Microstructure and Mechanical Properties of Rapidly Solidified Hypereutectic Al–Si and Al–Si–Fe Alloys

The microstructure and mechanical properties of rapidly solidified Al–18 wt% Si and Al–18 wt% Si–5 wt% Fe alloys were investigated by a combination of optical microscopy, scanning electron microscopy, transmission electron microscopy, x-ray diffraction, tensile testing, and wear testing. The centrifugally atomized binary alloy powder consisted of the -Al (slightly supersaturated with Si) and Si phases and the ternary alloy powder consisted of the -Al (slightly supersaturated with Si), silicon, and needle-like metastable Al–Fe–Si intermetallic phases. During extrusion the metastable -Al₄FeSi₂ phase in the as-solidified ternary alloy transformed to the equilibrium -Al₅FeSi phase. The tensile strength of both the binary and the ternary alloys decreased with a high-temperature exposure, but a significant fraction of the strength was retained up to 573 K. The specific wear gradually increased with increasing sliding speed but decreased with the addition of 5 wt% Fe to the Al–18 wt% Si alloy. The wear resistance improved with annealing due to coarsening of the silicon particles.     

Should benefit-risk ratio of the intramuscular vitamin K be reevaluated in newborn infants?

AIM: To compare the pharmacokinetics after po different doses of beta-carboxyethylgermanium sesquioxide (Ge-132). METHODS: An atomic absorption spectrophotometric system was used to measure germanium concentrations in plasma and urine samples after po Ge-132 1 (low dose, LD), 2.5 (medium dose, MD), and 4 (high dose, HD) g.m-2 in 24 healthy volunteers (one dose per 8 subjects). RESULTS: T1/2 alpha (LD, 1.2 +/- 0.7 h; MD, 1.1 +/- 0.6 h; HD, 1.2 +/- 0.5 h), T1/2 beta (LD, 5.2 +/- 1.2 h; MD, 5.8 +/- 2.5 h; HD, 5.5 +/- 1.4 h) and Cl/F (LD, 33 +/- 12 L.h-1; MD, 35 +/- 10 L.h-1; HD, 33 +/- 11 L.h-1) were not dose-related. Tmax was between 0.75 h and 2 h. Cmax (LD, 5.3 +/- 2.2 mg.L-1; MD, 13 +/- 5 mg.L-1; HD 18 +/- 8 mg.L-1, HD) and AUC (LD, 31 +/- 13 mg.h.L-1; MD, 60 +/- 16 mg.h.L-1; HD, 79 +/- 42 mg.h.L-1) were positive correlation to the dose of Ge-132. Urine-eliminated germanium within 24 h accounted for 11 +/- 3% of LD, 9 +/- 3% of MD, and 6 +/- 5% of HD (calculated from Ge/F) and showed a negative correlation to the dose. CONCLUSION: 1) Intracorporal process of Ge after po Ge-132 coincided with the first-order absorption and elimination with two-compartment kinetic model; 2) The amount of germanium eliminated in urine was below 11%.     

Reexpansion pulmonary edema occurring after thoracoscopic drainage of a pleural effusion

Video assisted thoracoscopic drainage and tale pleurodesis was used to treat a recurrent pleural effusion in a 60 year-old woman undergoing major gynecologic surgery. She developed reexpansion pulmonary edema immediately following surgery. Several important risk factors that were present in this patient are discussed. In addition to almost, complete collapse of the underlying lung for several weeks, thoracoscopy resulted in manipulations and rapid re-inflation of the underlying lung, which further increased the risk to the patient.     

Effect of IciA protein on the expression of the nrd gene encoding ribonucleoside diphosphate reductase in E. coli

BACKGROUND AND AIMS OF THE STUDY: This study investigated the efficacy of postoperative ticlopidine as antiplatelet therapy in patients shortly after heart valve repair or replacement. METHODS: Between 1990 and 1995, 235 consecutive patients underwent either valve repair (n = 67) or replacement with a bioprosthesis (n = 168). The bioprostheses used were Carpentier-Edwards porcine or pericardial (n = 158) valves, Prima stentless valves (n = 3) and cryopreserved homografts (n = 7). Types of repair were aortic (one), mitral annuloplasty with Carpentier ring (65) and tricuspid repair (one). Mean patient age was 67 (range: 16 to 83) years for valve replacement and 57 (range: 32 to 74) years for repair (p < 0.01). Atrial fibrillation occurred in 34% of patients. The hospital mortality rate was 11% (26 patients). Of the 209 survivors, 137 were assigned to antiplatelet treatment with ticlopidine for the first three months of follow up. The other 72 received either oral anticoagulation (coumadin; n = 40), aspirin (n = 14) or no medication (n = 18). In 15 patients, ticlopidine treatment was interrupted due to diarrhea (13 cases), mild allergic reaction (one) or anemia (one). The mean follow up was 3.2 years (range: 1 month to 6 years); cumulative follow up was 684 patient-years (pt-yr) and was complete in 96% of cases. RESULTS: There were two episodes of thromboembolism in the ticlopidine group at 1 month and 6 months respectively, with a linearized incidence of 0.5% pt-yr. In the coumadin group there were four episodes of thromboembolism, three within the first three months of follow up. The linearized incidence was 3% pt-yr (p < 0.01). There were three episodes of hemorrhage in the ticlopidine group in the first three months of follow up and one in the coumadin group. The linearized incidence was 0.75% pt-yr. CONCLUSIONS: Following heart valve repair or replacement with a bioprosthesis, the first three months is a high-risk period for thromboembolism. Ticlopidine seems to prevent this complication better than conventional therapy with oral anticoagulants. Nevertheless, hemorrhage continues to be a problem with ticlopidine therapy.     

Cerebral blood flow in hypertensive patients: an initial report of reduced and compensatory blood flow responses during performance of two cognitive tasks

We asked whether the altered cerebral vasculature associated with essential hypertension might dampen or redirect the regional cerebral blood flow (rCBF) response to cognitive work. Relative rCBF was assessed with [(15)O]water positron emission tomography during a working memory task, a memory span task, and two perceptual control tasks. Unmedicated hypertensive patients and control subjects differed in rCBF response during both memory tasks. Hypertensives showed relatively diminished rCBF responses in right hemisphere areas combined with compensatory activation of homologous areas in the left cerebral cortex. Essential hypertension appears to selectively influence the circulatory reserve of portions of cerebral cortex and secondarily induce recruitment of other cortical areas to process certain tasks.     

Gallbladder varices: diagnosis in children with portal hypertension on duplex sonography

Vascular dementia is actually considered as a ill-defined entity. The clinical and neuropathologic criteria of this multifactorial disorder remain uncertain. Although not widely accepted, the introduction of the concept of incomplete infarction in the brain can help to explain some particular types of vascular dementia. In the hypoxic-hypoperfusion dementia syndromes of cerebral cortex and white matter and in lacunar state dementia, which are the most common types of vascular dementia, areas of incomplete infarction co-exist with regions of complete infarction. Although initially rejected by early positron emission tomographic studies, it can now be demonstrated that these incomplete infarction areas reflect chronic ischaemia of the brain and that they are relevant to the pathogenesis of vascular dementia.