23,669 research outputs found
Manufacture of DPFC-DMS polymer in the SKG range
BPFC-DMS block copolymers were synthesized on a pre-pilot scale (i.e., to 5 Kg lots) and subsequently fabricated into clear, colorless films. Details of the synthesis procedures, property determinations, and film casting techniques are presented. Solubility, viscosity and molecular weight characteristics of the resulting product are reported
New Velocity Distribution in the Context of the Eddington Theory
Exotic dark matter together with the vacuum energy (associated with the
cosmological constant) seem to dominate the Universe. Thus its direct detection
is central to particle physics and cosmology. Supersymmetry provides a natural
dark matter candidate, the lightest supersymmetric particle (LSP). One
essential ingredient in obtaining the direct detection rates is the density and
velocity distribution of the LSP. The detection rate is proportional to this
density in our vicinity. Furthermore, since this rate is expected to be very
low, one should explore the two characteristic signatures of the process,
namely the modulation effect, i.e. the dependence of the event rate on the
Earth's motion and the correlation of the directional rate with the motion of
the sun. Both of these crucially depend on the LSP velocity distribution. In
the present paper we study simultaneously density profiles and velocity
distributions based on the Eddington theory.Comment: 40 LaTex pages, 19 figures and one table. The previous version was
expanded to include new numerical solutions to Poisson's equation. Sheduled
to appear in vol. 588, ApJ, May 1, 300
Generalized curve fit and plotting (GECAP) program
Program generates graphs on 8 1/2 by 11 inch paper and is designed to be used by engineers and scientists who are not necessarily professional programers. It provides fast and efficient method for display of plotted data without having to generate any additional FORTRAN instructions
A Magnetically-Switched, Rotating Black Hole Model For the Production of Extragalactic Radio Jets and the Fanaroff and Riley Class Division
A model is presented in which both Fanaroff and Riley class I and II
extragalactic jets are produced by magnetized accretion disk coronae in the
ergospheres of rotating black holes. While the jets are produced in the
accretion disk itself, the output power still is an increasing function of the
black hole angular momentum. For high enough spin, the black hole triggers the
magnetic switch, producing highly-relativistic, kinetic-energy-dominated jets
instead of Poynting-flux-dominated ones for lower spin. The coronal mass
densities needed to trigger the switch at the observed FR break power are quite
small (), implying that the source of the jet material
may be either a pair plasma or very tenuous electron-proton corona, not the
main accretion disk itself.
The model explains the differences in morphology and Mach number between FR I
and II sources and the observed trend for massive galaxies to undergo the FR
I/II transition at higher radio power. It also is consistent with the energy
content of extended radio lobes and explains why, because of black hole
spindown, the space density of FR II sources should evolve more rapidly than
that of FR I sources.
If the present model is correct, then the ensemble average speed of
parsec-scale jets in sources distinguished by their FR I morphology (not
luminosity) should be distinctly slower than that for sources with FR II
morphology. The model also suggests the existence of a population of
high-redshift, sub-mJy FR I and II radio sources associated with spiral or
pre-spiral galaxies that flared once when their black holes were formed but
were never again re-kindled by mergers.Comment: 14 pages, 2 figures, final version to appear in Sept Ap
Endotaxial Si nanolines in Si(001):H
We present a detailed study of the structural and electronic properties of a
self-assembled silicon nanoline embedded in the H-terminated silicon (001)
surface, known as the Haiku stripe. The nanoline is a perfectly straight and
defect free endotaxial structure of huge aspect ratio; it can grow micrometre
long at a constant width of exactly four Si dimers (1.54nm). Another remarkable
property is its capacity to be exposed to air without suffering any
degradation. The nanoline grows independently of any step edges at tunable
densities, from isolated nanolines to a dense array of nanolines. In addition
to these unique structural characteristics, scanning tunnelling microscopy and
density functional theory reveal a one-dimensional state confined along the
Haiku core. This nanoline is a promising candidate for the long sought after
electronic solid-state one-dimensional model system to explore the fascinating
quantum properties emerging in such reduced dimensionality.Comment: 8 pages, 6 figure
AN EXPERIMENTAL ECONOMICS APPROACH TO ANALYZING PRICE DISCOVERY IN FORWARD AND SPOT MARKETS
Laboratory experiments are used to generate data that facilitate investigation of pricing behavior in forward and spot markets. Results suggest a tendency for prices in a spot market to converge to levels higher than those in a forward market. The difference in these market environments is the supply schedule. Buyers in a spot market are aware that supply is inelastic and become relatively aggressive bidders. Forward markets have a relatively elastic supply schedule and buyers fare better. This may motivate firms to promote forward markets and/or vertically integrate in the procurement of inputs.Experimental economics, Forward market, Price discovery, Spot market, Marketing,
Stress relief as the driving force for self-assembled Bi nanolines
Stress resulting from mismatch between a substrate and an adsorbed material
has often been thought to be the driving force for the self-assembly of
nanoscale structures. Bi nanolines self-assemble on Si(001), and are remarkable
for their straightness and length -- they are often more than 400 nm long, and
a kink in a nanoline has never been observed. Through electronic structure
calculations, we have found an energetically favourable structure for these
nanolines that agrees with our scanning tunneling microscopy and photoemission
experiments; the structure has an extremely unusual subsurface structure,
comprising a double core of 7-membered rings of silicon. Our proposed structure
explains all the observed features of the nanolines, and shows that surface
stress resulting from the mismatch between the Bi and the Si substrate are
responsible for their self-assembly. This has wider implications for the
controlled growth of nanostructures on semiconductor surfaces.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let
SUPPLY AND DEMAND RISKS IN LABORATORY FORWARD AND SPOT MARKETS: IMPLICATIONS FOR AGRICULTURE
Laboratory experimental methods are used to investigate the impacts of supply and/or demand risks on prices, quantities traded, and earnings within forward and spot market institutions. Random demand and/or supply shifts can be as much as 25 percent of the expected equilibrium outcome. Nevertheless, results suggest that the spot or forward trading institution itself has a greater influence on market outcomes than the presence of risk within the trading institutions. Sellers tend to have relatively higher earnings in a spot market than buyers, regardless of the risk. Total surplus, however, generally is greater in a forward market.laboratory markets, forward market, spot market, supply and/or demand risks, Demand and Price Analysis, Marketing,
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