2,866 research outputs found
Controlling hysteresis in superconducting constrictions with a resistive shunt
We demonstrate control of the thermal hysteresis in superconducting
constrictions by adding a resistive shunt. In order to prevent thermal
relaxation oscillations, the shunt resistor is placed in close vicinity of the
constriction, making the inductive current-switching time smaller than the
thermal equilibration time. We investigate the current-voltage characteristics
of the same constriction with and without the shunt-resistor. The widening of
the hysteresis-free temperature range is explained on the basis of a simple
model.Comment: 6 pages, 7 figures, including Supplementary Informatio
Nonhypnotic low-dose etomidate for rapid correction of hypercortisolaemia in cushing's syndrome
We determined the adrenostatic potential of low-dose nonhypnotic etomidate in six patients with Cushing's syndrome (ectopic Cushing's syndrome,n=2; Cushing's disease,n=3; bilateral adrenal adenoma,n=1). Etomidate was given as a continuous infusion for 32 h in a dose of 2.5 mg/h (n=5) or 0.3 mg/kg/h (n=3), respectively. Saline was given during a control period. The responsiveness to exogenous ACTH was studied during placebo and 7 and 31 h after commencing etomidate by administration of 250 µg 1–24 ACTH i.v. Etomidate (2.5 mg/h) led to a consistent decrease in serum cortisol in all patients from a mean of 39.4±13.3 to 21.1±5.7 µg/dl after 7 h (P<0.05 compared with placebo). After 24 h cortisol was reduced further to a mean steady state concentration of 12.3±5.7 µg/dl (P<0.05). At the end of the infusion period the cortisol increase in response to ACTH was reduced but not abolished. In contrast, a dose of 0.3 mg/kg/h etomidate induced unresponsiveness of serum cortisol to exogenous ACTH within 7 h. However, sedation was observed in two out of three patients at this dose, while during etomidate in a dose of 2.5 mg/h no side effects were seen. We conclude that low-dose non-hypnotic etomidate reduces serum cortisol to within the normal range in patients with Cushing's syndrome. The possibility to dissociate the adrenostatic effect of etomidate from its hypnotic action, the absence of side effects, and the i.v. route suggest that etomidate in a dose of 0.04–0.05 mg/kg/h may become the drug of choice for rapid initial control of hypercortisolism
Niobium-based superconducting nano-devices fabrication using all-metal suspended masks
We report a novel method for the fabrication of superconducting nanodevices
based on niobium. The well-known difficulties of lithographic patterning of
high-quality niobium are overcome by replacing the usual organic resist mask by
a metallic one. The quality of the fabrication procedure is demonstrated by the
realization and characterization of long and narrow superconducting lines and
niobium-gold-niobium proximity SQUIDs
Project of a superfluid He3 detector for direct detection of non-baryonic dark matter : MACHe3
MACHe3 (MAtrix of Cells of superfluid Helium 3) is a project of non-baryonic
Dark Matter search using superfluid He3 as sensitive medium. Simulations on a
high granularity matrix show very good rejection against background events.
First results on a prototype cell are very encouraging. Neutron detection has
been highlighted as well as cosmic muon detection. A phenomenological study has
been done with the DarkSUSY code to investigate complementarity of MACHe3 with
existing Dark Matter detectors.Comment: 5 pages, 5 figures, to appear in Proceedings of the 4th Marseille
International Cosmology Conferenc
Etching suspended superconducting hybrid junctions from a multilayer
A novel method to fabricate large-area superconducting hybrid tunnel
junctions with a suspended central normal metal part is presented. The samples
are fabricated by combining photo-lithography and chemical etch of a
superconductor - insulator - normal metal multilayer. The process involves few
fabrication steps, is reliable and produces extremely high-quality tunnel
junctions. Under an appropriate voltage bias, a significant electronic cooling
is demonstrated
Disquisition on material parameters and their influence on wear rates at high temperatures
The aim of this work is to find correlations of hard phase content and matrix type with hot hardness and wear rates in the cyclic impact abrasion test at high testing temperatures. Several materials with different matrix types and varying hard phase content have been investigated regarding their wear behaviour as well as their hot hardness up to 800°C. The hot hardness and hard phase content then was correlated to the wear rates using statistical methods. Materials with comparable matrix properties and higher hard phase content always have higher hot hardness and these parameters are statistically dependent so correlation of wear rate with hot hardness is statistically sufficient. It was found, that within the same material the wear rate is correlated to the hot hardness as long as there is no significant change in the wear mechanism. When the matrix of the material changes the hot hardness can not be directly correlated to the wear rate any more. It was also found that among all materials tested those with an austenitic matrix generally have higher wear resistance even if they have the same hot hardness
Bolometric calibration of a superfluid He detector for Dark Matter search: direct measurement of the scintillated energy fraction for neutron, electron and muon events
We report on the calibration of a superfluid He bolometer developed for
the search of non-baryonic Dark Matter. Precise thermometry is achieved by the
direct measurement of thermal excitations using Vibrating Wire Resonators
(VWRs). The heating pulses for calibration were produced by the direct quantum
process of quasiparticle generation by other VWRs present. The bolometric
calibration factor is analyzed as a function of temperature and excitation
level of the sensing VWR. The calibration is compared to bolometric
measurements of the nuclear neutron capture reaction and heat depositions by
cosmic muons and low energy electrons. The comparison allows a quantitative
estimation of the ultra-violet scintillation rate of irradiated helium,
demonstrating the possibility of efficient electron recoil event rejection.Comment: 17 pages, submitted to Nuc. Instr. Meth.
MACHe3, a prototype for non-baryonic dark matter search: KeV event detection and multicell correlation
Superfluid He3 at ultra-low temperatures (100 microKelvins) is a sensitive
medium for the bolometric detection of particles. MACHe3 (MAtrix of Cells of
Helium 3) is a project for non-baryonic dark matter search using He3 as a
sensitive medium. Simulations made on a high granularity detector show a very
good rejection to background signals. A multicell prototype including 3
bolometers has been developed to allow correlations between the cells for
background event discrimination. One of the cells contains a low activity Co57
source providing conversion electrons of 7.3 and 13.6 keV to confirm the
detection of low energy events. First results on the multicell prototype are
presented. A detection threshold of 1 keV has been achieved. The detection of
low energy conversion electrons coming from the Co57 source is highlighted as
well as the cosmic muon spectrum measurement. The possibility to reject
background events by using the correlation among the cells is demonstrated from
the simultaneous detection of muons in different cells
Stabilized high-power laser system for the gravitational wave detector advanced LIGO
An ultra-stable, high-power cw Nd:YAG laser system, developed for the ground-based gravitational wave detector Advanced LIGO (Laser Interferometer Gravitational-Wave Observatory), was comprehensively characterized. Laser power, frequency, beam pointing and beam quality were simultaneously stabilized using different active and passive schemes. The output beam, the performance of the stabilization, and the cross-coupling between different stabilization feedback control loops were characterized and found to fulfill most design requirements. The employed stabilization schemes and the achieved performance are of relevance to many high-precision optical experiments
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