Evaluation of Chloride Diffusion and Corrosion Resistance in Reinforced Concrete Using Internal Curing and Shrinkage Reducing Admixtures

The properties of high-performance concretes obtained by the internal curing technique were studied in the fresh and hardened states. In some of the concrete mixtures, fine normal weight aggregates were replaced with lightweight aggregates (LWA) at 20 % vol. and ordinary portland cement was replaced by pulverized class F fly ash at 20 % by mass. Additionally, some mixtures were prepared including a shrinkage-reducing admixture, either as part of the mixing water or pre-soaked into the lightweight fine aggregates. The prepared concretes were subjected to degradation tests, such as accelerated carbonation and chloride ion deterioration. In addition, the reinforced concretes were analyzed through electrochemical corrosion tests with the linear polarization resistance technique. It was found that the internally cured concretes presented a mechanical resistance similar to those reported for the reference concretes (conventional concretes), but provided a higher resistance to carbonation, rapid penetration of chloride ions, and a lower chloride ion diffusion coefficient. The reinforcing steel structure in the internally cured concretes showed lower corrosion currents (Icorr) and corrosion potentials (Ecorr) in comparison to the reference concretes. Therefore, the use of the internal curing technique in concretes with pre-soaking in either water or a solution of shrinkage-reducing admixture can be considered as a viable alternative to extend the service life of concrete structures in contact with harmful environments

Measurement of polluting emissions of vehicles with gasoline engines, using static test

Articulo de Investigación.The pollutant emissions of vehicles with gasoline engine are analyzed, carrying out a verification of polluting emissions with static test, which allows knowing the chemical composition of five combustion gases coming from the exhaust of cars: CO, CO, NOx and unburned hydrocarbons (HC) as well as excess oxygen (O2). Random tests of emissions of polluting gases of private vehicles will be carried out, taking as sample the vehicles that move to the facilities of the UAEM Nezahualcóyotl University Center. The results will be analyzed based on the criteria established in the pollutant emission standards established for the circulation of light automotive vehicles (NOM-041-SEMARNAT-2015, NOM 042-SEMARNAT-2003 and NOM-EM-167- SEMARNAT-2016 ). As a result of the investigation, the polluting emissions from car exhaust were measured, the relationship between the type of pollutant found, the possible causes or failures in the emission control systems of gasoline vehicles was established. The preventive maintenance strategieSecretaria de Investigación de la Universidad Autonoma del Estado de México, Proyectos UAEM con financiamiento

Lessons learned obtaining informed consent in research with vulnerable populations in community health center settings

<p>Abstract</p> <p>Background</p> <p>To improve equity in access to medical research, successful strategies are needed to recruit diverse populations. Here, we examine experiences of community health center (CHC) staff who guided an informed consent process to overcome recruitment barriers in a medical record review study.</p> <p>Methods</p> <p>We conducted ten semi-structured interviews with CHC staff members. Interviews were audiotaped, transcribed, and structurally and thematically coded. We used NVivo, an ethnographic data management software program, to analyze themes related to recruitment challenges.</p> <p>Results</p> <p>CHC interviewees reported that a key challenge to recruitment included the difficult balance between institutional review board (IRB) requirements for informed consent, and conveying an appropriate level of risk to patients. CHC staff perceived that the requirements of IRB certification itself posed a barrier to allowing diverse staff to participate in recruitment efforts. A key barrier to recruitment also included the lack of updated contact information on CHC patients. CHC interviewees reported that the successes they experienced reflected an alignment between study aims and CHC goals, and trusted relationships between CHCs and staff and the patients they recruited.</p> <p>Conclusions</p> <p>Making IRB training more accessible to CHC-based staff, improving consent form clarity for participants, and developing processes for routinely updating patient information would greatly lower recruitment barriers for diverse populations in health services research.</p

Modelo de equilibrio espacial para determinar costos de transporte en la distribución de durazno en México

