9,826 research outputs found
Analog simulation of the Voigt solid
A method of reducing a mixed partial differential equation with boundary conditions to a form suitable for programming on the analog computer is developed. Presented along with the computer program set up to be used on the EAI TR-48 analog computer is a systematic check procedure to indicate possible computer malfunctions and programming errors. The results of the computer simulation are presented and supported with observed data --Abstract, page ii
Mauriac Syndrome in a Child with a Positive Antinuclear Antibody Screen
A 17-year-old male with type 1 diabetes mellitus (T1DM) presented to clinic with elevated transaminases and a positive antinuclear antibody (ANA) screen. Due to concern for autoimmune hepatitis, a liver biopsy was performed which revealed Mauriac syndrome. This case report is the second known description of a child with Mauriac syndrome presenting with positive autoimmune markers
Nonthermal THz to TeV Emission from Stellar Wind Shocks in the Galactic Center
The central parsec of the Galaxy contains dozens of massive stars with a
cumulative mass loss rate of ~ 10^{-3} solar masses per year. Shocks among
these stellar winds produce the hot plasma that pervades the central part of
the galaxy. We argue that these stellar wind shocks also efficiently accelerate
electrons and protons to relativistic energies. The relativistic electrons
inverse Compton scatter the ambient ultraviolet and far infrared radiation
field, producing high energy gamma-rays with a roughly constant luminosity from
\~ GeV to ~ 10 TeV. This can account for the TeV source seen by HESS in the
Galactic Center. Our model predicts a GLAST counterpart to the HESS source with
a luminosity of ~ 10^{35} ergs/s and cooling break at ~ 4 GeV. Synchrotron
radiation from the same relativistic electrons should produce detectable
emission at lower energies, with a surface brightness ~ 10^{32} B^2_{-3}
ergs/s/arcsec^2 from ~ THz to ~ keV, where B_{-3} is the magnetic field
strength in units of mG. The observed level of diffuse thermal X-ray emission
in the central parsec requires B < 300 micro-G in our models. Future detection
of the diffuse synchrotron background in the central parsec can directly
constrain the magnetic field strength, providing an important boundary
condition for models of accretion onto Sgr A*.Comment: submitted to ApJ Letter
Thin-disk laser pump schemes for large number of passes and moderate pump source quality
Novel thin-disk laser pump layouts are proposed yielding an increased number
of passes for a given pump module size and pump source quality. These novel
layouts result from a general scheme which bases on merging two simpler pump
optics arrangements. Some peculiar examples can be realized by adapting
standard commercially available pump optics simply by intro ducing an
additional mirror-pair. More pump passes yield better efficiency, opening the
way for usage of active materials with low absorption. In a standard multi-pass
pump design, scaling of the number of beam passes brings ab out an increase of
the overall size of the optical arrangement or an increase of the pump source
quality requirements. Such increases are minimized in our scheme, making them
eligible for industrial applicationsComment: 16 pages, 9 figure
Solid electrolyte for fuel cell
Thesis: B.S., Massachusetts Institute of Technology, Department of Chemical Engineering, 1953Includes bibliographical references (leaf 19).by Raymond F. Pohl.B.S.B.S. Massachusetts Institute of Technology, Department of Chemical Engineerin
Many-body theory of excitation dynamics in an ultracold Rydberg gas
We develop a theoretical approach for the dynamics of Rydberg excitations in
ultracold gases, with a realistically large number of atoms. We rely on the
reduction of the single-atom Bloch equations to rate equations, which is
possible under various experimentally relevant conditions. Here, we explicitly
refer to a two-step excitation-scheme. We discuss the conditions under which
our approach is valid by comparing the results with the solution of the exact
quantum master equation for two interacting atoms. Concerning the emergence of
an excitation blockade in a Rydberg gas, our results are in qualitative
agreement with experiment. Possible sources of quantitative discrepancy are
carefully examined. Based on the two-step excitation scheme, we predict the
occurrence of an antiblockade effect and propose possible ways to detect this
excitation enhancement experimentally in an optical lattice as well as in the
gas phase.Comment: 12 pages, 8 figure
Recommended from our members
Selective activation as an explanation fro hindsight bias
In hindsight, people often claim to have known more in foresight than they actually did. For example, the confidence for one of several possible outcomes is larger when it is known that this particular outcome occurred. A widespread explanation of hindsight bias assumes that the feedback serves as an anchor. How precisely this anchor takes effect and why it leads to a bias towards the anchor value has not been satisfactorily answered yet. One possible mechanism to explain hindsight bias assumes that the encoding of the feedback leads to a selective activation of the item-specific knowledge base. As a result, specific information units are strengthened and are thus more likely to be recalled when a person tries to reconstruct his or her original judgment. We tested the effect of selective activation in two hindsight experiments. The results showed a clear hindsight bias in that the recalled confidence ratings were distorted towards the feedback. Moreover, the consequences of selective activation were evident in that more information favoring the feedback was recalled
Correlations of Rydberg excitations in an ultra-cold gas after an echo sequence
We show that Rydberg states in an ultra-cold gas can be excited with strongly
preferred nearest-neighbor distance if densities are well below saturation. The
scheme makes use of an echo sequence in which the first half of a laser pulse
excites Rydberg states while the second half returns atoms to the ground state,
as in the experiment of Raitzsch et al. [Phys. Rev. Lett. 100 (2008) 013002].
Near to the end of the echo sequence, almost any remaining Rydberg atom is
separated from its next-neighbor Rydberg atom by a distance slightly larger
than the instantaneous blockade radius half-way through the pulse. These
correlations lead to large deviations of the atom counting statistics from a
Poissonian distribution. Our results are based on the exact quantum evolution
of samples with small numbers of atoms. We finally demonstrate the utility of
the omega-expansion for the approximate description of correlation dynamics
through an echo sequence.Comment: 8 pages, 6 figure
High-current Capability of Coaxial Cables in Magnetoforming Applications
Magnetoforming technology often requires impulse current amplitudes of several hundred kiloamps, at pulse durations between 30 µs and > 100 µs. Often, it is required to provide the impulse via a flexible transmission line (cable) in order to allow the forming coil to be positioned correctly. These cables have to withstand the high pulse currents without deterioration for a large number of pulses. In addition, it is necessary to minimise the inductance of the cable connection, as an increase in inductance negatively influences the efficiency of the installation as a whole, whence low-inductance coaxial cables are required which are able to fulfil all of these requirements simultaneously. Manufacturers normally do not specify the impulse current capability of coaxial cables, as this is not necessary for most standard applications. Therefore, experiments were performed to explore the limits of commercial medium high voltage cables in regard of their impulse current withstand capability for these specific impulse parameters. A coaxial medium voltage cable has been tested at single pulses of ca. 100 µs duration, at amplitudes between 30 and 140 kA. The radial deformation (expansion) of the cable was detected with a high-resolution, high-speed camera. At a frame rate of 9000 frames/s the expansion of the cable has been determined as a function of the current amplitude. We observed dynamic changes of the cable diameter at currents above 81 kA, reaching up to 1.26 mm increase in diameter at 142 kA pulse amplitude. Above 100 kA, part of the deformation becomes irreversible, with cumulated permanent changes of up to 1 mm. The measurements are used to estimate the operating range of these cables
- …