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Relative merits of stochastic and nonstatistical methods of computing primary ionization doses - radiation dose calculations
Rat skin was exposed to the plateau region of the 1.0 GeV/nucleon 56Fe beam at the Brookhaven AGS. Rats were irradiated or not with single of split doses of 56Fe or argon; some 56Fe-exposed rats were fed 250 ppm retinyl acetate continuously in the lab chow beginning 1 week before irradiation. All lesions were noted, photographed and identified for eventual histological diagnosis. The preponderance of the tumors so far are fibromas. The data show that single doses of 56Fe ions are 2 or 3 fold more effective than argon in producing tumors at 4.5 Gy but are about equally effective at 3.0 Gy and 9.0 Gy. The presence of 250 ppm retinyl acetate in the lab chow reduced the incidence of tumors by about 50-60% in comparison to groups exposed only to the radiation. These are preliminary findings based on only about one-fourth the eventual number of tumors expected.
Biomarkers provide methods to measure changes in biological systems and to relate them to environmental insults and disease processes. Biomarkers can be classified as markers of exposure and dose, markers of sensitivity, and markers of disease. It is important that the differences and applications of the various types of biomarkers be clearly understood. The military is primarily interested in early biomarkers of exposure and dose that do not require high levels of sensitivity but can be used to rapidly triage war fighters under combat or terrorist conditions and determine which, if any, require medical attention. Biomarkers of long-term radiation risk represent the second area of interest for the military. Biomarkers of risk require high sensitivity and specificity for the disease and insult but do not require rapid data turnaround. Biomarkers will help provide information for quick command decisions in the field, characterise long-term troop risks and identify early stages of radiation-induced diseases. This information provides major positive reassurances about individual exposures and risk that will minimise the physical and psychological impact of wartime radiation exposures.
PURPOSE: To investigate initial chromatid breaks in prematurely condensed G2 chromosomes following exposure to heavy ions of different LET. MATERIAL AND METHODS: Exponentially growing human fibroblast cells AG1522 were irradiated with gamma-rays, energetic carbon (13 keV/ microm, 80 keV/microm), silicon (55 keV/microm) and iron (140 keV/microm, 185keV/microm, 440keV/microm) ions. Chromosomes were prematurely condensed using calyculin-A. Initial chromatid-type and isochromatid breaks in G2 cells were scored. RESULTS: The dose response curves for total chromatid breaks were linear regardless of radiation type. The relative biological effectiveness (RBE) showed a LET-dependent increase, peaking around 2.7 at 55-80keV/microm and decreasing at higher LET. The dose response curves for isochromatid-type breaks were linear for high-LET radiations, but linear-quadratic for gamma-rays and 13 keV/microm carbon ions. The RBE for the induction of isochromatid breaks obtained from linear components increased rapidly between 13keV/microm (about 7) and 80keV/microm carbon (about 71), and decreased gradually until 440 keV/microm iron ions (about 66). CONCLUSIONS: High-LET radiations are more effective at inducing isochromatid breaks, while low-LET radiations are more effective at inducing chromatid-type breaks. The densely ionizing track structures of heavy ions and the proximity of sister chromatids in G2 cells result in an increase in isochromatid breaks.
Exposure to heavy particles can affect the functioning of the central nervous system (CNS), particularly the dopaminergic system. In turn, the radiation-induced disruption of dopaminergic function affects a variety of behaviors that are dependent upon the integrity of this system, including motor behavior (upper body strength), amphetamine (dopamine)-mediated taste aversion learning, and operant conditioning (fixed-ratio bar pressing). Although the relationships between heavy particle irradiation and the effects of exposure depend, to some extent, upon the specific behavioral or neurochemical endpoint under consideration, a review of the available research leads to the hypothesis that the endpoints mediated by the CNS have certain characteristics in common. These include: (1) a threshold, below which there is no apparent effect; (2) the lack of a dose-response relationship, or an extremely steep dose-response curve, depending on the particular endpoint; and (3) the absence of recovery of function, such that the heavy particle-induced behavioral and neural changes are present when tested up to one year following exposure. The current report reviews the data relevant to the degree to which these characteristics are common to neurochemical and behavioral endpoints that are mediated by the effects of exposure to heavy particles on CNS activity. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.
We present results of continuing efforts to evaluate total dose bias dependency and ELDRS effects in bipolar linear microcircuits. Several devices were evaluated, each exhibiting moderate to significant bias and/or dose rate dependency.
