177 research outputs found
The electroclinic effect and modulated phases in smectic liquid crystals
We explore the possibility that the large electroclinic effect observed in
ferroelectric liquid crystals arises from the presence of an ordered array of
disclination lines and walls. If the spacing of these defects is in the
subvisible range, this modulated phase would be similar macroscopically to a
smectic A phase. The application of an electric field distorts the array,
producing a large polarization, and hence a large electroclinic effect. We show
that with suitable elastic parameters and sufficiently large chirality, the
modulated phase is favored over the smectic A and helically twisted smectic C*
phases. We propose various experimental tests of this scenario.Comment: 9 pages, 7 figures; new version includes dipolar interactions and
bend-twist couplin
Cary's Response to Rapid Growth: Reflections Upon Twenty Years of Change
In preparation for this issue on politics and planning, Carolina Planning issued a call for papers from practicing planners in North Carolina who hold or have held elective office. In response, Robert Hinshaw, economic development section chief in the state Division of Community Assistance and former member of the Cary Town Council and Cary Planning and Zoning Board, shares his insights in this article on the role of the planner in these positions
Laparoscopic simulation training in gynaecology:Current provision and staff attitudes - a cross-sectional survey
<p>The objectives of this study were to explore current provision of laparoscopic simulation training, and to determine attitudes of trainers and trainees to the role of simulators in surgical training across the UK. An anonymous cross-sectional survey with cluster sampling was developed and circulated. All Royal College of Obstetricians and Gynaecologists (RCOG) Training Programme Directors (TPD), College Tutors (RCT) and Trainee representatives (TR) across the UK were invited to participate. One hundred and ninety-six obstetricians and gynaecologists participated. Sixty-three percent of hospitals had at least one box trainer, and 14.6% had least one virtual-reality simulator. Only 9.3% and 3.6% stated that trainees used a structured curriculum on box and virtual-reality simulators, respectively. Respondents working in a Large/Teaching hospital (<i>p</i> = 0.008) were more likely to agree that simulators enhance surgical training. Eighty-nine percent agreed that simulators improve the quality of training, and should be mandatory or desirable for junior trainees. Consultants (<i>p</i> = 0.003) and respondents over 40 years (<i>p</i> = 0.011) were more likely to hold that a simulation test should be undertaken before live operation. Our data demonstrated, therefore, that availability of laparoscopic simulators is inconsistent, with limited use of mandatory structured curricula. In contrast, both trainers and trainees recognise a need for greater use of laparoscopic simulation for surgical training.</p
Testing Standard Cosmology with Large Scale Structure
The galaxy power spectrum contains information on the growth of structure,
the growth rate through redshift space distortions, and the cosmic expansion
through baryon acoustic oscillation features. We study the ability of two
proposed experiments, BigBOSS and JDEM-PS, to test the cosmological model and
general relativity. We quantify the latter result in terms of the gravitational
growth index \gamma, whose value in general relativity is \gamma\approx 0.55.
Significant deviations from this value could indicate new physics beyond the
standard model of cosmology. The results show that BigBOSS (JDEM-PS) would be
capable of measuring \gamma with an uncertainty \sigma(\gamma) = 0.043 (0.054),
which tightens to \sigma(\gamma) = 0.031 (0.038) if we include Stage III data
priors, marginalizing over neutrino mass, time varying dark energy equation of
state, and other parameters. For all dark energy parameters and related figures
of merit the two experiments give comparable results. We also carry out some
studies of the influence of redshift range, resolution, treatment of
nonlinearities, and bias evolution to enable further improvement.Comment: 9 pages, 12 tables, 1 figure; v3 matches MNRAS accepted versio
Bayesian model comparison in cosmology with Population Monte Carlo
We use Bayesian model selection techniques to test extensions of the standard
flat LambdaCDM paradigm. Dark-energy and curvature scenarios, and primordial
perturbation models are considered. To that end, we calculate the Bayesian
evidence in favour of each model using Population Monte Carlo (PMC), a new
adaptive sampling technique which was recently applied in a cosmological
context. The Bayesian evidence is immediately available from the PMC sample
used for parameter estimation without further computational effort, and it
comes with an associated error evaluation. Besides, it provides an unbiased
estimator of the evidence after any fixed number of iterations and it is
naturally parallelizable, in contrast with MCMC and nested sampling methods. By
comparison with analytical predictions for simulated data, we show that our
results obtained with PMC are reliable and robust. The variability in the
evidence evaluation and the stability for various cases are estimated both from
simulations and from data. For the cases we consider, the log-evidence is
calculated with a precision of better than 0.08.
