The trans-activation domain of the sporulation response regulator Spo0A revealed by X-ray crystallography

Sporulation in Bacillus involves the induction of scores of genes in a temporally and spatially co-ordinated programme of cell development. Its initiation is under the control of an expanded two-component signal transduction system termed a phosphorelay. The master control element in the decision to sporulate is the response regulator, Spo0A, which comprises a receiver or phosphoacceptor domain and an effector or transcription activation domain. The receiver domain of Spo0A shares sequence similarity with numerous response regulators, and its structure has been determined in phosphorylated and unphosphorylated forms. However, the effector domain (C-Spo0A) has no detectable sequence similarity to any other protein, and this lack of structural information is an obstacle to understanding how DNA binding and transcription activation are controlled by phosphorylation in Spo0A. Here, we report the crystal structure of C-Spo0A from Bacillus stearothermophilus revealing a single alpha -helical domain comprising six alpha -helices in an unprecedented fold. The structure contains a helix-turn-helix as part of a three alpha -helical bundle reminiscent of the catabolite gene activator protein (CAP), suggesting a mechanism for DNA binding. The residues implicated in forming the sigma (A)-activating region clearly cluster in a flexible segment of the polypeptide on the opposite side of the structure from that predicted to interact with DNA. The structural results are discussed in the context of the rich array of existing mutational data

Controlled-NOT logic gate for phase qubits based on conditional spectroscopy

A controlled-NOT logic gate based on conditional spectroscopy has been demonstrated recently for a pair of superconducting flux qubits [Plantenberg et al., Nature 447, 836 (2007)]. Here we study the fidelity of this type of gate applied to a phase qubit coupled to a resonator (or a pair of capacitively coupled phase qubits). Our results show that an intrinsic fidelity of more than 99% is achievable in 45ns.Comment: 5 pages, 5 figures, To appear in Quantum Inf. Pro

Ab initio study of the beta$-tin->Imma->sh phase transitions in silicon and germanium

We have investigated the structural sequence of the high-pressure phases of silicon and germanium. We have focussed on the cd->beta-tin->Imma->sh phase transitions. We have used the plane-wave pseudopotential approach to the density-functional theory implemented within the Vienna ab-initio simulation package (VASP). We have determined the equilibrium properties of each structure and the values of the critical parameters including a hysteresis effect at the phase transitions. The order of the phase transitions has been obtained alternatively from the pressure dependence of the enthalpy and of the internal structure parameters. The commonly used tangent construction is shown to be very unreliable. Our calculations identify a first-order phase transition from the cd to the beta-tin and from the Imma to the sh phase, and they indicate the possibility of a second-order phase-transition from the beta-tin to the Imma phase. Finally, we have derived the enthalpy barriers between the phases.Comment: 12 pages, 16 figure

Estrategias de ahorro de sangre en Artroplastia Total de Rodilla Primaria aplicadas en nuestra Comunidad

Antecedentes. El objetivo del presente estudio fue realizar una actualización sobre las diferentes estrategias en el ahorro de sangre en cirugía protésica de rodilla pri-maria, a través de una revisión bibliográfica; así como, conocer qué estrategias se siguen en diferentes centros hospitalarios de nuestro ámbito, mediante un estudio multicéntrico. Métodos. Se realizó un estudio observacional transversal descriptivo basado en una encuesta realizada a 64 cirujanos y una búsqueda bibliográfica sobre los distintos aspectos incluidos en la encuesta. Resultados. Los cirujanos refieren que cuentan con protocolos de ahorro sanguíneo prequirúrgicos implantados en su Hospital en un 48,4% (31/64). La utilización del ácido tranexámico es bastante generalizada 71,9% de los encuestados (46/64). Este se administra vía endovenosa previa a la cirugía en un 26,6% (17/64) de los casos, de manera intraarticular en un 21,9% (14/64) y en una combinación de ambas en un 23,4% (15/64). El momento preferido para la colocación de la isquemia por los cirujanos es en un 57,8% (37/64) previo a pintar el campo, mientras que un 39,1% (25/64) prefiere colocarla en estéril. Un 3,1% (2/64) de cirujanos afirma implantar las prótesis sin utilizar isquemia en la cirugía. Conclusiones. En los últimos años se está imponiendo la utilización de ATX como principal estrategia de ahorro de sangre en ATR, aunque no existe consenso en cuanto a la dosis óptima ni a su vía de administración. La eficacia del ATX está influyendo en la eliminación de los drenajes postquirúrgicos y en la implementación de programas de rehabilitación preco

Medidas de Tromboprofilaxis en Artroplastia Total de Rodilla. Práctica habitual en la Comunidad Valenciana y revisión bibliográfica.

