5,135 research outputs found
Reheating constraints and consistency relations of the Starobinsky model and some of its generalizations
Building on the success of the Starobinsky model in describing the
inflationary period of the universe, we investigate two simple generalizations
of this model and their constraints imposed by the reheating epoch. The first
generalization takes the form , while the second is the
-Starobinsky model. We first focus on the case where or
equivalently, , which corresponds to the original Starobinsky model.
We derive exact consistency relations between observables and cosmological
quantities, without neglecting any terms, and impose the reheating condition , where is the equation of state parameter
at the end of reheating. This allows us to obtain new bounds for and
that satisfy this condition and apply them to other observables and
cosmological quantities. We repeat this process for the cases where
and and find that these generalizations only result in minor
modifications of the Starobinsky model, including the potential and the bounds
on observables and cosmological quantities.Comment: 17 pages, 2 figure
The role of environment in the morphological transformation of galaxies in 9 intermediate redshift clusters
[abridged] We analyze a sample of 9 massive clusters at 0.4<z<0.6 observed
with MegaCam in 4 photometric bands (g,r,i,z) from the core to a radius of 5
Mpc (~4000 galaxies). Galaxy cluster candidates are selected using photometric
redshifts computed with HyperZ. Morphologies are estimated with galSVM in two
broad morphological types (early-type and late-type). We examine the
morphological composition of the red-sequence and the blue-cloud and study the
relations between galaxies and their environment through the morphology-density
relations (T-Sigma) and the morphology-radius relation (T-R) in a mass limited
sample (log(M/Msol)>9.5). We find that the red sequence is already in place at
z~0.5 and it is mainly composed of very massive (log(M/Msol)>11.3) early-type
galaxies. These massive galaxies seem to be already formed when they enter the
cluster, probably in infalling groups, since the fraction remains constant with
the cluster radius. Their presence in the cluster center could be explained by
a segregation effect reflecting an early assembly history. Any evolution that
takes place in the galaxy cluster population occurs therefore at lower masses
(10.3<log(M/Msol)<11.3). For these galaxies, the evolution, is mainly driven by
galaxy-galaxy interactions in the outskirts as revealed by the T-Sigma
relation. Finally, the majority of less massive galaxies (9.5<log(M/Msol)<10.3)
are late-type galaxies at all locations, suggesting that they have not started
the morphological transformation yet even if this low mass bin might be
affected by incompleteness.Comment: A&A in pres
Electrochemical Impedance Spectroscopy (EIS): A Review Study of Basic Aspects of the Corrosion Mechanism Applied to Steels
AC impedance measurements have been applied for over twenty years in electrochemistry and physics to investigate the electrical properties of conductive materials and their interfaces using an external electrical impulse (VOLTAGE, V or CURRENT, I) as driving force. Furthermore, its application has recently appeared to be destined in the Biotechnology field as an effective tool for rapid microbiologic diagnosis of living organism in situ. However, there is no doubt that the electrochemical impedance spectroscopy (EIS) is still one of the most useful techniques around the world for metal corrosion control and its monitoring. Corrosion has long been recognized as one of the most expensive stumbling blocks that concern many industries and government agencies, because it is a steel destructive phenomenon that occurs due to the chemical interaction with aqueous environments and takes place at the interface between metal and electrolyte producing an electrical charge transfer or ion diffusion process. Consequently, it is experimentally possible to determine through the EIS technique the mechanism and control that kinectics of corrosion reactions encounter. First, EIS data is collected through a potentiostat/
galvanostat apparatus. After, it is fitted to a mathematical model (i.e. an equivalent electrical circuit, EEC) for its interpretation and analysis, fundamentally seeking a meaningful physical interpretation. Finally, this review reports some basic aspects of the corrosion mechanism applied to steels through the experimental EIS response using Nyquist or Bode plots. Examples are given for different applied electrochemical impedance cases in which steel is under study intentionally exposed to a corrosive
aqueous solution by applying a sinusoidal potential at various test conditions
A Wide-Field Study of the z~0.8 Cluster RX J0152.7-1357: the Role of Environment in the Formation of the Red-Sequence
[ABRIDGED] We present the first results from the largest spectroscopic survey
to date of an intermediate redshift galaxy cluster, the z=0.834 cluster RX
J0152.7-1357. We use the colors of galaxies, assembled from a D~12 Mpc region
centered on the cluster, to investigate the properties of the red-sequence as a
function of density and clustercentric radius. Our wide-field multi-slit survey
with a low-dispersion prism in the IMACS spectrograph at Magellan allowed us to
identify 475 new members of the cluster and its surrounding large scale
structure with a redshift accuracy of dz/(1+z)~1% and a contamination rate of
~2% for galaxies with i<23.75 mag. We combine these new members with the 279
previously known spectroscopic members to give a total of 754 galaxies from
which we obtain a mass-limited sample of 300 galaxies with stellar masses
M>4x10^{10} M_sun. We find that the red galaxy fraction is 93+/-3% in the two
merging cores of the cluster and declines to a level of 64+/-3% at projected
clustercentric radii R>~3 Mpc. At these large projected distances, the
correlation between clustercentric radius and local density is nonexistent.
