Coupled effects of ion beam chemistry and morphology on directed self-assembly of epitaxial semiconductor nanostructures.

We study the coupled effects of ion beam chemistry and morphology on the assembly of templated epitaxial nanostructures. Using a focused ion beam (FIB) system equipped with a mass-selecting filter, we pattern Si substrates with local ion doses of Si, Ge and Ga to control subsequent Ge(x)Si(1 - x) epitaxial nanostructure assembly. This capability to employ different templating species allows us to study how different incorporated ion species in the near surface region affect the ability to localize nucleation during subsequent epitaxial growth. Our results indicate that FIB-directed self-assembly is a complex process, dependent on dose-induced morphology in addition to ion-specific chemical effects.

Comparative issues in aviation and surgical crew resource management: (1) are we too solution focused?

Although the published work in health care increasingly promotes aviation as a high-reliability industry to be emulated, there is little empirical research to justify equating the dynamics of health care's operating environment with that of aviation. This article examines some of the potential key areas of difference between the two professional groups with respect to crew resource management. The risks of implementing crew resource management training in health care without an evidential basis are discussed.

Primary brain myxoma, an unusual tumor of meningeal origin: case report.

OBJECTIVE AND IMPORTANCE: Primary myxoma of the central nervous system is an extremely rare tumor arising from cells of primitive mesenchymal origin. Only two cases of primary intracranial myxoma have been described previously. We report a patient with a primary myxoma originating from the right frontoparietal convexity dura, which we studied in detail with diagnostic imaging and pathological analysis. CLINICAL PRESENTATION: A female adolescent presented to the emergency department with a 3-day history of mild headache, abdominal pain, and intermittent left-sided focal motor seizures. Neurological examination was remarkable for left leg hyperreflexia and difficulty with tandem gait. Cranial computed tomography and magnetic resonance imaging demonstrated an inhomogeneously enhancing mass in the right frontoparietal region. INTERVENTION: A right frontoparietal craniotomy was performed. During surgery, a tumor appearing similar to a typical convexity meningioma was completely removed along with the dural attachment. CONCLUSION: The patient had an uneventful recovery and returned to normal activity. Primary intracranial myxoma should be distinguished from other meningeal tumors and metastatic cardiac myxoma by appropriate pathological analysis and cardiac evaluation. A circumscribed myxoma completely excised with adequate dural margin carries a good prognosis for surgical cure.

Aviation Human Factors: Strategies for Enhancing Airline Safety

No abstract available.

A survey of moyamoya disease in Hawaii.

Moyamoya disease (MMD) is a rare entity in the US with a few retrospective series and sporadic cases reported in the US and North America. Although it is known that MMD exists in all races, there is a predilection for people of Asian origin. Because of the relatively high percentage of Asians living in Hawaii, it was hypothesized that the estimated prevalence of MMD would be higher in Hawaii than the remaining US. All practicing neurologists, neurosurgeons, neuroradiologists and major hospitals in Hawaii were surveyed for MMD patients treated during the past 10 years. Medical records and angiograms (when available) were reviewed and the diagnostic guidelines for MMD from the Ministry of Health and Welfare of Japan applied. There were 53 records reviewed in 42 patients; 21 fulfilled the criteria for definite Moyamoya disease which were the focus of this study. In Hawaii, the prevalence of MMD was higher in patients of Japanese descent compared to Caucasians (P = 0.012) and higher than in the remaining US (P < 0.001). Non-Japanese Asians and Pacific Islanders had a higher incidence of MMD than Caucasians that was not statistically significant. There was no difference in MMD among Japanese living in Hawaii or Japan. Males had an equal percentage of hemorrhage and infarcts; females tended to have a higher incidence of ischemic events rather than hemorrhage. Age and sex distribution of our series were similar to larger reported MMD studies. Our results suggest that: (1) Moyamoya disease in Hawaii has a higher incidence and prevalence than the rest of the US, largely due to the larger percentage of Asians, particularly Japanese, living in Hawaii; and (2) genetic rather than environmental factors may explain the increased MMD in Hawaii.

