Asymmetries in t tbar production: LHC versus Tevatron

The measurement of a charge asymmetry in t tbar production at LHC constitutes more than an independent confirmation of the forward-backward asymmetry found at Tevatron. Indeed, both measurements together can be used to identify the source of the asymmetry. This is demonstrated for the case of new Z', W' vector bosons and colour-sextet and triplet scalars, exchanged in t, u channels respectively, and a very heavy axigluon in the s channel.Comment: LaTeX 5 pages. Updated with discussion on implications of summer results. Final version to appear in PR

Asymmetries in top quark pair production at hadron colliders

We review the asymmetries in top quark pair production at the Tevatron and the LHC. We summarize the experimental measurements and the interpretations of a possible excess in terms of new physics. We also review other top quark properties-emphasizing effects related to the $t \bar t$ asymmetries-as well as other collider signals.Comment: RevTeX 40 pages. Final version to be published in Reviews of Modern Physics, with several addition

Constraining differential renormalization in abelian gauge theories

We present a procedure of differential renormalization at the one loop level which avoids introducing unnecessary renormalization constants and automatically preserves abelian gauge invariance. The amplitudes are expressed in terms of a basis of singular functions. The local terms appearing in the renormalization of these functions are determined by requiring consistency with the propagator equation. Previous results in abelian theories, with and without supersymmetry, are discussed in this context.Comment: 13 pages, LaTeX. Some equations corrected and a reference added. Complete ps paper also available at http://www-ftae.ugr.es/papiros.html or ftp://ftae3.ugr.es/pub/rmt/ugft73.p

CPT, Lorentz invariance and anomalous clash of symmetries

In this paper we first discuss the analysis regarding the role of Lorentz symmetry in the perturbative non-gravitational anomalies for a family of fermions, which has been recently performed in arXiv:0809.0184. The theory is assumed to be translational invariant, power-counting renormalizable and based on a local action, but is allowed to have general Lorentz violating operators, including those that break CPT. The main result is that Lorentz symmetry does not participate in the clash of symmetries that leads to the anomalies. Moreover, here we provide a simple "semiclassical" argument that shortly illustrates the origin of this fact.Comment: 8 pages, no figures. To appear in the proceedings of Discrete '08: Symposium on Prospects in the Physics of Discrete Symmetries, Valencia, Spain, 11-16 Dec 200

Did Medicaid Slow Declines in Access to Health Care during the Great Recession?

OBJECTIVE: We examine whether broadened access to Medicaid helped insulate households from declines in health coverage and health care access linked to the 2007-2009 Great Recession. DATA SOURCE: 2004-2010 Behavioral Risk Factor Surveillance System (BRFSS). STUDY DESIGN: Flexible difference-in-difference regressions were used to compare the impact of county-level unemployment on health care access in states with generous Medicaid eligibility guidelines versus states with restrictive guidelines. DATA COLLECTION/EXTRACTION METHODS: Nonelderly adults (aged 19-64) in the BRFSS were linked to county unemployment rates from the Bureau of Labor Statistics\u27 Local Area Unemployment Statistics Program. We created a Medicaid generosity index by simulating the share of a nationally representative sample of adults that would be eligible for Medicaid under each state\u27s 2007 Medicaid guidelines using data from the 2007 Current Population Survey\u27s Annual Social and Economic Supplement. PRINCIPAL FINDINGS: A percentage point (PPT) increase in the county unemployment rate was associated with a 1.3 PPT (95% CI: 0.9-1.6, P \u3c .01) increase in the likelihood of being uninsured and a 0.86 PPT (95% CI: 0.6-1.1, P \u3c .01) increase in unmet medical needs due to cost in states with restrictive Medicaid eligibility guidelines. Conversely, a one PPT increase in unemployment was associated with only a 0.64 PPT (P \u3c .01) increase in uninsurance among states with the most generous eligibility guidelines. Among states in the fourth quartile of generosity (ie, most generous), rises in county-level unemployment were associated with a 0.68 PPT (P \u3c .10) increase in unmet medical needs due to cost—a 21% smaller decrease relative to states with the most restrictive Medicaid eligibility guidelines. CONCLUSIONS: Increased access to Medicaid during the Great Recession mitigated the effects of increased unemployment on the rate of unmet medical need, particularly for adults with limited income

Non-relativistic electron-electron interaction in a Maxwell-Chern-Simons-Proca model endowed with a timelike Lorentz-violating background