This allows an assessment of the influence of the local environment on galaxy
evolution, as opposed to mechanisms that operate on cluster scales. Even beyond
R>3 Mpc we find an increasing fraction of red galaxies with increasing local
density. The red fraction at the highest local densities in two groups at R>3
Mpc matches the red fraction found in the two cores. Strikingly, galaxies at
intermediate densities at R>3 Mpc, that are not group members, also show signs
of an enhanced red fraction. Our results point to such intermediate density
regions and the groups in the outskirts of the cluster, as sites where the
local environment influences the transition of galaxies onto the red-sequence.Comment: 15 pages, 10 figures, 1 table, accepted for publication in ApJ,
expanded introduction and additional references adde
Methicillin-Resistant Staphylococcus aureus in a Beauty Salon, the Netherlands
An outbreak of community-associated USA300 methicillin-resistant Staphylococcus aureus occurred in a beautician and 2 of her customers. Eight other persons, who were either infected (n = 5) or colonized (n = 3), were linked to this outbreak, including a family member, a household contact, and partners of customers
Evolution of the Early-Type Galaxy Fraction in Clusters since z = 0.8
We study the morphological content of a large sample of high-redshift
clusters to determine its dependence on cluster mass and redshift. Quantitative
morphologies are based on bulge+disk decompositions of cluster and field
galaxies on deep VLT/FORS2 images of 18 optically-selected clusters at 0.45 < z
< 0.80 from the ESO Distant Cluster Survey (EDisCS). Morphological content is
given by the early-type galaxy fraction f_et, and early-type galaxies are
selected based on their bulge fraction and image smoothness. A set of 158 SDSS
clusters is analyzed exactly as the EDisCS sample to provide a robust local
comparison. Our main results are: (1) f_et values for the SDSS and EDisCS
clusters exhibit no clear trend as a function of sigma. (2) Mid-z EDisCS
clusters around sigma = 500 km/s have f_et ~= 0.5 whereas high-z EDisCS
clusters have f_et ~= 0.4 (~25% increase over 2 Gyrs). (3) There is a marked
difference in the morphological content of EDisCS and SDSS clusters. None of
the EDisCS clusters have f_et greater than 0.6 whereas half of the SDSS
clusters lie above this value. This difference is seen in clusters of all
velocity dispersions. (4) There is a strong correlation between morphology and
star formation in SDSS and EDisCS clusters. This correlation holds independent
of sigma and z even though the fraction of [OII] emitters decreases from z~0.8
to z~0.06 in all environments. Our results pose an interesting challenge to
structural transformation and star formation quenching processes that strongly
depend on the global cluster environment and suggest that cluster membership
may be of lesser importance than other variables in determining galaxy
properties. (ABRIDGED)Comment: 22 pages, 10 figures, accepted for publication in A&
Age- and Gender-Related Changes in Contractile Properties of Non-Atrophied EDL Muscle
Background: In humans, ageing causes skeletal muscles to become atrophied, weak, and easily fatigued. In rodent studies, ageing has been associated with significant muscle atrophy and changes in the contractile properties of the muscles. However, it is not entirely clear whether these changes in contractile properties can occur before there is significant atrophy, and whether males and females are affected differently. Methods and Results: We investigated various contractile properties of whole isolated fast-twitch EDL muscles from adult (2–6 months-old) and aged (12–22 months-old) male and female mice. Atrophy was not present in the aged mice. Compared with adult mice, EDL muscles of aged mice had significantly lower specific force, longer tetanus relaxation times, and lower fatiguability. In the properties of absolute force and muscle relaxation times, females were affected by ageing to a greater extent than males. Additionally, EDL muscles from a separate group of male mice were subjected to eccentric contractions of 15 % strain, and larger force deficits were found in aged than in adult mice. Conclusion: Our findings provide further insight into the muscle atrophy, weakness and fatiguability experienced by the elderly. We have shown that even in the absence of muscle atrophy, there are definite alterations in the physiological properties of whole fast-twitch muscle from ageing mice, and for some of these properties the alterations are mor
Epidemiology of community-onset Staphylococcus aureus infections in pediatric patients: an experience at a Children's Hospital in central Illinois
