Plasma-Assisted Nitriding of Aluminum-Alloy Parts

Plasma-assisted nitriding of aluminum alloys promises to become a suitable alternative to variants of thermochemical treatment used for raising the wear resistance of these materials especially from the standpoint of the environmental effect. Process performed in vacuum with the use of nitrogen and an argon-hydrogen mixture as the process gas provides for the formation of a layer of compounds (aluminum nitrides) with enhanced hardness on various aluminum alloys. However, until the present the process has been used only at the laboratory scale. No data can be found in the literature, for example, on the effect of the batch size on the uniformity of the thickness of the nitrided layer or on the wear resistance of parts from aluminum alloys. The present work is a study of plasma-assisted nitriding of commercially produced parts (pistons) fabricated from an aluminum alloy. The parameters of the process are chosen after the determining optimum conditions for preliminary sputtering treatment. Special attention is devoted to provision of temperature uniformity within a batch and the possibility of improving the surface quality by increasing the thickness of the compound layer. The topography of the surface and the thickness, chemical composition, and hardness of the compound layer are studied by the methods of scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), metallography, and measurement of ultramicrohardness. The performance characteristics of untreated, nitrided, and anodized pistons are evaluated with the help of vibration wear tests with a rider fabricated from a standard material. The results of the tests show that the wear resistance of some nitrided pistons is comparable to that of anodized parts.     

Codistribution of procathepsin B and mature cathepsin B forms in human prostate tumors detected by confocal and immunofluorescence microscopy

Ascorbic acid can recycle alpha-tocopherol from the tocopheroxyl free radical in lipid bilayers and in micelles, but such recycling has not been demonstrated to occur across cell membranes. In this work the ability of intracellular ascorbate to protect and to recycle alpha-tocopherol in intact human erythrocytes and erythrocyte ghosts was investigated. In erythrocytes that were 80% depleted of intracellular ascorbate by treatment with the nitroxide Tempol, both 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) and ferricyanide oxidized alpha-tocopherol to a greater extent than in cells not depleted of ascorbate. In contrast, in erythrocytes in which the intracellular ascorbate concentration had been increased by loading with dehydroascorbate, loss of alpha-tocopherol was less with both oxidants than in control cells. Protection against AAPH-induced oxidation of alpha-tocopherol was not prevented by extracellular ascorbate oxidase, indicating that the protection was due to intracellular and not to extracellular ascorbate. Incubation of erythrocytes with lecithin liposomes also generated an oxidant stress, which caused lipid peroxidation in the liposomes and depleted erythrocyte alpha-tocopherol, leading to hemolysis. Ascorbate loading of the erythrocytes delayed liposome oxidation and decreased loss of alpha-tocopherol from both cells and from alpha-tocopherol-loaded liposomes. When erythrocyte ghosts were resealed to contain ascorbate and challenged with free radicals generated by AAPH outside the ghosts, intravesicular ascorbate was totally depleted over 1 h of incubation, whereas alpha-tocopherol decreased only after ascorbate was substantially oxidized. These results suggest that ascorbate within the erythrocyte protects alpha-tocopherol in the cell membrane by a direct recycling mechanism.     

Proze\modell zur Untersuchung einer Induktivität für Gleichstromsteller

This paper describes the analysis of inductances, carrying a triangular current. Such inductances are used in the field of power electronics for buck- and boost-converters. Since the layout of such a coil requires either laborious numerical simulations or comprehensive practical experiences, a reduced process model is derived in this case which allows estimations with sufficient exactness and a sufficient variety of parameters. Based on the electromagnetic field distribution in the inductance the given geometry is reduced gradually in a way that the field distribution changes only insignificantly, however, calculation is becoming easier. The resulting reduced process model allows calculation of the electric field parameters by means of an analytical relation, which makes it easier to examine the dissipation power of different variants. Finally, the process model is used for optimization.     

