Compression testing of a sintered Ti6Al4V powder compact for biomedical applications

In this study, the compression deformation behavior of a Ti6Al4V powder compact, prepared by the sintering of cold compacted atomized spherical particles (100–200 μm) and containing 36–38% porosity, was investigated at quasi-static (1.6×10⁻³–1.6×10⁻¹ s⁻¹) and high strain rates (300 and 900 s⁻¹) using, respectively, conventional mechanical testing and Split Hopkinson Pressure Bar techniques. Microscopic studies of as-received powder and sintered powder compact showed that sintering at high temperature (1200 °C) and subsequent slow rate of cooling in the furnace changed the microstructure of powder from the acicular alpha () to the Widmanstätten (+β) microstructure. In compression testing, at both quasi-static and high strain rates, the compact failed via shear bands formed along the diagonal axis, 45° to the loading direction. Increasing the strain rate was found to increase both the flow stress and compressive strength of the compact but it did not affect the critical strain for shear localization. Microscopic analyses of failed samples and deformed but not failed samples of the compact further showed that fracture occurred in a ductile (dimpled) mode consisting of void initiation and growth in phase and/or at the /β interface and macrocracking by void coalescence in the interparticle bond region.     

Autopsies in children: are they still useful?

BACKGROUND: Juvenile chronic arthritis (JCA) is the commonest autoimmune rheumatic disease in childhood and presents different clinical subtypes. Juvenile chronic arthritis is considered to be of a polygenic nature and its genetic background is still under investigation. The clinical profile of JCA in the Greek population has not been studied completely. This study retrospectively analyzed the clinical and immunological features of JCA in Greek children presented between 1989 and 1994. Human leukocyte antigen (HLA)-positive or -negative associations in the different clinical subtypes were also detected. The findings of this study were correlated with those reported from other populations. METHODS AND RESULTS: Antinuclear antibodies (ANA) anti-ds DNA and anti-extractable nuclear antigen antibodies were estimated by immunofluorescent and ELISA assays. Human leukocyte antigen typing was performed by microlymphocytotoxicity, using immunobeads. The peak ages of JCA onset were between 2 and 5 years and also between 9 and 12 years. There was a high female predominance in pauciarticular and polyarticular groups. The most common disease was pauciarticular (58.7%) followed by systemic (25%) arthritis. The incidence of eye involvement was 12.5% and presented only in the pauciarticular group. Overall, ANA positivity was 53.7%, increasing to 90% in pauciarticular cases associated with chronic uveitis. In the early onset (EOPA) pauciarticular subtype, positive-HLA associations with alleles DR11 and DR8 were shown. In the late onset pauciarticular (LOPA) group only B27 allele was increased. CONCLUSIONS: The results of this retrospective study did not reveal major differences between JCA in Greek children compared with other Caucasian series.     

Adenosine A1 receptor stimulation antagonizes the negative inotropic effects of the PKC activator dioctanoylglycerol

It has been suggested that adenosine cardioprotection occurs via adenosine A1 receptor-mediated activation of protein kinase C (PKC). However, adenosine has well-known vasodilatory effects in the myocardium, whereas PKC is a vasoconstrictor. This study examined whether adenosine A1 receptor activation alters the effects of the PKC activator. 1,2-dioctanoyl-s,n-glycerol (DOG) in isolated perfused rat hearts (left-ventricular developed pressure) and rat ventricular myocytes ([Ca2+]i and cell shortening). Exposure to DOG decreased left-ventricular developed pressure by 30%, an effect that was completely reversible. Pretreatment of isolated hearts with either the PKC inhibitor chelerythrine or the adenosine A1 agonist 2-chloro-N6-cyclo-cyclo-isolated pentlyadenosine (CCPA) attenuated the negative inotropic effects of DOG. In the isolated myocytes, DOG decreased [Ca2+]i and cell shortening by 25 and 28%, respectively, effects that were attenuated by both chelerythrine and CCPA. The CCPA attenuation of the DOG-induced decrease in [Ca2+]i and cell shortening was blocked by pretreating the myocytes with the adenosine A1 antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). These results indicate that in rat ventricular myocardium, adenosine A1 receptor activation attenuates the apparent PKC-dependent negative inotropic effects of DOG via preservation of [Ca2+]i levels.     

A numerical study on determination of volume averaged thermal transport properties of metal foam structures using X-ray microtomography technique

Abstract

Volume averaged thermal transport properties of two metal foams with 10 and 20 PPI are obtained by using microtomography technique. The digital 3D structures of samples are generated in computer environment. The governing equations are solved for the entire domain and the volume averaged technique is used to determine interfacial heat transfer coefficient, longitudinal and transverse thermal dispersion conductivity. The study is performed for the pore scale Reynolds number from 100 to 600. The obtained results are within the ranges of the suggested correlations in literature. The present study supports the correlations suggested by Calmidi and Mahajan (2000) and Zhang et al. (2016).     

