872 research outputs found
Total and dissociative photoionization cross sections of N2 from threshold to 107 eV
The absolute cross sections for the production of N(+) and N2(+) were measured from the dissociative ionization threshold of 115 A. In addition, the absolute photoabsorption and photoionization cross sections were tabulated between 114 and 796 A. The ionization efficiencies were also given at several discrete wave lengths between 660 and 790 A. The production of N(+) fragment ions are discussed in terms of the doubly excited N2(+) states with binding energies in the range of 24 to 44 eV
Telescope to Observe Planetary Systems (TOPS): a high throughput 1.2-m visible telescope with a small inner working angle
The Telescope to Observe Planetary Systems (TOPS) is a proposed space mission
to image in the visible (0.4-0.9 micron) planetary systems of nearby stars
simultaneously in 16 spectral bands (resolution R~20). For the ~10 most
favorable stars, it will have the sensitivity to discover 2 R_E rocky planets
within habitable zones and characterize their surfaces or atmospheres through
spectrophotometry. Many more massive planets and debris discs will be imaged
and characterized for the first time. With a 1.2m visible telescope, the
proposed mission achieves its power by exploiting the most efficient and robust
coronagraphic and wavefront control techniques. The Phase-Induced Amplitude
Apodization (PIAA) coronagraph used by TOPS allows planet detection at 2
lambda/d with nearly 100% throughput and preserves the telescope angular
resolution. An efficient focal plane wavefront sensing scheme accurately
measures wavefront aberrations which are fed back to the telescope active
primary mirror. Fine wavefront control is also performed independently in each
of 4 spectral channels, resulting in a system that is robust to wavefront
chromaticity.Comment: 12 pages, SPIE conference proceeding, May 2006, Orlando, Florid
Cardiac Resynchronization With Sequential Biventricular Pacing for the Treatment of Moderate-to-Severe Heart Failure
ObjectivesThe InSync III study evaluated sequential cardiac resynchronization therapy (CRT) in patients with moderate-to-severe heart failure and prolonged QRS.BackgroundSimultaneous CRT improves hemodynamic and clinical performance in patients with moderate-to-severe heart failure (HF) and a wide QRS. Recent evidence suggests that sequentially stimulating the ventricles might provide additional benefit.MethodsThis multicenter, prospective, nonrandomized, six-month trial enrolled a total of 422 patients to determine the effectiveness of sequential CRT in patients with New York Heart Association (NYHA) functional class III or IV HF and a prolonged QRS. The study evaluated: whether patients receiving sequential CRT for six months experienced improvement in 6-min hall walk (6MHW) distance, NYHA functional class, and quality of life (QoL) over control group patients from the reported Multicenter InSync Randomized Clinical Evaluation (MIRACLE) trial; whether sequential CRT increased stroke volume compared to simultaneous CRT; and whether an increase in stroke volume translated into greater clinical improvements compared to patients receiving simultaneous CRT.ResultsInSync III patients experienced greater improvement in 6MHW, NYHA functional class, and QoL at six months compared to control (all p < 0.0001). Optimization of the sequential pacing increased (median 7.3%) stroke volume in 77% of patients. No additional improvement in NYHA functional class or QoL was seen compared to the simultaneous CRT group; however, InSync III patients demonstrated greater exercise capacity.ConclusionsSequential CRT provided most patients with a modest increase in stroke volume above that achieved during simultaneous CRT. Patients receiving sequential CRT had improved exercise capacity, but no change in functional status or QoL
TOPS: a small space telescope using phase induced-amplitude apodization (PIAA) to image rocky and giant exo-planets
