101 resultados para Porosidade total


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Seeing a total solar eclipse is often described as a once-in-a-lifetime experience. However, for many who have experienced totality, once-in-a-lifetime is simply not enough. They want more, and are willing to go to great lengths often at great expense to repeat the experience. What is it like to experience totality? What is it about the experience that motivates these eclipse chasers? Is there an eclipse chaser personality? Can eclipse chasing actually be described as an addiction? This book describes the people who dedicate their lives to chasing their dream.

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Restoration of joint centre during total hip arthroplasty is critical. While computer-aided navigation can improve accuracy during total hip arthroplasty, its expense makes it inaccessible to the majority of surgeons. This article evaluates the use, in the laboratory, of a calliper with a simple computer application to measure changes in femoral head centres during total hip arthroplasty. The computer application was designed using Microsoft Excel and used calliper measurements taken pre- and post-femoral head resection to predict the change in head centre in terms of offset and vertical height between the femoral head and newly inserted prosthesis. Its accuracy was assessed using a coordinate measuring machine to compare changes in preoperative and post-operative head centre when simulating stem insertion on 10 sawbone femurs. A femoral stem with a modular neck was used, which meant nine possible head centre configurations were available for each femur, giving 90 results. The results show that using this technique during a simulated total hip arthroplasty, it was possible to restore femoral head centre to within 6?mm for offset (mean 1.67?±?1.16?mm) and vertical height (mean 2.14?±?1.51?mm). It is intended that this low-cost technique be extended to inform the surgeon of a best-fit solution in terms of neck length and neck type for a specific prosthesis.

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Rice is comparatively efficient at assimilating inorganic arsenic (As i), a class-one, non-threshold carcinogen, into its grain, being the dominant source of this element to mankind. Here it was investigated how the total arsenic (Ast) and Asi content of Italian rice grain sourced from market outlets varied by geographical origin and type. Total Cr, Cd Se, Mg, K, Zn, Ni were also quantified. Ast concentration on a variety basis ranged from means of 0.18 mg kg-1 to 0.28 mg kg -1, and from 0.11 mg kg-1 to 0.28 mg kg-1 by production region. For Asi concentration, means ranged from 0.08 mg kg-1 to 0.11 mg kg-1 by variety and 0.10 mg kg -1 to 0.06 mg kg-1 by region. There was significant geographical variation for both Ast and Asi; total Se and Ni concentration; while the total concentration of Zn, Cr, Ni and K were strongly influenced by the type of rice.

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Pollution of subterranean water by arsenic (As) in Asia has resulted in the worst chemical disaster in human history. For populations living on subsistence rice diets, As contamination of rice grain contributes greatly to dietary As exposure. The main objectives of this study were to compare two dehusking processes: (a) wet process (soaking of rice, boiling and mechanical hulling) and (b) dry process (mechanical hulling), and recommend the method leading to a lower As content in commercial rice. In general, hulling of paddy rice (373 mu g As kg(-1)) significantly decreased As content in rice grain (311 mu g As kg(-1)). The final As concentrations in boiled rice (final product of the wet process) and atab rice (dry process) were 332 and 290 mu g kg(-1). Thus, the dry method is recommended for dehusking paddy rice if not As-free water is available. However, villagers can reduce the As content in the wet system by discarding the soaking water and using new water for the light boiling. Finally, it is not recommended to use rice husk for feeding animals because the As concentration is very high, approximately 1,000 mu g As kg(-1).

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Objective: Plasma total homocysteine (tHcy) has been positively associated with carotid intima-media thickness (IMT) in non-diabetic populations and in a few cross-sectional studies of diabetic patients. We investigated cross-sectional and prospective associations of a single measure of tHcy with common and internal carotid IMT over a 6-year period in type 1 diabetes. Research design and methods: tHcy levels were measured once, in plasma obtained in 1997–1999 from patients (n = 599) in the Epidemiology of Diabetes Interventions and Complications (EDIC) study, the observational follow-up of the Diabetes Control and Complications Trial (DCCT). Common and internal carotid IMT were determined twice, in EDIC “Year 6” (1998–2000) and “Year 12” (2004–2006), using B-mode ultra-sonography. Results: After adjustment, plasma tHcy [median (interquartile range): 6.2 (5.1, 7.5) μmol/L] was significantly correlated with age, diastolic blood pressure, renal dysfunction, and smoking (all p < 0.05). In an unadjusted model only, increasing quartiles of tHcy correlated with common and internal carotid IMT, again at both EDIC time-points (p < 0.01). However, multivariate logistic regression revealed no significant associations between increasing quartiles of tHcy and the 6-year change in common and internal carotid IMT (highest vs. lowest quintile) when adjusted for conventional risk factors. Conclusions: In a type 1 diabetes cohort from the EDIC study, plasma tHcy measured in samples drawn in 1997–1999 was associated with measures of common and internal carotid IMT measured both one and seven years later, but not with IMT progression between the two time-points. The data do not support routine measurement of tHcy in people with Type 1 diabetes.

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This chapter features a discussion of the economy and mobilization for the First World War. The authors analyse the implications and cost of total war, concluding with an examination of its contradictory legacies. In studying the war’s impact on Germany in particular, the chapter provides an in-depth look at the consequences of war on Europe’s strongest pre-war economy, without the complications of separating out the issues of a developing country, which can mimic those faced in wartime. The economic challenges that warring parties faced during the war included mobilization, warfare, labour shortage, impaired domestic economic activity, restricted international trade, a systematic redistribution of resources towards the war economy, food rationing, the predictable emergence of black markets, and a drop in living standards. The authors also discuss strategies to meet the significant financial demands associated with the war, and its tumultuous economic and political aftermath.

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The current study focuses on the effect of the material type and the lubricant on the abrasive wear behaviour of two important commercially available ceramic on ceramic prosthetic systems, namely, Biolox(R) forte and Bioloxl(R) delta (CeramTec AG, Germany). A standard microabrasion wear apparatus was used to produce '3-body' abrasive wear scars with three different lubricants: ultrapure water, 25 vol% new-born calf serum solution and 1 wt% carboxymethyl cellulose sodium salt (CMC-Na) solution. 1 mu m alumina particles were used as the abrasive. The morphology of the wear scar was examined in detail using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Subsurface damage accumulation was investigated by Focused Ion Beam (FIB) cross-sectional milling and Transmission Electron Microscopy (TEM). The effect of the lubricant on the '3-body' abrasive wear mechanisms is discussed and the effect of material properties compared. (C) 2009 Elsevier B.V. All rights reserved.

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A new experimental procedure based on attenuated total reflection infrared spectroscopy has been developed to investigate surface species under liquid phase reaction conditions. The technique has been tested by investigating the enhanced selectivity in the hydrogenation of α,β-unsaturated aldehyde citral over a 5% Pt/SiO2 catalyst toward unsaturated alcohols geraniol/nerol, which occurs when citronellal is added to the reaction. The change in selectivity is proposed to be the result of a change in the citral adsorption mode in the presence of citronellal. Short time on stream attenuated total internal reflection infrared spectroscopy has allowed identification of the adsorption modes of citral. With no citronellal, citral adsorbs through both the C═C and C═O groups; however, in the presence of citronellal, citral adsorption occurs through the C═O group only, which is proposed to be the cause of the altered reaction selectivity.