Poly-dodecahedrane: A new allotrope of carbon

Carbon is the most important chemical element and the theoretical study of its new allotropes can be of great interest. In this study, regular dodecahedron (dodecahedrane) oligomers (n = 1, 3, 5, 7, 9, 11, 13) by extending the dodecahedrane units in 3-dimensions were designed. Then, a theoretical study was conducted on their structures and electronic properties as potential new carbon allotrope. The cohesive energy (Ecoh) and $\Delta$G, were calculated. Experimental observations indicate that the Ecoh rises as the number of dodecahedrane units increases, whereas the Gibbs free energy change $\Delta$G decreases with an increase in the number of dodecahedrane units. The HOMO-LUMO energy gap (Eg) values, which represent electronic properties, decrease with increasing number of dodecahedrane units. Density functional theory (DFT) calculations of the novel carbon allotropes polydodecahedrane nanostructures have unveiled a previously unobserved symmetry, indicating intrinsic metallic behavior. The symmetrical distribution of partial charges was found in molecular electrostatic potential (MEP) diagrams for all oligomers, showing a tendency of the structures to maintain a symmetrical structural order as the number of monomer units increases. In addition, natural bond orbital (NBO) analysis of 13-units oligomer as largest designed structure reveals near-$sp^3$ hybridization for different carbons. Based on the calculated results, the structures have a tendency to extend in 3-dimensions and form a covalent network of poly-dodecahedrane with a unique structure consisting of interconnected cyclopentane rings. The results show that this exclusive configuration exhibits theoretical stability and suggests the potential for poly-dodecahedrane to be regarded as a novel carbon allotrope

Geoprocessing for the characterization of soils developed from basalt and sand material

Os levantamentos de solos são na maioria antigos e pouco detalhados, geralmente nos níveis exploratório e de reconhecimento. Isso pode ser explicado pelo fato de que o método tradicional de levantamento de solos é lento e caro, requerendo grande número de observações de campo. Assim, o presente trabalho teve como objetivo caracterizar unidades de mapeamento de solos das regiões de Ibaté e São Carlos, SP, desenvolvidos de materiais basálticos e areníticos em função da declividade e altitudes correspondentes, com base em modelo digital de elevação (MDE). Primeiramente, foi feito um mapa de solos semidetalhado pelo método tradicional. Posteriormente, utilizando-se curvas de nível da região, foi elaborado o MDE, do qual foram extraídos mapas com diferentes classes de declividade e elevação. Por meio da tabulação cruzada, foi determinada a incidência de cada solo nas respectivas classes de declives e altitudes. Cada solo apresentou comportamento diferenciado em relação às classes de declive. Contudo, nas faixas limítrofes de declividade pode ocorrer sobreposição de dois ou mais solos. Na referida região, o Latossolo Amarelo encontra-se predominantemente nas regiões mais altas e de relevo plano; entretanto, solos pouco intemperizados, como os Neossolos Litólicos, aparecem em diferentes faixas de declividade. Conclui-se que o conhecimento da distribuição dos solos no relevo é de grande importância, pois facilita a execução do levantamento de solos. O modelo de elevação apresenta semelhanças com o mapa de solos, podendo auxiliar na sua determinação. As variações de solo, no entanto, são mais complexas, não dispensando as observações de campo.Brazilian soil surveys are mostly outdated, with few details, usually based on discovery and recognition. This fact can be ascribed to the traditional, slow and expensive soil survey method, requiring a great number of field observations. Thus, faster and cheaper soil mapping techniques must be developed. The objective of this study was to characterize soil mapping units in the region of Ibaté and São Carlos, state of São Paulo, measuring slopes and altitudes, based on a digital elevation model (DEM). First a semi-detailed soil map was drawn based on the traditional methodology. Then, the DEM was elaborated using contour lines of the region, from which maps with different slope and elevation classes were extracted. By cross tabulation each soil was determined in each slope and elevation class. Each soil responded differently in relation to the slope classes. However, an overlapping of two or more soils can occur in the limit ranges. In the study area, the Typic Haplustox can be found predominantly in higher and plain areas. Low weathered soils such as the Typic Udorthent are however found at different slope levels. It was concluded that knowledge on the soil distribution in the relief is very important for soil surveys. The DEM have similarities with the soil map and can contribute with some information. Soil variations are however extremely complex, which makes field observations indispensable

First-principles calculations of the electronic and optical properties of penta-graphene monolayer: study of many-body effects

In the present work, first-principles calculations based on the density functional theory (DFT), GW approximation and Bethe-Salpeter equation (BSE) are performed to study the electronic and optical properties of penta-graphene (PG) monolayer. The results indicated that PG is a semiconductor with an indirect band gap of approximately 2.32 eV at the DFT- GGA level. We found that the utilization of the GW approximation based on many-body perturbation theory led to an increase in the band gap, resulting in a quasi-direct gap of 5.35 eV. Additionally, we employed the G0W0 - RP A and G0W0 - BSE approximations to calculate the optical spectra in the absence and in the presence of electron-hole interaction, respectively. The results demonstrated that the inclusion of electron-hole interaction caused a red-shift of the absorption spectrum towards lower energies compared to the spectrum obtained from the G0W0 - RP A approximation. With the electron-hole interaction, it is found that the optical absorption spectra are dominated by the first bound exciton with a significant binding energy 3.07 eV. The study concluded that the PG monolayer, with a wider band gap and enhanced excitonic effects, holds promise as a suitable candidate for the design and fabrication of optoelectronic components

