7,333 research outputs found
Dimensional crossover of the fundamental-measure functional for parallel hard cubes
We present a regularization of the recently proposed fundamental-measure
functional for a mixture of parallel hard cubes. The regularized functional is
shown to have right dimensional crossovers to any smaller dimension, thus
allowing to use it to study highly inhomogeneous phases (such as the solid
phase). Furthermore, it is shown how the functional of the slightly more
general model of parallel hard parallelepipeds can be obtained using the
zero-dimensional functional as a generating functional. The multicomponent
version of the latter system is also given, and it is suggested how to
reformulate it as a restricted-orientation model for liquid crystals. Finally,
the method is further extended to build a functional for a mixture of parallel
hard cylinders.Comment: 4 pages, no figures, uses revtex style files and multicol.sty, for a
PostScript version see http://dulcinea.uc3m.es/users/cuesta/cross.p
Mid-infrared quantum optics in silicon
Applied quantum optics stands to revolutionise many aspects of information
technology, provided performance can be maintained when scaled up. Silicon
quantum photonics satisfies the scaling requirements of miniaturisation and
manufacturability, but at 1.55 m it suffers from unacceptable linear and
nonlinear loss. Here we show that, by translating silicon quantum photonics to
the mid-infrared, a new quantum optics platform is created which can
simultaneously maximise manufacturability and miniaturisation, while minimising
loss. We demonstrate the necessary platform components: photon-pair generation,
single-photon detection, and high-visibility quantum interference, all at
wavelengths beyond 2 m. Across various regimes, we observe a maximum net
coincidence rate of 448 12 Hz, a coincidence-to-accidental ratio of 25.7
1.1, and, a net two photon quantum interference visibility of 0.993
0.017. Mid-infrared silicon quantum photonics will bring new quantum
applications within reach.Comment: 8 pages, 4 figures; revised figures, updated discussion in section 3,
typos corrected, added referenc
Selective-pivot sampling of radial distribution functions in asymmetric liquid mixtures
We present a Monte Carlo algorithm for selectively sampling radial
distribution functions and effective interaction potentials in asymmetric
liquid mixtures. We demonstrate its efficiency for hard-sphere mixtures, and
for model systems with more general interactions, and compare our simulations
with several analytical approximations. For interaction potentials containing a
hard-sphere contribution, the algorithm yields the contact value of the radial
distribution function.Comment: 5 pages, 5 figure
Experimental treatment of necrosis produced by proteolytic snake venoms. I – Action of isoxsuprine
General spherically symmetric elastic stars in Relativity
The relativistic theory of elasticity is reviewed within the spherically
symmetric context with a view towards the modeling of star interiors possessing
elastic properties such as theones expected in neutron stars. Emphasis is
placed on generality in the main sections of the paper, and the results are
then applied to specific examples. Along the way, a few general results for
spacetimes admitting isometries are deduced, and their consequences are fully
exploited in the case of spherical symmetry relating them next to the the case
in which the material content of the spacetime is some elastic material. This
paper extends and generalizes the pioneering work by Magli and Kijowski [1],
Magli [2] and [3], and complements, in a sense, that by Karlovini and
Samuelsson in their interesting series of papers [4], [5] and [6].Comment: 23 page
The Chisholm firestorm: observed microstructure, precipitation and lightning activity of a pyro-cumulonimbus
International audienceA fire storm that occurred on 28 May 2001 and devastated the town of Chisholm, ~150 km north of Edmonton, Alberta, induced a violent fire-invigorated cumulonimbus cloud. This pyro-cumulonimbus (pyro-Cb) had overshooting tops of 2.5?3 km above the tropopause, and injected massive amounts of smoke into the lower stratosphere. Fortunately, this event occurred under good coverage of radar, rain gauge, lightning and satellite measurements, which allowed in-depth documentation of the event, and gave us an opportunity to study the cloud top morphology and microstructure, precipitation and cloud electrification of the pyro-Cb. The combination of heat and smoke created a cloud with extremely small drops, which ascended rapidly in violent updrafts. There appeared to be little freezing up to the homogeneous freezing isotherm level of ?38°C. A cloud with such small and short-lived highly supercooled drops is incapable of producing precipitation except for few large graupel and hail, which produced the observed radar echoes and charged the cloud with positive lightning. The small cloud drops froze homogeneously to equally small ice particles, for which there is no mechanism to aggregate into precipitation particles, and which hence remain in the anvil. The lack of significant precipitation implies that only a small fraction of the smoke is scavenged, so that most of it is exhausted through the anvil to the upper troposphere and lower stratosphere. Comparisons with other cases suggest that a pyro-Cb does not have to be as violent as the Chisholm case for precipitation to be strongly suppressed. However, this level of convective vigor is necessary to create the overshooting updraft that injects the smoke into the lower stratosphere