Antecedentes: El tromboembolismo es una complicación de la cirugía de artroplastia total de rodilla. Para su prevención disponemos de múltiples medidas físicas y farmacológicas.Objetivo:Conocer quémedidas de prevención tromboembólica son las empleadas por los cirujanos ortopédicos en cirugía protésica de rodilla primaria en diferentes centros hospitalarios de nuestra región.Método: Estudio transversal descriptivo observacional basado en encuesta dirigida a especialistas COT de 9 hospitales públicos de la Comunidad Valenciana y búsqueda bibliográfica.Resultados: Se obtuvieron 64 encuestas. Todos los cirujanos eligen HBPM durante un mes como medida de tromboprofilaxis, descartando anticoagulantes orales o aspirina. El 29% también emplea dispositivos de movilización pasiva. Conclusiones: Los cirujanos ortopédicos de la comunidad valenciana optan por HBPM conforme a las mejores evidencias. Se estima, que la incidencia de eventos tromboembólicos sintomáticos desciende del 4,3 % al 1,8% con el uso de HBPM. El empleo de dispositivos de movilización pasiva y medias de compresión no están avaladas por las evidencias. La estratificación preoperatoria del riesgo de tromboembolismo, para emplear ácido acetil salicílico asociado a bombas de presión intermitente en caso de no existir alto riesgo es una tendencia cada vez más aceptada internacionalmente

Medidas para la prevención de la infección en la artroplastia de rodilla : prácticas habituales y evidencias

Infection after knee arthroplasty is one of the most feared complications and routine measures are applied to prevent it. The objective of this study is to identify which are the measures applied by the surgeons of the Valencian Community (CV) and know if the scientific evidence supports them or not. Methods. A descriptive cross-sectional observational study based on a survey of 64 surgeons and bibliographic searches on the aspects included in the survey were conducted. Results. 18.8% of the surgeons perform screening for SARM carriers and decolonization. 98.4% use cefazoline and 1.6% cefuroxime as antibiotic prophylaxis. With respect to the duration of antibiotic prophylaxis, 51% of surgeons administer three doses (24 hours prophylaxis), 23.4% use 2 doses and 17.2% of them use only one dose. 67.2% use 2% alcoholic chlorhexidine gluconate solution for surgical site preparation and 71.9% use adhesive incision drapes. Routine cement with antibiotics is used by 65.6% of respondents. The current scientific evidence supports antibiotic prophylaxis as performed by 100% of respondents; however there is no evidence for the superiority of the preparation of the skin with alcoholic chlorhexidine versus other antiseptics. There is also no evidence to support the use of adhesive incision drapes or the use of cement with antibiotics in a routine manner. Conclusions. It would be advisable for the CV surgeons to avoid the use of incision adhesive drapes and the application of cement with antibiotics in all cases. The preparation of the skin with alcoholic chlorhexidine does not seem to be more effective than other antiseptics in orthopaedic surgery. The screening of SAMR carriers and their decolonization seems to reduce the infection rate; its use can be recommended today, but studies with the largest number of patients that confirm their benefit are needed

Quantum walks: a comprehensive review

Quantum walks, the quantum mechanical counterpart of classical random walks, is an advanced tool for building quantum algorithms that has been recently shown to constitute a universal model of quantum computation. Quantum walks is now a solid field of research of quantum computation full of exciting open problems for physicists, computer scientists, mathematicians and engineers. In this paper we review theoretical advances on the foundations of both discrete- and continuous-time quantum walks, together with the role that randomness plays in quantum walks, the connections between the mathematical models of coined discrete quantum walks and continuous quantum walks, the quantumness of quantum walks, a summary of papers published on discrete quantum walks and entanglement as well as a succinct review of experimental proposals and realizations of discrete-time quantum walks. Furthermore, we have reviewed several algorithms based on both discrete- and continuous-time quantum walks as well as a most important result: the computational universality of both continuous- and discrete- time quantum walks.Comment: Paper accepted for publication in Quantum Information Processing Journa

