Traps and Thresholds in Pastoralist Mobility

Replaced with revised version of paper 07/22/10.Asset poverty traps, Pastoralism, Semiparametric estimation, International Development, Livestock Production/Industries, O12, Q12, O13, C50,

Economics of Pollution Trading for SO2 and NOx

For years economists have urged policymakers to use market-based approaches such as cap-and-trade programs or emission taxes to control pollution. The SO2 allowance market created by Title IV of the 1990 U.S. Clean Air Act Amendments represents the first real test of the wisdom of economists’ advice. Subsequent urban and regional applications of NOx emission allowance trading took shape in the 1990s in the United States, culminating in a second large experiment in emission trading in the eastern United States that began in 2003. This paper provides an overview of the economic rationale for emission trading and a description of the major U.S. programs for sulfur dioxide (SO2) and nitrogen oxides (NOx). We evaluate these programs along measures of performance including cost savings, environmental integrity, and incentives for technological innovation. We offer lessons for the design of future programs including, most importantly, those reducing carbon dioxide.sulfur dioxide, nitrogen oxides, emission trading, power plants, air pollution

Enhancing Services for Homeless Populations: Impact of a Virtual-Reality Training Tool on Health Professional Students’ Self-Efficacy in Working with Homeless Populations

INTRODUCTION Despite the rising prevalence and unmet healthcare needs of homeless populations, most healthcare providers do not receive specific training on working with this population. The growth of simulation-based technology in the medical classroom offers new opportunities for such training. Virtual-reality tools have been shown to facilitate learning and minimize restraints such as time and travel. The Enhancing Service to Homeless Populations (ESHP) program was designed to provide health professions students at Thomas Jefferson University with training on how to interact with homeless populations using an interprofessional virtual-reality setting, with the ultimate goal of improving students’ self-efficacy. METHODS Participants (n=15) were students recruited from Thomas Jefferson University from the nursing, medicine, occupational therapy and public health schools. Participants were placed into groups in which they simulated visits with homeless clients on the virtual world platform Second Life. Confidence levels and knowledge of the participants were elicited in surveys and structured interviews before and after participation in the simulations. Survey results were analyzed with descriptive statistics. Interviews were transcribed and qualitative analysis was done using NVivo software. RESULTS Preliminary analysis of survey data demonstrates an increase in self-efficacy after participation. Codebook development for the qualitative analysis is underway but results remain incomplete. CONCLUSION The ESHP program was found to increase students’ self-efficacy in interacting with homeless populations but more data must be analyzed before we can elaborate upon these findings

Facile Self-Assembly of Quantum Plasmonic Circuit Components

Efficient coupling between solid state quantum emitters and plasmonic waveguides is important for the realization of integrated circuits for quantum information, communication and sensing. However, realization of plasmonic circuits is still scarce, particularly due to challenges associated with accurate positioning of quantum emitters near plasmonic resonators. Current pathways for the construction of plasmonic circuits involve cumbersome and costly methods such as scanning atomic force microscopy or mechanical manipulation, where individual elements are physically relocated using the scanning tip. Here, we introduce a simple, fast and cost effective chemical self-assembly method for the attachment of two primary components of a practical plasmonic circuit: a single photon emitter and a waveguide. Our method enables coupling of nanodiamonds with a single quantum emitter (the nitrogen-vacancy (NV) center) onto the terminal of a silver nanowire, by simply varying the concentration of ascorbic acid (AA) in a reaction solution. The AA concentration is used to control the extent of agglomeration, and can be optimised so as to cause preferential, selective activation of the tips of the nanowires. The nanowire-nanodiamond structures show efficient plasmonic coupling of fluorescence emission from single NV centers into surface plasmon polariton (SPP) modes, evidenced by a more than two-fold reduction in fluorescence lifetime and an increase in fluorescence intensity.Comment: Published in Advanced Materials on 2 June 201

Spa47 is an oligomerization-activated type three secretion system (T3SS) ATPase from \u3cem\u3eShigella flexneri\u3c/em\u3e

