Lattice thermal expansion and anisotropic displacements in urea, bromomalonic aldehyde, pentachloropyridine and naphthalene

Anisotropic displacement parameters (ADPs) are commonly used in crystallography, chemistry and related fields to describe and quantify thermal motion of atoms. Within the very recent years, these ADPs have become predictable by lattice dynamics in combination with first-principles theory. Here, we study four very different molecular crystals, namely urea, bromomalonic aldehyde, pentachloropyridine, and naphthalene, by first-principles theory to assess the quality of ADPs calculated in the quasi-harmonic approximation. In addition, we predict both thermal expansion and thermal motion within the quasi-harmonic approximation and compare the predictions with experimental data. Very reliable ADPs are calculated within the quasi-harmonic approximation for all four cases up to at least 200 K, and they turn out to be in better agreement with experiment than the harmonic ones. In one particular case, ADPs can even reliably be predicted up to room temperature. Our results also hint at the importance of normal-mode anharmonicity in the calculation of ADPs

Glass fracture surface energy calculated from crystal structure and bond-energy data

We present a novel method to predict the fracture surface energy of oxide glasses, {\gamma}, using readily available crystallographic structure data of their isochemical crystal and tabled diatomic chemical bond energies, D0. The method assumes that {\gamma} equals the fracture surface energy of the most likely cleavage plane of the crystal. Calculated values were in excellent agreement with those calculated from measured glass density and D0 in an earlier work. This finding demonstrates a remarkable equivalence between crystal cleavage planes and glass fracture surfaces

Comparison of the NEI-VFQ and OSDI questionnaires in patients with Sjögren's syndrome-related dry eye

BACKGROUND: To examine the associations between vision-targeted health-related quality of life (VT-HRQ) and ocular surface parameters in patients with Sjögren's syndrome, a systemic autoimmune disease characterized by dry eye and dry mouth. METHODS: Forty-two patients fulfilling European / American diagnostic criteria for Sjögren's syndrome underwent Schirmer testing without anesthesia, ocular surface vital dye staining; and measurement of tear film breakup time (TBUT). Subjects were administered the Ocular Surface Disease Index (OSDI) and the 25-item National Eye Institute Vision Functioning Questionnaire (NEI-VFQ). Main outcome measures included ocular surface parameters, OSDI subscales describing ocular discomfort (OSDI-symptoms), vision-related function (OSDI-function), and environmental triggers, and NEI-VFQ subscales. RESULTS: Participants (aged 31–81 y; 95% female) all had moderate to severe dry eye. Associations of OSDI subscales with the ocular parameters were modest (Spearman r (ρ) < 0.22) and not statistically significant. Associations of NEI-VFQ subscales with the ocular parameters reached borderline significance for the near vision subscale with TBUT (ρ = 0.32, p = .05) and for the distance vision subscale with van Bijsterveld score (ρ = 0.33, p = .04). The strongest associations of the two questionnaires were for: ocular pain and mental function with OSDI-symptoms (ρ = 0.60 and 0.45, respectively); and general vision, ocular pain, mental function, role function, and driving with OSDI-function (ρ = 0.60, 0.50, 0.61, 0.64, 0.57, and 0.67, respectively). CONCLUSIONS: Associations between conventional objective measures of dry eye and VT-HRQ were modest. The generic NEI-VFQ was similar to the disease-specific OSDI in its ability to measure the impact of Sjögren's syndrome-related dry eye on VT-HRQ

Efecto tóxico del cobre en poblaciones naturales de picoplancton aisladas, procedentes de distintas localizaciónes geográficas

9 páginas, 9 figuras, 2 tablas.[EN] In an approach to understand more about copper toxicity effects on marine microalgae, 72-h growth inhibition toxicity tests were followed on natural picophytoplanktonic populations belonging to different coastal and oceanic geographic locations (Mediterranean Sea and Atlantic Ocean) covering, at an approximate longitude of 30ºW, latitudes from 32º14´S to 29º10´N. Analyses of samples established different predominant populations for different locations. Copper toxicity tests showed a group of cyanobacteria isolated from coastal samples that were the most sensitive, and a second group of picoeukaryotes collected from the Atlantic Ocean surface, which were more tolerant to copper. The use of flow cytometry for studying copper toxic effects provided a variety of information on cell parameters in addition to cellular density. In particular, an established increase in copper tolerance with increase of cell size was observed in cyanobacteria, but it was not clearly followed in picoeukaryotes. This study aims to relate copper tolerance to the geographic location sites of sampling collection. The results obtained establish that other factors such as cell size, proximity to the coast and copper concentration in situ are considered to have a greater influence than the fact of belonging to a determined location site.[ES] Con el fin de estudiar el efecto tóxico del cobre en las microalgas marinas, se llevaron a cabo ensayos de toxicidad (72 h) con poblaciones naturales de picofitoplancton. Poblaciones procedentes de distintas localizaciones geográficas (mar Mediterráneo y océano Atlántico), cubriendo, aproximadamente en la longitud de 30ºO, latitudes comprendidas entre 32º14´S y 29º10´N. El análisis inicial de las muestras permitió distinguir las poblaciones predominantes de cada estación de muestreo, a exponer en los ensayos de toxicidad. En resumen, un grupo de cianobacterias procedentes de las muestras costeras resultaron ser las más sensibles, y un segundo grupo de picoeucariotas, tomadas de la superficie del océano Atlántico, las más tolerantes al cobre. El análisis del ensayo se llevó a cabo mediante citometría de flujo lo que permitió estudiar otros parámetros celulares, aparte de la densidad celular. Pudiendo observar, en el caso de las cianobacterias, un incremento de la tolerancia al cobre con incremento de su tamaño celular; que no resultó tan evidente en el caso del grupo de picoeucariotas. Finalmente, al relacionar la tolerancia al cobre con las poblaciones procedentes de distintas localizaciones geográficas de muestreo podemos concluir que, otros factores, tales como: el tamaño celular, proximidad a costa, o concentraciones del metal in situ, pueden tener una mayor influencia que la localización geográfica de la población.This work has been supported by the Spanish CICYT (Spanish Commission for Research and Development) in the contract of the project PETRI 95-0971.Peer reviewe

