Quantum efficiency of a microwave photon detector based on a current-biased Josephson junction

We analyze the quantum efficiency of a microwave photon detector based on a current-biased Josephson junction. We consider the Jaynes-Cummings Hamiltonian to describe coupling between the photon field and the junction. We then take into account coupling of the junction and the resonator to the environment. We solve the equation of motion of the density matrix of the resonator-junction system to compute the quantum efficiency of the detector as a function of detection time, bias current, and energy relaxation time. Our results indicate that junctions with modest coherence properties can provide efficient detection of single microwave photons, with quantum efficiency in excess of 80%.Comment: 5 pages, 5 figures, PRB accepted versio

Adapting Livestock Production Systems to Climate Change in Nepal: Challenges and Opportunities

To assess climate change impacts and identify challenges and opportunities for livestock climate change adaption, we conducted a comprehensive study in the Thulokhola watershed of Nuwakot district in Nepal from June 1, 2011 to January 31, 2013. We established nine community livestock groups (CLGs) consisting of 51 members and trained the CLG members in daily livestock record keeping and monitoring surface water quality. Monthly fecal samples from 50 cattle, 50 goats, and 50 buffaloes were collected for the determination of gastrointestinal parasites. Soil and fodder samples were also collected and analyzed. Group discussions, Participatory Rural Appraisals, and full-fledged household survey of 97 households were done. A survey of 41 water sources in the watershed was also conducted. While 85.3 % of the water sources have either dried up or decreased in flow in recent years, drought conditions had great toll on agricultural production. Prevalence rates of helminthes on goats, cattle, and buffalo was 53.8%, 31.32%, and 23.52%, respectively, and animal deaths were remarkably high. Declining pregnancy rates on livestock along with waning supply of fodder and forages and poor soil quality were additional major problems. Although local communities have undertaken several measures including adding new breed, destocking, purchasing fodder and forages, and planting grasses for livestock climate change adaptation, the problems of animal health, breeding conditions, soil fertility, forest degradation, increasing women workload, and water shortages were largely unaddressed. Opportunities for livestock climate change adaptation in Nepal include agroforestry intervention, groundwater utilization, rainwater harvesting, enhancing feed efficiency, and community capacity-building

Hard Exclusive Pion Electroproduction at Backward Angles With CLAS

We report on the first measurement of cross sections for exclusive deeply virtual pion electroproduction off the proton, ep → e\u27nπ+, above the resonance region at backward pion center-of-mass angles. The ϕ∗ π-dependent cross sections were measured, from which we extracted three combinations of structure functions of the proton. Our results are compatible with calculations based on nucleon-to-pion transition distribution amplitudes (TDAs). These non-perturbative objects are defined as matrix elements of threequark-light-cone-operators and characterize partonic correlations with a particular emphasis on baryon charge distribution inside a nucleon

CDK2 limits the highly energetic secretory program of mature β cells by restricting PEP cycle-dependent KATP channel closure.

Hallmarks of mature β cells are restricted proliferation and a highly energetic secretory state. Paradoxically, cyclin-dependent kinase 2 (CDK2) is synthesized throughout adulthood, its cytosolic localization raising the likelihood of cell cycle-independent functions. In the absence of any changes in β cell mass, maturity, or proliferation, genetic deletion of Cdk2 in adult β cells enhanced insulin secretion from isolated islets and improved glucose tolerance in vivo. At the single β cell level, CDK2 restricts insulin secretion by increasing KATP conductance, raising the set point for membrane depolarization in response to activation of the phosphoenolpyruvate (PEP) cycle with mitochondrial fuels. In parallel with reduced β cell recruitment, CDK2 restricts oxidative glucose metabolism while promoting glucose-dependent amplification of insulin secretion. This study provides evidence of essential, non-canonical functions of CDK2 in the secretory pathways of quiescent β cells

Impact of Fatty-Acid Labeling of Bacillus subtilis Membranes on the Cellular Lipidome and Proteome

Developing cultivation methods that yield chemically and isotopically defined fatty acid (FA) compositions within bacterial cytoplasmic membranes establishes an in vivo experimental platform to study membrane biophysics and cell membrane regulation using novel approaches. Yet before fully realizing the potential of this method, it is prudent to understand the systemic changes in cells induced by the labeling procedure itself. In this work, analysis of cellular membrane compositions was paired with proteomics to assess how the proteome changes in response to the directed incorporation of exogenous FAs into the membrane of Bacillus subtilis. Key findings from this analysis include an alteration in lipid headgroup distribution, with an increase in phosphatidylglycerol lipids and decrease in phosphatidylethanolamine lipids, possibly providing a fluidizing effect on the cell membrane in response to the induced change in membrane composition. Changes in the abundance of enzymes involved in FA biosynthesis and degradation are observed; along with changes in abundance of cell wall enzymes and isoprenoid lipid production. The observed changes may influence membrane organization, and indeed the well-known lipid raft-associated protein flotillin was found to be substantially down-regulated in the labeled cells – as was the actin-like protein MreB. Taken as a whole, this study provides a greater depth of understanding for this important cell membrane experimental platform and presents a number of new connections to be explored in regard to modulating cell membrane FA composition and its effects on lipid headgroup and raft/cytoskeletal associated proteins

