EFECTOS SOCIOTERRITORIALES DE LAS POLÍTICAS NEOLIBERALES EN LA AGRICULTURA DEL MAÍZ: EL CASO DEL DISTRITO DE DESARROLLO RURAL ATLACOMULCO DEL ESTADO DE MÉXICO. 1990-2015

La reestructuración del sector agrario nacional, inducida por las políticas neoliberales implementadas a finales de los años ochenta y principios de los noventa del siglo pasado, lejos de incentivar la siembra de maíz y considerando el principio de las ventajas comparativas, ha tratado de orientar el camino de la agricultura mexicana hacia la producción de cultivos más competitivos en el mercado internacional, entre los cuales no figura el maíz. Aunado a lo anterior, también ha propuesto un esquema de producción en el que sólo los grandes y medianos productores de maíz han logrado insertarse en el nuevo modelo agrícola, dejando un tanto a la deriva a los pequeños productores. El DDR Atlacomulco, ubicado en la porción noroccidental del estado de México, se ha caracterizado por ser un área tradicionalmente importante en la producción de maíz, y a partir del análisis estadístico de sus factores de producción durante el periodo comprendido entre 1990 y 2015, en el presente trabajo se determinan cuáles han sido los principales cambios dentro de la actividad maicera en el marco de la implementación de las políticas neoliberales en la agricultura. Asimismo, se hace una reflexión de la situación del DDR Atlacomulco con respecto a las perspectivas señaladas por algunos autores con relación al posible destino de la agricultura del maíz a nivel nacional como consecuencia del giro neoliberal del campo mexicano. Como resultado del trabajo se observa que la siembra de maíz no ha perdido su papel preponderante dentro de las actividades agrícolas de la región aunque ha sufrido cambios y presenta una ligera, pero constante, disminución, además de que se reconoce que la estructura laboral agrícola se ha reconfigurado con el paso del tiempo

Multifunctional microcapsules based on ZnO and n-octadecane: From thermal energy storage to photocatalytic activity

Energy management is one of the most important issues to be addressed in the near future in many fields, one of which is buildings. In this sense, new phase change materials (PCM) are being widely studied for storing energy. Encapsulating PCM is a good way to incorporate these materials into different applications in which energy storage is useful. In this study, microcapsules based on ZnO containing n-octadecane as a phase change material were synthesized and characterized with regard to their structural, morphological and optical properties according to several synthesis parameters, such as the proportion of precursors, stirring rate and ageing time. The microcapsules were characterized using x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and UV–Vis spectroscopy in diffuse reflectance mode. The presence of n-octadecane inside the capsules was confirmed. Their thermal behaviour was analysed by means of differential scanning calorimetry. Heating/cooling cycles were performed, after which the microcapsules presented good stability. Furthermore, the encapsulation efficiency was estimated from melting and crystallization enthalpy values, reaching a value of 23.1%. Moreover, the isobaric specific heat of the microcapsules is higher than that of ZnO, which means that substituting ZnO with microcapsules in buildings leads to an important increase in the amount of sensible heat stored. Finally, the photocatalytic activity of the microcapsules was analysed by studying the photodegradation of Crystal Violet dye. The degradation rate increased when the microcapsules were present, so the photocatalytic activity of the microcapsules was confirmed under UV and visible irradiation, which is of interest because they can be used to remove organic pollutants from buildings.10 página

Stability and Thermal Properties Study of Metal Chalcogenide-Based Nanofluids for Concentrating Solar Power

Nanofluids are colloidal suspensions of nanomaterials in a fluid which exhibit enhanced thermophysical properties compared to conventional fluids. The addition of nanomaterials to a fluid can increase the thermal conductivity, isobaric-specific heat, diffusivity, and the convective heat transfer coefficient of the original fluid. For this reason, nanofluids have been studied over the last decades in many fields such as biomedicine, industrial cooling, nuclear reactors, and also in solar thermal applications. In this paper, we report the preparation and characterization of nanofluids based on one-dimensional MoS2 and WS2 nanosheets to improve the thermal properties of the heat transfer fluid currently used in concentrating solar plants (CSP). A comparative study of both types of nanofluids was performed for explaining the influence of nanostructure morphologies on nanofluid stability and thermal properties. The nanofluids prepared in this work present a high stability over time and thermal conductivity enhancements of up to 46% for MoS2-based nanofluid and up to 35% for WS2-based nanofluid. These results led to an increase in the efficiency of the solar collectors of 21.3% and 16.8% when the nanofluids based on MoS2 nanowires or WS2 nanosheets were used instead of the typical thermal oil

