The early stages of oxidation of ion-implanted nickel at high temperature

The early stages of oxidation of nickel implanted with nickel, chromium, or lithium ions in oxygen at 1100°C have been studied using various electron-optical techniques. The unimplanted metal develops initially a fine-grained, convoluted scale having a ridged, cellular structure. Subsequently, the oxide grains increase in size significantly and oxidation becomes predominantly controlled by diffusion of Ni ²⁺ ions across a compact, columnar scale. Implantation of the surface with nickel ions has no significant effect on the initial oxidation behavior. However, after implantation with chromium or lithium ions, the development of the NiO scale is, in the early stages of oxidation, suppressed by formation of NiCr ₂O₄ or LiO₂ nodules, respectively. Subsequently, the implanted species are incorporated into the steady-state NiO scale where they dope the oxide and thus influence the diffusion rate of Ni ²⁺ ions through it. As would be predicted, the steady-state oxidation rate of chromium-implanted nickel is increased while that of lithium-implanted nickel is decreased compared with that of the unimplanted metal.     

Colostral immunoglobulin transfer in calves II. The rate of absorption

The rate and pattern of colostral immunoglobulin absorption, based upon increase in concentration of immunoglobulin in serum in calves, has been determined from the interaction of three factors: starting age of colostral feeding, amount of colostrum fed, and time after feeding. All immunoglobulin classes show common characteristics of absorption following a rapid transfer during the first 4 h after feeding. An analysis of three-dimensional response surface for each of the three immunoglobulin classes indicated positive linear trend in the amount fed up to 2 liters. Rates of absorption in succeeding time periods following the initial feeding had decreasing linear trends. That is, age at first feeding had an inverse effect on rate of absorption. A linear-by-linear interaction between amount fed and starting age as shown for all three classes. Only immunoglobulin IgM had a significant quadratic response for amount fed. Concentration of immunoglobulin in the pooled colostrums fed had no influence on rate of absorption. Evidence is that 2 liters of colostrum fed to Holstein calves may be optimum in the range studied for maximum pinocytotic activation of absorptive cells and maximum rate of absorption.     

The influence of oxides on the friction and wear of alloys

Development of compacted oxides, particular y so-called ‘glazes’, on sliding metal and alloy surfaces can result in significant decreases in friction coefficients and wear rates. This paper describes how such ‘glazes’ can form on many alloys under a wide range of sliding conditions. ‘Glazes’ consist of very fine, compacted, crystalline particles of almost any oxide or oxides. Formation of the oxide, the subsequent development of the ‘glaze’, and the mechanisms by which the ‘glaze’ reduces friction and wear are discussed     

Effect of stress on blood leucocyte and milk somatic cell counts in dairy cows.

Blood and milk samples from Holstein cows were examined for total blood leucocyte count, differential blood leucocyte count, milk quality test, and somatic cell count in milk while the cows were stressed by corticotropin injection, confinement in a heat-humidity chamber, or environmental-heat stress by exposure during the hot summer months of June through November in southern Arizona. All three stressing conditions resulted in a moderate blood leucocytosis. Modest increases in somatic cell counts of milk were associated with corticotropin injection and environmental-heat stress. Positive correlations were recorded between blood leucocytes and somatic cell counts of milk in mastitis-free cows injected with corticotropin and between percent blood neutrophils and somatic cell counts of milk in environmental-heat stressed cows with no evidence of current mastitis.     

Fretting-induced damage between contacting steel-polymer surfaces

Fretting between steel components may be reduced by inserting a polymer layer between the components, or by using a polymer as a replacement for one metal component. This paper describes the wear behaviour, in a fretting situation, of several polymers and relates the damage inflicted on the carbon steel counterface to properties of the polymer which depend on its surface energetics     

The tensile straining of oxidized Fe-Cr-Al-Y alloys

The apparent tensile fracture strains, at which cracking of α-Al₂O₃ scales formed on Fe-Cr-Al-Y alloys during oxidation in 1 atm oxygen at 1200 °C occur, have been determined by two methods at room temperature. The values are reproducible and depend on the oxidation time but are within the range 1.4% to 2.3%. These are significantly higher than other published values for thermally formed oxides. It has also been observed that an intermediate thermal cycle to room temperature during the oxidation period does not affect significantly the subsequently measured fracture strain. These relatively high values are discussed in terms of two tentative hypotheses, one relating to flaws in the oxide, the other to possible loss of cohesion of oxide which is too fine to be detected by the methods used.     

