The nature of correlations in the insulating states of twisted bilayer graphene

The recently observed superconductivity in twisted bilayer graphene emerges from insulating states believed to arise from electronic correlations. While there have been many proposals to explain the insulating behaviour, the commensurability at which these states appear suggests that they are Mott insulators. Here we focus on the insulating states with $\pm 2$ electrons or holes with respect to the charge neutrality point. We show that the theoretical expectations for the Mott insulating states are not compatible with the experimentally observed dependence on temperature and magnetic field if, as frequently assumed, only the correlations between electrons on the same site are included. We argue that the inclusion of non-local (inter-site) correlations in the treatment of the Hubbard model can bring the predictions for the magnetic and temperature dependencies of the Mott transition to an agreement with experiments and have consequences for the critical interactions, the size of the gap, and possible pseudogap physics. The importance of the inter-site correlations to explain the experimental observations indicates that the observed insulating gap is not the one between the Hubbard bands and that antiferromagnetic-like correlations play a key role in the Mott transition.Comment: 8 pages (including appendix), 5 figure

Sustainable planning for poor communities: urban design studios as a catalyst for development in Colombia

This chapter addresses the potential role of sustainable urban design studios as catalysts for development in slum communities of the developing world. Understanding urbanisation processes in the developing world is important to our sustainability challenge because most of the world’s population will live in these places. oreover, world urbanisation patterns are both a key problem as well as a primary resource. Urban proximity makes sustainability with density possible, however urbanisation is both energy intensive and destructive to natural resources

Novel Grasses and Legumes Germplam: Advances and Perspectives for Tropical Zones

It has been the aim, in the present article, to bring together as much as possible scientific evidence and experience in new available germplasm for tropical zones. The economic importance of the Brachiaria, Paspalum and Pennisetum grasses is well established. New germplasm has become available since 1980. This paper reviews evaluations of Brachiaria accessions in humid lowlands and savannas of tropical America. The selection criteria need to be revised. Also, it is necessary to expose the new material as early as possible to farmers in order to select new germplasm with high chances of adoption. Within the genus Paspalum, P. dilatatum is possibly the most widespread. It has made a considerable contribution in the past, providing some of the best early season feed. In this paper, new data on P. atratum will be presented. Since 1985 a great effort had been made on Pennisetum. New cultivars are available. The main legumes genera to be discussed are Arachis spp., Calopogonium mucunoides, Centrosema spp., Desmodium spp., Glycine spp., Macroptilium spp., Neonotonia wightii and Stylosanthes spp. On Arachis, a historical perspective of the collection and evaluation in South America as well as a summary of the regional experience on Central America, Australia and United States would be presented. Some preliminary data on the drought tolerance and animal performance is discussed. For more than one hundred accessions evaluated through 1992 until 1997, twenty accessions of A. pintoi are outstanding and deserve further regional evaluation. Calopogonium mucunoides, although not widely used (like any other pasture legume today in tropical America), is the most popular forage legume amongst farmers in Brazil. A collection of 215 accessions was evaluated in the Cerrado ecosystem. A negative relationship between the degree of pilosity and in vitro dry matter digestibility was found. Within the seventeen accessions selected, two of them, CIAT 822 and 20709 were outstanding for their leaf retention during the dry season. Also, Macroptilium, Neonotonia and Stylosanthes, deserve special mention because attempts to develop cultivars from them have been determined and sustained. Finally, there is also an opportunity to search for new alternatives within the new available collection of N. wightii. Three new accessions are promising

Inclusion of [H3PW12O40] and [H4SiW12O40] into a silica gel matrix via "sol-gel" methodology

Indexación: Web of Science; Scopus.Here we report the inclusion of two Keggin Polyoxometalates (POMs), [H3PW12O40] and [H4SiW12O40], into silica gels by integrating them during the preparation of the SiO2 matrix via "sol-gel" methods. Aerogels were produced by supercritical drying of the wet gels impregnated with the POMs, and lyogels were obtained by means of a lyophilization process. These materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared (FT-IR) spectroscopy and thermoanalytical techniques (TGA-DSC). We found that a large fraction of POMs are lost during the aging time, and solvent exchange for lyophilization. However the thermal stability of the bare matrix is modified by the inclusion of POMs. Some aggregates with a high content of POMs were found via SEM-EDX.http://ref.scielo.org/3fg9t

