Properties of 1D two-barrier quantum pump with harmonically oscillating barriers

We study a one-dimensional quantum pump composed of two oscillating delta-functional barriers. The linear and non-linear regimes are considered. The harmonic signal applied to any or both barriers causes the stationary current. The direction and value of the current depend on the frequency, distance between barriers, value of stationary and oscillating parts of barrier potential and the phase shift between alternating voltages.Comment: 7 pages, 8 figure

Hypospadias and endocrine disruption: is there a connection?

Hypospadias is one of the most common congenital anomalies in the United States, occurring in approximately 1 in 250 newborns or roughly 1 in 125 live male births. It is the result of arrested development of the urethra, foreskin, and ventral surface of the penis where the urethral opening may be anywhere along the shaft, within the scrotum, or in the perineum. The only treatment is surgery. Thus, prevention is imperative. To accomplish this, it is necessary to determine the etiology of hypospadias, the majority of which have been classified as idiopathic. In this paper we briefly describe the normal development of the male external genitalia and review the prevalence, etiology, risk factors, and epidemiology of hypospadias. The majority of hypospadias are believed to have a multifactorial etiology, although a small percentage do result from single gene mutations. Recent findings suggest that some hypospadias could be the result of disrupted gene expression. Discoveries about the antiandrogenic mechanisms of action of some contemporary-use chemicals have provided new knowledge about the organization and development of the urogenital system and may provide additional insight into the etiology of hypospadias and direction for prevention

NEEMO - NASA's Extreme Environment Mission Operations: On to a NEO

During NEEMO missions, a crew of six Aquanauts lives aboard the National Oceanic and Atmospheric Administration (NOAA) Aquarius Underwater Laboratory the world's only undersea laboratory located 5.6 km off shore from Key Largo, Florida. The Aquarius habitat is anchored 62 feet deep on Conch Reef which is a research only zone for coral reef monitoring in the Florida Keys National Marine Sanctuary. The crew lives in saturation for a week to ten days and conducts a variety of undersea EVAs (Extra Vehicular Activities) to test a suite of long-duration spaceflight Engineering, Biomedical, and Geoscience objectives. The crew also tests concepts for future lunar exploration using advanced navigation and communication equipment in support of the Constellation Program planetary exploration analog studies. The Astromaterials Research and Exploration Science (ARES) Directorate and Behavioral Health and Performance (BHP) at NASA/Johnson Space Center (JSC), Houston, Texas support this effort to produce a high-fidelity test-bed for studies of human planetary exploration in extreme environments as well as to develop and test the synergy between human and robotic curation protocols including sample collection, documentation, and sample handling. The geoscience objectives for NEEMO missions reflect the requirements for Lunar Surface Science outlined by the LEAG (Lunar Exploration Analysis Group) and CAPTEM (Curation and Analysis Planning Team for Extraterrestrial Materials) white paper [1]. The BHP objectives are to investigate best meas-ures and tools for assessing decrements in cogni-tive function due to fatigue, test the feasibility study examined how teams perform and interact across two levels, use NEEMO as a testbed for the development, deployment, and evaluation of a scheduling and planning tool. A suite of Space Life Sciences studies are accomplished as well, ranging from behavioral health and performance to immunology, nutrition, and EVA suit design results of which will directly support the investigation of open questions and operational concepts that will enable NASA to continue its plan for planetary exploration

Two regimes for effects of surface disorder on the zero-bias conductance peak of tunnel junctions involving d-wave superconductors

Impurity-induced quasiparticle bound states on a pair-breaking surface of a d-wave superconductor are theoretically described, taking into account hybridization of impurity- and surface-induced Andreev states. Further a theory for effects of surface disorder (of thin impurity surface layer) on the low-bias conductance of tunnel junctions is developed. We find a threshold $n_c$ for surface impurity concentration $n_S$, which separates the two regimes for surface impurity effects on the zero-bias conductance peak (ZBCP). Below the threshold, surface impurities do not broaden the ZBCP, but effectively reduce its weight and generate impurity bands. For low $n_S$ impurity bands can be, in principle, resolved experimentally, being centered at energies of bound states induced by an isolated impurity on the surface. For larger $n_S$ impurity bands are distorted, move to lower energies and, beginning with the threshold concentration $n_S=n_c$, become centered at zero energy. With increasing $n_S$ above the threshold, the ZBCP is quickly destroyed in the case of strong scatterers, while it is gradually suppressed and broaden in the presence of weak impurity potentials. More realistic cases, taking into account additional broadening, not related to the surface disorder, are also considered.Comment: 9 pages, 7 figure

Conductivity of 2D many-component electron gas, partially-quantized by magnetic field

The 2D semimetal consisting of heavy holes and light electrons is studied. The consideration is based on assumption that electrons are quantized by magnetic field while holes remain classical. We assume also that the interaction between components is weak and the conversion between components is absent. The kinetic equation for holes colliding with quantized electrons is utilized. It has been stated that the inter-component friction and corresponding correction to the dissipative conductivity $\sigma_{xx}$ {\it do not vanish at zero temperature} due to degeneracy of the Landau levels. This correction arises when the Fermi level crosses the Landau level. The limits of kinetic equation applicability were found. We also study the situation of kinetic memory when particles repeatedly return to the points of their meeting.Comment: 13 pages, 1 figur