<p>Abstract</p> <p>Background</p> <p>The nation-wide concern over methicillin-resistant <it>Staphylococcus aureus </it>(MRSA) has prompted many clinicians to use vancomycin when approaching patients with suspected staphylococcal infections. We sought to characterize the epidemiology of community-onset <it>S. aureus </it>infections in hospitalized children to assist local clinicians in providing appropriate empiric antimicrobial therapy.</p> <p>Methods</p> <p>From January 2005–June 2008, children (0–18 years old) admitted to the Children's Hospital of Illinois with community-onset <it>S. aureus </it>infections were identified by a computer-assisted laboratory-based surveillance and medical record review.</p> <p>Results</p> <p>Of 199 patients, 67 (34%) had invasive infections, and 132 (66%) had skin and soft tissue infections (SSTIs). Among patients with invasive infections, <it>S. aureus </it>isolates were more likely to be susceptible to methicillin (MSSA 63% vs. MRSA 37%), whereas patients with SSTIs, <it>S. aureus </it>isolates were more likely to be resistant to methicillin (MRSA 64% vs. MSSA 36%). Bacteremia and musculoskeletal infections were the most common invasive infections in both groups of <it>S. aureus</it>. Pneumonia with empyema was more likely to be caused by MRSA (<it>P </it>= 0.02). The majority (~90%) of MRSA isolates were non-multidrug resistant, even in the presence of healthcare-associated risk factors.</p> <p>Conclusion</p> <p>Epidemiological data at the local level is important for antimicrobial decision-making. MSSA remains an important pathogen causing invasive community-onset <it>S. aureus </it>infections among hospitalized children. In our hospital, nafcillin in combination with vancomycin is recommended empiric therapy in critically ill patients with suspected invasive staphylococcal infections. Because up to 25% of MSSA circulating in our area are clindamycin-resistant, clindamycin should be used cautiously as empiric monotherapy in patients with suspected invasive staphylococcal infections.</p
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High tide or riptide on the cosmic shoreline? A water-rich atmosphere or stellar contamination for the warm super-Earth GJ 486b from JWST observations
Planets orbiting M-dwarf stars are prime targets in the search for rocky exoplanet atmospheres. The small size of M dwarfs renders their planets exceptional targets for transmission spectroscopy, facilitating atmospheric characterization. However, it remains unknown whether their host stars' highly variable extreme-UV radiation environments allow atmospheres to persist. With JWST, we have begun to determine whether or not the most favorable rocky worlds orbiting M dwarfs have detectable atmospheres. Here, we present a 2.8–5.2 μm JWST NIRSpec/G395H transmission spectrum of the warm (700 K, 40.3× Earth's insolation) super-Earth GJ 486b (1.3 R⊕ and 3.0 M⊕). The measured spectrum from our two transits of GJ 486b deviates from a flat line at 2.2σ − 3.3σ, based on three independent reductions. Through a combination of forward and retrieval models, we determine that GJ 486b either has a water-rich atmosphere (with the most stringent constraint on the retrieved water abundance of H2O > 10% to 2σ) or the transmission spectrum is contaminated by water present in cool unocculted starspots. We also find that the measured stellar spectrum is best fit by a stellar model with cool starspots and hot faculae. While both retrieval scenarios provide equal quality fits () to our NIRSpec/G395H observations, shorter wavelength observations can break this degeneracy and reveal if GJ 486b sustains a water-rich atmosphere
Transfer of SCN1A to the brain of adolescent mouse model of Dravet syndrome improves epileptic, motor, and behavioral manifestations
Dravet syndrome is a genetic encephalopathy characterized by severe epilepsy combined with motor, cognitive, and behavioral abnormalities. Current antiepileptic drugs achieve only partial control of seizures and provide little benefit on the patient’s neurological development. In >80% of cases, the disease is caused by haploinsufficiency of the SCN1A gene, which encodes the alpha subunit of the Nav1.1 voltage-gated sodium channel. Novel therapies aim to restore SCN1A expression in order to address all disease manifestations. We provide evidence that a high-capacity adenoviral vector harboring the 6-kb SCN1A cDNA is feasible and able to express functional Nav1.1 in neurons. In vivo, the best biodistribution was observed after intracerebral injection in basal ganglia, cerebellum, and prefrontal cortex. SCN1A A1783V knockin mice received the vector at 5 weeks of age, when most neurological alterations were present. Animals were protected from sudden death, and the epileptic phenotype was attenuated. Improvement of motor performance and interaction with the environment was observed. In contrast, hyperactivity persisted, and the impact on cognitive tests was variable (success in novel object recognition and failure in Morris water maze tests). These results provide proof of concept for gene supplementation in Dravet syndrome and indicate new directions for improvement
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