142 research outputs found
Polymer Chain Generation for Coarse-Grained Models Using Radical-Like Polymerization
International audienceThis paper presents major improvements in the efficiency of the so-called Radical-Like Polymerization (RLP) algorithm proposed in ”Polymer chain generation for coarse-grained models using radical-like polymerization” [J. Chem. Phys. 128 (2008)]. Three enhancements are detailed in this paper: (1) the capture radius of a radical is enlarged to increase the probability of finding a neighboring monomer; (2) between each growth step, equilibration is now performed with increasing the relaxation time depending on the actual chain size; (3) the RLP algorithm is now fully parallelized and proposed as a “fix” within the “Lammps” molecular dynamics simulation suite
Bizonal cardiac engineered tissues with differential maturation features in a mid-throughput multimodal bioreactor
Functional three-dimensional (3D) engineered cardiac tissue (ECT) models are essential for effective drug screening and biological studies. Application of physiological cues mimicking those typical of the native myocardium is known to promote the cardiac maturation and functionality in vitro. Commercially available bioreactors can apply one physical force type at a time and often in a restricted loading range. To overcome these limitations, a millimetric-scalemicroscope-integrated bioreactor was developed to deliver multiple biophysical stimuli to ECTs. In this study, we showed that the single application of auxotonic loading (passive) generated a bizonal ECT with a unique cardiac maturation pattern. Throughout the statically cultured constructs and in the ECT region exposed to high passive loading, cardiomyocytes predominantly displayed a round morphology and poor contractility ability. The ECT region with a low passive mechanical stimulation instead showed both rat- and human-origin cardiac cell maturation and organization, as well as increased ECT functionality
A D-band 3D printed antenna
This paper reports the design and fabrication of a novel all-metal antenna operating in the millimeter-wave band. Based on the resonant cavity antenna (RCA) concept, the principle of antenna operation is explained, and a parametric study of several key design parameters is provided. A novel impedance matching technique is introduced to broaden the antenna return loss bandwidth. Two gain enhancement methods have been employed to achieve a more directive beam with reduced side lobes and back lobes. The D-band antenna prototypes are produced using i) all-metal printing without any post-processing; ii) dielectric printing with copper metallization applied later. Comparisons of the simulated and measured results amongst the antennas fabricated using the two additive manufacturing techniques are made. Measurement results of the two antenna prototypes show that the proposed design can achieve a 14.2% bandwidth with a maximum gain of 15.5 dBi at 135 GHz. The present work is the first D-band resonant cavity antenna fabricated using two different 3D printing methods
Epithelial Cell Gene Expression Induced by Intracellular Staphylococcus aureus
HEp-2 cell monolayers were cocultured with intracellular Staphylococcus aureus, and changes in gene expression were profiled using DNA microarrays. Intracellular S. aureus affected genes involved in cellular stress responses, signal transduction, inflammation, apoptosis, fibrosis, and cholesterol biosynthesis. Transcription of stress response and signal transduction-related genes including atf3, sgk, map2k1, map2k3, arhb, and arhe was increased. In addition, elevated transcription of proinflammatory genes was observed for tnfa, il1b, il6, il8, cxcl1, ccl20, cox2, and pai1. Genes involved in proapoptosis and fibrosis were also affected at transcriptional level by intracellular S. aureus. Notably, intracellular S. aureus induced strong transcriptional down-regulation of several cholesterol biosynthesis genes. These results suggest that epithelial cells respond to intracellular S. aureus by inducing genes affecting immunity and in repairing damage caused by the organism, and are consistent with the possibility that the organism exploits an intracellular environment to subvert host immunity and promote colonization
Geocentrism reexamined
The universe is nearly isotropic on very large scales. It is much more
difficult to show that the universe is radially homogeneous (independent of
distance), or equivalently, that it is isotropic about distant points. This
taken as an axiom, since if it were not true, then we would occupy a preferred
position. This paper considers several empirical arguments for radial
homogeneity based on the cosmic microwave background (CMB). The tightest limits
on inhomogeneity on the scale of the horizon are of order ten percent but will
improve soon. These limits involve the Sunyaev-Zel'dovich effect in clusters of
galaxies, excitation of low-energy atomic transitions, and the accurately
thermal spectrum of the CMB. Weaker limits from primordial nucleosynthesis are
discussed briefly.Comment: RevTeX source, 14 pages, no figs. To appear Phys Rev
Risk adjustment for inter-hospital comparison of primary cesarean section rates: need, validity and parsimony
