Semiparametric Cross Entropy for rare-event simulation

The Cross Entropy method is a well-known adaptive importance sampling method for rare-event probability estimation, which requires estimating an optimal importance sampling density within a parametric class. In this article we estimate an optimal importance sampling density within a wider semiparametric class of distributions. We show that this semiparametric version of the Cross Entropy method frequently yields efficient estimators. We illustrate the excellent practical performance of the method with numerical experiments and show that for the problems we consider it typically outperforms alternative schemes by orders of magnitude

Thermal Entanglement of a Spin-1/2 Ising-Heisenberg Model on a Symmetrical Diamond Chain

The entanglement quantum properties of a spin-1/2 Ising-Heisenberg model on a symmetrical diamond chain were analyzed. Due to the separable nature of the Ising-type exchange interactions between neighboring Heisenberg dimers, calculation of the entanglement can be performed exactly for each individual dimer. Pairwise thermal entanglement was studied in terms of the isotropic Ising-Heisenberg model, and analytical expressions for the concurrence (as a measure of bipartite entanglement) were obtained. The effects of external magnetic field $H$ and next-nearest neighbor interaction $J_m$ between nodal Ising sites were considered. The ground-state structure and entanglement properties of the system were studied in a wide range of the coupling constant values. Various regimes with different values of the ground-state entanglement were revealed, depending on the relation between competing interaction strengths. Finally, some novel effects, such as the two-peak behavior of concurrence versus temperature and coexistence of phases with different values of magnetic entanglement were observed

Transverse Takahashi Identities and Their Implications for Gauge Independent Dynamical Chiral Symmetry Breaking

In this article, we employ transverse Takahashi identities to impose valuable non-perturbative constraints on the transverse part of the fermion-photon vertex in terms of new form factors, the so called $Y_i$ functions. We show that the implementation of these identities is crucial in ensuring the correct local gauge transformation of the fermion propagator and its multiplicative renormalizability. Our construction incorporates the correct symmetry properties of the $Y_i$ under charge conjugation operation as well as their well-known one-loop expansion in the asymptotic configuration of incoming and outgoing momenta. Furthermore, we make an explicit analysis of various existing constructions of this vertex against the demands of transverse Takahashi identities and the previously established key features of quantum electrodynamics, such as gauge invariance of the critical coupling above which chiral symmetry is dynamically broken. We construct a simple example in its quenched version and compute the mass function as we vary the coupling strength and also calculate the corresponding anomalous dimensions $\gamma_m$. There is an excellent fit to the Miransky scalling law and we find $\gamma_m=1$ rather naturally in accordance with some earlier results in literature, using arguments based on Cornwall-Jackiw-Tomboulis effective potential technique. Moreover, we numerically confirm the gauge invariance of this critical coupling.Comment: 16 pages, 4 figure

Management of Urinary Tract Infection in Pregnancy

Urinary tract infection is a frequent occurrence in pregnancy that can increase the risk of complications; therefore, it is essential to investigate it at the first prenatal consultation. It is classified as asymptomatic bacteriuria, cystitis, and pyelonephritis. This research aims to determine the most appropriate treatment for urinary tract infections during pregnancy according to the best available evidence. The methodology implemented a clinical question: What is the best treatment for urinary tract infections during pregnancy? The PICO format helped search for scientific information, such as the pregnant women’s population with urinary tract infections, whether the intervention received was an antibiotic treatment, was the comparison a no antibiotic treatment, and the result of preventing complications during pregnancy. The databases consulted were PubMed, Cochrane Library, the ACCESSSS search engine, Epistemonikos, DynaMed, and UpToDate. As a result of the information search process, 305 articles were obtained, of which 255 were discarded for not being within the inclusion criteria and 51 were used in this investigation. Of these 50 articles, 15 were eliminated because they were duplicates and 37 were used in this review. In conclusion, urinary tract infection causes increased perinatal maternal morbidity and mortality; therefore, it is essential to investigate and treat it. Keywords: urinary tract infections, pregnancy, drug therapy. Resumen La infección del trato urinario es una afectación frecuente en el embarazo que puede aumentar el riego de complicaciones, por lo tanto, es fundamental investigarla desde la primera consulta prenatal, se clasifica en bacteriuria asintomática, cistitis y pielonefritis. El objetivo de esta investigación es determinar el tratamiento más adecuado para los cuadros de infección del tracto urinario durante el embarazo de acuerdo a la mejor evidencia disponible. En la metodología se implementó como pregunta clínica ¿cuál es el mejor tratamiento para la infección del tracto urinario durante el embarazo? bajo el formato PICO que ayudó en la búsqueda de información científica, la población son las mujeres gestantes con infección del tracto urinario, la intervención es el tratamiento antibiótico recibido, la comparación fue el no tratamiento antibiótico y el resultado la prevención de complicaciones durante el embarazo. Las bases de datos consultadas fueron PubMed, Cochrane Library, el buscador ACCESSSS, Epistemonikos, DynaMed y UpToDate. En el resultado del proceso de búsqueda de la información se obtuvo 305 artículos de los cuales se descartaron 255 por no estar dentro de los criterios de inclusión y se utilizaron 51 artículos que se servirán en esta investigación; de estos 50 se eliminan 15 artículos por estar duplicados y finalmente 37 artículos se utilizarán para la elaboración de esta revisión. Como principales conclusiones tenemos que la infección del tracto urinario causa aumento de la morbimortalidad materno perinatal, por lo tanto, es fundamental investigarla y tratarla. Palabras Clave: infecciones urinarias, embarazo, quimioterapia

MegaMorph: classifying galaxy morphology using multi-wavelength S\'ersic profile fits

Aims. This work investigates the potential of using the wavelength-dependence of galaxy structural parameters (S\'ersic index, n, and effective radius, Re) to separate galaxies into distinct types. Methods. A sample of nearby galaxies with reliable visual morphologies is considered, for which we measure structural parameters by fitting multi-wavelength single-S\'ersic models. Additionally, we use a set of artificially redshifted galaxies to test how these classifiers behave when the signal-to-noise decreases. Results. We show that the wavelength-dependence of n may be employed to separate visually-classified early- and late-type galaxies, in a manner similar to the use of colour and n. Furthermore, we find that the wavelength variation of n can recover galaxies that are misclassified by these other morphological proxies. Roughly half of the spiral galaxies that contaminate an early-type sample selected using (u-r) versus n can be correctly identified as late-types by N, the ratio of n measured in two different bands. Using a set of artificially-redshifted images, we show that this technique remains effective up to z ~ 0.1. N can therefore be used to achieve purer samples of early-types and more complete samples of late-types than using a colour-n cut alone. We also study the suitability of R, the ratio of Re in two different bands, as a morphological classifier, but find that the average sizes of both early- and late-type galaxies do not change substantially over optical wavelengths.Comment: 6 pages, 2 figures, 2 tables, Accepted for publication in A&