Ten Year Operating Test Results and Post-Test Analysis of a 1/10 Segment Stirling Sodium Heat Pipe, Phase III
High-temperature heat pipes are being evaluated for use in energy conversion applications such as fuel cells, gas turbine re-combustors, Stirling cycle heat sources; and with the resurgence of space nuclear power both as reactor heat removal elements and as radiator elements. Long operating life and reliable performance are critical requirements for these applications. Accordingly, long-term materials compatibility is being evaluated through the use of high-temperature life test heat pipes. Thermacore, Inc., has carried out a sodium heat pipe 10-year life test to establish long-term operating reliability. Sodium heat pipes have demonstrated favorable materials compatibility and heat transport characteristics at high operating temperatures in air over long time periods. A representative one-tenth segment Stirling Space Power Converter heat pipe with an Inconel 718 envelope and a stainless steel screen wick has operated for over 87,000 hr (10 yr) at nearly 700 C. These life test results have demonstrated the potential for high-temperature heat pipes to serve as reliable energy conversion system components for power applications that require long operating lifetime with high reliability. Detailed design specifications, operating history, and post-test analysis of the heat pipe and sodium working fluid are described
Dynamic Glass Transition in Two Dimensions
The question about the existence of a structural glass transition in two
dimensions is studied using mode coupling theory (MCT). We determine the
explicit d-dependence of the memory functional of mode coupling for
one-component systems. Applied to two dimensions we solve the MCT equations
numerically for monodisperse hard discs. A dynamic glass transition is found at
a critical packing fraction phi_c^{d=2} = 0.697 which is above phi_c^{d=3} =
0.516 by about 35%. phi^d_c scales approximately with phi^d_{\rm rcp} the value
for random close packing, at least for d=2, 3. Quantities characterizing the
local, cooperative 'cage motion' do not differ much for d=2 and d=3, and we
e.g. find the Lindemann criterion for the localization length at the glass
transition. The final relaxation obeys the superposition principle, collapsing
remarkably well onto a Kohlrausch law. The d=2 MCT results are in qualitative
agreement with existing results from MC and MD simulations. The mean squared
displacements measured experimentally for a quasi-two-dimensional binary system
of dipolar hard spheres can be described satisfactorily by MCT for monodisperse
hard discs over four decades in time provided the experimental control
parameter Gamma (which measures the strength of dipolar interactions) and the
packing fraction phi are properly related to each other.Comment: 14 pages, 15 figure
Monte Carlo simulations of the screening potential of the Yukawa one-component plasma
A Monte Carlo scheme to sample the screening potential H(r) of Yukawa plasmas
notably at short distances is presented. This scheme is based on an importance
sampling technique. Comparisons with former results for the Coulombic
one-component plasma are given. Our Monte Carlo simulations yield an accurate
estimate of H(r) as well for short range and long range interparticle
distances.Comment: to be published in Journal of Physics A: Mathematical and Genera
Phase behaviour of additive binary mixtures in the limit of infinite asymmetry
We provide an exact mapping between the density functional of a binary
mixture and that of the effective one-component fluid in the limit of infinite
asymmetry. The fluid of parallel hard cubes is thus mapped onto that of
parallel adhesive hard cubes. Its phase behaviour reveals that demixing of a
very asymmetric mixture can only occur between a solvent-rich fluid and a
permeated large particle solid or between two large particle solids with
different packing fractions. Comparing with hard spheres mixtures we conclude
that the phase behaviour of very asymmetric hard-particle mixtures can be
determined from that of the large component interacting via an adhesive-like
potential.Comment: Full rewriting of the paper (also new title). 4 pages, LaTeX, uses
revtex, multicol, epsfig, and amstex style files, to appear in Phys. Rev. E
(Rapid Comm.
- …