BACKGROUND: Cesarean section rates is often used as an indicator of quality of care in maternity hospitals. The assumption is that lower rates reflect in developed countries more appropriate clinical practice and general better performances. Hospitals are thus often ranked on the basis of caesarean section rates. The aim of this study is to assess whether the adjustment for clinical and sociodemographic variables of the mother and the fetus is necessary for inter-hospital comparisons of cesarean section (c-section) rates and to assess whether a risk adjustment model based on a limited number of variables could be identified and used. METHODS: Discharge abstracts of labouring women without prior cesarean were linked with abstracts of newborns discharged from 29 hospitals of the Emilia-Romagna Region (Italy) from 2003 to 2004. Adjusted ORs of cesarean by hospital were estimated by using two logistic regression models: 1) a full model including the potential confounders selected by a backward procedure; 2) a parsimonious model including only actual confounders identified by the "change-in-estimate" procedure. Hospital rankings, based on ORs were examined. RESULTS: 24 risk factors for c-section were included in the full model and 7 (marital status, maternal age, infant weight, fetopelvic disproportion, eclampsia or pre-eclampsia, placenta previa/abruptio placentae, malposition/malpresentation) in the parsimonious model. Hospital ranking using the adjusted ORs from both models was different from that obtained using the crude ORs. The correlation between the rankings of the two models was 0.92. The crude ORs were smaller than ORs adjusted by both models, with the parsimonious ones producing more precise estimates. CONCLUSION: Risk adjustment is necessary to compare hospital c-section rates, it shows differences in rankings and highlights inappropriateness of some hospitals. By adjusting for only actual confounders valid and more precise estimates could be obtained
Observations of Milky Way Dwarf Spheroidal galaxies with the Fermi-LAT detector and constraints on Dark Matter models
We report on the observations of 14 dwarf spheroidal galaxies with the Fermi
Gamma-Ray Space Telescope taken during the first 11 months of survey mode
operations. The Fermi telescope provides a new opportunity to test particle
dark matter models through the expected gamma-ray emission produced by pair
annihilation of weakly interacting massive particles (WIMPs). Local Group dwarf
spheroidal galaxies, the largest galactic substructures predicted by the cold
dark matter scenario, are attractive targets for such indirect searches for
dark matter because they are nearby and among the most extreme dark matter
dominated environments. No significant gamma-ray emission was detected above
100 MeV from the candidate dwarf galaxies. We determine upper limits to the
gamma-ray flux assuming both power-law spectra and representative spectra from
WIMP annihilation. The resulting integral flux above 100 MeV is constrained to
be at a level below around 10^-9 photons cm^-2 s^-1. Using recent stellar
kinematic data, the gamma-ray flux limits are combined with improved
determinations of the dark matter density profile in 8 of the 14 candidate
dwarfs to place limits on the pair annihilation cross-section of WIMPs in
several widely studied extensions of the standard model. With the present data,
we are able to rule out large parts of the parameter space where the thermal
relic density is below the observed cosmological dark matter density and WIMPs
(neutralinos here) are dominantly produced non-thermally, e.g. in models where
supersymmetry breaking occurs via anomaly mediation. The gamma-ray limits
presented here also constrain some WIMP models proposed to explain the Fermi
and PAMELA e^+e^- data, including low-mass wino-like neutralinos and models
with TeV masses pair-annihilating into muon-antimuon pairs. (Abridged)Comment: 25 pages, 4 figures, accepted to ApJ, Corresponding authors: J.
Cohen-Tanugi, C. Farnier, T.E. Jeltema, E. Nuss, and S. Profum
Fermi LAT Observations of LS I +61 303: First detection of an orbital modulation in GeV Gamma Rays
This Letter presents the first results from the observations of LSI +61 303
using Large Area Telescope data from the Fermi Gamma-Ray Space Telescope
between 2008 August and 2009 March. Our results indicate variability that is
consistent with the binary period, with the emission being modulated at 26.6
+/- 0.5 days. This constitutes the first detection of orbital periodicity in
high-energy gamma rays (20 MeV-100 GeV, HE). The light curve is characterized
by a broad peak after periastron, as well as a smaller peak just before
apastron. The spectrum is best represented by a power law with an exponential
cutoff, yielding an overall flux above 100 MeV of 0.82 +/- 0.03(stat) +/-
0.07(syst) 10^{-6} ph cm^{-2} s^{-1}, with a cutoff at 6.3 +/- 1.1(stat) +/-
0.4(syst) GeV and photon index Gamma = 2.21 +/- 0.04(stat) +/- 0.06(syst).
There is no significant spectral change with orbital phase. The phase of
maximum emission, close to periastron, hints at inverse Compton scattering as
the main radiation mechanism. However, previous very high-energy gamma ray
(>100 GeV, VHE) observations by MAGIC and VERITAS show peak emission close to
apastron. This and the energy cutoff seen with Fermi suggest the link between
HE and VHE gamma rays is nontrivial.Comment: 7 pages, 5 figures, accepted for publication in ApJ Letters 21 July
200
Fermi observations of high-energy gamma-ray emission from GRB 080825C
The Fermi Gamma-ray Space Telescope (FGST) has opened a new high-energy
window in the study of Gamma-Ray Bursts (GRBs). Here we present a thorough
analysis of GRB 080825C, which triggered the Fermi Gamma-ray Burst Monitor
(GBM), and was the first firm detection of a GRB by the Fermi Large Area
Telescope (LAT). We discuss the LAT event selections, background estimation,
significance calculations, and localization for Fermi GRBs in general and GRB
080825C in particular. We show the results of temporal and time-resolved
spectral analysis of the GBM and LAT data. We also present some theoretical
interpretation of GRB 080825C observations as well as some common features
observed in other LAT GRBs.Comment: 18 pages, 7 figures. Accepted for publication in ApJ. Corresponding
authors: A. Bouvier, J. Granot, A.J. van der Hors
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