878 research outputs found
Metals in the diffuse gas around high-redshift galaxies
The gas around galaxies provides fuel for star formation, playing a crucial role in the formation and evolution of galaxies. However, because the gas is very diffuse, it is difficult to observe in emission, so in this work we examine it by analyzing absorption lines in the spectra of bright background sources. Our observational results are also compared with current cosmological simulations.GalaxiesInterstellar matter and star formatio
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A fieldable instrument for waterborne radionuclide detection
In monitoring effluent leaving its sites, US DOE assays for alpha- emitting radionuclides (U, transuranics) to ensure compliance with regulatory limits. Because alpha emissions can only by detected over a short range in water ({approximately}40{mu}m), the conventional approach is to collect samples for processing in a central laboratory; a time-consuming and cost procedure ensues to separate and measure the radionuclides. Because of the sporadic nature of sampling processes, there is the possibility that a release may go undetected. We are addressing this issue by a developing a real-time, field- deployable instrument which incorporates a proprietary film that selectively binds radionuclides from dilute aqueous samples. By combining the film with an appropriate alpha spectrometer, we have developed a fieldable system that can operate as an autonomous monitor in a batch or continuous manner. Laboratory results to date have been encouraging. Positive identification of U and Pu has been made by resolving the energy spectrum of emitted alphas. Sensitivity for U is at the 10 part per trillion level (15 femtocuries per liter)
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A technical study of TLD beta calibration factor for exposures to depleted uranium
The beta calibration factor for converting light output (on reading a thermoluminescent dosimeter) to shallow dose equivalent has been reexamined through theoretical calculations and experimental measurements. The results support the previously determined value for contact with a depleted uranium slab but indicate that for many actual workplace situations, the contact value may be overly conservative
NIREX petrological samples archive
This report describes archival curation of petrological samples and related digital records
arising from past investigations undertaken by the BGS under the Nirex Site
Investigations Programmes at Sellafield and, to a lesser extent, Dounreay. This consisted
of the following tasks:
1. Log all relevant samples and subsamples in order to verify which can be readily made
available for future investigations.
2. Record their present storage locations within the BGS site at Keyworth.
3. Determine the extent of electronic records relating to these samples and held on the
Apple Mac databases within the (former) Mineralogy and Petrology Group.
4. Transfer these databases into the BGS data architecture.
5. Prepare a report recording these activities and metadata necessary to locate the
samples/subsamples and records for subsequent use.
The collections and electronic records were assembled during a series of investigations
carried out mostly by the Mineralogy and Petrology Group (MPG) of the British
Geological Survey in the early to mid 1990s, and some carried out by field staff of BGS.
These investigations formed part of the Site Investigations carried out by Nirex in
seeking a site acceptable for construction of a repository for low and medium level
radioactive waste
Can forest management based on natural disturbances maintain ecological resilience?
Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance
Personal identity (de)formation among lifestyle travellers: A double-edged sword?
This article explores the personal identity work of lifestyle travellers – individuals for whom extended leisure travel is a preferred lifestyle that they return to repeatedly. Qualitative findings from in-depth semi-structured interviews with lifestyle travellers in northern India and southern Thailand are interpreted in light of theories on identity formation in late modernity that position identity as problematic. It is suggested that extended leisure travel can provide exposure to varied cultural praxes that may contribute to a sense of social saturation. Whilst a minority of the respondents embraced a saturation of personal identity in the subjective formation of a cosmopolitan cultural identity, several of the respondents were paradoxically left with more identity questions than answers as the result of their travels
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Brittle behavior of SSC yokes
In liquid helium at 4 K ultra--low carbon steel is known to be brittle. Fracture toughness and ultimate strength measured by the National Institute of Standards and Technology (NIST) are used here to examine the brittle behavior of the SSC yokes. The fracture toughness K{sub Ic} of the material is used to estimate the maximum allowable length of pre--existing cracks. Tensile properties of the steel at 4 K are compared with maximum tensile stresses obtained from the ANSYS finite element analysis of the DSX201 cross--section. 5 refs., 3 figs., 4 tabs
Significant Biochemical, Biophysical and Metabolic Diversity in Circulating Human Cord Blood Reticulocytes
10.1371/journal.pone.0076062PLoS ONE810-POLN
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