3,759 research outputs found
Optimal Tradeoff Between Exposed and Hidden Nodes in Large Wireless Networks
Wireless networks equipped with the CSMA protocol are subject to collisions
due to interference. For a given interference range we investigate the tradeoff
between collisions (hidden nodes) and unused capacity (exposed nodes). We show
that the sensing range that maximizes throughput critically depends on the
activation rate of nodes. For infinite line networks, we prove the existence of
a threshold: When the activation rate is below this threshold the optimal
sensing range is small (to maximize spatial reuse). When the activation rate is
above the threshold the optimal sensing range is just large enough to preclude
all collisions. Simulations suggest that this threshold policy extends to more
complex linear and non-linear topologies
Systemic lupus during pregnancy with refractory alveolar haemorrhage: recovery following termination of pregnancy
A case of refractory pulmonary hemorrhage in a pregnant 22-year-old with systemic lupus is presented. The clinical difficulty of management of pulmonary haemorrhage and lupus flare during pregnancy are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68549/2/10.1177_096120339700600909.pd
Formation of central massive objects via tidal compression
For a density that is not too sharply peaked towards the center, the local
tidal field becomes compressive in all three directions. Available gas can then
collapse and form a cluster of stars in the center, including or even being
dominated by a central black hole. We show that for a wide range of
(deprojected) Sersic profiles in a spherical potential, the tidal forces are
compressive within a region which encloses most of the corresponding light of
observed nuclear clusters in both late-type and early-type galaxies. In such
models, tidal forces become disruptive nearly everywhere for relatively large
Sersic indices n >= 3.5. We also show that the mass of a central massive object
(CMO) required to remove all radial compressive tidal forces scales linearly
with the mass of the host galaxy. If CMOs formed in (progenitor) galaxies with
n ~ 1, we predict a mass fraction of ~ 0.1-0.5%, consistent with observations
of nuclear clusters and super-massive black holes. While we find that tidal
compression possibly drives the formation of CMOs in galaxies, beyond the
central regions and on larger scales in clusters disruptive tidal forces might
contribute to prevent gas from cooling.Comment: 19 pages, 4 figures. Accepted for publication in ApJ. High resolution
version available at
http://www-obs.univ-lyon1.fr/labo/perso/eric.emsellem/preprint
Case finding of mild cognitive impairment and dementia and subsequent care; results of a cluster RCT in primary care
Purpose Despite a call for earlier diagnosis of dementia, the diagnostic yield of case finding and its impact on the mental health of patients and relatives are unclear. This study assessed the effect of a two-component intervention of case finding and subsequent care on these outcomes. Methods In a cluster RCT we assessed whether education of family physicians (FPs; trial stage 1) resulted in more mild cognitive impairment (MCI) and dementia diagnoses among older persons in whom FPs suspected cognitive decline and whether case finding by a practice nurse and the FP (trial stage 2) added to this number of diagnoses. In addition, we assessed mental health effects of case finding and subsequent care (trial stage 2). FPs of 15 primary care practices (PCPs = clusters) judged the cognitive status of all persons ≤ 65 years. The primary outcome, new MCI and dementia diagnoses by FPs after 12 months as indicated on a list, was assessed among all persons in whom FPs suspected cognitive impairment but without a formal diagnosis of dementia. The secondary outcome, mental health of patients and their relatives, was assessed among persons consenting to participate in trial stage 2. Trial stage 1 consisted of either intervention component 1: training FPs to diagnose MCI and dementia, or control: no training. Trial stage 2 consisted of either intervention component 2: case finding of MCI and dementia and care by a trained nurse and the FP, or control: care as usual. Results Seven PCPs were randomized to the intervention; eight to the control condition. MCI or dementia was diagnosed in 42.3 (138/326) of persons in the intervention, and in 30.5 (98/321) in the control group (estimated difference GEE: 10.8, OR: 1.51, 95-CI 0.60-3.76). Among patients and relatives who consented to stage 2 of the trial (n = 145; 25), there were no differences in mental health between the intervention and control group. Conclusions We found a non-significant increase in the number of new MCI diagnoses. As we cannot exclude a clinically relevant effect, a larger study is warranted to replicate ours. Trial Registration Nederlands Trial Register NTR3389 © 2016 van den Dungen et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
22: Ex-vivo expansion (EvE) of previously cryopreserved cord blood (CB) into natural killer (NK) cells with enhanced AML and neuroblastoma cytotoxicity Potential role of CB NK cells in adoptive cellular immunotherapy (ACI)
Newsletter providing "a lighter, human interest side of the news" from the Boston University Medical Campus
Black-hole-regulated star formation in massive galaxies
Super-massive black holes, with masses larger than a million times that of
the Sun, appear to inhabit the centers of all massive galaxies.
