The Conditions Needed for a Buffer to Set the pH in a System

It is a known fact that buffer systems are widely used in industry and in diverse laboratories to maintain the pH of a system within desired limits, occasionally narrow. Hence, the aim of the present work is to study the buffer capacity and buffer efficacy in order to determine the useful conditions to impose the pH on a given system. This study is based on the electroneutrality and component balance equations for a mixture of protons polyreceptors. The added volume equations were established, V, for strong acids or bases, as well as the buffer capacity equations with dilution effect, β dil, and the buffer efficacy, ε, considering that the analyte contains a mixture of the species of the same polyacid system or of various polyacid systems. The ε index is introduced to define the performance of a buffer solution and to find out for certain, whether the buffer is adequate or not to set the pH of a system, given the proper conditions and characteristics

Estudio de extracción de polifenoles de thalassia testuidum

Un aspecto crucial en la evolución del hombre lo constituyó el aprender a curar sus enfermedades a partir de lo que le proporcionaba la naturaleza; dentro de esos elementos se destacan predominantemente los vegetales. Así, el uso de las plantas ha sido un contribuyente importante al desarrollo de la farmacoterapia moderna. Debido a las condiciones físicas y químicas del ambiente marino, casi la totalidad de los organismos que habitan los mares exhiben una variedad de moléculas con cualidades estructurales y químicas únicas, producto del desarrollo de mecanismos bioquímicos y fisiológicos, que incluyen la producción de compuestos bioactivos para propósitos tales como la reproducción,  comunicación, protección contra depredación, infecciones y competencia [4]. El uso de organismos marinos, y en especial las algas, para la producción de cosméticos se encuentra en auge en muchos países. Existe una gran variedad de productos cosméticos a nivel mundial, por la evidencia de las propiedades beneficiosas de las algas como promotores de la síntesis de fibras colágenas, antioxidantes, antiirritantes [6]. Específicamente, el extracto obtenido a partir de la angiosperma Thalassia testudinum denominado BM-21, ha sido el más estudiado y plantea un gran interés por su acción dermorregeneradora y potente capacidad antioxidante. Actualmente, las condiciones de obtención del extracto son: relación de material vegetal-volumen de disolvente 1:10, disolvente etanol al 50 %, temperatura de extracción 60 °C, tiempo de extracción 4 h. Si bien el BM-21 como materia prima ha resultado excelente por sus propiedades, desde el punto de vista tecnológico se necesita mejorar la etapa de extracción del proceso de producción con el objetivo de lograr una mayor extracción del producto en el menor tiempo posible

Propuesta para generar modelos de construcción BIM de proyectos de edificación

El uso de nuevas tecnologías de información contribuye a la atenuación de los efectos producidos por la división de los procesos necesarios para la ejecución de los proyectos de ingeniería, entre otras causas. La adopción y uso actual del Building Information Modeling (BIM) proporciona una base para la gestión y conducción de proyectos, cuya información contenida en un modelo inteligente se puede relacionar a las etapas del ciclo de vida de los proyectos de edificación. El objetivo general de este trabajo de investigación es la determinación de los criterios para generar modelos BIM aplicables en la etapa de construcción de los proyectos de edificación en el estado de Yucatán. La metodología planteada consiste en llevar a cabo un estudio de caso sobre un proyecto de edificación, el cual será analizado para determinarán los conceptos de obra que serán los componentes del modelo BIM de construcción y se desarrollará un instrumento en formato digital (cédula) para la recopilación de datos. Una vez concluido el modelo BIM, se obtendrán las directrices para su elaboración, así como una librería de objetos paramétricos para cada componente del modelo y se realizará un diagrama de flujo para exponer la secuencia de generación del modelo BIM

Shrike predation on the lizard Mesalina adramitana in Qatar; a review of reported reptile and amphibian prey

We report, for the first time, evidence of predation by a shrike (Lanius sp.) on the lizard Mesalina adramitana. This is the first record of predation by shrikes on lizards in Qatar. Whilst we did not directly observe the event, the presence of shrikes in the area and the method of impalement indicate shrikes as the predator. The lizard was found freshly impaled on a palm tree (Phoenix dactylifera), at 150 cm above ground. Bird species of the genus Lanius are well-known predators of lizards, and in arid environments reptiles are likely common prey for these birds. We provide a review of literature concerning predatory events by shrikes on reptiles and amphibians. We suggest inspection of shrubs for animals impaled by shrikes can improve biodiversity inventories, complementing other commonly used methods

Exploring Health Science Students’ Notions on Organ Donation and Transplantation: A Multicenter Study

The knowledge acquired during university education about organ donation and transplantation (ODT) decisively influences the information future health professionals transmit. This is important in ODT where the participation of the general public is essential to obtain organs. Objective: To determine notions of Spanish medicine and nursing students on ODT and its relationship with attitude toward ODT. Methods and Design: and design. We conducted a sociologic, multicenter, and observational study. The population for our study consisted of medical and nursing students in Spanish universities. Our database was the Collaborative International Donor Project, stratified by geographic area and academic course. A validated questionnaire (PCID-DTO-RIOS) was self-administered and completed anonymously. Our sample consisted of 9598 medical and 10, 566 nursing students (99% confidence interval; precision of ±1%), stratified by geographic area and year of study. Results: The completion rate for our study was 90%. Only 20% (n=3640) of students thought their notions on ODT were good; 41% (n=7531) thought their notions were normal; 36% (n=6550) thought their notions were scarce. Comparing groups, there were differences between those who believed that their notions on ODT were good (44% nursing vs 56% medical students; P < .000), and those who believed it scarce (54% nursing vs 46% medical students; P < .000). Notions on ODT were related with attitude toward the donation of one''s own organs: those who considered their notions were good were more in favor then those who considered it scarce (88% vs 72%; P < .000). Conclusion: Only 20% of Spanish medical and nursing students thought their notions on ODT were good. Having good knowledge is related to a favorable attitude towards ODT. Receiving specific information on the subject could improve their knowledge about ODT during their training

Numerical hydrodynamics in general relativity

The current status of numerical solutions for the equations of ideal general relativistic hydrodynamics is reviewed. With respect to an earlier version of the article the present update provides additional information on numerical schemes and extends the discussion of astrophysical simulations in general relativistic hydrodynamics. Different formulations of the equations are presented, with special mention of conservative and hyperbolic formulations well-adapted to advanced numerical methods. A large sample of available numerical schemes is discussed, paying particular attention to solution procedures based on schemes exploiting the characteristic structure of the equations through linearized Riemann solvers. A comprehensive summary of astrophysical simulations in strong gravitational fields is presented. These include gravitational collapse, accretion onto black holes and hydrodynamical evolutions of neutron stars. The material contained in these sections highlights the numerical challenges of various representative simulations. It also follows, to some extent, the chronological development of the field, concerning advances on the formulation of the gravitational field and hydrodynamic equations and the numerical methodology designed to solve them.Comment: 105 pages, 12 figures. The full online-readable version of this article, including several animations, will be published in Living Reviews in Relativity at http://www.livingreviews.or

A High Accurate Approximation for a Galactic Newtonian Nonlinear Model Validated by Employing Observational Data

This article proposes Perturbation Method (PM) to solve nonlinear problems. As case study PM is employed to provide a detailed study of a nonlinear galactic model. Our approach is rather elementary and seeks to explain as much detail as possible the material of this work.In particular our solution gives rise qualitatively, to the known flat rotation curves. In fact, we compare the numerical solution and the obtained approximation by employing observational data proving the validity and high accuracy of the model under study