227 research outputs found
Cross-correlation of WMAP 3rd year and the SDSS DR4 galaxy survey: new evidence for Dark Energy
We cross-correlate the third-year WMAP data with galaxy samples extracted
from the SDSS DR4 (SDSS4) covering 13% of the sky, increasing by a factor of
3.7 the volume sampled in previous analyses. The new measurements confirm a
positive cross-correlation with higher significance (total signal-to-noise of
about 4.7). The correlation as a function of angular scale is well fitted by
the integrated Sachs-Wolfe (ISW) effect for LCDM flat FRW models with a
cosmological constant. The combined analysis of different samples gives
Omega_L=0.80-0.850.77-0.86$ (95% CL). We find
similar best fit values for Omega_L for different galaxy samples with median
redshifts of z ~0.3 and z ~0.5, indicating that the data scale with redshift as
predicted by the LCDM cosmology (with equation of state parameter w=-1). This
agreement is not trivial, but can not yet be used to break the degeneracy
constraints in the w versus Omega_L plane using only the ISW data.Comment: 5 pages, final version to be published by MNRAS Let. Minor changes
with some additional clarification on error analysis don
Detection of Gravitational Lensing in the Cosmic Microwave Background
Gravitational lensing of the cosmic microwave background (CMB), a
long-standing prediction of the standard cosmolgical model, is ultimately
expected to be an important source of cosmological information, but first
detection has not been achieved to date. We report a 3.4 sigma detection, by
applying quadratic estimator techniques to all sky maps from the Wilkinson
Microwave Anisotropy Probe (WMAP) satellite, and correlating the result with
radio galaxy counts from the NRAO VLA Sky Survey (NVSS). We present our
methodology including a detailed discussion of potential contaminants. Our
error estimates include systematic uncertainties from density gradients in
NVSS, beam effects in WMAP, Galactic microwave foregrounds, resolved and
unresolved CMB point sources, and the thermal Sunyaev-Zeldovich effect.Comment: 27 pages, 20 figure
Cosmic Microwave Weak lensing data as a test for the dark universe
Combined analyses of WMAP 3-year and ACBAR Cosmic Microwave Anisotropies
angular power spectra have presented evidence for gravitational lensing >3
sigma level. This signal could provide a relevant test for cosmology. After
evaluating and confirming the statistical significance of the detection in
light of the new WMAP 5-year data, we constrain a new parameter A_L that scales
the lensing potential such that A_L=0 corresponds to unlensed while A_L=1 is
the expected lensed result. We find from WMAP5+ACBAR a 2.5 sigma indication for
a lensing contribution larger than expected, with A_L=3.1_{-1.5}^{+1.8} at 95%
c.l.. The result is stable under the assumption of different templates for an
additional Sunyaev-Zel'dovich foreground component or the inclusion of an extra
background of cosmic strings. We find negligible correlation with other
cosmological parameters as, for example, the energy density in massive
neutrinos. While unknown systematics may be present, dark energy or modified
gravity models could be responsible for the over-smoothness of the power
spectrum. Near future data, most notably from the Planck satellite mission,
will scrutinize this interesting possibility.Comment: 7 Pages, 3 Figure
ISW-LSS cross-correlation in coupled Dark Energy models with massive neutrinos
We provide an exhaustive analysis of the Integrated Sach-Wolfe effect (ISW)
in the context of coupled Dark Energy cosmologies where a component of massive
neutrinos is also present. We focus on the effects of both the coupling between
Dark Matter and Dark Energy and of the neutrino mass on the cross-correlation
between galaxy/quasar distributions and ISW effect. We provide a simple
expression to appropriately rescale the galaxy bias when comparing different
cosmologies. Theoretical predictions of the cross-correlation function are then
compared with observational data. We find that, while it is not possible to
distinguish among the models at low redshifts, discrepancies between coupled
models and CDM increase with . In spite of this, current data alone
seems not able to distinguish between coupled models and CDM. However,
we show that upcoming galaxy surveys will permit tomographic analysis which
allow to better discriminate among the models. We discuss the effects on
cross-correlation measurements of ignoring galaxy bias evolution, b(z), and
magnification bias correction and provide fitting formulae for b(z) for the
cosmologies considered. We compare three different tomographic schemes and
investigate how the expected signal to noise ratio, snr, of the ISW-LSS
cross-correlation changes when increasing the number of tomographic bins. The
dependence of snr on the area of the survey and the survey shot noise is also
discussed.Comment: 18 pages, 23 figures. Several major extensions. New sections and
figures was added. ApJ in prin
Tracing The Sound Horizon Scale With Photometric Redshift Surveys
We propose a new method for cosmological parameters extraction using the
baryon acoustic oscillation scale as a standard ruler in deep galaxy surveys
with photometric determination of redshifts. The method consists in a simple
empirical parametric fit to the angular 2-point correlation function w(theta).
It is parametrized as a power law to describe the continuum plus a Gaussian to
describe the BAO bump. The location of the Gaussian is used as the basis for
the measurement of the sound horizon scale. This method, although simple,
actually provides a robust estimation, since the inclusion of the power law and
the use of the Gaussian removes the shifts which affect the local maximum. We
discuss the effects of projection bias, non-linearities, redshift space
distortions and photo-z precision, and apply our method to a mock catalog of
the Dark Energy Survey, built upon a large N-body simulation provided by the
MICE collaboration. We discuss the main systematic errors associated to our
method and show that they are dominated by the photo-z uncertainty.Comment: 12 pages, 12 figures, published online in MNRAS, 25 October 201
Meropenem vs standard of care for treatment of neonatal late onset sepsis (NeoMero1): A randomised controlled trial.
