599 research outputs found
NGO partnerships and capacity development in the water sanitation and hygiene sector: Abridged version for public dissemination
GLP-1 and glucose tolerance after sleeve gastrectomy in morbidly obese subjects with type 2 diabetes.
Although GLP-1 has been suggested as a major factor for the marked improvement of glucose tolerance commonly seen after sleeve gastrectomy (SG), several observations challenge this hypothesis. To better understand the role of GLP-1 in the remission of type 2 diabetes mellitus (T2DM) long term after SG in humans, we conducted two separate cross-sectional studies: 1) the GLP-1 response to a standardized mixed liquid meal (SMLM) was compared in subjects with T2DM antedating SG but with different long-term (>2 years) T2DM outcomes (remission, relapse, or lack of remission) (study 1) and 2) the effect of GLP-1 receptor blockade with exendin (9-39) on glucose tolerance was examined in subjects with T2DM antedating surgery, who had undergone SG and presented with long-term T2DM remission (study 2). In study 1, we observed a comparable GLP-1 response to the SMLM regardless of the post-SG outcome of T2DM. In study 2, the blockade of GLP-1 action resulted in impaired insulin secretion but limited deterioration of glucose tolerance. Thus, our data suggest the enhanced GLP-1 secretion observed long term after SG is neither sufficient nor critical to maintain normal glucose tolerance in subjects with T2DM antedating the surgery
Accurate masses and radii of normal stars: modern results and applications
This paper presents and discusses a critical compilation of accurate,
fundamental determinations of stellar masses and radii. We have identified 95
detached binary systems containing 190 stars (94 eclipsing systems, and alpha
Centauri) that satisfy our criterion that the mass and radius of both stars be
known to 3% or better. To these we add interstellar reddening, effective
temperature, metal abundance, rotational velocity and apsidal motion
determinations when available, and we compute a number of other physical
parameters, notably luminosity and distance. We discuss the use of this
information for testing models of stellar evolution. The amount and quality of
the data also allow us to analyse the tidal evolution of the systems in
considerable depth, testing prescriptions of rotational synchronisation and
orbital circularisation in greater detail than possible before. The new data
also enable us to derive empirical calibrations of M and R for single (post-)
main-sequence stars above 0.6 M(Sun). Simple, polynomial functions of T(eff),
log g and [Fe/H] yield M and R with errors of 6% and 3%, respectively.
Excellent agreement is found with independent determinations for host stars of
transiting extrasolar planets, and good agreement with determinations of M and
R from stellar models as constrained by trigonometric parallaxes and
spectroscopic values of T(eff) and [Fe/H]. Finally, we list a set of 23
interferometric binaries with masses known to better than 3%, but without
fundamental radius determinations (except alpha Aur). We discuss the prospects
for improving these and other stellar parameters in the near future.Comment: 56 pages including figures and tables. To appear in The Astronomy and
Astrophysics Review. Ascii versions of the tables will appear in the online
version of the articl
Is GNSS real-time positioning a reliable option to validate erosion studies at olive grove environments?
