Plasma sheath effects on ion collection by a pinhole

This work presents tables to assist in the evaluation of pinhole collection effects on spacecraft. These tables summarize results of a computer model which tracks particle trajectories through a simplified electric field in the plasma sheath. A technique is proposed to account for plasma sheath effects in the application of these results and scaling rules are proposed to apply the calculations to specific situations. This model is compared to ion current measurements obtained by another worker, and the agreement is very good

Ion collection from a plasma by a pinhole

Ion focusing by a biased pinhole is studied numerically. Laplace's equation is solved in 3-D for cylindrical symmetry on a constant grid to determine the potential field produced by a biased pinhole in a dielectric material. Focusing factors are studied for ions of uniform incident velocity with a 3-D Maxwellian distribution superimposed. Ion currents to the pinhole are found by particle tracking. The focusing factor of positive ions as a function of initial velocity, temperature, injection radius, and hole size is reported. For a typical Space Station Freedom environment (oxygen ions having a 4.5 eV ram energy, 0.1 eV temperature, and a -140 V biased pinhole), a focusing factor of 13.35 is found for a 1.5 mm radius pinhole

Thermal equilibrium of a macroscopic quantum system in a pure state

We consider the notion of thermal equilibrium for an individual closed macroscopic quantum system in a pure state, i.e., described by a wave function. The macroscopic properties in thermal equilibrium of such a system, determined by its wave function, must be the same as those obtained from thermodynamics, e.g., spatial uniformity of temperature and chemical potential. When this is true we say that the system is in macroscopic thermal equilibrium (MATE). Such a system may however not be in microscopic thermal equilibrium (MITE). The latter requires that the reduced density matrices of small subsystems be close to those obtained from the microcanonical, equivalently the canonical, ensemble for the whole system. The distinction between MITE and MATE is particularly relevant for systems with many-body localization (MBL) for which the energy eigenfunctions fail to be in MITE while necessarily most of them, but not all, are in MATE. We note however that for generic macroscopic systems, including those with MBL, most wave functions in an energy shell are in both MATE and MITE. For a classical macroscopic system, MATE holds for most phase points on the energy surface, but MITE fails to hold for any phase point

Characterization of Alkali Metal Dispensers and Non-Evaporable Getter Pumps in Ultra-High Vacuum Systems for Cold Atomic Sensors

A glass ultrahigh vacuum chamber with rubidium alkali metal dispensers and non-evaporable getter pumps has been developed and used to create a cold atomic sample in a chamber that operates with only passive vacuum pumps. The ion-mass spectrum of evaporated gases from the alkali metal dispenser has been recorded as a function of dispenser current. The efficacy of the non-evaporable getter pumps in promoting and maintaining vacuum has been characterized by observation of the Rb vapor optical absorption on the D2 transition at 780 nm and vacuum chamber pressure rate of rise tests. We have demonstrated a sample of laser-cooled Rb atoms in this chamber when isolated and operating without active vacuum pumps

Soybean Yield Response to Late Soybean Aphid Treatment

Soybean aphids have emerged as a major pest in soybean production in the last four years. This pest was first widely observed in Northwest Iowa in 2002, and in 2003 this pest caused widespread yield loss. In Northwest Iowa the pest reached peak populations later than many models indicated would be likely. Research is needed to better understand what impact late season insecticide applications have on soybean yields when aphid populations are high

Drug Safety and Surveillance: the Case of Avandia

A year ago, a meta-analysis published in The New England Journal of Medicine sounded alarms about the cardiovascular safety of the popular diabetes drug Avandia (rosiglitazone). The study caused both policymakers and the public to question the Food and Drug Administration’s ability to ensure the safety of drugs brought to the marketplace, and evoked memories of Vioxx, the painkiller withdrawn from the market in 2004 because of its link to heart attacks. A year after the Avandia story broke, this Clinical Brief revisits the controversy, summarizes a new study of the cardiovascular safety of diabetes drugs, and analyzes the policy implications for the drug approval process

Location of the Lee-Yang zeros and absence of phase transitions in some Ising spin systems

