207 research outputs found
Halo concentrations in the standard LCDM cosmology
We study the concentration of dark matter halos and its evolution in N-body
simulations of the standard LCDM cosmology. The results presented in this paper
are based on 4 large N-body simulations with about 10 billion particles each:
the Millennium-I and II, Bolshoi, and MultiDark simulations. The MultiDark (or
BigBolshoi) simulation is introduced in this paper. This suite of simulations
with high mass resolution over a large volume allows us to compute with
unprecedented accuracy the concentration over a large range of scales (about
six orders of magnitude in mass), which constitutes the state-of-the-art of our
current knowledge on this basic property of dark matter halos in the LCDM
cosmology. We find that there is consistency among the different simulation
data sets. We confirm a novel feature for halo concentrations at high
redshifts: a flattening and upturn with increasing mass. The concentration
c(M,z) as a function of mass and the redshift and for different cosmological
parameters shows a remarkably complex pattern. However, when expressed in terms
of the linear rms fluctuation of the density field sigma(M,z), the halo
concentration c(sigma) shows a nearly-universal simple U-shaped behaviour with
a minimum at a well defined scale at sigma=0.71. Yet, some small dependences
with redshift and cosmology still remain. At the high-mass end (sigma < 1) the
median halo kinematic profiles show large signatures of infall and highly
radial orbits. This c-sigma(M,z) relation can be accurately parametrized and
provides an analytical model for the dependence of concentration on halo mass.
When applied to galaxy clusters, our estimates of concentrations are
substantially larger -- by a factor up to 1.5 -- than previous results from
smaller simulations, and are in much better agreement with results of
observations. (abridged)Comment: Submitted to MNRA
Latin American Young Researchers and the Academic Labour Market Employment. A Case Study Analysis
The neoliberal model that has permeated higher education, has instrumentalised and commodified knowledge. This has forced academics to participate in the production of research to attract funding in the search of institutional stability. This paper problematizes the limited opportunities of integration of young Latin-American researchers in academic institutions. The purpose of this study is to explore the factors that hinder access to academia and unveil the weaknesses behind governmental policies for the development of employment programmes in both industry and academia. The methodology employed, is a critical discourse analysis of five biographies of Chilean and Mexican doctors. Results uncovered the use of discursive strategies that aim to legitimise reasons behind work fragility and the discursive construction of these actors. This article contributes to acknowledge similar patterns amongst Latin-American young researchers
Incident cervical HPV infections in young women: Transition probabilities for CIN and infection clearance
Background: We describe transition probabilities for incident human papillomavirus (HPV) 16/18/31/33/35/45/52/58/59 infections and cervical intraepithelial neoplasia (CIN) 1 lesions. Methods: Women ages 16 to 23 years underwent cytology and cervical swab PCR testing for HPV at approximately 6-month intervals for up to 4 years in the placebo arm of an HPV vaccine trial. The cumulative proportion of incident HPV infections with diagnosed CIN, clearing (infection undetectable), or persisting without CIN, were estimated. Results: Most incident infections cleared, without detection of CIN, ranging at 36 months from 66.9% for HPV31 to 91.1% for HPV59. There was little variation in the 36-month proportion of incident HPV16, 18, and 31 infections followed by a CIN1 lesion positive for the relevant HPV type (range 16.7%-18.6%), with lower risks for HPV59 (6.4%) and HPV33 (2.9%). Thirty-six-month transition probabilities for CIN2 ranged across types from 2.2% to 9.1%; however, the number of events was generally too small for statistically significant differences to be seen across types for this endpoint, or CIN3. Conclusions: Some incident HPV types appear more likely to result in diagnosed CIN1 than others. The relative predominance of HPV16, vis-à -vis some other high-risk HPV types (e.g., HPV33) in prevalent CIN2/3, appears more directly associated with relatively greater frequency of incident HPV16 infections within the population, than a higher risk of infection progression to CIN2/3. Impact: Nearly all incident HPV infections either manifest as detectable CIN or become undetectable within 36 months. Some HPV types (e.g., 16 and 33) appear to have similar risk of CIN2/3 despite widely varied incidence. ©2011 AACR
Molecular profiling of hepatocellular carcinoma in mice with a chronic deficiency of hepatic s-adenosylmethionine: relevance in human liver diseases
S-adenosylmethionine arises as a central molecule in the preservation of liver homeostasis as a chronic hepatic deficiency results in spontaneous development of steatohepatitis and hepatocellular carcinoma. In the present work, we have attempted a comprehensive analysis of proteins associated with hepatocarcinogenesis in MAT1A knock out mice using a combination of two-dimensional electrophoresis and mass spectrometry, to then apply the resulting information to identify hallmarks of human HCC. Our results suggest the existence of individual-specific factors that might condition the development of preneoplastic lesions. Proteomic analysis allowed the identification of 151 differential proteins in MAT1A-/- mice tumors. Among all differential proteins, 27 changed in at least 50% of the analyzed tumors, and some of these alterations were already detected months before the development of HCC in the KO liver. The expression level of genes coding for 13 of these proteins was markedly decreased in human HCC. Interestingly, seven of these genes were also found to be down-regulated in a pretumoral condition such as cirrhosis, while depletion of only one marker was assessed in less severe liver disorders
