2,145 research outputs found

    Ultrastable glasses portray similar behaviour to ordinary glasses at high pressure

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    Pressure experiments provide a unique opportunity to unravel new insights into glass-forming liquids by exploring its effect on the dynamics of viscous liquids and on the evolution of the glass transition temperature. Here we compare the pressure dependence of the onset of devitrification, Ton, between two molecular glasses prepared from the same material but with extremely different ambient-pressure kinetic and thermodynamic stabilities. Our data clearly reveal that, while both glasses exhibit different dTon/dP values at low pressures, they evolve towards closer calorimetric devitrification temperature and pressure dependence as pressure increases. We tentatively interpret these results from the different densities of the starting materials at room temperature and pressure. Our data shows that at the probed pressures, the relaxation time of the glass into the supercooled liquid is determined by temperature and pressure similarly to the behaviour of liquids, but using stability-dependent parametersPostprint (published version

    Notes on Lagothrix flavicauda (Primates: Atelidae): oldest known specimen and the importance of the revisions of museum specimens

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    The yellow-tailed woolly monkey, Lagothrix flavicauda (Humboldt, 1812), is a large atelid endemic to the cloud forests of Peru. The identity of this species was uncertain for at least 150 years, since its original description in 1812 without a voucher specimen. Additionally, the absence of expeditions to the remote Peruvian cloud forests made it impossible to collect material that would help to confirm the true identity of L. flavicauda during the 19th and first half of the 20th century. Until now, the specimens of L. flavicauda collected by H. Watkins, in 1925, in La Lejía (Amazonas, Peru) were thought to be the oldest ones deposited in any scientific collection. Nevertheless, after reviewing the databases of the several international museums and literature, we found one specimen of L. flavicauda deposited at the Muséum National d’histoire Naturelle (Paris, France) collected in 1900 by G.A. Baër, in the most eastern part of San Martín (Peru), where the presence of this species was not confirmed until 2011. Thus, Baër’s specimen represents the oldest known specimen of the yellow-tailed woolly monkey and the only one coming from the eastern part of the species’ distribution. Finally, we highlight the importance of online scientific databases for easily diagnosable species. However, caution needs to be taken when using them. We also discuss the value of scientific collections as sources of new discoveries

    Impacto da identificação do ponto anatômico e do erro padrão de mensuração na análise cefalométrica utilizando um modelo de simulação matemática

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    Objective: To assess, using a mathematical simulation model, the participation of each coordinate involved in the formation of cephalometric angles and to determine the extent to which errors in the identification of cephalometric landmarks can, individually and collectively, influence the measurement of these angles. Material and Methods: The reference values and standard errors of 13 landmarks obtained from the analysis of 30 cephalograms were used. For each landmark, 1000 observations were simulated using the Monte Carlo method. On the basis of linear regression models, equations designed to estimate measurement errors due to landmark identification errors were obtained and analysed. Results: The coordinates most involved in the formation of the angles SNA, SNB, ANB, FMA, PPL, DFC, and AEF were Ny, Ny, Ax, Goy, Poy, Poy, and Ptmx, respectively, and the standard measurement errors for these angles were 1.2, 0.9, 0.8, 1.6, 1.5, 1.5, and 1.4, respectively. Conclusion: The standard measurement error of the angle depends on the geometric impact coefficient and the standard error of the coordinates involved in the formation of the angles, and the geometric impact coefficient varies according to the angle analysed.Objetivos: Avaliar, empregando um modelo matemático de simulação, a participação de cada coordenada envolvida na formação de ângulos cefalométricos, assim como determinar a extensão da influência dos erros na identificação dos pontos cefalométricos, individual e coletivamente, na mensuração destes ângulos. Materiais e métodos: Foram utilizados os valores de referência e os erros padrão de 13 pontos anatômicos obtidos a partir da análise de 30 cefalogramas. Para cada ponto anatômico, foram simuladas 1000 observações utilizando o método de Monte Carlo. Com base em modelos de regressão linear, foram obtidas e analisadas equações destinadas a estimar os erros de medição devido a erros na identificação dos pontos cefalométricos. Resultados: As coordenadas mais envolvidas na formação dos ângulos SNA, SNB, ANB, FMA, PPL, DFC, e AEF foram Ny, Ny, Ax, Goy, Poy, Poy, e Ptmx, respectivamente, e os erros padrão de mensuração destes ângulos foram 1,2; 0,9; 0,8; 1,6; 1,5; 1,5 e 1,4, respectivamente. Conclusões: O erro padrão de mensuração de cada ângulo cefalométrico depende do coeficiente de impacto geométrico e do erro padrão das coordenadas dos pontos anatômicos envolvidos na formação dos mesmos, sendo que o coeficiente de impacto geométrico varia de acordo com o ângulo analisado

    Spirotetramat — An Alternative for the Control of Parasitic Sucking Insects and its Fate in the Environment

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    Spirotetramat is an insecticide derived from tetramic acid, a systemic material, for the control of sucking insects in their juvenile, immature stages, including aphids, scale insects, and whitefly. It produces growth inhibition of younger insects, reduces the ability of insects to reproduce, resulting in mortality. It acts to inhibit the biosynthesis of lipids and represents a new alternative for the control of problematic insects such as Planococcus ficus and Aphis gossypii. After a foliar application of spirotetramat, it enters the plant and transforms to its metabolite enol, along with the metabolite ketohydroxy, which are the two main products of degradation

