Selenide layers on gallium ARSENIDE (100): Chemical reactions and electronic passivation

The passivation of GaAs (100) surfaces by Se and ZnSe has been investigated using soft X-ray photoelectron spectroscopy and low energy electron diffraction. An interface layer is identified which reflects a compound of gallium and selenium and it is shown that GaSe is consistent with the data. The mechanism whereby band bending is removed is also considered.     

New concept in coronary angioplasty: dilatation with a helical balloon that allows simultaneous autoperfusion

OBJECTIVE: This study was done to determine whether retrograde delivery of cardioplegic solution provides uniform blood flow to the myocardium supplied by an occluded coronary artery and whether it maintains myocardial energy levels beyond the coronary occlusion. METHODS: Isolated pig hearts were used. A hydraulic occluder was placed at the origin of the left anterior descending coronary artery. The perfusion pressure for retrograde delivery of cardioplegic solution was controlled at 40 to 50 mm Hg. Magnetic resonance imaging and localized 31P magnetic resonance spectroscopy were used to assess myocardial perfusion and energy metabolism, respectively. RESULTS: Magnetic resonance perfusion images (n = 7) showed that the perfusion defect that occurred during antegrade delivery of cardioplegic solution (as a result of the occlusion of the left anterior descending coronary artery) resolved during retrograde delivery of cardioplegic solution. Retrograde perfusion delivered similar amounts of flow to the jeopardized myocardium as it did to other areas of the myocardium. However, the distribution of cardioplegic solution by the retrograde route was heterogeneous (cloudlike) across both ventricular walls. 31P magnetic resonance spectra showed that the ischemic changes induced by occlusion of the left anterior descending artery during antegrade perfusion were greatly alleviated by retrograde perfusion; however, it took longer for retrograde cardioplegia (n = 7, 17.08 minutes) to restore the levels of inorganic phosphate/phosphocreatine relative to the effect of releasing the left anterior descending artery occluder during antegrade delivery of cardioplegic solution (n = 7, 5.3 minutes). CONCLUSIONS: First, retrograde delivery of cardioplegic solution provides sufficient flow to the myocardium beyond a coronary occlusion to maintain near normal levels of energy metabolites, and second, the efficacy of the retrograde route of cardioplegic solution delivery (in terms of distribution of the solution and rate of myocardial energy recovery) is significantly lower than that of the antegrade route.     

Position statement: single-dose activated charcoal. American Academy of Clinical Toxicology; European Association of Poisons Centres and Clinical Toxicologists

In preparing this Position Statement, all relevant scientific literature was identified and reviewed critically by acknowledged experts using agreed criteria. Well-conducted clinical and experimental studies were given precedence over anecdotal case reports and abstracts were not usually considered. A draft Position Statement was then produced and subjected to detailed peer review by an international group of clinical toxicologists chosen by the American Academy of Clinical Toxicology and the European Association of Poisons Centres and Clinical Toxicologists. The Position Statement went through multiple drafts before being approved by the boards of the two societies and being endorsed by other societies. The Position Statement includes a summary statement for ease of use and is supported by detailed documentation which describes the scientific evidence on which the Statement is based. Single-dose activated charcoal should not be administered routinely in the management of poisoned patients. Based on volunteer studies, the effectiveness of activated charcoal decreases with time; the greatest benefit is within 1 hour of ingestion. The administration of activated charcoal may be considered if a patient has ingested a potentially toxic amount of a poison (which is known to be adsorbed to charcoal) up to 1 hour previously; there are insufficient data to support or exclude its use after 1 hour of ingestion. There is no evidence that the administration of activated charcoal improves clinical outcome. Unless a patient has an intact or protected airway, the administration of charcoal is contraindicated.     

Noncontinent urinary diversion

When the need for urinary diversion arises, whether from carcinoma of the urinary tract, malfunction, or malformation, a decision must be made about the type of diversion to be performed. Currently, the patient and surgeon must decide on continent versus noncontinent versus neobladder, and on the type of intestinal segment to be used.     

Bench-scale evaluations and mechanistic studies of intumescent/fire-protective coatings for polyvinyl chloride nitrile rubber

The object of this study was to identify, for future large-scale testing, and adequate fire-protective coating for the substrate, polyvinyl chloride (PVC) nitrile rubber (MIL-P-15280 Rev H). Fifteen fire protective coatings which included ten intumescent, two ablatives, two fire retardants and one photon diffusive coatings were evaluated using bench-scale thermal insults. To discern the possible mechanism(s) whereby the coatings offer fire protection, the effect of radiant heat versus the flame source employed was investigated and thermogravimetric analysis (TGA) of the neat coatings was performed. In selected cases, the effect of coating thickness and repeatability of the results were evaluated. The differences in coating effectiveness, and the varied repeatability in three of the four cases examined, focus on the inherent complexity of intumescence, as well as on the importance of scaled-up testing of coatings that appeared promising. Thermogravimetric analyses of the coatings indicate that two selected TGA measurements/parameters, when used in conjunction, appear useful in characterizing mechanistic differences between the less effective and more effective coatings. Based on the rigorous criterion adopted, one candidate (a water-based intumescent coating at 100 mil (2.54 mm) thickness) appears promising for the substrate, PVC nitrile rubber. Its effectiveness is attributable to it exhibiting good insulative and re-radiative properties and an apparent low susceptibility to crack formation.     