Using a combined set of recent CMB, SNIa and BAO data, we find inconclusive
evidence between flat LambdaCDM and simple dark-energy models. A curved
Universe is moderately to strongly disfavoured with respect to a flat
cosmology. Using physically well-motivated priors within the slow-roll
approximation of inflation, we find a weak preference for a running spectral
index. A Harrison-Zel'dovich spectrum is weakly disfavoured. With the current
data, tensor modes are not detected; the large prior volume on the
tensor-to-scalar ratio r results in moderate evidence in favour of r=0.
[Abridged]Comment: 11 pages, 6 figures. Matches version accepted for publication by
MNRA
AACAP 2006 Research Forum--Advancing research in early-onset bipolar disorder: barriers and suggestions
OBJECTIVE: The 2006 Research Forum addressed the goal of formulating a research agenda for early-onset bipolar disorder (EOBP) and improving outcome by understanding the risk and protective factors that contribute to its severity and chronicity.
METHOD: Five work groups outlined barriers and research gaps in EOBP genetics, neuroimaging, prodromes, psychosocial factors, and pharmacotherapy.
RESULTS: There was agreement that the lack of consensus on the definition and diagnosis of EOBP is the primary barrier to advancing research in BP in children and adolescents. Related issues included: the difficulties in managing co-morbidity both statistically and clinically; acquiring adequate sample sizes to study the genetics, biology, and treatment; understanding the EOBP\u27s developmental aspects; and identifying environmental mediators and moderators of risk and protection. Similarly, both psychosocial and medication treatment strategies for children with BP are hamstrung by diagnostic issues. To advance the research in EOBP, both training and funding mechanisms need to be developed with these issues in mind.
CONCLUSIONS: EOBP constitutes a significant public health concern. Barriers are significant but identifiable and thus are not insurmountable. To advance the understanding of EOBP, the field must be committed to resolving diagnostic and assessment issues. Once achieved, with adequate personnel and funding resources, research into the field of EOBP will doubtless be advanced at a rapid pace
Observational Constraints on Theories with a Blue Spectrum of Tensor Modes
Motivated by the string gas cosmological model, which predicts a blue tilt of
the primordial gravitational wave spectrum, we examine the constraints imposed
by current and planned observations on a blue tilted tensor spectrum. Starting
from an expression for the primordial gravitational wave spectrum normalized
using cosmic microwave background observations, pulsar timing, direct detection
and nucleosynthesis bounds are examined. If we assume a tensor to scalar ratio
on scales of the CMB which equals the current observational upper bound, we
obtain from these current observations constraints on the tensor spectral index
of , , and
respectively.Comment: 12 pages, 1 figure, 2 references added, relationship of this work
with Ref. 20 adde
Exile Vol. XXIX No. 1
Once by Kate Silliman 1
Mute by Robert Youngblood 1
Photo by Walter Gunn 2
Cactus Man by Bruce Pedretti 3
From Years On Nauset Beach by 4
Lazy Days of The Matter That Fills You With Guild (And Ecstacy) by Eric Stevenson 5
Tennessee Friday by Becky Hinshaw 6
Photo by Jenny Gardner 7
Street Opera by Bill Hayes 7
Antonia by Ruth Wick 8
Photo by Sheila Waters 9
Tunnel Vision by Jeff Reynold 10
Mrs. Matthews by Kate Reynolds 10
A White Mountain by Ruth Wick 11
The Last Days Of Oliver Descantes by Jeff Hamilton 12-23
Photo by Christopher Hooper 24
Baptism by Becky Hinshaw 25
Sunday Afternoon by August West 26
The Joke\u27s On by Christopher B. Broughm 26
Photo by Mark Baganz 27
Blues by Dave Rheingold 28
Speaking To You Through Derision by Jeff Hamilton 29
