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Glucocorticoid-regulated localization of cell surface glycoproteins in rat hepatoma cells is mediated within the Golgi complex.
Glucocorticoid hormones regulate the post-translational maturation and sorting of cell surface and extracellular mouse mammary tumor virus (MMTV) glycoproteins in M1.54 cells, a stably infected rat hepatoma cell line. Exposure to monensin significantly reduced the proteolytic maturation and externalization of viral glycoproteins resulting in a stable cellular accumulation of a single 70,000-Mr glycosylated polyprotein (designated gp70). Cell surface- and intracellular-specific immunoprecipitations of monensin-treated cells revealed that gp70 can be localized to the cell surface only in the presence of 1 microM dexamethasone, while in uninduced cells gp70 is irreversibly sequestered in an intracellular compartment. Analysis of oligosaccharide processing kinetics demonstrated that gp70 acquired resistance to endoglycosidase H with a half-time of 65 min in the presence or absence of hormone. In contrast, gp70 was inefficiently galactosylated after a 60-min lag in uninduced cells while rapidly acquiring this carbohydrate modification in the presence of dexamethasone. Furthermore, in the absence or presence of monensin, MMTV glycoproteins failed to be galactosylated in hormone-induced CR4 cells, a complement-selected sorting variant defective in the glucocorticoid-regulated compartmentalization of viral glycoproteins to the cell surface. Since dexamethasone had no apparent global effects on organelle morphology or production of total cell surface-galactosylated species, we conclude that glucocorticoids induce the localization of cell surface MMTV glycoproteins by regulating a highly selective step within the Golgi apparatus after the acquisition of endoglycosidase H-resistant oligosaccharide side chains but before or at the site of galactose attachment
Gravitational Settling of ^{22}Ne in Liquid White Dwarf Interiors--Cooling and Seismological Effects
We assess the impact of the trace element ^{22}Ne on the cooling and
seismology of a liquid C/O white dwarf (WD). Due to this elements' neutron
excess, it sinks towards the interior as the liquid WD cools. The subsequent
gravitational energy released slows the cooling of the WD by 0.25--1.6 Gyrs by
the time it has completely crystallized, depending on the WD mass and the
adopted sedimentation rate. The effects will make massive WDs or those in metal
rich clusters (such as NGC 6791) appear younger than their true age. Our
diffusion calculations show that the ^{22}Ne mass fraction in the crystallized
core actually increases outwards. The stability of this configuration has not
yet been determined. In the liquid state, the settled ^{22}Ne enhances the
internal buoyancy of the interior and changes the periods of the high radial
order g-modes by approximately 1%. Though a small adjustment, this level of
change far exceeds the accuracy of the period measurements. A full assessment
and comparison of mode frequencies for specific WDs should help constrain the
still uncertain ^{22}Ne diffusion coefficient for the liquid interior.Comment: 26 pages (11 text pages with 15 figures); to appear in The
Astrophysical Journa
Gravitational settling of 22Ne and white dwarf evolution
We study the effects of the sedimentation of the trace element 22Ne in the
cooling of white dwarfs. In contrast with previous studies, which adopted a
simplified treatment of the effects of 22Ne sedimentation, this is done
self-consistently for the first time, using an up-to-date stellar evolutionary
code in which the diffusion equation is coupled with the full set of equations
of stellar evolution. Due the large neutron excess of 22Ne, this isotope
rapidly sediments in the interior of the white dwarf. Although we explore a
wide range of parameters, we find that using the most reasonable assumptions
concerning the diffusion coefficient and the physical state of the white dwarf
interior the delay introduced by the ensuing chemical differentation is minor
for a typical 0.6 Msun white dwarf. For more massive white dwarfs, say M_Wd
about 1.0 Msun, the delay turns out to be considerably larger. These results
are in qualitatively good accord with those obtained in previous studies, but
we find that the magnitude of the delay introduced by 22Ne sedimentation was
underestimated by a factor of about 2. We also perform a preliminary study of
the impact of 22Ne sedimentation on the white dwarf luminosity function.
