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

Cálculo del coeficiente de difusión del Zn en un disolvente eutéctico profundo mediante técnicas electroquímicas

En el presente trabajo se llevó a cabo la determinación electroquímica del coeficiente de difusión del Zn²⁺, en un disolvente eutéctico profundo compuesto por cloruro de colina y urea, en una relación molar de 1:2, a una temperatura de 70 °C. Para ello se emplearon las técnicas electroquímicas de voltamperometría cíclica y cronoamperometría. A partir de los transitorios potenciostáticos de corriente, de la ecuación de Cottrell y mediante el análisis de las coordenadas del máximo, se calculó el valor para D= 4.76x10-⁸ cm²s-¹ y D= 6.71x10-⁸ cm²s-¹, respectivamente.In the present work it was carried out the electrochemical determination of the diffusion coefficient of Zn²⁺, in a deep eutectic solvent composed of choline chloride and urea in a molar ratio of 1:2, at a temperature of 70°C. For this, the electrochemical techniques of cyclic voltammetry and chronoamperometry were used. From potentiostatic current transients and Cottrell equation, the value for D=4.76x10-⁸ cm²s-¹ and D=4.76x10-⁸ cm²s-¹ was calculated, respectively

Cuantificación electroquímica de la superficie electroactiva de nanopartículas de Au soportadas sobre ITO a diferentes monocapas mediante electrodepósito de Cu a subpotencial

En el presente trabajo, se llevó a cabo la determinación del área superficial activa, ASA, de nanopartículas de Au, AuNPs, soportadas sobre ITO, a diferentes monocapas de AuNPs. Para llevar a cabo lo anterior, se formaron monocapas de AuNPs sobre la superficie del electrodo de ITO a través de un policatión, la poli L-lisina, PLL, entre cada capa. Una vez formada cada monocapa, se lleva a cabo el proceso de electrodepósito de Cu a subpotencial, UPD, en una disolución acuosa de Cu²⁺, empleando las técnicas electroquímicas de voltamperometría cíclica y cronoamperometría. Del análisis de los transitorios potenciostáticos de corriente se determinó la carga eléctrica involucrada en el proceso de formación de cada monocapa, y a partir de esta se determinó el ASA con respecto a las monocapas 1, 2 y 5.The present work was conducted to determine the active surface area, ASA, of Au nanoparticles, AuNPs, supported on ITO, to different monolayers AuNPs. To perform the above, AuNPs monolayers on the surface of ITO electrode is formed through a polycation, poly L-lysine, PLL, between each layer. Each monolayer once formed, is held the Cu electroplating process underpotential, UPD, in an aqueous solution of Cu²⁺, using electrochemical techniques such as cyclic voltammetry and chronoamperometry. Analysis potentiostatic current transient electrical load involved in the formation of each monolayer was determined, and from this, the ASA was determined over monolayers 1, 2 and 5

Prácticas del laboratorio de metalurgia I : cristales perfectos e imperfectos : para la carrera de ingeniería metalúrgica

1 archivo PDF (66 páginas) ; 2a ed.Prácticas para servir como una guía en el laboratorio de metalurgia I, que es el complemento del curso de cristales perfectos e imperfectos que se imparte para la carrera de Ingeniería Metalúrgica

An Exact Method to Determine the Conductivity of Aqueous Solutions in Acid-Base Titrations

Several works in the literature show that it is possible to establish the analytic equations to estimate the volume V of a strong base or a strong acid (Vb and Va, resp.) being added to a solution of a substance or a mix of substances during an acid-base titration, as well as the equations to estimate the first derivative of the titration plot dpH/dV, and algebraic expressions to determine the buffer β capacity with dilution βdil. This treatment allows establishing the conditions of thermodynamic equilibria for all species within a system containing a mix of species from one or from various polyacid systems. The present work shows that it is possible to determine exactly the electric conductivity of aqueous solutions for these Brønsted acid-base titrations, because the functional relation between this property and the composition of the system in equilibrium is well known; this is achieved using the equivalent conductivity λi values of each of the ions present in a given system. The model employed for the present work confirms the experimental outcomes with the H2SO4, B(OH)3, CH3COOH, and H3PO4 aqueous solutions’ titration

Discovering HIV related information by means of association rules and machine learning

Acquired immunodeficiency syndrome (AIDS) is still one of the main health problems worldwide. It is therefore essential to keep making progress in improving the prognosis and quality of life of affected patients. One way to advance along this pathway is to uncover connections between other disorders associated with HIV/AIDS-so that they can be anticipated and possibly mitigated. We propose to achieve this by using Association Rules (ARs). They allow us to represent the dependencies between a number of diseases and other specific diseases. However, classical techniques systematically generate every AR meeting some minimal conditions on data frequency, hence generating a vast amount of uninteresting ARs, which need to be filtered out. The lack of manually annotated ARs has favored unsupervised filtering, even though they produce limited results. In this paper, we propose a semi-supervised system, able to identify relevant ARs among HIV-related diseases with a minimal amount of annotated training data. Our system has been able to extract a good number of relationships between HIV-related diseases that have been previously detected in the literature but are scattered and are often little known. Furthermore, a number of plausible new relationships have shown up which deserve further investigation by qualified medical experts

Evaluation of a quality improvement intervention to reduce anastomotic leak following right colectomy (EAGLE): pragmatic, batched stepped-wedge, cluster-randomized trial in 64 countries

Background Anastomotic leak affects 8 per cent of patients after right colectomy with a 10-fold increased risk of postoperative death. The EAGLE study aimed to develop and test whether an international, standardized quality improvement intervention could reduce anastomotic leaks. Methods The internationally intended protocol, iteratively co-developed by a multistage Delphi process, comprised an online educational module introducing risk stratification, an intraoperative checklist, and harmonized surgical techniques. Clusters (hospital teams) were randomized to one of three arms with varied sequences of intervention/data collection by a derived stepped-wedge batch design (at least 18 hospital teams per batch). Patients were blinded to the study allocation. Low- and middle-income country enrolment was encouraged. The primary outcome (assessed by intention to treat) was anastomotic leak rate, and subgroup analyses by module completion (at least 80 per cent of surgeons, high engagement; less than 50 per cent, low engagement) were preplanned. Results A total 355 hospital teams registered, with 332 from 64 countries (39.2 per cent low and middle income) included in the final analysis. The online modules were completed by half of the surgeons (2143 of 4411). The primary analysis included 3039 of the 3268 patients recruited (206 patients had no anastomosis and 23 were lost to follow-up), with anastomotic leaks arising before and after the intervention in 10.1 and 9.6 per cent respectively (adjusted OR 0.87, 95 per cent c.i. 0.59 to 1.30; P = 0.498). The proportion of surgeons completing the educational modules was an influence: the leak rate decreased from 12.2 per cent (61 of 500) before intervention to 5.1 per cent (24 of 473) after intervention in high-engagement centres (adjusted OR 0.36, 0.20 to 0.64; P < 0.001), but this was not observed in low-engagement hospitals (8.3 per cent (59 of 714) and 13.8 per cent (61 of 443) respectively; adjusted OR 2.09, 1.31 to 3.31). Conclusion Completion of globally available digital training by engaged teams can alter anastomotic leak rates. Registration number: NCT04270721 (http://www.clinicaltrials.gov)