No presente trabalho estudou-se a influência da adição de alumina nas propriedades da espuma vítrea. A alumina foi empregada com a finalidade de proporcionar uma maior refratariedade para os corpos ...cerâmicos. Foram investigados corpos cerâmicos à base de vidro sodo-cálcico moído, oriundo de embalagens de vidro transparente, calcário dolomítico e alumina. Os corpos cerâmicos foram formulados com teores de 3% e 5% em peso de calcário dolomítico, ambos sem e com 4% em peso de alumina, conformados por prensagem uniaxial e queimados entre 600 ºC e 1000 ºC, com uma taxa de aquecimento de 150 K/h. A caracterização tecnológica dos corpos cerâmicos envolveu a determinação da expansão volumétrica. A microestrutura foi avaliada por meio de microscopia óptica e eletrônica de varredura. Os resultados experimentais mostraram que a adição de alumina influencia a expansão volumétrica dos corpos cerâmicos, reduzindo a espumação significativamente.In this work, the influence of the alumina addition on the properties of foam glass was studied. Alumina was introduced to the mixture in order to increase the refractoriness of the final product. Ceramic bodies were composed by ground soda-lime glass from transparent glass bottles, dolomitic lime and alumina. The ceramic bodies were formulated with 3 and 5 wt.% of dolomite lime, both without alumina and with 4 wt.% of this material, uniaxially pressed, and fired in the temperature range from 600 ºC to 1000 ºC at a heating rate of 150 K/h. The technological characterization of the ceramic bodies involved the determination of the volume expansion. The microstructure was investigated by optical microscopy and scanning electron microscopy. The experimental results show that the addition of alumina influenced the volume expansion of the ceramic bodies, decreasing the foaming.
The purpose of this study was to investigate whether patients with chronic meningococcemia have abnormalities in their humoral immune system. The alternative and classical complement system, the ...levels of IgA, IgG and IgM, as well as IgG subclasses were studied in 15 individuals who had recovered from chronic meningococcemia. We found one individual with complete deficiency of properdin, a component of the alternative complement pathway. In the other patients, the complement system was normal. The mean plasma IgG concentration was significantly below normal in the patient group, while the mean values of IgA, IgM and the IgG subclasses were normal. Two individuals, however, had low IgG2 and IgG4 levels. We conclude that properdin deficiency and reduced plasma IgG levels may predispose to chronic meningococcal disease, but that the majority of patients with chronic meningococcemia have a normal humoral immune system.
Erosive wear is characterized by successive loss of material from the surface due to the continuous impact of solid particles. This type of wear affects numerous industries, such as power generation, ...mining, and the pneumatic transportation of solids. The worst case scenario normally occurs where there is a combination of both erosion and oxidation, especially at high temperatures. In order to minimize damage caused by erosive wear, many authors propose the use of better bulk materials or surface coatings, and generally cermets (ceramic carbides in metal matrices) are suggested. Various researchers have conducted experiments to study the wear mechanisms occurring in this kind of materials, but most of these experiments do not lead to similar results; in fact, there is no accordance among the authors, and moreover, some wear variables are ignored. In this book, studies undertaken in this field by several investigators have been discussed extensively. At the end of this book, table reviews are suggested to summarize the most important mechanisms of the erosive wear in bulk and coating cermets.
We investigated simultaneously blood flow velocity waveforms of uteroplacental vessels, the umbilical artery, the fetal aorta and the fetal common carotid artery. In pregnancies with intrauterine ...growth retardation or preeclampsia we found low diastolic velocities in uteroplacental vessels, the umbilical artery and the fetal aorta and high diastolic velocities in the common carotid artery. Abnormal waveforms of the common carotid artery were most effective in predicting fetal compromise and might be a valuable clinical tool for the supervision and therapy of high-risk pregnancies in the future.
A porcelana de cinza de ossos é amplamente aceita e alcança alto valor de mercado, entretanto, sua produção ainda é pouco difundida, de modo que sua fabricação e pesquisa são restritas a poucos ...países. Sendo o Brasil grande produtor de gado, apresenta grande potencial para a reciclagem de ossos, podendo-se encontrar aplicação destes em materiais cerâmicos. Neste trabalho foi feita uma análise comparativa das características técnicas entre uma formulação de porcelana obtida com cinzas de ossos conforme a receita tradicional inglesa e uma formulação de porcelana tradicional. Os resultados mostraram que a sinterização de porcelana de cinzas de ossos requer cuidados extras em ciclos rápidos de queima quando comparada à porcelana tradicional, devido a um menor intervalo de gresificação. No entanto, a maior resistência mecânica e as qualidades estéticas, destacando-se a elevada alvura, fazem desta porcelana bastante atrativa em termos de potencial de aplicações industriais.Porcelains from bone ash are widely accepted and present high market value, however, their manufacture and research are still restricted to few countries. As a great producer of cattle, Brazil presents great potential for the recycling of cattle bone into ceramic materials. In this work, it was realized a comparative investigation of technical properties of a typical porcelain composition manufactured from bone ash according to English traditional composition and a traditional porcelain. The results revealed that it is more difficult to sinter bone porcelain in fast firing cycles, once it showed shorter firing intervals compared to traditional porcelains. However, the higher mechanical strength and better aesthetic qualities, especially its whiteness, make bone porcelains very attractive materials in terms of industrial applications potential.
During systems-level consolidation, mnemonic representations initially reliant on the hippocampus are thought to migrate to neocortical sites for more permanent storage, with an eminent role of sleep ...for facilitating this information transfer. Mechanistically, consolidation processes have been hypothesized to rely on systematic interactions between the three cardinal neuronal oscillations characterizing non-rapid eye movement (NREM) sleep. Under global control of de- and hyperpolarizing slow oscillations (SOs), sleep spindles may cluster hippocampal ripples for a precisely timed transfer of local information to the neocortex. We used direct intracranial electroencephalogram recordings from human epilepsy patients during natural sleep to test the assumption that SOs, spindles and ripples are functionally coupled in the hippocampus. Employing cross-frequency phase-amplitude coupling analyses, we found that spindles were modulated by the up-state of SOs. Notably, spindles were found to in turn cluster ripples in their troughs, providing fine-tuned temporal frames for the hypothesized transfer of hippocampal memory traces.
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