Effect of the temperature on the TMOS sono-hydrolysis and a study of the structure of the resulting aged sonogels

The effect of temperature on the oxalic acid catalyzed sono-hydrolysis of tetramethoxysilane (TMOS) was studied by means of a heat flux calorimetric method. The activation energy of the process was measured as (24.5 +/- 0.8) kJ/mol in the temperature range between 10 and 50 degreesC. The structural characteristics of the resulting sonogels, after long period of aging in saturated conditions, were studied by means of small angle X-ray scattering. The structure can be described as formed by similar to2.7 nm mean size mass fractal-like aggregates (clusters) of primary silica particles of similar to0.3 nm mean size, all imbibed in a liquid phase. The average mass fractal dimension of the clusters was found to be 2.58. The primary particle density was estimated as 2.23 g/cm(3), in good agreement with the value frequently quoted for fused silica. The volume fraction of the clusters, in the saturated sonogels was estimated as about 28%. The moment in which the meniscus of the liquid phase penetrates into the clusters under rapid evaporation process has been detected by an inflection in the first derivative of the curve of weight loss in a simple thermogravimetric test. (C) 2003 Elsevier B.V. All rights reserved.

Structural evolution of aerogels prepared from TEOS sono-hydrolysis upon heat treatment up to 1100 degrees C

The structural evolution of aerogels prepared from TEOS sono-hydrolysis was studied as a function of the temperature of heat treatment up to 1100 degreesC by means of small angle X-ray scattering (SAXS) and density measurements. The mass fractal structure of the original wet sonogel (with scattering exponent alpha similar to 2.2) apparently transforms to a surface fractal structure in a length scale lesser than similar to1.5 nm, upon the process resulting in aerogel. Such a structural transformation is interpreted by the formation of new particles with characteristic dimension of similar to1.5 nm, with rough boundaries or electronic density fluctuations (or ultra-micropores) in their interior. The structural arrangement of these particles seem to preserve part of mass fractal characteristics of the original wet sonogel, now in a length scale greater than similar to1.5 nm. The electronic density heterogeneities in the particles start to be eliminated at around 800 degreesC and, at 900 degreesC, the particles become perfectly homogeneous, so the structure can be described as a porous structure with a porosity of similar to68% with similar to9.0 nm mean size pores and similar to4.3 nm mean size solid particles. Above 900 degreesC, a vigorous viscous flux sintering process sets in, eliminating most of the porosity and increasing rapidly the bulk density in an aerogel-glass transformation. (C) 2003 Elsevier B.V. All rights reserved.

About the nanoporosity elimination above 800 degrees C in xerogels prepared from TEOS sono-hydrolysis

Small angle X-ray scattering measurements, bulk and skeleton density data and an in-situ study by dilatometric thermal analysis about the nanoporosity elimination above 800 degreesC in TEOS sonogels are presented. Apparently, two processes act during the nanoporosity elimination, which precedes the foaming phenomenon often observed in such systems. The first, with an activation energy of (3.9 +/- 0.4) x 10(2) kJ/mol and high frequency factor, is the controlling process of the most nanoporosity elimination at higher temperature. The value of this activation energy is compatible to that for viscous flux throughout densification process in typical silica-based materials. The second, with an activation energy of (49 +/- 5) kJ/mol and low frequency factor, seems to be the controlling process of the first and extremely slow nanoporosity elimination at low temperature.

Pediatras e os distúrbios respiratórios do sono na criança

OBJECTIVES. assessment of opinions and practices of pediatricians concerning sleep-disordered breathing (SDB) in children. Methods. randomly 516 pediatricians were selected in the state of São Paulo, Brazil. A survey mailed to them included questions regarding: their professional profile, knowledge about SDB in childhood, opinions and practices for diagnosis and treatment of these diseases. RESULTS. 112 anonymous completed surveys were returned (21.7%). The teaching of SDB during medical school and pediatric residency training was considered unsatisfactory respectively by 65.2% and 34.8% of the pediatricians. Forty-nine respondents (43.8%) rated their knowledge about SDB in children as regular, 39 (34.8%) as good and 17 (15.2%) as unsatisfactory. The most important sleep-related questions were: mouth breathing, breathing pauses, sleep amount, excessive daytime sleepiness and nocturnal wheezing. Clinical aspects regarded as the most significant for suspecting obstructive sleep apnea syndrome (OSAS) were: breathing pauses, adenoid hypertrophy, mouth breathing, craniofacial anomaly and snoring. The most frequent practices for evaluation of OSAS in children were: cavum radiography with referral to an otorhinolarnygologist (25%) and nocturnal pulse oximetry (14.2%). Only 11.6% of pediatricians recommended overnight polysomnography and 4.5%, nap polysomnography. The most effective practices for SDB were considered to be: adenoidectomy and adenotonsillectomy, parents counseling, weight loss and sleep hygiene. CONCLUSIONS. there is a gap between research on SDB in childhood and pediatric practice. © 2006 Associação Médica Brasileira.