Enzymes of glucose metabolism in cultured human gliomas: neoplasia is accompanied by altered hexokinase, phosphofructokinase, and glucose-6-phosphate dehydrogenase levels.

The enzymes of glycolysis and selected enzymes of the pentose phosphate pathways were measured by fluorometric methods in extracts prepared from cultures of normal cortical human astrocytes and from cultures derived from low-grade (II) or high-grade (IV) gliomas. The hexokinase and phosphofructokinase levels of the low-grade glioma-derived line were not significantly different from those of the normal astrocyte cultures. However, the activities of hexokinase and phosphofructokinase were consistently and significantly increased in the high-grade glioma-derived lines. The activity of glucose-6-phosphate dehydrogenase was significantly decreased in all glioma-derived lines and by more than 90% in the high-grade-derived lines. Other enzymes of the glycolytic pathway were not significantly different from those of normal astrocytes, or they showed a variation inconsistently related to the neoplastic state. Glucose flux is not apparently regulated to a significant degree of hexokinase in glioma-derived lines, since the measured Vmax values are in substantial excess over the measured flux rates. Reversible binding of hexokinase to the particulate fraction was observed in both the normal astrocytes cultures and the high-grade glioma-derived lines. A twofold displacement of particulate hexokinase by ATP, ADP, 1-O-methylglucose, sorbitol-6-phosphate, and dibutyryl cyclic AMP was observed in the high-grade glioma-derived lines. The degree of displacement by various agents and the basal ratio of free/bound was not significantly different between the transformers and the nontransformants. The hexokinase from both the gliomas and the normal astrocytes was noncompetitively inhibited by the glucose analogue 2-deoxy-d-glucose. Phosphofructokinase activity is close to the observed glucose flux rates in both the normal astrocyte and the glioma-derived cultures. The phosphofructokinase activity of normal astrocytes is activated twofold or more by ADP, AMP, fructose-2,6-diphosphate, and Pi. However, these same ligands activate phosphofructokinase by less than twofold in a typical high-grade glioma-derived line. ATP, dibutyryl cyclic AMP, and citrate inhibit glioma and normal astrocytic phosphofructokinase, but the magnitude of the inhibition is much less than in the glioma-derived lines.

Machete wounds to the head: report of three cases.

Three cases of machete wounds to the head are described. The resulting injuries from this unusual mode of trauma varied in severity and included transection of a previously placed ventriculoperitoneal shunt. Complications of these injuries resulted from delayed and inadequate treatment.

Glucose metabolism in human gliomas: correspondence of in situ and in vitro metabolic rates and altered energy metabolism.

The rates of disappearance of glucose from the medium of 13 human glioma-derived cell lines and one cultured of normal human cortical astrocytes were determined by fluorometric techniques. High-grade glioma-derived cultures showed a range of glucose consumption between 1 and 5 nmol/min/mg protein. Normal astrocyte cultures and cultures derived from grades I-III gliomas had a glucose consumption rate of 2-3 nmol/min/mg protein. Seven high-grade glioma lines were derived from surgical samples taken from patients who had been scanned by 18F-2-deoxy-d-glucose positron computed tomography. The rate of glucose consumption in these high-grade glioma-derived lines was close to the maximum local cerebral metabolic rate for glucose (LCMRglc) measured in situ in the tumors from which the cultures were derived. In cultured glioma-derived lines, approximately one-half of the glucose consumed was recovered as lactate and pyruvate, suggesting a reliance of glioma cells on aerobic glycolysis. ATP and phosphocreatine (PCr) levels were variable in the glioma-derived lines, and ATP was lower in the glioma-derived lines than in the normal astrocytes. Levels and regulation of glycogen differed significantly among the various glioma-derived cell lines. Glycogen content did not diminish as glucose was consumed, suggesting that glycogen utilization is not tightly regulated by the glucose metabolic rate. These results suggest that human glioma-derived cell cultures (1) adequately reflect the metabolic capacity of gliomas in situ and (2) are significantly altered in several aspects of their glycolytic metabolism.

