5,873 research outputs found
Effect of shape anisotropy on the phase diagram of the Gay-Berne fluid
We have used the density functional theory to study the effect of molecular
elongation on the isotropic-nematic, isotropic-smectic A and nematic-smectic A
phase transitions of a fluid of molecules interacting via the Gay-Berne
intermolecular potential. We have considered a range of length-to-width
parameter in steps of 0.2 at different densities and
temperatures. Pair correlation functions needed as input information in density
functional theory are calculated using the Percus-Yevick integral equation
theory. Within the small range of elongation, the phase diagram shows
significant changes. The fluid at low temperature is found to freeze directly
from isotropic to smectic A phase for all the values of considered by us
on increasing the density while nematic phase stabilizes in between isotropic
and smectic A phases only at high temperatures and densities. Both
isotropic-nematic and nematic-smectic A transition density and pressure are
found to decrease as we increase . The phase diagram obtained is compared
with computer simulation result of the same model potential and is found to be
in good qualitative agreement.Comment: 15 pages, 6 figure
Simultaneous measurement of multiple parameters of a subwavelength structure based on the weak value formalism
A mathematical extension of the weak value formalism to the simultaneous
measurement of multiple parameters is presented in the context of an optical
focused vector beam scatterometry experiment. In this example, preselection and
postselection are achieved via spatially-varying polarization control, which
can be tailored to optimize the sensitivity to parameter variations. Initial
experiments for the two-parameter case demonstrate that this method can be used
to measure physical parameters with resolutions at least 1000 times smaller
than the wavelength of illumination
Fundamental Limitations of Cavity-assisted Atom Interferometry
Atom interferometers employing optical cavities to enhance the beam splitter
pulses promise significant advances in science and technology, notably for
future gravitational wave detectors. Long cavities, on the scale of hundreds of
meters, have been proposed in experiments aiming to observe gravitational waves
with frequencies below 1 Hz, where laser interferometers, such as LIGO, have
poor sensitivity. Alternatively, short cavities have also been proposed for
enhancing the sensitivity of more portable atom interferometers. We explore the
fundamental limitations of two-mirror cavities for atomic beam splitting, and
establish upper bounds on the temperature of the atomic ensemble as a function
of cavity length and three design parameters: the cavity g-factor, the
bandwidth, and the optical suppression factor of the first and second order
spatial modes. A lower bound to the cavity bandwidth is found which avoids
elongation of the interaction time and maximizes power enhancement. An upper
limit to cavity length is found for symmetric two-mirror cavities, restricting
the practicality of long baseline detectors. For shorter cavities, an upper
limit on the beam size was derived from the geometrical stability of the
cavity. These findings aim to aid the design of current and future
cavity-assisted atom interferometers.Comment: 11 pages, 12 figure
A Simulation Study on Multicomponent Lipid Bilayer
Simulation of a multicomponent lipid bilayer having a fixed percentage of
cholesterol is done to study phase transition leading to domain formation. The
concept of random lattice has been used in simulation to account for the
coupling between the internal and translational degrees of freedom of lipid
molecules. Considering a canonical ensemble, dissimilar lipid molecules are
allowed to exchange their positions in the lattice subject to standard
metropolis algorithm. The steps involved in the process effectively takes into
account for the movement of sphingolipids and cholesterol molecules helping
formation of cholesterol rich domains of saturated lipids as found in natural
membranes
Poly(ethylene oxide)-sodium dodecyl sulfate interactions studied using static and dynamic light scattering
Static and dynamic light scattering measurements have been made on poly(ethy1ene oxide)
(PEO) in the presence of the ionic surfactant sodium dodecyl sulfate (SDS) in aqueous solution over a range
of relative concentrations. The purpose was, in part, to demonstrate the polyelectrolyte effecte which arise
in PEO on formation of the charged complex between the components in solution in which small SDS micelles
are incorporated into the flexible PEO coil. The influence of the ionic strength of the medium was studied.
