Granular self-organisation and reactivity—adsorbates and agglomerates particle size influence

The aim of this work is to study the organisation of the distributed system and the influence of adsorption and agglomeration phenomena in a dry bi-phase mixture. The studied system is a mixture of silica and carbonate. The parameter of interest is particle size. With the crossover of different fractions of silica and carbonate, it is possible to build a dimensional chessboard and then study the role of dimension in the organisation of distributed system. In these mixtures, several combinations are possible following the particle size. These combinations result from agglomeration and adsorption mechanisms. It is necessary to distinguish self-attractive phenomena (self-agglomeration and self-adsorption) that concern particles of same chemical composition, and inter-attractive phenomena (inter-agglomeration and inter-adsorption) that concern particles of different chemical compositions. The reactivity of the different mixtures treated thermally at 850 °C is measured by X-ray diffraction (DRX). It is estimated by the quantity of produced phases. Then this reactivity is explained by the different attractive phenomena studied.     

Locomotor activity rhythms in dogs vary with age and cognitive status.

Beagle dogs exhibited diurnal patterns of locomotor activity that varied as a function of age, cognitive status, and housing environment. Aged dogs housed in an indoor facility showed a delayed onset of activity following lights on and displayed shorter bouts of activity, with more rest periods during the day, compared with young dogs. Cognitively impaired aged dogs were more active and showed a delayed peak of activity compared with unimpaired aged dogs. Housing in continuous light did not disrupt activity rhythms. The effect of age was less prominent in dogs housed in an indoor/outdoor facility. This suggests that bright sunlight and natural light-dark transitions are better able to consolidate and synchronize the activity rhythms of the dogs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Mechanical Properties of the Novel Nanocrystalline Refractory Tantalum Alloys

Protection of Metals and Physical Chemistry of Surfaces - The nanocrystalline tantalum alloys were investigated in terms of mechanical properties. The materials were obtained by powder metallurgy...     

Resonant frequency of gold/polycarbonate hybrid nano resonators fabricated on plastics via nano-transfer printing

We report the fabrication of gold/polycarbonate (Au/PC) hybrid nano resonators on plastic substrates through a nano-transfer printing (nTP) technique, and the parametric studies of the resonant frequency of the resulting hybrid nano resonators. nTP is a nanofabrication technique that involves an assembly process by which a printable layer can be transferred from a transfer substrate to a device substrate. In this article, we applied nTP to fabricate Au/PC hybrid nano resonators on a PC substrate. When an AC voltage is applied, the nano resonator can be mechanically excited when the AC frequency reaches the resonant frequency of the nano resonator. We then performed systematic parametric studies to identify the parameters that govern the resonant frequency of the nano resonators, using finite element method. The quantitative results for a wide range of materials and geometries offer vital guidance to design hybrid nano resonators with a tunable resonant frequency in a range of more than three orders of magnitude (e.g., 10 KHz-100 MHz). Such nano resonators could find their potential applications in nano electromechanical devices. Fabricating hybrid nano resonators via nTP further demonstrates nTP as a potential fabrication technique to enable a low-cost and scalable roll-to-roll printing process of nanodevices.     

Study on microstructure and mechanical properties of spark plasma sintered Alumix 431 powder

Spark plasma sintering (SPS) has been used to successfully densify a 7075 aluminium alloy obtained from Alumix 431 powder. Sintering experiments were conducted at the temperature of 450 and 500°C for 2.5, 5 and 10?min. All the presented results confirm the excellent sinterability of Alumix 431 powder in vacuum during the SPS process and clearly show the effect of sintering temperatures and holding times on the densification, microstructure and mechanical properties of the obtained sintered compacts. The best results of hardness (1412?±?39?MPa), tensile strength (345?±?15?MPa) and compressive strength (618?±?4?MPa) were obtained by the compacts sintered at 500°C for 5 min.     