Temperature dependent second-order Raman scattering in CuI

We report second-order Raman scattering spectra of copper iodide bulk single crystals aside from the fundamental TO and LO mode. The spectral shape was reproduced by a 2-phonon density of states calculated by DFT. Characteristic multi-phonon features were identified and assigned to combination, overtone and difference modes. In this way, the energy of acoustic zone-boundary phonons was determined. The temperature dependence of those modes and the fundamental optical phonons was analyzed by means of phonon-phonon interactions and lattice expansion effects up to room temperature. Processes related to the mode energy shift and width were identified for phonons at high symmetry points. The shifts due to lattice expansion are in accordance with the predictions by DFT in quasi-harmonic approximation using PBEsol functional.Comment: 11 pages, 6 figures, 3 tables. Submitted to Phys. Rev.

The White Dwarfs Within 25 pc of the Sun: Kinematics and Spectroscopic Subtypes

We present the fractional distribution of spectroscopic subtypes, range and distribution of surface temperatures, and kinematical properties of the white dwarfs (WDs) within 25 pc of the Sun. There is no convincing evidence of halo WDs in the total 25 pc sample of 224 WDs. There is also little to suggest the presence of genuine thick disk subcomponent members within 25 pc. It appears that the entire 25 pc sample likely belongs to the thin disk. We also find no significant kinematic differences with respect to spectroscopic subtypes. The total DA to non-DA ratio of the 25 pc sample is 1.8, a manifestation of deepening envelope convection, which transforms DA stars with sufficiently thin H surface layers into non-DAs. We compare this ratio with the results of other studies. We find that at least 11% of the WDs within 25 pc of the Sun (the DAZ and DZ stars) have photospheric metals that likely originate from accretion of circumstellar material (debris disks) around them. If this interpretation is correct, then it suggests the possibility that a similar percentage have planets, asteroid-like bodies, or debris disks orbiting them. Our volume-limited sample reveals a pileup of DC WDs at the well-known cutoff in DQ WDs at Teff ∼ 6000 K. Mindful of small number statistics, we speculate on its possible evolutionary significance. We find that the incidence of magnetic WDs in the 25 pc sample is at least 8% in our volume-limited sample, dominated by cool WDs. We derive approximate formation rates of DB and DQ degenerates and present a preliminary test of the evolutionary scenario that all cooling DB stars become DQ WDs via helium convective dredge-up with the diffusion tail of carbon extending upward from their cores

Evaluation of foam properties of saponin from Ilex paraguariensis A. St. Hil. (Aquifoliaceae) fruits