Synthesis and characterization of metal oxide-based microcapsules including phase change materials for energy storage applications

In this study, microcapsules based on Cu2O containing different phase change materials (PCM) were prepared and characterized. The elemental, structural and electronic properties of the Cu2O-based microcapsules were characterized using several techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy and Fourier-transform infrared spectroscopy. In addition, the thermal properties of the microcapsules prepared were characterized in order to analyse their possible application as a thermal energy storage medium. Heating/cooling cycles using a differential scanning calorimetry technique were performed, and the phase change temperature and enthalpy were estimated. We observed good stability after the cycles. Furthermore, the encapsulation efficiency was estimated from melting and crystallization enthalpy values, reaching a value of 14.8% for the paraffin wax-based microcapsules. Finally, isobaric specific heat was measured to evaluate the storage capability of the encapsulated PCMs with regard to pure Cu2O to evaluate their possible application as a thermal storage system. An increase of around 140% was found in the isobaric specific heat for the microcapsules based on paraffin wax with regard to pure Cu2O. © 2023, The Author(s)

Improving the efficiency of the concentrating solar power plants using heat transfer nanofluids with gold nanoplates: An analysis from laboratory to industrial scale

We report about the remarkable changes in the thermophysical properties of the heat transfer fluid used in concentrating solar power plants with parabolic-trough collectors (Dowtherm A, a mixture of diphenyl oxide and biphenyl) by addition of Au nanoplates in mass fractions around 10−2 wt%. The resulting nanofluids are stable for weeks, and their enhanced physical properties make them good candidates for the application. Particularly, with 4.8·10−2 wt% of Au nanoplates, specific heat increases by 12.0 ± 1.2 % at 523 K and thermal conductivity increases by 24.9 ± 6.1 % at 373 K, with no measurable changes in density or dynamic viscosity. This set of physical properties allows to make a realistic estimation of the performance of a prototypical concentrating solar power plant using these nanofluids for solar-to-thermal energy conversion. We determine, using computational cost-free numerical models available in literature, that the performance of a concentrating solar power plant could increase up to 35.1 %, compared to the predicted 24.7 % with the conventional heat transfer fluid, with neither rheological penalties nor economically prohibitive structural changes. The findings here reported may contribute to encourage the application of heat transfer nanofluids in order to improve the efficiency of concentrating solar power plants, and to consolidate a working scheme that positively promotes the transition from laboratory scale to industrial scale. © 2023 The Author

Mobile App–Based Intervention for Adolescents With First-Episode Psychosis: Study Protocol for a Pilot Randomized Controlled Trial

Introduction: Previous studies have shown an improvement in the access to treatment for patients with first-episode psychosis (FEP), specifically young patients, through mobile app–based interventions. The aim of this study is to test the effectiveness of a mobile app–based intervention to improve community functioning in adolescents with FEP. Mobile app–based interventions could increase quality of life and disease awareness, which improve adherence to treatment and reduce the frequency of relapses and rehospitalizations in adolescents with FEP.Methods: This article describes a mobile app treatment and the pilot trial protocol for patients with FEP. We will perform a single-blind randomized clinical trial (RCT) including patients with FEP aged 14–19 years recruited from Gregorio Marañón Hospital, Madrid, Spain. Patients will be randomly assigned to an intervention group, which will receive treatment as usual plus five modules of a psychological intervention through the mobile app (psychoeducation, recognition of symptoms and prevention of relapses, problem solving, mindfulness, and contact wall), or to a control group (standard care). The effectiveness of the intervention will be assessed by means of an extensive battery of clinical tests at baseline and at 3 months of follow-up. The primary outcome is reduction in psychotic and depressive symptoms; secondary outcomes comprise adherence, awareness, use of drugs, and quality of life. Data will be analyzed on an intention-to-treat (ITT) basis. Mixed model repeated-measures analysis will be used to explore the following effect: group × time interaction between the control group and the intervention group for clinical and functional variables during the follow-up period.Discussion: This is an innovative study for the assessment of a psychological intervention through a mobile app for patients with FEP during the critical period. This pilot RCT is intended to be a precursor to larger studies, which in turn could facilitate dissemination of mobile app therapy for patients with FEP.Ethics and Dissemination: The local ethics committee approved the study protocol. All participants must sign the informed consent, to participate. After finalizing the study, the results will be published.Trial registration: NCT03161249. NCT clinicaltrials.gov. Date of registration in primary registry 02 May 2017. clinicaltrials.gov

