Relative frequencies of constrained events in stochastic processes: An analytical approach

The stochastic simulation algorithm (SSA) and the corresponding Monte Carlo (MC) method are among the most common approaches for studying stochastic processes. They rely on knowledge of interevent probability density functions (PDFs) and on information about dependencies between all possible events. Analytical representations of a PDF are difficult to specify in advance, in many real life applications. Knowing the shapes of PDFs, and using experimental data, different optimization schemes can be applied in order to evaluate probability density functions and, therefore, the properties of the studied system. Such methods, however, are computationally demanding, and often not feasible. We show that, in the case where experimentally accessed properties are directly related to the frequencies of events involved, it may be possible to replace the heavy Monte Carlo core of optimization schemes with an analytical solution. Such a replacement not only provides a more accurate estimation of the properties of the process, but also reduces the simulation time by a factor of order of the sample size (at least $\approx 10^4$). The proposed analytical approach is valid for any choice of PDF. The accuracy, computational efficiency, and advantages of the method over MC procedures are demonstrated in the exactly solvable case and in the evaluation of branching fractions in controlled radical polymerization (CRP) of acrylic monomers. This polymerization can be modeled by a constrained stochastic process. Constrained systems are quite common, and this makes the method useful for various applications

Recent developments in miniemulsion polymerization

Some developments in miniemulsion polymerization aiming at taking advantage of its unique mechanisms minimizing the drawbacks of this technique are discussed. The discussion ineludes preparation of highly concentrated latexes, miniemulsion polymerization in continuous stirred tank reactors (CSTRs), and elimination of the low molecular weight hydrophobe

Sobre proyectos de espacios públicos de calidad: estrategias urbanas comparadas

La ciudad compacta, policéntrica y con espacios públicos de calidad constituye un modelo urbano implícito en los Objetivos de Desarrollo Sostenible (ODS). La Nueva Agenda Urbana promueve la calidad del espacio público como bien común, y por ello es pertinente reconsiderar los parámetros de calidad e investigar su potencial de desarrollo. Este artículo se fundamenta en una reflexión teórica y metodológica sobre la calidad de los espacios públicos, teniendo en cuenta las aportaciones de la tradición urbanística. Con esta perspectiva se han analizado una selección de proyectos de espacio público en el ámbito europeo, lo que ha permitido identificar una serie de parámetros que, posteriormente, se aplican a nueve ejemplos representativos en Madrid, Barcelona y Zaragoza. El objetivo es efectuar evaluaciones sobre la calidad de los espacios públicos y determinar en qué medida están en relación con las condiciones de seguridad, accesibilidad e inclusividad que estos ofrecen. The polycentric, compact city with quality public spaces constitutes an implicit urban model in the Sustainable Development Goals (SDGs). The New Urban Agenda promotes the quality of public space as a common good. Therefore, it is pertinent to reconsider the quality parameters and investigate its development potential. This article is based on a theoretical and methodological reflection on the quality of public spaces, taking into account the contributions of the urban tradition. With this perspective, a selection of public space projects in the European sphere has been analyzed. This has made it possible to identify a series of parameters that are subsequently applied to nine representative examples in Madrid, Barcelona and Zaragoza. The objective is to carry out evaluations on the quality of public spaces and determine to what extent they are in relation to the conditions of security, accessibility and inclusivity that they offer

Radiation Produces Irreversible Chronic Dysfunction in the Submandibular Glands of the Rat

The exposure to high doses of ionizing radiation during radiotherapy results in severe morphological and functional alterations of the salivary glands, such as xerostomia. In the present study we investigated the chronic effect of a single radiation dose of 15 Gray (Gy) limited to head and neck on rat salivary gland function (salivary secretion and gland mass) and histology. Results indicate that norepinephrine (NE)-induced salivary secretion was reduced significantly at 30, 90, 180 and 365 days after the administration of a single dose of 15 Gy of ionizing radiation compared to non-irradiated animals. The maximal secretory response was reduced by 33% at 30 and 90 days post irradiation. Interestingly, a new fall in the salivary response to NE was observed at 180 days and was maintained at 365 days post irradiation, showing a 75% reduction in the maximal response. The functional fall of the salivary secretion observed at 180 days post irradiation was not only associated with a reduction of gland mass but also to an alteration of the epithelial architecture exhibiting a changed proportion of ducts and acini, loss of eosinophilic secretor granular material, and glandular vacuolization and fibrosis. On the basis of the presented results, we conclude that ionizing radiation produces irreversible and progressive alterations of submandibular gland (SMG) function and morphology that leads to a severe salivary hypo-function