1,972 research outputs found

    A search for lines in the bright X-ray afterglow of GRB120711A

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    GRB120711A, discovered and rapidly localized by the INTEGRAL satellite, attracted particular interest due to its high gamma-ray fluence, very bright X-ray afterglow, and the detection of a prompt optical transient and of long-lasting emission at GeV energies. A follow-up observation carried out with the XMM-Newton satellite has provided an X-ray spectrum in the 0.3-10 keV with unprecedented statistics for a GRB afterglow 20 hours after the burst. The spectrum is well fit by a power-law with photon index 1.87+-0.01, modified by absorption in our Galaxy and in the GRB host at z=1.4. A Galactic absorption consistent with that estimated from neutral hydrogen observations is obtained only with host metallicity lower than 0.05 of the Solar value. We report the results of a sensitive search for emission and absorption lines using the matched filter smoothing method (Rutledge and Sako 2003). No statistically significant lines were found. The upper limits on the equivalent width of emission lines, derived through Monte Carlo simulations, are few tens of eV, a factor about 10 lower than that of the possible lines reported in the literature for other bursts.Comment: Accepted for publication in A&

    WHY DO RESEARCHERS COLLABORATE WITH INDUSTRY? AN ANALYSIS OF THE WINE SECTOR IN CHILE, SOUTH AFRICA AND ITALY

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    This paper explores the determinants of the linkages between industry and research organizations – including universities. We present new evidence on three wine producing areas – Piedmont, a region of Italy, Chile, South Africa - that have successfully reacted to the recent structural changes experienced in the industry worldwide. Based on an original data-set, we carry out an econometric exercise to study the microeconomic determinants of researchers' collaborations with industry. The evidence reveals that individual researcher characteristics, such as embeddedness in the academic system, age and sex, matter more than their publishing record or formal degrees.University-Industry Linkages, Innovation System, Wine Sector, Emerging Economies

    Clusters of firms in space and time

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    The use of the K-functions (Ripley, 1977) has become recently popular in the analysis of the spatial pattern of firms. It was first introduced in the economic literature by Arbia and Espa (1996) and then popularized by Marcon and Puech (2003), Quah and Simpson (2003), Duranton and Overman (2005) and Arbia et al. (2008). In particular in Arbia et al. (2008) we used Ripley’s K-functions as instruments to study the inter-sectoral co-agglomeration pattern of firms in a single moment of time. All this researches have followed a static approach, disregarding the time dimension. Temporal dynamics, on the other hand, play a crucial role in understanding the economic and social phenomena, particularly when referring to the analysis of the individual choices leading to the observed clusters of economic activities. With respect to the contributions previously appeared in the literature, this paper uncovers the process of firm demography by studying the dynamics of localization through space-time K-functions. The empirical part of the paper will focus on the study of the long run localization of firms in the area of Rome (Italy), by concentrating on the ICT sector data collected by the Italian Industrial Union in the period 1920- 2005.Agglomeration, Non-parametric measures; Space-time K-functions, Spatial clusters, Spatial econometrics.

    Neutrinoless double-beta decay

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    This paper introduces the neutrinoless double-beta decay the rarest nuclear weak process and describes the status of the research for this transition, both from the point of view of theoretical nuclear physics and in terms of the present and future experimental scenarios. Implications of this phenomenon on crucial aspects of particle physics are briefly discussed. The calculations of the nuclear matrix elements in case of mass mechanisms are reviewed, and a range for these quantities is proposed for the most appealing candidates. After introducing general experimental concepts—such as the choice of the best candidates, the different proposed technological approaches, and the sensitivity—we make the point on the experimental situation. Searches running or in preparation are described, providing an organic presentation which picks up similarities and differences. A critical comparison of the adopted technologies and of their physics reach in terms of sensitivity to the effective Majorana neutrino mass is performed. As a conclusion, we try to envisage what we expect round the corner and at a longer time scaleThis work was partially supported by the MICINN (Spain) (FPA2011-29854) ; by the Comunidad de Madrid (Spain) (HEPHACOS S2009-ESP-1473); by the Spanish Consolider-Ingenio 2010 Program, CPAN (CSD2007-00042

