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ABSTRACT The current Covid-19 pandemic has been the most discussed topic of the year, mostly about protection and ways to avoid dissemination of the virus. In the healthcare system, especially in the operating rooms, the viability of laparoscopic surgery was questioned, mostly because of the transmission through aerosol. This article tries to suggest a way to minimize risks of laparoscopic surgery, during this situation, by using electrostatic filters, a simple, effective and low cost alternative.

RESUMO Objetivo: Descrever e analisar a prevalência de baixa acuidade visual e suas causas em estudantes do ensino público de Belo Horizonte/MG. Métodos: Estudo transversal de 1452 escolares de 5 a 19 anos, do ensino público de Belo Horizonte/MG, triados e atendidos entre 2011 e 2014. Resultados: Da amostra total, 150 pacientes (10,33%) apresentaram baixa acuidade visual à triagem, recebendo encaminhamento para atendimento oftalmológico. Quarenta (26,66%) foram encaminhados e compareceram à consulta, onde 29 (72,5%) apresentaram indicação de correção visual. O astigmatismo miópico simples e composto foram os diagnósticos mais relacionados à prescrição de óculos. Conclusão: O estudo mostrou que a prevalência de baixa acuidade visual na população estudada foi compatível com demais programas semelhantes. Em contrapartida, a taxa de abstenção foi maior do que o esperado, evidenciando a importância da criação de medidas preventivas e informativas quanto à importância do cuidado com a saúde ocular.

The chemical resistance of ceramic glazes susceptible to it, and more specifically the glazes formulated with a calcium matt frit, is enhanced by depositing on the surface a thin layer of zirconium oxide. A stabilized zirconia sol is the precursor of the layer, which is deposited by spray painting over the glaze, and with a mild heat treatment (Tmax ≈ 400 ° C) is transformed into ZrO2 and anchored to the glaze’s surface. Chemical resistance tests show that the protected glaze does not suffer a visually significant attack by concentrated hydrochloric acid, conditions under which the same glaze without the coating is severely damaged. The used precursor generates a zirconium oxide layer that protects the underlying glaze, so that the chemical attack by the hydrochloric acid is confined to cracks and discontinuities in the deposited layer.La resistencia al ataque químico de vidriados cerámicos susceptibles al mismo, concretamente formulados a partir de una frita mate de calcio, se ha mejorado depositando en la superficie una capa delgada de óxido de circonio. Un sol de circonio estabilizado es el precursor de la capa, el cual se deposita mediante aerografía sobre el vidriado cocido y con un tratamiento térmico suave (Tmax ≈ 400 ºC), es transformado en ZrO2 y anclado a la superficie. Los ensayos de resistencia química demuestran que el vidriado protegido no sufre un ataque apreciable visualmente por parte del ácido clorhídrico concentrado, condiciones en las que el mismo vidriado sin el recubrimiento resulta gravemente dañado. El precursor utilizado genera una capa de óxido de circonio que protege el vidriado subyacente, de modo que el ataque químico por parte del ácido clorhídrico queda confinado al entorno de las grietas y discontinuidades de la capa depositada.

This study was undertaken to determine the effect of zircon content and firing temperature on the hardness and indentation modulus of zircon–glass composites obtained by sintering. A standard non-devitrified borosilicate glass (SRM 717a) powder and an industrial micrometric zircon powder were used to prepare mixtures with a zircon volume/solids volume between 0 and 0.63, by the wet method. The values of these mechanical properties were determined by nanoindentation and related to the most important microstructural characteristics of the composites, such as porosity, zircon volume fraction, glass volume fraction, and average zircon grain size. Composite mechanical performance was interpreted and determined by statistically analysing the results of a large number of indentations using two maximum loads. An empirical model was developed that describes the effect of these microstructural characteristics on composite hardness and modulus of indentation. Composites of high hardness (11.3 ± 2.5 GPa) and low porosity (ε = 0.07) were obtained at 1100 °C from a mixture with a zircon volume/solids volume of 0.43. [ABSTRACT FROM AUTHOR]

