High Valley Research Articles

Methodology of geotechnical risk analysis for a steep creeping slope at a 160m high valley bridge

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Slight Symmetry Reduction in Thermoelectrics

Thermoelectric research on germanium telluride (GeTe) has been mainly focused on the enhancement of its performance in the high-temperature cubic phase since the 1960s. Recently in Joule, Pei and co-workers achieved an unprecedented thermoelectric figure of merit in rhombohedral-phase GeTe by exploiting slight symmetry breaking in the structure, which simultaneously improved the electronic properties and reduced the lattice thermal conductivity.

Spin and valley filter across line defect in silicene

We propose a new scheme to achieve an effective spin/valley filter in silicene with extended line defect on the basis of spin–valley coupling due to the intrinsic spin-orbit coupling (SOC). The transmission coefficient of the spin/valley states is seriously affected by the SOC. When a perpendicular magnetic field is applied on one side of the line defect, one valley state will experience backscattering, but the other valley will not; this leads to high valley polarization in all transmission directions. Moreover, the spin/valley polarization can be enhanced to 96% with the aid of a perpendicular electric field.

Respuesta de genotipos de avena a la infección por Puccinia graminis f. sp. avenae en Valles Altos de México


 
 
 La roya del tallo de la avena, causada por Puccinia graminis f. sp. avenae, ha aumentado su incidencia y severidad significativamente en parcelas de temporal distribuidas en Valles Altos de México. El objetivo de este estudio fue de determinar la respuesta de 28 genotipos de avena de temporal a la infección por Puccinia graminis f. sp. avenae bajo condiciones de campo, durante los ciclos primavera-verano 2013 y 2014. Se utilizó un diseño experimental completamente al azar con cuatro repeticiones, y un arreglo de tratamientos en parcelas divididas. Las parcelas grandes fueron cinco fechas de siembra y las parcelas chicas estuvieron constituidas por los 28 genotipos de avena. La variable respuesta fue el porcentaje de daño de roya del tallo en cada uno de los genotipos, desde que se inició la enfermedad hasta el término de cada ciclo del cultivo. La variedad de avena más resistente a la roya del tallo fue Diamante R-31, seguida por Nodaway, AB177 y Teporaca. Mientras que las variedades más susceptibles fueron Guelatao, Tulancingo y Ópalo. Asimismo, las fechas de siembra 1 (23 de junio) y 2 (30 de junio) presentaron los menores porcentajes de severidad de la enfermedad. Adicionalmente, se observó que el rendimiento de grano de avena disminuye severamente en presencia de la roya del tallo y sin ser controlada con algún fungicida.
 
 

Floquet high Chern insulators in periodically driven chirally stacked multilayer graphene

Chirally stacked N-layer graphene is a semimetal with ±pN band-touching at two nonequivalent corners in its Brillioun zone. We predict that an off-resonant circularly polarized light (CPL) drives chirally stacked N-layer graphene into a Floquet Chern insulators (FCIs), aka quantum anomalous Hall insulators, with tunable high Chern number CF = ±N and large gaps. A topological phase transition between such a FCI and a valley Hall (VH) insulator with high valley Chern number Cv = ±N induced by a voltage gate can be engineered by the parameters of the CPL and voltage gate. We propose a topological domain wall between the FCI and VH phases, along which perfectly valley-polarized N-channel edge states propagate unidirectionally without backscattering.

Diversity of airborne Cladosporium species isolated from agricultural environments of northern Argentinean Patagonia: molecular characterization and plant pathogenicity

Fungal spores are normal components of external environments. They have been reported to be associated with human, animal and plant diseases causing primary and opportunistic infections. Cladosporium is commonly the most frequently isolated genus from air samples, and its species are considered mainly saprophytic, but there is a wide variety of taxa that can cause adverse effects on human and animal health and also on plants. In this work, we aimed to record Cladosporium spores frequency of isolation in northern Argentinean Patagonia and to perform a molecular characterization based on actin gene complemented with EF1α and ITS genes. The ability of the pathogens to cause disease in pip fruits of Packham’s Triumph and Abate Fetel pears and red delicious apples was determined. Results confirmed Cladosporium spores as the main genera isolated from air samples, and the molecular characterization revealed the existence of 11 species in this region grouped in C. cladosporioides and C. herbarum complexes. Pathogenicity tests revealed that Cladosporium sp. cause disease on fruit. Abate Fetel was the most susceptible to infection. These results compose the first study in Argentina in respect of identification at species level of airborne Cladosporium spores, and furthermore, it is the first report in northern Patagonia and the high valley of Rio Negro productive region. This knowledge can help farmers to take preventive measures in order to avoid biological damage.

