La contratación pública de obras: situación actual y puntos de mejora

La construcción pública ha sido, es y será uno de los pilares fundamentales del sector construcción español, si bien la actual situación de crisis económica y la reducción de la inversión pública en nuevas infraestructuras ha generado un descenso de actividad hasta niveles similares a los años noventa. El retorno a índices de actividad más elevados no solo se conseguirá con la recuperación de la economía del país, sino que será necesario realizar ciertas mejoras en los procesos de licitación con objeto de conseguir una mayor funcionalidad y flexibilidad en la contratación pública de obras

La importancia del curado en el comportamiento posterior frente a la corrosión de las estructuras de hormigón armado

Steel in contact with fresh concrete is covered by a layer of passivating oxydes due to the alkaline nature of the pore solution. The presence of oxygen plays an important role in this passivation process as well as in the corrosión one when is developped due to the ingress of aggressives, such as, chioride ions. In the present paper, results are commented on the behaviour found when oxygen is limited due to the concrete curing conditions, in a completely saturated chamber Surprisely, the results indícate that the oxygen availability during the curing has a marked influence on the future corrosión beabieviour This allows to deduce that the mechanisms involved are not so simple as was currently accepted and that new specific tests are needed to clarify the controversial points. &nbsp

Food hub: Una alternativa para alimentar las ciudades de manera sostenible

La tarea de alimentar las ciudades es un reto al que hoy se enfrentan todos los gobiernos e implica una coordinación de múltiples productores, distribuidores, operadores logísticos y comerciantes de alimentos perecederos. Este artículo pretende analizar los Food hubs en el sistema de distribución urbano de alimentos, de manera crítica y sistemática desde la literatura. Se presenta en primera instancia un estado del arte sobre el concepto de Food hub, luego se presenta una propuesta de tipificación de Food hubs de acuerdo a unos criterios, concentrándose en actores implicados en el proceso de distribución de alimentos, estructura jurídica y sus funciones. También se describen los impactos sociales, económicos y medioambientales que traería consigo la implementación de un Food hub. Finalmente, se presentan las principales oportunidades para la expansión de Food hubs urbanos y se exponen cuatro ejemplos latinoamericanos, relacionándolos con la tipología propuesta. Food hub as an efficient alternative to sustainably feed the cities. The task of feeding cities is a challenge that nowadays all governments face, it involves the coordination of multiple producers, distributors, logistics operators and traders of perishable foods. This paper analyzes the Food hubs concept and its impact on urban development in a critical perception from the literature review. The state of the art on the concept of Food Hub is presented at first instance. Then a classification of different types of Food hub is done by focusing on the actors involved in the food system distribution process, structure and functions. After that, an analysis of the prospects of the implementation of Food hubs is performed, evaluating its economic, social and environmental impacts. Finally, the main opportunities for the deployment of urban Food hubs are presented, and four Latin-American cases are introduced, linked them with the proposed typolog

Spectroelectrochemical Studies of CTAB Adsorbed on Gold Surfaces in Perchloric Acid

The behaviour of CTAB adsorbed on polycrystalline gold electrodes has been studied using a combination of spectroelectrochemical methods. The results indicate that the formation of the layer is the consequence of the precipitation of the CTAB micelles on the electrode surface as bromide ions, which stabilize the micelles, are replaced by perchlorate anions. This process leads to the formation of CTA+ layers in which perchlorate ions are intercalated, in which the adlayer suffers a continuous rearrangement that leads to the formation of micro-dominions of different types of hydrogen-bonded water populations throughout the adlayer. After prolonged cycling, a stable situation is reached. Under these conditions, water molecules permeate through the adlayer toward the electrode surface at potentials positive of the potential of zero charge, due to the repulsion between the CTA+ layer and the positive charge of the electrode.This research was funded by Ministerio de Ciencia e Innovación (Spain) grant number PID2019-105653GB-I00), Generalitat Valenciana (Spain) grant number PROMETEO/2020/063. A.C. gratefully acknowledges the support of the University of Aberdeen

La importancia del curado en el comportamiento posterior frente a la corrosión de las estructuras de hormigón armado

Steel in contact with fresh concrete is covered by a layer of passivating oxydes due to the alkaline nature of the pore solution. The presence of oxygen plays an important role in this passivation process as well as in the corrosión one when is developped due to the ingress of aggressives, such as, chloride ions. In the present paper, results are commented on the behaviour found when oxygen is limited due to the concrete curing conditions, in a completely saturated chamber. Surprisely, the results indicate that the oxygen availability during the curing has a marked influence on the future corrosion beabieviour This allows to deduce that the mechanisms involved are not so simple as was currently accepted and that new specific tests are needed to clarify the controversial points.Cuando el acero se pone en contacto con el hormigón fresco, debido a la naturaleza alcalina de éste, el acero se recubre de una capa de óxidos pasivantes, que lo mantienen constantemente protegido. En este proceso juega un papel preponderante la presencia del oxígeno, que resulta también esencial para el desarrollo de los procesos de corrosión, cuando hay agresivos presentes (por ejemplo los cloruros). En el presente trabajo se comentan resultados de los cambios que se aprecian, tanto en el proceso de pasivación como de corrosión, cuando el acceso de oxígeno se limita, circunstancia que se produce cuando el hormigón se cura en condiciones de saturación de agua. Los resultados muestran que la disponibilidad de oxígeno durante el curado tiene una marcada influencia en la resistencia futura a la corrosión lo, que indica que los mecanismos no son tan evidentes como se pensaba y se necesitarán ensayos futuros específicos para aclarar todos los aspectos que ahora aparecen como contradictorio