Protection of flavonoids against hypochlorite-induced protein modifications

Plant polyphenols, such as flavonoids, are ubiquitous components of human diet, and have been recognised as efficient radical scavengers and antioxidants. Their protective effects were especially seen in cell-free assays. Whilst in living cells, depending on experimental conditions, polyphenols may manifest both anti- and pro-oxidative activity. In the present study, the effectiveness of fifteen structurally different flavonoids against hypochlorite-mediated changes in in vitro systems, with and without cells, was tested and compared. Quercetin was found to be the best protector against hypochlorite-mediated fluorescein bleaching and BSA thiol groups oxidation, whilst in living cells its effects on hypochlorite-associated cytotoxicity were moderate. Contrary, epigallocatechin gallate, pelargonidin and catechin, with less impressive hypochlorite scavenging activity in cell-free assays, were the most effective against 3-chlorotyrosine formation after hypochlorite treatment. Taken together, special care should be taken when extrapolating the results on antioxidant propensity of food bioactive compounds in vitro to the cellular milieu.     

Micromechanical Measurements and Biocompatibility of the High Porosity Ti Scaffold Made with Saccharose as a Space Holder

Protection of Metals and Physical Chemistry of Surfaces - The paper presents mechanical properties of the porous Ti scaffold made with saccharose as a space holder. The Ti scaffolds had the...     

Characterization,Tribological and Mechanical Properties of Plasma Paste Borided AISI 316 Steel

The AISI 316 steel was treated by the plasma paste boriding by using a gas mixture of 70%H₂–30%Ar with a boron source of 100% B₂O₃ in the temperature range of 700–800 °C for 3, 5 and 7 h. The boride layers formed on the samples were observed by scanning electron microscope. The iron borides were also identified by the use of an X-ray microanalyzer, equipped with energy dispersive X-ray spectroscopy. The XRD analysis was carried out to identify the iron and metallic borides present inside the boride layer. Based on the kinetic data, the value of boron activation energy for the AISI 316 steel was estimated as 118.12 kJ mol^?1 and compared with the data available in the literature. A regression model based on ANOVA analysis was used to predict the boride layers’ thicknesses depending on the boriding parameters: the treatment time and the boriding temperature. A good correspondence was obtained between the experimental values and those predicted by the regression model. Furthermore, the wear behavior of the sample borided at 750 °C for 5 h was investigated. The significant increase in wear resistance of plasma borided layer was observed in comparison with the untreated AISI 316 steel. The nanomechanical properties of the sample, plasma paste borided at 700 °C for 7 h, were examined using the nanoindenter with a Vickers diamond tip. The load–displacement curves, as well as, Young’s moduli and hardness were shown for the selected measurements. The obtained results depended on the phase composition of the tested area.     

Transendothelial migration of lymphocytes from HIV-1-infected donors: a mechanism for extravascular dissemination of HIV-1

To identify factors that cause HIV-1 to establish perivascular foci of infected cells, we studied the transendothelial migration of blood mononuclear leukocytes (MNL) from 76 HIV+ patients and 41 controls. The fraction of patients' lymphocytes that migrated across endothelial cell monolayers in vitro was significantly increased (p < or = 0.03) compared with that of control donors. Migration of patients' CD4+ T cells was particularly enhanced, whereas the migration of monocytes did not differ between patients and controls. Lymphocyte migration correlated with expression of CD11a/CD18 and CD49d/CD29 and with the quantity of TNF-alpha produced as MNLs migrated through the endothelium. Measurement of HIV-1 proviral DNA copies in the patients' MNLs (n = 26) suggested that in half the cases virus-infected cells accumulated preferentially amidst the migratory leukocytes. We observed the same behavior with normal donor MNLs infected, in vitro, with each of 4 strains of HIV-1. The number of HIV-1 proviral DNA copies per million MNLs was 40 to 178 times higher in the migratory population than in the original population added to the endothelium. To test whether only certain strains of HIV-1 stimulate transendothelial migration of infected cells, we used single strand conformation polymorphism analysis to identify quasispecies of HIV-1 in the MNLs. If all strains of HIV-1 were equal in their ability to stimulate transendothelial migration, we expected to find no differences in the quasispecies present in the original and migratory cell populations. In fact the quasispecies differed in 14 of 19 paired samples, suggesting that only certain HIV-1 quasispecies promote transendothelial migration of infected cells.