    Accuracy of computer-assisted surgery in immediate implant placement : an experimental study

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    Purpose: Computer-guided surgery has been increased in recent years. Nonetheless, few data are available on the validation of this technique for immediate implant placement. The purpose of this in vitro study was to evaluate the accuracy of computer-guided surgery in immediate implant placement. Materials and methods: Cone-beam computed tomography scans (CBCTs) and virtual models were obtained of eight fresh pigs hemi-mandibles to perform the digital planning of implants placement. Fifteen implants were simulated, and surgical guides were designed to transfer the digital planning to the surgical procedure. Postsurgical CBCTs were performed to compare the position of the planned implants versus the real implant position. Paired t-test and the intra-class correlation coefficient (ICC) were used to assess the mean differences and correlations in each outcome variable evaluated twice by one experienced researcher. Furthermore, variations were compared with the results reported in the scientific literature using a one-sample t-test P 0.05). The ICC values ranged from 0.888 to 0.949. Furthermore, the mean deviation was 1.43 mm at the implant neck, 2.19 mm at the apex, and 6.81° for the angular deviation. Similarly, significant differences (P < 0.05) were found at the neck and angular deviation when comparing the results with values reported in the literature. Conclusions: Although some variations were observed, they did not have a clinically significant impact. Therefore, computer-guided surgery could be satisfactorily used in immediate implants placement

    Manejo de água na cultura do arroz: consumo, ocorrência de plantas daninhas, absorção de nutrientes e características produtivas.

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    Experiments were carried out during four years in order to study the effects of water management, on its consumption, weed occurrence, nutrient uptake and rice (cv. CICA 8 and CNA- 1051 Ajuricaba) yield. The treatments were: continuous flooding during entire cicle; intermittent flooding during entire cicle; intermittent flooding during vegetative phase followed by continuous flooding during reproductive phase; subsurface irrigation by raising the water table, with rows of 0.20 m wide; subsurface irrigation, with rows of 0.30 m wide. Water consumption was high due to high percolation and lateral flow losses of 61 to 91% of total water consumption, depending on the irrigation system. Intermittent flooding used 71% less water than continuous flooding, that, however, reduced weed occurrence and increased P and Fe uptake. Subsurface irrigation increased Mn uptake. Intermittent flooding during vegetative phase followed by continuous flooding during reproductive phase produced higher rice yield due to the increasement in tillering, number of grains/panicle, and grain weight.Durante quatro anos foram conduzidos experimentos para se verificar o efeito do manejo de água no seu consumo, na ocorrência de plantas daninhas, na absorção de nutrientes e nas características produtivas do arroz (Oryza sativa L.), cvs. CICA 8 e CNA-1051 (Ajuricaba). Os tratamentos de manejo de água consistiram de: inundação contínua durante todo o ciclo; inundação intermitente durante todo o ciclo; inundação intermitente na fase vegetativa seguida de inundação contínua na fase reprodutiva; subirrigação pela elevação do lençol freático, com espaçamento de 0,20 m entre linhas de plantas, e subirrigação, com espaçamento de 0,30 m entre linhas. O consumo de água foi elevado em decorrência das altas perdas por percolação e fluxo lateral, que corresponderam de 61 a 91% do consumo total, dependendo do sistema de irrigação utilizado. A inundação intermitente propiciou economia de 71% de água. A inundação contínua reduziu a ocorrência de plantas daninhas e favoreceu a absorção de P e Fe, enquanto a subirrigação favoreceu a absorção de Mn. A combinação de inundação intermitente na fase vegetativa, com inundação contínua na fase reprodutiva, propiciou produções mais elevadas por favorecer o perfilhamento e a obtenção de elevado número de grãos por panícula, com maior peso dos grãos

    Educating for earthquake science and risk in a tectonically slowly deforming region

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    Over the past decade, scientists have been called to participate more actively in public education and outreach (E&O). This is particularly true in fields of significant societal impact, such as earthquake science. Local earthquake risk culture plays a role in the way that the public engages in educational efforts. In this article, we describe an adapted E&O program for earthquake science and risk. The program is tailored for a region of slow tectonic deformation, where large earthquakes are extreme events that occur with long return periods. The adapted program has two main goals: (1) to increase the awareness and preparedness of the population to earthquake and related risks (tsunami, liquefaction, fires, etc.), and (2) to increase the quality of earthquake science education, so as to attract talented students to geosciences. Our integrated program relies on activities tuned for different population groups who have different interests and abilities, namely young children, teenagers, young adults, and professionals

    Multiple glass transitions in vapor-deposited orientational glasses of the most fragile plastic crystal Freon 113

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    We investigate by fast-scanning nanocalorimetry the formation of Freon 113 films from the vapor phase at deposition temperatures ranging from 50 to 120 K, that is, spanning above and below the transition temperature of the glassy crystal to the plastic crystal (Tgc = 72 K). Analysis of the heat capacity curves indicates that vapor deposition at T < Tgc of the highly fragile Freon 113 yields structural and orientational glasses in the as-deposited state depending on the temperature range of deposition. Interestingly, growing above Tgc produces plastic crystals with a conformational ratio C1/Cs that changes with Tdep above and below 110–120 K, the temperature at which previous works have identified the arrest of the transformations between the C1 and Cs conformers.Peer ReviewedPostprint (author's final draft
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