Finally, we hypothesize as well on the possibility of detecting the
sedimentation of 22Ne using pulsating white dwarfs in the appropriate effective
temperature range with accurately determined rates of change of the observed
periods.Comment: To apper in The Astrophysical Journa
Abdominal obesity in adolescents: Development of age-specific waist circumference cut-offs linked to adult IDF criteria
Objectives: The purpose of this study was to develop age- and sex-specific waist cir-cumference (WC) cut-off points, linked to older adolescent and adult criteria forabdominal obesity, to be applied to children in the clinical setting.Methods: A total of 16,788 adolescents aged 10 to 16 years were assessed for WC.Smoothed age and sex-specific WC curves were obtained using Coleâs LMS method.Results: Percentiles that corresponded to the International Diabetes Federation (IDF)recommendations used for older adolescents and adults (161 years old) were the97thpercentile for boys and the 87thpercentile for girls. Using these cutoffs, a total of368 boys and 1138 girls were categorized as abdominally obese, in contrast to 1654boys and 987 girls that were identified using the current IDF pediatric criteria (90thpercentile).Conclusions: We provide age- and sex-specific cut-off points that can be used toidentify abdominal obesity in adolescents. The present findings provide a tool thatcan be used in the clinical setting for the early detection and prevention of adult obe-sity. Population-specific cutoffs may be required for pediatric ages to diagnosechildren at risk
Axisymmetric smoothed particle hydrodynamics with self-gravity
The axisymmetric form of the hydrodynamic equations within the smoothed
particle hydrodynamics (SPH) formalism is presented and checked using idealized
scenarios taken from astrophysics (free fall collapse, implosion and further
pulsation of a sun-like star), gas dynamics (wall heating problem, collision of
two streams of gas) and inertial confinement fusion (ICF, -ablative implosion
of a small capsule-). New material concerning the standard SPH formalism is
given. That includes the numerical handling of those mass points which move
close to the singularity axis, more accurate expressions for the artificial
viscosity and the heat conduction term and an easy way to incorporate
self-gravity in the simulations. The algorithm developed to compute gravity
does not rely in any sort of grid, leading to a numerical scheme totally
compatible with the lagrangian nature of the SPH equations.Comment: 17 pages, 10 figures, 1 Table. Accepted for publication in MNRA
Swope Supernova Survey 2017a (SSS17a), the Optical Counterpart to a Gravitational Wave Source
On 2017 August 17, the Laser Interferometer Gravitational-wave Observatory
(LIGO) and the Virgo interferometer detected gravitational waves emanating from
a binary neutron star merger, GW170817. Nearly simultaneously, the Fermi and
INTEGRAL telescopes detected a gamma-ray transient, GRB 170817A. 10.9 hours
after the gravitational wave trigger, we discovered a transient and fading
optical source, Swope Supernova Survey 2017a (SSS17a), coincident with
GW170817. SSS17a is located in NGC 4993, an S0 galaxy at a distance of 40
megaparsecs. The precise location of GW170817 provides an opportunity to probe
the nature of these cataclysmic events by combining electromagnetic and
gravitational-wave observations.Comment: 25 pages, 10 figures, 2 tables, published today in Scienc
Constraining deflagration models of Type Ia supernovae through intermediate-mass elements
The physical structure of a nuclear flame is a basic ingredient of the theory
of Type Ia supernovae (SNIa). Assuming an exponential density reduction with
several characteristic times we have followed the evolution of a planar nuclear
flame in an expanding background from an initial density 6.6 10^7 g/cm3 down to
2 10^6 g/cm3. The total amount of synthesized intermediate-mass elements (IME),
from silicon to calcium, was monitored during the calculation. We have made use
of the computed mass fractions, X_IME, of these elements to give an estimation
of the total amount of IME synthesized during the deflagration of a massive
white dwarf. Using X_IME and adopting the usual hypothesis that turbulence
decouples the effective burning velocity from the laminar flame speed, so that
the relevant flame speed is actually the turbulent speed on the integral
length-scale, we have built a simple geometrical approach to model the region
where IME are thought to be produced. It turns out that a healthy production of
IME involves the combination of not too short expansion times, t_c > 0.2 s, and
high turbulent intensities. According to our results it could be difficult to
produce much more than 0.2 solar masses of intermediate-mass elements within
the deflagrative paradigma. The calculations also suggest that the mass of IME
scales with the mass of Fe-peak elements, making it difficult to conciliate
energetic explosions with low ejected nickel masses, as in the well observed
SN1991bg or in SN1998de. Thus a large production of Si-peak elements,
especially in combination with a low or a moderate production of iron, could be
better addressed by either the delayed detonation route in standard
Chandrasekhar-mass models or, perhaps, by the off-center helium detonation in
the sub Chandrasekhar-mass scenario.Comment: 9 pages, 5 figures, 2 table
Photonic crystal optical waveguides for on-chip Bose-Einstein condensates
We propose an on-chip optical waveguide for Bose-Einstein condensates based
on the evanescent light fields created by surface states of a photonic crystal.
It is shown that the modal properties of these surface states can be tailored
to confine the condensate at distances from the chip surface significantly
longer that those that can be reached by using conventional index-contrast
guidance. We numerically demonstrate that by index-guiding the surface states
through two parallel waveguides, the atomic cloud can be confined in a
two-dimensional trap at about 1m above the structure using a power of
0.1mW.Comment: 5 pages, 4 figure
The Old Host-Galaxy Environment of SSS17a, the First Electromagnetic Counterpart to a Gravitational Wave Source
We present an analysis of the host-galaxy environment of Swope Supernova
Survey 2017a (SSS17a), the discovery of an electromagnetic counterpart to a
gravitational wave source, GW170817. SSS17a occurred 1.9 kpc (in projection;
10.2") from the nucleus of NGC 4993, an S0 galaxy at a distance of 40 Mpc. We
present a Hubble Space Telescope (HST) pre-trigger image of NGC 4993, Magellan
optical spectroscopy of the nucleus of NGC 4993 and the location of SSS17a, and
broad-band UV through IR photometry of NGC 4993. The spectrum and broad-band
spectral-energy distribution indicate that NGC 4993 has a stellar mass of log
(M/M_solar) = 10.49^{+0.08}_{-0.20} and star formation rate of 0.003
M_solar/yr, and the progenitor system of SSS17a likely had an age of >2.8 Gyr.
There is no counterpart at the position of SSS17a in the HST pre-trigger image,
indicating that the progenitor system had an absolute magnitude M_V > -5.8 mag.
We detect dust lanes extending out to almost the position of SSS17a and >100
likely globular clusters associated with NGC 4993. The offset of SSS17a is
similar to many short gamma-ray burst offsets, and its progenitor system was
likely bound to NGC 4993. The environment of SSS17a is consistent with an old
progenitor system such as a binary neutron star system.Comment: ApJL in pres
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