Microcomputers Implementation of Digital Control Strategies for Structural Response Reduction

Abstract: In the past, implementation of active structural control strategies employing PC-based hardware has often been problematic, and there seems to be a need to improve the understanding of the issues associated with implementation of digital control, as well as to reduce the excessive computational times required for I/O processes and calculation of control forces. Recently developed hardware based on dedicated digital signal processing (DSP) chips has offered new possibilities for control algorithm implementation. This paper discusses digital control system concepts and specific practical aspects of digital control implementation, including the use of supervision. Details regarding active structural control using the Texas Instruments TMS32OC30 DSP chip and experimental verification of the hardware performance are given.     

Randbedingungen für Prozeßmodelle bei hochfrequenten Wirbelstromproblemen

Übersicht Bei der Entwicklung von Prozeßmodellen für hochfrequente Wirbelstromprobleme stellt sich die Frage nach Randbedingungen, die den Einfluß von leitenden permeablen Räumen erfassen. In der vorliegenden Arbeit wird eine solche Randbedingung für geschichtete Medien hergeleitet und auf ihre Genauigkeit hin untersucht. Dabei wird ein Weg aufgezeigt, der Berechnungen beliebig oft geschichteter Materialien erlaubt.

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Boundary conditions in process modells for high-frequency eddy current problems

Contents In the development of process modells for high-frequency eddy current problems, boundary conditions have to be chosen, which take into account the influence of conductivity and permeability for the calculation of the external fields. In the present paper a boundary condition for layered materials is derived and its accuracy is investigated.

     

Interaction between thiol-modifying agents and P1075, a K(ATP) channel opener, in rat isolated aorta

In the past year progress in the study of cationic species has been made, particularly in our understanding of the factors which control the selective recognition of biologically important cations such as ammonium, alkali and alkaline earth metal ions, and of metal ions used in biomedicine such as lanthanides and iron(III). Based on this knowledge, several new hosts with improved transport, photophysical and biological properties have been designed.     

Utility of a nitric oxide electrode for monitoring the administration of nitric oxide in biologic systems

Von Hippel-Lindau (VHL) disease is an inherited autosomal dominant neoplastic disorder causing central nervous system haemangioblastomas. The VHL gene (3p25-3p26) is known to be a tumour suppressor gene, with its inactivation being responsible for a predisposition to tumour development. As far as we know, the present report of VHL disease manifestation in identical twins is unique. Genetic inquiry into the family background did not reveal this disease among their progenitors. For presymptomatic diagnosis of 17 presently unaffected family members, constitutional DNA of the twins was screened for VHL germline mutations, using loss of heterozygosity studies and exon-specific DNA sequencing. To determine the influence of somatic mutations of the VHL gene in tumourigenesis, DNA of five surgically removed intracerebral haemangioblastomas of the identical twins was analyzed in comparison with their constitutional DNA by DNA sequencing of the complete VHL coding region. However, no allelic losses were found for the VHL gene or for various other tumour suppressor genes (p53, BRCA1, BRCA2, DCC, and MCC). Furthermore, no mutations were found in the constitutional DNA of either twin sister or in the DNA of all five tumour lesions. Based on our observations, we conclude that in certain VHL families, presymptomatic molecular diagnosis of the disease is not feasible and requires close clinical surveillance of all individuals at risk.     

The Bender Gestalt: Use of clinical judgment versus recall scores in prediction of Huntington's disease.

Used Bender-Gestalt recall scores and clinical evaluation of Bender protocols to predict organicity in 2 comparisons in a total of 89 Ss: normals vs premorbids for Huntington's disease and normals vs Ss already affected with Huntington's disease (mean ages, 31 yrs for normals and premorbids and 38 yrs for Huntington's Ss). Mean Bender recall scores significantly discriminated between normals and premorbids. Chi-squares reflecting predictive accuracy were significant for both comparisons using the Bender recall score but were nonsignificant for the predictions by clinical evaluations. Hit rates for the recall score prediction, however, were not much better than those for the clinical evaluation method and were too low for diagnostic evaluation of individual cases. (PsycINFO Database Record (c) 2010 APA, all rights reserved)