Cosmologically-motivated theories of galaxy formation need feedback from these
super-massive black holes to regulate star formation. In the absence of such
feedback, state-of-the-art numerical simulations dramatically fail to reproduce
the number density and properties of massive galaxies in the local Universe.
However, there is no observational evidence of this strongly coupled
co-evolution between super-massive black holes and star formation, impeding our
understanding of baryonic processes within galaxies. Here we show that the star
formation histories (SFHs) of nearby massive galaxies, as measured from their
integrated optical spectra, depend on the mass of the central super-massive
black hole. Our results suggest that black hole mass growth scales with gas
cooling rate in the early Universe. The subsequent quenching of star formation
takes place earlier and more efficiently in galaxies hosting more massive
central black holes. The observed relation between black hole mass and star
formation efficiency applies to all generations of stars formed throughout a
galaxy's life, revealing a continuous interplay between black hole activity and
baryon cooling.Comment: Published in Nature, 1 January 201
A study of rotating globular clusters - the case of the old, metal-poor globular cluster NGC 4372
Aims: We present the first in-depth study of the kinematic properties and
derive the structural parameters of NGC 4372 based on the fit of a Plummer
profile and a rotating, physical model. We explore the link between internal
rotation to different cluster properties and together with similar studies of
more GCs, we put these in the context of globular cluster formation and
evolution. Methods: We present radial velocities for 131 cluster member stars
measured from high-resolution FLAMES/GIRAFFE observations. Their membership to
the GC is additionally confirmed from precise metallicity estimates. Using this
kinematic data set we build a velocity dispersion profile and a systemic
rotation curve. Additionally, we obtain an elliptical number density profile of
NGC 4372 based on optical images using a MCMC fitting algorithm. From this we
derive the cluster's half-light radius and ellipticity as r_h=3.4'+/-0.04' and
e=0.08+/-0.01. Finally, we give a physical interpretation of the observed
morphological and kinematic properties of this GC by fitting an axisymmetric,
differentially rotating, dynamical model. Results: Our results show that NGC
4372 has an unusually high ratio of rotation amplitude to velocity dispersion
(1.2 vs. 4.5 km/s) for its metallicity. This, however, puts it in line with two
other exceptional, very metal-poor GCs - M 15 and NGC 4590. We also find a mild
flattening of NGC 4372 in the direction of its rotation. Given its old age,
this suggests that the flattening is indeed caused by the systemic rotation
rather than tidal interactions with the Galaxy. Additionally, we estimate the
dynamical mass of the GC M_dyn=2.0+/-0.5 x 10^5 M_Sun based on the dynamical
model, which constrains the mass-to-light ratio of NGC 4372 between 1.4 and 2.3
M_Sun/L_Sun, representative of an old, purely stellar population.Comment: Accepted for publication in A&A, 12 pages, 14 figures, 2 table
The wall shear rate distribution for flow in random sphere packings
The wall shear rate distribution P(gamma) is investigated for pressure-driven
Stokes flow through random arrangements of spheres at packing fractions 0.1 <=
phi <= 0.64. For dense packings, P(gamma) is monotonic and approximately
exponential. As phi --> 0.1, P(gamma) picks up additional structure which
corresponds to the flow around isolated spheres, for which an exact result can
be obtained. A simple expression for the mean wall shear rate is presented,
based on a force-balance argument.Comment: 4 pages, 3 figures, 1 table, RevTeX 4; significantly revised with
significantly extended scop
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