8,390 research outputs found
Development of battery separator composites
Improved inorganic-organic separators developed by NASA were commercially prepared. A single-ply asbestos substrate was developed, as well as alternative substrates based on cellulose and on polypropylene fibers. The single-ply asbestos was bound with butyl rubber and was functionally superior to the formerly used polyphenylene oxide saturated sheet. Commercially prepared separators exhibited better measured separator properties than the NASA standard. Cycle life in Ni/Zn and Ag/Zn cells was related to substrate, decreasing in the order; asbestos cellulose paper nonwoven polypropylene. The cycle life of solvent-coated separators was better than aqueous in Ni/Zn cells, while aqueous coatings were better in Ag/Zn cells
Alkaline battery, separator therefore
An improved battery separator for alkaline battery cells has low resistance to electrolyte ion transfer and high resistance to electrode ion transfer. The separator is formed by applying an improved coating to an electrolyte absorber. The absorber, preferably, is a flexible, fibrous, and porous substrate that is resistant to strong alkali and oxidation. The coating composition includes an admixture of a polymeric binder, a hydrolyzable polymeric ester and inert fillers. The coating composition is substantially free of reactive fillers and plasticizers commonly employed as porosity promoting agents in separator coatings. When the separator is immersed in electrolyte, the polymeric ester of the film coating reacts with the electrolyte forming a salt and an alcohol. The alcohol goes into solution with the electrolyte while the salt imbibes electrolyte into the coating composition. When the salt is formed, it expands the polymeric chains of the binder to provide a film coating substantially permeable to electrolyte ion transfer but relatively impermeable to electrode ion transfer during use
A Survey for Low-Surface-Brightness Galaxies Around M31. I. The Newly Discovered Dwarf Andromeda V
We present images and a color-magnitude diagram for And V, a new dwarf
spheroidal companion to M31 that was found using a digital filtering technique
applied to 1550 square degrees of the second Palomar Sky Survey. And V resolves
into stars easily in follow-up 4-m V- and I-band images, from which we deduce a
distance of 810 +/- 45 kpc using the tip of the red giant branch method. Within
the uncertainties, this distance is identical to the Population II distances
for M31 and, combined with a projected separation of 112 kpc, provides strong
support for a physical association between the two galaxies. There is no
emission from And V detected in H alpha, 1.4 GHz radio continuum, or IRAS
bandpasses, and there is no young population seen in the color-magnitude
diagram that might suggest that And V is an irregular. Thus, the classification
as a new dwarf spheroidal member of the Local Group seems secure. With an
extinction-corrected central surface brightness of 25.2 V mag per square
arcsec, a mean metal abundance of [Fe/H] approximately -1.5, and no evidence
for upper AGB stars, And V resembles And I & III.Comment: Accepted for publication in The Astronomical Journal, November 1998
issue; 4 embedded PostScript figures, 4 JPEG figures; see
http://aloe.tuc.noao.edu/jacoby/dwarfs.html for a complete full-resolution
PostScript versio
Recommended from our members
SMM behaviour and magnetocaloric effect in heterometallic 3d-4f coordination clusters with high azide : metal ratios
We present the synthesis and characterization of heterometallic compounds with a very large azide to metal ratio and fascinating magnetic properties
The HELLAS2XMM survey: IV. Optical identifications and the evolution of the accretion luminosity in the Universe
We present results from the photometric and spectroscopic identification of
122 X-ray sources recently discovered by XMM-Newton in the 2-10 keV band (the
HELLAS2XMM 1dF sample). Their flux cover the range 8E-15-4E-13 cgs and the
total area surveyed is 0.9 deg2. About 20% of the hard X-ray selected sources
have an X-ray to optical flux ratio (X/O) ten times or more higher than that of
optically selected AGN. Unlike the faint sources found in the ultra-deep
Chandra and XMM-Newton surveys, which reach X-ray (and optical) fluxes more
than one order of magnitude lower than the HELLAS2XMM survey sources, many of
the extreme X/O sources in our sample have R<=25 and are therefore accessible
to optical spectroscopy. We report the identification of 13 sources with
X/O>10: 8 are narrow line QSO (i.e. QSO2), four are broad line QSO. We use a
combined sample of 317 hard X-ray selected sources (HELLAS2XMM 1dF, CDFN 1Msec,
SSA13 and Lockman Hole flux limited samples), 221 with measured z, to evaluate
the cosmological evolution of the hard X-ray source's number and luminosity
densities. Looking backward in time, the low luminosity sources (logL(2-10keV)
= 43-44 erg/s) increase in number at a rate different than the high luminosity
sources (logL(2-10keV)>44.5 erg/s), reaching a maximum around z=1 and then
levelling off beyond z=2. This translates into an accretion driven luminosity
density which is dominated by sources with logL(2-10keV) < 44.5 erg/s up to at
least z=1, while the contribution of the same sources and of those with
logL(2-10keV)>44.5 erg/s appear to be comparable between z=2 and 4.Comment: v2, minor changes, A&A in pres
On the propagation of jump discontinuities in relativistic cosmology
A recent dynamical formulation at derivative level \ptl^{3}g for fluid
spacetime geometries , that employs the concept
of evolution systems in first-order symmetric hyperbolic format, implies the
existence in the Weyl curvature branch of a set of timelike characteristic
3-surfaces associated with propagation speed |v| = \sfrac{1}{2} relative to
fluid-comoving observers. We show it is the physical role of the constraint
equations to prevent realisation of jump discontinuities in the derivatives of
the related initial data so that Weyl curvature modes propagating along these
3-surfaces cannot be activated. In addition we introduce a new, illustrative
first-order symmetric hyperbolic evolution system at derivative level
\ptl^{2}g for baryotropic perfect fluid cosmological models that are
invariant under the transformations of an Abelian isometry group.Comment: 19 pages, 1 table, REVTeX v3.1 (10pt), submitted for publication to
Physical Review D; added Report-No, corrected typo
Using Both Sides of Your Brain: The Case for Rapid Interhemispheric Switching
Individual brain hemispheres are often specialized for specific aspects of a behavior. How both sides of the brain coordinate their output to produce a perfectly seamless behavior is not known. Songbirds appear to achieve this by rapidly switching back and forth between hemispheres
- …