Evolution of solidification texture during additive manufacturing.

Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six <100> preferred growth directions in face centered cubic alloys. Therefore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numerical modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components.

Pulsed laser deposition of hydroxyapatite thin films on Ti-6Al-4V: effect of heat treatment on structure and properties.

Hydroxyapatite (HA) is an attractive biomaterial that has been widely used as a coating for dental and orthopedic metal implants. In this work, HA coatings were deposited on Ti-6Al-4V substrates by laser ablation of HA targets with a KrF excimer laser. Deposition was performed at ambient temperature under different working pressures that varied from 10(-4) to 10(-1) torr of oxygen. The as-deposited films were amorphous. They were annealed at 290-310 degrees C in ambient air in order to restore the crystalline structure of HA. The coatings morphology, composition and structure were investigated by scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction techniques. Mechanical and adhesive properties were examined using nanoindentation and scratch tests, respectively. The stability of the HA coatings was tested under simulated physiological conditions. This study reveals that the combination of pulsed laser deposition and post-deposition annealing at 300 degrees C have the potential to produce pure, adherent, crystalline HA coatings, which show no dissolution in a simulated body fluid.

Identification of a 60-kD antigen associated with malignant growth of human breast tissue.

Antisera against a novel 60-kD antigen (P60) were developed using immunomasking strategy which shows malignant growth-related expression in human breast cancer tissue. Cell adhesion assay in the presence of P60 antibody clearly indicates a role for P60 directly or indirectly in adhesion of tumor cells to extracellular matrix protein vitronectin. These results indicate that P60 could be a potential marker to distinguish benign from malignant growth of human breast tissue, and that P60 could be an integrin or a non-integrin receptor, or a receptor-related protein to vitronectin.

Pethidine, metoclopramide and the gastro-oesophageal sphincter. A study in healthy volunteers.

The effects of intramuscular pethidine (1.0--3.0 mg/kg) followed by metoclopramide 10 mg intravenously, and those of a combination of pethidine 1.5 mg/kg and metoclopramide 10 mg given intramuscularly, on the lower oesophageal sphinct pressure have been studied manometrically in human volunteers. In the former group, the mean effect of all the doses of pethidine was a reduction of the lower oesophageal barrier pressure by 6.8 cmH2O from control values (p less than 0.0002), while the intravenous administration of metoclopramide resulted in a mean increase in barrier pressure of 8.75 cmH2O above the depressed level (p less than 0.0001). Following the combination of pethidine and metoclopramide given intramuscularly depression of the sphincter pressure was not totally prevented, but there was a reduction in its incidence and severity. It is suggested that pethidine is likely to increase the possibility of gastro-oesophageal reflux, and that metoclopramide is a useful adjunct in the prevention of reflux in preparation for, and after, surgery in patients who have been given pethidine for pain relief.

Inadvertent intra-arterial injection of thiopentone.

A case is recorded in which intra-arterial injection of thiopentone 2.5 per cent was made into an aberrant branch of the radial artery at the lateral aspect of the wrist. Although the intra-arterial injection of thiopentone is a fairly uncommon accident, especially on the dorsum of the hand, nevertheless, precautions should always be taken to avoid it. These precautions should include palpating for a pulse before application of a tourniquet and after removal of the tourniquet, and checking for backflow of blood after insertion of the cannula. The anaesthetist should always have a high index of suspicion, should use a vessel which is significantly remote from any palpable pulse and should always pause after a test dose of one or two ml of thiopentone solution to ensure that the injection is not uncomfortable. Some of the anatomical abnormalities to be found in the arterial supply to the forearm and hand have been described, and the immediate and late treatment of accidental arterial injection of thiopentone has also been detailed.

Laryngoscope blade with suction unit.

A laryngoscope blade incorporating a suction tube is described. Blood or secretions are automatically aspirated from the pharynx when the blade is inserted.