Solid Film Deposition and Non-Sacrificial Boundary Lubrication

This paper reports the results of studying various approaches in non-sacrificial boundary lubrication in which the deposition of a beneficial surface layer is the result of a chemical reaction involving one or more components in the lubricating fluid but not the metal surface itself. This is in contrast to the conventional approach which involves the rubbing surfaces as reactants with the components in the lubricant and usually promotes wear as the result of chemical change of the surfaces. The most interesting findings show that a reaction between a molybdenum complex and a mixture of zinc dialkylphosphorodithioates produced in situ deposition of MoS₂ and some other unidentified crystalline material. Effective reductions in friction and wear were obtained. Electron diffraction patterns of the worn metal surface established the presence of MoS₂.     

Finite element analysis of a single bead-on-plate specimen using SYSWELD

An uncoupled thermal and mechanical analysis has been carried out using the software code, SYSWELD in order to model a single bead-on-plate specimen. The heat source is represented by the Goldak double ellipsoid model which is available within the code. The parameters of this model were defined by the welding parameters and the macrographs and thermocouple data provided in the benchmark. The mechanical analysis is based on an isotropic hardening model which is defined by the tensile data provided in the protocol. Annealing is assumed at a temperature of 1400 °C. This paper describes the heat source fitting, the subsequent thermal and mechanical analyses and presents selected results.     

Composite chitosan and calcium sulfate scaffold for dual delivery of vancomycin and recombinant human bone morphogenetic protein-2

A biodegradable, composite bone graft, composed of chitosan microspheres embedded in calcium sulfate, was evaluated in vitro for point-of-care loading and delivery of antibiotics and growth factors to prevent infection and stimulate healing in large bone injuries. Microspheres were loaded with rhBMP-2 or vancomycin prior to mixing into calcium sulfate loaded with vancomycin. Composites were evaluated for set time, drug release kinetics, and bacteriostatic/bactericidal activity of released vancomycin, induction of ALP expression by released rhBMP-2, and interaction of drugs on cells. Results showed the composite set in under 36 min and released vancomycin levels that were bactericidal to S. aureus (>MIC 8–16 μg/mL) for 18 days. Composites exhibited a 1 day-delayed release, followed by a continuous release of rhBMP-2 over 6 weeks; ranging from 0.06 to 1.49 ng/mL, and showed a dose dependent release based on initial loading. Released rhBMP-2 levels were, however, too low to induce detectable levels of ALP in W20-17 cells, due to the affinity of rhBMP-2 for calcium-based materials. With stimulating amounts of rhBMP-2 (>50 ng/mL), the ALP response from W-20-17 cells was inhibited when exposed to high vancomycin levels (1,800–3,600 μg/mL). This dual-delivery system is an attractive alternative to single delivery or preloaded systems for bone regeneration since it can simultaneously fight infection and deliver a potent growth factor. Additionally, this composite can accommodate a wide range of therapeutics and thus be customizable for specific patient needs, however, the potential interactive effects of multiple agents must be investigated to ensure that functional activity is not altered.     

Improved ant colony optimization algorithms for determining project critical paths

In project management, a project can be represented as a network in two ways; namely, activity-on-arc (AoA) and activity-on-node (AoN). Two recent papers have shown that ant colony optimization (ACO) could find critical path(s) in projects represented as AoA networks. This paper points out that the number and placement of logical dummy activities associated with AoA-based networks can pose serious problems. To get around the problems, an ACO technique based on AoN networks is then proposed. For comparison, the two existing AoA-based ACO algorithms were reproduced and modified into AoN-based algorithms. Moreover, the proposed ACO algorithm was applied to AoA networks as well. All six algorithms were tested with several benchmark problems. The test results strongly indicate that AoN-based ACO algorithms are more effective and efficient in finding critical paths than AoA-based algorithms.     

