Results 1 - 10 of 1974
Results 1 - 10 of 1974. Search took: 0.025 seconds
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[en] The objective of this work was to detect the inclusion of animal meal in Japanese quail (Coturnix coturnix japonica) diets, by analyzing eggs and their fractions (albumen and yolk) through the technique of carbon (13C/12C) and nitrogen (15N/14N) stable isotopes. Four hundred and thirty-two Japanese quails, 45-day-old females, were distributed in a completely randomized experimental design, in eight treatments: T1, strictly vegetable diet (VEG), with corn (Zea mays) and soybean (Glycine max) meal; T2, bovine meat and bone meal (BM); T3, poultry viscera meal (OM); T4, feather meal (FM); T5, BM+OM; T6, BM+FM; T7, OM+FM; and T8, BM+OM+FM. Sixteen eggs were randomly collected from each treatment – eight for whole egg analysis and eight for separate yolk and albumen analyses. To determine the turnover rate, the exponential isotope dilution model was used. The application of C and N stable isotopes allows identifying the use of animal meal in coded diets through the analysis of whole eggs and their fractions, which suggests that this technique is a promising tool for the traceability and certification of products of animal origin. (author)
[en] We investigate the transverse momentum dependence of valence and sea quark distribution functions of light asymmetric nuclei (He and Li). To this end, we first calculate the valence and sea distributions of these nuclei applying a parametrization method in which the parton distribution functions (PDFs) of nucleus are related to those of free nucleon via a weight function that contains the nuclear modifications. Then we obtain the unpolarized transverse momentum dependent (TMD) PDFs of the nucleus using the covariant parton model (CPM) approach. We also compute the valence and sea quark distributions ratios of He and Li to those of deuteron and present the results with respect to x (Bjorken variable) at fixed values of transverse momentum. It is found that these ratios shift to the larger values of x by increasing the transverse momentum value as expected and they are not transverse momentum dependent in large x region.
[en] O-glycosides are naturally occurring carbohydrates that have promising biological activities. However, the conventional way to market a drug involves an exhaustive and expensive process. On the other hand, research based on in silico approach has been shown to be efficient in predicting pharmacodynamic properties, reducing time and costs. In this work, we report the synthesis, complete labeling and evaluation of the pharmacokinetic and toxicity profile of 2-propyn-1-yl 2,3,4,6-tetra-O-acetyl-β-D-glycopyranose. The compound was obtained in good yield and excellent stereoselectivity. From the NOESY experiment it was possible to determine the major product of the glycosylation reaction. The in silico study, reported for the first time, indicated that this compound has good oral bioavailability, is active against the main molecular targets and exhibits low toxicity. (author)
[en] The worldwide comparison of stable 15N and 13C isotope measurements provides confidence in the analytical performance of stable isotope laboratories and hence an important tool for external quality control. The 2019 Proficiency Test (PT) on 15N and 13C isotopic abundance in plant materials, organized by the University of Wageningen, the Netherlands, and funded by the SWMCN Laboratory has been successfully completed. The Wageningen Evaluating Programs for Analytical Laboratories (WEPAL, http://www.wepal.nl/) is accredited for the organization of Inter-laboratory Sudies by the Dutch Accreditation Council.
