2,069 research outputs found
Bohr's 1913 molecular model revisited
It is generally believed that the old quantum theory, as presented by Niels
Bohr in 1913, fails when applied to few electron systems, such as the H2
molecule. Here we find new solutions within the Bohr theory that describe the
potential energy curve for the lowest singlet and triplet states of H2 about as
well as the early wave mechanical treatment of Heitler and London. We also
develop a new interpolation scheme which substantially improves the agreement
with the exact ground state potential curve of H2 and provides a good
description of more complicated molecules such as LiH, Li2, BeH and He2.Comment: 6 pages, 9 figure
Phase-coherent repetition rate multiplication of a mode-locked laser from 40 MHz to 1 GHz by injection locking
We have used injection locking to multiply the repetition rate of a passively
mode-locked femtosecond fiber laser from 40 MHz to 1 GHz while preserving
optical phase coherence between the master laser and the slave output. The
system is implemented almost completely in fiber and incorporates gain and
passive saturable absorption. The slave repetition rate is set to a rational
harmonic of the master repetition rate, inducing pulse formation at the least
common multiple of the master and slave repetition rates
O. D. Edwards, Arnold O. Morgan, Decker S. Womack and Dean Gano to Gov. Ross Barnett, 28 September 1962
Senders state that for every border patrolman sent to carry out Bobby\u27s order they will send another Texan to face him. Message was forwarded to Jackson, MS.https://egrove.olemiss.edu/west_union_gov/1065/thumbnail.jp
Chalcogenide-glass polarization-maintaining photonic crystal fiber for mid-infrared supercontinuum generation
In this paper, we report the design and fabrication of a highly birefringent
polarization-maintaining photonic crystal fiber (PM-PCF) made from chalcogenide
glass, and its application to linearly-polarized supercontinuum (SC) generation
in the mid-infrared region. The PM fiber was drawn using the casting method
from As38Se62 glass which features a transmission window from 2 to 10
and a high nonlinear index of 1.13.10mW. It has a
zero-dispersion wavelength around 4.5 and, at this wavelength, a large
birefringence of 6.10 and consequently strong polarization maintaining
properties are expected. Using this fiber, we experimentally demonstrate
supercontinuum generation spanning from 3.1-6.02 and 3.33-5.78
using femtosecond pumping at 4 and 4.53 , respectively. We
further investigate the supercontinuum bandwidth versus the input pump
polarization angle and we show very good agreement with numerical simulations
of the two-polarization model based on two coupled generalized nonlinear
Schr\"odinger equations.Comment: 13 pages, 8 figure
Off-Critical SLE(2) and SLE(4): a Field Theory Approach
Using their relationship with the free boson and the free symplectic fermion,
we study the off-critical perturbation of SLE(4) and SLE(2) obtained by adding
a mass term to the action. We compute the off-critical statistics of the source
in the Loewner equation describing the two dimensional interfaces. In these two
cases we show that ratios of massive by massless partition functions,
expressible as ratios of regularised determinants of massive and massless
Laplacians, are (local) martingales for the massless interfaces. The
off-critical drifts in the stochastic source of the Loewner equation are
proportional to the logarithmic derivative of these ratios. We also show that
massive correlation functions are (local) martingales for the massive
interfaces. In the case of massive SLE(4), we use this property to prove a
factorisation of the free boson measure.Comment: 30 pages, 1 figures, Published versio
Hypertension in autosomal dominant polycystic kidney disease: a meta-analysis
CONTEXT: Autosomal dominant polycystic kidney disease (ADPKD) is a common disorder that can cause hypertension during childhood, but the true prevalence of hypertension during childhood is not known. OBJECTIVE: We undertook a systematic review and meta-analysis to determine the prevalence of hypertension in children with ADPKD. DATA SOURCES: Systematic review of articles published between 1980 and 2015 in MEDLINE and EMBASE. STUDY SELECTION: Studies selected by two authors independently if reporting data on prevalence of hypertension in children and young persons aged 15 children. Articles were excluded if inadequate diagnostic criteria for hypertension were used. Studies with selection bias were included but analysed separately. DATA EXTRACTION: Data extracted on prevalence of hypertension, proteinuria and reduced renal function using standardised form. Meta-analysis was performed to calculate weighted mean prevalence. RESULTS: 903 articles were retrieved from our search; 14 studies met the inclusion criteria: 1 prospective randomised controlled trial; 8 prospective observational studies; and 5 retrospective cross-sectional studies. From 928 children with clinically confirmed ADPKD, 20% (95% CI 15% to 27%) were hypertensive. The estimated prevalence of proteinuria in children with ADPKD is 20% (8 studies; 95% CI 9% to 40%) while reduced renal function occurred in 8% (5 studies; 95% CI 2% to 26%). LIMITATIONS: Studies showed a high degree of methodological heterogeneity (I(2)=73.4%, τ(2)=0.3408, p<0.0001). Most studies did not use ambulatory blood pressure (BP) monitoring to diagnose hypertension. CONCLUSIONS: In this meta-analysis we estimate 20% of children with ADPKD have hypertension. In the population, many children with ADPKD are not under regular follow-up and remain undiagnosed. We recommend that all children at risk of ADPKD have regular BP measurement
Dust enshrouded star-forming activity in Arp 299
We present mid-infrared spectro-imaging (5 - 16 microns) observations of the
infrared luminous interacting system Arp 299 (=Mrk171 =IC694+NGC3690) obtained
with the ISOCAM instrument aboard ISO. Our observations show that nearly 40% of
the total emission at 7 and 15 microns is diffuse, originating from the
interacting disks of the galaxies. Moreover, they indicate the presence of
large amounts of hot dust in the main infrared sources of the system and large
extinctions toward the nuclei. While the observed spectra have an overall
similar shape, mainly composed of Unidentified Infrared Bands (UIB) in the
short wavelength domain, a strong continuum at ~ 13 microns and a deep silicate
absorption band at 10 microns, their differences reveal the varying physical
conditions of each component. For each source, the spectral energy distribution
(SED) can be reproduced by a linear combination of a UIB "canonical" spectral
template and a hot dust continuum due to a 230-300 K black body, after
independently applying an extinction correction to both of them. We find that
the UIB extinction does not vary much throughout the system (A_V ~ 5 mag)
suggesting that most UIBs originate from less enshrouded regions. IC694 appears
to dominate the infrared emission of the system and our observations support
the interpretation of a deeply embedded nuclear starburst located behind an
absorption of about 40 mag. The central region of NGC3690 displays a hard
radiation field characterized by a [NeIII]/[NeII] ratio > 1.8. It also hosts a
strong continuum from 5 to 16 microns which can be explained as thermal
emission from a deeply embedded (A_V ~ 60 mag) compact source, consistent with
the mid-infrared signature of an active galactic nucleus (AGN), and in
agreement with recent X-ray findings.Comment: to be published in Astronomy and Astrophysics - 12 page
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