Saponins are natural compounds able to form abundant foam, a desirable quality required in some chemical, foods, cosmetic and pharmaceutical processes. Ilex paraguariensis A. St. Hil. (Aquifoliaceae) known as mate, is a South American widely cultivated specie due to the preparation of a tea-like beverage from its leaves. Moreover, its green fruits are a rich source of non-toxic and very low haemolytic saponins. In this study, mate saponin fraction (MSF) was evaluated as a foam former, focusing on its foamability, foam lifetime, and film drainage in the presence of different electrolytes (ionic strength I = 0.024 M). Sodium dodecyl sulphate (SDS) and polysorbate 80 (Poly-80) were used as reference surfactants. The critical micelle concentration (CMC), the minimum attainable surface tension (&#947;CMC), surface excess concentration (&#915;) and cross-section molecular surface (A) values of MSF were comparable to those of Poly-80. The foamability of MSF and both reference surfactants was equivalent. The addition of MgCl2 resulted in a negative effect on MSF foamability. The salts NaCl, KBr, and KNO3 exhibited a negative influence on MSF foam lifetime. Similar behavior was observed for MSF film drainage (order of activity: Na2HPO4 >; MgCl2 &#8776; NaCl &#8776; KNO3 >; KBr), where a primary fast film drainage rate was followed by film thinning stabilization after around 5 min. The behavior described above seems to be uncorrelated to the solutions' zeta potential.As saponinas são compostos naturais capazes de formar espuma abundante, qualidade desejável exigida em alguns processos químicos, alimentícios, cosméticos e farmacêuticos. Ilex paraguariensis A. St. Hil. (Aquifoliaceae), mais conhecida como mate, é uma espécie largamente cultivada devido ao consumo do chimarrão. Além disso, seus frutos verdes representam uma fonte rica de saponinas pouco tóxicas e pouco hemolíticas. Nesse trabalho avaliou-se a fração de saponinas de mate (MSF) como formadora de espuma, com ênfase na espumabilidade, permanência da espuma e drenagem do filme na presença de diferentes eletrólitos (I = 0,024 M). Dodecil sulfato de sódio (SDS) e polissorbato 80 (Poly-80) foram utilizados como tensoativos-referência. Os valores de concentração micelar crítica (CMC), tensão superficial na CMC (&#947;CMC), concentração de excesso de superfície (&#915;) e área do grupamento polar na interface (A) referente à MSF foram comparáveis ao Poly-80. A espumabilidade da MSF e de ambos os tensoativos-referência foram equivalentes. A adição de MgCl2 resultou em um efeito negativo sobre a espumabilidade de MSF. Os sais NaCl, KBr e KNO3 tiveram influência negativa sobre a estabilidade da espuma. Em relação à drenagem do filme de MSF, após 60 min. seguiu-se a ordem Na2HPO4 >; MgCl2 &#8776; NaCl &#8776; KNO3 >; KBr, caracterizando uma drenagem inicial acelerada seguida pelo equilíbrio hidrodinâmico do filme após 5 min. O comportamento observado parece não estar relacionado com o potencial zeta das soluções

Early events of Bacillus anthracis germination identified by time-course quantitative proteomics

Germination of Bacillus anthracis spores involves rehydration of the spore interior and rapid degradation of several of the protective layers, including the spore coat. Here, we examine the temporal changes that occur during B. anthracis spore germination using an isobaric tagging system. Over the course of 17 min from the onset of germination, the levels of at least 19 spore proteins significantly decrease. Included are acid-soluble proteins, several known and predicted coat proteins, and proteins of unknown function. Over half of these proteins are small (less than 100 amino acids) and would have been undetectable by conventional gel-based analysis. We also identified 20 proteins, whose levels modestly increased at the later time points when metabolism has likely resumed. Taken together, our data show that isobaric labeling of complex mixtures is particularly effective for temporal studies. Furthermore, we describe a rigorous statistical approach to define relevant changes that takes into account the nature of data obtained from multidimensional protein identification technology coupled with the use of isobaric tags. This study provides an expanded list of the proteins that may be involved in germination of the B. anthracis spore and their relative levels during germination.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55849/1/5199_ftp.pd

Programa química na educação

Trabalho apresentado no 31º SEURS - Seminário de Extensão Universitária da Região Sul, realizado em Florianópolis, SC, no período de 04 a 07 de agosto de 2013 - Universidade Federal de Santa Catarina.As alterações por que passa uma sociedade determinam variações nas relações sociais e, podem gerar novos modelos culturais, entre eles a tecnológica que está atrelada a possibilidade de o sujeito agir a partir de um saber do qual ele se apropria, tornando-se um cidadão competente. É nessa perspectiva que o Programa Químico na Educação conta com três projetos: Portal da Química, Química no Ensino Fundamental e Materiais Didático-pedagógicos para o Ensino de Química. O objetivo geral do Programa é colaborar na promoção de melhorias na qualidade do ensino de Ciências e de Química nos distintos níveis de aprendizagem. O Portal é um apoio ao ambiente acadêmico, capaz de adicionar serviços, informações e ser intercâmbio entre alunos, professores e sociedade. Os Materiais didático-pedagógicos possibilitam maior acesso dos estudantes a novas ferramentas educacionais. Na Química no Ensino Fundamental estão sendo desenvolvidas metodologias de ensino-aprendizagem e atividades experimentais adaptados às dimensões da criança e do adolescente e ao desenvolvimento da autonomia e das habilidades científicas com alunos do 9º ano em três escolas públicas. Quanto a metodologia, cada projeto tem suas especificidades: visitas à instituições envolvidas; desenvolvimento de atividades pedagógicas; aplicação de aulas práticas com materiais do cotidiano; experimentos de baixo custos; confecção e divulgação de materiais digitais como tabelas de dicas, apostila, vídeo-aulas abrangendo professores e alunos de todos os níveis; manutenção do Portal; administração dos alunos responsáveis pela publicação e criação desses conteúdos. Os resultados são parciais, pois o programa tem período de finalização previsto para dezembro de 2013. Em relação aos materiais didático-pedagógicos já confeccionamos XXXX jogos que estão a disposição no Laboratório de Psicologia da Educação da UDESC/CCT. O portal da química já conta com mais de 23 mil acessos. Alguns de regiões como Estados Unidos, Portugal e Angola. Desses acessos os conteúdos mais procurados são artigos, curiosidades e definições