4,168 research outputs found
Functional theories of thermoelectric phenomena
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
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
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
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
Intraossäre Infusion: Eine wichtige Technik auch für die Kinderanästhesie
Zusammenfassung: Die zeitgerechte Etablierung eines venösen Zugangs kann insbesondere bei Säuglingen und Kleinkindern eine große Herausforderung sein. Hier hat sich die intraossäre Infusionstechnik seit den 1940er Jahren als schnelle, effiziente und sichere Alternativmethode zur Schaffung eines Gefäßzugangs bewährt, um einem vitalgefährdeten Kind dringend benötigte Medikamente und Flüssigkeiten zu applizieren. Während in den internationalen Leitlinien zur pädiatrischen Notfallmedizin der intraossären Infusion eine hohe Priorität eingeräumt wird, greifen die meisten Anästhesisten nur sehr zögerlich auf diese langjährig bewährte Punktionstechnik zurück. Die vorliegende Arbeit beschreibt die intraossäre Infusionstechnik, stellt zwei unterschiedliche Kanülierungssysteme vor und diskutiert, basierend auf den aktuellen notfallmedizinischen Leitlinien sowie anhand von eigenen Fallbeispielen, potenzielle Indikationen für die Kinderanästhesie. Demnach sollten insbesondere akut vital-gefährdete Kinder mit Kreislaufstillstand, Laryngospasmus, akuter Atemwegsblutung, hypovolämischem Schock oder Hypothermie bei ausgedehnten Verbrennungen ohne liegenden bzw. rasch anzulegenden venösen Zugang mit einer intraossären Kanüle versorgt werden. Inwieweit die intraossäre Infusion auch beim nichtakut vital-gefährdeten Kind mit schwierigem oder unmöglichem peripheren Venenzugang in der Anästhesie überbrückend und zeitlich begrenzt eingesetzt werden sollte, wird die zukünftige Diskussion zeigen. Die erfolgreiche Anwendung der intraossären Infusionstechnik in der Kinderanästhesie verlangt die unmittelbare Verfügbarkeit der entsprechenden Ausrüstung, die umfassende Schulung und das regelmäßige Training sowie eine klare Regelung für ihre Anwendung innerhalb der Anästhesieabteilun
Handling and analysis of ices in cryostats and glove boxes in view of cometary samples
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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