Intracardiac catheter 2-D arrays on a silicon substrate

The design, fabrication, and characterization of a 7 MHz, two-dimensional (2-D) array transducer built on a silicon substrate is described. The array fits inside a 9-French (2.9 mm O.D.) catheter for use in real-time intracardiac volumetric imaging. The -6 dB fractional bandwidth of the transducer is 30%, the 50 /spl Omega/ pitch-catch insertion loss is 78 dB, and the interelement crosstalk is -25 dB. Realtime volumetric images in phantoms and in-vitro images of a sheep heart have been acquired yielding measured spatial resolution of 2 mm at a depth of 1 cm. The cardiac structures imaged include ventricular chambers, interventricular septum, mitral and tricuspid valves and real-time 3-D rendered volumes of the tricuspid valve in the open and closed position.     

GLUCOSE OXIDASE REACTION FOR ESTIMATION OF GLUCOSE WITHOUT HORSERADISH PEROXIDASE. SOME MICROBIOLOGICAL AND FERMENTATION APPLICATIONS

An enzymic method has been developed for analysis of glucose. Glucose oxidase acts on glucose to produce hydrogen peroxide which acts to directly reduce the green Cu(II) 2–2′-bicinchoninate complex to a violet complex without horseradish peroxidase. A concentration range of 20–200 μM glucose was used but the reaction shows a linear range of 20–800 μM glucose. Interference is controlled by using a blank determination which has not been treated with glucose oxidase. The reaction has been used to estimate glucose levels in Saccharomyces cerevisiae fermentation and α-amylase, invertase and β-galactosidase reactions and coloured corn-steep fermentation media.     

POEMS syndrome in a patient with diabetic ketoacidosis: case report and review

This article summarise the main data in the literature on the role of bacteriological contamination of the dialysate fluid in inflammatory reactions in hemodialysis. Pyrogenic substances of small molecular weight from Gram-negative bacteria grown in dialysate can pass across intact dialyzer membrane to stimulate cytokine production by peripheral blood mononuclear cells. Cellulosic hemodialysis membranes are more permeable to endotoxins than synthetic membranes. Polysulfone membranes and polyamide membranes are able to adsorb bacterial toxins on the dialysate side. The diffusive transfer of bacterial products across dialysis membrane from dialysate fluid was demonstrated. Transmembrane passage of cytokine-inducing bacterial products across reprocessed dialyzers is greater than across new dialyzers. Bacteriological contamination of the dialysate fluid is a problem which must be considered with much more care by nephrologists, especially as LAL test is unable to detect all the bacterial products which can contaminate the dialysate fluid.     

Metal ion and guanine nucleotide modulations of agonist interaction in G-protein-coupled serotonin1A receptors from bovine hippocampus

1. The serotonin type 1A (5-HT1A) receptors are members of a superfamily of seven transmembrane domain receptors that couple to GTP-binding regulatory proteins (G-proteins). We have studied the modulation of agonist binding to 5-HT1A receptors from bovine hippocampus by metal ions and guanine nucleotide. 2. Bovine hippocampal membranes containing the 5-HT1A receptor were isolated. These membranes exhibited high-affinity binding sites for the specific agonist [3H]OH-DPAT. 3. The agonist binding is inhibited by monovalent cations Na+, K+, and Li+ in a concentration-dependent manner. Divalent cations such as Ca2+, Mg2+, and Mn2+, on the other hand, show more complex behavior and induce enhancement of agonist binding up to a certain concentration. The effect of the metal ions on agonist binding is strongly modulated in the presence of GTP-gamma-S, a nonhydrolyzable analogue of GTP, indicating that these receptors are coupled to G-proteins. 4. To gain further insight into the mechanisms of agonist binding to bovine hippocampal 5-HT1A receptors under these conditions, the binding affinities and binding sites have been analyzed by Scatchard analysis of saturation binding data. Our results are relevant to ongoing analyses of the overall regulation of receptor activity for G-protein-coupled seven transmembrane domain receptors.