We consider a class of Ising spin systems on a set \Lambda of sites. The sites are grouped into units with the property that each site belongs to either one or two units, and the total internal energy of the system is the sum of the energies of the individual units, which in turn depend only on the number of up spins in the unit. We show that under suitable conditions on these interactions none of the |\Lambda| Lee-Yang zeros in the complex z = exp{2\beta h} plane, where \beta is the inverse temperature and h the uniform magnetic field, touch the positive real axis, at least for large values of \beta. In some cases one obtains, in an appropriately taken \beta to infinity limit, a gas of hard objects on a set \Lambda'; the fugacity for the limiting system is a rescaling of z and the Lee-Yang zeros of the new partition function also avoid the positive real axis. For certain forms of the energies of the individual units the Lee-Yang zeros of both the finite- and zero-temperature systems lie on the negative real axis for all \beta. One zero-temperature limit of this type, for example, is a monomer-dimer system; our results thus generalize, to finite \beta, a well-known result of Heilmann and Lieb that the Lee-Yang zeros of monomer-dimer systems are real and negative.Comment: Plain TeX. Seventeen pages, five figures from .eps files. Version 2 corrects minor errors in version

CARD11 mediates factor-specific activation of NF-κB by the T cell receptor complex

NF‐κB is a critical target of signaling downstream of the T cell receptor (TCR) complex, but how TCR signaling activates NF‐κB is poorly understood. We have developed an expression cloning strategy that can identify catalytic and noncatalytic molecules that participate in different pathways of NF‐κB activation. Screening of a mouse thymus cDNA library yielded CARD11, a membrane‐associated guanylate kinase (MAGUK) family member containing CARD, PDZ, SH3 and GUK domains. Using a CARD‐deleted variant of CARD11 and RNA interference (RNAi), we demonstrate that CARD11 mediates NF‐κB activation by αCD3/αCD28 cross‐linking and PMA/ionomycin treatment, but not by TNFα or dsRNA. CARD11 is not required for TCR‐mediated induction of NFAT or AP‐1. CARD11 functions upstream of the IκB‐kinase (IKK) complex and cooperates with Bcl10 in a CARD domain‐dependent manner. RNAi‐rescue experiments suggest that the CARD, coiled‐coil, SH3 and GUK domains of CARD11 are critical for its signaling function. These results implicate CARD11 in factor‐ specific activation of NF‐κB by the TCR complex and establish a role for a MAGUK family member in antigen receptor signaling

A Bounded-Size Likelihood Test for Non- Nested Probabilistic Discrete Choice Models Estimated from Choice-Based Samples

Discrete-choice models of the hierarchical logit form enable the analyst to configure tree structures and to investigate the relative statistical and behavioural strengths of alternative hierarchies. The alternative tree structures can be nested or nonnested in a specification sense, and the underlying sample of observations can be exogenous or endogenous. When the sample is endogenous (i.e. choice based) and alternative tree structures are non-nested in a statistically comparative sense, the conventional likelihood ratio tests for comparisons of exogenously sampled nested hierarchical models are not appropriate. This paper presents a bounded-size likelihood ratio test for non-nested discrete choice models estimated from choice-based samples. The tests are presented with and without correction for sample size. We apply the test using a sample of four transport modes for long distance non-business travel in Australia

The effect of weather on respiratory and cardiovascular deaths in 12 U.S. cities.

We carried out time-series analyses in 12 U.S. cities to estimate both the acute effects and the lagged influence of weather on respiratory and cardiovascular disease (CVD) deaths. We fit generalized additive Poisson regressions for each city using nonparametric smooth functions to control for long time trend, season, and barometric pressure. We also controlled for day of the week. We estimated the effect and the lag structure of both temperature and humidity based on a distributed lag model. In cold cities, both high and low temperatures were associated with increased CVD deaths. In general, the effect of cold temperatures persisted for days, whereas the effect of high temperatures was restricted to the day of the death or the day before. For myocardial infarctions (MI), the effect of hot days was twice as large as the cold-day effect, whereas for all CVD deaths the hot-day effect was five times smaller than the cold-day effect. The effect of hot days included some harvesting, because we observed a deficit of deaths a few days later, which we did not observe for the cold-day effect. In hot cities, neither hot nor cold temperatures had much effect on CVD or pneumonia deaths. However, for MI and chronic obstructive pulmonary disease deaths, we observed lagged effects of hot temperatures (lags 4-6 and lags 3 and 4, respectively). We saw no clear pattern for the effect of humidity. In hierarchical models, greater variance of summer and winter temperature was associated with larger effects for hot and cold days, respectively, on respiratory deaths