Experiencia sobre una propuesta metodológica y didáctica para la capacitación de profesores de EGB 3 y polimodal

En este trabajo presentamos los resultados obtenidos como consecuencia del dictado de un Curso de Capacitación para Profesores de EGB 3 y Polimodal, llevado a cabo en la Facultad de Ciencias Exactas y Naturales de la Universidad Nacional de La Pampa. Aprovechando las alternativas que ofrece la evolución tecnológica para propiciar cambios en el enfoque de enseñar y aprender matemática, teniendo en cuenta que la informática ocupa un lugar cada vez más importante en nuestra sociedad y resulta de gran utilidad en el campo educativo, les presentamos a los profesores una propuesta metodológica y didáctica complementaria para la enseñanza del tema Resolución Numérica de Ecuaciones Polinómicas. Esta propuesta consiste, básicamente, en utilizar métodos que usualmente no se enseñan en la Escuela de Nivel Polimodal, con el complemento de la computadora como herramienta colaboradora. Estos métodos permitirán que el alumno analice expresiones polinómicas que no tienen solución exacta, que son de orden elevado y, por consiguiente, son difíciles de tratar por medio de los métodos convencionales. Este tipo de expresiones provienen, por lo general, de problemas técnicos o de situaciones problemáticas de la vida real cuyo tratamiento puede motivar al alumno, facilitando de esta manera el proceso de enseñanza-aprendizaje relativo a la Resolución Numérica de Ecuaciones Polinómicas de cualquier orden. La motivación especial que nos condujo a la elaboración y dictado de este Curso fue la de intentar mejorar el proceso de enseñanza-aprendizaje referido a esta temática en los niveles educativos citados anteriormente. Los participantes respondieron activamente a las distintas propuestas de trabajo que se presentaron a lo largo del desarrollo del Curso. Es por ello que podemos concluir que esta experiencia resultó positiva

Software educativo en línea para la enseñanza y el aprendizaje de temas de Cálculo Numérico

En un proyecto de investigación finalizado, se diseñó un software de escritorio para la enseñanza y el aprendizaje del tema Resolución Numérica de Ecuaciones no Lineales, usando el paquete MatLab

Gyriosomus granulipennis Pizarro-Araya & Flores 2004 (Coleoptera: Tenebrionidae): An extreme case to preserve

El archipiélago de Los Choros, conformado por las islas Choros, Damas y Gaviota forma parte de la Reserva Nacional Pingüino de Humboldt y está situado dentro del desierto costero transicional de Chile (25º-32º S). Estudios recientes realizados en el archipiélago dan cuenta de una especie endémica de Tenebrionidae (Coleoptera) de la isla Choros (29º15’ S, 71º32’ O) descripta como Gyriosomus granulipennis Pizarro-Araya & Flores. El objetivo del presente trabajo es evaluar la prioridad de conservación de esta especie en el archipiélago mediante el análisis del Índice de Prioridad de Conservación (CPI), clasifi cación del Ministerio de Medio Ambiente (MMA) de Chile y lista roja de la IUCN. Nuestros resultados sostienen que esta especie puede ser catalogada en categoría En peligro por el índice CPI y Vulnerable según el MMA. Según criterios IUCN esta especie debería ser categorizada con Datos Defi cientes (DD), ya que muchos de los datos necesarios para la clasifi cación son difíciles de obtener para insectos o pueden sobrestimar o subestimar el riesgo de extinción de esta especie. Consideramos importante monitorear la continuidad de esta especie y conservarla a través del hábitat, para lo cual proponemos evitar el acceso a turistas y erradicar el conejo silvestre europeo.The Choros Archipelago includes three islands: Choros, Damas and Gaviota and it is part of The Pingüino de Humboldt National Reserve. These insular ecosystems are within the Chilean transitional coastal (25º-32º S). Prior researches in the archipelago reported a species of Tenebrionidae (Coleoptera) endemic to Choros island (29º15’ S, 71º32’ W) described as Gyriosomus granulipennis Pizarro-Araya & Flores. The objective of this paper is to evaluate the vulnerability of this species in the archipelago through Conservation Priority Index (CPI), Environmental Ministery of Chile (MMA) and Red List of IUCN. We concluded that G. granulipennis is Endangered by CPI index, and Vulnerable by MMA of Chile. Additionally, this species can be classiffi ed with Defi cient Data (DD) by IUCN because many of data are impossible or diffi cult to obtain for insects and can overestimate or underestimate the risk of extinction of this species. We consider important to monitoring the continuity of this species and the protection of habitat, for which we propose not allow access the tourists and eradication of European rabbit.Fil: Pizarro Ayala, Jaime. Universidad de La Serena; ChileFil: Flores, Gustavo Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Vergara, Olivia E.. Universidad de Concepción; Chil