High-Temperature Corrosion of Iron–Chromium Alloys in Oxidizing–Chloridizing Conditions

An investigation has been carried out into the effects of 0.1 to 1.0% HCl onthe oxidation of Fe–28%Cr and Fe–28%Cr–1%Y inargon–20%O₂ at 600 and 700°C. At the higher temperature,the additions of HCl to the gas caused considerable increases in corrosionof the binary alloy, with the rates of metal loss actually being greaterthan those of iron in the 0.5 and 1% HCl-containing environments. Thick andmultilayered scales were observed; these were oxides, particularlyFeCr₂O₄ and Fe₂O₃, that developedfollowing formation and vapor phase transport of chlorine-containing speciesfrom the metal surface. The main metal-loss processes were evaporation ofFeCl₂, CrCl₂, and CrO₂Cl₂, withthe first two of these reacting with oxygen to form solid oxides in thescale, while the third was lost mainly to the environment. The addition of1% Y to the alloy resulted in a marked improvement in corrosion resistanceat 700°C, because of the reactive element facilitating rapidestablishment of a protective Cr₂O₃-rich layer andpromoting the formation of condensed chlorides rather than the more volatileCrO₂Cl₂ phase. At 600°C, additions of HCl toargon–20%O₂ caused formation of some localized condensedchlorides on both alloys, but the corrosion rates were relatively low,because of protection by a Cr₂O₃-rich oxide scale.     

Key Technologies for Next-Generation Terrestrial Digital Television Standard DVB-T2

A new platform for HDTV transmissions, in the form of a new-generation terrestrial digital video broadcasting standard (DVB-T2), has been developed by the DVB Project and will be published by the European Telecommunications Standards Institute. A number of technical innovations have been included in DVB-T2 to boost throughput and ruggedness, enhance single-frequency network coverage, and ease both transmitter and receiver implementation. This article starts from the motivations that led the DVB project to create the new standard and then surveys the key technologies behind DVB-T2, including the LDPC/BCH forward error correction scheme, transmission scheduling, orthogonal frequency-division multiplexing with huge block size, multiple-antenna transmissions, and synchronization techniques. A comparison with the current DVB-T standard is also provided, showing that DVB-T2 is able to increase the payload throughput and allows HDTV transmission with current network planning.     

Report of the Second Equine Leucocyte Antigen Workshop, Squaw valley, California, July 1995

The final assignment of antibody clusters for leucocyte antigens and immunoglobulins, as described in detail in Sections 3 and 4, is summarized in Table 4. Together with other mAbs developed outside of ELAW II (Table 9) this pool of reagents represent a powerful array of tools for the study of equine immunity. The Second Equine Leucocyte Antigen Workshop made considerable advances in pursuing the objectives of establishing the specificities of mAbs and achieving consensus on the nomenclature for equine leucocyte and immunoglobulin molecules. Of equal importance, several productive collaborations were fostered among the participating laboratories and observers. Overall, enormous advances have been made in the past decade since mAbs specific for equine leucocyte antigens and immunoglobulins were first reported. There remains enormous scope and need for further studies of equine leucocyte antigens and immunoglobulins, both for the purposes of comparative immunology and for the good of the horse. In the future novel techniques will be required to develop reagents for specific target antigens such as the orthologues of the CD25 or CD45 isoforms. In studies of equine immunoglobulins the functional role of the IgG isotypes must be better established, reagents for IgE must be developed, and cloning of the immunoglobulin heavy chain genes will be essential if the complexities of the IgG sub-isotypes are to be elucidated. The tasks still facing the currently small group of equine immunologists throughout the world remain formidable, and will only be tackled successfully in a spirit of collaboration.     

v-representability for noninteracting systems

The Epstein-Barr virus (EBV) induces unlimited growth of B lymphocytes in vitro, a phenomenon known as immortalization. The elucidation of the mechanisms by which EBV de-regulates B-cell proliferation in vitro will permit an understanding of how the virus contributes in vivo to the genesis of Burkitt's lymphoma (BL) and of lymphoproliferations in immunosuppressed patients. At present, no single EBV immortalizing gene has been identified, and the hypothesis has been made that many viral genes cooperate in establishing an autocrine loop of secretion leading to immortalization. Constitutive expression of B-cell surface molecules such as CD21 and CD23, specifically implicated in the control of B-cell proliferation, is indeed induced at the surface of immortalized B lymphocytes. The expression of the viral nuclear antigen 2 (EBNA2) has been shown to be in part responsible for CD21 and CD23 up-regulation, and EBNA2 is suspected to be a transactivator of cellular genes, although this point remains to be demonstrated. The role of EBNA2 gene, independently of other viral genes, has been investigated by transfection into B-lymphoma lines, but conflicting results have been reported. To further investigate its role in the regulation of CD21 and CD23 molecules, we have compared the effects of EBNA2 expression in 2 sets of B-lymphoma lines infected with P3HR1 EBV strain, and/or transfected with EBNA2 gene. We report here that: (i) EBNA2 expression is not a sufficient condition to induce CD21 and CD23 upregulation, EBNA2's effects are highly dependent on the cellular context, and moreover can be modified by infection with P3HR1 virus; (ii) EBNA2 induces activation of CD23 expression in a very particular way, namely, an increased quantity of CD23 steady-state RNA coding for the form A of the protein, which is not detectable at the cell surface but directly secreted.