6,497 research outputs found
Hawking Radiation and Unitary evolution
We find a family of exact solutions to the semi-classical equations
(including back-reaction) of two-dimensional dilaton gravity, describing
infalling null matter that becomes outgoing and returns to infinity without
forming a black hole. When a black hole almost forms, the radiation reaching
infinity in advance of the original outgoing null matter has the properties of
Hawking radiation. The radiation reaching infinity after the null matter
consists of a brief burst of negative energy that preserves unitarity and
transfers information faster than the theoretical bound for positive energy.Comment: LaTex file + uuencoded ps version including 4 figure
A multicountry randomized controlled trial of comprehensive maternal nutrition supplementation initiated before conception: the Women First trial.
Background: Reported benefits of maternal nutrition supplements commenced during pregnancy in low-resource populations have typically been quite limited.
Objectives: This study tested the effects on newborn size, especially length, of commencing nutrition supplements for women in low-resource populations ≥3 mo before conception (Arm 1), compared with the same supplement commenced late in the first trimester of pregnancy (Arm 2) or not at all (control Arm 3).
Methods: Women First was a 3-arm individualized randomized controlled trial (RCT). The intervention was a lipid-based micronutrient supplement; a protein-energy supplement was also provided if maternal body mass index (kg/m2) was(DRC), Guatemala, India, and Pakistan. The primary outcome was length-for-age z score (LAZ), with all anthropometry obtainedDRC, outcomes were determined for all 4 sites from WHO newborn standards (non-gestational-age-adjusted, NGAA) as well as INTERGROWTH-21st fetal standards (3 sites, gestational age-adjusted, GAA).
Results: A total of 7387 nonpregnant women were randomly assigned, yielding 2451 births with NGAA primary outcomes and 1465 with GAA outcomes. Mean LAZ and other outcomes did not differ between Arm 1 and Arm 2 using either NGAA or GAA. Mean LAZ (NGAA) for Arm 1 was greater than for Arm 3 (effect size: +0.19; 95% CI: 0.08, 0.30, P = 0.0008). For GAA outcomes, rates of stunting and small-for-gestational-age were lower in Arm 1 than in Arm 3 (RR: 0.69; 95% CI: 0.49, 0.98, P = 0.0361 and RR: 0.78; 95% CI: 0.70, 0.88, P \u3c 0.001, respectively). Rates of preterm birth did not differ among arms.
Conclusions: In low-resource populations, benefits on fetal growth-related birth outcomes were derived from nutrition supplements commenced before conception or late in the first trimester. This trial was registered at clinicaltrials.gov as NCT01883193
Predictability and Semiclassical Approximation at the onset of Black Hole formation
We combine analytical and numerical techniques to study the collapse of
conformally coupled massless scalar fields in semiclassical 2D dilaton gravity,
with emphasis on solutions just below criticality when a black hole almost
forms. We study classical information and quantum correlations. We show
explicitly how recovery of information encoded in the classical initial data
from the outgoing classical radiation becomes more difficult as criticality is
approached. The outgoing quantum radiation consists of a positive-energy flux,
which is essentially the standard Hawking radiation, followed by a
negative-energy flux which ensures energy conservation and guarantees unitary
evolution through strong correlations with the positive-energy Hawking
radiation. As one reaches the critical solution there is a breakdown of
unitarity. We show that this breakdown of predictability is intimately related
to a breakdown of the semiclassical approximation.Comment: 26 pages RevTex + 8 figures in a separate postscript fil
Low-dose aspirin for the prevention of preterm delivery in nulliparous women with a singleton pregnancy (ASPIRIN): a randomised, double-blind, placebo-controlled trial.
BACKGROUND: Preterm birth remains a common cause of neonatal mortality, with a disproportionately high burden in low-income and middle-income countries. Meta-analyses of low-dose aspirin to prevent pre-eclampsia suggest that the incidence of preterm birth might also be decreased, particularly if initiated before 16 weeks of gestation.
METHODS: ASPIRIN was a randomised, multicountry, double-masked, placebo-controlled trial of low-dose aspirin (81 mg daily) initiated between 6 weeks and 0 days of pregnancy, and 13 weeks and 6 days of pregnancy, in nulliparous women with an ultrasound confirming gestational age and a singleton viable pregnancy. Participants were enrolled at seven community sites in six countries (two sites in India and one site each in the Democratic Republic of the Congo, Guatemala, Kenya, Pakistan, and Zambia). Participants were randomly assigned (1:1, stratified by site) to receive aspirin or placebo tablets of identical appearance, via a sequence generated centrally by the data coordinating centre at Research Triangle Institute International (Research Triangle Park, NC, USA). Treatment was masked to research staff, health providers, and patients, and continued until 36 weeks and 7 days of gestation or delivery. The primary outcome of incidence of preterm birth, defined as the number of deliveries before 37 weeks\u27 gestational age, was analysed in randomly assigned women with pregnancy outcomes at or after 20 weeks, according to a modified intention-to-treat (mITT) protocol. Analyses of our binary primary outcome involved a Cochran-Mantel-Haenszel test stratified by site, and generalised linear models to obtain relative risk (RR) estimates and associated confidence intervals. Serious adverse events were assessed in all women who received at least one dose of drug or placebo. This study is registered with ClinicalTrials.gov, NCT02409680, and the Clinical Trial Registry-India, CTRI/2016/05/006970.
