The effect of (Ti + Al): V ratio on the structure and oxidation behaviour of TiAlN/VN nano-scale multilayer coatings

Nano-scaled multilayered TiAlN/VN coatings have been grown on stainless steel and M2 high speed steel substrates at U-B = - 85 V in an industrial, four target, Hauzer HTC 1000 coater using combined cathodic steered arc etching/unbalanced magnetron sputtering. X-ray diffraction (XRD) has been used to investigate the effects of process parameters (Target Power) on texture evolution (using texture parameter T*), development of residual stress (sin(2) psi method) and nano-scale multilayer period. The composition of the coating was determined using energy dispersive X-ray analysis. The thermal behaviour of the coatings in air was studied using thermo-gravimetric analysis, XRD and scanning electron microscopy. The bi-layer period varied between 2.8 and 3.1 nm and in all cases a {1 1 0} texture developed with a maximum value T* = 4.9. The residual stress varied between -5.2 and -7.4 GPa. The onset of rapid oxidation occurred between 628 and 645 degreesC depending on the (Ti+Al):V ratio. After oxidation in air at 550 degreesC AlVO4, TiO2 and V2O5 Phases were identified by XRD with the AlVO4, TiO2 being the major phases. The formation of AlVO4 appears to disrupt the formation of Al2O3 which imparts oxidation resistance to TiAlN based coatings. Increasing the temperature to 600 and 640 degreesC led to a dramatic increase in the formation of V2O5 which was highly oriented (0 0 1) with a plate-like morphology. At 640 degreesC there was no evidence of the coating on XRD. Increasing the temperature to 670 degreesC led to further formation of AlVO4 and a dramatic reduction in V2O5. (C) 2003 Elsevier B.V. All rights reserved

Tribological properties of unbalanced magnetron sputtered nano-scale multilayer coatings TiAlN/VN and TiAlCrYN deposited on plasma nitrided steels

Unbalanced magnetron sputtered multilayer coatings TiAlN/VN and TiAlCrYN grown on pulse plasma nitriding pre-treated low alloy steel P20 have been characterised by using X-ray diffraction (XRD), scanning electron microscope (SEM), micro-indentation, scratch and pin-on-dise wear tests. A 160-mu m-thick nitrided case was formed on the steel surface containing a pure Fe3N and Fe4N compound layer and showing hardness up to 8.5 GPa, which led to improved load bearing ability and adhesion behaviour of the coating-substrate system. The coatings deposited on non-nitrided P20 showed poor adhesion and severe cracking and spalling wear. In contrast, the TiAlN/VN and TiAlCrYN deposited on nitrided substrates showed only mild polishing and oxidation wear mechanisms and extremely low wear coefficients in the scales of 10(-17) and 10(-16) m(3) N-1 m(-1), respectively. In drilling solution treated 304 austenite stainless steel, the TiAlN/VN-coated drills showed a lifetime 50% longer than TiAlN-coated drills. Plasma nitriding pre-treatment led to further increases of lifetime by 33%. (c) 2004 Elsevier B.V. All rights reserved

From the Feynman-Schwinger representation to the non-perturbative relativistic bound state interaction

We write the 4-point Green function in QCD in the Feynman-Schwinger representation and show that all the dynamical information are contained in the Wilson loop average. We work out the QED case in order to obtain the usual Bethe-Salpeter kernel. Finally we discuss the QCD case in the non-perturbative regime giving some insight in the nature of the interaction kernel.Comment: 25 pages, RevTex, 3 figures included, typos corrected, to appear in Phys. Rev. D 5