Efetividade dos aparelhos intrabucais de avanço mandibular no tratamento do ronco e da síndrome da apneia e hipopneia obstrutiva do sono (SAHOS): Revisão sistemática

Introduction: The snoring is produced by the vibration of the soft palatum and/or other oropharyngeal tissues, during the air passage, in the breathing function. OSAHS is defined as the closing of 30%, at least, of the nasal/ buccal airway for 10 seconds or more, in spite of existing inspiratory effort, accompanied by oxyhemoglobin de- saturation of 4% or more. Objectives: To evaluate the available scientific evidence about the use of mandibular advancement intraoral appliances in the treatment of the snoring and/or OSAHS. Methodology: Electronic search strategy using predefined key-words and criteria was realized including studies published until October of 2008. It was also used the qualitative evaluation of the articles methodology. Results: Although a significant number of articles has studied this subject, only 7 articles showed methodological quality to be included in this systematic review. Conclusions: The intraoral appliances are widely prescribed for the treatment of snoring and OSAHS as primary therapy and as an alternative to patients who are unable to tolerate the positive airway pressure therapy.

Edema agudo de pulmão de pressão negativa como complicação grave de síndrome de apneia obstrutiva do sono em crianças. Relatos de casos

Introduction: Obstructive sleep apnea syndrome is related to cardiopulmonary complications in children. It is important to know its patophysiology and possible complications to help reduce risks in this group. Aims: To report three cases of severe cardiorespiratory complications of obstructive sleep apnea managed in the intensive care unit (ICU). Case report: Two children with no previous diagnosis of obstructive sleep apnea syndrome suffered acute congestive heart failure and acute lung oedema with need of ICU and improved after adenotonsillectomy. In a third case, the patient had acute lung oedema as a complication after adenotonsillectomy. Conclusions: Paediatricians and otolaryngologists must be aware of the clinical manifestations of severe sleep apnea. Early referring to treatment and special attention at pre and post surgical periods are essentials to avoid serious complications.

Caracterización de los síndromes de sostenibilidad del desarrollo. El caso de Argentina. Taller "Síndromes de sostenibilidad del desarrollo en América Latina", Santiago de Chile 16 y 17 de septiembre de 2002

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Los síndromes de sostenibilidad del desarrollo. El caso de México

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Síndromes de sostenibilidad ambiental del desarrollo en Colombia: taller Síndromes de sostenibilidad del desarrollo en América Latina""

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Síndromes oculares secundárias a infecção pelo Herpesvirus felino-1-Revisão

The feline infectious respiratory disease is the most common diagnosed infection in the veterinary clinic routine, being the Feline Herpesvirus1 the most important causal agent. Once infected, the cat will become a lifetime latent carrier, experiencing episodes of viral reactivation and spontaneous spread especially when there is a stress factor involved. This virus acts in the upper respiratory system and is also associated with eye diseases. The diagnosis is made by viral isolation and treatment protocol is based on a topic antiviral therapy, even though many of them are epiteliotoxic and may progress with intense discomfort in felines.The purpose of this paper is to describe the main ocular manifestations and syndromes seen in cats suffering from feline herpesvirus. Conjunctivitis, epithelial and stromal keratitis, corneal ulceration and indolent ulcers are the main ocular manifestations associated with viral infection, whereas symblepharon, keratoconjunctivitis sicca, proliferative keratitis and corneal sequestration are the main eye syndromes that can be observed in infected animals.

Exercício, funcionalidade e distúrbios do sono em pacientes com doença de Parkinson

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Viagem ao sono: relações de tradicionalidade e consumo na Praia do Sono - Parati (RJ)

Pós-graduação em Ciências Sociais - FFC

Análise quantitativa do tempo de trânsito oral e faríngeo em síndromes genéticas

Pós-graduação em Fonoaudiologia - FFC

Correlação entre 6-sulfatoximelatonina, distúrbios do sono e citocinas inflamatórias em Transtornos do Espectro do Autismo (TEA)

Pós-graduação em Fonoaudiologia - FFC

Estudo das lesões laríngeas e do grau de disfonia em pacientes com paracoccidioidomicose

Pós-graduação em Doenças Tropicais - FMB