Propuesta de diseño de un sistema de telefonía móvil HSPA en el departamento de Matagalpa.

El presente trabajo consta de una propuesta de diseño de un sistema de telefonía móvil HSPA en el departamento de Matagalpa, además presenta un análisis que se realizó con el apoyo de herramientas de software ATOLL, que mediante la simulación permite realizar una emigración de datos a google earth

Dibenzothiophene adsorption at boron doped carbon nanoribbons studied within density functional theory

"The adsorption of dibenzothiophene (DBT) on bare and boron-doped armchair carbon nanoribbons (ACNRs) is being investigated in the framework of the density functional theory by implementing periodic boundary conditions that include corrections from dispersion interactions. The reactivity of the ACNRs is characterized by using the Fukui functions as well as the electrostatic potential as local descriptors. Non-covalent adsorption mechanism is found when using the local Perdew-Becke-Ernzerhof functional, regardless of the DBT orientation and adsorption location. The dispersion interactions addition is a milestone to describe the adsorption process. The charge defects introduced in small number (i.e., by doping with B atoms), within the ACNRs increases the selectivity towards sulfur mainly due to the charge depletion at B sites. The DBT magnitude in the adsorption energy shows non-covalent interactions. As a consequence, the configurations where the DBT is adsorbed on a BC3 island increase the adsorption energy compared to random B arrangements. The stability of these configurations can be explained satisfactorily in terms of dipole interactions. Nevertheless, from the charge-density difference analysis and the weak Bader charge-distribution interactions cannot be ruled out completely. This is why the electronic properties of the ribbons are analyzed in order to elucidate the key role played by the B and DBT states in the adsorbed configurations.

Effect of packing on the cohesive and electronic properties of methanofullerene crystals

"The crystal structure, cohesive energy, and electronic properties of bulk phases of the fullerene derivative [6, 6]-phenyl-C(61)-butyric-acid-methyl-ester (PCBM) have been calculated using ab initio density-functional theory (DFT) techniques. We have only considered cubic and hexagonal crystal lattices with one PCBM molecule per primitive cell. It was found that the cohesive properties of these systems are determined mainly by two types of mechanisms, namely, the van der Waals interaction and the formation of weak hydrogen bonds. Among the considered crystal structures, the most stable one, which is also the most compact structure, is the simple cubic which has a cohesive energy difference of 1.27 eV with respect to the isolated PCBM molecule. Regarding the electronic properties, the simple-cubic PCBM crystal is found to be a semiconductor with an indirect band gap of 1.21 eV. In addition, we have also investigated the electronic contribution of the phenyl-butyric-acid-methyl-ester tail to the electronic states of the entire system. By analyzing the projected density of states (DOS), we found that the states introduced by the tail are too far from the valence and conduction bands, so that the reduction of the band gap of bulk PCBM compared to PCBM molecule results only from the close packing. In addition, the tail introduces a splitting of the degenerate states of the molecule reducing the gap by about 0.2 eV compared to the C(60) molecule. On the other hand, it is shown that the simple hexagonal structure presents a layered structure with the separation between layers of 12.6 angstrom. Furthermore, in the cohesive curve, there is a nonvanishing cohesive energy for noninteracting layers. The study of the hexagonal monolayers shows a stable structure with a cohesive energy of 0.72 eV, which indicates that PCBM can form two-dimensional systems when the PCBM molecules are deposited on the appropriate substrates. The results provided by this work may be important to improve our understanding concerning the mechanisms of formation of PCBM supramolecular structures, and how they can be modified to reach a desired particular property.

Quantitative trait locus mapping associated with earliness and fruit weight in tomato

