2,930 research outputs found
Alternative Refrigerants in Adiabatic Capillary Tubes
This study examines the mass flow rate of refrigerants in adiabatic capillary tubes, with an
emphasis on the nature of the metastable region for both single component refrigerants and
mixtures.
The metastable region of a capillary tube was found to be much more predictable than
previously thought. A new and revealing data taking technique, which takes the history of the
system into account, allowed for the discovery of a hysteresis effect in the mass flow rate as the
level of inlet subcooling is increased and decreased. This finding may have a profound impact on
the future of capillary tube data acquisition and modeling.Air Conditioning and Refrigeration Project 6
Renin-angiotensin system in pregnant South African blacks
Plasma renin activity was measured in the arterial blood, peripheral venous blood, uterine venous blood and in the urine of pregnant South African Blacks, 14 normotensives and 19 with specific hypertensive disease. In addition renin activity was measured in the umbilical venous blood of the babies delivered by Caesarean section of these women. The renin activity was significantly lower in the blood of the specific hypertensive disease subjects than in the normotensives, but significantly higher in the urine of the hypertensive disease cases. Renin activity of the babies of the hypertensive and control subjects did not differ significantly.S. Afr. Med. J., 48, 302 (1974)
Three-dimensional fast electron transport for ignition-scale inertial fusion capsules
Three-dimensional hybrid PIC simulations are presented to study electron
energy transport and deposition in a full-scale fast ignition configuration.
Multi-prong core heating close to ignition is found when a few GA, few PW beam
is injected. Resistive beam filamentation in the corona seeds the 3D current
pattern that penetrates the core. Ohmic heating is important in the low-density
corona, while classical Coulomb deposition heats the core. Here highest energy
densities (few Tbar at 10 keV) are observed at densities above 200 g/cc. Energy
coupling to the core ranges from 20 to 30%; it is enhanced by beam collimation
and decreases when raising the beam particle energy from 1.5 to 5.5 MeV.Comment: 5 pages, 5 figure
The mineral and lipid composition of the arteries of white and bantu children
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Lateral vibration effects in atomic-scale friction
The influence of lateral vibrations on the stick-slip motion of a nanotip elastically pulled on a flat crystal surface is studied by atomic force microscopy measurements on a NaCl(001) surface in ultra-high vacuum. The slippage of the nanotip across the crystal lattice is anticipated at increasing driving amplitude, similarly to what is observed in presence of normal vibrations. This lowers the average friction force, as explained by the Prandtl-Tomlinson model with lateral vibrations superimposed at finite temperature. Nevertheless, the peak values of the lateral force, and the total energy losses, are expected to increase with the excitation amplitude, which may limit the practical relevance of this effect
Treatment of haemophilia A with purified factor VIII obtained from human plasma by cryoprecipitation
Orthonormal sequences in and time frequency localization
We study uncertainty principles for orthonormal bases and sequences in
. As in the classical Heisenberg inequality we focus on the product
of the dispersions of a function and its Fourier transform. In particular we
prove that there is no orthonormal basis for for which the time and
frequency means as well as the product of dispersions are uniformly bounded.
The problem is related to recent results of J. Benedetto, A. Powell, and Ph.
Jaming.
Our main tool is a time frequency localization inequality for orthonormal
sequences in . It has various other applications.Comment: 18 page
Non-invasive laminar inference with MEG: comparison of methods and source inversion algorithms
Magnetoencephalography (MEG) is a direct measure of neuronal current flow; its anatomical resolution is therefore not constrained by physiology but rather by data quality and the models used to explain these data. Recent simulation work has shown that it is possible to distinguish between signals arising in the deep and superficial cortical laminae given accurate knowledge of these surfaces with respect to the MEG sensors. This previous work has focused around a single inversion scheme (multiple sparse priors) and a single global parametric fit metric (free energy). In this paper we use several different source inversion algorithms and both local and global, as well as parametric and non-parametric fit metrics in order to demonstrate the robustness of the discrimination between layers. We find that only algorithms with some sparsity constraint can successfully be used to make laminar discrimination. Importantly, local t-statistics, global cross-validation and free energy all provide robust and mutually corroborating metrics of fit. We show that discrimination accuracy is affected by patch size estimates, cortical surface features, and lead field strength, which suggests several possible future improvements to this technique. This study demonstrates the possibility of determining the laminar origin of MEG sensor activity, and thus directly testing theories of human cognition that involve laminar- and frequency-specific mechanisms. This possibility can now be achieved using recent developments in high precision MEG, most notably the use of subject-specific head-casts, which allow for significant increases in data quality and therefore anatomically precise MEG recordings
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