Hypotheses that dissolved organic carbon (DOC) and electrochemical charge affect the rate of methylmercury [CH 3 Hg(I)] synthesis by modulating the availability of ionic mercury [Hg(II)] to bacteria were tested by using a mer-lux bioindicator (O. Selifonova, R. Burlage, and T. Barkay, Appl. Environ. Microbiol. 59:3083-3090, 1993). A decline in Hg(II)-dependent light production was observed in the presence of increasing concentrations of DOC, and this decline was more pronounced at pH 7 than at pH 5, suggesting that DOC is a factor controlling the bioavailability of Hg(II). A thermodynamic model (MINTEQA2) was used to select assay conditions that clearly distinguished among various Hg(II) species. By using this approach, it was shown that negatively charged forms of mercuric chloride (HgCl 3 ؊ /HgCl 4 2؊) induced less light production than the electrochemically neutral form (HgCl 2), and no difference was observed between the two neutral forms, HgCl 2 and Hg(OH) 2. These results suggest that the negative charge of Hg(II) species reduces their availability to bacteria and may be one reason why accumulation of CH 3 Hg(I) is more often reported to occur in freshwater than in estuarine and marine biota.
Daily tesamorelin for 26 weeks decreased visceral fat and improved lipid profiles, effects that might be useful in HIV-infected patients who have treatment-associated central fat accumulation. (ClinicalTrials.gov number, NCT00123253 [ClinicalTrials.gov] .).
Analysis of mercury-contaminated soil from the flood plain of East Fork Poplar Creek (EFPC) in Oak Ridge, TN, using a scanning electron microscope (SEM) with energy-and wavelength X-ray dispersive spectroscopy (EDS/WDS) and a transmission electron microscope (TEM) with select area electron diffraction (SAED) revealed the presence of submicron, crystalline mercuric sulfide (HgS) in the form of metacinnabar. The HgS formed in place after the deposition and burial of mercury-contaminated soils. A reaction path model developed to describe the geochemical evolution of the soil redox conditions during flooding predicted that the resultant pe and pH of the soil would be within the stability range of HgS. The reaction of mercury with other metal sulfides or sulfhydryl groups in the soil may have also contributed to the formation of HgS. The formation of HgS is significant to the remediation efforts at EFPC because the toxicity, leachability, and volatility of mercury in soils is dependent on the solid phase speciation. Because the local hydrogeochemical conditions are not unique, the formation of HgS at this site has implications to other environments as well.
At its most elemental, patient-reported outcomes (PRO) assessment involves asking the patients questions and evaluating their answers. Instrument developers need to be clear about what they want to know, from whom they want to know it and why, whether what they learned is credible, and whether they can interpret what they learned in the context of the research objectives. Because credible instrument development is neither inexpensive nor technically trivial, researchers must first determine that no available measure meets their research objectives. We suggest that the tasks of either reviewing current instruments or developing new ones originate from the same basic premise: PRO assessment requires a well-articulated conceptual framework. Once defined in the context of the research objectives, the conceptual framework needs to be adapted to the population of interest. We discuss how qualitative methods enrich the conceptual framework and facilitate the technical measurement tasks of item development, testing, and reduction. We recognize that PRO assessment stands at a technological crossroads with the increasingly frequent application of "modern" psychometric methods and discuss how innovations such as item banks and computer-adaptive testing will influence PRO instrument development. Although items are the essential building blocks for instruments, scales are the primary unit of analysis for PRO assessment, and we discuss methods for scoring and combining them. Finally, PRO assessment is meaningless if the key figure chooses not to cooperate. We consider how respondent burden influences the quality of PRO assessment.
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