535 research outputs found
Stabilization of Ultracold Molecules Using Optimal Control Theory
In recent experiments on ultracold matter, molecules have been produced from
ultracold atoms by photoassociation, Feshbach resonances, and three-body
recombination. The created molecules are translationally cold, but
vibrationally highly excited. This will eventually lead them to be lost from
the trap due to collisions. We propose shaped laser pulses to transfer these
highly excited molecules to their ground vibrational level. Optimal control
theory is employed to find the light field that will carry out this task with
minimum intensity. We present results for the sodium dimer. The final target
can be reached to within 99% if the initial guess field is physically
motivated. We find that the optimal fields contain the transition frequencies
required by a good Franck-Condon pumping scheme. The analysis is able to
identify the ranges of intensity and pulse duration which are able to achieve
this task before other competing process take place. Such a scheme could
produce stable ultracold molecular samples or even stable molecular
Bose-Einstein condensates
Genomics reveals historic and contemporary transmission dynamics of a bacterial disease among wildlife and livestock
Whole-genome sequencing has provided fundamental insights into infectious disease epidemiology, but has rarely been used for examining transmission dynamics of a bacterial pathogen in wildlife. In the Greater Yellowstone Ecosystem (GYE), outbreaks of brucellosis have increased in cattle along with rising seroprevalence in elk. Here we use a genomic approach to examine Brucella abortus evolution, cross-species transmission and spatial spread in the GYE. We find that brucellosis was introduced into wildlife in this region at least five times. The diffusion rate varies among Brucella lineages (âŒ3 to 8âkm per year) and over time. We also estimate 12 host transitions from bison to elk, and 5 from elk to bison. Our results support the notion that free-ranging elk are currently a self-sustaining brucellosis reservoir and the source of livestock infections, and that control measures in bison are unlikely to affect the dynamics of unrelated strains circulating in nearby elk populations
The night-sky at the Calar Alto Observatory
We present a characterization of the main properties of the night-sky at the
Calar Alto observatory for the time period between 2004 and 2007. We use
optical spectrophotometric data, photometric calibrated images taken in
moonless observing periods, together with the observing conditions regularly
monitored at the observatory, such as atmospheric extinction and seeing. We
derive, for the first time, the typical moonless night-sky optical spectrum for
the observatory. The spectrum shows a strong contamination by different
pollution lines, in particular from Mercury lines, which contribution to the
sky-brightness in the different bands is of the order of ~0.09 mag, ~0.16 mag
and ~0.10 mag in B, V and R respectively. The zenith-corrected values of the
moonless night-sky surface brightness are 22.39, 22.86, 22.01, 21.36 and 19.25
mag arcsec^-2 in U, B, V, R and I, which indicates that Calar Alto is a
particularly dark site for optical observations up to the I-band. The fraction
of astronomical useful nights at the observatory is ~70%, with a ~30% of
photometric nights. The typical extinction at the observatory is k_V~0.15 mag
in the Winter season, with little dispersion. In summer the extinction has a
wider range of values, although it does not reach the extreme peaks observed at
other sites. The median seeing for the last two years (2005-6) was ~0.90",
being smaller in the Summer (~0.87") than in the Winter (~0.96"). We conclude
in general that after 26 years of operations Calar Alto is still a good
astronomical site, being a natural candidate for future large aperture optical
telescopes.Comment: 16 pages, 5 figures, accepted for publishing in the Publications of
Astronomical Society of the Pacific (PASP
Theory of Cylindrical Tubules and Helical Ribbons of Chiral Lipid Membranes
We present a general theory for the equilibrium structure of cylindrical
tubules and helical ribbons of chiral lipid membranes. This theory is based on
a continuum elastic free energy that permits variations in the direction of
molecular tilt and in the curvature of the membrane. The theory shows that the
formation of tubules and helical ribbons is driven by the chirality of the
membrane. Tubules have a first-order transition from a uniform state to a
helically modulated state, with periodic stripes in the tilt direction and
ripples in the curvature. Helical ribbons can be stable structures, or they can
be unstable intermediate states in the formation of tubules.Comment: 43 pages, including 12 postscript figures, uses REVTeX 3.0 and
epsf.st
Rigid Chiral Membranes
Statistical ensembles of flexible two-dimensional fluid membranes arise
naturally in the description of many physical systems. Typically one encounters
such systems in a regime of low tension but high stiffness against bending,
which is just the opposite of the regime described by the Polyakov string. We
study a class of couplings between membrane shape and in-plane order which
break 3-space parity invariance. Remarkably there is only {\it one} such
allowed coupling (up to boundary terms); this term will be present for any
lipid bilayer composed of tilted chiral molecules. We calculate the
renormalization-group behavior of this relevant coupling in a simplified model
and show how thermal fluctuations effectively reduce it in the infrared.Comment: 11 pages, UPR-518T (This replaced version has fonts not used
removed.