Phytoplankton patchiness in two shallow waterbodies

The hydrodynamic behaviour in lentic ecosystems is closely related with the spatial and temporal evolution of their physical, chemical and biological characteristics. Because of this, and in order to improve our present knowledge on the limnological dynamics of such ecosystems, a coupled analysis on the relationship between the biological patterns and the governing hydrodynamics mechanisms it is necessary. This paper uses both field analysis and numerical simulation to describe the links between the water movements and the phytoplankton spatial distribution on two shallow waterbodies in the South of Spain: Alhama de Granada Reservoir (Granada) and Laguna Nueva de la Albufera de Adra (Almería). In both systems the observed phytoplankton spatial distribution exhibited dynamic patterns forced by hydrodynamical transport processes. The knowledge of this physical-biological coupling could be useful to outline the basic guidelines for water quality management.Los ecosistemas acuáticos leníticos se caracterizan por un intenso acoplamiento entre los mecanismos de transporte hidrodinámico que en ellos ocurren y la evolución espacial y temporal de sus principales variables físico-químicas y biológicas. En consecuencia y con el objetivo de mejorar nuestro entendimiento sobre la dinámica limnológica de este tipo de sistemas, resulta necesario el desarrollo de análisis interdisciplinares que profundicen en esta estrecha relación hidrodinámica-biología. En este trabajo se analiza, a partir de estudios de campo y simulaciones numéricas, el acoplamiento entre el movimiento de la masa fluida a nivel de macroescala y la distribución espacial del fitoplancton en dos ecosistemas acuáticos someros del Sur de España : el embalse de Alhama de Granada (Granada) y la Laguna Nueva de la Albufera de Adra (Almería). En ambos sistemas se han encontrado patrones dinámicos de distribución espacial de las microalgas, íntimamente relacionados con la dinámica de la masa de agua. El conocimiento de este acoplamiento resulta útil en la definición de líneas básicas para la adecuada gestión de la calidad del agua

The role peer responses to adolescent expression of emotions plays in their emotion regulation : A systematic literature review

Introduction Peer responses to adolescents’ emotional expressions (PREE), are thought to influence the continued development of emotion regulation (ER). Unsupportive (e.g., dismissive) PREE, for example, are expected to be associated with greater maladaptive ER. Poor ER is known to place adolescents at risk of psychopathology. The aim of this systematic review was to collate and synthesize the emerging evidence exploring the role that peer emotion socialization, specifically PREE, plays in adolescent ER and identify future directions. Methods In adherence with PRISMA guidelines, PsychINFO, Medline Complete, CINAHL Complete, Scopus and Web of Science were searched on April 20th, 2021, May 28th, 2022, and April 12th, 2023 for English language reports published after 1998. To be included, studies needed to report on PREE and its relation to adolescent ER. Results A total of eight studies, one qualitative and seven quantitative, met inclusion criteria and had a combined N of 785 participants (aged 10–18 years). Studies were primarily undertaken in the US and mostly included males and females, with one study only including female participants. Conclusions Although only eight studies were identified, the review identified preliminary evidence for an association between PREE and ER in adolescents. This association appeared to vary depending on adolescent gender, age, the closeness of the friendship and the PREE. Several limitations were identified, and suggestions are made for future research in this emerging area