Initial activation of EpCAM cleavage via cell-to-cell contact

<p>Abstract</p> <p>Background</p> <p>Epithelial cell adhesion molecule EpCAM is a transmembrane glycoprotein, which is frequently over-expressed in simple epithelia, progenitors, embryonic and tissue stem cells, carcinoma and cancer-initiating cells. Besides functioning as a homophilic adhesion protein, EpCAM is an oncogenic receptor that requires regulated intramembrane proteolysis for activation of its signal transduction capacity. Upon cleavage, the extracellular domain EpEX is released as a soluble ligand while the intracellular domain EpICD translocates into the cytoplasm and eventually into the nucleus in combination with four-and-a-half LIM domains protein 2 (FHL2) and β-catenin, and drives cell proliferation.</p> <p>Methods</p> <p>EpCAM cleavage, induction of the target genes, and transmission of proliferation signals were investigated under varying density conditions using confocal laser scanning microscopy, immunoblotting, cell counting, and conditional cell systems.</p> <p>Results</p> <p>EpCAM cleavage, induction of the target genes, and transmission of proliferation signals were dependent on adequate cell-to-cell contact. If cell-to-cell contact was prohibited EpCAM did not provide growth advantages. If cells were allowed to undergo contact to each other, EpCAM transmitted proliferation signals based on signal transduction-related cleavage processes. Accordingly, the pre-cleaved version EpICD was not dependent on cell-to-cell contact in order to induce <it>c-myc </it>and cell proliferation, but necessitated nuclear translocation. For the case of contact-inhibited cells, although cleavage of EpCAM occurred, nuclear translocation of EpICD was reduced, as were EpCAM effects.</p> <p>Conclusion</p> <p>Activation of EpCAM's cleavage and oncogenic capacity is dependent on cellular interaction (juxtacrine) to provide for initial signals of regulated intramembrane proteolysis, which then support signalling via soluble EpEX (paracrine).</p

Spectrum and Variability of Mrk501 as observed by the CAT Imaging Telescope

The CAT Imaging Telescope has observed the BL Lac object Markarian 501 between March and August 1997. We report here on the variability over this time including several large flares. We present also preliminary spectra for all these data, for the low emission state, and for the largest flare.Comment: 4 pages, 4 figures, Late

Poorly cytotoxic terminally differentiated CD56(neg)CD16(pos) NK cells accumulate in Kenyan children with Burkitt lymphomas

Natural killer (NK) cells are critical for restricting viral infections and mediating tumor immunosurveillance. Epstein-Barr virus (EBV) and Plasmodium falciparum malaria are known risk factors for endemic Burkitt lymphoma (eBL), the most common childhood cancer in equatorial Africa. To date, the composition and function of NK cells have not been evaluated in eBL etiology or pathogenesis. Therefore, using multiparameter flow cytometry and in vitro killing assays, we compared NK cells from healthy children and children diagnosed with eBL in Kenya. We defined 5 subsets based on CD56 and CD16 expression, including CD56(neg)CD16(pos) We found that licensed and terminally differentiated perforin-expressing CD56(neg)CD16(pos) NK cells accumulated in eBL children, particularly in those with high EBV loads (45.2%) compared with healthy children without (6.07%) or with (13.5%) malaria exposure (P = .0007 and .002, respectively). This progressive shift in NK cell proportions was concomitant with fewer CD56(dim)CD16(pos) cells. Despite high MIP-1beta expression, CD56(neg)CD16(pos) NK cells had diminished cytotoxicity, with lower expression of activation markers NKp46, NKp30, and CD160 and the absence of TNF-alpha. Of note, the accumulation of poorly cytotoxic CD56(neg)CD16(pos) NK cells resolved in long-term eBL survivors. Our study demonstrates impaired NK cell-mediated immunosurveillance in eBL patients but with the potential to restore a protective NK cell repertoire after cancer treatment. Characterizing NK cell dysfunction during coinfections with malaria and EBV has important implications for designing immunotherapies to improve outcomes for children diagnosed with eBL

Observation of the Crab Nebula Gamma-Ray Emission Above 220 Gev by the Cat Cherenkov Imaging Telescope

The CAT imaging telescope, recently built on the site of the former solar plant Themis (French Pyrenees), observed gamma-rays from the Crab nebula from October 1996 to March 1997. This steady source, often considered as the standard candle of very-high-energy gamma-ray astronomy, is used as a test-beam to probe the performances of the new telescope, particularly its energy threshold (220 GeV at 20 degrees zenith angle) and the stability of its response. Due to the fine-grain camera, an accurate analysis of the longitudinal profiles of shower images is performed, yielding the source position in two dimensions for each individual shower.Comment: 5 pages, 3 figures, Tex, contribution to 25th ICRC Durba

Detection of Vhe Gamma-Rays from MRK 501 with the Cat Imaging Telescope

The CAT imaging telescope on the site on the former solar plant Themis has been observing gamma-rays from Mrk501 above 220 GeV in March and April 1997. This source is shown to be highly variable and the light curve is presented. The detected gamma-ray rate for the most intense flare is in excess of 10 per minute.Comment: 5 pages, 4 figures, Tex, contribution to 25th ICRC Durba