Nonlinear thermoelectric response of quantum dots: renormalized dual fermions out of equilibrium

The thermoelectric transport properties of nanostructured devices continue to attract attention from theorists and experimentalist alike as the spatial confinement allows for a controlled approach to transport properties of correlated matter. Most of the existing work, however, focuses on thermoelectric transport in the linear regime despite the fact that the nonlinear conductance of correlated quantum dots has been studied in some detail throughout the last decade. Here, we review our recent work on the effect of particle-hole asymmetry on the nonlinear transport properties in the vicinity of the strong coupling limit of Kondo-correlated quantum dots and extend the underlying method, a renormalized superperturbation theory on the Keldysh contour, to the thermal conductance in the nonlinear regime. We determine the charge, energy, and heat current through the nanostructure and study the nonlinear transport coefficients, the entropy production, and the fate of the Wiedemann-Franz law in the non-thermal steady-state. Our approach is based on a renormalized perturbation theory in terms of dual fermions around the particle-hole symmetric strong-coupling limit.Comment: chapter contributed to 'New Materials for Thermoelectric Applications: Theory and Experiment' Springer Series: NATO Science for Peace and Security Series - B: Physics and Biophysics, Veljko Zlatic (Editor), Alex Hewson (Editor). ISBN: 978-9400749863 (2012

Exploring the Structure of the Bound Proton With Deeply Virtual Compton Scattering

In the past two decades, deeply virtual Compton scattering of electrons has been successfully used to advance our knowledge of the partonic structure of the free proton and investigate correlations between the transverse position and the longitudinal momentum of quarks inside the nucleon. Meanwhile, the structure of bound nucleons in nuclei has been studied in inclusive deep-inelastic lepton scattering experiments off nuclear targets, showing a significant difference in longitudinal momentum distribution of quarks inside the bound nucleon, known as the EMC effect. In this Letter, we report the first beam spin asymmetry (BSA) measurement of exclusive deeply virtual Compton scattering off a proton bound in 4He. The data used here were accumulated using a 6 GeV longitudinally polarized electron beam incident on a pressurized 4He gaseous target placed within the CLAS spectrometer in Hall-B at the Thomas Jefferson National Accelerator Facility. The azimuthal angle (ϕ) dependence of the BSA was studied in a wide range of virtual photon and scattered proton kinematics. The Q², xB, and t dependencies of the BSA on the bound proton are compared with those on the free proton. In the whole kinematical region of our measurements, the BSA on the bound proton is smaller by 20% to 40%, indicating possible medium modification of its partonic structure

Results from the Super Cryogenic Dark Matter Search (SuperCDMS) experiment at Soudan

We report the result of a blinded search for Weakly Interacting Massive Particles (WIMPs) using the majority of the SuperCDMS Soudan dataset. With an exposure of 1690 kg days, a single candidate event is observed, consistent with expected backgrounds. This analysis (combined with previous Ge results) sets an upper limit on the spin-independent WIMP--nucleon cross section of $1.4 \times 10^{-44}$ ($1.0 \times 10^{-44}$) cm$^2$ at 46 GeV/$c^2$. These results set the strongest limits for WIMP--germanium-nucleus interactions for masses $>$12 GeV/$c^2$

The economic burden of HIV/AIDS on individuals and households in Nepal: a quantitative study.

BACKGROUND: There have been only limited studies assessing the economic burden of HIV/AIDS in terms of direct costs, and there has been no published study related to productivity costs in Nepal. Therefore, this study explores in detail the economic burden of HIV/AIDS, including direct costs and productivity costs. This paper focuses on the direct costs of seeking treatment, productivity costs, and related factors affecting direct costs, and productivity costs. METHODS: This study was a cross-sectional, quantitative study. The primary data were collected through a structured face-to-face survey from 415 people living with HIV/AIDS (PLHIV). The study was conducted in six representative treatment centres of six districts of Nepal. The data analysis regarding the economic burden (direct costs and productivity costs) was performed from the household's perspective. Descriptive statistics have been used, and regression analyses were applied to examine the extent, nature and determinants of the burden of the disease, and its correlations. RESULTS: Average total costs due to HIV/AIDS (the sum of average total direct and average productivity costs before adjustment for coping strategies) were Nepalese Rupees (NRs) 2233 per month (US$30.2/month), which was 28.5$ 20.4), and average productivity costs (before adjustment for coping strategies) were NRs 721 (US$ 9.7). The average monthly productivity losses (before adjustment for coping strategies) were 5.05 days per person. The major determinants for the direct costs were household income, occupation, health status of respondents, respondents accompanied or not, and study district. Health status of respondents, ethnicity, sexual orientation and study district were important determinants for productivity costs. CONCLUSIONS: The study concluded that HIV/AIDS has caused a significant economic burden for PLHIV and their families in Nepal. The study has a number of policy implications for different stakeholders. Provision of social support and income generating programmes to HIV-affected individuals and their families, and decentralising treatment services in each district seem to be viable solutions to reduce the economic burden of HIV-affected individuals and households