7,266 research outputs found
Some aspects of analytical chemistry as applied to water quality assurance techniques for reclaimed water: The potential use of X-ray fluorescence spectrometry for automated on-line fast real-time simultaneous multi-component analysis of inorganic pollutants in reclaimed water
The potential use of isotopically excited energy dispersive X-ray fluorescence (XRF) spectrometry for automated on line fast real time (5 to 15 minutes) simultaneous multicomponent (up to 20) trace (1 to 10 parts per billion) analysis of inorganic pollutants in reclaimed water was examined. Three anionic elements (chromium 6, arsenic and selenium) were studied. The inherent lack of sensitivity of XRF spectrometry for these elements mandates use of a preconcentration technique and various methods were examined, including: several direct and indirect evaporation methods; ion exchange membranes; selective and nonselective precipitation; and complexation processes. It is shown tha XRF spectrometry itself is well suited for automated on line quality assurance, and can provide a nondestructive (and thus sample storage and repeat analysis capabilities) and particularly convenient analytical method. Further, the use of an isotopically excited energy dispersive unit (50 mCi Cd-109 source) coupled with a suitable preconcentration process can provide sufficient sensitivity to achieve the current mandated minimum levels of detection without the need for high power X-ray generating tubes
Individual and Collective Responsiveness to Climate Change: A Response to Dwyer
Commentaire / CommentaryLâhistoire de James Dwyer au sujet dâune Commission GAIA fictive met en eÌvidence les preÌoccupations concernant la porteÌe de la bioeÌthique, en particulier en ce qui concerne la reÌpartition de la responsabiliteÌ au niveau international face aux impacts des changements climatiques sur la santeÌ. Ce commentaire traite de lâimpact potentiel dâun individu sur les eÌmissions de gaz aÌ effet de serre et lâimportance des reÌponses institutionnelles afin dâavoir un impact significatif.James Dwyerâs story about a fictional GAIA Commission highlighted unresolved concerns about the scope of bioethics, specifically regarding the global distribution of, and responsibility for, the health impacts of climate change. This commentary discusses the potential impact of an individual on greenhouse gas emissions and the importance of engaging institutional responses in order to have meaningful impacts
Ocular Phenotyping in the harlequin Mouse Model of Retinal Degeneration: A Framework for Therapeutic Testing
Retinal degeneration, despite devastating effects, lacks therapy. Memantine has potential for preserving vision by reducing excitotoxicity associated with reactive oxygen species (ROS). A model for memantine delivery is the oxidative stress- and retinal degeneration in harlequin (hq) mice. Wild type (WT) and hq mice received untreated or memantine-treated (30 mg/kg/ day) drinking water at 1 out to 2,4,6, 8 and 10 months (mo) of age (5 males per cohort). Retinal integrity was assessed using electroretinography and ocular coherence tomography with ROS levels and apoptosis examined postmortem. Reduced hq vision was evident at 2 mo with a slight elevation in ROS at 2 mo, central retinal photoreceptor layer thinning at 4 mo and significant apoptosis at 4 mo. Excitotoxicity was not evident. Memantine had expected effects in WT mice but did not preserve hq vision. Ocular phenotyping of hq mice revealed dry age-related macular degeneration and a valid framework for testing appropriate drugs
HazardReady â a geographically based natural hazard education and preparedness web application
Earthquakes, floods, wildfires, and other natural disasters are inevitable and costly both in terms of lives lost and money spent on recovery. Scientific research on natural hazards is widely shared within the scientific community, but is less often made more widely accessible, as methods or pathways for providing scientific natural hazard information and data in non-technical language are limited. Priorities for imparting hazard information include: 1) scientific accuracy, 2) spatial granularity, 3) integration of information about all relevant hazards, 4) nontechnical content, 5) appropriate preparedness activities, and 6) engagement with existing disaster response and mitigation capabilities. In response to these priorities, we developed HazardReady, an interactive online application that delivers location-based multihazard risk and preparedness information using graphics and natural language easily understood by nonexpert users. This paper explores the development of the prototype for Missoula County, Montana, U.S.A. called MissoulaReady. The web application is built on spatial data layers corresponding to levels of risk and historical distributions of natural hazards in Missoula County. A web user queries these data by searching on a spatial location, either an address or a map click, for which curated, location-specific, interpreted risk information is then served. We specifically address the steps required to implement all of the priorities identified, including how natural hazard data are collated, modified, and interpreted, as well as methods by which diverse stakeholders were involved in the applicationâs creation. Focus groups and usage metrics indicate that the application meets criteria of scientific accuracy and usability
Scanning electrochemical microscopy as a local probe of oxygen permeability in cartilage
The use of scanning electrochemical microscopy, a high-resolution chemical imaging technique, to probe the distribution and mobility of solutes in articular cartilage is described. In this application, a mobile ultramicroelectrode is positioned close (not, vert, similar1 ÎŒm) to the cartilage sample surface, which has been equilibrated in a bathing solution containing the solute of interest. The solute is electrolyzed at a diffusion-limited rate, and the current response measured as the ultramicroelectrode is scanned across the sample surface. The topography of the samples was determined using Ru(CN)64â, a solute to which the cartilage matrix was impermeable. This revealed a number of pit-like depressions corresponding to the distribution of chondrocytes, which were also observed by atomic force and light microscopy. Subsequent imaging of the same area of the cartilage sample for the diffusion-limited reduction of oxygen indicated enhanced, but heterogeneous, permeability of oxygen across the cartilage surface. In particular, areas of high permeability were observed in the cellular and pericellular regions. This is the first time that inhomogeneities in the permeability of cartilage toward simple solutes, such as oxygen, have been observed on a micrometer scale
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