The flowering time is regarded as an important factor that affects yield in various crops. In order to understand how the molecular basis controlling main components of earliness in tomato (Solanum lycopersicum L.), and to deduce whether the correlation between fruit weight, days to flowering and seed weight, is caused by pleiotropic effects or genetic linkage, a QTLs analysis was carried out using an F2 interspecific population derived from the cross of S. lycopersicum and S. pimpinellifolium. The analysis revealed that most of the components related to earliness were independent due to the absence of phenotypic correlation and lack of co-localization of their QTLs. QTLs affecting the flowering time showed considerable variation over time in values of explained phenotypic variation and average effects, which suggested dominance becomes more evident over time. The path analysis showed that traits such as days to flowering, seed weight, and length of the first leaf had a significant effect on the expression of fruit weight, confirming that their correlations were due to linkage. This result was also confirmed in two genomic regions located on chromosomes 1 and 4, where despite showing high co-localization of QTLs associated to days to flowering, seed weight and fruit weight, the presence and absence of epistasis in dfft1.1 × dftt4.1 and fw1.1 × fw4.1, suggested that the linkage was the main cause of the co-localization

Solar photovoltaic technology in isolated rural communities in Latin America and the Caribbean

The main characteristics of photovoltaic (PV) energy and its current development in Latin American and Caribbean countries (LAC); its impact on the electrification of homes, health institutions, and schools in isolated or difficult-to-access communities; and, the advantages thereof are presented and discussed by replacing the use of traditional fuels such as firewood and kerosene in order to improve inhabitants ’health as well as reducing CO2 emissions. Countries like Nicaragua, Peru, Brazil, Argentina, and Chile stand out for their growing PV energy development in the region. A case study of the electrification process by PV systems shows very positive changes are manifested in terms of improving the quality of life of the inhabitants, and especially their physical and mental health state. In addition, CO2 emission reductions from electrifying 216 houses in the nine communities reach an annual amount of 2,164.19 t/yr, reducing firewood consumption by 2,123.39 t/yr and kerosene consumption by 40.80 t/yr However, LAC countries must adopt laws and regulations that regulate the use of PV energy, with an emphasis on recycling systems at the end of their life cycle

Atomic surface segregation and structural characterization of PdPt bimetallic nanoparticles

"Bimetallic nanoparticles are of interest since they lead to many interesting electrical, chemical, catalytic, and optical properties. They are particularly important in the field of catalysis since they show superior catalytic properties than their monometallic counterparts. The structures of bimetallic nanoparticles depend mainly on the synthesis conditions and the miscibility of the two components. In this work, PdPt alloyed-bimetallic nanoparticles (NPs) were synthesized through the polyol method, and characterized using spherical aberration (Cs) corrected scanning transmission electron microscopy (STEM). High-angle annular dark-field (HAADF)-STEM images of bimetallic nanoparticles were obtained. The contrast of images shows that nanoparticles have an alloy structure with an average size of 8.2 nm. Together with the characterization of nanoparticles, a systematic molecular dynamics simulations study focused on the structural stability and atomic surface segregation trends in 923-atom PdPt alloyed-bimetallic NPs was carried out.

Conservation and Use of Latin American Maize Diversity: Pillar of Nutrition Security and Cultural Heritage of Humanity

Latin America is the center of domestication and diversity of maize, the second most cultivated crop worldwide. In this region, maize landraces are fundamental for food security, livelihoods, and culture. Nevertheless, genetic erosion (i.e., the loss of genetic diversity and variation in a crop) threatens the continued cultivation and in situ conservation of landrace diversity that is crucial to climate change adaptation and diverse uses of maize. We provide an overview of maize diversity in Latin America before discussing factors associated with persistence of large in situ maize diversity, causes for maize landrace abandonment by farmers, and strategies to enhance the cultivation of landraces. Among other factors, maize diversity is linked with: (1) small-holder farming, (2) the production of traditional food products, (3) traditional cropping systems, (4) cultivation in marginal areas, and (5) retention of control over the production system by the farmers. On the other hand, genetic erosion is associated with substitution of landraces with hybrid varieties or cash crops, and partial (off-farm labor) or complete migration to urban areas. Continued cultivation, and therefore on-farm conservation of genetic diversity held in maize landraces, can be encouraged by creating or strengthening market opportunities that make the cultivation of landraces and open pollinated varieties (OPVs) more profitable for farmers, supporting breeding programs that prioritize improvement of landraces and their special traits, and increasing the access to quality germplasm of landraces and landrace-derived OPVs

Clima organizacional y sensibilidad a la crítica de alumnos de la facultad de psicología de una universidad pública de Lima

