9,478 research outputs found
Several new catalysts for reduction of oxygen in fuel cells
Test results prove nickel carbide or nitride, nickel-cobalt carbide, titanium carbide or nitride, and intermetallic compounds of the transition or noble metals to be efficient electrocatalysts for oxygen reduction in alkaline electrolytes in low temperature fuel cells
Extreme thermopower anisotropy and interchain transport in the quasi-one-dimensional metal Li(0.9)Mo(6)O(17)
Thermopower and electrical resistivity measurements transverse to the
conducting chains of the quasi-one-dimensional metal Li(0.9)Mo(6)O(17) are
reported in the temperature range 5 K = 400 K the
interchain transport is determined by thermal excitation of charge carriers
from a valence band ~ 0.14 eV below the Fermi level, giving rise to a large,
p-type thermopower that coincides with a small, n-type thermopower along the
chains. This dichotomy -- semiconductor-like in one direction and metallic in a
mutually perpendicular direction -- gives rise to substantial transverse
thermoelectric (TE) effects and a transverse TE figure of merit among the
largest known for a single compound.Comment: PRL in press, manuscript (5pp, 4 Fig.'s) and Supplementary Material
(3pp, 3 Fig.'s
Acute complete heart block in dogs
A study has been conducted immediately and up to 18 days after the surgical production of complete heart block in dogs. Immediately after surgery cardiac output, coronary flow, and mean arterial pressure were reduced in rough proportion to the degree of bradycardia. In time, these measures began to return toward preoperative levels. Paralleling the diminished left ventricular work was a diminished left ventricular oxygen consumption with little consequent change in myocardial efficiency. Small rises were detected in central venous pressure. At autopsy, the only unequivocal abnormality was myocardial hypertrophy which became measurable between 2 and 18 days after operation
The Effects of Massive Substructures on Image Multiplicities in Gravitati onal Lenses
Surveys for gravitational lens systems have typically found a significantly
larger fraction of lenses with four (or more) images than are predicted by
standard ellipsoidal lens models (50% versus 25-30%). We show that including
the effects of smaller satellite galaxies, with an abundance normalized by the
observations, significantly increases the expected number of systems with more
than two images and largely explains the discrepancy. The effect is dominated
by satellites with ~20% the luminosity of the primary lens, in rough agreement
with the typical luminosities of the observed satellites. We find that the lens
systems with satellites cannot, however, be dropped from estimates of the
cosmological model based on gravitational lens statistics without significantly
biasing the results.Comment: 23 pages, 7 figures, more discussion of sis vs sie and inclusion of
uncorrelated contribution
THE EFFECT OF POLY-L-LYSINE ON THE UPTAKE OF REOVIRUS DOUBLE-STRANDED RNA IN MACROPHAGES IN VITRO
The effect of polycations on cultured mouse peitoneal macrophages has been examined. Polycations, at concentrations greater than 5 µg/ml, are toxic for macrophages) as measured by failure of the cells to exclude vital dyes. At toxic concentrations polycations bind in large amounts to nuclei and endoplasmic reticulum, while at nontoxic levels polycations bind selectively to the cell surface. Nontoxic concentrations of polycations stimulate binding of reovirus double-stranded (ds) RNA to the macrophages by forming polycation-dsRNA complexes either in the medium or at the cell surface. These complexes enter the cell in endocytic vacuoles and are concentrated in secondary lysosomes. Despite exposure to the acid hydrolases within this cell compartment, the dsRNA and the polycation (poly-L-lysine) are conserved in a macromolecular form within the vacuolar system. The mechanism(s) by which the uptake of infectious nucleic acids and the induction of interferon by dsRNA are stimulated by polycations are discussed
Heat Conduction and Magnetic Phase Behavior in Electron-Doped Ca_{1-x} La_x MnO_3(0 <= x <= 0.2)
Measurements of thermal conductivity (kappa) vs temperature are reported for
a series of Ca_{1-x} La_x MnO_3(0 <= x <= 0.2) specimens. For the undoped
(x=0), G-type antiferromagnetic compound a large enhancement of kappa below the
Neel temperature (T_N ~ 125 K) indicates a strong coupling of heat-carrying
phonons to the spin system. This enhancement exhibits a nonmonotonic behavior
with increasing x and correlates remarkably well with the small ferromagnetic
component of the magnetization reported previously [Neumeier and Cohn, Phys.
Rev. B 61 14319 (2000).] Magnetoelastic polaron formation appears to underly
the behavior of kappa and the magnetization at x <= 0.02.Comment: submitted to PRB; 4 pp., 4 Fig.'s, RevTex
Applications of DFT to the theory of twentieth-century harmony
Music theorists have only recently, following groundbreaking work by Quinn, recognized the potential for the DFT on pcsets, initially proposed by Lewin, to serve as the foundation of a theory of harmony for the twentieth century. This paper investigates pcset “arithmetic” – subset structure, transpositional combination, and interval content – through the lens of the DFT. It discusses relationships between interval classes and DFT magnitudes, considers special properties of dyads, pcset products, and generated collections, and suggest methods of using the DFT in analysis, including interpreting DFT magnitudes, using phase spaces to understand subset structure, and interpreting the DFT of Lewin’s interval function. Webern’s op. 5/4 and Bartok’s String Quartet 4, iv, are discussed.Accepted manuscrip
A transform of complementary aspects with applications to entropic uncertainty relations
Even though mutually unbiased bases and entropic uncertainty relations play
an important role in quantum cryptographic protocols they remain ill
understood. Here, we construct special sets of up to 2n+1 mutually unbiased
bases (MUBs) in dimension d=2^n which have particularly beautiful symmetry
properties derived from the Clifford algebra. More precisely, we show that
there exists a unitary transformation that cyclically permutes such bases. This
unitary can be understood as a generalization of the Fourier transform, which
exchanges two MUBs, to multiple complementary aspects. We proceed to prove a
lower bound for min-entropic entropic uncertainty relations for any set of
MUBs, and show that symmetry plays a central role in obtaining tight bounds.
For example, we obtain for the first time a tight bound for four MUBs in
dimension d=4, which is attained by an eigenstate of our complementarity
transform. Finally, we discuss the relation to other symmetries obtained by
transformations in discrete phase space, and note that the extrema of discrete
Wigner functions are directly related to min-entropic uncertainty relations for
MUBs.Comment: 16 pages, 2 figures, v2: published version, clarified ref [30
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