Nuevos datos sobre la sucesión del "CXG" (Grupo das Beiras) : evidencia sedimentaria del origen glacioderivado de las facies conglomeráticas de la FM. del Cabeço das Popas, en la región de Monfortinho (Portugal Central)

La presencia de "dropstones" en las facies finas laminadas que se intercalan entre los orto y paraconglomerados característicos de la Fm. del Cabeço das opas (CXG: Grupo das Beiras), prueba su origen glacioderivado. La edad véndica media-superior considerada para esta Fm. permite postular la existencia de episodios glaciares postvarangerienses en el Macizo Hespérico

Topological field theories in n-dimensional spacetimes and Cartan's equations

Action principles of the BF type for diffeomorphism invariant topological field theories living in n-dimensional spacetime manifolds are presented. Their construction is inspired by Cuesta and Montesinos' recent paper where Cartan's first and second structure equations together with first and second Bianchi identities are treated as the equations of motion for a field theory. In opposition to that paper, the current approach involves also auxiliary fields and holds for arbitrary n-dimensional spacetimes. Dirac's canonical analysis for the actions is detailedly carried out in the generic case and it is shown that these action principles define topological field theories, as mentioned. The current formalism is a generic framework to construct geometric theories with local degrees of freedom by introducing additional constraints on the various fields involved that destroy the topological character of the original theory. The latter idea is implemented in two-dimensional spacetimes where gravity coupled to matter fields is constructed out, which has indeed local excitations.Comment: LaTeX file, no figure

Latinamerican guidelines of RIICER for diagnosis of tick-borne rickettsioses

Las rickettsiosis transmitidas por garrapatas son afecciones de distribución mundial, que por diferentes motivos se pueden considerar emergentes y reemergentes. Hasta hace escasos años la única rickettsiosis transmitida por garrapatas en Latinoamérica era la infección por Rickettsia rickettsii, pero en la actualidad y fundamentalmente, gracias a la incorporación de nuevas herramientas para el diagnóstico microbiológico como la reacción en cadena de la polimerasa y secuenciación o el cultivo celular rápido en tubo cerrado, se han descrito e involucrado otras especies de Rickettsia en la producción de patología humana. En estas guías se detallan y describen las diferentes técnicas utilizadas para el diagnóstico microbiológico de las rickettsiosis. Además, se incluye una sección en la que se detallan las especies más importantes de garrapatas duras relacionadas con las rickettsiosis en Latinoamérica, con claves para su clasificación taxonómica.Tick-borne rickettsioses are worldwide infectious diseases that are considered emerging and re-emerging. Until recently the only tick-borne rickettsiosis present in Latin America was Rickettsia rickettsii infection, but to date, with the incorporation of new tools as PCR and sequencing and the quick cellular close tube cultures (Shell-vial), new species has been involved as human pathogens. In these guidelines, we offer an update of the microbiological assays for diagnosing rickettsioses. Besides we have included a section in which the most important hard ticks involved in human rickettsioses in Latinoamerica are detailed.Financiamiento: RIICER (Red Iberoamericana para la Investigación y Control de las Enfermedades Rickettsiales) del Programa Iberoamericano de Ciencia y Tecnología para el Desarrollo (CYTED)

Risco de Diabetes Mellitus numa população escolar

A Diabetes Mellitus (DM) é uma doença crónica que apresenta como principais factores de risco: obesidade, gordura abdominal e história familiar. Para avaliar o risco de desenvolver DM tipo 2 dentro de 10 anos aplicou-se uma ficha de avaliação onde se verificou que 12,5% apresentam risco sensivelmente elevado e 3,6% risco moderado. No entanto esta população já apresenta alguns factores de risco tais como IMC elevado, perímetro abdominal aumentado ou muito aumentado, baixa actividade física, alimentação deficiente em vegetais e frutas e antecedentes familiares com DM.Diabetes Mellitus (DM) is a chronic disease that presents as main risk factors: obesity, abdominal fat and family history. To assess the risk of developing type 2 diabetes within 10 years was applied an evaluation and it was found that 12.5% have significantly elevated risk and 3.6% moderate risk. However, this population already has some risk factors such as high BMI, waist circumference increased or greatly increased, low physical activity, diet deficient in fruits and vegetables and family history of DM

Aprendendo com o insucesso: um estudo de caso de aplicação da resolução criativa de problemas ao projeto educativo

O Projeto Educativo, como instrumento fundamental para a autonomia das escolas, em Portugal, deve aglutinar as principais expectativas da comunidade escolar, implicando rigor na metodologia de investigação, utilizada para sua elaboração, e na implementação da mudança requerida. O presente artigo relata a forma como foi possível obter esses aspectos, numa escola secundária, ao longo de mais de um ano, por meio do uso do método de Resolução Criativa de Problemas, que envolveu toda a comunidade escolar. Conforme o planeamento definido, a elaboração do Projeto Educativo seguiu os passos de um trabalho de investigação e resultou num documento estratégico e operacional, sujeito, posteriormente, a várias tentativas de implementação que, no entanto, tiveram apenas sucesso relativo. A discussão das condições necessárias para que o documento final possa servir de base à implementação das políticas e ações definidas, o que simplificaria todo o esquema de funcionamento escolar, sob um prisma de gestão efetiva das organizações, é aqui iniciada e sugerida para futuras investigações