Transcriptomic analysis of cutaneous squamous cell carcinoma reveals a multi-gene prognostic signature associated with metastasis.
BackgroundMetastasis of cutaneous squamous cell carcinoma (cSCC) is uncommon. Current staging methods are reported to have sub-optimal performances in metastasis prediction. Accurate identification of patients with tumours at high risk of metastasis would have a significant impact on management.ObjectiveTo develop a robust and validated gene expression profile (GEP) signature for predicting primary cSCC metastatic risk using an unbiased whole transcriptome discovery-driven approach.MethodsArchival formalin-fixed paraffin-embedded primary cSCC with perilesional normal tissue from 237 immunocompetent patients (151 non-metastasising and 86 metastasising) were collected retrospectively from four centres. TempO-seq was used to probe the whole transcriptome and machine learning algorithms were applied to derive predictive signatures, with a 3:1 split for training and testing datasets.ResultsA 20-gene prognostic model was developed and validated, with an accuracy of 86.0%, sensitivity of 85.7%, specificity of 86.1%, and positive predictive value of 78.3% in the testing set, providing more stable, accurate prediction than pathological staging systems. A linear predictor was also developed, significantly correlating with metastatic risk.LimitationsThis was a retrospective 4-centre study and larger prospective multicentre studies are now required.ConclusionThe 20-gene signature prediction is accurate, with the potential to be incorporated into clinical workflows for cSCC
Genomics of Brucellosis in Wildlife and Livestock of the Greater Yellowstone Ecosystem
Brucellosis, a disease caused by the bacterium Brucella abortus, has recently been expanding its distribution in the Greater Yellowstone Ecosystem (GYE), with increased outbreaks in cattle and rising seroprevalence in elk (Cervus elaphus) over the past decade. Genetic studies suggest elk are a primary source of recent transmission to cattle. However, these studies are based on Variable Number Tandem Repeat (VNTR) data, which are limited in assessing and quantifying transmission among species. The goal of this study was to (i) investigate the introduction history of B. abortus in the GYE, (ii) identify B. abortus lineages associated with host species and/or geographic localities, and (iii) quantify transmission across wildlife and livestock host species and populations. We sequenced B. abortus whole genomes (n= 207) derived from isolates collected from three host species (bison, elk, cattle) over the past 30 years, throughout the GYE. We identified genetic variation among isolates, and applied a spatial diffusion phylogeographic modeling approach that incorporated temporal information from sampling. Based on these data, our results suggest four divergent Brucella lineages, with a time to most recent common ancestor of ~130 years ago, possibly representing a minimum of four brucellosis introductions into the GYE. Two Brucella lineages were generally clustered by geography. Evidence for cross-species transmission was detected among all species, though most events occur within species and herds. Understanding transmission dynamics is imperative for implementing effective control measures and may assist in identifying source populations responsible for past and future brucellosis infections in wildlife and outbreaks in livestock
Safety, efficacy, and immunogenicity of an inactivated influenza vaccine in healthy adults: a randomized, placebo-controlled trial over two influenza seasons
<p>Abstract</p> <p>Background</p> <p>Seasonal influenza imposes a substantial personal morbidity and societal cost burden. Vaccination is the major strategy for influenza prevention; however, because antigenically drifted influenza A and B viruses circulate annually, influenza vaccines must be updated to provide protection against the predicted prevalent strains for the next influenza season. The aim of this study was to assess the efficacy, safety, reactogenicity, and immunogenicity of a trivalent inactivated split virion influenza vaccine (TIV) in healthy adults over two influenza seasons in the US.