Cosmological simulations using a static scalar-tensor theory

We present $\Lambda$CDM $N$-body cosmological simulations in the framework of a static general scalar-tensor theory of gravity. Due to the influence of the non-minimally coupled scalar field, the gravitational potential is modified by a Yukawa type term, yielding a new structure formation dynamics. We present some preliminary results and, in particular, we compute the density and velocity profiles of the most massive group.Comment: 4 pages, 6 figures, to appear in Journal of Physics: Conference Series: VII Mexican School on Gravitation and Mathematical Physics. 26 November to 1 December 2006, Playa del Carmen, Quintana Roo, Mexic

Evidence for Blue Straggler Stars Rejuvenating the Integrated Spectra of Globular Clusters

Integrated spectroscopy is the method of choice for deriving the ages of unresolved stellar systems. However, hot stellar evolutionary stages, such as hot horizontal branch stars and blue straggler stars (BSSs), can affect the integrated ages measured using Balmer lines. Such hot, "non-canonical" stars may lead to overestimations of the temperature of the main sequence turn-off, and therefore underestimations of the integrated age of a stellar population. Using an optimized Hbeta index in conjunction with HST/WFPC2 color-magnitude diagrams (CMDs), we show that Galactic globular clusters exhibit a large scatter in their apparent "spectroscopic" ages, which does not correspond to that in their CMD-derived ages. We find for the first time that the specific frequency of BSSs, defined within the same aperture as the integrated spectra, shows a clear correspondence with Hbeta in the sense that, at fixed metallicity, higher BSS ratios lead to younger "apparent" spectroscopic ages. Thus, the specific frequency of BSSs in globular clusters sets a fundamental limit on the accuracy for which spectroscopic ages can be determined for globular clusters, and maybe for other stellar systems like galaxies. The observational implications of this result are discussed.Comment: 5 pages, 2 figures, 1 table. Accepted for publication in ApJ

How much dark matter is there inside early-type galaxies?

We study the luminous mass as a function of the dynamical mass inside the effective radius (r_e) of early-type galaxies (ETGs) to search for differences between these masses. We assume Newtonian dynamics and that any difference between these masses is due to the presence of dark matter. We use several samples of ETGs -ranging from 19 000 to 98 000 objects- from the ninth data release of the Sloan Digital Sky Survey. We perform Monte Carlo (MC) simulations of galaxy samples and compare them with real samples. The main results are: i) MC simulations show that the distribution of the dynamical vs. luminous mass depends on the mass range where the ETGs are distributed (geometric effect). This dependence is caused by selection effects and intrinsic properties of the ETGs. ii) The amount of dark matter inside r_e is approximately 7% +- 22%. iii) This amount of dark matter is lower than the minimum estimate (10%) found in the literature and four times lower than the average (30%) of literature estimates. However, if we consider the associated error, our estimate is of the order of the literature average.Comment: 24 pages, 12 figures. MNRAS accepte

On Some Geometric Properties of Slice Regular Functions of a Quaternion Variable

The goal of this paper is to introduce and study some geometric properties of slice regular functions of quaternion variable like univalence, subordination, starlikeness, convexity and spirallikeness in the unit ball. We prove a number of results, among which an Area-type Theorem, Rogosinski inequality, and a Bieberbach-de Branges Theorem for a subclass of slice regular functions. We also discuss some geometric and algebraic interpretations of our results in terms of maps from $\mathbb R^4$ to itself. As a tool for subordination we define a suitable notion of composition of slice regular functions which is of independent interest

Scalability of the Muscular Action in a Parametric 3D Model of the Index Finger

A method for scaling the muscle action is proposed and used to achieve a 3D inverse dynamic model of the human finger with all its components scalable. This method is based on scaling the PCSA (physiological cross-sectional area) in a Hill muscle model. Different anthropometric parameters and maximal grip force data have been measured and their correlations have been analysed and used for scaling the PCSA of each muscle. A linear relationship between the normalised PCSA and the product of the length and breadth of the hand has been finally used for scaling, with a slope of 0.01315 cm-2, with the length and breadth of the hand expressed in centimetres. The parametric muscle model has been included in a parametric finger model previously developed by the authors, and it has been validated reproducing the results of an experiment in which subjects from different population groups exerted maximal voluntary forces with their index finger in a controlled postur

Relationship between Serum Concentration of Uric Acid and Insulin Secretion among Adults with Type 2 Diabetes Mellitus

To determine the relationship between serum concentrations of uric acid and insulin secretion with hyperglycaemic clamp technique among adults with type 2 diabetes mellitus (DM2) without hyperuricemia, we carried out a cross-sectional study on 45 patients of both gender. We observed correlation between uric acid with male gender r = 0.710 (P = 0.001). Also correlation between uric acid and total insulin secretion was positive r = 0.295 (P = 0.049). As well as a positive correlation adjusted for body mass index was demonstrated for the first, second, and total phases of insulin secretion, respectively, r = 0.438 (P = 0.022), r = 0.433 (P = 0.022), and r = 0.439 (P = 0.024). Serum concentration of uric acid showed a positive relationship with the total phase of insulin secretion; even in states prior to hyperuricemia, uric acid can play an important role in the function of the beta cell in patients with DM2

La autoestima como variable protectora del burnout en estudiantes de fisioterapia

En los últimos años existe un creciente interés por determinar los factores que inciden en el origen y el mantenimiento del burnout académico. En este contexto, en el presente trabajo se analiza la posible existencia de diferencias signifi cativas en el burnout experimentado por los estudiantes universitarios en función de su nivel de autoestima. La muestra está compuesta por 487 estudiantes de Fisioterapia de diversas universidades españolas, 354 mujeres (72.68%) y 133 varones (27.32%), con edades comprendidas entre los 18 y los 47 años (M = 21.28 y DT = 4.32). Para medir la autoestima, se utilizó la Escala de Autoestima de Rosenberg; para evaluar el burnout, se usó el Maslach Burnout Inventory (MBI). Como procedimiento de análisis de datos, se efectuó un ANOVA de un factor, así como la d de Cohen. Los resultados de este trabajo ponen de manifi esto que, cuando los estudiantes tienen una baja autoestima, aparecen manifestaciones más claras de burnout. En cambio, cuanto mayor es la valoración que hacen de sí mismos, menores síntomas de agotamiento y despersonalización y mayores niveles de realización personal manifi estan los estudiantes. Dado el rol protector de la autoestima sobre el burnout, se incide en la importancia de potenciar la autoestima de los estudiantes como estrategia para prevenir la aparición del síndrome.What variables are implicated in burnout appearance and maintenance among university students is one of the facts that has raised lately a greater attention in burnout investigation. In this context, our work assesses if students’ self-esteem level causes meaningful differences in students’ burnout. The sample comprised a total of 487 students selected among different Spanish universities of Physiotherapy, 354 women (72.68%) and 133 men (27.32%), aged between 18 and 47 years old (M = 21.28; SD = 4.32). We measure self-esteem by using Rosenberg’s Self- Esteem Scale. Burnout was evaluated by using Maslach Burnout Inventory (MBI). One-way ANOVA was calculated in order to estimate statistical differences in students’ burnout according to their level of self-esteem. Furthermore, Cohen’s d was used in order to establish the effect sizes of those differences. Our results show that burnout syndrome appears when students’ self-esteem is low. Nevertheless, higher levels of selfesteem show lower levels of emotionally exhaustion and despersonalization, and higher levels of personal accomplishment. In view that self-esteem works as a protector factor of burnout, we highlight that enhancing students’ self esteem is one of the better ways to prevent this syndrome