3,757 research outputs found

    Investigation of complete and incomplete fusion in 7^{7}Li+124^{124}Sn reaction around Coulomb barrier energies

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    The complete and incomplete fusion cross sections for 7^{7}Li+124^{124}Sn reaction were measured using online and offline characteristic γ\gamma-ray detection techniques. The complete fusion (CF) cross sections at energies above the Coulomb barrier were found to be suppressed by \sim 26 \% compared to the coupled channel calculations. This suppression observed in complete fusion cross sections is found to be commensurate with the measured total incomplete fusion (ICF) cross sections. There is a distinct feature observed in the ICF cross sections, i.e., t\textit{t}-capture is found to be dominant than α\alpha-capture at all the measured energies. A simultaneous explanation of complete, incomplete and total fusion (TF) data was also obtained from the calculations based on Continuum Discretized Coupled Channel method with short range imaginary potentials. The cross section ratios of CF/TF and ICF/TF obtained from the data as well as the calculations showed the dominance of ICF at below barrier energies and CF at above barrier energies.Comment: 9 pages, 8 figure

    Unfolding of eigenvalue surfaces near a diabolic point due to a complex perturbation

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    The paper presents a new theory of unfolding of eigenvalue surfaces of real symmetric and Hermitian matrices due to an arbitrary complex perturbation near a diabolic point. General asymptotic formulae describing deformations of a conical surface for different kinds of perturbing matrices are derived. As a physical application, singularities of the surfaces of refractive indices in crystal optics are studied.Comment: 23 pages, 7 figure

    Theoretically Efficient Parallel Graph Algorithms Can Be Fast and Scalable

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    There has been significant recent interest in parallel graph processing due to the need to quickly analyze the large graphs available today. Many graph codes have been designed for distributed memory or external memory. However, today even the largest publicly-available real-world graph (the Hyperlink Web graph with over 3.5 billion vertices and 128 billion edges) can fit in the memory of a single commodity multicore server. Nevertheless, most experimental work in the literature report results on much smaller graphs, and the ones for the Hyperlink graph use distributed or external memory. Therefore, it is natural to ask whether we can efficiently solve a broad class of graph problems on this graph in memory. This paper shows that theoretically-efficient parallel graph algorithms can scale to the largest publicly-available graphs using a single machine with a terabyte of RAM, processing them in minutes. We give implementations of theoretically-efficient parallel algorithms for 20 important graph problems. We also present the optimizations and techniques that we used in our implementations, which were crucial in enabling us to process these large graphs quickly. We show that the running times of our implementations outperform existing state-of-the-art implementations on the largest real-world graphs. For many of the problems that we consider, this is the first time they have been solved on graphs at this scale. We have made the implementations developed in this work publicly-available as the Graph-Based Benchmark Suite (GBBS).Comment: This is the full version of the paper appearing in the ACM Symposium on Parallelism in Algorithms and Architectures (SPAA), 201

    Care seeking behaviour for childhood illness- a questionnaire survey in western Nepal

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    BACKGROUND: The World Health Organization estimates that seeking prompt and appropriate care could reduce child deaths due to acute respiratory infections by 20%. The purpose of our study was to assess care seeking behaviour of the mothers during childhood illness and to determine the predictors of mother's care seeking behaviour. METHODS: A cross-sectional survey was conducted in the immunization clinics of Pokhara city, Kaski district, western Nepal. A trained health worker interviewed the mothers of children suffering from illness during the preceding 15 days. RESULTS: A total of 292 mothers were interviewed. Pharmacies (46.2%) were the most common facilities where care was sought followed by allopathic medical practitioners (26.4%). No care was sought for 8 (2.7%) children and 26 (8.9%) children received traditional/home remedies. 'Appropriate', 'prompt' and 'appropriate and prompt' care was sought by 77 (26.4%), 166 (56.8%) and 33 (11.3%) mothers respectively. The mothers were aware of fever (51%), child becoming sicker (45.2%) and drinking poorly (42.5%) as the danger signs of childhood illness. By multiple logistic regression analysis total family income, number of symptoms, mothers' education and perceived severity of illness were the predictors of care seeking behaviour. CONCLUSION: The results of the present study show that the mothers were more likely to seek care when they perceived the illness as 'serious'. Poor maternal knowledge of danger signs of childhood illness warrants the need for a complementary introduction of community-based Integrated Management of Childhood Illness programmes to improve family's care seeking behaviour and their ability to recognize danger signs of childhood illness. Socioeconomic development of the urban poor may overcome their financial constraints to seek 'appropriate' and 'prompt' care during the childhood illness

    Electromagnetic transition from the 4+^+ to 2+^+ resonance in 8^8Be measured via the radiative capture in 4^4He+4^4He

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    An earlier measurement on the 4+^+ to 2+^+ radiative transition in 8^8Be provided the first electromagnetic signature of its dumbbell-like shape. However, the large uncertainty in the measured cross section does not allow a stringent test of nuclear structure models. The present paper reports a more elaborate and precise measurement for this transition, via the radiative capture in the 4^4He+4^4He reaction, improving the accuracy by about a factor of three. The {\it ab initio} calculations of the radiative transition strength with improved three-nucleon forces are also presented. The experimental results are compared with the predictions of the alpha cluster model and {\it ab initio} calculations.Comment: 5 pages and 7 figures, Submitted to Physical Review Letter

    The Wolf-Rayet binaries of the nitrogen sequence in the Large Magellanic Cloud: spectroscopy, orbital analysis, formation, and evolution

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    Massive Wolf-Rayet (WR) stars dominate the radiative and mechanical energy budget of galaxies and probe a critical phase in the evolution of massive stars prior to core-collapse. It is not known whether core He-burning WR stars (classical WR, cWR) form predominantly through wind-stripping (w-WR) or binary stripping (b-WR). With spectroscopy of WR binaries so-far largely avoided due to its complexity, our study focuses on the 44 WR binaries / binary candidates of the Large Magellanic Cloud (LMC, metallicity Z~0.5 Zsun), identified on the basis of radial velocity variations, composite spectra, or high X-ray luminosities. Relying on a diverse spectroscopic database, we aim to derive the physical and orbital parameters of our targets, confronting evolution models of evolved massive stars at sub-solar metallicity, and constraining the impact of binary interaction in forming them. Spectroscopy is performed using the Potsdam Wolf-Rayet (PoWR) code and cross-correlation techniques. Disentanglement is performed using the code Spectangular or the shift-and-add algorithm. Evolutionary status is interpreted using the Binary Population and Spectral Synthesis (BPASS) code, exploring binary interaction and chemically-homogeneous evolution. No obvious dichotomy in the locations of apparently-single and binary WN stars on the Hertzsprung-Russell diagram is apparent. According to commonly used stellar evolution models (BPASS, Geneva), most apparently-single WN stars could not have formed as single stars, implying that they were stripped by an undetected companion. Otherwise, it must follow that pre-WR mass-loss/mixing (e.g., during the red supergiant phase) are strongly underestimated in standard stellar evolution models.Comment: accepted to A&A on 10.05.2019; 69 pages (25 main paper + 44 appendix); Corrigendum: Shenar et al. 2020, A&A, 641, 2: An unfortunate typo in the implementation of the "transformed radius" caused errors of up to ~0.5dex in the derived mass-loss rates. This has now been correcte
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