Friction and wear of nanocrystalline materials and nanolaminated composites.

In the search of new wear resistant coatings for applications such as cutting tools and turbine refurbishing, a wide range of coatings, belonging to emerging classes of materials, namely, nanocrystalline materials and nanolayered composites, have been produced and tested. These coatings were produced using an rf magnetron sputtering system and include monolithic nanocrystalline metals (Al,Ti,Cu), nanolaminated composites composed of alternating layers of metal/ceramic (Al/Al\sb2O\sb3, Ti/TiN) and metal/metal (Ti/Cu). The metal layer thickness in the as-sputtered films of Al/Al\sb2O\sb3 ranged from 70 to 500 nm, and 150 to 450 nm in Ti/TiN. The nonmetals (Al\sb2O\sb3,TiN) layer thicknesses ranged from 10 to 40 nm and total film thicknesses of 10-15 $\mu$m. As-sputtered nanocrystalline aluminum films with an average grain size of 16.4 nm were isothermally annealed at 573 K to increase the grain size up to 98.0. nm. All materials were characterized and tested for their tribological properties. Friction and wear tests were performed under unlubricated sliding conditions using pin-on-disc type tribometer which was designed and constructed for measuring wear rates and coefficients of friction of thin films in air and in vacuum. The coefficient of friction of the materials tested against the stainless steel pin varied with the sliding distance. At the early stages of sliding the coefficient of friction rose to a peak, followed by a decrease to a steady-state value. The transition to the steady-state in the friction curve corresponded to a transition from severe wear to mild wear. In aluminum the value of the peak coefficient of friction decreased from \rm\mu\sb{p} = 1.4 for a coarse grain size of 10\sp6nm to \rm\mu\sb{p} = 0.6 for a grain size of 16.4 nm when tested under ambient conditions. The coefficient of friction of nanocrystalline aluminum showed a 30% increase when tested in vacuum (10\sp{-6} torr). Within the grain size range of 15-100 nm, the wear rates were found to be linearly dependent on the square root of the grain size \rm(W\sb{s} = 8.5\times 10\sp{-4} + (2.44 \times 10\sp{-4}).\ D\sp{1/2} for severe wear and \rm W\sb{m} = {-}1.9 \times 10\sp{-4} + (5.1 \times 10\sp{-5}).\ D\sp{1/2} for mild wear). The peak value of the coefficient of friction decreased about 70% in Al/Al\sb2O\sb3 (with 200 nm Al layer thickness) while a 60% improvement in the steady-state coefficient of friction was measured in Ti/TiN (with 150 nm Ti layer thickness) in comparison to the as-sputtered monolithic aluminum and titanium films, respectively. An increase in wear resistance with decreasing layer thickness was also observed (for example, \rm W\sb{s} = 7.0 \times 10\sp{-5} + (2.9 \times 10\sp{-7}).\ \lambda\sp{0.5}\sb{Ti}). Mechanical properties (hardness and elastic moduli) of the films were measured using an ultra-microindentation system. Hardness measurement of nanocrystalline aluminum revealed that within the grain size range 15-100 nm the hardness-grain size data obeys a Hall-Petch type relationship (i.e., \rm H = 34\ \lbrack MPa\rbrack + 0.21 \lbrack MPa\cdot m\sp{0.5}\rbrack\ D\sp{-0.5}\ \lbrack m\sp{-0.5}\rbrack). The hardness of Al/Al\sb2O\sb3 and Ti/TiN could also be described in the formalism of the Hall-Petch type indicating that ceramic layers inhibit slip transfer across metallic layers. (Abstract shortened by UMI.)Dept. of Mechanical, Automotive, and Materials Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1996 .F37. Source: Dissertation Abstracts International, Volume: 59-08, Section: B, page: 4384. Advisers: D. O. Northwood; A. T. Alpas. Thesis (Ph.D.)--University of Windsor (Canada), 1996

Mechanical and crystallographic anisotropy in zirconium alloy tubing.

The annealing behaviour of 60% tube reduced and stress relieved Zircaloy-4 nuclear fuel cladding material is studied over the temperature range 300 to 1000\sp\circC for annealing times of 10\sp3, 10\sp4 and 10\sp5 seconds. For annealing temperatures up to 500\sp\circC there is little change in texture and mechanical anisotropy; rather, the tubing becomes softer due to recovery and removal of cold-work. In the temperature range 500 to 800\sp\circC, there is change in microhardness due to recrystallization and grain growth effects. For annealing temperatures above 800\sp\circC, the overall room temperature strength of the tubing is increased due to phase changes and the tubing exhibits a more mechanically anisotropic behaviour. The data on the mechanical anisotropy ratio (minimum/maximum hardness) shows that the recrystallized structure produced at about 500\sp\circC for annealing times 10\sp3 and 10\sp4 seconds is more mechanically anisotropic than the as-received tubing. (Abstract shortened by UMI.)Dept. of Mechanical, Automotive, and Materials Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1991 .F375. Source: Masters Abstracts International, Volume: 31-01, page: 0412. Thesis (M.A.Sc.)--University of Windsor (Canada), 1991