Photo by Jenny Gardner 30
Northern Lights by Adrienne Wehr 31
Tripping On The Yawn Of Tomorrow by Kate Reynolds 32
Cleo by Kim Kiefer 33
Kuei Mei by Amy Pence 34
Drawing by Peter Brooke 35
Cover Drawing by Peter Brooke -title pag
High sensitivity measurements of the CMB power spectrum with the extended Very Small Array
We present deep Ka-band ( GHz) observations of the CMB made
with the extended Very Small Array (VSA). This configuration produces a
naturally weighted synthesized FWHM beamwidth of arcmin which covers
an -range of 300 to 1500. On these scales, foreground extragalactic
sources can be a major source of contamination to the CMB anisotropy. This
problem has been alleviated by identifying sources at 15 GHz with the Ryle
Telescope and then monitoring these sources at 33 GHz using a single baseline
interferometer co-located with the VSA. Sources with flux densities \gtsim 20
mJy at 33 GHz are subtracted from the data. In addition, we calculate a
statistical correction for the small residual contribution from weaker sources
that are below the detection limit of the survey.
The CMB power spectrum corrected for Galactic foregrounds and extragalactic
point sources is presented. A total -range of 150-1500 is achieved by
combining the complete extended array data with earlier VSA data in a compact
configuration. Our resolution of allows the first 3
acoustic peaks to be clearly delineated. The is achieved by using mosaiced
observations in 7 regions covering a total area of 82 sq. degrees. There is
good agreement with WMAP data up to where WMAP data run out of
resolution. For higher -values out to , the agreement in
power spectrum amplitudes with other experiments is also very good despite
differences in frequency and observing technique.Comment: 16 pages. Accepted in MNRAS (minor revisions
Spatial variation in the fine-structure constant -- new results from VLT/UVES
(abridged) We present a new analysis of a large sample of quasar
absorption-line spectra obtained using UVES (the Ultraviolet and Visual Echelle
Spectrograph) on the VLT (Very Large Telescope) in Chile. In the VLT sample
(154 absorbers), we find evidence that alpha increases with increasing
cosmological distance from Earth. However, as previously shown, the Keck sample
(141 absorbers) provided evidence for a smaller alpha in the distant absorption
clouds. Upon combining the samples an apparent variation of alpha across the
sky emerges which is well represented by an angular dipole model pointing in
the direction RA=(17.3 +/- 1.0) hr, dec. = (-61 +/- 10) deg, with amplitude
(0.97 +0.22/-0.20) x 10^(-5). The dipole model is required at the 4.1 sigma
statistical significance level over a simple monopole model where alpha is the
same across the sky (but possibly different to the current laboratory value).
The data sets reveal a number of remarkable consistencies: various data cuts
are consistent and there is consistency in the overlap region of the Keck and
VLT samples. Assuming a dipole-only (i.e. no-monopole) model whose amplitude
grows proportionally with `lookback-time distance' (r=ct, where t is the
lookback time), the amplitude is (1.1 +/- 0.2) x 10^(-6) GLyr^(-1) and the
model is significant at the 4.2 sigma confidence level over the null model
[Delta alpha]/alpha = 0). We apply robustness checks and demonstrate that the
dipole effect does not originate from a small subset of the absorbers or
spectra. We present an analysis of systematic effects, and are unable to
identify any single systematic effect which can emulate the observed variation
in alpha.Comment: 47 pages, 35 figures. Accepted for publication by Monthly Notices of
the Royal Astronomical Society. Please see
http://astronomy.swin.edu.au/~mmurphy/pub.html for an ASCII version of table
A1 and the full set of Voigt profile fits for appendix
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