Hardening of 316L stainless steel by laser surface alloying

The goal of this study is to investigate different hardening routes for 316L stainless steel by laser surface alloying. We have investigated the formation of iron-chromium carbides by SiC or carbon incorporation, the alloying with submicronic particles of TiC and the precipitation of titanium carbide from mixtures of Ti and SiC. For each hardening route we present the microstructures and the hardness of the processed surface alloys and the conditions leading to the best compromise between highest hardness, best homogeneity and lowest occurrence of cracks. From these results it can be reasoned that hardening by iron-chromium carbides is the best hardening route and that this surface alloy might be a good candidate for tribological applications.     

The chicken beta-globin gene promoter forms a novel "cinched" tetrahelical structure

We have previously shown that the G-rich sequence G16CG(GGT)2GG in the promoter region of the chicken beta-globin gene poses a formidable barrier to DNA synthesis in vitro (Woodford et al., 1994, J. Biol. Chem. 269, 27029-27035). The K+ requirement, template-strand specificity, template concentration independence, and involvement of Hoogsteen bonding suggested that the underlying basis of this new type of DNA synthesis arrest site might be an intrastrand tetrahelical structure. However, the arrest site lacks the four G-rich repeats that are a hallmark of previously described intramolecular tetraplexes and contains a number of noncanonical bases that would be expected to greatly destabilize such a structure. Here we report evidence for an unusual K+-dependent intrastrand "cinched" tetraplex. This structure has several unique features including the incorporation of bases other than guanine into the stem of the tetraplex, interaction between loop bases and bases in the flanking region, and base pairing between bases 3 and 5 of the tetrahelix-forming region to form a molecular "cinch." This finding extends the range of sequences capable of tetraplex formation as well as our appreciation of the conformational complexity of the chicken beta-globin promoter.     

Supramalleolar osteotomy for ankle valgus in myelomeningocele

Oral fibroblasts stimulated invasion of oral-carcinoma cells into the collagen matrix. The mechanisms of the fibroblast-induced stimulation of invasiveness was further investigated by examining cell motility and proteolytic activity of tumor cells, using mainly an adenoid-cystic-carcinoma cell line (ACCS) and normal fibroblasts from gingival tissues. Conditioned medium from the fibroblasts grown in serum-free medium was fractionated on a Superdex 200 pg column, and Peak 1 eluted at 200 to 300 kDa and Peak 2 eluted at 50 to 100 kDa were found to contain different specific activity. Treatment of ACCS cells with Peak 1 resulted in an increase in the production of proteolytic enzymes. Peak 2 stimulated both chemotaxis and chemokinesis of ACCS cells. A chemotactic factor was purified from the heparin-unbound fraction of Peak 2 by anion exchange and hydrophobic chromatography, and was named "fibroblast-derived motility factor (FDMF)". At 1 microg/ml, FDMF stimulated chemotaxis of ACCS cells by 4-fold compared with unstimulated controls. Characterization of the physicochemical properties of FDMF suggested that it might be different from any known motility factors. Exposure of ACCS cells to FDMF resulted in reduced amounts of actin stress fiber in the cytoplasm and induction of tyrosine phosphorylation of several cellular proteins detectable 30 to 60 min after treatment. These FDMF-induced changes were blocked by pre-treatment either with genistein or with pertussis toxin. These findings suggest that FDMF may be a novel protein which stimulates cell motility via a signaling pathway mediated by a pertussis-toxin-sensitive G protein and tyrosine phosphorylation.     

Nonlinear Performance Index (npi): A Tool for Manipulator Dynamics Improvement

The precise control of manipulators depends nonlinearly on the velocity of the motion as well as on manipulator configuration and commanded acceleration requiring complex control strategies. This paper presents a useful tool for identifying and quantifying nonlinear effects appearing during the motion of any manipulator, the Nonlinear Performance Index (npi). The npi takes into account not only the geometrical parameters defining the manipulator but also its structural dynamics through the use of inertial parameters like mass, inertia, centre of mass... The npi can be used in the design stage for analysing and reducing these undesirable nonlinear effects in any general motion or in the trajectory planning looking for paths along which more precise control is expected. The last part of the paper shows how this design optimisation and path planning has been applied to the Agribot, a fruit picking robot designed at the IAI.     

Discoloration of a red cationic dye by supported TiO(2) photocatalysis

The degradation under UV, visible and sunlight irradiation of C.I. Basic Red 46 (BR 46) dye used for acrylic fibers dyeing has been studied in a lab-scale continuous system with two different immobilized TiO(2) systems. Catalyst I was based on TiO(2) particles deposited on cellulose fibers; Catalyst II combined TiO(2) particles deposited on a layer of cellulose fibers (as in Catalyst I) with a layer of carbon fibers and finally a layer of cellulose fibers. The treatment of aqueous dye solutions and industrial wastewater contaminated with the same dye has been evaluated in terms of color removal and chemical oxygen demand (COD) decrease. With UV light, aqueous solutions containing dye were decolorized slightly more rapidly with Catalyst II than with Catalyst I. Sunlight was also very effective and experiments involving sunlight irradiation showed Catalyst II to be the more efficient, giving more than 90% discoloration after 20 min of treatment. Comparing the discoloration yield by adsorption or under visible light for both catalysts, it was observed that the difference between them is below 5%. The adsorption kinetics was found to follow a second-order rate law for Catalyst I and a first-order rate law for Catalyst II. The kinetics of photocatalytic degradation under UV or sunlight were found to follow a first-order rate law for both catalytic systems. Under sunlight the COD removal yield for textile wastewater reaches 33% with Catalyst I against 93% with Catalyst II.     