Photocurrent in nanostructures with asymmetric antidots

The steady current induced by electromagnetic field in a 2D system with asymmetric scatterers is studied. The scatterers are assumed to be oriented cuts with one diffusive and another specular sides. Besides, the existence of isotropic impurity scatterers is assumed. This simple model simulates the lattice of half-disk which have been studied numerically recently. The model allows the exact solution in the framework of the kinetic equation. The static current response in the second order of electric field is obtained. The photogalvanic tensor contains both responses to linear and circular polarization of electromagnetic field. The model possesses non-analyticity with regards to the rate of impurity scattering.Comment: 9 pages, 6 figure

On the effect of far impurities on the density of states of two-dimensional electron gas in a strong magnetic field

The effect of impurities situated at different distances from a two-dimensional electron gas on the density of states in a strong magnetic field is analyzed. Based on the exact result of Brezin, Gross, and Itzykson, we calculate the density of states in the whole energy range, assuming the Poisson distribution of impurities in the bulk. It is shown that in the case of small impurity concentration the density of states is qualitatively different from the model case when all impurities are located in the plane of the two-dimensional electron gas.Comment: 6 pages, 1 figure, submitted to JETP Letter

Hydrothermal sensitivities of seed populations underlie fluctuations of dormancy states in an annual plant community

Plant germination ecology involves continuous interactions between changing environmental conditions and the sensitivity of seed populations to respond to those conditions at a given time. Ecologically meaningful parameters characterizing germination capacity (or dormancy) are needed to advance our understanding of the evolution of germination strategies within plant communities. The germination traits commonly examined (e.g., maximum germination percentage under optimal conditions) may not adequately reflect the critical ecological differences in germination behavior across species, communities, and seasons. In particular, most seeds exhibit primary dormancy at dispersal that is alleviated by exposure to dry after-ripening or to hydrated chilling to enable germination in a subsequent favorable season. Population-based threshold (PBT) models of seed germination enable quantification of patterns of germination timing using parameters based on mechanistic assumptions about the underlying germination physiology. We applied the hydrothermal time (HTT) model, a type of PBT model that integrates environmental temperature and water availability, to study germination physiology in a guild of coexisting desert annual species whose seeds were after-ripened by dry storage under different conditions. We show that HTT assumptions are valid for describing germination physiology in these species, including loss of dormancy during after-ripening. Key HTT parameters, the hydrothermal time constant (θHT ) and base water potential distribution among seeds (Ψb (g)), were effective in describing changes in dormancy states and in clustering species exhibiting similar germination syndromes. θHT is an inherent species-specific trait relating to timing of germination that correlates well with long-term field germination fraction, while Ψb (g) shifts with depth of dormancy in response to after-ripening and seasonal environmental variation. Predictions based on variation among coexisting species in θHT and Ψb (g) in laboratory germination tests matched well with 25-yr observations of germination dates and fractions for the same species in natural field conditions. Seed dormancy and germination strategies, which are significant contributors to long-term species demographics under natural conditions, can be represented by readily measurable functional traits underlying variation in germination phenologies.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Turning up by turning over : the change of scenery effect in major league baseball

Purpose: This study examined a “change of scenery” effect on performance in major league baseball (MLB). We also tested this effect for voluntary versus involuntary employee departures, as well as employees returning to a past employer. Design/Methodology/Approach: This study uses publicly available MLB performance data from 2004 to 2015. The data comprise 712 team changes for players following two consecutive years with the same organization. Data were analyzed using MANCOVA to assess the impact of changing teams on player performance. Findings: Results indicate players with declining performance benefited significantly from a change of scenery. Following a team change, these players experienced a significant increase in their performance that remained stable through a subsequent season. The effect was not different for players who changed teams via trade and free agency and was modest for those returning to a past organization. Analysis also showed that players leaving while their performance was improving suffered a subsequent performance drop-off in the new organization. Implications: As the war for talent escalates and employees change jobs more frequently, extending our understanding of how performance can be influenced by work context may provide new insight into organization staffing policies. Originality/Value: Results extend field theory by highlighting how past performance interacts with new work contexts to influence performance. This is one of the few studies evaluating the job change-performance relationship, and perhaps the first to account for the effects of performance trends prior to exit

Time-Translation Invariance of Scattering Maps and Blue-Shift Instabilities on Kerr Black Hole Spacetimes

In this paper, we provide an elementary, unified treatment of two distinct blue-shift instabilities for the scalar wave equation on a fixed Kerr black hole background: the celebrated blue-shift at the Cauchy horizon (familiar from the strong cosmic censorship conjecture) and the time-reversed red-shift at the event horizon (relevant in classical scattering theory). Our first theorem concerns the latter and constructs solutions to the wave equation on Kerr spacetimes such that the radiation field along the future event horizon vanishes and the radiation field along future null infinity decays at an arbitrarily fast polynomial rate, yet, the local energy of the solution is infinite near any point on the future event horizon. Our second theorem constructs solutions to the wave equation on rotating Kerr spacetimes such that the radiation field along the past event horizon (extended into the black hole) vanishes and the radiation field along past null infinity decays at an arbitrarily fast polynomial rate, yet, the local energy of the solution is infinite near any point on the Cauchy horizon. The results make essential use of the scattering theory developed in [M. Dafermos, I. Rodnianski and Y. Shlapentokh-Rothman, A scattering theory for the wave equation on Kerr black hole exteriors, preprint (2014) available at \url{http://arxiv.org/abs/1412.8379}] and exploit directly the time-translation invariance of the scattering map and the non-triviality of the transmission map.Comment: 26 pages, 12 figure