Chemosensetizing and cardioprotective effects of resveratrol in doxorubicin- treated animals

BACKGROUND: Doxorubicin (DOX), an anthracycline antibiotic is one of the most effective anticancer drug used in the treatment of variety of cancers .Its use is limited by its cardiotoxicity. The present study was designed to assess the role of a natural product resveratrol (RSVL) on sensitization of mammary carcinoma (Ehrlich ascites carcinoma) to the action of DOX and at the same time its protective effect against DOX-induced cardiotoxicity in rats. METHODS: Ehrlich ascites carcinoma bearing mice were used in this study. Percent survival of tumor bearing mice was used for determination of the Cytotoxic activity of DOX in presence and absence of RSVL. Uptake and cell cycle effect of DOX in tumor cells in the presence of RSVL was also determined. Histopatholgical examination of heart tissues after DOX and/or RSVL therapy was also investigated. RESULTS: DOX at a dose level of 15 mg/kg increased the mean survival time of tumor bearing mice to 21 days compared with 15 days for non tumor-bearing control mice. Administration of RSVL at a dose level of 10 mg/kg simultaneously with DOX increased the mean survival time to 30 days with 70% survival of the tumor-bearing animals. RSVL increased the intracellular level of DOX and there was a strong correlation between the high cellular level of DOX and its cytotoxic activity. Moreover, RSVL treatment showed 4.8 fold inhibition in proliferation index of cells treated with DOX. Histopathological analysis of rat heart tissue after a single dose of DOX (20 mg/kg) showed myocytolysis with congestion of blood vessels, cytoplasmic vacuolization and fragmentation. Concomitant treatment with RSVL, fragmentation of the muscle fiber revealed normal muscle fiber. CONCLUSION: This study suggests that RSVL could increase the cytotoxic activity of DOX and at the same time protect against its cardiotoxicity

The alpha 7 nicotinic receptor agonist PHA-543613 hydrochloride inhibits <i>Porphyromonas gingivalis</i>-induced expression of interleukin-8 by oral keratinocytes

Objective: The alpha 7 nicotinic receptor (α7nAChR) is expressed by oral keratinocytes. α7nAChR activation mediates anti-inflammatory responses. The objective of this study was to determine if α7nAChR activation inhibited pathogen-induced interleukin-8 (IL-8) expression by oral keratinocytes.&lt;p&gt;&lt;/p&gt; Materials and methods: Periodontal tissue expression of α7nAChR was determined by real-time PCR. OKF6/TERT-2 oral keratinocytes were exposed to &lt;i&gt;Porphyromonas gingivalis&lt;/i&gt; in the presence and absence of a α7nAChR agonist (PHA-543613 hydrochloride) alone or after pre-exposure to a specific α7nAChR antagonist (α-bungarotoxin). Interleukin-8 (IL-8) expression was measured by ELISA and real-time PCR. Phosphorylation of the NF-κB p65 subunit was determined using an NF-κB p65 profiler assay and STAT-3 activation by STAT-3 in-cell ELISA. The release of ACh from oral keratinocytes in response to &lt;i&gt;P. gingivalis&lt;/i&gt; lipopolysaccharide was determined using a GeneBLAzer M3 CHO-K1-blacell reporter assay.&lt;p&gt;&lt;/p&gt; Results: Expression of α7nAChR mRNA was elevated in diseased periodontal tissue. PHA-543613 hydrochloride inhibited &lt;i&gt;P. Gingivalis&lt;/i&gt;-induced expression of IL-8 at the transcriptional level. This effect was abolished when cells were pre-exposed to a specific α7nAChR antagonist, α-bungarotoxin. PHA-543613 hydrochloride downregulated NF-κB signalling through reduced phosphorylation of the NF-κB p65-subunit. In addition, PHA-543613 hydrochloride promoted STAT-3 signalling by maintenance of phosphorylation. Furthermore, oral keratinocytes upregulated ACh release in response to &lt;i&gt;P. Gingivalis&lt;/i&gt; lipopolysaccharide.&lt;p&gt;&lt;/p&gt; Conclusion: These data suggest that α7nAChR plays a role in regulating the innate immune responses of oral keratinocytes.&lt;p&gt;&lt;/p&gt