Investigation of enhanced thermal properties in NiO-based nanofluids for concentrating solar power applications: A molecular dynamics and experimental analysis

Nanofluids could be a promising alternative to the typical heat transfer fluids (HTF) used in concentrating solar power. This study analyses nanofluids based on a typical HTF for concentrating solar power (CSP) applications and NiO nanoparticles. The optimum nanoparticle concentration was determined by analysing the stability of the nanofluids. Some of their properties, such as density, viscosity, isobaric specific heat and thermal con- ductivity, were characterized to evaluate their performance. Their thermal conductivity increased by up to 96% and the heat transfer coefficient by 50%. Molecular dynamics calculations were performed to explain from a molecular perspective how the presence of equal proportions of two surfactants, benzalkonium chloride (BAC) and 1-Octadecanethiol (ODT), enhanced the thermal properties of the NiO nanofluid. The isobaric specific heat and thermal conductivity values followed the same experimental tendency. The analysis of the radial distribu- tion functions (RDFs) and spatial distribution functions (SDFs) revealed an inner layer of base fluid and sur- factant molecules around the NiO cell. This first layer contained BAC molecules at all the temperatures, while ODT was only incorporated at higher temperatures. The exchange of surfactant and base fluid molecules around the NiO as the temperature increases may play an important role in the enhancement of the thermal properties

MoS2 nanosheets vs nanowires: preparation and theoretical study of highly stable and efficient nanofluids for Concentrating Solar Power

The nano-colloidal suspension of nanomaterials in a base fluid, typically named a nanofluid, is a promising system that shows interesting properties, such as those related to heat transfer processes. Obtaining nanofluids with high stability is a priority challenge for this kind of system. So, a rationalization of the preparation of nanofluids is clearly needed. Thus, this study presents a methodology based on liquid phase exfoliation that makes it possible to prepare stable nanofluids and control the morphology of the nanostructures, which is defined by the surfactant used. Two stable nanofluids were prepared based on MoS2 nanosheets and MoS2 nanowires and a typical heat transfer fluid (HTF) used in high temperature applications. Periodic-Density Functional Theory (periodic-DFT) calculations were performed to rationalize why different nanostructures were obtained according to the surfactant used. Finally, enhancements in thermal properties were found, being up to 57% for thermal conductivity and up to 7.5% for isobaric specific heat. Therefore, these nanofluids are a promising alternative to the typical HTF used, which is a eutectic mixture of biphenyl and diphenyl oxide. Also, to our knowledge, controlling the nanostructures obtained and the rationalization of the methodology for the preparation of stable nanofluids is reported for the first time. This leads to highly stable nanofluids with improved thermal properties, promising for application in concentrating solar power

Memorias : Coloquio Vida Cotidiana y Diseño

1 archivo PDF (259 páginas)Memorias del coloquio realizado en noviembre de 2007 en las instalaciones de la UAM Azcapotzalco en donde la temática, incluyó investigaciones variadas que iban desde utensilios para comer hasta las librerías y vecindades en el siglo XIX, pasando por el diseño japonés, empaques y embalajes, cooperativas y la España Musulmana, todo esto relacionado con la vida cotidiana ya que dicho concepto está modificando la manera en que los científicos sociales se acercan a la realidad