Redox regulation of methylthioadenosine phosphorylase in liver cells: molecular mechanism and functional implications
MTAP (5'-methylthioadenosine phosphorylase) catalyses the reversible phosphorolytic cleavage of methylthioadenosine leading to the production of methylthioribose-1-phosphate and adenine. Deficient MTAP activity has been correlated with human diseases including cirrhosis and hepatocellular carcinoma. In the present study we have investigated the regulation of MTAP by ROS (reactive oxygen species). The results of the present study support the inactivation of MTAP in the liver of bacterial LPS (lipopolysaccharide)-challenged mice as well as in HepG2 cells after exposure to t-butyl hydroperoxide. Reversible inactivation of purified MTAP by hydrogen peroxide results from a reduction of V(max) and involves the specific oxidation of Cys(136) and Cys(223) thiols to sulfenic acid that may be further stabilized to sulfenyl amide intermediates. Additionally, we found that Cys(145) and Cys(211) were disulfide bonded upon hydrogen peroxide exposure. However, this modification is not relevant to the mediation of the loss of MTAP activity as assessed by site-directed mutagenesis. Regulation of MTAP by ROS might participate in the redox regulation of the methionine catabolic pathway in the liver. Reduced MTA (5'-deoxy-5'-methylthioadenosine)-degrading activity may compensate for the deficient production of the precursor S-adenosylmethionine, allowing maintenance of intracellular MTA levels that may be critical to ensure cellular adaptation to physiopathological conditions such as inflammation
Site testing in summer at Dome C, Antarctica
We present summer site testing results based on DIMM data obtained at Dome C,
Antarctica. These data have been collected on the bright star Canopus during
two 3-months summer campaigns in 2003-2004 and 2004-2005. We performed
continuous monitoring of the seeing a nd the isoplanatic angle in the visible.
We found a median seeing of 0.54 \arcsec and a median isoplanatic angle of 6.8
\arcsec. The seeing appears to have a deep minimum around 0.4 \arcsec almost
every day in late afternoon
Angle-resolved photoemission study and first principles calculation of the electronic structure of GaTe
The electronic band structure of GaTe has been calculated by numerical atomic
orbitals density-functional theory, in the local density approximation. In
addition, the valence-band dispersion along various directions of the GaTe
Brillouin zone has been determined experimentally by angle-resolved
photoelectron spectroscopy. Along these directions, the calculated valence-band
structure is in good concordance with the valence-band dispersion obtained by
these measurements. It has been established that GaTe is a direct-gap
semiconductor with the band gap located at the Z point, that is, at Brillouin
zone border in the direction perpendicular to the layers. The valence-band
maximum shows a marked \textit{p}-like behavior, with a pronounced anion
contribution. The conduction band minimum arises from states with a comparable
\textit{s}- \textit{p}-cation and \textit{p}-anion orbital contribution.
Spin-orbit interaction appears to specially alter dispersion and binding energy
of states of the topmost valence bands lying at . By spin-orbit, it is
favored hybridization of the topmost \textit{p}-valence band with deeper
and flatter \textit{p}-\textit{p} bands and the valence-band minimum at
is raised towards the Fermi level since it appears to be determined by
the shifted up \textit{p}-\textit{p} bands.Comment: 7 text pages, 6 eps figures, submitted to PR
Reply to J.J. Muñoz-Perez et al. Comments on âConfirmation of beach accretion by grain-size trend analysis: Camposoto beach, CĂĄdiz, SWSpainâ by E. Poizot et al. (2013) Geo-Marine Letters 33(4)
In a novel finding for a beach environment, Poizot
et al. (2013) identified an FB+ trend (sediments becoming
finer, better sorted and more positively skewed upshore) on a
well-developed swash bar on the upper foreshore of the
Camposoto beach of CĂĄdiz in SW Spain. In their Discussion
of that paper, Muñoz-Perez et al. (2014) provide some
supporting arguments and also report grain-size, beach profile
and other data from nearby beaches which differ from those of
Poizot and colleagues for Camposoto beach, pointing out that
a trend observed on one beach may not apply to a
neighbouring beach. However, even though the absolute
values differ, the overall trends actually do show the same
general behaviour. In our Reply to their comments, we also
address some difficulties in comparing granulometric datasets
generated by different analytical techniques
All-particle cosmic ray energy spectrum measured by the HAWC experiment from 10 to 500 TeV
We report on the measurement of the all-particle cosmic ray energy spectrum
with the High Altitude Water Cherenkov (HAWC) Observatory in the energy range
10 to 500 TeV. HAWC is a ground based air-shower array deployed on the slopes
of Volcan Sierra Negra in the state of Puebla, Mexico, and is sensitive to
gamma rays and cosmic rays at TeV energies. The data used in this work were
taken from 234 days between June 2016 to February 2017. The primary cosmic-ray
energy is determined with a maximum likelihood approach using the particle
density as a function of distance to the shower core. Introducing quality cuts
to isolate events with shower cores landing on the array, the reconstructed
energy distribution is unfolded iteratively. The measured all-particle spectrum
is consistent with a broken power law with an index of prior to
a break at ) TeV, followed by an index of . The
spectrum also respresents a single measurement that spans the energy range
between direct detection and ground based experiments. As a verification of the
detector response, the energy scale and angular resolution are validated by
observation of the cosmic ray Moon shadow's dependence on energy.Comment: 16 pages, 11 figures, 4 tables, submission to Physical Review
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