A study of the electronic properties of liquid alkali metals. A self--consistent approach

We study the electronic properties (density of states, conductivity and thermopower) of some nearly--free--electron systems: the liquid alkali metals and two liquid alloys, Li-Na and Na-K. The study has been performed within the self-consistent second order Renormalized Propagator Perturbation Expansion (RPE) for the self-energy. The input ionic pseudopotentials and static correlation functions are derived from the neutral pseudoatom method and the modified hypernetted chain theory of liquids, respectively. Reasonable agreement with experiment is found for Na, K, Rb and Na-K, whereas for Li and Cs and Li-Na the agreement is less satisfactoryComment: 14 pages, Latex, 1 figure, 1 tabl

Leaching of nitroso rubber material removes uncured polymer

New leaching process removes uncured polymer from nitroso rubber, elastomer used in presence of nitrogen tetroxide. Uncured portion is removed by controlled soaking of polymer slab in Freon TF. Leaching with Freon TF prevents nitroso rubber from adhering to adjoining surfaces and limiting its usefulness in either static or dynamic applications

Flight Path and Mission Strategies to Satisfy Outer Planet Quarantine Constraints

Analysis of typical Jupiter-Saturn-Pluto trajectory to determine characteristics of outer planet space missions and planetary quarantine constraint

Development and Sex Ratio of \u3ci\u3eMelittobia Australica\u3c/i\u3e and \u3ci\u3eM. Digitata\u3c/i\u3e (Hymenoptera: Eulophidae) on \u3ci\u3eMegachile Rotundata\u3c/i\u3e (Hymenoptera: Megachilidae) and \u3ci\u3eTrypoxylon Politum\u3c/i\u3e (Hymenoptera: Sphecidae)

Life history, development time, and sex ratio of Melittobia australica Girault and M. digitata Dahms on Megachile rotundata (Fabricius) and Trypoxylon politum Say are presented and compared with previous reports. Total development time and sex ratio differs slightly among the different hosts but falls within the expected range reported for different hosts and Melittobia species. The slightly longer development times and higher proportion of males recorded for both species on M. rotundata hosts probably reflects poorer host nutritional quality, relative to T. politum. We confirm that the one unusually extended development time reported by Schmieder for Melittobia chalybii Ashmead collected in New Jersey, can be accounted for as likely having represented a previously unknown species since described as M. femorata Dahms

Parent Stars of Extrasolar Planets. XI. Trends with Condensation Temperature Revisited

We report the results of abundance analyses of new samples of stars with planets and stars without detected planets. We employ these data to compare abundance-condensation temperature trends in both samples. We find that stars with planets have more negative trends. In addition, the more metal-rich stars with planets display the most negative trends. These results confirm and extend the findings of Ramirez et al. (2009) and Melendez et al. (2009), who restricted their studies to solar analogs. We also show that the differences between the solar photospheric and CI meteoritic abundances correlate with condensation temperature.Comment: 7 pages, 11 figures; to be published in MNRA

A coral reef as an analogical model to promote collaborative learning on cultural and ethnic diversity in science

An exercise designed to engage students in critical thinking and active conversation about gender, diversity, and ethnicity in science is described. First semester college science students frequently do not realize that individual scholarship is an integral component of global scholarship and that scientific progress stems from the scholarly contributions of numerous individuals. The described exercise initially uses a collage of a coral reef—chosen both for its visual impact and because it is an excellent model of diversity—highlighting various aspects of life on a reef. This is followed by a trawl of library resources to enable the development of a chronology of significant contributions and practices in the field of medicine and the identification of historical and contemporary scholars and practitioners by race, cultural heritage, and gender

Collisionless reconnection: The sub-microscale mechanism of magnetic field line interaction

Magnetic field lines are quantum objects carrying one quantum $\Phi_0=2\pi\hbar/e$ of magnetic flux and have finite radius $\lambda_m$. Here we argue that they possess a very specific dynamical interaction. Parallel field lines reject each other. When confined to a certain area they form two-dimensional lattices of hexagonal structure. We estimate the filling factor of such an area. Antiparallel field lines, on the other hand, attract each other. We identify the physical mechanism as being due to the action of the gauge potential field which we determine quantum mechanically for two parallel and two antiparallel field lines. The distortion of the quantum electrodynamic vacuum causes a cloud of virtual pairs. We calculate the virtual pair production rate from quantum electrodynamics and estimate the virtual pair cloud density, pair current and Lorentz force density acting on the field lines via the pair cloud. These properties of field line dynamics become important in collisionless reconnection, consistently explaining why and how reconnection can spontaneously set on in the field-free centre of a current sheet below the electron-inertial scale.Comment: 13 journal pages, 6 figures, submitted to Ann. Geophy

Efficient posterior simulation in cointegration models with priors on the cointegration space

A message coming out of the recent Bayesian literature on cointegration is that it is important to elicit a prior on the space spanned by the cointegrating vectors (as opposed to a particular identi…ed choice for these vectors). In this note, we discuss a sensible way of eliciting such a prior. Furthermore, we develop a collapsed Gibbs sampling algorithm to carry out e¢ cient posterior simulation in cointegration models. The computational advantages of our algorithm are most pronounced with our model, since the form of our prior precludes simple posterior simulation using conventional methods (e.g. a Gibbs sampler involves non-standard posterior conditionals). However, the theory we draw upon implies our algorithm will be more e¢ cient even than the posterior simulation methods which are used with identi…ed versions of cointegration models

Bayesian inference in the time varying cointegration model

There are both theoretical and empirical reasons for believing that the parameters of macroeconomic models may vary over time. However, work with time-varying parameter models has largely involved Vector autoregressions (VARs), ignoring cointegration. This is despite the fact that cointegration plays an important role in informing macroeconomists on a range of issues. In this paper we develop time varying parameter models which permit coin- tegration. Time-varying parameter VARs (TVP-VARs) typically use state space representations to model the evolution of parameters. In this paper, we show that it is not sensible to use straightforward extensions of TVP-VARs when allowing for cointegration. Instead we develop a speci…cation which allows for the cointegrating space to evolve over time in a manner comparable to the random walk variation used with TVP-VARs. The properties of our approach are investigated before developing a method of posterior simulation. We use our methods in an empirical investigation involving a permanent/transitory variance decomposition for inflation