1,459 research outputs found
Testing the presence of multiple photometric components in nearby early-type galaxies using SDSS
We investigate two-dimensional image decomposition of nearby, morphologically
selected early-type galaxies (ETGs). We are motivated by recent observational
evidence of significant size growth of quiescent galaxies and theoretical
development advocating a two-phase formation scenario for ETGs. We find that a
significant fraction of nearby ETGs show changes in isophotal shape that
require multi-component models. The characteristic sizes of the inner and outer
component are and kpc. The inner component lies on the
mass-size relation of ETGs at , while the outer component
tends to be more elliptical and hints at a stochastic buildup process. We find
real physical differences between the single- and double-component ETGs, with
the double-component galaxies being younger and more metal-rich. The fraction
of double component ETGs increases with increasing and decreases in
denser environments. We hypothesize that double-component systems were able to
accrete gas and small galaxies until later times, boosting their central
densities, building up their outer parts, and lowering their typical central
ages. In contrast, the oldest galaxies, perhaps due to residing in richer
environments, have no remaining hints of their last accretion episode.Comment: resubmitted to ApJ after referee's repor
Magnetic flux pumping in 3D nonlinear magnetohydrodynamic simulations
A self-regulating magnetic flux pumping mechanism in tokamaks that maintains
the core safety factor at , thus preventing sawteeth, is analyzed
in nonlinear 3D magnetohydrodynamic simulations using the M3D-C code. In
these simulations, the most important mechanism responsible for the flux
pumping is that a saturated quasi-interchange instability generates
an effective negative loop voltage in the plasma center via a dynamo effect. It
is shown that sawtoothing is prevented in the simulations if is
sufficiently high to provide the necessary drive for the
instability that generates the dynamo loop voltage. The necessary amount of
dynamo loop voltage is determined by the tendency of the current density
profile to centrally peak which, in our simulations, is controlled by the
peakedness of the applied heat source profile.Comment: submitted to Physics of Plasmas (23 pages, 15 Figures
The Search for Stable, Massive, Elementary Particles
In this paper we review the experimental and observational searches for
stable, massive, elementary particles other than the electron and proton. The
particles may be neutral, may have unit charge or may have fractional charge.
They may interact through the strong, electromagnetic, weak or gravitational
forces or through some unknown force. The purpose of this review is to provide
a guide for future searches - what is known, what is not known, and what appear
to be the most fruitful areas for new searches. A variety of experimental and
observational methods such as accelerator experiments, cosmic ray studies,
searches for exotic particles in bulk matter and searches using astrophysical
observations is included in this review.Comment: 34 pages, 8 eps figure
The association between leukocytes and sperm quality is concentration dependent
<p>Abstract</p> <p>Background</p> <p>To evaluate the association between leukocytes (polymorphonuclear granulocytes -PMNL) and semen parameters at different leukocyte concentrations.</p> <p>Methods</p> <p>This was a retrospective clinical study at a university hospital andrology clinic. Semen samples from infertile men were analyzed for sperm morphology and motility according to seminal leukocytes (PMNL) concentration (category A: >0 to <0.25 × 10(6)/mL; category B: >0.25 to <0.5 × 10(6)/mL; category C: >0.5 to <0.75 × 10(6)/mL; category D: >0.75 to <1.0 × 10(6)/mL, category E: >1 × 10(6)/mL).</p> <p>Results</p> <p>The percentage of sperm with normal morphology increased significantly from category A (14%) to category D (19%) but decreased in category E to levels (14%) similar to those in category A. Motility grades a and a+b (combined) also increased from category A (12%, 20%) to category D (18.0%, 28.5%) and decreased in category E (11%, 20.5%) to levels similar to those in category A. Sperm deformities and motility grades c and d increased progressively in all categories.</p> <p>Summary</p> <p>Leukocytes had a positive association with normal morphology and progressive motility in semen samples at a concentration of 0-1 × 10(6)/mL. The findings suggest that the association between leukocytes (PMNL) and semen quality might be concentration dependent.</p
Endothelial Function Assessed by Digital Volume Plethysmography Predicts the Development and Progression of Type 2 Diabetes Mellitus
Background
Endothelial dysfunction is a consequence of type 2 diabetes mellitus, but it is unclear whether endothelial dysfunction of conductance versus resistance vessels may also precede type 2 diabetes mellitus development.
Methods and Results
In a population‐based cohort of 15 010 individuals from the GHS (Gutenberg Health Study) (aged 35–74 years at enrollment in 2007–2012), we identified 1610 cases of incident pre–diabetes mellitus and 386 cases of incident type 2 diabetes mellitus by hemoglobin A1c (HbA1c) and/or medical history between 2012 and 2017. Endothelial function of conductance and resistance vessels was measured by flow‐mediated dilation and digital volume plethysmography–derived reactive hyperemia index, respectively. Multivariable regression modeling was used to estimate β coefficients of HbA1c levels at follow‐up and relative risks of incident (pre–)diabetes mellitus. Reactive hyperemia index was independently associated with HbA1c after multivariable adjustment for baseline HbA1c, sex, age, socioeconomic status, arterial hypertension, waist/height ratio, pack‐years of smoking, non–high‐density lipoprotein/high‐density lipoprotein ratio, physical activity, family history of myocardial infarction/stroke, prevalent cardiovascular disease, medication use, and C‐reactive protein (β=−0.020; P=0.0029). The adjusted relative risk per SD decline in reactive hyperemia index was 1.08 (95% CI, 1.02–1.15; P=0.012) for incident pre–diabetes mellitus and 1.16 (95% CI, 1.01–1.34; P=0.041) for incident type 2 diabetes mellitus. Flow‐mediated dilation independently increased the relative risk for developing pre–diabetes mellitus by 8% (95% CI, 1.02–1.14; P=0.012), but it was not independently associated with incident type 2 diabetes mellitus (relative risk, 1.01; 95% CI, 0.86–1.19; P=0.92) and with HbA1c (β=−0.003; P=0.59).
Conclusions
Endothelial dysfunction of resistance rather than conductance vessels may precede the development of (pre–)diabetes mellitus. Assessment of endothelial function by digital volume plethysmography may help to identify subjects at risk for development of type 2 diabetes mellitus
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