Calidad pozolera en poblaciones de maíz Cacahuacintle de los Valles Altos de Puebla, México


 
 
 La raza de maíz Cacahuacintle (MC) está confinada en nichos ecológicos específicos y ha sido mínimamente estudiada a nivel intra-racial en sus aspectos de calidad para pozole, no obstante que su uso culinario específico en la gastronomía mexicana lo ubica como una opción agrícola rentable para los agricultores de los Valles Altos de México. El objetivo del estudio fue identificar poblaciones sobresalientes en calidad para pozole (CPP) en colectas de maíz Cacahuacintle de Valles Altos de Puebla (MCVAP). Se utilizaron poblaciones de MCVAP, poblaciones de MC del Estado de México, y como testigos para calidad, una población de maíz Cónico y otra de maíz Ancho. La caracterización morfológica y física de grano se aplicó en todas las poblaciones; la evaluación de la calidad para pozole, contenido de amilosa y propiedades de formación de pasta (PFP) sólo en poblaciones seleccionadas por forma de grano y en los testigos. La forma de grano predominante fue redondeada globosa (86%), que es la típica del maíz Cacahuacintle. Los valores promedio de las variables físicas del grano en las poblaciones de MC fueron: peso de mil granos de 540.6 g, peso hectolítrico de 60.5 kg hL-1, y color de grano con 83.8% de ref lectancia. El grupo formado por las poblaciones CPue-00473,00 474,00477 y 00487 se consideró como de mejor calidad para pozole, por presentar equilibrio en las variables de calidad consideradas. El contenido de amilosa no mostró correlación significativa con ninguna de las variables tecnológicas analizadas. Sin embargo, el perfil viscoamilográfico mostró una clara diferencia entre los maíces Cacahuacintle y el maíz Ancho.
 
 

Valley dependent transport in graphene L junction

We studied the valley dependent transport in graphene L junctions connecting an armchair lead and a zigzag lead. The junction can be used in valleytronic devices and circuits. Electrons injected from the armchair lead into the junction is not valley polarized, but they can become valley polarized in the zigzag lead. There are Fermi energies, where the current in the zigzag lead is highly valley polarized and the junction is an efficient generator of valley polarized current. The features of the valley polarized current depend sensitively on the widths of the two leads, as well as the number of dimers in the armchair lead, because this number has a sensitive effect on the band structure of the armchair lead. When an external potential is applied to the junction, the energy range with high valley polarization is enlarged enhancing its function as a generator of highly valley polarized current. The scaling behavior found in other graphene devices is also found in L junctions, which means that the results presented here can be extended to junctions with larger dimensions after appropriate scaling of the energy.

Simulación espacial de Claviceps gigantea (Fuentes, de la Isla, Ullstrup y Rodríguez) en el Estado de México

El cultivo de maíz en México es uno de los más importantes destacando los Valles Altos de México, en esta región la principal problemática del cultivo son las enfermedades, principalmente las que originan la pudrición de la mazorca lo que disminuye el rendimiento y representa grandes pérdidas económicas. Una de estas enfermedades es causada por el hongo Claviceps gigantea que comúnmente se conoce como diente de caballo. Esta enfermedad puede invadir toda la mazorca impidiendo la formación de grano.; en los últimos años, las condiciones climáticas han favorecido la proliferación de este hongo en predios cultivados con maíz Zea mays L. El presente trabajo se llevó a cabo en parcelas de una hectárea de cinco municipios del Estado de México, con la incidencia natural del hongo durante tres ciclos de cultivo (2013-2015) usando técnicas geoestadísticas y realizando el proceso de simulación condicionada y no condicionada para predecir el comportamiento espacial de la enfermedad a través del tiempo. Los resultados muestran que las técnicas de simulación usadas para predecir el comportamiento de Claviceps gigantea, son una herramienta eficaz para prevenir las infestaciones producidas por este hongo este tipo de estudio pretende ayudar a la elaboración de programas de manejo integrado.