[en] Elastic scattering of 6Li from16O nucleus in the energy range of 13:0 - 50.0 MeV was analyzed within the framework of optical potential, double folding optical potential, and cluster folding potentials. The present study involves theoretical calculations based on available experimental angular distributions of the scattering process. Of particular interest is the cluster folding based on the well-known cluster structure of 6Li. Elastic scattering data for the 6Li+16O system plotted as a function of momentum transfer showed that the real Coulomb nuclear interference region is independent of the bombarding energy. This structural pattern could be used to define the interaction potential with some certainty and to extract reliable values for the renormalization factors. (Author)
[en] On May 2019, the members of the Anthropocene Working Group completed a binding vote to affirm some of the key questions that have been agreed in 2016: the Anthropocene should be considered as a formal chronostratigraphic unit, defined by a Global Boundary Stratotype Section and Point (GSSP), using one of the stratigraphic signals around the mid-twentieth century of the Common Era. The fallout from nuclear weapons testing appears as the most suitable GSSP. In this article, the main anthropogenic markers are discussed as well as the sources or human-made radiation and the signature of nuclear weapons testing. The appearance of 239+240Pu in the early 1950s and the clear peak, in 1963, makes a good marker. High resolution archives include layers of sedimentary rocks, lacustrine and marine sediments and corals and polar ice cores. A coupled application of other radioactive isotopes, as 137Cs, 14C and 241Am, may be useful to categorize distinct fallout signatures. A site to define the Anthropocene (golden spike) would ideally be located between 30° and 60° north of the equator. Nevertheless, results obtained in sediments on the Brazilian coast showed that both 239+240Pu and 137Cs signatures could be detected and quantified as markers of this 'atomic age'. (author)
[en] The proposal for the development of a nuclear optical clock has triggered a multitude of experimental and theoretical studies. In particular the prediction of an unprecedented systematic frequency uncertainty of about 10 has rendered a nuclear clock an interesting tool for many applications, potentially even for a re-definition of the second. The focus of the corresponding research is a nuclear transition of the Th nucleus, which possesses a uniquely low nuclear excitation energy of only 8.12±0.11 eV (152.7±2.1 nm). This energy is sufficiently low to allow for nuclear laser spectroscopy, an inherent requirement for a nuclear clock. Recently, some significant progress toward the development of a nuclear frequency standard has been made and by today there is no doubt that a nuclear clock will become reality, most likely not even in the too far future. Here we present a comprehensive review of the current status of nuclear clock development with the objective of providing a rather complete list of literature related to the topic, which could serve as a reference for future investigations.
[en] Elemental and isotopic ratios (C/N, δ13C, δ15N) of sediment samples captured by PVC traps in eight stations along the coastal reefs of the Abrolhos region, Brazil, were analyzed. The study area is characterized by the influence of continental sediments on biogenic sediments. The highest δ13C values were found in the Sebastião Gomes (second shallower station), with average values close to -15‰ in all sampling periods. The isotopic ratio of carbon and nitrogen indicates that the organic matter analyzed has marine origin, with signature features of oceanic regions. The highest C/N ratio average value of 8.29 occurred in Nova Viçosa (the southernmost station and one of the shallowest) during the spring, in other seasons the average value was close to 7 in all periods. Although the values of C/N indicate a significantly marine contribution, δ15N values suggest that N series recycling processes are frequent during the time that the material remained in the environment. The results will provide a baseline for future environmental monitoring and studies on changes in sediment composition in an important set of coastal coral reefs. (author)
[en] The regulation for isotopes which emit radiation with extremely long half-lives such as Calsium-48 (t1/2=1.9×1019 year) or Bismuth-209 (t1/2=2.01×1019 year) was examined. At permission usage facilities pertaining to unsealed radioisotopes, all the radiation-emitting isotopes have to be controlled as radioisotopes regardless of their quantities or half-lives, even if radioactivity of these isotopes rarely exceeds the lower bound quantities (as with 'exemption levels'). This is because the lower bound quantities are evaluated in terms of integrated radioactivity of all the unsealed radiation-emitting isotopes placed in a factory or place of business. In most of such cases, these isotopes can be excluded from the subject of radiation control by considering the regulation on the concentration limit for the unsealed radiation-emitting isotope even at the permission usage facilities pertaining to unsealed radioisotopes. (author)
[en] Our present understanding of the structure of the Hoyle state in 12C and other near-threshold states in α-conjugate nuclei is reviewed in the framework of the α-condensate model. The 12C Hoyle state, in particular, is a candidate for α-condensation, due to its large radius and α-cluster structure. The predicted features of nuclear α-particle condensates are reviewed along with a discussion of their experimental indicators, with a focus on precision break-up measurements. Two experiments are discussed in detail, firstly concerning the break-up of 12C and then the decays of heavier nuclei. With more theoretical input, and increasingly complex detector setups, precision break-up measurements can, in principle, provide insight into the structures of states in α-conjugate nuclei. However, the commonly-held belief that the decay of a condensate state will result in Nα-particles is challenged. We further conclude that unambiguously characterising excited states built on α-condensates is difficult, despite improvements in detector technology. (author)