Radiation hardened linear devices are characterized for performance in combined total dose and displacement damage environments for a mission scenario with a high radiation level. Performance at low and high dose rate for both biased and unbiased conditions is compared and the impact to hardness assurance methodology is discussed.
The purpose of this test was to characterize the Philips/NXP BFR92A NPN 5 gigahertz wide band silicon transistor for total dose response. This test shall serves as the radiation lot acceptance test (RLAT) for the lot date code (LDC) 1027. The BFR92A is packaged in a 3-pin plastic SOT23 package. Low dose rate (LDR/ELDRS) irradiations was performed.
This report presents total ionizing dose evaluation data for the Linear Technology Corporation LTC1877 high efficiency monolithic synchronous step-down regulator. Data sheet parameters were tracked as a function of ionizing dose up to a total of 20 krad(SiO2). Control devices were also used.
Variability of the space radiation environment is investigated with regard to total dose specification for spacecraft electronics. It is shown to have a significant impact. A new approach is developed for total dose requirements that replaces the radiation design margin concept with failure probability during a mission.
A confidence level based approach to total dose radiation hardness assurance is presented for spacecraft electronics. It is applicable to both ionizing and displacement damage dose. Results are compared to the traditional approach that uses radiation design margin and advantages of the new approach are discussed.
Total ionizing dose and displacement damage testing was performed to characterize and determine the suitability of candidate electronics for NASA space utilization. Devices tested include optoelectronics, digital, analog, linear bipolar devices, and hybrid devices. Displacement Damage, Optoelectronics, Proton Damage, Single Event Effects, and Total Ionizing Dose.
A total dose analysis for exposure of electronic parts at the box level is presented for the Hubble Space Telescope. This was done using solid angle sectoring/3-dimensional ray trace and Monte Carlo radiation transport simulations. Results are discussed in terms of parts that are potential total dose concerns.
The purpose of this test was to characterize the Analog Devices ADXL354 parameter degradation for total dose response. In the test, the device was exposed to a dose rate of 50 rad(Si)/s or 0.5 Gy(Si)/s using a gamma radiation source in accordance with MIL-STD-883K Paragraph 3.6.1 (Condition A). Device parameters such as supply current, self-test voltage response, and LDO regulator output voltages were monitored.
The purpose of this study is to examine the low dose rate total ionizing dose (TID) susceptibility of the SFT2222A NPN bipolar junction transistor (BJT) manufactured by Solid State Devices, Inc. (SSDI).
This study was undertaken to determine the total ionizing dose (TID) sensitivity of the PA10 Power Op Amp Manufactured by APEX (figure 1), which is a candidate for use on the LDCM TIRS instrument. The test was conducted with interest in both parametric degradation and functional failure in the configuration like that of the TIRS application. (See figure 2). The DUT was irradiated in a stepwise fashion, with parametric and functional degradation measured between steps. The parts were irradiated with gamma rays at a low dose rate (~0.01 rads(Si)/sec.).
This study compares two statistical modeling approaches to construct summary dose-response curves for low boom community noise surveys. NASA field survey data were used that consist of multiple responses from a survey participant. These data require an approach that accounts for the correlation among repeated annoyance observations from the same participant. A multilevel model accounts for the correlation by allowing estimated parameters to vary with each survey participant. On the other hand, a population average model utilizes generalized estimating equations and accounts for the correlation via a user-specified within-subject correlation structure. A visual comparison of the dose-response curves for these two methods reveals similar results. When comparing specific points along the summary curves, the multilevel model yields more precise confidence bounds than the population average model. The similarity between the summary curves derived from each model lends validity to both approaches for approximating a population representative summary curve.
This study compares two statistical models to construct summary dose-response curves for low boom community noise surveys. Data from two NASA field surveys are used that consist of multiple responses per survey participant. These data require an approach that accounts for the correlation among repeated annoyance observations from the same participant. A multilevel model accounts for the correlation by allowing estimated parameters to vary with each survey participant. On the other hand, a population average model utilizes generalized estimating equations and accounts for the correlation via a userspecified within-subject correlation structure. A visual comparison of the dose-response curves for these two methods reveals similar results. When comparing specific points along the summary curves, the multilevel model yields more precise confidence bounds than the population average model. The similarity between the summary curves derived from each model lends validity to both approaches for approximating a population representative summary curve, though modeling assumptions may lend favor to the multilevel logistic modeling approach over the population average model.