Interaction microenvironment - Pantoea agglomerans limits maize yield

Pantoea agglomerans has been reported as the cause of chlorotic streaks on maize leaves in the Central High Valleys of México (CVHM), but there are no current data of how the infection of this new pathogen in Mexico affects production and yield of the crop. To understand the development of the disease in the crop, two experiments with a split-plot design and three replications were established during spring-summer 2010 in different microenvironments: Ayapango and Temamatla. Three cultivars of maize (a tri-linear HS2 hybrid, the single-cross hybrid Triunfo and the native Cacahuacintle) were evaluated with three P. agglomerans isolates. In the three maize cultivars, chlorotic streaks appeared on new leaves; at the ripening stage, the symptoms were less perceptible. The average incidence of plants with chlorotic streaks was higher in the town of Temamatla than in Ayapango, and in both microenvironments, the average degree of severity was less than 40%. Isolate A was the most virulent (P < 0.0001) on the three cultivars evaluated. These results will provide the basis for effective management of the disease under environmental conditions similar to those evaluated in this research.

Breeding and Alimentation in the Roman Cisalpina: A First Balance between Archaeology and Zoo-archaeology from High Ground and Valley Floor Villages

The report aims to offer a preliminary framework of knowledge on zoo archaeological topics in the North Eastern Italy during the Roman age through a comparative data analysis from high ground and valley floor villages The purpose is also connecting archaeological and zoo archaeological data with other kind of source if possible The faunistic data show the prevalence of ovine and pigs related to environmental vocation and also political economical and cultural influences in the complex relation among production distribution and consumption

New Record of Chaetasbolisia erysiphoides from Cold Arid Soils of Zanskar (Kargil), India

Zanskar is a high altitude semi-desert valley in Ladakh (30°45'–35°50'N and 75°45'–80°31'E) lying on the northern flank of the Great Himalayan range. This mountain range acts as a climatic barrier protecting Zanskar valley from most of the monsoon, resulting in a warm and dry climate during the six months of summer, with a temperature range of 20–27°C, low humidity and scant precipitation.

Electronic structure and spin/valley transport properties of monolayer MoS2 under the irradiation of the off-resonant circularly polarized light

The new-type monolayer semiconductor material molybdenum disulfide (MoS2) is direct band gap semiconductor with a similar geometrical structure to graphene, and as it owns superior physical features such as spin/valley Hall effect, it should be more excellent than graphene from the viewpoint of device design and applications. The manipulation of the spin and valley transport in MoS2-based device has been an interesting subject in both experimental and theoretical researches. Experimentally, the photoninduced quantum spin and valley Hall effects may result in high on-off speed spin and/or valley switching based on MoS2. Theoretically, the off-resonant electromagnetic field induced Floquet effective energy should modulate effectively the electronic structure, spin/valley Hall conductance as well as the spin/valley polarization of the MoS2, through the virtual photon absorption and/or emission processes. Utilizing the low energy effective Hamilton model from the tight-binding approximation and Kubo linear response theorem, we theoretically investigate the electronic structure and spin/valley transport properties of the monolayer MoS2 under the irradiation of the off-resonant circularly polarized light in the present work. The band gaps around the K and K' point of the Brillouin region for monolayer MoS2 proves to increase linearly and decrease firstly and then increase, respectively with the increase of external off-resonant right-circularly polarized light induced effective coupling energy, and decrease firstly and then increase and increase linearly with the increase of left-circularly polarized light induced effective coupling energy, therefore, the interesting transition of semiconducting-semimetallic-semiconducting may be observable in monolayer MoS2. Furthermore, the spin and valley Hall conductance of the monolayer MoS2 for the case without off-resonant circularly polarized light are 0 and 2e2/h, respectively, and they will convert into -2e2/h and 0 when the absolute value of the off-resonant circularly polarized light induced effective coupling energy is in a range of 0.79-0.87 eV. Finally, the spin polarization for monolayer MoS2 increases up to a largest value and changes from positive to negative and/or negative to positive at the vicinity of the effective coupling energy ±0.79 eV of the off-resonant right/left circularly polarized light, while the valley polarization should increase firstly and then decrease with the off-resonant circularly polarized light, and goes up to 100% in the range of 0.79-0.87 eV of the absolute value for effective coupling energy. Therefore, the external off-resonant circularly polarized electromagnetic field should be an effective means in manipulating the electronic structure, spin/valley Hall conductance and spin/valley polarization of the monolayer MoS2, the two-dimensional MoS2 may be tuned into a brand bandgap material with excellent spin/valley and optoelectrical properties.

