11,974 research outputs found
Early life growth patterns persist for 12 years and impact pulmonary outcomes in cystic fibrosis
BACKGROUND:
In children with cystic fibrosis (CF), recovery from growth faltering within 2 years of diagnosis (Responders) is associated with better growth and less lung disease at age 6 years. This study examined whether these benefits are sustained through 12 years of age.
METHODS:
Longitudinal growth from 76 children with CF enrolled in the Wisconsin CF Neonatal Screening Project was examined and categorized into 5 groups: R12, R6, and R2, representing Responders who maintained growth improvement to age 12, 6, and 2 years, respectively, and I6 and N6, representing Non-responders whose growth did and did not improve during ages 2-6 years, respectively. Lung disease was evaluated by % predicted forced expiratory volume in one second (FEV1) and chest radiograph (CXR) scores.
RESULTS:
Sixty-two percent were Responders. Within this group, 47% were R12, 28% were R6, and 25% were R2. Among Non-responders, 76% were N6. CF children with meconium ileus (MI) had worse lung function and CXR scores compared to other CF children. Among 53 children with pancreatic insufficiency without MI, R12 had significantly better FEV1 (97-99% predicted) and CXR scores during ages 6-12 years than N6 (89-93% predicted). Both R6 and R2 experienced a decline in FEV1 by ages 10-12 years.
CONCLUSIONS:
Early growth recovery in CF is critical, as malnutrition during infancy tends to persist and catch-up growth after age 2 years is difficult. The longer adequate growth was maintained after early growth recovery, the better the pulmonary outcomes at age 12 years
Attempted DNA extraction from a Rancho La Brea Columbian mammoth (Mammuthus columbi): prospects for ancient DNA from asphalt deposits.
Fossil-bearing asphalt deposits are an understudied and potentially significant source of ancient DNA. Previous attempts to extract DNA from skeletons preserved at the Rancho La Brea tar pits in Los Angeles, California, have proven unsuccessful, but it is unclear whether this is due to a lack of endogenous DNA, or if the problem is caused by asphalt-mediated inhibition. In an attempt to test these hypotheses, a recently recovered Columbian mammoth (Mammuthus columbi) skeleton with an unusual pattern of asphalt impregnation was studied. Ultimately, none of the bone samples tested successfully amplified M. columbi DNA. Our work suggests that reagents typically used to remove asphalt from ancient samples also inhibit DNA extraction. Ultimately, we conclude that the probability of recovering ancient DNA from fossils in asphalt deposits is strongly (perhaps fatally) hindered by the organic compounds that permeate the bones and that at the Rancho La Brea tar pits, environmental conditions might not have been ideal for the general preservation of genetic material
The K-theoretic Farrell-Jones Conjecture for hyperbolic groups
We prove the K-theoretic Farrell-Jones Conjecture for hyperbolic groups with
(twisted) coefficients in any associative ring with unit.Comment: 33 pages; final version; to appear in Invent. Mat
Influence of Phase Matching on the Cooper Minimum in Ar High Harmonic Spectra
We study the influence of phase matching on interference minima in high
harmonic spectra. We concentrate on structures in atoms due to interference of
different angular momentum channels during recombination. We use the Cooper
minimum (CM) in argon at 47 eV as a marker in the harmonic spectrum. We measure
2d harmonic spectra in argon as a function of wavelength and angular
divergence. While we identify a clear CM in the spectrum when the target gas
jet is placed after the laser focus, we find that the appearance of the CM
varies with angular divergence and can even be completely washed out when the
gas jet is placed closer to the focus. We also show that the argon CM appears
at different wavelengths in harmonic and photo-absorption spectra measured
under conditions independent of any wavelength calibration. We model the
experiment with a simulation based on coupled solutions of the time-dependent
Schr\"odinger equation and the Maxwell wave equation, including both the single
atom response and macroscopic effects of propagation. The single atom
calculations confirm that the ground state of argon can be represented by its
field free symmetry, despite the strong laser field used in high harmonic
generation. Because of this, the CM structure in the harmonic spectrum can be
described as the interference of continuum and channels, whose relative
phase jumps by at the CM energy, resulting in a minimum shifted from the
photoionization result. We also show that the full calculations reproduce the
dependence of the CM on the macroscopic conditions. We calculate simple phase
matching factors as a function of harmonic order and explain our experimental
and theoretical observation in terms of the effect of phase matching on the
shape of the harmonic spectrum. Phase matching must be taken into account to
fully understand spectral features related to HHG spectroscopy
Expected Supremum of a Random Linear Combination of Shifted Kernels
We address the expected supremum of a linear combination of shifts of the
sinc kernel with random coefficients. When the coefficients are Gaussian, the
expected supremum is of order \sqrt{\log n}, where n is the number of shifts.
When the coefficients are uniformly bounded, the expected supremum is of order
\log\log n. This is a noteworthy difference to orthonormal functions on the
unit interval, where the expected supremum is of order \sqrt{n\log n} for all
reasonable coefficient statistics.Comment: To appear in the Journal of Fourier Analysis and Application
Supercooling across first-order phase transitions in vortex matter
Hysteresis in cycling through first-order phase transitions in vortex matter,
akin to the well-studied phenomenon of supercooling of water, has been
discussed in literature. Hysteresis can be seen while varying either
temperature T or magnetic field H (and thus the density of vortices). Our
recent work on phase transitions with two control variables shows that the
observable region of metastability of the supercooled phase would depend on the
path followed in H-T space, and will be larger when T is lowered at constant H
compared to the case when H is lowered at constant T. We discuss the effect of
isothermal field variations on metastable supercooled states produced by
field-cooling. This path dependence is not a priori applicable to metastability
caused by reduced diffusivity or hindered kinetics.Comment: Tex, 8 pages, 3 Postscripts figures. Submitted to Pramana - J.