Analysis of lipidation of recombinant Lyme vaccine protein (rOspA) by electrospray mass spectroscopy

Lipidation at the N-terminal of recombinant outer surface protein A (rOspA) is an important determinant of its immunogenicity. Lipidation patterns of rOspA can be sensitive to processing environments and storage conditions. In order to assure product consistency and stability. it is essential to characterize and monitor lipidation patterns of rOspA through its life-cycle. Electrospray mass spectroscopy combined with maximum entropy calculation was employed to analyze the lipidation of rOspA. The results revealed that more than 90% of protein is a tri-lipidated rOspA and the remainder is di-lipidated. It was demonstrated that the method is both sensitive and quantitative and has the potential to be used for routine quality control and stability testing.     

In Vitro Characterization of Polymeric Membrane used for Controlled Release Application

The application of a polymer film coat is a common practice in the preparation of controlled release dosage forms. In vitro characterization of the polymeric membrane is essential for optimization of the membrane formulation. Polymers selected in this study were cellulose acetate (CA), ethylcellulose (EC) and copolymers of acrylic and methacrylic esters (Eudragit RL100). Plasticizers used in this study were dibutyl sebacate (DBS), triethyl citrate (TEC) and triacetin. Polymer dispersions containing different plasticizers were cast into membranes on a tefloncoated plate. The resulting membranes were evaluated for permeability and mechanical properties. Membrane permeability was determined by quantifying the transport of a model drug, theophylline, across a circular polymeric membrane mounted in a thermostatted, twocompartment horizontal diffusion cell. Mechanical properties of the membranes, such as tensile strength, percent elongation and modulus of elasticity, were determined using an Instron 4301. The results of this study indicate that the CA and EC membranes were found to be effective in preventing the diffusion of theophylline. The addition of Eudragit RL100 to the CA or EC membranes increased the permeability but decreased the mechanical strength of the resulting membrane(s). A significant increase in permeability was observed at a CA:Eudragit RL100 ratio of 60:40. This could be explained by a change in the mechanism of drug transport, principally from partitioning into the membrane to diffusing through the liquidfilled pores of the resulting membrane(s). The results of the mechanical deformation studies indicate that triacetin has a greater potential for partitioning into the CA polymer than does TEC or DBS. DBS has a greater potential for partitioning into the EC polymer than does TEC or triacetin. The addition of Eudragit RL100 to the CA membrane(s) caused a significant decrease in the tensile strength, percent elongation and modulus of elasticity, thus resulting in weaker and softer membranes. The results indicate that the test methods employed were sufficiently sensitive to quantify the test parameters for the changes in membrane compositions which could provide valuable information for optimization of the membrane formulation.     

Daily repetitive transcranial magnetic stimulation (rTMS) improves mood in depression

Converging evidence points to hypofunction of the left prefrontal cortex in depression. Repetitive transcranial magnetic stimulation (rTMS) activates neurons near the surface of the brain. We questioned whether daily left prefrontal rTMS might improve mood in depressed subjects and report a pilot study of such treatment in six highly medication-resistant depressed inpatients. Depression scores significantly improved for the group as a whole (Hamilton Depression Scores decreased from 23.8 +/- 4.2 (s.d.) at baseline to 17.5 +/- 8.4 after treatment; t = 3.03, 5DF, p = 0.02, two-tailed paired t-test). Two subjects showed robust mood improvement which occurred progressively over the course of several weeks. In one subject, depression symptoms completely remitted for the first time in 3 years. Daily left prefrontal rTMS appears to be safe, well tolerated and may alleviate depression.     

Vortex core size in submonolayer superfluid4He films

The superfluid transition of⁴He films adsorbed on 500 Å diameter slip-cast alumina powder is measured with a torsion oscillator technique for films with transition temperatures between 50 and 700 mK. The transitions are found to be controlled by the universal Kosterlitz- Thouless critical line, but a strong increase in the broadening of the transition is observed for the thinnest films. Analysis in terms of vortex pair excitations shows that this broadening results from a vortex core size that increases rapidly as the film is thinned, scaling roughly with the interparticle spacing of the superfluid submonolayer. Third sound modes are identified in the dissipation, in addition to a broad peak from the vortex unbinding. This system provides evidence of a three-dimensional superfluid transition mediated by vortex excitations.