Coupling of hydrodynamics and quasiparticle motion in collective modes of superfluid trapped Fermi gases

At finite temperature, the hydrodynamic collective modes of superfluid trapped Fermi gases are coupled to the motion of the normal component, which in the BCS limit behaves like a collisionless normal Fermi gas. The coupling between the superfluid and the normal components is treated in the framework of a semiclassical transport theory for the quasiparticle distribution function, combined with a hydrodynamic equation for the collective motion of the superfluid component. We develop a numerical test-particle method for solving these equations in the linear response regime. As a first application we study the temperature dependence of the collective quadrupole mode of a Fermi gas in a spherical trap. The coupling between the superfluid collective motion and the quasiparticles leads to a rather strong damping of the hydrodynamic mode already at very low temperatures. At higher temperatures the spectrum has a two-peak structure, the second peak corresponding to the quadrupole mode in the normal phase.Comment: 14 pages; v2: major changes (effect of Hartree field included

Dynamics of a trapped Fermi gas in the BCS phase

We derive semiclassical transport equations for a trapped atomic Fermi gas in the BCS phase at temperatures between zero and the superfluid transition temperature. These equations interpolate between the two well-known limiting cases of superfluid hydrodynamics at zero temperature and the Vlasov equation at the critical one. The linearized version of these equations, valid for small deviations from equilibrium, is worked out and applied to two simple examples where analytical solutions can be found: a sound wave in a uniform medium and the quadrupole excitation in a spherical harmonic trap. In spite of some simplifying approximations, the main qualitative results of quantum mechanical calculations are reproduced, which are the different frequencies of the quadrupole mode at zero and the critical temperature and strong Landau damping at intermediate temperatures. In addition we suggest a numerical method for solving the semiclassical equations without further approximations.Comment: 15 pages, 4 figures; v2: discussion and references adde

Defining Tucker Act Jurisdiction After Bowen v. Massachusetts

Part I of this Article summarizes the relevant provisions of the Tucker Act, and examines courts\u27 interpretations of whether a district court had jurisdiction over a claim when a potential judgment exceeded $10,000. This Article suggests that, over time, traditional Tucker Act jurisdiction has been distorted by the appearance of a new kind of plaintiff\u27 seeking structural reform rather than the kinds of compensation envisioned by the Act. This Article also suggests that Tucker Act jurisdiction has been distorted by two congressional actions: the creation of the judgment fund; and amendments to the Administrative Procedure Act. These congressional actions could be construed to extend district court jurisdiction over claims for money damages. As a result, the distinction between Tucker and non- Tucker Act remedies has been blurred. Part II of this Article explicates the case law before and after the passage of the APA and its relevant amendments. This Article notes how, in the 1980\u27s, the Department of Justice (DOJ) began to assert that state suits against the Federal Government seeking reimbursement of grant-in-aid funds should be treated as Tucker Act claims and tried in the United States Claims Court, rather than as non-Tucker Act claims to be tried in the district courts. Although the DOJ achieved some measure of success, Judge Bork, in a masterful display of judicial legerdemain, offered alternative reasoning which became the basis for the Bowen decision. This alternative was superficially attractive but intrinsically false and created the impression that Bowen had diminished the traditional jurisdiction of the Claims Court and Court of Appeals for the Federal Circuit. Part III discusses and analyzes the Bowen case, outlining its procedural history, and highlighting the United States Supreme Court\u27s efforts to distinguish Bowen from the run of the mill Tucker Act suits. In part IV, this Article offers alternative interpretations of the Bowen ruling. Finally, part V of this Article advances the preferred solution and suggests how the Bowen decision can be reconciled with a century of case law, thereby avoiding the kind of judicial nihilism evidenced in this Article\u27s introductory quotation

Genomics in medicine : from promise to practice

CITATION: Urban, M. F. 2015. Genomics in medicine : from promise to practice. South African Medical Journal, 105(7):545-547, doi:10.7196/SAMJnew.7894.The original publication is available at http://www.samj.org.zaGenomics is a complex field that is taking an increasing role in many aspects of healthcare. Genomic medicine is expected to transition into the broader paradigm of precision medicine, with profound long-term implications for the practice of medicine and the training of future practitioners.http://www.samj.org.za/index.php/samj/article/view/10067Publisher's versio

Erwartungsbildung über den Wahlausgang und ihr Einfluss auf die Wahlentscheidung

Expectations about the outcome of elections play an important role in both rational choice and social psychological theories of voting. So far, however, there is not much research on the formation of expectations and their influence on voting behavior. In this paper, we use election studies from Belgium, Austria, and Germany to address several questions about the formation and effects of expectations. First, we investigate the quality of the overall expectations and identify several factors that systematically influence the formation of expectations. In a second step, we turn to individual expectations for parties and coalitions and find a moderate bias in favor of preferred parties and coalitions. We show that the effect of wishful thinking decreases with higher levels of political knowledge and education. Finally, we test two different mechanisms how expectations can affect voting behavior, the rational decision of strategic coalition voting to avoid casting a wasted vote and the social psychological bandwagon effect. Both effects are supported and political knowledge appears to be a crucial moderator between these two mechanisms.

