Modifying the properties of AISI 316L steel by glow discharge assisted low-temperature nitriding and oxynitriding

Apart from titanium, its alloys and CoCrMo alloys, austenitic steels are widely used in medical applications. In order to improve the frictional wear resistance of these steels, they are subjected to various surface treatments such that the good corrosion resistance of the steels is preserved.The paper analyzes the structure and phase composition of AISI 316L steel after subjecting it to low-temperature nitriding and oxynitriding under glow discharge conditions. The treatments produced diffusion-type surface layers composed of nitrogen-expanded austenite (known as the phase S, i.e. supersaturated solution of nitrogen in austenite) with a thin surface layer of chromium nitride (CrN) zone (after nitriding) or chromium oxide (Cr₂O₃) zone (after oxynitriding). It has been shown that the treatments substantially increase the hardness and frictional wear resistance of the steel without degrading its good corrosion resistance (examined in the Ringer physiological solution at a temperature of 37 °C).     

Similarity preservation in default logic

The paper identifies a problem in default reasoning in Reiter’s Default Logic and related systems: elements which are similar given the axioms only, become distinguishable in extensions. We explain why, sometimes, this is considered undesirable. Two approaches are presented for guaranteeing similarity preservation: One approach formalizes a way of uniformly applying the defaults to all similar elements by introducing generic extensions, which depend only on similarity types of objects. According to the second approach, for a restricted class of default theories, a default theory is viewed as a “shorthand notation” to what is “really meant” by its formulation. In this approach we propose a rewriting of defaults in a form that guarantees similarity preservation of the modified theory. It turns out that the above two approaches yield the same result. This revised version was published online in June 2006 with corrections to the Cover Date.     

Role of metabolism by esterase and cytochrome P-450 in cocaine-induced suppression of the antibody response

To investigate the role of metabolism in cocaine-induced immunosuppression, diazinon and beta-ionone were administered as an esterase inhibitor and a cytochrome P-450 (P-450) inducer, respectively, to B6C3F1 female mice. When 10 or 30 mg/kg of diazinon was administered 30 min before cocaine (30 mg/kg) was administered i.p. for 7 consecutive days, the suppression of the T-dependent antibody response to sheep red blood cells was potentiated greatly when compared to the suppression by cocaine alone. Spleen and thymus weights were decreased significantly and serum glutamate-pyruvate transaminase activities were elevated dramatically when cocaine and diazinon were administered together. beta-Ionone was administered s.c. for 7 consecutive days and the P-450 activities were determined 3 days after the last administration. beta-Ionone induced cocaine N-demethylation, which is the first step in the activation of cocaine to the metabolites capable of producing hepatotoxicity, as well as P-450IA1- and P-450IIB1-specific monooxygenases. The inductive effects of beta-ionone on P-450IA1/2 and P-450IIB1/2 proteins were confirmed by using Western immunoblotting with selective monoclonal antibodies. In addition, when beta-ionone (600 mg/kg) was administered with cocaine for 7 days, the suppression of the antibody response was potentiated greatly, thymus weight was decreased significantly and serum glutamate-pyruvate transaminase was elevated. Our present results suggest that inhibition of the esterase pathway of cocaine shunts the metabolism of cocaine into an immunotoxic pathway, and that the metabolism of cocaine by P-450 may be the critical pathway for the generation of the metabolites capable of suppressing the antibody response.     

Bile duct variations in partial liver transplantations from living-related donors

The aim of this paper was to present anatomic variations of bile ducts and their effect on the perioperative course of living-related donors in partial liver transplantations in children. Liver fragments for partial transplantation were harvested from 41 related donors. Segments II and III were harvested from 35 and segments II, III, and IV from 6 donors. During the procedure, cholangiography through cystic duct was performed revealing a normal anatomy of the bile ducts in 33 (80.5%) cases. The rest of the donors showed anatomic variations. There was only one case of complications related to the bile duct. The intraoperative diagnosis of anatomic variations allowed for safe partial liver harvesting.     

Thermovoltaic effect in polycrystalline samarium sulfide

A thermovoltaic effect has been observed for the first time in a polycrystalline sample of samarium sulfide (SmS) with artificially created concentration gradient of excess (overstoichiometric) samarium ions, in which an electric voltage of 12–22.5 mV was generated in a temperature interval of 370–485 K. It is shown that the specific voltage generation in SmS due to the thermovoltaic effect can be observed in a temperature range of 100–1800 K.     

Modeling damage and load redistribution in composites under tension–tension fatigue loading

A fatigue model developed for composite laminates and based on the cycle-by-cycle probability of failure has been modified to account for damage creation and evolution and its effect on cycles to failure. The residual strength of different parts of the laminate is determined during cyclic loading and damage such as matrix cracking is quantified along with its effect on load redistribution and cycles to failure of different parts of the laminate. The model does not require any curve fitting or experimentally measured data other than basic material static strength values and their associated experimental scatter. The model is applied to uni-directional and cross-ply laminates. A stress-based approach using energy minimization and calculus of variations is used. The model predictions range from fair to excellent.     

NUMERICAL INVESTIGATION OF JET IMPINGEMENT WITH CROSS FLOW—COMPARISON OF YANG-SHIH AND STANDARD k–ϵ TURBULENCE MODELS

ABSTRACT

Computational fluid dynamics models are used to predict the heat transfer distribution on a smooth surface under an array of angled impinging jets. The three-dimensional numerical models simulate impingement with cross flow in one direction. Jet angle is varied between 30°, 60°, and 90° as measured from the smooth flat impingement surface. Conjugate conduction in the heated boundary is included in the analysis. Two turbulence models are examined, the standard k–? model and the Yang-Shih model. Local and average heat transfer coefficients are compared with test data for 30 test cases. The Yang-Shih model was able to predict average Nusselt number within 2–30%. The standard k–? model predicts average Nusselt number with 0 to nearly 60% error.