A dish-Stirling solar-thermal power system

This paper presents results of a preliminary design/economic study of a first-generation Point Focusing Distributed Receiver (PFDR) solar-thermal electric system optimized for application to industrial and small community power plants at power levels up to 10 MW_e. Power conversion is provided by small Stirling cycle engines mounted at the focus of paraboloidal solar concentrators. The output of multiple power modules (concentrator, receiver, engine, and electric generator) is collected by means of a conventional electrical system and interfaced with a utility grid. Based on the United Stirling (Sweden) P-75 engine, a 1 MW_e system employing mass-produced components (100 000 modules/year) could produce electricity at costs competitive with those projected for electricity generated by more conventional means, eg with fossil fuels.     

The effects of distributional learning on rats' sensitivity to phonetic information.

During the first year of life, infants show decreased sensitivity to phonetic differences not used in their native language and increased sensitivity to the differences that are used. It has been shown that this change in speech perception is a function of the distributional properties of the input. The present study explores whether the mechanism responsible for the developmental changes regarding the organization of phonetic categories is a general mechanism shared with other animals. The results demonstrate that the distributional exposure to a phonetic continuum affects the subsequent discrimination of these phonemes in rats, indicating that the ability to use distributional cues to change the phonetic category structure extends beyond humans. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

High temperature processing of poly-SiC substrates from the vapor phase for wafer-bonding

The transfer by wafer-bonding of single-crystalline SiC thin films to a polycrystalline SiC substrate to obtain a “quasi-wafer” requires high quality polycrystalline substrates with controlled bulk properties (thermal conductivity, electrical resistivity) as well as with very low surface roughness (RMS < 5 nm) and bowing (< 10 μm). Currently, available polycrystalline SiC wafers are processed by sintering or by Chemical Vapor Deposition (CVD). Sintered ceramic wafers are very heterogeneous (mixture of 3C, 6H, 4H and silicon), while CVD ones are of better quality (homogeneous and textured 3C). The aim of this paper is to investigate the fabrication and the properties (bulk and surface) of SiC substrates with large (0.1 to a few mm) grains. To meet these requirements, two high temperature processes (around 2000 °C) for single crystal growth were used: Physical Vapor Transport (PVT) and the recently developed CVD Feed Physical Vapor Transport (CF-PVT). Structural investigations performed on large grain wafers sliced and polished from the grown ingots showed an important influence of the initial seed on the grain size, polytype and crystallographic texture. Chemical and Mechanical Polishing (CMP) of such structures was studied and optimized to obtain low surface roughness. The intra-grain roughness is very low (RMS < 0.5 nm) but a few nanometer of height steps were observed between grains. The relations between bulk properties, surface functionalization and process conditions are discussed. This first seeding step with commercial substrates is necessary for the creation of original substrates which can be used for the fabrication of new substrates.     

Disposition of 14C-eptifibatide after intravenous administration to healthy men

Eptifibatide, a synthetic peptide inhibitor of the platelet glycoprotein IIb/IIIa receptor, has been studied as an antithrombotic agent in a variety of acute ischemic coronary syndromes. The purpose of the present study was to characterize the disposition of 14C-eptifibatide in man after a single intravenous (i.v.) bolus dose. 14C-Eptifibatide (approximately 50 microCi) was administered to eight healthy men as a single 135-microgram/kg i.v. bolus. Blood, breath carbon dioxide, urine, and fecal samples were collected for up to 72 hours postdose and analyzed for radioactivity by liquid scintillation spectrometry. Plasma and urine samples were also assayed by liquid chromatography with mass spectrometry for eptifibatide and deamidated eptifibatide (DE). Mean (+/- SD) peak plasma eptifibatide concentrations of 879 +/- 251 ng/mL were achieved at the first sampling time (5 minutes), and concentrations then generally declined biexponentially, with a mean distribution half-life of 5 +/- 2.5 minutes and a mean terminal elimination half-life of 1.13 +/- 0.17 hours. Plasma eptifibatide concentrations and radioactivity declined in parallel, with most of the radioactivity (82.4%) attributed to eptifibatide. A total of approximately 73% of administered radioactivity was recovered in the 72-hour period following 14C-eptifibatide dosing. The primary route of elimination was urinary (98% of the total recovered radioactivity), whereas fecal (1.5%) and breath (0.8%) excretion was small. Eptifibatide is cleared by both renal and nonrenal mechanisms, with renal clearance accounting for approximately 40% of total body clearance. Within the first 24 hours, the drug is primarily excreted in the urine as unmodified eptifibatide (34%), DE (19%), and more polar metabolites (13%).