Telluriding monolayer MoS2 and WS2 via alkali metal scooter

The conversion of chalcogen atoms to other types in transition metal dichalcogenides has significant advantages for tuning bandgaps and constructing in-plane heterojunctions; however, difficulty arises from the conversion of sulfur or selenium to tellurium atoms owing to the low decomposition temperature of tellurides. Here, we propose the use of sodium for converting monolayer molybdenum disulfide (MoS2) to molybdenum ditelluride (MoTe2) under Te-rich vapors. Sodium easily anchors tellurium and reduces the exchange barrier energy by scooting the tellurium to replace sulfur. The conversion was initiated at the edges and grain boundaries of MoS2, followed by complete conversion in the entire region. By controlling sodium concentration and reaction temperature of monolayer MoS2, we tailored various phases such as semiconducting 2H-MoTe2, metallic 1T′-MoTe2, and 2H-MoS2−xTex alloys. This concept was further extended to WS2. A high valley polarization of ~37% in circularly polarized photoluminescence was obtained in the monolayer WS2−xTex alloy at room temperature.

Optical, electric and magnetic controlled ballistic conductance in monolayer WSe2: the perfect valley and spin polarizations

We study the charge and valley-spin ballistic transport through monolayer (ML) WSe2 potential barrier, of width and height , in the presence of an off-resonant light and ferromagnetic (FM) exchange field. We show that an electric switch is available in WSe2 by increasing beyond the critical value . Due to the band gaps of valley and responding differently to off-resonant light together with the huge spin–orbit coupling (SOC) in WSe2, the perfect valley and spin polarizations are obtained. Interestingly, under the effect of electrostatic potential , the valley polarization can be realized even for a tiny light intensity. Additionally, the FM exchange field can assist significantly the spin polarization in a wider region of light intensity and barrier height plane due to the large shift of spin-up and down bands. More important in our results, the highest valley and spin conductance is near 100% even under the polarized situation. These results demonstrate that WSe2 is a distinguished 2D material for novel spintronics and valleytronics in future.

Supporting farmer-managed irrigation systems in the Shigar valley, Karakorum: Role of the government and Aga Khan Rural Support Programme

Farmer-managed irrigation systems (FMIS) in the high altitude valleys of the Karakorum, Pakistan, continue to be managed effectively despite increased pressure on the social arrangements that sustain them. Colonial era records shows that over a century ago government agencies undertook irrigation support projects. In the past three decades, government agencies and the non-government agency Aga Khan Rural Support Programme (AKRSP), which channels foreign funds into the region, have actively engaged in the provision of irrigation support. This article seeks to explore whether such projects support or undermine farmer-managed irrigation systems and the complex institutional arrangements that underpin them. Field research using ethnographic and participatory methods was conducted in spring 2013 in the upper Shigar valley, Skardu district, Gilgit-Baltistan. The findings show that irrigation development is a political activity that involves village-based actors, religious leaders, local politicians, and government and non-government agencies. Government agencies operate in a largely top-down, engineering mode, their larger projects limited to villages suffering water scarcity. The local government provides small funds for renovation work of FMIS, though allocation of funds is highly politicized. Non-government agencies, for a variety of reasons including donor-funding cycles, apply a one-size-fits-all ‘participatory’ model in an attempt to socially engineer rules and institutions. In communities divided by factionalism the use of such external models that stress formation of committees are unlikely to yield positive results, and could instead contribute to undermining the very systems they seek to support. This research argues that irrigation interventions should take care to build upon the rich and complex social arrangements that have sustained FMIS through the centuries.

