Stellar black holes: cosmic history and feedback at the dawn of the universe

Significant historic cosmic evolution for the formation rate of stellar black holes is inferred from current theoretical models of the evolution of massive stars, the multiple observations of compact stellar remnants in the near and distant universe, and the cosmic chemical evolution. The mean mass of stellar black holes, the fraction of black holes/neutron stars, and the fraction of black hole high mass X-ray binaries (BH-HMXBs)/solitary black holes increase with redshift. The energetic feedback from large populations of BH-HMXBs form in the first generations of star burst galaxies has been overlooked in most cosmological models of the reionization epoch of the universe. The powerful radiation, jets, and winds from BH-HMXBs heat the intergalactic medium over large volumes of space and keep it ionized until AGN take over. It is concluded that stellar black holes constrained the properties of the faintest galaxies at high redshifts. I present here the theoretical and observational grounds for the historic cosmic evolution of stellar black holes. Detailed calculations on their cosmic impact are presented elsewhere (Mirabel, Dijkstra, Laurent, Loeb, Pritchard, 2011).Comment: 9 pages, 1 color figure. Invited talk at the IAU Symp. 275, Jets at all scales. Held in Buenos Aires on 13-17 September 2010. To be published by Cambridge University Press. Eds. G. Romero, R. Sunyaev and T. Bellon

The Coarse Geometry of Merger Trees in \Lambda CDM

We introduce the contour process to describe the geometrical properties of merger trees. The contour process produces a one-dimensional object, the contour walk, which is a translation of the merger tree. We portray the contour walk through its length and action. The length is proportional to to the number of progenitors in the tree, and the action can be interpreted as a proxy of the mean length of a branch in a merger tree. We obtain the contour walk for merger trees extracted from the public database of the Millennium Run and also for merger trees constructed with a public Monte-Carlo code which implements a Markovian algorithm. The trees correspond to halos of final masses between 10^{11} h^{-1} M_sol and 10^{14} h^{-1} M_sol. We study how the length and action of the walks evolve with the mass of the final halo. In all the cases, except for the action measured from Markovian trees, we find a transitional scale around 3 \times 10^{12} h^{-1} M_sol. As a general trend the length and action measured from the Markovian trees show a large scatter in comparison with the case of the Millennium Run trees.Comment: 7 pages, 5 figures, submitted to MNRA

Heart rate differences between symptomatic and asymptomatic Brugada syndrome patients at night

Peer ReviewedPostprint (author's final draft

A CRS oedometer cell for unsaturated and non-isothermal tests

Research into the thermo-hydro-mechanical (THM) behavior of unsaturated soils and the effect of strain rate on their mechanical responses requires employment of advanced laboratory testing systems and procedures as well as protocols of correcting the measured data in order to account for errors associated with complex test conditions and apparatus calibrations. This paper presents design and calibration of an innovative constant-rate-of-strain (CRS) oedometer cell for characterization of the THM behavior of soils under combined non-isothermal and unsaturated conditions. The advanced oedometer cell enables for simultaneous control of temperature, suction, and stress state within the soil specimens. Temperatures of 20 to 200° C is applied through a tubular heating element placed at the base of the soil specimen. Suction is controlled using axis-translation technique, and measured using both axis-translation and two high-capacity tensiometers (HCTs) accommodated on the periphery of the specimen. The performance of the new cell is assessed based on a set of tests performed on clay specimens and its merits and advantages are discussed in detail

New remarks on the Cosmological Argument

We present a formal analysis of the Cosmological Argument in its two main forms: that due to Aquinas, and the revised version of the Kalam Cosmological Argument more recently advocated by William Lane Craig. We formulate these two arguments in such a way that each conclusion follows in first-order logic from the corresponding assumptions. Our analysis shows that the conclusion which follows for Aquinas is considerably weaker than what his aims demand. With formalizations that are logically valid in hand, we reinterpret the natural language versions of the premises and conclusions in terms of concepts of causality consistent with (and used in) recent work in cosmology done by physicists. In brief: the Kalam argument commits the fallacy of equivocation in a way that seems beyond repair; two of the premises adopted by Aquinas seem dubious when the terms `cause' and `causality' are interpreted in the context of contemporary empirical science. Thus, while there are no problems with whether the conclusions follow logically from their assumptions, the Kalam argument is not viable, and the Aquinas argument does not imply a caused origination of the universe. The assumptions of the latter are at best less than obvious relative to recent work in the sciences. We conclude with mention of a new argument that makes some positive modifications to an alternative variation on Aquinas by Le Poidevin, which nonetheless seems rather weak.Comment: 12 pages, accepted for publication in International Journal for Philosophy of Religio