Physic
Poor recovery from cystic fibrosis pulmonary exacerbations is associated with poor long-term outcomes
RATIONALE:
People with CF treated with IV antibiotics for a pulmonary exacerbation (PEx) frequently fail to recover to baseline FEV1 . The long-term impact of these events has not been studied.
OBJECTIVES:
To determine if a patient's spirometric recovery after a PEx is associated with time to next PEx within 1 year, the spirometric recovery after the next PEx, and/or the number of PEx episodes in the next 3 years.
METHODS:
We used data from the CF Foundation Patient Registry from 2004 to 2011. We randomly selected one PEx per patient that met inclusion/exclusion criteria. Patients were defined as Non-Responders if their best FEV1 (in liters) recorded in the 3 months after the PEx was <90% of the best FEV1 (in liters) in the 6 months before the PEx. We compared Responders and Non-Responders using multivariable regression models.
RESULTS:
We randomly chose 13 954 PEx episodes that met inclusion/exclusion criteria. A total of 2 762 (19.8%) patients were classified as Non-Responders. Non-Responders had a shorter median time to the next PEx, 235 (95%CI 218, 252) days, versus >365 days for Responders. Thirty-four percent of Non-Responders at the initial PEx were also Non-Reponders at the next PEx, versus 20% of Responders at the initial PEx. Non-Responders had more PEx episodes over the next 3 years, 4.99 (95%CI 4.84, 5.13), than Responders, 3.46 (95%CI 3.41, 3.51).
CONCLUSIONS:
Poor recovery after a PEx is associated with a shorter time to the next PEx, increased risk of poor recovery at a second PEx, and more frequent subsequent PEx treatments
Employer perceptions of skills gaps in retail:issues and implications for UK retailers
Purpose – This paper seeks to identify the skills gaps associated with retail employees in SME and multiple retail companies, and to investigate the potential training and business implications that arise from these skills gaps, from the point of view of retail employers. Design/methodology/approach – Research was conducted within one geographical region and across five counties within the UK. Telephone and face-to-face interviews and focus group workshops were conducted, resulting in responses from 52 retailers. Findings – The key issues and areas of concern to emerge were: the industry image and impact on recruitment and retention; employee and management skills gaps; and barriers to training. Research limitations/implications – The findings highlight the need for UK retail industry to raise the image of the sector, to identify the skills sets for specific roles, and to clarify the retail qualifications and training required delivering these. Originality/value – Succeeds in identifying the skills gaps associated with retail employees in SME and multiple retail companies and in investigating the potential training and business implications arising from these skills gaps
Investigating slim disk solutions for HLX-1 in ESO 243-49
The hyper luminous X-ray source HLX-1 in the galaxy ESO 243-49, currently the
best intermediate mass black hole candidate, displays spectral transitions
similar to those observed in Galactic black hole binaries, but with a
luminosity 100-1000 times higher. We investigated the X-ray properties of this
unique source fitting multi-epoch data collected by Swift, XMM-Newton & Chandra
with a disk model computing spectra for a wide range of sub- and
super-Eddington accretion rates assuming a non-spinning black hole and a
face-on disk (i = 0 deg). Under these assumptions we find that the black hole
in HLX-1 is in the intermediate mass range (~2 x 10^4 M_odot) and the accretion
flow is in the sub-Eddington regime. The disk radiation efficiency is eta =
0.11 +/-0.03. We also show that the source does follow the L_X ~ T^4 relation
for our mass estimate. At the outburst peaks, the source radiates near the
Eddington limit. The accretion rate then stays constant around 4 x 10^(-4)
M_odot yr^(-1) for several days and then decreases exponentially. Such
"plateaus" in the accretion rate could be evidence that enhanced mass transfer
rate is the driving outburst mechanism in HLX-1. We also report on the new
outburst observed in August 2011 by the Swift-X-ray Telescope. The time of this
new outburst further strengthens the ~1 year recurrence timescale.Comment: 24 pages, 10 figures, accepted for publication in Ap
Lattice thermal conductivity of disordered NiPd and NiPt alloys
Numerical calculations of lattice thermal conductivity are reported for the
binary alloys NiPd and NiPt. The present work is a continuation of an earlier
paper by us [PRB, 72, 214207 (2005)]which had developed a theoretical framework
for the calculation of configuration-averaged lattice thermal conductivity and
thermal diffusivity in disordered alloys. The formulation was based on the
augmented space theorem combined with a scattering diagram technique. In this
paper we shall show dependence of the lattice thermal conductivity on a series
of variables like phonon frequency, temperature and alloy composition. The
temperature dependence of and its realtion to the measured thermal
conductivity is discussed. The concentration dependence of appears to
justify the notion of a minimum thermal conductivity as discussed by Kittel,
Slack and others. We also study the frequency and composition dependence of the
thermal diffusivity averaged over modes. A numerical estimate of this quantity
gives an idea about the location of mobility edge and the fraction of states in
the frequency spectrum which is delocalized.Comment: 23 pages, 18 figure
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