44,909 research outputs found
The traveling-wave V-antenna
Combination resonant V-antenna and traveling-wave dipole antenn
Controlling the crystal polymorph by exploiting the time dependence of nucleation rates
Most substances can crystallise into two or more different crystal lattices,
called polymorphs. Despite this, there are no systems in which we can
quantitatively predict the probability of one competing polymorph forming,
instead of the other. We address this problem using large scale (hundreds of
events) studies of the competing nucleation of the alpha and gamma polymorphs
of glycine. In situ Raman spectroscopy is used to identify the polymorph of
each crystal. We find that the nucleation kinetics of the two polymorphs is
very different. Nucleation of the alpha polymorph starts off slowly but
accelerates, while nucleation of the gamma polymorph starts off fast but then
slows. We exploit this difference to increase the purity with which we obtain
the gamma polymorph by a factor of ten. The statistics of the nucleation of
crystals is analogous to that of human mortality, and using a result from
medical statistics we show that conventional nucleation data can say nothing
about what, if any, are the correlations between competing nucleation
processes. Thus we can show that, with data of our form, it is impossible to
disentangle the competing nucleation processes. We also find that the growth
rate and the shape of a crystal depends on when it nucleated. This is new
evidence that nucleation and growth are linked.Comment: 8 pages, plus 17 pages of supplementary materia
Oral human papillomavirus (HPV) infection in men who have sex with men: prevalence and lack of anogenital concordance.
To estimate the prevalence of oral detectable human papillomavirus (HPV) DNA in HIV-negative men who have sex with men (MSM) attending a sexual health clinic in London and concordance with anogenital HPV infection. Such data are important to improve our understanding of the epidemiology of oral HPV and the potential use of vaccines to prevent oropharyngeal cancers
Development of a Microsatellite Library in \u3cem\u3eLolium Perenne\u3c/em\u3e
Lolium perenne, as one of the most important forage grasses of temperate regions, combines a number of very useful characteristics, e.g., good seedling establishment, with a low resistance to drought and limited winter hardiness. Trait selection and introgression can be greatly enhanced by the use of molecular markers in a genetic linkage map. The aim of this project was the generation of a genomic microsatellite library which when combined with microsatellites developed from a Genethresher database would give good genome coverage coupled to high levels of marker polymorphism
Vectorcardiographic changes during extended space flight
To assess the effects of space flight on cardiac electrical properties, vectorcardiograms were taken on the 9 Skylab astronauts during the flights of 28, 59, and 84 days. The Frank lead system was used and observations were made at rest; during 25%, 50% and 75% of maximum exercise; during a short pulse of exercise (150 watts, 2 minutes); and after exercise. Data from 131 in-flight tests were analyzed by computer and compared to preflight and postflight values. Statistically significant increase in QRS vector magnitude (six of nine crewmen); T vector magnitude (five of nine crewmen); and resting PR interval duration (six of nine crewmen) occurred. During exercise the PR interval did not differ from preflight. Exercise heart rates inflight were the same as preflight, but increased in the immediate postflight period. With the exception of the arrhythmias, no deleterious vectorcardiographic changes were observed during the Skylab missions
Notes on multiplicativity of maximal output purity for completely positive qubit maps
A problem in quantum information theory that has received considerable
attention in recent years is the question of multiplicativity of the so-called
maximal output purity (MOP) of a quantum channel. This quantity is defined as
the maximum value of the purity one can get at the output of a channel by
varying over all physical input states, when purity is measured by the Schatten
-norm, and is denoted by . The multiplicativity problem is the
question whether two channels used in parallel have a combined that is
the product of the of the two channels. A positive answer would imply a
number of other additivity results in QIT.
Very recently, P. Hayden has found counterexamples for every value of .
Nevertheless, these counterexamples require that the dimension of these
channels increases with and therefore do not rule out multiplicativity
for in intervals with depending on the channel dimension. I
argue that this would be enough to prove additivity of entanglement of
formation and of the classical capacity of quantum channels.
More importantly, no counterexamples have as yet been found in the important
special case where one of the channels is a qubit-channel, i.e. its input
states are 2-dimensional. In this paper I focus attention to this qubit case
and I rephrase the multiplicativity conjecture in the language of block
matrices and prove the conjecture in a number of special cases.Comment: Manuscript for a talk presented at the SSPCM07 conference in
Myczkowce, Poland, 10/09/2007. 12 page
Quantifying electronic correlation strength in a complex oxide: a combined DMFT and ARPES study of LaNiO
The electronic correlation strength is a basic quantity that characterizes
the physical properties of materials such as transition metal oxides.
Determining correlation strengths requires both precise definitions and a
careful comparison between experiment and theory. In this paper we define the
correlation strength via the magnitude of the electron self-energy near the
Fermi level. For the case of LaNiO, we obtain both the experimental and
theoretical mass enhancements by considering high resolution
angle-resolved photoemission spectroscopy (ARPES) measurements and density
functional + dynamical mean field theory (DFT + DMFT) calculations. We use
valence-band photoemission data to constrain the free parameters in the theory,
and demonstrate a quantitative agreement between the experiment and theory when
both the realistic crystal structure and strong electronic correlations are
taken into account. These results provide a benchmark for the accuracy of the
DFT+DMFT theoretical approach, and can serve as a test case when considering
other complex materials. By establishing the level of accuracy of the theory,
this work also will enable better quantitative predictions when engineering new
emergent properties in nickelate heterostructures.Comment: 10 pages, 5 figure
Stabilized lasers for advanced gravitational wave detectors
Second generation gravitational wave detectors require high power lasers with more than 100 W of output power and with very low temporal and spatial fluctuations. To achieve the demanding stability levels required, low noise techniques and adequate control actuators have to be part of the high power laser design. In addition feedback control and passive noise filtering is used to reduce the fluctuations in the so-called prestabilized laser system (PSL). In this paper, we discuss the design of a 200 W PSL which is under development for the Advanced LIGO gravitational wave detector and will present the first results. The PSL noise requirements for advanced gravitational wave detectors will be discussed in general and the stabilization scheme proposed for the Advanced LIGO PSL will be described
Bino Dark Matter and Big Bang Nucleosynthesis in the Constrained E6SSM with Massless Inert Singlinos
We discuss a new variant of the E6 inspired supersymmetric standard model
(E6SSM) in which the two inert singlinos are exactly massless and the dark
matter candidate has a dominant bino component. A successful relic density is
achieved via a novel mechanism in which the bino scatters inelastically into
heavier inert Higgsinos during the time of thermal freeze-out. The two massless
inert singlinos contribute to the effective number of neutrino species at the
time of Big Bang Nucleosynthesis, where the precise contribution depends on the
mass of the Z' which keeps them in equilibrium. For example for mZ' > 1300 GeV
we find Neff \approx 3.2, where the smallness of the additional contribution is
due to entropy dilution. We study a few benchmark points in the constrained
E6SSM with massless inert singlinos to illustrate this new scenario.Comment: 24 pages, revised for publication in JHE
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