7,026 research outputs found

    Drug resistance in B and non-B subtypes amongst subjects recently diagnosed as primary/recent or chronic HIV-infected over the period 2013–2016: Impact on susceptibility to first-line strategies including integrase strand-transfer inhibitors

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    Objectives To characterize the prevalence of transmitted drug resistance mutations (TDRMs) by plasma analysis of 750 patients at the time of HIV diagnosis from January 1, 2013 to November 16, 2016 in the Veneto region (Italy), where all drugs included in the recommended first line therapies were prescribed, included integrase strand transfer inhibitors (InNSTI). Methods TDRMs were defined according to the Stanford HIV database algorithm. Results Subtype B was the most prevalent HIV clade (67.3%). A total of 92 patients (12.3%) were expected to be resistant to one drug at least, most with a single class mutation (60/68–88.2% in subtype B infected subjectsand 23/24–95.8% in non-B subjects) and affecting mainly NNRTIs. No significant differences were observed between the prevalence rates of TDRMs involving one or more drugs, except for the presence of E138A quite only in patients with B subtype and other NNRTI in subjects with non-B infection. The diagnosis of primary/recent infection was made in 73 patients (9.7%): they had almost only TDRMs involving a single class. Resistance to InSTI was studied in 484 subjects (53 with primary-recent infection), one patient had 143C in 2016, a total of thirteen 157Q mutations were detected (only one in primary/recent infection). Conclusions Only one major InSTI-TDRM was identified but monitoring of TDRMs should continue in the light of continuing presence of NNRTI-related mutation amongst newly diagnosed subjects, sometime impacting also to modern NNRTI drugs recommended in first-line therapy

    Influence of shower fluctuations and primary composition on studies of the shower longitudinal development

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    We study the influence of shower fluctuations, and the possible presence of different nuclear species in the primary cosmic ray spectrum, on the experimental determination of both shower energy and the proton air inelastic cross section from studies of the longitudinal development of atmospheric showers in fluorescence experiments. We investigate the potential of track length integral and shower size at maximum as estimators of shower energy. We find that at very high energy (~10^19-10^20 eV) the error of the total energy assignment is dominated by the dependence on the hadronic interaction model, and is of the order of 5%. At lower energy (~10^17-10^18 eV), the uncertainty of the energy determination due to the limited knowledge of the primary cosmic ray composition is more important. The distribution of depth of shower maximum is discussed as a measure of the proton-air cross section. Uncertainties in a possible experimental measurement of this cross section introduced by intrinsic shower fluctuations, the model of hadronic interactions, and the unknown mixture of primary nuclei in the cosmic radiation are numerically evaluated.Comment: 12 pages, 11 figures, 4 table

    A new FSA approach for in situ γ\gamma-ray spectroscopy

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    An increasing demand of environmental radioactivity monitoring comes both from the scientific community and from the society. This requires accurate, reliable and fast response preferably from portable radiation detectors. Thanks to recent improvements in the technology, γ\gamma-spectroscopy with sodium iodide scintillators has been proved to be an excellent tool for in-situ measurements for the identification and quantitative determination of γ\gamma-ray emitting radioisotopes, reducing time and costs. Both for geological and civil purposes not only 40^{40}K, 238^{238}U, and 232^{232}Th have to be measured, but there is also a growing interest to determine the abundances of anthropic elements, like 137^{137}Cs and 131^{131}I, which are used to monitor the effect of nuclear accidents or other human activities. The Full Spectrum Analysis (FSA) approach has been chosen to analyze the γ\gamma-spectra. The Non Negative Least Square (NNLS) and the energy calibration adjustment have been implemented in this method for the first time in order to correct the intrinsic problem related with the χ2\chi ^2 minimization which could lead to artifacts and non physical results in the analysis. A new calibration procedure has been developed for the FSA method by using in situ γ\gamma-spectra instead of calibration pad spectra. Finally, the new method has been validated by acquiring γ\gamma-spectra with a 10.16 cm x 10.16 cm sodium iodide detector in 80 different sites in the Ombrone basin, in Tuscany. The results from the FSA method have been compared with the laboratory measurements by using HPGe detectors on soil samples collected in the different sites, showing a satisfactory agreement between them. In particular, the 137^{137}Cs isotopes has been implemented in the analysis since it has been found not negligible during the in-situ measurements.Comment: accepted by Science of Total Environment: 8 pages, 10 figures, 3 table