In México, peach as a seasonal fruit has a very large range in prices, in addition to this, it has poor infrastructure to preserve the fruit in refrigerated conditions, the reduced shelf-life and, coupled with localized areas of production, long distances are needed to be traveled in order for the product to reach the consumer. Furthermore, the concentration of production in one period causes excess supply, favoring the consumers and consequently reducing the profit margin for the producers. In this sense, this paper developed in 2011, raises the possibility of reducing expenses for transportation by planning the regional production, considering quality and variety of peaches that consumers expect. In order to do this, we formulated a linear model of distribution that includes economic variables of the peach-market, aiming to minimize transportation costs of the possible routes that can be activated when running the model. Using two scenarios; a basic one and the other with 20% increase in production. The results indicate that it is possible to determine optimal routes at the lowest costs, just as it is possible to find the best way to distribute peach in the country. With an increase in the peach production of 20%, reducing the costs of transport and has a better distribution.En México, el durazno como fruto estacional tiene un rango muy grande en cuanto a precio, además, la poca infraestructura para conservar la fruta en condiciones de refrigeración, su reducida vida útil de anaquel y aunado a las zonas muy localizadas de producción hace que se tengan que recorrer grandes distancias para que el producto llegue a los consumidores. Además, la concentración de la producción en un sólo periodo provoca excesos de oferta, favoreciendo a los consumidores y como consecuencia reduciendo el margen de utilidad de los productores. En este sentido el presente trabajo, desarrollado en el año 2011, plantea la posibilidad de reducir gastos por concepto de transportación si se planea la producción regional considerando calidad y variedad de duraznos que los consumidores regionales esperan. Para ello, se formuló un modelo lineal de distribución que incluye las variables económicas del mercado del durazno, el cual pretende minimizar los costos de transporte de las posibles rutas que se pueden activar cuando se ejecuta el modelo. Se manejan dos escenarios; uno base y uno con un aumento de 20% en la producción. Los resultados indican, que es posible determinarlas rutas óptimas al menor costo posible, de igual manera, es posible encontrar la mejor forma de distribución del durazno en el país. Con un aumento en la producción de durazno de 20% se reducen los costos de transporte y se tiene una mejor distribución

Risk of COVID-19 after natural infection or vaccinationResearch in context

Background: While vaccines have established utility against COVID-19, phase 3 efficacy studies have generally not comprehensively evaluated protection provided by previous infection or hybrid immunity (previous infection plus vaccination). Individual patient data from US government-supported harmonized vaccine trials provide an unprecedented sample population to address this issue. We characterized the protective efficacy of previous SARS-CoV-2 infection and hybrid immunity against COVID-19 early in the pandemic over three-to six-month follow-up and compared with vaccine-associated protection. Methods: In this post-hoc cross-protocol analysis of the Moderna, AstraZeneca, Janssen, and Novavax COVID-19 vaccine clinical trials, we allocated participants into four groups based on previous-infection status at enrolment and treatment: no previous infection/placebo; previous infection/placebo; no previous infection/vaccine; and previous infection/vaccine. The main outcome was RT-PCR-confirmed COVID-19 >7–15 days (per original protocols) after final study injection. We calculated crude and adjusted efficacy measures. Findings: Previous infection/placebo participants had a 92% decreased risk of future COVID-19 compared to no previous infection/placebo participants (overall hazard ratio [HR] ratio: 0.08; 95% CI: 0.05–0.13). Among single-dose Janssen participants, hybrid immunity conferred greater protection than vaccine alone (HR: 0.03; 95% CI: 0.01–0.10). Too few infections were observed to draw statistical inferences comparing hybrid immunity to vaccine alone for other trials. Vaccination, previous infection, and hybrid immunity all provided near-complete protection against severe disease. Interpretation: Previous infection, any hybrid immunity, and two-dose vaccination all provided substantial protection against symptomatic and severe COVID-19 through the early Delta period. Thus, as a surrogate for natural infection, vaccination remains the safest approach to protection. Funding: National Institutes of Health

Risk of COVID-19 after natural infection or vaccinationResearch in context

Summary: Background: While vaccines have established utility against COVID-19, phase 3 efficacy studies have generally not comprehensively evaluated protection provided by previous infection or hybrid immunity (previous infection plus vaccination). Individual patient data from US government-supported harmonized vaccine trials provide an unprecedented sample population to address this issue. We characterized the protective efficacy of previous SARS-CoV-2 infection and hybrid immunity against COVID-19 early in the pandemic over three-to six-month follow-up and compared with vaccine-associated protection. Methods: In this post-hoc cross-protocol analysis of the Moderna, AstraZeneca, Janssen, and Novavax COVID-19 vaccine clinical trials, we allocated participants into four groups based on previous-infection status at enrolment and treatment: no previous infection/placebo; previous infection/placebo; no previous infection/vaccine; and previous infection/vaccine. The main outcome was RT-PCR-confirmed COVID-19 >7–15 days (per original protocols) after final study injection. We calculated crude and adjusted efficacy measures. Findings: Previous infection/placebo participants had a 92% decreased risk of future COVID-19 compared to no previous infection/placebo participants (overall hazard ratio [HR] ratio: 0.08; 95% CI: 0.05–0.13). Among single-dose Janssen participants, hybrid immunity conferred greater protection than vaccine alone (HR: 0.03; 95% CI: 0.01–0.10). Too few infections were observed to draw statistical inferences comparing hybrid immunity to vaccine alone for other trials. Vaccination, previous infection, and hybrid immunity all provided near-complete protection against severe disease. Interpretation: Previous infection, any hybrid immunity, and two-dose vaccination all provided substantial protection against symptomatic and severe COVID-19 through the early Delta period. Thus, as a surrogate for natural infection, vaccination remains the safest approach to protection. Funding: National Institutes of Health