1,721,022 research outputs found
Preparation and purification of high specific activity radionuclides for environmental studies
No full textHigh sp. activity radionuclides are a powerful tool for labeling a large range of inorganic and organometallic species that are present in the environment at very low concentrations. To study the environmental impact of trace elements (TE) on humans, it is of fundamental importance to carry out both in-vitro and in-vivo experiments on cell cultures and lab. animals, with concentrations of these TE representative of the actual long-term and low-level exposures. To obtain these radiotracers in a very high specific activity form, it is necessary (1) to optimize the production method by either charged particle accelerator (normally cyclotron) or nuclear reactor irradiation; (2) to separate and purify them from the irradiated target by chemical or physicochemical methods, without the addition of inactive carriers (i.e., the socalled no-carrier-added form); and (3) to carry out a series of analytical and radioanalytical tests to verify the chemical, radiochememical and radionuclide purities of the tracer or labeled compound under investigation. Some production, separation, purification and quality control methods developed for the 2 cyclotron-produced radionuclides 52Mn and 48V are presented and discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Content of trace elements in the respirable fractions of the air particulate of urban and rural areas monitored by Neutron Activation Analysis
No full textThe concentrations (ng/m3) of more than 30 trace elements have been determined in the total air particulate matter and in the size-segregated fractions collected in urban, industrialized, and rural residential areas in northern Italy by means of a multistage inertial impactor with the PM10 inlet. All measurements have been carried out by instrumental neutron activation analysis, except for Pb and Cd, which have been determined by electrothermal atomic absorption spectroscopy. Analytical quality assurance procedures have been developed with special regard to blanks, reagents, and sampling. Total concentrations and the granulometric distribution found in the different locations are reported and compared
Preparation of high specific activity radiotracers for radioanalytical studies
No full textThis work reviews the more recent advances in this field carried out by the authors groups. High specific activity radiotracers are very suitable for studies related to the toxicol. impact of trace elements onto human health. In order to investigate the metabolic behavior of Low Level Exposure (LLE) to trace elements, it is necessary to carry out in-vitro and in-vivo expts. with tracers whose concn. is of the same order of magnitude as the present environmental exposure values (ng-μg/kg day). Prepns., sepns. and purifications of some no carrier added (NCA) radiotracers (48V, 95m,96Tc, 195m,g,197m,gHg, 199Au, 202Tl) produced by either cyclotron or nuclear reactor irradn., are presented and discussed. 23 Refs
Analytical Related Problems in Metals and Trace Elements Determination in Industrial Waste Landfill Leachates.
No full textThe periodic analytical control of wastelandfill leachate is of fundamental importance not only to check the presence of possible toxic substances, but also to assess changes in concentration levels and behaviour with time. This work identifies some of the difficulties which arise during the analysis of some heavy metals and traceelements in leachate samples from a controlled industrialwasteslandfill located in north Italy. The analyticalproblems encountered using both electro-thermal atomic absorption spectroscopy (ETAAS) and neutron activation analysis (NAA) for the determination of a series of elements, Cu, Cd, Pb, Ni, Mn, V, As, Se, Sb, Th, Sn, Cs, W, Cr, with concentration often at nanogram levels, are presented and evaluated. To solve these problems two selective chemical procedures have been developed to separate and to eliminate the matrix interfering compounds or elements (i.e., organic matter, complexing agents, Cl−, Br−, S2−, Na+) which reduce and in some cases impair the sensitivity of the technique. For the analyses by ETAAS a preliminary preconcentration and separation procedure, based on the ion exchange resin Chelex-100 has been developed to determine Pb, Cd, Co, Cu, Ni and Sn. In the case of NAA a specific radiochemical separation had to be studied for the analysis of Sn, V, W, Mn, Cr, As, Sb, Se, Th in presence of high bromine and sodium concentrations. Procedures blanks and yields have been controlled and evaluated and quality assurance measurements have been carried out analyzing, with the proposed methods, standard reference materials from BCR and NIST. Furthermore, different mineralization procedures using both microwave and Teflon bomb have been compared and evaluated
Radioanalytical Quality Controls by INAA and RNAA determination of Specific Activity, Chemical Purity and Isotopic Composition of labelled compounds
No full textStudio delle concentrazioni degli elementi in tracce e della loro distribuzione granulometrica nel particolato atmosferico di zone urbane e industrializzate mediante analisi per attivazione neutronica.
No full textN.C.A. gold-199: a radionuclide suitable for both SPECT and radionuclide therapy: production yield, radiochemical separation, radionuclidic purity and specific activity
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