Optical and Ionospheric Phenomena at EISCAT under continuous X-mode HF pumping

We present experimental results from multiinstrument observations in the high-latitude ionospheric F2 layer at the EISCAT (European Incoherent Scatter Scientific Association) heating facility. The results come from a set of experiments, when an X-polarized HF pump wave at high heater frequencies (fH > 6.0 MHz) was injected into the F region of the ionosphere toward the magnetic zenith. Experiments were carried out under quiet magnetic conditions with an effective radiated power of 458–548 MW. HF pumping was produced at different heater frequencies, away from electron gyroharmonic frequencies, and different durations of heater pulses. We show the first experimental evidence of the excitation of artificial optical emissions at red (630 nm) and green (557.7 nm) lines in the high-latitude ionospheric F2 layer induced by an X-polarized HF pump wave. Intensities at red and green lines varied in the range 110–950 R and 50–350 R, respectively, with a ratio of green to red line of 0.35–0.5. The results of optical observations are compared with behaviors of the HF-enhanced ion and plasma lines from EISCAT UHF incoherent scatter radar data and small-scale field-aligned artificial irregularities from Cooperative UK Twin Located Auroral Sounding System observations. It was found that the X-mode radio-induced optical emissions coexisted with HF-enhanced ion and plasma lines and strong artificial field-aligned irregularities throughout the whole heater pulse. It is indicative that parametric decay or oscillating two-stream instabilities were not quenched by fully established small-scale field-aligned artificial irregularities excited by an X-mode HF pump wave

Amphiphilic block copolymers as stabilizers in emulsion polymerization: Effects of molecular weight dispersity and evidence of self-folding behavior

Emulsion polymerizations, used to produce many commodity materials, require stabilizing agents to prevent phase separation. Incorporation of these stabilizers in the final polymer may have negative effects on product properties, so the design of new stabilizers is being actively pursued. Amphiphilic diblock copolymers are a promising type of emulsion polymerization stabilizer and are the focus of this work (Fig. 1). First, the tolerance of an amphiphilic diblock copolymer stabilizer’s performance to high molecular weight dispersity and homopolymer impurity has been investigated. Polystyrene-b-poly(acrylic acid) block copolymers were studied due to their previously demonstrated efficacy as stabilizers in emulsion polymerization, and their similarity to commercially important polystyrene-r-poly(acrylic acid) stabilizers. Neither greater molecular weight dispersity nor homopolymer impurity was found to negatively impact the stabilization performance of these block copolymers, suggesting that the economically unfavorable conditions required to achieve low molecular weight dispersity and homopolymer impurity may be avoided. We then examined novel polystyrene-b-[polystyrene-r-poly(acrylic acid)] block-random copolymers which were shown to stabilize emulsion polymerizations with up to 50 weight percent solids content, exceeding what was possible using the polystyrene-b-poly(acrylic acid) block copolymers. Of even greater significance and scientific value is that the block-random copolymers were also observed to have unusual solution behavior, self-folding rather than self-assembling, to give single chain nanoparticles. Emulsion polymerizations stabilized by these block-random copolymers had a total particle surface area which was directly proportional to the stabilizer concentration and was unaffected by polymerization kinetics. A novel “seeded-coagulative” emulsion polymerization mechanism has been proposed to explain these results, which were unexplainable by any known emulsion polymerization mechanism. Please click Additional Files below to see the full abstrac

Efavirenz use during pregnancy and for women of child-bearing potential

BACKGROUND: Efavirenz is the preferred non-nucleoside reverse transcriptase inhibitor for first-line antiretroviral treatment in many countries. For women of childbearing potential, advantages of efavirenz are balanced by concerns that it is teratogenic. This paper reviews evidence of efavirenz teratogenicity and considers implications in common clinical scenarios. FINDINGS: Concerns of efavirenz-induced fetal effects stem from animal studies, although the predictive value of animal data for humans is unknown. Four retrospective cases of central nervous system birth defects in infants with first trimester exposure to efavirenz have been interpreted as being consistent with animal data. In a prospective pregnancy registry, which is subject to fewer potential biases, no increase was detected in overall risk of birth defects following exposure to efavirenz in the first-trimester. DISCUSSION: For women planning a pregnancy or not using contraception, efavirenz should be avoided if alternatives are available. According to WHO guidelines for resource-constrained settings, benefits of efavirenz are likely to outweigh risks for women using contraception. Women who become pregnant while receiving efavirenz often consider drug substitution or temporarily suspending treatment. Both options have substantial risks for maternal and fetal health which, we argue, appear unjustified after the critical period of organogenesis (3–8 weeks post-conception). Efavirenz-based triple regimens, initiated after the first trimester of pregnancy and discontinued after childbirth, are potentially an important alternative for reducing mother-to-child transmission in pregnant women who do not yet require antiretroviral treatment. CONCLUSION: Current recommendations for care for women who become pregnant while receiving efavirenz may need to be re-considered, particularly in settings with limited alternative drugs and laboratory monitoring. With current data limitations, additional adequately powered prospective studies are needed