</p> <p>Methods</p> <p>The primary endpoint of this double-blind, randomized study was the average efficacy of TIV versus placebo for the prevention of vaccine-matched, culture-confirmed influenza (VMCCI) across the 2005-2006 and 2006-2007 influenza seasons. Secondary endpoints included the prevention of laboratory-confirmed (defined by culture and/or serology) influenza, as well as safety, reactogenicity, immunogenicity, and consistency between three consecutive vaccine lots. Participants were assessed actively during both influenza seasons, and nasopharyngeal swabs were collected for viral culture from individuals with influenza-like illness. Blood specimens were obtained for serology one month after vaccination and at the end of each influenza season's surveillance period.</p> <p>Results</p> <p>Although the point estimate for efficacy in the prevention of all laboratory-confirmed influenza was 63.2% (97.5% confidence interval [CI] lower bound of 48.2%), the point estimate for the primary endpoint, efficacy of TIV against VMCCI across both influenza seasons, was 46.3% with a 97.5% CI lower bound of 9.8%. This did not satisfy the pre-specified success criterion of a one-sided 97.5% CI lower bound of >35% for vaccine efficacy. The VMCCI attack rates were very low overall at 0.6% and 1.2% in the TIV and placebo groups, respectively. Apart from a mismatch for influenza B virus lineage in 2005-2006, there was a good match between TIV and the circulating strains. TIV was highly immunogenic, and immune responses were consistent between three different TIV lots. The most common reactogenicity events and spontaneous adverse events were associated with the injection site, and were mild in severity.</p> <p>Conclusions</p> <p>Despite a good immune response, and an average efficacy over two influenza seasons against laboratory-confirmed influenza of 63.2%, the pre-specified target (lower one-sided 97.5% confidence bound for efficacy > 35%) for the primary efficacy endpoint, the prevention of VMCCI, was not met. However, the results should be interpreted with caution in view of the very low attack rates we observed at the study sites in the 2005-2006 and 2006-2007, which corresponded to relatively mild influenza seasons in the US. Overall, the results showed that TIV has an acceptable safety profile and offered clinical benefit that exceeded risk.</p> <p>Trial registration</p> <p>NCT00216242</p
Transcriptomic analysis of cutaneous squamous cell carcinoma reveals a multi-gene prognostic signature associated with metastasis.
BACKGROUND: Metastasis of cutaneous squamous cell carcinoma (cSCC) is uncommon. Current staging methods are reported to have sub-optimal performances in metastasis prediction. Accurate identification of patients with tumours at high risk of metastasis would have a significant impact on management. OBJECTIVE: To develop a robust and validated gene expression profile (GEP) signature for predicting primary cSCC metastatic risk using an unbiased whole transcriptome discovery-driven approach. METHODS: Archival formalin-fixed paraffin-embedded primary cSCC with perilesional normal tissue from 237 immunocompetent patients (151 non-metastasising and 86 metastasising) were collected retrospectively from four centres. TempO-seq was used to probe the whole transcriptome and machine learning algorithms were applied to derive predictive signatures, with a 3:1 split for training and testing datasets. RESULTS: A 20-gene prognostic model was developed and validated, with an accuracy of 86.0%, sensitivity of 85.7%, specificity of 86.1%, and positive predictive value of 78.3% in the testing set, providing more stable, accurate prediction than pathological staging systems. A linear predictor was also developed, significantly correlating with metastatic risk. LIMITATIONS: This was a retrospective 4-centre study and larger prospective multicentre studies are now required. CONCLUSION: The 20-gene signature prediction is accurate, with the potential to be incorporated into clinical workflows for cSCC
Toward the clinical application of time-domain fluorescence lifetime imaging
High-speed (video-rate) fluorescence lifetime imaging (FLIM) through a flexible endoscope is reported based on gated optical image intensifier technology. The optimization and potential application of FLIM to tissue autofluorescence for clinical applications are discussed. (c) 2005 Society of Photo-Optical Instrumentation Engineers
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