Predicting Pregnancy Outcomes Using Longitudinal Information: A Penalized Splines Mixed–Effects Model Approach

We propose a semiparametric mixed–effects model (SNMM) using penalized splines to clas- sify longitudinal data and improve the prediction of a binary outcome. The work is motivated by a study in which different hormone levels were measured during the early stages of preg- nancy, and the challenge is using this information to predict normal versus abnormal pregnancy outcomes. The aim of this paper is to compare models and estimation strategies based on alternative formulations of SNMMs depending on the characteristics of the data set under con- sideration. For our motivating example, we address the classification problem using a particular case of the SNMM in which the parameter space has a finite dimensional component (fixed effects and variance components) and an infinite dimensional component (unknown function) that need to be estimated. The nonparametric component of the model is estimated using pe- nalized splines. For the parametric component, we compare the advantages of using random effects versus direct modeling of the correlation structure of the errors. Numerical studies show that our approach improves over other existing methods for the analysis of this type of data. Furthermore, the results obtained using our method support the idea that explicit modeling of the serial correlation of the error term improves the prediction accuracy with respect to a model with random effects, but independent errors.MTM2014-52184-

Multi-filter transit observations of WASP-39b and WASP-43b with three San Pedro M\'artir telescopes

Three optical telescopes located at the San Pedro M\'artir National Observatory were used for the first time to obtain multi-filter defocused photometry of the transiting extrasolar planets WASP-39b and WASP-43b. We observed WASP-39b with the 2.12m telescope in the U filter for the first time, and additional observations were carried out in the R and I filters using the 0.84m telescope. WASP-43b was observed in VRI with the same instrument, and in the i filter with the robotic 1.50m telescope. We reduced the data using different pipelines and performed aperture photometry with the help of custom routines, in order to obtain the light curves. The fit of the light curves (1.5--2.5mmag rms), and of the period analysis, allowed a revision of the orbital and physical parameters, revealing for WASP-39b a period ($4.0552947 \pm 9.65 \times 10^{-7}$ days) which is $3.084 \pm 0.774$ seconds larger than previously reported. Moreover, we find for WASP-43b a planet/star radius ($0.1738 \pm 0.0033$) which is $0.01637 \pm 0.00371$ larger in the i filter with respect to previous works, and that should be confirmed with additional observations. Finally, we confirm no evidence of constant period variations in WASP-43b.Comment: 13 pages, 7 figures, accepted in PASP, scheduled for the February 1, 2015 issu

Stellar population gradients from cosmological simulations: dependence on mass and environment in local galaxies

The age and metallicity gradients for a sample of group and cluster galaxies from N-body+hydrodynamical simulation are analysed in terms of galaxy stellar mass. Dwarf galaxies show null age gradient with a tail of high and positive values for systems in groups and cluster outskirts. Massive systems have generally zero-age gradients which turn to positive for the most massive ones. Metallicity gradients are distributed around zero in dwarf galaxies and become more negative with mass; massive galaxies have steeper negative metallicity gradients, but the trend flattens with mass. In particular, fossil groups are characterized by a tighter distribution of both age and metallicity gradients. We find a good agreement with both local observations and independent simulations. Interestingly, our results suggest that environment differently affects the gradients at low and high masses. The results are also discussed in terms of the central age and metallicity, as well as the total colour, specific star formation and velocity dispersio

A solution for galactic disks with Yukawian gravitational potential

We present a new solution for the rotation curves of galactic disks with gravitational potential of the Yukawa type. We follow the technique employed by Toomre in 1963 in the study of galactic disks in the Newtonian theory. This new solution allows an easy comparison between the Newtonian solution and the Yukawian one. Therefore, constraints on the parameters of theories of gravitation can be imposed, which in the weak field limit reduce to Yukawian potentials. We then apply our formulae to the study of rotation curves for a zero-thickness exponential disk and compare it with the Newtonian case studied by Freeman in 1970. As an application of the mathematical tool developed here, we show that in any theory of gravity with a massive graviton (this means a gravitational potential of the Yukawa type), a strong limit can be imposed on the mass (m_g) of this particle. For example, in order to obtain a galactic disk with a scale length of b ~ 10 kpc, we should have a massive graviton of m_g << 10^{-59} g. This result is much more restrictive than those inferred from solar system observations.Comment: 7 pages; 1 eps figure; to appear in General Relativity and Gravitatio

Fermion localization on branes with generalized dynamics

In this letter we consider a specific model of braneworld with nonstandard dynamics diffused in the literature, specifically we focus our attention on the matter energy density, the energy of system, the Ricci scalar and the thin brane limit. As the model is classically stable and capable of localize gravity, as a natural extension we address the issue of fermion localization of fermions on a thick brane constructed out from one scalar field with nonstandard kinetic terms coupled with gravity. The contribution of the nonstandard kinetic terms in the problem of fermion localization is analyzed. It is found that the simplest Yukawa coupling $\eta\bar{\Psi}\phi\Psi$ support the localization of fermions on the thick brane. It is shown that the zero mode for left-handed can be localized on the thick brane depending on the values for the coupling constant $\eta$.Comment: 6 pages, 3 figure

Ischaemic Stroke in the Time of Coronavirus Disease 2019

Each year, between 1.1 and 1.5 million Europeans have a stroke1. Two to three out of 10 patients die as a consequence of it and about one third remains functionally dependent2. As we know, the likelihood of a favourable outcome in this disease relies heavily on patients presenting promptly after symptoms onset and on hospitals providing immediate access to optimized stroke care

Technical evaluation of resistance to compression in concretes made with CPCA cement

In recent years Venezuela has presented a crisis on the demand, commercialization and production of cement, the material needed for construction, therefor additive cements are being used without any type of regulations. This work presents the physical-mechanical characterization of three concrete mixtures with water / cement ratio of 0.45 and water / cement ratio of 0.60 with different types of Portland cement, Type I, Type CPCA1,and the third mixture corresponds to Type CPCA1 Rewarding it with a 15% addition in his own weight, developing a mixture of better quality. These concretes were characterized by: settling, setting time, percentage of total porosity, percentage of water absorption and mechanical resistance to compression. The results showed that the concrete mixture produced with CPCA1 does not meet the minimum requirements established in the Venezuelan standard for use in the elaboration of structural concrete, because among other parameters its resistance to compression it&#39;s below the design value. As for the CPCA1 giving it 15% addition in its own weight meets the requirements, and can be used in the manufacture of concrete structural elements