An Analysis of the Impact of the Political Changes on Labor Unions in Egypt

This study analyzes the impact of the political changes on labor unions in Egypt in the period from 1960 to 1967. In 1960-1961 Egypt became a socialist country with one political party, the Arab Socialist Union. As a result of that development in the political arena, a wave of socialist laws were introduced by the government, affecting not only the labor unions' traditional functions, but also the industrial relations system in general. The study came to the following conclusions. 1. The role of the labor unions in the industrial relations system and especially in formulating the socialist laws was minimized in Egypt in the 1960-1967 period. 2. From an economic point of view, the socialist laws in the 1960-1967 period had restrained economic development process by reducing savings, not supplying the economy with skilled productive workers, causing inflation, and the wage structure did not work as an incentive system to stimulate productivity. 3. The socialist laws did not achieve any of their expected objectives partly because no one except the government was involved in these laws' formulation and implementation. 4. Except for the small increase in wages, the average worker did not achieve any tangible benefits that could improve his economic and social status. 5. The existence of political control over labor unions and over the industrial relations system will continue and persist as long as labor unions do not have effective leadership and as long as there is no political opposition to the government

Accurate measurement of in-plane and out-of-plane shear moduli on 3D woven SiC-SiBC material

International audienc

Mechanism of Action of an Environmentally Relevant Organochlorine Mixture in Repressing Steroid Hormone Biosynthesis in Leydig Cells

Within Leydig cells, steroidogenesis is induced by the pituitary luteinizing hormone (LH). The binding of LH to its receptor increases cAMP production, which then activates the expression of genes involved in testosterone biosynthesis. One of these genes codes for the steroidogenic acute regulatory (STAR) protein. STAR is part of a complex that shuttles cholesterol, the precursor of all steroid hormones, through the mitochondrial membrane where steroidogenesis is initiated. Organochlorine chemicals (OCs) are environmental persistent organic pollutants that are found at high concentrations in Arctic areas. OCs are known to affect male reproductive health by decreasing semen quality in different species, including humans. We previously showed that an environmentally relevant mixture of OCs found in Northern Quebec disrupts steroidogenesis by decreasing STAR protein levels without affecting the transcription of the gene. We hypothesized that OCs might affect STAR protein stability. To test this, MA-10 Leydig cell lines were incubated for 6 h with vehicle or the OCs mixture in the presence or absence of 8Br-cAMP with or without MG132, an inhibitor of protein degradation. We found that MG132 prevented the OC-mediated decrease in STAR protein levels following 8Br-cAMP stimulation. However, progesterone production was still decreased by the OC mixture, even in the presence of MG132. This suggested that proteins involved in steroid hormone production in addition to STAR are also affected by the OC mixture. To identify these proteins, a whole cell approach was used and total proteins from MA-10 Leydig cells exposed to the OC mixture with or without stimulation with 8Br-cAMP were analyzed by 2D SDS-PAGE and LC-MS/MS. Bioinformatics analyses revealed that several proteins involved in numerous biological processes are affected by the OC mixture, including proteins involved in mitochondrial transport, lipid metabolism, and steroidogenesis

A comparative study of different antiviral treatment protocols in HCV related cryoglobulinemic vasculitis

The treatment of HCV and its sequelae are used to be predominantly based on Interferon (IFN). However, this was associated with significant adverse events as a result of its immunostimulant capabilities. Since their introduction, the directly acting antiviral drugs (DAAs), have become the standard of care to treat of HCV and its complications including mixed cryoglobulinemic vasculitis (MCV). In spite of achieving sustained viral response (SVR), there appeared many reports describing unwelcome complications such as hepatocellular and hematological malignancies as well as relapses. Prolonged inflammation induced by a multitude of factors, can lead to DNA damage and affects BAFF and APRIL, which serve as markers of B-cell proliferation. We compared, head-to-head, three antiviral protocols for HCV–MCV treatment As regards the treatment response and relapse, levels of BAFF and APRIL among pegylated interferon α-based and free regimens (Sofosbuvir + Ribavirin; SOF–RIBA, Sofosbuvir + Daclatasvir; SOF–DACLA). Regarding clinical response HCV–MCV and SVR; no significant differences could be identified among the 3 different treatment protocols, and this was also independent form using IFN. We found no significant differences between IFN-based and free regimens DNA damage, markers of DNA repair, or levels of BAFF and APRIL. However, individualized drug-to-drug comparisons showed many differences. Those who were treated with IFN-based protocol showed decreased levels of DNA damage, while the other two IFN-free groups showed increased DNA damage, being the worst in SOF–DACLA group. There were increased levels of BAFF through follow-up periods in the 3 protocols being the best in SOF–DACLA group (decreased at 24 weeks). In SOF–RIBA, CGs relapsed significantly during the follow-up period. None of our patients who were treated with IFN-based protocol had significant clinico-laboratory relapse. Those who received IFN-free DAAs showed a statistically significant relapse of constitutional manifestations. Our findings suggest that IFN-based protocols are effective in treating HCV–MCV similar to IFN-free protocols. They showed lower levels of DNA damage and repair. We believe that our findings may offer an explanation for the process of lymphoproliferation, occurrence of malignancies, and relapses by shedding light on such possible mechanisms