The Telescope to Observe Planetary Systems (TOPS) is a proposed space mission to image planetary systems of nearby stars simultaneously in a few wide spectral bands covering the visible light (0.4-0.9 μm). It achieves its power by combining a high accuracy wavefront control system with a highly efficient Phase-Induced Amplitude Apodization (PIAA) coronagraph which provides strong suppression very close to the star (within 2 λ/D). The PIAA coronagraphic technique opens the possibility of imaging Earthlike planets in visible light with a smaller telescope than previously supposed. If sized at 1.2-m, TOPS would image and characterize many Jupiter-sized planets, and discover 2 RE rocky planets within habitable zones of the ≈10 most favorable stars. With a larger 2-m aperture, TOPS would have the sensitivity to reveal Earth-like planets in the habitable zone around ≈20 stars, and to characterize any found with low resolution spectroscopy. Unless the occurrence of Earth-like planets is very low (η⊕ <~ 0.2), a useful fraction of the TPF-C scientific program would be possible with aperture much smaller than the baselined 8 by 3.5m for TPF, with its more conventional coronagraph. An ongoing laboratory experiment has successfully demonstrated high contrast coronagraphic imaging within 2 λ/d with the PIAA coronagraph / focal plane wavefront sensing scheme envisioned for TOPS
LSST Science Book, Version 2.0
A survey that can cover the sky in optical bands over wide fields to faint
magnitudes with a fast cadence will enable many of the exciting science
opportunities of the next decade. The Large Synoptic Survey Telescope (LSST)
will have an effective aperture of 6.7 meters and an imaging camera with field
of view of 9.6 deg^2, and will be devoted to a ten-year imaging survey over
20,000 deg^2 south of +15 deg. Each pointing will be imaged 2000 times with
fifteen second exposures in six broad bands from 0.35 to 1.1 microns, to a
total point-source depth of r~27.5. The LSST Science Book describes the basic
parameters of the LSST hardware, software, and observing plans. The book
discusses educational and outreach opportunities, then goes on to describe a
broad range of science that LSST will revolutionize: mapping the inner and
outer Solar System, stellar populations in the Milky Way and nearby galaxies,
the structure of the Milky Way disk and halo and other objects in the Local
Volume, transient and variable objects both at low and high redshift, and the
properties of normal and active galaxies at low and high redshift. It then
turns to far-field cosmological topics, exploring properties of supernovae to
z~1, strong and weak lensing, the large-scale distribution of galaxies and
baryon oscillations, and how these different probes may be combined to
constrain cosmological models and the physics of dark energy.Comment: 596 pages. Also available at full resolution at
http://www.lsst.org/lsst/sciboo
LSST: from Science Drivers to Reference Design and Anticipated Data Products
(Abridged) We describe here the most ambitious survey currently planned in
the optical, the Large Synoptic Survey Telescope (LSST). A vast array of
science will be enabled by a single wide-deep-fast sky survey, and LSST will
have unique survey capability in the faint time domain. The LSST design is
driven by four main science themes: probing dark energy and dark matter, taking
an inventory of the Solar System, exploring the transient optical sky, and
mapping the Milky Way. LSST will be a wide-field ground-based system sited at
Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m
effective) primary mirror, a 9.6 deg field of view, and a 3.2 Gigapixel
camera. The standard observing sequence will consist of pairs of 15-second
exposures in a given field, with two such visits in each pointing in a given
night. With these repeats, the LSST system is capable of imaging about 10,000
square degrees of sky in a single filter in three nights. The typical 5
point-source depth in a single visit in will be (AB). The
project is in the construction phase and will begin regular survey operations
by 2022. The survey area will be contained within 30,000 deg with
, and will be imaged multiple times in six bands, ,
covering the wavelength range 320--1050 nm. About 90\% of the observing time
will be devoted to a deep-wide-fast survey mode which will uniformly observe a
18,000 deg region about 800 times (summed over all six bands) during the
anticipated 10 years of operations, and yield a coadded map to . The
remaining 10\% of the observing time will be allocated to projects such as a
Very Deep and Fast time domain survey. The goal is to make LSST data products,
including a relational database of about 32 trillion observations of 40 billion
objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures
available from https://www.lsst.org/overvie
Genetic association study of QT interval highlights role for calcium signaling pathways in myocardial repolarization.
