Exposures to patient and personnel in computed axial tomography

Distribution of radiation exposure circumcranially for patients undergoing brain scanning with EMI computed tomographic equipment was measured using thermoluminescent dosimeters. The exposures are found to lie in the range of 1-5 R depending on position relative to tube motion. The maximum exposure of 5 R in CT scanning lies between the estimated exposure of 1.2 R for skull radiography and approximately 10 R for angiographic examination. Measured exposures are reported corresponding to locations of the patients' eyes, thyroid, chest and gonads, and at various locations in the vicinity of the unit.     

A Novel Bilateral Power Conversion Scheme for Variable Frequency Static Power Supplies

PWM voltage source inverters (VSI's) supplied from diode rectifiers are employed with most of today's static power supplies for variable frequency ac type loads. This method generates nonsinusoidal input and output voltage/current waveforms and yields poor system reliability. An upgraded method of power conversion is presented that eliminates both problems. In addition, it allows bidirectional power flow which improves efficiency and simplifies cooling requirements. The subject method requires a PWM rectifier and a PWM current source inverter. Advanced PWM techniques employed with both static Converters allow the minimization of all associated passive components.     

The Delta Modulation Technique in Static PWM Inverters

Pulsewidth modulation (PWM) techniques are employed in voltage-source inverters to produce a variable output voltage containing the least possible harmonic distortion over a wide frequency range. To achieve these objectives, compromises are made in terms of control circuit complexity, smoothness of inverter operation, and overall system reliability. The delta modulation (DM) technique fulfills the aforementioned performance requirements with a minimum of circuit complexity, smooth inverter operation and with improved system reliability.     

Tilt table testing in the evaluation and management of athletes with recurrent exercise-induced syncope

The development and application of a highly sensitive double-target fluorescence in situ hybridization (FISH) method in combination with immunohistochemistry for detection of chromosome 1 abnormalities in interphase nuclei of neuroblastoma samples is reported. An alpha-satellite probe specific for chromosome 1 and a VNTR probe that hybridizes to chromosome band 1p36.3 were hybridized to GD2 prestained neuroblastoma cells in double-target FISH experiments. The ratio of intact to deleted chromosome 1 homologs in the neuroblastoma cells was assessed. To demonstrate the reliability of the method described, four selected samples derived from different neuroblastoma stages are presented. FISH results correlated well with data obtained by conventional cytogenetic procedures. The technique described allows sensitive detection of chromosome 1 abnormalities in interphase nuclei and enables partial cytogenetic analysis of nondividing cells with a defined immunological phenotype.     

Loss of CD4+ T cells in human immunodeficiency virus type 1-infected chimpanzees is associated with increased lymphocyte apoptosis

Supportive evidence that apoptosis contributes to loss of CD4+ lymphocytes in human immunodeficiency virus type 1 (HIV-1)-infected humans comes from an apparent lack of abnormal apoptosis in apathogenic lentivirus infections of nonhuman primates, including HIV-1 infection of chimpanzees. Two female chimpanzees were inoculated, one cervically and the other intravenously, with HIV-1 derived from the LAI/LAV-1b strain, which was isolated from a chimpanzee infected with the virus for 8 years. Within 6 weeks of infection, both recipient chimpanzees developed a progressive loss of CD4+ T cells which correlated with persistently high viral burdens and increased levels of CD4+ T-cell apoptosis both in vitro and in vivo. Lymph nodes from both animals also revealed evidence of immune hyperactivation. Intermediate levels of T-cell apoptosis in both peripheral blood and lymph nodes were seen in a third chimpanzee that had been infected with the LAI/LAV-1b strain for 9 years; this animal has maintained depressed CD4/CD8 T-cell ratios for the last 3 years. Similar analyses of cells from 4 uninfected animals and 10 other HIV-1-infected chimpanzees without loss of CD4+ cells revealed no difference in levels of apoptosis in these two control groups. These results demonstrate a correlation between immune hyperactivation, T-cell apoptosis, and chronic loss of CD4+ T cells in HIV-1-infected chimpanzees, providing additional evidence that apoptosis is an important factor in T-cell loss in AIDS. Furthermore, the results show that some HIV-1 strains are pathogenic for chimpanzees and that this species is not inherently resistant to HIV-1-induced disease.     

A high pressure single-pass high-conversion electrochemical cell for intensification of organic electrosynthesis processes

The anode oxidation of 4-methoxytoluene (4-MT) to 4-methoxybenzyl dimethylacetal (4-MBDMA) in methanol is used as a test reaction for the study of a microchannel electrochemical reactor operated continuously in a single-pass high-conversion mode. The cell consists of two stainless steel cathodes, grooved with 100 μm deep channels surrounding a flat glassy carbon anode. Pressures up to 20 bars are applied in the cell in order to reduce the volumetric flow rate of the cathodically produced hydrogen. Both the narrow gap and the operation under pressure lead to an enhancement of the electrolytic conductivity of the cell and make it possible to operate with concentrated solutions, with high current densities and with a very low supporting electrolyte concentration (i.e. 0.01 M KF).The cell performance is discussed in terms of cell voltage, reactant conversion, material and current efficiency and finally selectivity in 4-MBDMA. The effect of inlet reagent concentration, pressure, flow-rate and temperature are investigated. Best performance is obtained with 0.5 M 4-MT at 5 bars and 45 °C: for a 90% conversion, selectivity and current efficiency attain, respectively, 92% and 85%. The high pressure, single-pass high-conversion cell exhibits in this case a space time yield 5–10 times higher than the current industrial process, with a significantly lower concentration of the supporting electrolyte.     

Performance and Analysis of Stack Junctionless Tunnel Field Effect Transistor

Silicon - To overcome the fabrication complexity and achieve a better switching ratio is a major grave concern for applications in semiconductor devices. In this regards, a novel stack gate-oxide...