On the behavior of CTAB/CTAOH adlayers on gold single crystal surfaces

The behavior of adsorbed CTAB and CTAOH on gold single crystal electrodes has been studied in solutions with different pH values. For the different single crystal electrodes, the adsorbed adlayer formed by CTA+ cations is in contact with the surface, when the electrode charge is negative. As the surface charge becomes positive, the adlayer detaches from the surface and water molecules permeate through it, giving rise to characteristic peaks in the voltammogram. Charge and laser induced jump temperature measurements show that the composition of the adlayer contains not only the CTA+ cations but also anions, which are required to stabilize the adlayer. In alkaline solutions, the higher solubility of CTAB/CTAOH in alkaline solutions leads to the partial desorption of the adlayer when these species are not present in the solution. When CTAB or CTAOH are dissolved in the alkaline cell solution, the adlayer is strongly bonded to the surface in the whole potential window due to the negative charge of the surface.Financial support from Ministerio de Ciencia e Innovación (Project PID2019-105653GB-I00) and Generalitat Valenciana (Project PROMETEO/2020/063) is acknowledged

Determining optimal flight paths for cellular network connectivity for the transmission of real-time physiological data in support of big data analytics during airborne critical care transport

This thesis presents a methodology for determining the optimal flight paths between two geographical points based on distance and cellular reception over the path. This methodology consists of two main concepts: coverage map generation, and path planning. Coverage map generation creates a grid map of the total planning space that contains coverage information for each grid point. Coverage is calculated based on geographical and technical information regarding each cell tower in the planning area. The planning step utilises the coverage map to plan a route based on minimum distance and maximum coverage, which is then smoothed into a feasible route for an aircraft to follow. This methodology is demonstrated in an airborne critical care transport within the Province of Ontario in Canada context. Leveraging available cellular information, this methodology is used to determine optimal paths between various care centres or their closest airport. Evaluation reveals that optimal routes can be found through this methodology

Validation of bioelectrical impedance analysis for body composition assessment in children with obesity aged 8-14y

BACKGROUND & AIMS: The aim was to generate a predictive equation to assess body composition (BC) in children with obesity using bioimpedance (BIA), and avoid bias produced by different density levels of fat free mass (FFM) in this population. METHODS: This was a cross-sectional validation study using baseline data from a randomized intervention trial to treat childhood obesity. Participants were 8 to 14y (n = 315), underwent assessments on anthropometry and BC through Air Displacement Plethysmography (ADP), Dual X-Ray Absorptiometry and BIA. They were divided into a training (n = 249) and a testing subset (n = 66). In addition, the testing subset underwent a total body water assessment using deuterium dilution, and thus obtained results for the 4-compartment model (4C). A new equation to estimate FFM was created from the BIA outputs by comparison to a validated model of ADP adjusted by FFM density in the training subset. The equation was validated against 4C in the testing subset. As reference, the outputs from the BIA device were also compared to 4C. RESULTS: The predictive equation reduced the bias from the BIA outputs from 14.1% (95%CI: 12.7, 15.4) to 4.6% (95%CI: 3.8, 5.4) for FFM and from 18.4% (95%CI: 16.9, 19.9) to 6.4% (95% CI: 5.3, 7.4) for FM. Bland-Altman plots revealed that the new equation significantly improved the agreement with 4C; furthermore, the observed trend to increase the degree of bias with increasing FM and FFM also disappeared. CONCLUSION: The new predictive equation increases the precision of BC assessment using BIA in children with obesity

Capecitabine and bevacizumab as first-line treatment in elderly patients with metastatic colorectal cancer

BACKGROUND: The efficacy and safety of capecitabine and bevacizumab in elderly patients with metastatic colorectal cancer (mCRC) considered unsuitable for receiving first-line chemotherapy with an irinotecan or oxaliplatin-based combination were assessed in a phase II, open, multicentre, uncontrolled study. METHODS: Treatment consisted of capecitabine 1250 mgm 2 (or 950 mgm 2 for patients with a creatinine clearance of 30–50ml min 1) twice daily on days 1–14 and bevacizumab (7.5 mg kg 1) on day 1 every 3 weeks. RESULTS: A total of 59 patients aged X70 years with mCRC were enrolled. In an intention-to-treat analysis, the overall response rate was 34%, with 71% of patients achieving disease control. Median progression-free survival and overall survival were 10.8 months and 18 months, respectively. In all, 32 patients (54%) had grade 3/4 adverse events (AEs), the most common being hand–foot syndrome (19%), diarrhoea (9%) and deep venous thrombosis (7%). Four patients died because of treatment-related AEs. A relationship was detected between creatinine clearance p50 ml min 1 and the development of non-bevacizumab-related grade 3/4 AEs. The incidence of bevacizumab-associated AEs (hypertension, thromboembolic events and proteinuria) was consistent with that of previous reports in elderly patients. CONCLUSION: Bevacizumab combined with capecitabine represents a valid therapeutic alternative in elderly patients considered to be unsuitable for receiving polychemotherapy.This study was supported by Hoffmann-La Roche, Nutley, NJ, USA