Regulation of hexokinase in cultured gliomas.

Positron emission computed tomographic (PECT) scanning studies have demonstrated that high grade gliomas exhibit increased 2-[18F]fluoro-2-deoxyglucose (18FDG) uptake compared to cerebral white matter and low grade gliomas. Hexokinase catalyzes the phosphorylation of glucose, as well as 18FDG and 2-deoxyglucose (2DG), thereby "trapping" these slowly metabolized analogues intracellularly. We hypothesize that a similar hexokinase-mediated uptake of glucose and glucose analogues occurs in vitro. Hexokinase activity was assayed in homogenates of tissue-cultured lines derived from high (IV) and low (II) grade gliomas and in fibroblasts derived from skin. With glucose as substrate, the maximal activity (Vmax) in the Grade IV lines was 200% of the activity found in the Grade II line, fibroblasts, and astrocytes; however, the Michaelis substrate affinity constant (Km) bore no relationship to tumor grade. With 2DG as substrate, the Vmax of all cell lines decreased, but the Grade IV lines still tended to have greater activity than the others. The Km values for 2DG were 5 times higher than those for glucose. Hexokinase is found in two subcellular compartments: an active form reversibly bound to mitochondria and a less active, cytosolic form. Up to 20% of the total hexokinase was found in the cytosol in all lines tested. High energy phosphate compounds (ATP, ADP, CTP, and others) displaced mitochondria-bound hexokinase, which increased the cytosolic form by 2-fold in the glioma lines, but fibroblast hexokinase distribution was unaffected. Our results suggest that: (a) high grade gliomas have increased hexokinase activity, which may explain the grade-related differences in 18FDG uptake observed by PECT scanning, and (b) human glioma hexokinases may be regulated by reversible subcellular compartmentation.

Protein diffusion coefficient measurements by laminar flow analysis: method and applications.

Laminar flow in an open tube leads to solute band spreading. This process is opposed by radial diffusion. The translational diffusion coefficient of a solute can be calculated from the band dispersion, tube length, and flow rate. No calibration is necessary. A simple apparatus was used to measure the diffusion coefficients of several small solutes and 18 proteins. Most results were within +/- 10% of literature values. Each determination required 7-90 min, depending on the magnitude of the diffusion coefficient. The amount of protein needed was approximately 25 micrograms. The diffusion coefficient data were useful for the estimation of molecular weights.

The effect of lice infestation on the growth of Hereford calves.

Two experiments were carried out to examine the effects of cattle lice on the productivity of young calves. In both experiments the main species present was Linognathus vituli. In the first experiment, treatment of grazing heifers and their suckled calves did not improve the overall bodyweight gain of either the heifers or the calves. The calves experienced a rapid build-up in lice populations during autumn and early winter which was associated with mild transient pathogenic effects, but this was followed by an apparent 'self-cure' reaction and compensatory gain during late winter. In the second experiment young calves were placed in feedlots and fed high and low planes of nutrition. Treatment to remove lice did not result in any improvements in growth rate on either plane of nutrition; however it was clear that untreated, undernourished calves had heavier lice infestation.

Role of chronic low-level lead exposure in the aetiology of mental retardation.

Water-lead levels were measured in the homes occupied during the first year of life by 77 mentally retarded children aged two to six years and 77 non-retarded matched controls, and in the homes occupied by their mothers during pregnancy. The water-lead content was significantly higher in the retarded group, and the probability of mental retardation was significantly increased when water lead exceeded 800 mug. per litre. Blood-lead levels were also significantly higher in the retarded group. It is concluded that lead contamination of water may be one factor in the multifactorial aetiology of mental retardation and that every effort should be made to reduce the lead content of drinking-water.