4,005 research outputs found
A novel laser ranging system for measurement of ground-to-satellite distances
A technique was developed for improving the precision of laser ranging measurements of ground-to-satellite distances. The method employs a mode-locked laser transmitter and utilizes an image converter tube equipped with deflection plates in measuring the time of flight of the laser pulse to a distant retroreflector and back. Samples of the outgoing and returning light pulses are focussed on the photocathode of the image converter tube, whose deflection plates are driven by a high-voltage 120 MHz sine wave derived from a very stable oscillator. From the relative positions of the images produced at the output phosphor by the two light pulses, it is possible to make a precise determination of the fractional amount by which the time of flight exceeds some large integral multiple of the period of the deflection sinusoid
Hydrocarbon phenotyping of algal species using pyrolysis-gas chromatography mass spectrometry
<p>Abstract</p> <p>Background</p> <p>Biofuels derived from algae biomass and algae lipids might reduce dependence on fossil fuels. Existing analytical techniques need to facilitate rapid characterization of algal species by phenotyping hydrocarbon-related constituents.</p> <p>Results</p> <p>In this study, we compared the hydrocarbon rich algae <it>Botryococcus braunii </it>against the photoautotrophic model algae <it>Chlamydomonas reinhardtii </it>using pyrolysis-gas chromatography quadrupole mass spectrometry (pyGC-MS). Sequences of up to 48 dried samples can be analyzed using pyGC-MS in an automated manner without any sample preparation. Chromatograms of 30-min run times are sufficient to profile pyrolysis products from C8 to C40 carbon chain length. The freely available software tools AMDIS and SpectConnect enables straightforward data processing. In <it>Botryococcus </it>samples, we identified fatty acids, vitamins, sterols and fatty acid esters and several long chain hydrocarbons. The algae species <it>C. reinhardtii, B. braunii </it>race A and <it>B. braunii </it>race B were readily discriminated using their hydrocarbon phenotypes. Substructure annotation and spectral clustering yielded network graphs of similar components for visual overviews of abundant and minor constituents.</p> <p>Conclusion</p> <p>Pyrolysis-GC-MS facilitates large scale screening of hydrocarbon phenotypes for comparisons of strain differences in algae or impact of altered growth and nutrient conditions.</p
Regional differences in health status in China : population health-related quality of life results from the National Health Services Survey 2008
Purpose: to measure, describe and analyse regional differences in health-related quality of life measured by EQ-5D in China. Data were obtained via face-to-face interviews on a national representative sample (n=120,703, 15-103 years). The EQ-5D instrument was used to measure health status.
Results: Rural areas had worse health status than urban areas. Health status was worst in western areas and best in eastern areas, and such disparities were profounder in rural areas. In urban areas, health status was best in middle-sized cities. In rural areas, health status increased with the economic development level of a county.
Conclusion: Our study enhances understanding of the urban-rural differences and east-middle-west differences in health and sheds light on inequalities in health status between different city categories in the urban areas and county categories in the rural areas.Swedish Research CouncilEuroQol Excutive OfficeAccepte
Dynamical elastic bodies in Newtonian gravity
Well-posedness for the initial value problem for a self-gravitating elastic
body with free boundary in Newtonian gravity is proved. In the material frame,
the Euler-Lagrange equation becomes, assuming suitable constitutive properties
for the elastic material, a fully non-linear elliptic-hyperbolic system with
boundary conditions of Neumann type. For systems of this type, the initial data
must satisfy compatibility conditions in order to achieve regular solutions.
Given a relaxed reference configuration and a sufficiently small Newton's
constant, a neigborhood of initial data satisfying the compatibility conditions
is constructed
Potential Energy Landscape and Long Time Dynamics in a Simple Model Glass
We analyze the properties of a Lennard-Jones system at the level of the
potential energy landscape. After an exhaustive investigation of the
topological features of the landscape of the systems, obtained studying small
size sample, we describe the dynamics of the systems in the multi-dimensional
configurational space by a simple model. This consider the configurational
space as a connected network of minima where the dynamics proceeds by jumps
described by an appropriate master equation. Using this model we are able to
reproduce the long time dynamics and the low temperature regime. We investigate
both the equilibrium regime and the off-equilibrium one, finding those typical
glassy behavior usually observed in the experiments such as: {\it i)} stretched
exponential relaxation, {\it ii)} temperature-dependent stretching parameter,
{\it iii)} breakdown of the Stokes-Einstein relation, and {\it iv)} appearance
of a critical temperature below which one observes deviation from the
fluctuation-dissipation relation as consequence of the lack of equilibrium in
the system.Comment: 11 pages (Latex), 9 ps figure
Connected Network of Minima as a Model Glass: Long Time Dynamics
A simple model to investigate the long time dynamics of glass-formers is
presented and applied to study a Lennard-Jones system in supercooled and glassy
phases. According to our model, the point representing the system in the
configurational phase space performs harmonic vibrations around (and activated
jumps between) minima pertaining to a connected network. Exploiting the model,
in agreement with the experimental results, we find evidence for: i) stretched