This communication reports the adaptation and relationship between the scale of organizational climate and sensitivity to criticism on 338 students of undergraduate, of which 140 are male and 198 female of the faculty of psychology of public university of Lima. Organizational climate scale was finally restructured into four factors: a) factor 1: negative attitude towards the organization (19 items), b) factor 2: quality of work (8 items), c) factor 3: institutional image (4 items), and d) factor 4: competition authority (6 items); while the scale of sensitivity to criticism maintained its very structure. The results arrogated the lack of relationship between organizational climate and sensitivity to criticism, in the same way sex and age does not make a difference with these.La presente comunicación reporta la adaptación y la relación entre la escala de clima organizacional y la sensibilidad a la crítica en 338 alumnos de pregrado, de los cuales 140 son del sexo masculino y 198 del femenino de la facultad de psicología de una universidad pública de Lima. Para ello, la escala de clima organizacional finalmente quedó reestructurada en cuatro factores: a) factor 1: actitud negativa hacia la organización (19 ítems), b) factor 2: calidad en el trabajo (8 ítems), c) factor 3: imagen institucional (4 ítems), y d) factor 4: competencia de la autoridad (6 ítems); mientras que la escala de sensibilidad a la crítica mantuvo su misma estructura. Así, los resultados arrogaron la falta de relación entre el clima organizacional y la sensibilidad a la crítica; de la misma manera, el sexo y la edad no marcaron la diferencia con estas

Anafilaxia en niños y adultos: prevención, diagnóstico y tratamiento

La anafilaxia es una condición que requiere asistencia inmediata para su resolución, se puede presentar en diferentes entornos: consultorio, hospital, escuela, hogar o en algún otro espacio público. La información aquí contenida forma parte de lineamientos conocidos sobre prevención, diagnóstico y tratamiento. Se abordan aspectos epidemiológicos, desencadenantes, factores de riesgo y cofactores; se explican de una manera didáctica los mecanismos fisiopatológicos que se traducen en fenotipos de presentación. Se enfatiza el diagnóstico clínico con base en criterios ya establecidos, se mencionan clasificaciones para evaluar la gravedad de la reacción, así como el rol de las pruebas clínicas o de laboratorio. Como aspectos de relevancia, se abordan el tratamiento de primera elección con adrenalina, instrucciones sobre autoinyectores y diferentes elementos para el tratamiento complementario y de segunda elección. También se refieren aspectos a considerar al dar de alta a un paciente y medidas de seguimiento, con un énfasis preventivo en la comunidad. Finalmente, se menciona el abordaje en el consultorio de alergia para decidir sobre opciones de inmunomodulación. ABSTRACT Anaphylaxis is a condition that requires immediate assistance for its resolution, it can occur in different settings: office, hospital, school, home or some other public space. The information contained herein forms part of known guidelines on prevention, diagnosis and treatment. Epidemiological aspects, triggers, risk factors and co-factors are addressed; physiopathological mechanisms that are translated into presentation phenotypes are explained in a didactic way. Clinical diagnosis is emphasized based on established criteria, classifications are mentioned to evaluate the severity of the reaction, as well as the role of clinical or laboratory tests. As relevant aspects, the first choice treatment with adrenaline, instructions on auto-injectors and different elements for the complementary and second choice treatment are dealt with. They also refer to aspects to consider when discharging a patient and followup measures, with a preventive emphasis on the community. Finally, the allergy clinic approach to deciding on immunomodulation options is mentione

Lo glocal y el turismo. Nuevos paradigmas de interpretación.

El estudio del turismo se realiza desde múltiples escalas y enfoques, este libro aborda muchos temas que es necesario discutir desde diversas perspectivas; es el caso de la reflexión sobre la propia disciplina y sus conceptos, así como los asuntos específicos referidos al impacto territorial, los tipos de turismo, las cuestiones ambientales, el tema de la pobreza, la competitividad, las políticas públicas, el papel de las universidades, las áreas naturales protegidas, la sustentabilidad, la cultura, el desarrollo, la seguridad, todos temas centrales documentados y expuestos con originalidad y dominio del asunto. Lo multiescalar es básico para la comprensión del sistema turístico, sistema formado de procesos globales, regionales y locales. El eje de discusión del libro es lo glocal, esa interacción entre lo nacional y local con lo global