Highlights • Closed porosity and minimum attainable porosity in the composite depend on zircon content. • The solution–reprecipitation mechanism only occurs at high temperatures, for high zircon contents. • Except for high zircon contents, composite sintering takes place via particle rearrangement by viscous flow. • A kinetic model describing the sintering, by viscous flow, of zircon–glass composites is proposed. • The effect of temperature on the process rate is glass viscosity dependent. Abstract This report sets out the results obtained on studying the sintering process of glass–zircon composites, analysing the microstructural changes that developed on modifying zircon content. The sintering of composites with moderate zircon contents only developed via particle rearrangement by viscous flow. In contrast, at high zircon contents, the zircon solution–reprecipitation process was also required. A kinetic model was developed and validated that describes the effect of the heating rate and zircon volume fraction on the composite degree of non-isothermal sintering progress associated with particle rearrangement by viscous flow. [ABSTRACT FROM AUTHOR]

Many materials of a glass-ceramic nature are obtained by glass particle sinter-crystallisation, whose process kinetics have been studied very little. The present study analyses the physico-chemical transformations that develop during the firing of a complex commercial satin glaze (containing more than five phases), with high frit content, particularly focusing on sinter-crystallisation kinetics. Glaze sintering and phase evolution were studied by hot stage microscopy (HSM) and X-ray diffraction (XRD). The glaze melting and crystallisation ranges and the kinetic parameters of the crystallisation process were determined by differential thermal analysis (DTA). Glaze sinter-crystallisation behaviour and the development of the crystal mass fractions, residual glass compositions, and effective viscosity, η eff , during heating are discussed, based on Rietveld analysis of the XRD data. A new kinetic model was developed that describes the non-isothermal sinter-crystallisation of materials exhibiting three-stage sintering. A two-step kinetic model is involved: sintering with concurrent surface crystallisation (corresponding to sintering stages I and II) and sintering with simultaneous partial melting of crystalline phases (sintering stage III). The experimental data obtained by hot stage microscopy (HSM) at different heating rates were compared with those estimated by the model. The results obtained by the two methods exhibited very good agreement. The crystallisation kinetic parameters (activation energy, E cr , and Avrami index, n, obtained by DTA, were consistent with the viscous flow activation energy, Q 2 , corresponding to the first sintering step (sintering stages I and II). The model was used to calculate the values of the effective sintering viscosity, η s , of the glaze melt. These values were compared with the experimental effective viscosity, η eff , data obtained by hot stage microscopy (HSM). Both sets of results exhibited good agreement. Effective sintering viscosity, η s , which is readily measurable, helps better understand the role played by the different glaze constituents and by the firing conditions in sintering, enabling more rational design of these materials. [ABSTRACT FROM AUTHOR]

Libertarianism deals with what the law should be. In this article, we focus on what the appropriate law to punish criminals should be in a libertarian society; that is, one that respects the Non-Aggression Principle and property rights. We examine various theories of punishment and explain why some are incompatible with libertarianism. We contribute to the latest libertarian theory of punishment suggesting the necessity to take time preference into consideration. We conclude stating a limit and a limitation to libertarian punishment theories.

A structural model was developed to describe the shear-thinning behaviour of dense, stabilised suspensions of plate-like particles. The model is based on the following main assumptions: the particles are distributed in more or less compact layers, oriented parallel to the flow; the particles are assumed to behave as hard disks, disk thickness being the sum of crystal thickness plus twice the Debye length; when the shear stress increases, the orientation of the plate-like particles in the flow direction also increases, thus increasing layer compactness. In order to test the proposed model, a kaolin was selected and characterised. The kaolin was used to prepare more than 40 aqueous suspensions, modifying the solids volume fraction between ϕ = 0.20 and ϕ = 0.475 and the dispersant (sodium silicate) content between X s = 0.075 and X s = 0.225 mg dispersant/m 2 solid. The flow curves of all suspensions were determined in the quasi-steady state. The results confirmed the validity of the model to satisfactorily describe the combined effect of ϕ and X S on the flow curves in the shear-thinning range. [ABSTRACT FROM AUTHOR]