    Analysis of heat kernel highlights the strongly modular and heat-preserving structure of proteins

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    In this paper, we study the structure and dynamical properties of protein contact networks with respect to other biological networks, together with simulated archetypal models acting as probes. We consider both classical topological descriptors, such as the modularity and statistics of the shortest paths, and different interpretations in terms of diffusion provided by the discrete heat kernel, which is elaborated from the normalized graph Laplacians. A principal component analysis shows high discrimination among the network types, either by considering the topological and heat kernel based vector characterizations. Furthermore, a canonical correlation analysis demonstrates the strong agreement among those two characterizations, providing thus an important justification in terms of interpretability for the heat kernel. Finally, and most importantly, the focused analysis of the heat kernel provides a way to yield insights on the fact that proteins have to satisfy specific structural design constraints that the other considered networks do not need to obey. Notably, the heat trace decay of an ensemble of varying-size proteins denotes subdiffusion, a peculiar property of proteins

    A convex optimization approach for automated water and energy end use disaggregation

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    A detailed knowledge of water consumption at an end-use level is an essential requirement to design and evaluate the efficiency of water saving policies. In the last years, this has led to the development of automated tools to disaggregate high resolution water consumption data at the household level into end use categories. In this work, a new disaggregation algorithm is presented. The proposed algorithm is based on the assumption that the disaggregated signals to be identified are piecewise constant over the time and it exploits the information on the time-of-day probability in which a specific water use event might occur. The disaggregation problem is formulated as a convex optimization problem, whose solution can be efficiently computed through numerical solvers. Specifically, the disaggregation problem is treated as a least-square error minimization problem, with an additional (convex) penalty term aiming at enforcing the disaggregate signals to be piece-wise constant over the time. The proposed disaggregation algorithm has been initially tested against household electricity data available in the literature. The obtained results look promising and similar results are expected to be obtained for water data

    Improving the Protection of Aquatic Ecosystems by Dynamically Constraining Reservoir Operation Via Direct Policy Conditioning

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    Water management problems generally involve conflicting and non-commensurable objectives. Assuming a centralized perspective at the system-level, the set of Pareto-optimal alternatives represents the ideal solution of most of the problems. Yet, in typical real-world applications, only a few primary objectives are explicitly considered, taking precedence over all other concerns. These remaining concerns are then internalized as static constraints within the problem's formulation. This approach yields to solutions that fail to explore the full set of objectives tradeoffs. In this paper, we propose a novel method, called direct policy conditioning (DPC), that combines direct policy search, multi-objective evolutionary algorithms, and input variable selection to design dynamic constraints that change according to the current system conditions. The method is demonstrated for the management problem of the Conowingo Dam, located within the Lower Susquehanna River, USA. The DPC method is used to identify environmental protection mechanisms and is contrasted with traditional static constraints de fining minimum environmental flow requirements. Results show that the DPC method identifies a set of dynamically constrained control policies that overcome the current alternatives based on the minimum environmental flow constraint, in terms of environmental protection but also of the primary objectives

    Effects of olive and pomegranate by-products on human microbiota : a study using the SHIME (R) in vitro simulator

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    Two by-products containing phenols and polysaccharides, a "pate" (OP) from the extra virgin olive oil milling process and a decoction of pomegranate mesocarp (PM), were investigated for their effects on human microbiota using the SHIME (R) system. The ability of these products to modulate the microbial community was studied simulating a daily intake for nine days. Microbial functionality, investigated in terms of short chain fatty acids (SCFA) and NH4+, was stable during the treatment. A significant increase in Lactobacillaceae and Bifidobacteriaceae at nine days was induced by OP mainly in the proximal tract. Polyphenol metabolism indicated the formation of tyrosol from OP mainly in the distal tract, while urolithins C and A were produced from PM, identifying the human donor as a metabotype A. The results confirm the SHIME (R) system as a suitable in vitro tool to preliminarily investigate interactions between complex botanicals and human microbiota before undertaking more challenging human studies
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