    Impact of a revised 25^{25}Mg(p,γ\gamma)26^{26}Al reaction rate on the operation of the Mg-Al cycle

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    Proton captures on Mg isotopes play an important role in the Mg-Al cycle active in stellar H-burning regions. In particular, low-energy nuclear resonances in the 25^{25}Mg(p,γ\gamma)26^{26}Al reaction affect the production of radioactive 26^{26}Algs^{gs} as well as the resulting Mg/Al abundance ratio. Reliable estimations of these quantities require precise measurements of the strengths of low-energy resonances. Based on a new experimental study performed at LUNA, we provide revised rates of the 25^{25}Mg(p,γ\gamma)26^{26}Algs^{gs} and the 25^{25}Mg(p,γ\gamma)26^{26}Alm^{m} reactions with corresponding uncertainties. In the temperature range 50 to 150 MK, the new recommended rate of the 26^{26}Alm^{m} production is up to 5 times higher than previously assumed. In addition, at T=100=100 MK, the revised total reaction rate is a factor of 2 higher. Note that this is the range of temperature at which the Mg-Al cycle operates in an H-burning zone. The effects of this revision are discussed. Due to the significantly larger 25^{25}Mg(p,γ\gamma)26^{26}Alm^{m} rate, the estimated production of 26^{26}Algs^{gs} in H-burning regions is less efficient than previously obtained. As a result, the new rates should imply a smaller contribution from Wolf-Rayet stars to the galactic 26^{26}Al budget. Similarly, we show that the AGB extra-mixing scenario does not appear able to explain the most extreme values of 26^{26}Al/27^{27}Al, i.e. >102>10^{-2}, found in some O-rich presolar grains. Finally, the substantial increase of the total reaction rate makes the hypothesis of a self-pollution by massive AGBs a more robust explanation for the Mg-Al anticorrelation observed in Globular-Cluster stars

    Activation measurement of the 3He(alpha,gamma)7Be cross section at low energy

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    The nuclear physics input from the 3He(alpha,gamma)7Be cross section is a major uncertainty in the fluxes of 7Be and 8B neutrinos from the Sun predicted by solar models and in the 7Li abundance obtained in big-bang nucleosynthesis calculations. The present work reports on a new precision experiment using the activation technique at energies directly relevant to big-bang nucleosynthesis. Previously such low energies had been reached experimentally only by the prompt-gamma technique and with inferior precision. Using a windowless gas target, high beam intensity and low background gamma-counting facilities, the 3He(alpha,gamma)7Be cross section has been determined at 127, 148 and 169 keV center-of-mass energy with a total uncertainty of 4%. The sources of systematic uncertainty are discussed in detail. The present data can be used in big-bang nucleosynthesis calculations and to constrain the extrapolation of the 3He(alpha,gamma)7Be astrophysical S-factor to solar energies

    A nested alignment graph kernel through the dynamic time warping framework

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    In this paper, we propose a novel nested alignment graph kernel drawing on depth-based complexity traces and the dynamic time warping framework. Specifically, for a pair of graphs, we commence by computing the depth-based complexity traces rooted at the centroid vertices. The resulting kernel for the graphs is defined by measuring the global alignment kernel, which is developed through the dynamic time warping framework, between the complexity traces. We show that the proposed kernel simultaneously considers the local and global graph characteristics in terms of the complexity traces, but also provides richer statistic measures by incorporating the whole spectrum of alignment costs between these traces. Our experiments demonstrate the effectiveness and efficiency of the proposed kernel

