4,168 research outputs found

    Functional theories of thermoelectric phenomena

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    We review the progress that has been recently made in the application of time-dependent density functional theory to thermoelectric phenomena. As the field is very young, we emphasize open problems and fundamental issues. We begin by introducing the formal structure of \emph{thermal density functional theory}, a density functional theory with two basic variables -- the density and the energy density -- and two conjugate fields -- the ordinary scalar potential and Luttinger's thermomechanical potential. The static version of this theory is contrasted with the familiar finite-temperature density functional theory, in which only the density is a variable. We then proceed to constructing the full time-dependent non equilibrium theory, including the practically important Kohn-Sham equations that go with it. The theory is shown to recover standard results of the Landauer theory for thermal transport in the steady state, while showing greater flexibility by allowing a description of fast thermal response, temperature oscillations and related phenomena. Several results are presented here for the first time, i.e., the proof of invertibility of the thermal response function in the linear regime, the full expression of the thermal currents in the presence of Luttinger's thermomechanical potential, an explicit prescription for the evaluation of the Kohn-Sham potentials in the adiabatic local density approximation, a detailed discussion of the leading dissipative corrections to the adiabatic local density approximation and the thermal corrections to the resistivity that follow from it.Comment: 34 pages, 6 figure

    Transient charge and energy flow in the wide-band limit

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    The wide-band limit is a commonly used approximation to analyze transport through nanoscale devices. In this work we investigate its applicability to the study of charge and heat transport through molecular break junctions exposed to voltage biases and temperature gradients. We find that while this approximation faithfully describes the long-time charge and heat transport, it fails to characterize the short-time behavior of the junction. In particular, we find that the charge current flowing through the device shows a discontinuity when a temperature gradient is applied, while the energy flow is discontinuous when a voltage bias is switched on and even diverges when the junction is exposed to both a temperature gradient and a voltage bias. We provide an explanation for this pathological behavior and propose two possible solutions to this problem.Comment: 11 pages, 9 figure

    Effects of Force Level and Hand Dominance on Bilateral Transfer of a Fine Motor Skill

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    Our research is about bilateral transfer, a concept in motor learning where skills learned by one limb are "transferred", allowing the opposite limb to benefit from what was learned by the first limb. Previous research into bilateral transfer has raised questions about whether specific aspects of motor coordination are or are not transferred. We wanted to see whether learning to control pinch force by the thumb and index finger is transferable, and if it is, whether the learning transfers equally from either hand. We also want to look into the effects of different force levels on the degree of transfer. We designed a task using a program that takes force levels as inputs and has the participant trace shapes on a screen. By having participants perform with one hand, then practice with the other, and finally perform again with the initial hand, we can measure transfer as the difference in performance before and after practice with the other hand.Kinesiology and Health Educatio

    Radiation studies for GaAs in the ATLAS Inner Detector

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    We estimate the hardness factors and the equivalent 1 MeV neutron fluences for hadrons fluences expected at the GaAs positions wheels in the ATLAS Inner Detector. On this basis the degradation of the GaAs particle detectors made from different substrates as a function of years LHC operation is predicted.Comment: 11 pages, 6 Postscript figures, uses elsart.cls, submitted to Nucl. Inst. and Met

    Intraoss√§re Infusion: Eine wichtige Technik auch f√ľr die Kinderan√§sthesie

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    Zusammenfassung: Die zeitgerechte Etablierung eines ven√∂sen Zugangs kann insbesondere bei S√§uglingen und Kleinkindern eine gro√üe Herausforderung sein. Hier hat sich die intraoss√§re Infusionstechnik seit den 1940er Jahren als schnelle, effiziente und sichere Alternativmethode zur Schaffung eines Gef√§√üzugangs bew√§hrt, um einem vitalgef√§hrdeten Kind dringend ben√∂tigte Medikamente und Fl√ľssigkeiten zu applizieren. W√§hrend in den internationalen Leitlinien zur p√§diatrischen Notfallmedizin der intraoss√§ren Infusion eine hohe Priorit√§t einger√§umt wird, greifen die meisten An√§sthesisten nur sehr z√∂gerlich auf diese langj√§hrig bew√§hrte Punktionstechnik zur√ľck. Die vorliegende Arbeit beschreibt die intraoss√§re Infusionstechnik, stellt zwei unterschiedliche Kan√ľlierungssysteme vor und diskutiert, basierend auf den aktuellen notfallmedizinischen Leitlinien sowie anhand von eigenen Fallbeispielen, potenzielle Indikationen f√ľr die Kinderan√§sthesie. Demnach sollten insbesondere akut vital-gef√§hrdete Kinder mit Kreislaufstillstand, Laryngospasmus, akuter Atemwegsblutung, hypovol√§mischem Schock oder Hypothermie bei ausgedehnten Verbrennungen ohne liegenden bzw. rasch anzulegenden ven√∂sen Zugang mit einer intraoss√§ren Kan√ľle versorgt werden. Inwieweit die intraoss√§re Infusion auch beim nichtakut vital-gef√§hrdeten Kind mit schwierigem oder unm√∂glichem peripheren Venenzugang in der An√§sthesie √ľberbr√ľckend und zeitlich begrenzt eingesetzt werden sollte, wird die zuk√ľnftige Diskussion zeigen. Die erfolgreiche Anwendung der intraoss√§ren Infusionstechnik in der Kinderan√§sthesie verlangt die unmittelbare Verf√ľgbarkeit der entsprechenden Ausr√ľstung, die umfassende Schulung und das regelm√§√üige Training sowie eine klare Regelung f√ľr ihre Anwendung innerhalb der An√§sthesieabteilun

    Handling and analysis of ices in cryostats and glove boxes in view of cometary samples

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    Comet nucleus sample return mission and other return missions from planets and satellites need equipment for handling and analysis of icy samples at low temperatures under vacuum or protective gas. Two methods are reported which were developed for analysis of small icy samples and which are modified for larger samples in cometary matter simulation experiments (KOSI). A conventional optical cryostat system was modified to allow for transport of samples at 5 K, ion beam irradiation, and measurement in an off-line optical spectrophotometer. The new system consists of a removable window plug containing nozzles for condensation of water and volatiles onto a cold finger. This plug can be removed in a vacuum system, changed against another plug (e.g., with other windows (IR, VIS, VUV) or other nozzles). While open, the samples can be treated under vacuum with cooling by manipulators (cut, removal, sample taking, irradiation with light, photons, or ions). After bringing the plug back, the samples can be moved to another site of analysis. For handling the 30 cm diameter mineral-ice samples from the KOSI experiments an 80x80x80 cm glove box made out of plexiglass was used. The samples were kept in a liquid nitrogen bath, which was filled from the outside. A stream a dry N2 and evaporating gas from the bath purified the glove box from impurity gases and, in particular, H2O, which otherwise would condense onto the samples
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