Model-based analysis of the autonomic response to head-up tilt testing in Brugada syndrome

The etiology of Brugada syndrome (BS) is complex and multifactorial, making risk stratification in this population a major challenge. Since changes in the autonomic modulation of these patients are commonly related to arrhythmic events, we analyze in this work whether the response to head-up tilt (HUT) testing on this population may provide useful, complementary information for risk stratification. In order to perform this analysis, a coupled physiological model integrating the cardiac electrical activity, the cardiovascular system and the baroreceptors reflex control of the autonomic function, in response to HUT is proposed. A sensitivity analysis was performed, based on a screening method, evidencing the influence of cardiovascular parameters on blood pressure and of baroreflex regulation on heart rate. The most sensitive parameters have been identified on a set of 20 subjects (8 controls and 12 BS patients), so as to assess subject-specific model parameters. According to the results, controls showed an increased sympathetic modulation after tilting, as well as a reduced left ventricular contractility was observed in symptomatic, with respect to asymptomatic BS patients. These results provide new insights regarding the autonomic mechanisms regulating the cardiovascular system in BS which might be used as a complementary source of information, along with classical electrophysiological parameters, for BS risk stratification.Peer ReviewedPostprint (author's final draft

234Th-derived particle fluxes and seasonal variability: when is the ss assumption reliable? Insights from a novel Approach for carbon flux simulation

Th measurements are widely used to estimate the downward carbon flux of particles via the oceanic Biological Pump. Carbon export is evaluated from 234Th-238U disequilibrium assuming either steady state (SS) conditions, or including a non-SS (NSS) correction. We use a novel stochastic simulation to quantify the temporal variation of vertical carbon and 234Th (dissolved and particulate) concentration profiles with high temporal resolution. We calculate seasonal export as if in situ measured with sediment trap and SS- and NSS-234ThapproachesandquantifytheperiodsofvalidityforSS/NSSconditionsdefinedinpreviousworks.The SS approach is valid throughout the entire season in oligotrophic regions. In temperate regions, the SS introduces a bias in the export if sampling takes place outside specific temporal windows. Windows of validity range from days in short blooms of ~15-day duration to weeks in blooms longer than ~30 days

Evaluación del triángulo cefalométrico de tweed en pacientes peruanos con biotipo facial armónico

RESUMENEl triángulo cefalométrico de Tweed es bastante utilizado en la planificación de un tratamiento de ortodoncia, y ha sido reconocido como una de las claves para el diagnóstico, siendo muy importante para conocer el desarrollo de la maloclusión y el patrón facial.OBJETIVO: Evaluar el triángulo cefalométrico de Tweed en pacientes peruanos con biotipo facial armónico, de Clase I esquelética por medio de radiografías laterales de cabeza.MATERIALES Y MÉTODOS: La muestra estuvo conformada por 112 cefalogramas de adultos de 18 a 40 años de edad, (83 mujeres y 29 varones) que cumplieron los criterios de selección del archivo de un Centro de Diagnóstico por Imágenes. Se analizaron las radiografías de forma digitalizada y en ellas se evaluó el triángulo de Tweed a través de las mediciones de los ángulos IMPA, FMA y FMIA. También se evaluó la relación esquelética según Arnett, Steiner y Proyección USP para seleccionar los casos armónicos. Las pruebas de T de Student, ANCOVA y Regresión Lineal Múltiple fueron empleadas.RESULTADOS: Los valores cefalométricos del triángulo de Tweed fueron (FMA= 27.26°, FMIA= 60.05° e IMPA= 92.77°) y muestran diferencias significativas con los valores de la norma caucásica (p<0.001). En el análisis multivariante se observa que el ángulo IMPA, está modificado significativamente por las variaciones en el ángulo FMA y FMIA, y el modelo de regresión demuestra que este ángulo puede ser altamente predecible por estas variables.CONCLUSIÓN: Los valores cefalométricos del triángulo de Tweed difieren al de las normas caucásicas estando el ángulo IMPA más vestibularizado y los ángulos FMA y FMIA son los mejores predictores para el ángulo IMPA