316 research outputs found
Computational method to predict thermodynamic, transport, and flow properties for the modified Langley 8-foot high-temperature tunnel
The Langley 8 foot high temperature tunnel (8 ft HTT) is used to test components of hypersonic vehicles for aerothermal loads definition and structural component verification. The test medium of the 8 ft HTT is obtained by burning a mixture of methane and air under high pressure; the combustion products are expanded through an axisymmetric conical contoured nozzle to simulate atmospheric flight at Mach 7. This facility was modified to raise the oxygen content of the test medium to match that of air and to include Mach 4 and Mach 5 capabilities. These modifications will facilitate the testing of hypersonic air breathing propulsion systems for a wide range of flight conditions. A computational method to predict the thermodynamic, transport, and flow properties of the equilibrium chemically reacting oxygen enriched methane-air combustion products was implemented in a computer code. This code calculates the fuel, air, and oxygen mass flow rates and test section flow properties for Mach 7, 5, and 4 nozzle configurations for given combustor and mixer conditions. Salient features of the 8 ft HTT are described, and some of the predicted tunnel operational characteristics are presented in the carpet plots to assist users in preparing test plans
Factorisation of generalised theta functions. I
We prove a version of "factorisation", relating the space of sections of theta bundles on the moduli spaces of (parabolic, rank 2) vector bundles on curves of genus g and g-1
A facile synthesis of 2-(2'-vinylthiophene)chromones by the modified Baker-Venkataraman tansformation
579-58
Ultrasound sensing using the acousto-optic effect in polymer dispersed liquid crystals
Acousto-optic effects are demonstrated in polymer dispersed liquid crystal (PDLC) films, showing promise for applications in ultrasound sensing. The PDLC films are used to image two displacement profiles of an air-coupled flexural transducers resonant modes at 295 kHz and 730 kHz. Results are confirmed using laser vibrometry. The regions on the transducers with the largest displacements are clearly imaged by the PDLC films, with the resolution agreeing well with laser vibrometry scanning. Imaging takes significantly less time than a scanning system (switching time of a few seconds, as compared to 8 hours for laser vibrometry). Heating effects are carefully monitored using thermal imaging, and are found not to be the main cause of PDLC clearing
Ultrasound sensing using the acousto-optic effect in polymer dispersed liquid crystals
Technical efficiencies and yield variability are comparable across organic and conventional farms
Cotton is essentially a smallholder crop across tropical countries. Being a major cash crop, it plays a decisive role in the livelihoods of cotton-producing farmers. Both conventional and organic production systems offer alternative yet interesting propositions to cotton farmers. This study was conducted in Nimar valley, a prominent cotton-producing region of central India, with the aim of categorically evaluating the contribution of management and fixed factors to productivity on conventional and organic cotton farms. A study framework was developed considering the fixed factors, which cannot be altered within reasonable limits of time, capacity and resources, e.g., landholding or years of age and/or practice; and management factors, which can be altered/influenced within a reasonable time by training, practice and implementation. Using this framework, a structured survey of conventional and organic farms operating under comparable circumstances was conducted. Landholding and soil types were significant contributors/predictors of yield on organic farms. In contrast, landholding was not the main factor related to yields on conventional farms, which produced the highest yields when led by farmers with more than five years of formal education and living in a joint family. Nitrogen application, the source of irrigation (related to timely and adequate supply), crop rotation and variables related to adequate plant population (seed source, germination rate and plant thinning) were the main management factors limiting cotton yields among conventional and organic farms. Both organic and conventional farms in the Nimar valley exhibited a similar pattern of variation in cotton yields and technical efficiency. This study highlights the enormous scope for improving cotton productivity in the region by improving technical efficiency, strengthening extension services and making appropriate policy interventions
Measures on Banach Manifolds and Supersymmetric Quantum Field Theory
We show how to construct measures on Banach manifolds associated to
supersymmetric quantum field theories. These measures are mathematically
well-defined objects inspired by the formal path integrals appearing in the
physics literature on quantum field theory. We give three concrete examples of
our construction. The first example is a family of measures on a
space of functions on the two-torus, parametrized by a polynomial (the
Wess-Zumino-Landau-Ginzburg model). The second is a family \mu_\cG^{s,t} of
measures on a space \cG of maps from to a Lie group (the
Wess-Zumino-Novikov-Witten model). Finally we study a family
of measures on the product of a space of connection s on the trivial principal
bundle with structure group on a three-dimensional manifold with a
space of \fg-valued three-forms on
We show that these measures are positive, and that the measures
\mu_\cG^{s,t} are Borel probability measures. As an application we show that
formulas arising from expectations in the measures \mu_\cG^{s,1} reproduce
formulas discovered by Frenkel and Zhu in the theory of vertex operator
algebras. We conjecture that a similar computation for the measures
where is a homology three-sphere, will yield the
Casson invariant of Comment: Minor correction
Effects of Parvovirus B19 Infection in Renal Transplant Recipients: A Retrospective Review of Three Cases
Parvovirus B19 (PVB19) is a DNA virus which causes clinically relevant infection in renal transplant recipients (RTR) leading to significant morbidity. Manifestations include erythropoietin resistant anemia, proteinuria, and glomerulosclerosis in the allograft. Severe infection may require administration of intravenous immunoglobulin, reduction in immunosuppression and transfusions. The major challenge in managing and preventing the infection in RTR involves the act of balancing the decreased level of immunosuppression and the risk of rejection. The objective of this article is to understand the importance of PVB19 infection and its outcome in RTR. We reviewed the medical records of three RTR with confirmed PVB19 infection and recorded patient information including demographics, clinical and laboratory data, management, and outcome. The average time of occurrence of PVB19 infection as transplant was 8.6 weeks and they presented with symptomatic anemia. Elevated creatinine values were noted in two of them. Following treatment, anemia improved and creatinine values returned to baseline. One of them developed an early relapse and had to be treated once again similarly. We emphasize the importance of maintaining a high index of suspicion for PVB19 infection in patients with anemia in the posttransplant phase, especially in patients on higher doses of immunosuppressants. Early and proper treatment can prevent worsening clinical condition and possible effects on the allograft
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