Aim of study: Soil degradation in agricultural areas is a widespread problem. In this framework, a data validation methodology is presented, including a study of the spatial resolution of Global Navigation Satellite System (GNSS) measurements, the calculation of erosion/deposition models, and the contribution of dual frequency and low-cost single frequency GNSS receivers.Area of study: A test olive grove in SE Spain.Material and methods: The study is based on three observation campaigns, between 2016 and 2018, using different GNSS receivers and working modes. The comparison between different surveys provide the volumetric variation over the analyzed period.Main results: Considering the dual-frequency receiver, there was no statistically significant difference between the means and the variances from 1.5 m and from 4.5 m data resolution at the 0.05 significance level. In order to estimate vertical differences from successive GNSS campaigns a differential digital elevation approach was applied. Although the differences depended on the zone of the test area and they changed along the monitoring period, the erosion rate could be catalogued as very low. The dual-frequency receiver satisfied the vertical centimetric precision limits for high accurate Digital Elevation Model (DEM), making it a reliable and accurate option to validate erosion studies in small areas.Research highlights: The results have allowed the characterization of multi-annual spatial redistribution of the topsoil at local scale, being of great help to design future prevention actions for the “tillage erosion” in olive grove environments. However, more tests are needed to guarantee the feasibility of low-cost receivers
RC J0311+0507: A Candidate for Superpowerful Radio Galaxies in the Early Universe at Redshift z=4.514
A strong emission line at 6703A has been detected in the optical spectrum for
the host galaxy (R=23.1) of the radio source RC J0311+0507 (4C+04.11). This
radio galaxy, with a spectral index of 1.31 in the frequency range 365-4850
MHz, is one of the ultrasteep spectrum objects from the deep survey of a sky
strip conducted with RATAN-600 in 1980-1981. We present arguments in favor of
the identification of this line with Ly\alpha at redshift z=4.514. In this
case, the object belongs to the group of extremely distant radio galaxies of
ultrahigh radio luminosity (P_{1400}=1.3 x 10^{29}W Hz^{-1}). Such power can be
provided only by a fairly massive black hole (~10^9M_\sun}) that formed in a
time less than the age of the Universe at the observed z(1.3 Gyr) or had a
primordial origin.Comment: 8 pages, 3 figure
Gene action in short-duration pigeonpeas
F1-F2 hybrids from a half diallel set of crosses involving 7 early Cajanus cajan lines were studied for yield and a number of yield-related traits. Parental performance was a good predictor of breeding value for most traits in the F1, but in the F2 a significant positive association between GCA effects and the parental performance was seen only for number of days to flowering. GCA variance predominated for all traits in the F1 and F2. The results suggested exploitation of the additive genetic variation in breeding for improvement of the cro
Optical and Near-IR Imaging of Ultra Steep Spectrum Radio Sources - The K-z diagram of radio and optically selected galaxies
We present optical and/or near-IR images of 128 ultra steep spectrum (USS)
radio sources. Roughly half of the objects are identified in the optical images
(R 94% are detected at K<~ 22. The mean
K-magnitude is K=19.26 within a 2" diameter aperture. The distribution of R-K
colors indicates that at least 1/3 of the objects observed have very red colors
(R-K>5). The major axes of the identifications in K-band are preferentially
oriented along the radio axes, with half of them having compact morphologies.
The 22 sources with spectroscopic redshifts and K-band magnitudes follow the
K-z relation found from previous radio samples, but with a larger scatter. We
argue that this may be due to a dependence of K-magnitude on the radio power,
with the highest radio power sources inhabiting the most massive host galaxies.
We present a composite K-z diagram of radio-loud and radio-quiet galaxies,
selected from the HDF-North and the Hawaii surveys. Out to z <~ 1, the
radio-loud galaxies trace the bright envelope of the radio quiet galaxies,
while at z >~ 1, the radio-loud galaxies are >~ 2 magnitudes brighter. We argue
that this is not due to a contribution from the AGN or emission lines. This
difference strongly suggests that radio galaxies pinpoint the most massive
systems out to the highest known redshifts, probably due to the mutual
correlation of the mass of the galaxy and the radio power on the mass of the
central black hole.Comment: 39 Pages, including 10 PostScript figures. Accepted for publication
in the January 2002 Astronomical Journal. Figures 2 and 12 are available from
http://www.strw.leidenuniv.nl/~debreuck/paper