Pb(II) and Cd(II) removal from aqueous solutions by olive cake

The removal of heavy metals from wastewater using olive cake as an adsorbent was investigated. The effect of the contact time, pH, temperature, and concentration of adsorbate on adsorption performance of olive cake for Pb(II) and Cd(II) ions were examined by batch method. Adsorption of Pb(II) and Cd(II) in aqueous solution onto olive cake was studied in single component. After establishing the optimum conditions, elution of these ions from the adsorbent surface was also examined. The optimum sorption conditions were determined for two elements. Maximum desorption of the Pb(II) and Cd(II) ions were found to be 95.92 and 53.97% by 0.5M HNO(3) and 0.2M HCl, respectively. The morphological analysis of the olive cake was performed by the scanning electron microscopy (SEM).     

Multiple attribute decision-making solution to material selection problem based on modified fuzzy axiomatic design-model selection interface algorithm

Material selection, one of the mostly encountered decision problems in material science literature, is still an onerous task for manufacturing organisations. Achieving accurate solution to this issue, the paper developed a model selection interface to enable analytical solutions to different problem concepts in material selection under multiple attribute decision-making (MADM) environments. Specifically, the generic framework of the fuzzy axiomatic design-model selection interface (FAD-MSI) is modified and successfully applied to the different material selection problem concepts. Consequently, the derived problem-model sets can be referred to accomplish further proposals on this era.     

An integrated decision aid extension to material selection problem

Choice of an adequate material in design process is one of the critical tasks for the relevant decision-makers. At this insight, the consistency of the decisions is extremely depending on the relevance of adapted techniques to the nature of different problem cases. This paper proposed an integrated decision aid (IDEA) to match the suitable techniques with different problem cases based on the following six dimensions: (i) the type of the decision problem, (ii) the size of the problem, (iii) selection of the preference techniques by decision-makers, (iv) decision-makers’ preference structure, (v) the necessity for the use of relative importance, (vi) the nature of performance values. Furthermore, the implementation procedure of the proposed IDEA for a material selection problem is demonstrated with the previously cited applications from material science literature. Hereafter, it is expected that the IDEA provides great advantages and encouragements to researchers/practitioners in order to prevent excessive time consuming, probable misapplications, and the other challenging issues in multiple criteria analysis of material selection problems.     

Fatty acid composition and sensory properties of Wels catfish (Silurus glanis) hot smoked with different sawdust materials

This study aims to compare chemical, physical and sensorial parameters of the Wels catfish (Silurus glanis), hot smoked using vine, poplar, lemon tree and oak sawdust as well as corncob. Significant differences (P < 0.05) in proximate composition were found between fresh and smoked samples; however, the changes in fatty acid composition were less significant. In the fatty acid composition of control group, monounsaturated fatty acids (41.60%) had the highest share in fatty acids, which was followed by saturated fatty acids (29.95%) and polyunsaturated fatty acids (28.34%). The major fatty acids were observed to be C16:0, C18:0; C16:1 n‐7, C18:1 n‐9c, C18:1 n‐9t and C18:2 n6c. There were significant differences (P < 0.05) between the groups considering their colour measurement results. General preference criteria such as appearance, odour, texture, colour and taste were chosen for the sensorial analysis, which were rated by the panellists. According to the results of overall appearance, the fillet pieces smoked with lemon tree (9.00), poplar (8.66), corncob (8.00), oak (7.33) and vine (5.33) sawdust were determined as the most preferred, in order.     

Small amount TiB2 addition into B4C through sputter deposition and hot pressing

Small amount of TiB₂ (<5 wt%) was added into B₄C through a novel method that combines the use of sputter deposition and hot pressing. Sputter deposition provided more uniform dispersion of TiB₂ grains with smaller grain sizes as compared to the conventional particulate mixing. Small amount TiB₂ addition demonstrated to be an effective way for improving the fracture behavior and toughness of B₄C while not sacrificing its outstanding lightweight property to a large extent: 2.3 wt% TiB₂ addition brought 15% improvement in indentation fracture toughness while resulting in less than 2% increase in density. The improvement can be attributed to the combination of crack impeding by TiB₂ grains and crack deflection at the B₄C–TiB₂ interfaces. TiB₂ also played as grain growth inhibitor resulting in a slight increase (2%) in Vickers hardness. Another intention of employing sputter deposition was to modify the grain boundary of B₄C; however, neither formation of Ti-containing phase nor Ti segregation has been observed at grain boundaries likely due to the poor wettability of B₄C.