The QT interval, an electrocardiographic measure reflecting myocardial repolarization, is a heritable trait. QT prolongation is a risk factor for ventricular arrhythmias and sudden cardiac death (SCD) and could indicate the presence of the potentially lethal mendelian long-QT syndrome (LQTS). Using a genome-wide association and replication study in up to 100,000 individuals, we identified 35 common variant loci associated with QT interval that collectively explain ∼8-10% of QT-interval variation and highlight the importance of calcium regulation in myocardial repolarization. Rare variant analysis of 6 new QT interval-associated loci in 298 unrelated probands with LQTS identified coding variants not found in controls but of uncertain causality and therefore requiring validation. Several newly identified loci encode proteins that physically interact with other recognized repolarization proteins. Our integration of common variant association, expression and orthogonal protein-protein interaction screens provides new insights into cardiac electrophysiology and identifies new candidate genes for ventricular arrhythmias, LQTS and SCD
Free text adversity statements as part of a contextualised admissions process:a qualitative analysis
Abstract Background Medical schools globally are encouraged to widen access and participation for students from less privileged backgrounds. Many strategies have been implemented to address this inequality, but much still needs to be done to ensure fair access for all. In the literature, adverse circumstances include financial issues, poor educational experience and lack of professional-status parents. In order to take account of adverse circumstances faced by applicants, The University of Dundee School of Medicine offers applicants the opportunity to report circumstances which may have resulted in disadvantage. Applicants do this by completing a free text statement, known as an ‘adversity statement’, in addition to the other application information. This study analysed adversity statements submitted by applicants during two admissions cycles. Analysis of content and theme was done to identify the information applicants wished to be taken into consideration, and what range of adverse circumstances individuals reported. Methods This study used a qualitative approach with thematic analysis to categorise the adversity statements. The data was initially analysed to create a coding framework which was then applied to the whole data set. Each coded segment was then analysed for heterogeneity and homogeneity, segments merged into generated themes, or to create sub-themes. Results The data set comprised a total of 384 adversity statements. These showed a wide range of detail involving family, personal health, education and living circumstances. Some circumstances, such as geographical location, have been identified and explored in previous research, while others, such as long term health conditions, have had less attention in the literature. The degree of impact, the length of statement and degree of detail, demonstrated wide variation between submissions. Conclusions This study adds to the debate on best practice in contextual admissions and raises awareness of the range of circumstances and impact applicants wish to be considered. The themes which emerged from the data included family, school, personal health, and geographical location issues. Descriptions of the degree of impact that an adverse circumstance had on educational or other attainment was found to vary substantially from statements indicating minor, impact through to circumstances stated as causing major impact
The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment
The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in
operation since July 2014. This paper describes the second data release from
this phase, and the fourteenth from SDSS overall (making this, Data Release
Fourteen or DR14). This release makes public data taken by SDSS-IV in its first
two years of operation (July 2014-2016). Like all previous SDSS releases, DR14
is cumulative, including the most recent reductions and calibrations of all
data taken by SDSS since the first phase began operations in 2000. New in DR14
is the first public release of data from the extended Baryon Oscillation
Spectroscopic Survey (eBOSS); the first data from the second phase of the
Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2),
including stellar parameter estimates from an innovative data driven machine
learning algorithm known as "The Cannon"; and almost twice as many data cubes
from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous
release (N = 2812 in total). This paper describes the location and format of
the publicly available data from SDSS-IV surveys. We provide references to the
important technical papers describing how these data have been taken (both
targeting and observation details) and processed for scientific use. The SDSS
website (www.sdss.org) has been updated for this release, and provides links to
data downloads, as well as tutorials and examples of data use. SDSS-IV is
planning to continue to collect astronomical data until 2020, and will be
followed by SDSS-V.Comment: SDSS-IV collaboration alphabetical author data release paper. DR14
happened on 31st July 2017. 19 pages, 5 figures. Accepted by ApJS on 28th Nov
2017 (this is the "post-print" and "post-proofs" version; minor corrections
only from v1, and most of errors found in proofs corrected
Incidence of AIDS-Defining Opportunistic Infections in a Multicohort Analysis of HIV-infected Persons in the United States and Canada, 2000–2010
Background. There are few recent data on the rates of AIDS-defining opportunistic infections (OIs) among human immunodeficiency virus (HIV)–infected patients in care in the United States and Canada
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