The ATESP 5 GHz radio survey. III. 4.8, 8.6 and 19 GHz follow-up observations of radio galaxies
[Abridged] Physical and evolutionary properties of the sub-mJy radio
population are not entirely known. The radio/optical analysis of the ATESP 5
GHz sample has revealed a significant class of compact flat/inverted
radio-spectrum sources associated to early-type galaxies up to redshift 2. Such
sources are most plausibly triggered by an AGN, but their observational
properties are not entirely consistent with those of standard radio galaxy
populations. In the present work we aim at a better understanding of the radio
spectra of such sources and ultimately of the nature of AGNs at sub-mJy flux
levels. We used the ATCA to get multi-frequency (4.8, 8.6 and 19 GHz)
quasi-simultaneous observations for a representative sub-sample of ATESP radio
sources associated with early-type galaxies (26 objects with S>0.6 mJy). This
can give us insight into the accretion/radiative mechanism that is at work,
since different regimes display different spectral signatures in the radio
domain. From the analysis of the radio spectra, we find that our sources are
most probably jet-dominated systems. ADAF models are ruled out by the high
frequency data, while ADAF+jet scenarios are still consistent with
flat/moderately inverted-spectrum sources, but are not required to explain the
data. We compared our sample with high (>20 GHz) frequency selected surveys,
finding spectral properties very similar to the ones of much brighter (S>500
mJy) radio galaxies extracted from the Massardi et al. (2008) sample. Linear
sizes of ATESP 5 GHz sources associated with early type galaxies are also often
consistent with the ones of brighter B2 and 3C radio galaxies, with possibly a
very compact component that could be associated at least in part to (obscured)
radio-quiet quasar-like objects and/or low power BL Lacs.Comment: Accepted for publication in Astronomy & Astrophysic
Computing Naturally in the Billiard Ball Model
Fredkin's Billiard Ball Model (BBM) is considered one of the fundamental
models of collision-based computing, and it is essentially based on elastic
collisions of mobile billiard balls. Moreover, fixed mirrors or reflectors are
brought into the model to deflect balls to complete the computation. However,
the use of fixed mirrors is "physically unrealistic" and makes the BBM not
perfectly momentum conserving from a physical point of view, and it imposes an
external architecture onto the computing substrate which is not consistent with
the concept of "architectureless" in collision-based computing. In our initial
attempt to reduce mirrors in the BBM, we present a class of gates: the
m-counting gate, and show that certain circuits can be realized with few
mirrors using this gate. We envisage that our findings can be useful in future
research of collision-based computing in novel chemical and optical computing
substrates.Comment: 10 pages, 7 figure
X-ray selected Infrared Excess AGN in the Chandra Deep Fields: a moderate fraction of Compton-thick sources
We examine the properties of the X-ray detected, Infrared Excess AGN or Dust
Obscured Galaxies (DOGs) in the Chandra Deep Fields (CDF). We find 26 X-ray
selected sources which obey the 24 micron to R-band flux ratio criterion
f_24/f_R>1000. These are at a median redshift of 2.3 while their IR
luminosities are above 10^12 solar. Their X-ray luminosities are all above a
few times 10^42 erg s-1 in the 2-10 keV band unambiguously arguing that these
host AGN. Nevertheless, their IR Spectral Energy Distributions are split
between AGN (Mrk231) and star-forming templates (Arp220). Our primary goal is
to examine their individual X-ray spectra in order to assess whether this X-ray
detected DOG population contains heavily obscured or even Compton-thick
sources. The X-ray spectroscopy reveals a mixed bag of objects. We find that
four out of the 12 sources with adequate photon statistics and hence reliable
X-ray spectra, show evidence for a hard X-ray spectral index (~1) or
harder,consistent with a Compton-thick spectrum. In total 12 out of the 26 DOGs
show evidence for flat spectral indices. However, owing to the limited photon
statistics we cannot differentiate whether these are flat because they are
reflection-dominated or because they show moderate amounts of absorption. Seven
DOGs show relatively steep spectra (>1.4) indicative of small column densities.
All the above suggest a fraction of Compton-thick sources that does not exceed
5%. The average X-ray spectrum of all 26 DOGs is hard (~1.1) or even harder
(~0.6) when we exclude the brightest sources. These spectral indices are well
in agreement with the stacked spectrum of X-ray undetected sources (~0.8 in the
CDFN). This could suggest (but not necessarily prove) that X-ray undetected
DOGs, in a similar fashion to the X-ray detected ones presented here, are
hosting a moderate fraction of Compton-thick sources.Comment: 16 pages To appear in A&
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