Gram-negative pathogens often use conserved type three secretion systems (T3SS) for virulence. The Shigella type three secretion apparatus (T3SA) penetrates the host cell membrane and provides a unidirectional conduit for injection of effectors into host cells. The protein Spa47 localizes to the base of the apparatus and is speculated to be an ATPase that provides the energy for T3SA formation and secretion. Here, we developed an expression and purification protocol, producing active Spa47 and providing the first direct evidence that Spa47 is a bona fide ATPase. Additionally, size exclusion chromatography and analytical ultracentrifugation identified multiple oligomeric species of Spa47 with the largest greater than 8 fold more active for ATP hydrolysis than the monomer. An ATPase inactive Spa47 point mutant was then engineered by targeting a conserved Lysine within the predicted Walker A motif of Spa47. Interestingly, the mutant maintained a similar oligomerization pattern as active Spa47, but was unable to restore invasion phenotype when used to complement a spa47 null S. flexneri strain. Together, these results identify Spa47 as a Shigella T3SS ATPase and suggest that its activity is linked to oligomerization, perhaps as a regulatory mechanism as seen in some related pathogens. Additionally, Spa47 catalyzed ATP hydrolysis appears to be essential for host cell invasion, providing a strong platform for additional studies dissecting its role in virulence and providing an attractive target for anti-infective agents

Formation and Evolution of the Large‐Scale Magnetic Fields in Venus’ Ionosphere: Results From a Three Dimensional Global Multispecies MHD Model

Large‐scale magnetic fields have been observed in Venus’ ionosphere by both the Pioneer Venus Orbiter (PVO) and Venus Express spacecraft. In this study, we examine the formation and evolution of the large‐scale magnetic field in the Venus ionosphere using a sophisticated global multispecies Magnetohydrodynamics (MHD) model that has been developed for Venus (Ma et al., 2013, https://doi.org/10.1029/2012JA018265). A time‐dependent model run is performed under varying solar wind dynamic pressure. Based on model results, we find that (1) the initial response of the induced magnetosphere is fast (~min), (2) a large‐scale magnetic field gradually forms in the ionosphere when the solar wind dynamic pressure suddenly exceeds the ionospheric thermal pressure, (3) both the penetration and decay of the large‐scale magnetic field in the ionosphere are slow (~hr), and (4) the ion escape rate has a nonlinear response to the change of solar wind dynamic pressure.Plain language SummaryLarge‐scale magnetic fields have been observed at Venus’ ionosphere by previous Venus missions. In this study, we examine the formation and evolution of the large‐scale magnetic field in the Venus ionosphere using a sophisticated global model. A time‐dependent model run is performed under varying solar wind dynamic pressure (density). Model results show that the outside interaction region responds quickly (~min) to the solar wind variation, while the response time of the ionosphere is long (~hr). We also found that the ion escape rate has a nonlinear response to the change of solar wind dynamic pressure.Key PointsThe global MHD model self‐consistently reproduces the formation and evolution of the large‐scale magnetic fields in the Venus ionosphereModel results show that it takes quite long time (~hr) for the magnetic field to penetrate into and decay in the ionosphereThe large‐scale magnetic fields in the ionosphere act as an additional obstacle to the solar windPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155482/1/grl60596.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155482/2/grl60596_am.pd

Martian ionospheric responses to dynamic pressure enhancements in the solar wind

As a weakly magnetized planet, Mars ionosphere/atmosphere interacts directly with the shocked solar wind plasma flow. Even though many numerical studies have been successful in reproducing numerous features of the interaction process, these earlier studies focused mainly on interaction under steady solar wind conditions. Recent observations suggest that plasma escape fluxes are significantly enhanced in response to solar wind dynamic pressure pulses. In this study, we focus on the response of the ionosphere to pressure enhancements in the solar wind. Through modeling of two idealized events using a magnetohydrodynamics model, we find that the upper ionosphere of Mars responds almost instantaneously to solar wind pressure enhancements, while the collision dominated lower ionosphere (below ~150 km) does not have noticeable changes in density. We also find that ionospheric perturbations in density, magnetic field, and velocity can last more than an hour after the solar wind returns to the quiet conditions. The topside ionosphere forms complicated transient shapes in response, which may explain unexpected ionospheric behaviors in recent observations. We also find that ionospheric escape fluxes do not correlate directly with simultaneous solar wind dynamic pressure. Rather, their intensities also depend on the earlier solar wind conditions. It takes a few hours for the ionospheric/atmospheric system to reach a new quasi‐equilibrium state. Key Points This paper studies ionospheric responses to solar wind pressure enhancements The ionosphere forms complicated transient shapes when solar wind varies The escape fluxes depend on both simultaneous and earlier solar wind conditionsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106668/1/jgra50802.pd