relaxational dynamics; ii) a strong T-dependence of the stretching parameter;
iii) breakdown of the Stokes-Einstein law.Comment: 4 pages (Latex), 4 eps figure
Recommended from our members
Health-related quality of life in Huntingtonâs Disease patients: a comparison of proxy assessment and patient self-rating using the disease-specific Huntingtonâs Disease health-related quality of life questionnaire (HDQoL)
Huntingtonâs disease (HD) is a fatal, neurodegenerative disease for which there is no known cure. Proxy evaluation is relevant for HD as its manifestation might limit the ability of persons to report their health-related quality of life (HrQoL). This study explored patientâproxy ratings of HrQoL of persons at different stages of HD, and examined factors that may affect proxy ratings. A total of 105 patientâproxy pairs completed the Huntingtonâs disease health-related quality of life questionnaire (HDQoL) and other established HrQoL measures (EQ-5D and SF-12v2). Proxyâpatient agreement was assessed in terms of absolute level (mean ratings) and intraclass correlation. Proxiesâ ratings were at a similar level to patientsâ self-ratings on an overall Summary Score and on most of the six Specific Scales of the HDQoL. On the Specific Hopes and Worries Scale, proxies on average rated HrQoL as better than patientsâ self-ratings, while on both the Specific Cognitive Scale and Specific Physical and Functional Scale proxies tended to rate HrQoL more poorly than patients themselves. The patientâs disease stage and mental wellbeing (SF-12 Mental Component scale) were the two factors that primarily affected proxy assessment. Proxy scores were strongly correlated with patientsâ self-ratings of HrQoL, on the Summary Scale and all Specific Scales. The patientâproxy correlation was lower for patients at moderate stages of HD compared to patients at early and advanced stages. The proxy report version of the HDQoL is a useful complementary tool to self-assessment, and a promising alternative when individual patients with advanced HD are unable to self-report
Astrometric calibration and performance of the Dark Energy Camera
We characterize the ability of the Dark Energy Camera (DECam) to perform
relative astrometry across its 500~Mpix, 3 deg^2 science field of view, and
across 4 years of operation. This is done using internal comparisons of ~4x10^7
measurements of high-S/N stellar images obtained in repeat visits to fields of
moderate stellar density, with the telescope dithered to move the sources
around the array. An empirical astrometric model includes terms for: optical
distortions; stray electric fields in the CCD detectors; chromatic terms in the
instrumental and atmospheric optics; shifts in CCD relative positions of up to
~10 um when the DECam temperature cycles; and low-order distortions to each
exposure from changes in atmospheric refraction and telescope alignment. Errors
in this astrometric model are dominated by stochastic variations with typical
amplitudes of 10-30 mas (in a 30 s exposure) and 5-10 arcmin coherence length,
plausibly attributed to Kolmogorov-spectrum atmospheric turbulence. The size of
these atmospheric distortions is not closely related to the seeing. Given an
astrometric reference catalog at density ~0.7 arcmin^{-2}, e.g. from Gaia, the
typical atmospheric distortions can be interpolated to 7 mas RMS accuracy (for
30 s exposures) with 1 arcmin coherence length for residual errors. Remaining
detectable error contributors are 2-4 mas RMS from unmodelled stray electric
fields in the devices, and another 2-4 mas RMS from focal plane shifts between
camera thermal cycles. Thus the astrometric solution for a single DECam
exposure is accurate to 3-6 mas (0.02 pixels, or 300 nm) on the focal plane,
plus the stochastic atmospheric distortion.Comment: Submitted to PAS
Sexual orientation and symptoms of common mental disorder or low wellbeing: combined meta-analysis of 12 UK population health surveys
Background Previous studies have indicated increased risk of mental disorder symptoms, suicide and substance misuse in lesbian, gay and bisexual (LGB) adults, compared to heterosexual adults. Our aims were to determine an estimate of the association between sexual orientation identity and poor mental health and wellbeing among adults from 12 population surveys in the UK, and to consider whether effects differed for specific subgroups of the population. Methods Individual data were pooled from the British Cohort Study 2012, Health Survey for England 2011, 2012 and 2013, Scottish Health Survey 2008 to 2013, Longitudinal Study of Young People in England 2009/10 and Understanding Society 2011/12. Individual participant meta-analysis was used to pool estimates from each study, allowing for between-study variation. Results Of 94,818 participants, 1.1 % identified as lesbian/gay, 0.9 % as bisexual, 0.8 % as âotherâ and 97.2 % as heterosexual. Adjusting for a range of covariates, adults who identified as lesbian/gay had higher prevalence of common mental disorder when compared to heterosexuals, but the association was different in different age groups: apparent for those under 35 (ORâ=â1.78, 95 % CI 1.40, 2.26), weaker at age 35â54.9 (ORâ=â1.42, 95 % CI 1.10, 1.84), but strongest at age 55+ (ORâ=â2.06, 95 % CI 1.29, 3.31). These effects were stronger for bisexual adults, similar for those identifying as âotherâ, and similar for 'low wellbeing'. Conclusions In the UK, LGB adults have higher prevalence of poor mental health and low wellbeing when compared to heterosexuals, particularly younger and older LGB adults. Sexual orientation identity should be measured routinely in all health studies and in administrative data in the UK in order to influence national and local policy development and service delivery. These results reiterate the need for local government, NHS providers and public health policy makers to consider how to address inequalities in mental health among these minority groups
- âŠ