentally difficult to access. Several such measurements, which target Higgs-boson decays to heavy-flavour quarks, as well as their combinations are presented in this thesis. A novel analysis that measures Higgs-boson production in association with a heavy vector boson V (VH, with V=W,Z) at high transverse momentum pTVp_{\text{T}}^{V} is presented. Dedicated Higgs-boson reconstruction techniques are applied to reconstruct the highly Lorentz-boosted Higgs-boson decays into pairs of bottom quarks. The measurement is subsequently combined with a VH cross-section measurement at low and intermediate pTVp_{\text{T}}^{V} to provide a differential cross-section measurement in kinematic fiducial volumes over the largest possible pTVp_{\text{T}}^{V} range. All cross-section measurements agree with the SM predictions within relative uncertainties that range from 30% to 300%. The results are furthermore interpreted as limits on the parameters of a SM effective field theory. Finally, a combination of measurements of Higgs decays to heavy-flavour quarks is used to experimentally determine that the Higgs-boson coupling to charm quarks is weaker than to bottom quarks, as predicted by the SM

    Missed opportunities and missing markets: Spatio-temporal arbitrage of rice in Madagascar

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    This paper uses an exceptionally rich data set to test the extent to which markets in Madagascar are integrated across space, time, and form (in converting from paddy to rice) and to explain some of the factors that limit arbitrage and price equalization within a single country. In particular, we use rice price data across four quarters of 2000-2001 along with data on transportation costs and infrastructure availability for nearly 1400 communes in Madagascar to examine the extent of market integration at three different spatial scales sub-regional, regional, and national and determine whether non-integration is due to high transfer costs or lack of competition. The results indicate that markets are fairly well integrated at the sub-regional level and that factors such as high crime, remoteness, and lack of information are among the factors limiting competition. A lack of competition persists at the regional level and high transfer costs impede spatial market integration at the national level. Only six percent of rural communes appear to be intertemporally integrated and there appear to be significant untapped opportunities for interseasonal arbitrage. Income is directly and strongly related to the probability of a commune being in interseasonal competitive equilibrium.Marketing,

    Spin chain from membrane and the Neumann-Rosochatius integrable system

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    We find membrane configurations in AdS_4 x S^7, which correspond to the continuous limit of the SU(2) integrable spin chain, considered as a limit of the SU(3) spin chain, arising in N=4 SYM in four dimensions, dual to strings in AdS_5 x S^5. We also discuss the relationship with the Neumann-Rosochatius integrable system at the level of Lagrangians, comparing the string and membrane cases.Comment: LaTeX, 16 pages, no figures; v2: 17 pages, title changed, explanations and references added; v3: more explanations added; v4: typos fixed, to appear in Phys. Rev.

    The impact of prior information on estimates of disease transmissibility using Bayesian tools

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    The basic reproductive number (R₀) and the distribution of the serial interval (SI) are often used to quantify transmission during an infectious disease outbreak. In this paper, we present estimates of R₀ and SI from the 2003 SARS outbreak in Hong Kong and Singapore, and the 2009 pandemic influenza A(H1N1) outbreak in South Africa using methods that expand upon an existing Bayesian framework. This expanded framework allows for the incorporation of additional information, such as contact tracing or household data, through prior distributions. The results for the R₀ and the SI from the influenza outbreak in South Africa were similar regardless of the prior information (R0 = 1.36-1.46, ÎŒ = 2.0-2.7, ÎŒ = mean of the SI). The estimates of R₀ and ÎŒ for the SARS outbreak ranged from 2.0-4.4 and 7.4-11.3, respectively, and were shown to vary depending on the use of contact tracing data. The impact of the contact tracing data was likely due to the small number of SARS cases relative to the size of the contact tracing sample