FINDINGS: From March 23, 2016 to June 30, 2018, 14 361 women were screened for inclusion and 11 976 women aged 14-40 years were randomly assigned to receive low-dose aspirin (5990 women) or placebo (5986 women). 5780 women in the aspirin group and 5764 in the placebo group were evaluable for the primary outcome. Preterm birth before 37 weeks occurred in 668 (11·6%) of the women who took aspirin and 754 (13·1%) of those who took placebo (RR 0·89 [95% CI 0·81 to 0·98], p=0·012). In women taking aspirin, we also observed significant reductions in perinatal mortality (0·86 [0·73-1·00], p=0·048), fetal loss (infant death after 16 weeks\u27 gestation and before 7 days post partum; 0·86 [0·74-1·00], p=0·039), early preterm delivery (\u3c34 \u3eweeks; 0·75 [0·61-0·93], p=0·039), and the incidence of women who delivered before 34 weeks with hypertensive disorders of pregnancy (0·38 [0·17-0·85], p=0·015). Other adverse maternal and neonatal events were similar between the two groups.
INTERPRETATION: In populations of nulliparous women with singleton pregnancies from low-income and middle-income countries, low-dose aspirin initiated between 6 weeks and 0 days of gestation and 13 weeks and 6 days of gestation resulted in a reduced incidence of preterm delivery before 37 weeks, and reduced perinatal mortality.
FUNDING: Eunice Kennedy Shriver National Institute of Child Health and Human Development
The contribution of financial entities to the sustainable development through the reporting of corporate social responsibility information
This paper aims at examining the relationship between board composition and corporate
social responsibility (CSR) of a sample of listed financial entities, discussing the driving
reasons of these entities to disclose CSR information. We hypothesize that there is a positive
association between outside (institutional and independent directors) and female directors and
CSR disclosure and a negative relationship between inside directors and CSR reporting. Our
findings provide evidence that the proportions of independent directors and female directors
on boards encourage CSR disclosure. Moreover, the results also show that the proportions of
inside directors and institutional directors on boards do not have influence on CSR reporting.
Thus, our evidence suggests that board attributes such as independent and female directors
encourage financial entities to report CSR matters, showing the effectiveness of these two
corporate governance mechanisms. The paper shed light on the influence of board structure of
financial entities on CSR disclosure. Therefore, this study contributes to past research by
providing an index to measure CSR disclosure of financial entities and the importance of the
distinction between outside and inside directors
Three-Dimensional Gravity with Conformal Scalar and Asymptotic Virasoro Algebra
Strominger has derived the Bekenstein-Hawking entropy of the BTZ black hole
using asymptotic Virasoro algebra. We apply Strominger's method to a black hole
solution found by Martinez and Zanelli (MZ). This is a solution of
three-dimensional gravity with a conformal scalar field. The solution is not
, but it is asymptotically ; therefore, it has the asymptotic
Virasoro algebra. We compute the central charge for the theory and compares
Cardy's formula with the Bekenstein-Hawking entropy. It turns out that the
functional form does agree, but the overall numerical coefficient does not.
This is because this approach gives the "maximum possible entropy" for the
numerical coefficient.Comment: 26 pages, LaTeX; v2: minor correction
New Physics at the LHC. A Les Houches Report: Physics at TeV Colliders 2009 - New Physics Working Group
We present a collection of signatures for physics beyond the standard model
that need to be explored at the LHC. First, are presented various tools
developed to measure new particle masses in scenarios where all decays include
an unobservable particle. Second, various aspects of supersymmetric models are
discussed. Third, some signatures of models of strong electroweak symmetry are
discussed. In the fourth part, a special attention is devoted to high mass
resonances, as the ones appearing in models with warped extra dimensions.
Finally, prospects for models with a hidden sector/valley are presented. Our
report, which includes brief experimental and theoretical reviews as well as
original results, summarizes the activities of the "New Physics" working group
for the "Physics at TeV Colliders" workshop (Les Houches, France, 8-26 June,
2009).Comment: 189 page
Kinetic modelling of competition and depletion of shared miRNAs by competing endogenous RNAs
Non-conding RNAs play a key role in the post-transcriptional regulation of
mRNA translation and turnover in eukaryotes. miRNAs, in particular, interact
with their target RNAs through protein-mediated, sequence-specific binding,
giving rise to extended and highly heterogeneous miRNA-RNA interaction
networks. Within such networks, competition to bind miRNAs can generate an
effective positive coupling between their targets. Competing endogenous RNAs
(ceRNAs) can in turn regulate each other through miRNA-mediated crosstalk.
Albeit potentially weak, ceRNA interactions can occur both dynamically,
affecting e.g. the regulatory clock, and at stationarity, in which case ceRNA
networks as a whole can be implicated in the composition of the cell's
proteome. Many features of ceRNA interactions, including the conditions under
which they become significant, can be unraveled by mathematical and in silico
models. We review the understanding of the ceRNA effect obtained within such
frameworks, focusing on the methods employed to quantify it, its role in the
processing of gene expression noise, and how network topology can determine its
reach.Comment: review article, 29 pages, 7 figure
Ultracold atomic gases in optical lattices: mimicking condensed matter physics and beyond
We review recent developments in the physics of ultracold atomic and
molecular gases in optical lattices. Such systems are nearly perfect
realisations of various kinds of Hubbard models, and as such may very well
serve to mimic condensed matter phenomena. We show how these systems may be
employed as quantum simulators to answer some challenging open questions of
condensed matter, and even high energy physics. After a short presentation of
the models and the methods of treatment of such systems, we discuss in detail,
which challenges of condensed matter physics can be addressed with (i)
disordered ultracold lattice gases, (ii) frustrated ultracold gases, (iii)
spinor lattice gases, (iv) lattice gases in "artificial" magnetic fields, and,
last but not least, (v) quantum information processing in lattice gases. For
completeness, also some recent progress related to the above topics with
trapped cold gases will be discussed.Comment: Review article. v2: published version, 135 pages, 34 figure
- …