Theoretical description of phase coexistence in model C60

We have investigated the phase diagram of the Girifalco model of C60 fullerene in the framework provided by the MHNC and the SCOZA liquid state theories, and by a Perturbation Theory (PT), for the free energy of the solid phase. We present an extended assessment of such theories as set against a recent Monte Carlo study of the same model [D. Costa et al, J. Chem. Phys. 118:304 (2003)]. We have compared the theoretical predictions with the corresponding simulation results for several thermodynamic properties. Then we have determined the phase diagram of the model, by using either the SCOZA, or the MHNC, or the PT predictions for one of the coexisting phases, and the simulation data for the other phase, in order to separately ascertain the accuracy of each theory. It turns out that the overall appearance of the phase portrait is reproduced fairly well by all theories, with remarkable accuracy as for the melting line and the solid-vapor equilibrium. The MHNC and SCOZA results for the liquid-vapor coexistence, as well as for the corresponding critical points, are quite accurate. All results are discussed in terms of the basic assumptions underlying each theory. We have selected the MHNC for the fluid and the first-order PT for the solid phase, as the most accurate tools to investigate the phase behavior of the model in terms of purely theoretical approaches. The overall results appear as a robust benchmark for further theoretical investigations on higher order C(n>60) fullerenes, as well as on other fullerene-related materials, whose description can be based on a modelization similar to that adopted in this work.Comment: RevTeX4, 15 pages, 7 figures; submitted to Phys. Rev.

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time, and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space. While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes, vast areas of the tropics remain understudied. In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity, but it remains among the least known forests in America and is often underrepresented in biodiversity databases. To worsen this situation, human-induced modifications may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge, it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Surface Modification Of Pdms Microchips With Poly(ethylene Glycol) Derivatives For μtas Applications

In this work is presented a method for the modification of native PDMS surface in order to improve its applicability as a substrate for microfluidic devices, especially in the analysis of nonpolar analytes. Therefore, poly(ethylene glycol) divinyl ether modified PDMS substrate was obtained by surface modification of native PDMS. The modified substrate was characterized by attenuated total reflectance infrared spectroscopy, water contact angle measurements, and by evaluating the adsorption of rhodamine B and the magnitude of the EOF mobility. The reaction was confirmed by the spectroscopic evaluation. The formation of a well-spread water film over the surface immediately after the modification was an indicative of the modified surface hydrophilicity. This characteristic was maintained for approximately ten days, with a gradual return to a hydrophobic state. Fluorescence assays showed that the nonpolar adsorption property of PDMS was significantly decreased. 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Valores ecobiométricos e índice de resistividade da artéria oftálmica externa em catetos (Tayassu tajacu, Linnaeus, 1758)

RESUMO Foram avaliados ultrassonograficamente, pela via transpalpebral, 28 bulbos oculares de 14 catetos adultos, através de técnica padronizada pelo operador. Adicionalmente foi realizado o estudo hemodinâmico da artéria oftálmica externa pela técnica de Doppler colorido. Os dados coletados foram analisados estatisticamente pelo programa Bioestat 5.0 for Windows, adotando-se 5% de significância. Com a metodologia empregada, obtiveram-se os seguintes valores para os globos oculares direito e esquerdo, respectivamente D1: 1,72 ± 0,29mm e 1,76 ± 0,40mm; D2: 9,95 ± 1,08mm e 10,6 ± 0,99mm; D3: 7,42 ± 0,93mm e 7,45 ± 0,72mm e D4: 17,6 ± 0,78mm e 17,8 ± 0,59mm. Os valores médios do índice de resistividade da artéria oftálmica externa foram 0,435 ± 0,02 e 0,448 ± 0,02 (globos oculares direito e esquerdo, respectivamente). Não houve diferença estatística quanto aos antímeros oculares em nenhum dos parâmetros estudados. Conclui-se que a ecobiometria ocular e a Dopplerfluxometria da artéria oftálmica na espécie Tayassu tajacu é executável e reprodutível, desde que haja domínio do examinador em relação à anatomia e à técnica adequada. Os valores inferidos neste estudo servem de referência para médicos veterinários no diagnóstico de doenças oculares.</jats:p