Maravilla: Variedad de cebada forrajera para los valles altos de México

Maravilla es una variedad de cebada forrajera obtenida de un cruzamiento múltiple realizado por el Programa Nacional de Cebada del Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP). Maravilla es de hábito de crecimiento de primavera, porte intermedio, presenta tolerancia a las principales enfermedades del cultivo, posee alto rendimiento potencial y su precocidad le permite adaptarse a las condiciones de temporal de los Valles Altos de la Mesa Central de México. Las características químicas del grano de Maravilla representan un importante suministro de nutrientes: la concentración de proteína cruda varía de 10.0 a 14.5%; la concentración de almidón oscila de 61 a 66%; el contenido de minerales promedio es de 3.5%; la fibra cruda promedio es de 3.5%; el extracto etéreo promedio es de 1.83%; el extracto libre de nitrógeno promedio es de 74%; y la digestibilidad de materia seca promedio es de 95%. Respecto al forraje verde, el momento óptimo de corte es cuando el grano se encuentra en etapa de masoso suave, donde el rendimiento es superior a 20 t ha-1; mientras que en materia seca es de 8-12 t ha-1. Maravilla se evaluó en más de 30 sitios experimentales en diferentes ambientes de las regiones productoras de cebada de los Valles Altos durante el periodo de 2012 a 2015. El rendimiento de grano observado fue de 2.1-5.2 t ha-1; similar y en ocasiones superior en 5% al de la variedad de cebada maltera Esmeralda.

Earth surface processes and landscape evolution in the Himalaya: a framework for sustainable development and geohazard mitigation

Abstract Successful sustainable development and geohazard mitigation in the Himalaya requires an understanding of the nature and dynamics of Earth surface processes and landscape evolution. In recent years, geoscience studies of Himalayan environments have been increasing due to better accessibility, modern technologies and the understanding that there is a necessity to determine the nature and predict likely environmental changes that are occurring due to natural and human influences. The Himalaya is one of the most dynamically active tectonic and geomorphic regions on our planet, and it is the most glaciated mountain area outside of the polar realms. The high mountains and deep valleys are a consequence of the continued collision of the Indian and Eurasian continental plates, rapid uplift and intense denudation by glacial, fluvial, landsliding, aeolian and weathering processes. These processes change over time, influenced by topographic development, climate change and humans. Defining the rates and magnitudes of these processes and their interactions is fundamental in developing a framework to quantify, model and predict future changes for geohazard mitigation and sustainable development.

State policies and cereal production: territorial transformations in High Valleys of Mexico

Las políticas implementadas por el Estado mexicano en el sector agrícola se han regido por el modelo económico neoliberal en busca de una mayor productividad y beneficio al comercio internacional, favoreciendo a los cultivos de mayor rentabilidad económica, disminuyendo su intervención en lo referente a granos básicos y pequeña agricultura. Este proceso genera cambios en el tipo y modo de producción y en la relación sociedad-naturaleza. Por lo que, es importante estudiar las transformaciones territoriales a partir de la implementación de políticas en un sector vulnerable como lo es el agrícola. El objetivo del presente trabajo es socializar el efecto de los cambios estructurales, el libre comercio y los programas agrícolas sobre la producción de granos básicos y las principales transformaciones territoriales generadas en México.

Effect of a velocity barrier on the spin- and valley-dependent transport in ferromagnetic silicene

We investigate the transport properties in a ferromagnetic silicene sheet in the presence of a velocity barrier, defining the region in which the Fermi velocity vF is tunable compared to other regions. It is shown that the valley and spin transports could be modulated by a pure velocity barrier. To achieve the high spin and valley polarization more efficiently, a local gate voltage is considered in the velocity barrier region, to induce a on-site potential difference between two sublattices of the silicene sheet. For the Fermi velocity inside the barrier smaller than the other regions, it is found that a velocity barrier induces a strong oscillation in the conductance and the valley and spin polarizations are strongly enhanced. In the opposite case, the valley and spin polarizations are suppressed by the velocity barrier. In particular, there exists a sharp transition of the polarizations by varying the Fermi velocity in this case, which has a potential application in the spin- and valley-polarized devices.