    πNN\pi NN coupling determined beyond the chiral limit

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    Within the conventional QCD sum rules, we calculate the πNN\pi NN coupling constant, gπNg_{\pi N}, beyond the chiral limit using two-point correlation function with a pion. We consider the Dirac structure, iγ5i\gamma_5, at mπ2m_\pi^2 order, which has clear dependence on the PS and PV coupling schemes for the pion-nucleon interactions. For a consistent treatment of the sum rule, we include the linear terms in quark mass as they constitute the same chiral order as mπ2m_\pi^2. Using the PS coupling scheme for the pion-nucleon interaction, we obtain gπN=13.3±1.2g_{\pi N}=13.3\pm 1.2, which is very close to the empirical πNN\pi NN coupling. This demonstrates that going beyond the chiral limit is crucial in determining the coupling and the pseudoscalar coupling scheme is preferable from the QCD point of view.Comment: 8 pages, revtex, some errors are corrected, substantially revise

    Tilted axis rotation, candidates for chiral bands, and wobbling motion in 138Nd

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    High-spin states in 138Nd were investigated using the reaction 94Zr(48Ca,4n), detecting coincident γ rays with the gasp spectrometer. A rich level scheme was constructed including four bands of negative parity at low spins, eight bands of dipole transitions, and eight bands of quadrupole transitions at medium spins. The cranked shell model and the tilted-axis cranking model are used to assign configurations to the observed bands, where zero pairing is assumed. For selected configurations the case of finite pairing is also considered. A consistent notation for configuration assignment that applies for both zero and finite pairing is introduced. The observed bands are interpreted as rotation around the short and long principal axes (quadrupole bands), as well as around a tilted axis (dipole bands). The dipole bands have an intermediate character, between magnetic and collective electric rotation. A pair of dipole bands is identified as candidates for chiral partners. The possible existence of the wobbling mode at low deformation and medium spins is discussed. The consistent interpretation of the multitude of observed bands strongly supports the existence of stable triaxial deformation at medium spins in 138Nd. ©2012 American Physical Societ

    The 3He(alpha,gamma)7Be S-factor at solar energies: the prompt gamma experiment at LUNA

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    The 3He(alpha,gamma)7Be process is a key reaction in both Big-Bang nucleosynthesis and p-p chain of Hydrogen Burning in Stars. A new measurement of the 3He(alpha,gamma)7Be cross section has been performed at the INFN Gran Sasso underground laboratory by both the activation and the prompt gamma detection methods. The present work reports full details of the prompt gamma detection experiment, focusing on the determination of the systematic uncertainty. The final data, including activation measurements at LUNA, are compared with the results of the last generation experiments and two different theoretical models are used to obtain the S-factor at solar energies.Comment: Accepted for publication in Nucl. Phys.

    Preliminary results for the characterization of the radiological levels of rocks in Tuscany Region.

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    The environmental background levels of natural radiation due to the nuclides in rocks vary in significant amounts that depend on the geological and geomorphological features of a territory. The main source of terrestrial gamma-ray radiation exposure to humans is from 238U, 232Th decay chains and 40K decay. This paper reports a part of the results of the Research Project “Measurement of natural radioactivity and mapping of the radioisotope abundances of Tuscany Region”, which started at August 2008 and it is supported by founds of Tuscany Region. The aim of this project is to realize the thematic maps of radioactivity content and in particular of the abundances of eU1, eTh1 and 40K. These goals will be achieved by integrating the information from measurements on samples in laboratory with in-situ investigations and airborne surveys. The Legnaro National Laboratory (LNL) is the national leader for the design and realization of high-resolution gamma-ray spectrometers, portable and massive NaI(Tl) detectors. The MCA_Rad gamma-ray spectrometry system was designed and built up at LNL for measuring large amount of samples with a minimum attendance: these features fit perfectly with the requirements of this project. This system is able to measure any type of materials (solid, liquid, gas), and due to the high efficiency and its geometric symmetry, absolute activity measurements are possible with systematic errors below 5%. http://www.fe.infn.it/u/mantovani/CV/Proceedings/Bezzon_10b.pd
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