Informed consent in Texas: a proposal for reasonableness and predictability.
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Thomson Thick X-Ray Absorption in a Broad Absorption Line Quasar, PG 0946+301.
We present a deep ASCA observation of a broad absorption line quasar (BALQSO) PG 0946+301. The source was clearly detected in one of the gas imaging spectrometers, but not in any other detector. If BALQSOs have intrinsic X-ray spectra similar to normal radio-quiet quasars, our observations imply that there is Thomson thick X-ray absorption (NH greater, similar1024 cm-2) toward PG 0946+301. This is the largest column density estimated so far toward a BALQSO. The absorber must be at least partially ionized and may be responsible for attenuation in the optical and UV. If the Thomson optical depth toward BALQSOs is close to 1, as inferred here, then spectroscopy in hard X-rays with large telescopes like XMM would be feasible.
Journal Article↗
Summary of measurements of high-LET particle radiation in U.S. manned space missions.
A summary of measurements of high-LET particle radiation inside U.S. manned spacecraft is given for ASTP (Apollo Soyuz Test Project), Skylab and Apollo missions. The results include particle fluxes, integral LET spectra, and stopping-density charge distributions derived from measurements made in plastic nuclear track detectors worn by astronauts and located at various positions inside spacecraft. The results presented for different missions cover a wide range of shielding depth and missions type.
Astronauts↗
Modelling radiation loads to detectors in a SNAP mission.
In order to investigate the degradation of optical detectors of the Supernova Acceleration Project (SNAP) space mission because of irradiation, a three-dimensional model of the satellite has been developed. A realistic radiation environment at the satellite orbit, including both galactic cosmic rays and cosmic ray trapped in radiation belts, has been taken into account. The modelling has been performed with the MARS14 Monte Carlo code. In a current design, the main contribution to dose accumulated in the photo-detectors is shown to be due to trapped protons. The contribution of primary alpha particles is estimated. Predicted performance degradation for the photodetector for a four-year space mission is 40% and this can be reduced further by means of shielding optimisation.
Alpha Particles↗
Flux of high-LET cosmic-ray particles in manned space flight.
On the Apollo and Skylab missions the high energy heavy ion (HZE) flux was measured by means of plastic nuclear track detectors. Measurements involve the fluxes of high linear energy transfer (LET), 6 < or approximately Z < or approximately 26 particles incident on astronauts and on several biological experiments. Partial results of these measurements are presented; the effects of shielding and solar modulation are discussed.
Collodion↗
Investigation of circular asymmetry in cancer mortality of Hiroshima and Nagasaki A-bomb survivors.
Data on Hiroshima and Nagasaki A-bomb survivors are used to investigate, for each city, possible circular asymmetry in cancer mortality around the hypocenter. Using the Cox regression method and controlling for age ATB, sex, followup year, distance from the hypocenter, and type of shielding, it is found that in Hiroshima cancer mortality was significantly higher in the westerly direction from the hypocenter. Mortality from stomach cancer, leukemia, and colon cancer were higher in the westerly direction. In Nagasaki, only lung cancer exhibited circular asymmetry, and was significantly higher in the westerly direction. For various reasons, the results tend to support the possibility of an asymmetry in radiation dose in Hiroshima, but not in Nagasaki. Also, possible asymmetry in nondose variables associated with cancer is suggested in both cities, particularly in variables associated with lung cancer. Indications for future work and implications for future dose-mortality investigations are discussed.
Age Factors↗
Planar positron imaging of rubidium-82 for myocardial infarction: a comparison with thallium-201 and regional wall motion.
Rubidium-82 (Rb-82) is a generator-produced, short half-life (76 seconds) positron emitting potassium analog. Using a mobile gamma camera equipped with a rotating tungsten collimator and high-energy shielding, we examined the use of Rb-82 in the coronary care unit and clinical laboratory for detection of perfusion defects due to myocardial infarction. We studied 31 subjects, 10 patients with acute myocardial infarction, 12 with remote myocardial infarction, and nine controls. Rb-82 images were compared with Tl-201 and regional wall motion for detection of infarct-related arteries. Of the 22 patients with myocardial infarction, 16 were identified with Rb-82 and Tl-201. In nine control subjects, eight were normal with each method. Correlation between Rb-82 and Tl-201 defect scores was excellent. Sensitivity and specificity for infarct-related arteries were similar for Rb-82, Tl-201, and wall motion imaging. Thus planar Rb-82 imaging can detect MI reliably in the coronary care unit and in the clinical laboratory.
Coronary Care Units↗
The surgical pathology and cytopathology of US Persian Gulf War military veterans.
BACKGROUND: Tens of thousands of Persian Gulf War veterans (GWVs) have presented with medical symptoms since Operation Desert Shield and Operation Desert Storm. The Kuwait Registry at the Armed Forces Institute of Pathology was established to act as a repository for surgical pathology, cytopathology, and autopsy material from GWVs. OBJECTIVE: To identify conditions known to be endemic to the theater of operations in our cohort of GWVs. METHODS: The Kuwait Registry database was searched by computer for listed conditions endemic to the Persian Gulf region included in the registry through December 31, 1997. RESULTS: Of the 2582 patients in this cohort, 1 patient with hepatitis B and 15 patients with hepatitis C were identified. Other known endemic conditions of the Persian Gulf region were not found. CONCLUSIONS: Viral hepatitis (B and C), which is prevalent in the US population, was the only listed endemic condition identified in surgical pathology or cytopathology specimens in our cohort of GWVs.
Adult↗
SemiSPECT: a small-animal single-photon emission computed tomography (SPECT) imager based on eight cadmium zinc telluride (CZT) detector arrays.
The first full single-photon emission computed tomography (SPECT) imager to exploit eight compact high-intrinsic-resolution cadmium zinc telluride (CZT) detectors, called SemiSPECT, has been completed. Each detector consists of a CZT crystal and a customized application-specific integrated circuit (ASIC). The CZT crystal is a 2.7 cm x 2.7 cm x -0.2 cm slab with a continuous top electrode and a bottom electrode patterned into a 64 x 64 pixel array by photolithography. The ASIC is attached to the bottom of the CZT crystal by indium-bump bonding. A bias voltage of -180 V is applied to the continuous electrode. The eight detectors are arranged in an octagonal lead-shielded ring. Each pinhole in the eight-pinhole aperture placed at the center of the ring is matched to each individual detector array. An object is imaged onto each detector through a pinhole, and each detector is operated independently with list-mode acquisition. The imaging subject can be rotated about a vertical axis to obtain additional angular projections. The performance of SemiSPECT was characterized using 99mTc. When a 0.5 mm diameter pinhole is used, the spatial resolution on each axis is about 1.4 mm as estimated by the Fourier crosstalk matrix, which provides an algorithm-independent average resolution over the field of view. The energy resolution achieved by summing neighboring pixel signals in a 3 x 3 window is about 10% full-width-at-half-maximum of the photopeak. The overall system sensitivity is about 0.5 x 10(-4) with the energy window of +/-10% from the photopeak. Line-phantom images are presented to visualize the spatial resolution provided by SemiSPECT, and images of bone, myocardium, and human tumor xenografts in mice demonstrate the feasibility of preclinical small-animal studies with SemiSPECT.
Animals↗