77 research outputs found
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Health Effects of Low-Level Radiation
The author reviews the bases for setting and the adequacy of radiation protection standards. (PSB
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Viewpoint on Proposed Radiation-Protection Standards
The proposed revision of 10CFR20 is discussed from a personal perspective. A brief historical review of the development of radiation standards is presented, and arguments against the proposed de minimis level elaborated upon. (ACR
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Experimental Evaluation of the Radiation Protection Afforded by Typical Oak Ridge Homes Against Distributed Sources
The protection afforded against simulated fall-out radiation has been evaluated for several typical homes in the Oak Ridge area. Nine houses were chosen to represent a variety of construction materials, topographical conditions and sizes; they included three types of Oak Ridge Cemesto houses, one concrete-block house with a basement fall-out shelter, and two wood-frame houses. The protection factor (ratio of open-field exposure dose rate to exposure dose rate in the house) in all these houses ranged from 2 to 5 on the main floor and from 5 to 30 in the basements, except in the fall-out shelter, where the protection factor was greater than 100. The analysis showed that sloping lots. common to Oak Ridge, do not appreciably affect the protection factor for the main floor. Owing to the generally increased exposure of the basement walls on such lots, the protection factors in the basements were typically lower than in similar basements built on level lots. (auth
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Studies Directed Toward Improving the Spatial Resolution of the Distribution of Plutonium in Bone
Of several methods which have been discussed for the improvement of resolution in fission fragment track detectors for neutron-induced autoradiography, emphasis had been on the use of absorber layers inserted between the sample and the detector. Scanning electron microscopy was shown to be beneficial for viewing only the entrance holes of fission fragment tracks in the detector foil. The primary disadvantage of using thick absorbers lies in the factor of 50 to 100 percent loss in sensitivity over bare detectors. One promising solution to this problem is the use of glass detectors with high critical angles, no absorbers, and short etching times. Such detectors gave the best resolution of any system tested (+-2 ), though they suffered at fluences greater than 10 n/sub th/ cm from high backgrounds as a result of their natural uranium content. Two samples of bone, each of 1 mg were dissolved in HNO spiked with Pu, and analyzed for total Pu content in an isotopic abundance mass spectrometer. The Pu concentration was 1 ppm by weight; bones with 10 ppm of Pu are required, therefore, for neutron-induced autoradiography. Bones in suitable form for IMMA required only to be coated with a thin conductive coating of gold. In a fast scan mode, all elements were searched in 200 x 200 areas. Good quality micrographs were obtained showing Na, K, Ca, and P as major constituents with minor elements present, such as Cr and Fe. (CH
Gas-phase detection of solid-state fission product complexes for post-detonation nuclear forensic analysis
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Civil Effects Study CEX-58.1
Report regarding experiments made to determine the fallout-radiation protection offered by five typical residential structures located at the Nevada Test Site
Ancestral predisposition toward a domesticated lifestyle in the termite-cultivated fungus Termitomyces
The ancestor of termites relied on gut symbionts for degradation of plant material, an association that persists in all termite families. However, the single-lineage Macrotermitinae has additionally acquired a fungal symbiont that complements digestion of food outside the termite gut. Phylogenetic analysis has shown that fungi grown by these termites forma clade—the genus Termitomyces—but the events leading toward domestication remain unclear. To address this, we reconstructed the lifestyle of the common ancestor of Termitomyces using a combination of ecological data with a phylogenomic analysis of 21 related non-domesticated species and 25 species of Termitomyces. We show that the closely related genera Blastosporella and Arthromyces also contain insect-associated species. Furthermore, the genus Arthromyces produces asexual spores on the mycelium, which may facilitate insect dispersal when growing on aggregated subterranean fecal pellets of a plant-feeding insect. The sister-group relationship between Arthromyces and Termitomyces implies that insect association and asexual sporulation, present in both genera, preceded the domestication of Termitomyces and did not follow domestication as has been proposed previously. Specialization of the common ancestor of these two genera on an insect-fecal substrate is further supported by similar carbohydrate-degrading profiles between Arthromyces and Termitomyces. We describe a set of traits that may have predisposed the ancestor of Termitomyces toward domestication, with each trait found scattered in related taxa outside of the termite-domesticated clade. This pattern indicates that the origin of the termite-fungus symbiosis may not have required large-scale changes of the fungal partner.http://www.cell.com/current-biology/homeam2022BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant Patholog
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