Static light scattering measurements show that the radius of gyration changes as a function of SDS concentration
and the ionic strength of the medium. Diffusion coefficients from dynamic light scattering (DLS) reflect
changes in the pair interaction potential as the SDS and ionic strength are altered. Laplace inversion of the
DLS time correlation function gives relaxation time distributions consisting of the PEO/SDS complex as the
main component and free SDS micelles as the minor component. Changes in peak areas are related to the
increase in the degree of binding between SDS and PEO as the relative concentrations change and also the
increase in SDS micellar size with increase in the ionic strength of the medium
Feasibility of near-unstable cavities for future gravitational wave detectors
Near-unstable cavities have been proposed as an enabling technology for
future gravitational wave detectors, as their compact structure and large beam
spots can reduce the coating thermal noise of the interferometer. We present a
tabletop experiment investigating the behaviour of an optical cavity as it is
parametrically pushed to geometrical instability. We report on the observed
degeneracies of the cavity's eigenmodes as the cavity becomes unstable and the
resonance conditions become hyper-sensitive to mirror surface imperfections. A
simple model of the cavity and precise measurements of the resonant frequencies
allow us to characterize the stability of the cavity and give an estimate of
the mirror astigmatism. The significance of these results for gravitational
wave detectors is discussed, and avenues for further research are suggested.Comment: 11 pages, 8 figure
CARMA CO(J = 2 - 1) Observations of the Circumstellar Envelope of Betelgeuse
We report radio interferometric observations of the 12C16O 1.3 mm J = 2-1
emission line in the circumstellar envelope of the M supergiant Alpha Ori and
have detected and separated both the S1 and S2 flow components for the first
time. Observations were made with the Combined Array for Research in
Millimeter-wave Astronomy (CARMA) interferometer in the C, D, and E antenna
configurations. We obtain good u-v coverage (5-280 klambda) by combining data
from all three configurations allowing us to trace spatial scales as small as
0.9\arcsec over a 32\arcsec field of view. The high spectral and spatial
resolution C configuration line profile shows that the inner S1 flow has
slightly asymmetric outflow velocities ranging from -9.0 km s-1 to +10.6 km s-1
with respect to the stellar rest frame. We find little evidence for the outer
S2 flow in this configuration because the majority of this emission has been
spatially-filtered (resolved out) by the array. We also report a SOFIA-GREAT
CO(J= 12-11) emission line profile which we associate with this inner higher
excitation S1 flow. The outer S2 flow appears in the D and E configuration maps
and its outflow velocity is found to be in good agreement with high resolution
optical spectroscopy of K I obtained at the McDonald Observatory. We image both
S1 and S2 in the multi-configuration maps and see a gradual change in the
angular size of the emission in the high absolute velocity maps. We assign an
outer radius of 4\arcsec to S1 and propose that S2 extends beyond CARMA's field
of view (32\arcsec at 1.3 mm) out to a radius of 17\arcsec which is larger than
recent single-dish observations have indicated. When azimuthally averaged, the
intensity fall-off for both flows is found to be proportional to R^{-1}, where
R is the projected radius, indicating optically thin winds with \rho \propto
R^{-2}.Comment: 11 pages, 8 figures To be published in the Astronomical Journal
(Received 2012 February 10; accepted 2012 May 25
Clinically speaking: A communication skills program for students from non-English speaking backgrounds
This paper reports on the design, delivery and evaluation of an innovative oral communication skills program for first year students in a Bachelor of Nursing degree at an Australian university. This program was introduced in 2004 to meet the needs of first year undergraduate students from non-English speaking backgrounds who had experienced difficulties with spoken English while on clinical placement. The program consisted of early identification of students in need of communication development, a series of classes incorporated into the degree program to address students' needs, followed by a clinical placement block. This paper describes the structure of the program, discusses some of the major problems encountered by students in the clinical setting and presents some of the teaching strategies used to address these problems. Evaluations of the program suggest that students' communication skills and confidence improved, resulting in a more positive clinical experience for the majority of students
Reflexive Modernization and the Disembedding of Budo: Judo from 1946 to the 2000 Sydney Olympics.
This article considers some of the sociologically significant changes to judo in its process of transformation from a Budo based martial art into a modern competitive spectator sport. Taking the period of time from 1946 until the Sydney Olympics, an examination is undertaken using Giddens's notion of reflexive modernization in which key aspects of the original judo are disembedded or 'lifted out' of the practice. They are then re-embedded with western structures, practices and meanings. Central themes to emerge from this analysis are the social forces of internationalization, institutionalization and commodification of judo over this period, each of which contributes to a reflexive modernization process. It is concluded that the evolution of this activity in its now dominant sporting form is taking judo further and further away from the aims, methods and ideas derived from the philosophical principles on which it was originally conceived. Ironically, in spite of this, it appears that many western practitioners are attempting to re-embed the very aspects of eastern movement forms, such as Budo, that have been disembedded, a situation that prompts us to call for further work in this area
Multiple Comorbid Conditions among Middle-Aged and Elderly Hemophilia Patients: Prevalence Estimates and Implications for Future Care
Introduction. Advances in hemophilia care and treatment have led to increases in the life expectancy among hemophiliacs. As a result, persons with hemophilia are reaching an older age and experiencing various age-related health conditions never seen before in this population. Aim. To determine the prevalence of comorbidities among middle-aged and elderly hemophilia A and hemophilia B patients. Methods. Retrospective chart review among all hemophilia patients, who attended the Gulf States Hemophilia and Thrombophilia Center. Results. All patients had at least one comorbid condition other than hemophilia, and the majority had between 3 and 6 comorbidities. The most common conditions identified were chronic hepatitis C, hypertension, HIV, chronic arthropathy, and overweight/obesity. Conclusions. Since persons with comorbidities are more likely to have poorer health outcomes and require greater care in managing their health needs, caring for aging hemophiliacs is likely to pose various social and economic challenges for both patients and providers
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