BACKGROUND: The early use of broad-spectrum antibiotics remains the cornerstone for the treatment of neonatal late onset sepsis (LOS). However, which antibiotics should be used is still debatable, as relevant studies were conducted more than 20 years ago, recruited in single centres or countries, evaluated antibiotics not in clinical use anymore and had variable inclusion/exclusion criteria and outcome measures. Moreover, antibiotic-resistant bacteria have become a major problem in many countries worldwide. We hypothesized that efficacy of meropenem as a broad-spectrum antibiotic is superior to standard of care regimens (SOC) in empiric treatment of LOS and aimed to compare meropenem to SOC in infants aged 44 weeks meeting the Goldstein criteria of sepsis, were randomized in a 1:1 ratio to receive meropenem or one of the two SOC regimens (ampicillin+gentamicin or cefotaxime+gentamicin) chosen by each site prior to the start of the study for 8-14 days. The primary outcome was treatment success (survival, no modification of allocated therapy, resolution/improvement of clinical and laboratory markers, no need of additional antibiotics and presumed/confirmed eradication of pathogens) at test-of-cure visit (TOC) in full analysis set. Stool samples were tested at baseline and Day 28 for meropenem-resistant Gram-negative organisms (CRGNO). The primary analysis was performed in all randomised patients and in patients with culture confirmed LOS. Proportions of participants with successful outcome were compared by using a logistic regression model adjusted for the stratification factors. From September 3, 2012 to November 30th 2014, total of 136 patients (instead of planned 275) in each arm were randomized; 140 (52%) were culture positive. Successful outcome at TOC was achieved in 44/136 (32%) in the meropenem arm vs. 31/135 (23%) in the SOC arm (p = 0.087). The respective numbers in patients with positive cultures were 17/63 (27%) vs. 10/77 (13%) (p = 0.022). The main reason of failure was modification of allocated therapy. Treatment emergent adverse events occurred in 72% and serious adverse events in 17% of patients, the Day 28 mortality was 6%. Cumulative acquisition of CRGNO by Day 28 occurred in 4% of patients in the meropenem and 12% in the SOC arm (p = 0.052). CONCLUSIONS: Within this study population, we found no evidence that meropenem was superior to SOC in terms of success at TOC, short term hearing disturbances, safety or mortality were similar in both treatment arms but the study was underpowered to detect the planned effect. Meropenem treatment did not select for colonization with CRGNOs. We suggest that meropenem as broad-spectrum antibiotic should be reserved for neonates who are more likely to have Gram-negative LOS, especially in NICUs where microorganisms producing extended spectrum- and AmpC type beta-lactamases are circulating
Frontal Non-Invasive Neurostimulation Modulates Antisaccade Preparation in Non-Human Primates
A combination of oculometric measurements, invasive electrophysiological recordings and microstimulation have proven instrumental to study the role of the Frontal Eye Field (FEF) in saccadic activity. We hereby gauged the ability of a non-invasive neurostimulation technology, Transcranial Magnetic Stimulation (TMS), to causally interfere with frontal activity in two macaque rhesus monkeys trained to perform a saccadic antisaccade task. We show that online single pulse TMS significantly modulated antisaccade latencies. Such effects proved dependent on TMS site (effects on FEF but not on an actively stimulated control site), TMS modality (present under active but not sham TMS on the FEF area), TMS intensity (intensities of at least 40% of the TMS machine maximal output required), TMS timing (more robust for pulses delivered at 150 ms than at 100 post target onset) and visual hemifield (relative latency decreases mainly for ipsilateral AS). Our results demonstrate the feasibility of using TMS to causally modulate antisaccade-associated computations in the non-human primate brain and support the use of this approach in monkeys to study brain function and its non-invasive neuromodulation for exploratory and therapeutic purposes
Contribution to van der Waerden's conjecture
AbstractIn this paper, we give two different elementary proofs for the inequality which states that the permanent of doubly stochastic matrices is greater than or equal to (n!/nn). This inequality was proved earlier by the author, and independently by Egorychev and Falikman
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Impact of progressive global warming on the global-scale yield of maize and soybean
Global surface temperature is projected to warm over the coming decades, with regional differences expected in temperature change, rainfall and the frequency of extreme events. Temperature is a major determinant of crop growth and development, affecting planting date, growing season length and yield. We investigated the effects of increments of mean global temperature warming from 0.5 °C to 4 °C on soybean and maize development and yield, both globally and for the main producing countries, and simulated adaptation through changing planting date and variety. Increasing temperature resulted in reduced growing season lengths and ultimately reduced yields for both crops. The global yield for maize decreased as temperature increased, although the severity of the decrease was dependent on geographic region. Small temperature increases of 0.5 °C had no effect on soybean yield, although yield decreased as temperature increased. These negative effects, however, were partly compensated for by the implementation of adaptation strategies including planting earlier in the season and changing variety. The degree of compensation was dependent on geographical area and crop, with maize adaptation delaying the negative effects of temperature on yield, compared to soybean adaptation which increased yield in China, India and Korea DPR as well as delaying the effects in the remaining countries. The results of this paper indicate the degree to which farmer-controlled adaptation strategies can alleviate the negative impacts of increasing temperature on two major crop species
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