1000 Genomes-based meta-analysis identifies 10 novel loci for kidney function.

HapMap imputed genome-wide association studies (GWAS) have revealed >50 loci at which common variants with minor allele frequency >5% are associated with kidney function. GWAS using more complete reference sets for imputation, such as those from The 1000 Genomes project, promise to identify novel loci that have been missed by previous efforts. To investigate the value of such a more complete variant catalog, we conducted a GWAS meta-analysis of kidney function based on the estimated glomerular filtration rate (eGFR) in 110,517 European ancestry participants using 1000 Genomes imputed data. We identified 10 novel loci with p-value < 5 × 10(-8) previously missed by HapMap-based GWAS. Six of these loci (HOXD8, ARL15, PIK3R1, EYA4, ASTN2, and EPB41L3) are tagged by common SNPs unique to the 1000 Genomes reference panel. Using pathway analysis, we identified 39 significant (FDR < 0.05) genes and 127 significantly (FDR < 0.05) enriched gene sets, which were missed by our previous analyses. Among those, the 10 identified novel genes are part of pathways of kidney development, carbohydrate metabolism, cardiac septum development and glucose metabolism. These results highlight the utility of re-imputing from denser reference panels, until whole-genome sequencing becomes feasible in large samples

Serum magnesium and calcium levels in relation to ischemic stroke : Mendelian randomization study

ObjectiveTo determine whether serum magnesium and calcium concentrations are causally associated with ischemic stroke or any of its subtypes using the mendelian randomization approach.MethodsAnalyses were conducted using summary statistics data for 13 single-nucleotide polymorphisms robustly associated with serum magnesium (n = 6) or serum calcium (n = 7) concentrations. The corresponding data for ischemic stroke were obtained from the MEGASTROKE consortium (34,217 cases and 404,630 noncases).ResultsIn standard mendelian randomization analysis, the odds ratios for each 0.1 mmol/L (about 1 SD) increase in genetically predicted serum magnesium concentrations were 0.78 (95% confidence interval [CI] 0.69-0.89; p = 1.3 7 10-4) for all ischemic stroke, 0.63 (95% CI 0.50-0.80; p = 1.6 7 10-4) for cardioembolic stroke, and 0.60 (95% CI 0.44-0.82; p = 0.001) for large artery stroke; there was no association with small vessel stroke (odds ratio 0.90, 95% CI 0.67-1.20; p = 0.46). Only the association with cardioembolic stroke was robust in sensitivity analyses. There was no association of genetically predicted serum calcium concentrations with all ischemic stroke (per 0.5 mg/dL [about 1 SD] increase in serum calcium: odds ratio 1.03, 95% CI 0.88-1.21) or with any subtype.ConclusionsThis study found that genetically higher serum magnesium concentrations are associated with a reduced risk of cardioembolic stroke but found no significant association of genetically higher serum calcium concentrations with any ischemic stroke subtype

Galaxy Clusters Associated with Short GRBs. II. Predictions for the Rate of Short GRBs in Field and Cluster Early-Type Galaxies

We determine the relative rates of short GRBs in cluster and field early-type galaxies as a function of the age probability distribution of their progenitors, P(\tau) \propto \tau^n. This analysis takes advantage of the difference in the growth of stellar mass in clusters and in the field, which arises from the combined effects of the galaxy stellar mass function, the early-type fraction, and the dependence of star formation history on mass and environment. This approach complements the use of the early- to late-type host galaxy ratio, with the added benefit that the star formation histories of early-type galaxies are simpler than those of late-type galaxies, and any systematic differences between progenitors in early- and late-type galaxies are removed. We find that the ratio varies from R(cluster)/R(field) ~ 0.5 for n = -2 to ~ 3 for n = 2. Current observations indicate a ratio of about 2, corresponding to n ~ 0 - 1. This is similar to the value inferred from the ratio of short GRBs in early- and late-type hosts, but it differs from the value of n ~ -1 for NS binaries in the Milky Way. We stress that this general approach can be easily modified with improved knowledge of the effects of environment and mass on the build-up of stellar mass, as well as the effect of globular clusters on the short GRB rate. It can also be used to assess the age distribution of Type Ia supernova progenitors.Comment: ApJ accepted versio