Low-noise high-voltage DC power supply for nanopositioning applications

Nanopositioning techniques currently applied to characterize physical properties of materials interesting for applications at the microscopic scale rely on high-voltage electronic control circuits that should have the lowest possible noise level. Here we introduce a simple, flexible, and custom-built power supply circuit that can provide +375\,V with a noise level below 10\,ppm. The flexibility of the circuit comes from its topology based on discrete MOSFET components that can be suitable replaced in order to change the polarity as well as the output voltage and current.Comment: 3 pages, 2 figure

A gynandromorph of Xylocopa augusti and an unusual record of X. iris from Brazil (Hymenoptera: Apidae: Xylocopini)

We describe and illustrate for the first time a mixed gynandromorph of Xylocopa(Neoxylocopa) augusti Lepeletier de Saint Fargeau from Buenos Aires, Argentina. Also, we document and discuss a historical specimen of the Old World carpenter bee X. (Copoxyla) iris (Christ) possibly collected in Brazil.Fil: Lucia, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Entomología; ArgentinaFil: Villamil, Soledad Camila. Universidad Nacional del Sur. Departamento de Agronomía. Laboratorio de Estudios Apícolas; ArgentinaFil: Gonzalez, Victor H.. University of Kansas; Estados Unido

Evidence of Twisted flux-tube Emergence in Active Regions

Elongated magnetic polarities are observed during the emergence phase of bipolar active regions (ARs). These extended features, called magnetic tongues, are interpreted as a consequence of the azimuthal component of the magnetic flux in the toroidal flux-tubes that form ARs. We develop a new systematic and user-independent method to identify AR tongues. Our method is based on determining and analyzing the evolution of the AR main polarity inversion line (PIL). The effect of the tongues is quantified by measuring the acute angle [ tau] between the orientation of the PIL and the direction orthogonal to the AR main bipolar axis. We apply a simple model to simulate the emergence of a bipolar AR. This model lets us interpret the effect of magnetic tongues on parameters that characterize ARs ( e.g. the PIL inclination and the tilt angles, and their evolution). In this idealized kinematic emergence model, tau is a monotonically increasing function of the twist and has the same sign as the magnetic helicity. We systematically apply our procedure to a set of bipolar ARs that were observed emerging in line-of-sight magnetograms over eight years. For most of the cases studied, the tongues only have a small influence on the AR tilt angle since tongues have a much lower magnetic flux than the more concentrated main polarities. From the observed evolution of tau, corrected for the temporal evolution of the tilt angle and its final value when the AR is fully emerged, we estimate the average number of turns in the subphotospherically emerging flux-rope. These values for the 41 observed ARs are below unity, except for one. This indicates that subphotospheric flux-ropes typically have a low amount of twist, i.e. highly twisted flux-tubes are rare. Our results demonstrate that the evolution of the PIL is a robust indicator of the presence of tongues and constrains the amount of twist in emerging flux-tube

Markov Switching Garch Models of Currency Crises in Southeast Asia

This paper develops a model which is able to forecast exchange rate turmoil. Our starting point relies on the empirical evidence that exchange rate volatility is not constant. In fact, the modeling strategy adopted refers to the vast literature of the GARCH class of models, where the variance process is explicitly modeled. Further empirical evidence shows that it is possible to distinguish between two different regimes: “ordinary” versus “turbulence”. Low exchange rate changes are associated with low volatility (ordinary regime) and high exchange rate devaluations go together with high volatility. This calls for a regime switching approach. In our model we also allow the transition probabilities to vary over time as functions of economic and financial indicators. We find that real effective exchange rate, money supply relative to reserves, stock index returns and bank stock index returns and volatility are the major indicators.Currency crises, Markov Switching Models, Volatility

Larval description and phylogenetic placement of the Australian endemic genus Barretthydrus Lea, 1927 (Coleoptera: Dytiscidae: Hydroporinae: Hydroporini: Sternopriscina)

The larvae of the Australian endemic species Barretthydrus tibialis Lea, 1927 and Barretthydrus geminatus Lea, 1927 are described and illustrated for the first time, with detailed morphometric and chaetotaxic analyses of the cephalic capsule, head appendages, legs, last abdominal segment, and urogomphi. A parsimony analysis based on 118 informative larval characteristics of 34 species in all 10 tribes of the subfamily Hydroporinae was conducted using the program TNT. No clear larval morphological synapomorphies support the monophyletic origin of the tribe Hydroporini. Compared to other known larvae of Hydroporini, Barretthydrus Lea is postulated to share a closer phylogenetic relationship with Antiporus Sharp, which reinforces their inclusion in the subtribe Sternopriscina.Fil: Alarie, Yves. Laurentian University. Department of Biology; CanadáFil: Michat, Mariano Cruz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental. Laboratorio de Entomología; ArgentinaFil: Hendrich, L.. Zoologische Staatssammlung Munchen; AlemaniaFil: Watts, Chris H. S.. South Australian Museum; Australi

Perceptions and Factors Influencing Success in Professional Preparation Physical Therapy Education

The purpose of this study was to gather data on student background characteristics, the perceptions of social and academic support, and self-concept of current professional preparation physical therapy (PT) students. A second purpose was to determine whether any variables were predictive of academic success/retention and to investigate whether there were differences in those variables between majority and minority PT students. The study used mixed methods with entry-level PT students from Virginia and North Carolina. Questionnaires were collected from 575 of 778 PT students for a 74% response rate. Semi-structured interviews were conducted with 25 respondents. Girves and Wemmerus\u27 conceptual model of doctoral degree progress was used as the theoretical framework for the study. Statistically significant differences were found between ethnic groups in background characteristics, social support, academic support, and all self-concept variables. Overall significant predictors of success were: undergraduate grade point average (GPA), ethnicity, having personal financing sources or loans for school, achieving an award, perceptions that coursework was academically stimulating, perceptions of academic expectations, being satisfied with academic performance, perceived ratings of both undergraduate and graduate performance, and overall rating of their PT school experience. Statistical differences were found between the ethnic groups for predictors of academic success. The interview data supported the quantitative findings and added depth to the findings regarding both similarities and differences between the perceptions of facilitators and barriers experienced by majority and minority PT students. Constructs of the Girves and Wemmerus model were not fully supported for this population of graduate students; however, the combination of variables investigated in this study accounted for 55% of the variance in graduate GPA. The study\u27s findings are utilized in making recommendations for the recruitment and retention of physical therapy students, particularly minority students, in hoping to increase the diversity of the physical therapy profession