A planar Maxwell-Chern-Simons-Proca model endowed with a Lorentz-violating background is taken as framework to investigate the electron-electron interaction. The Dirac sector is introduced exhibiting a Yukawa and a minimal coupling with the scalar and the gauge fields, respectively. The the electron-electron interaction is then exactly evaluated as the Fourier transform of the Moller scattering amplitude (carried out in the non-relativistic limit) for the case of a purely time-like background. The interaction potential exhibits a totally screened behavior far from the origin as consequence of massive character of the physical mediators. The total interaction (scalar plus gauge potential) can always be attractive, revealing that this model may lead to the formation of electron-electron bound states.Comment: 14 pages, 4 figures, style revtex. To appear in International Journal Modern Physics

Influence of Lorentz- and CPT-violating terms on the Dirac equation

The influence of Lorentz- and CPT-violating terms (in "vector" and "axial vector" couplings) on the Dirac equation is explicitly analyzed: plane wave solutions, dispersion relations and eigenenergies are explicitly obtained. The non-relativistic limit is worked out and the Lorentz-violating Hamiltonian identified in both cases, in full agreement with the results already established in the literature. Finally, the physical implications of this Hamiltonian on the spectrum of hydrogen are evaluated both in the absence and presence of a magnetic external field. It is observed that the fixed background, when considered in a vector coupling, yields no qualitative modification in the hydrogen spectrum, whereas it does provide an effective Zeeman-like splitting of the spectral lines whenever coupled in the axial vector form. It is also argued that the presence of an external fixed field does not imply new modifications on the spectrum.Comment: 13 pages, no figures, revtex4 styl

dCas9-based epigenome editing suggests acquisition of histone methylation is not sufficient for target gene repression.

Distinct epigenomic profiles of histone marks have been associated with gene expression, but questions regarding the causal relationship remain. Here we investigated the activity of a broad collection of genomically targeted epigenetic regulators that could write epigenetic marks associated with a repressed chromatin state (G9A, SUV39H1, Krüppel-associated box (KRAB), DNMT3A as well as the first targetable versions of Ezh2 and Friend of GATA-1 (FOG1)). dCas9 fusions produced target gene repression over a range of 0- to 10-fold that varied by locus and cell type. dCpf1 fusions were unable to repress gene expression. The most persistent gene repression required the action of several effector domains; however, KRAB-dCas9 did not contribute to persistence in contrast to previous reports. A 'direct tethering' strategy attaching the Ezh2 methyltransferase enzyme to dCas9, as well as a 'recruitment' strategy attaching the N-terminal 45 residues of FOG1 to dCas9 to recruit the endogenous nucleosome remodeling and deacetylase complex, were both successful in targeted deposition of H3K27me3. Surprisingly, however, repression was not correlated with deposition of either H3K9me3 or H3K27me3. Our results suggest that so-called repressive histone modifications are not sufficient for gene repression. The easily programmable dCas9 toolkit allowed precise control of epigenetic information and dissection of the relationship between the epigenome and gene regulation

The relationship between zinc intake and growth in children aged 1-8 years: a systematic review and meta-analysis

BACKGROUND/OBJECTIVES: It is estimated that zinc deficiency affects 17% of the world's population, and because of periods of rapid growth children are at an increased risk of deficiency, which may lead to stunting. This paper presents a systematic review and meta-analysis of the randomised controlled trials (RCTs) that assess zinc intake and growth in children aged 1–8 years. This review is part of a larger systematic review by the European Micronutrient Recommendations Aligned Network of Excellence that aims to harmonise the approach to setting micronutrient requirements for optimal health in European populations (www.eurreca.org). SUBJECT/METHODS: Searches were performed of literature published up to and including December 2013 using MEDLINE, Embase and the Cochrane Library databases. Included studies were RCTs in apparently healthy child populations aged from 1 to 8 years that supplied zinc supplements either as capsules or as part of a fortified meal. Pooled meta-analyses were performed when appropriate. RESULTS: Nine studies met the inclusion criteria. We found no significant effect of zinc supplementation of between 2 weeks and 12 months duration on weight gain, height for age, weight for age, length for age, weight for height (WHZ) or WHZ scores in children aged 1–8 years. CONCLUSIONS: Many of the children in the included studies were already stunted and may have been suffering from multiple micronutrient deficiencies, and therefore zinc supplementation alone may have only a limited effect on growth