4,150 research outputs found

    Extragalactic Source Counts in the Spitzer 24-micron Band: What Do We Expect From ISOCAM 15-micron Data and Models?

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    The comparison between the new Spitzer data at 24 micron and the previous ISOCAM data at 15 micron is a key tool to understand galaxy properties and evolution in the infrared and to interpret the observed number counts, since the combination of Spitzer with the ISO cosmological surveys provides for the first time the direct view of the Universe in the Infrared up to z~2. We present the prediction in the Spitzer 24-micron band of a phenomenological model for galaxy evolution derived from the 15-micron data. Without any ``a posteriori'' update, the model predictions seem to agree well with the recently published 24-micron extragalactic source counts, suggesting that the peak in the 24-micron counts is dominated by ``starburst'' galaxies like those detected by ISOCAM at 15 micron, but at higher redshifts (1 < z < 2 instead of 0.5 < z < 1.5).Comment: 8 pages: 4 pages of main text + 5 postscript figures, use aastex. Accepted for publication in ApJL. Replaced with the proof version (added missing references and corrected a few sentences

    A New Method for ISOCAM Data Reduction - I. Application to the European Large Area ISO Survey Southern Field: Method and Results

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    We have developed a new data reduction technique for ISOCAM LW data and have applied it to the European Large Area ISO Survey (ELAIS) LW3 (15 micron) observations in the southern hemisphere (S1). This method, known as LARI technique and based on the assumption of the existence of two different time scales in ISOCAM transients (accounting either for fast or slow detector response), was particularly designed for the detection of faint sources. In the ELAIS S1 field we obtained a catalogue of 462 15 micron sources with signal-to-noise ratio >= 5 and flux densities in the range 0.45 - 150 mJy (filling the whole flux range between the Deep ISOCAM Surveys and the IRAS Faint Source Survey). The completeness at different flux levels and the photometric accuracy of this catalogue have been tested with simulations. Here we present a detailed description of the method and discuss the results obtained by its application to the S1 LW3 data.Comment: 20 pages, LaTeX, MNRAS style, 20 postscript figures, full catalogue not yet available at http://boas5.bo.astro.it/~elais/catalogues/. Accepted for publication in MNRA

    Local scale multiple quantitative risk assessment and uncertainty evaluation in a densely urbanised area (Brescia, Italy)

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    Abstract. The study of the interactions between natural and anthropogenic risks is necessary for quantitative risk assessment in areas affected by active natural processes, high population density and strong economic activities. We present a multiple quantitative risk assessment on a 420 km2 high risk area (Brescia and surroundings, Lombardy, Northern Italy), for flood, seismic and industrial accident scenarios. Expected economic annual losses are quantified for each scenario and annual exceedance probability-loss curves are calculated. Uncertainty on the input variables is propagated by means of three different methodologies: Monte-Carlo-Simulation, First Order Second Moment, and point estimate. Expected losses calculated by means of the three approaches show similar values for the whole study area, about 64 000 000 € for earthquakes, about 10 000 000 € for floods, and about 3000 € for industrial accidents. Locally, expected losses assume quite different values if calculated with the three different approaches, with differences up to 19%. The uncertainties on the expected losses and their propagation, performed with the three methods, are compared and discussed in the paper. In some cases, uncertainty reaches significant values (up to almost 50% of the expected loss). This underlines the necessity of including uncertainty in quantitative risk assessment, especially when it is used as a support for territorial planning and decision making. The method is developed thinking at a possible application at a regional-national scale, on the basis of data available in Italy over the national territory

    Integration of natural and technological risks in Lombardy, Italy

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    Abstract. Multi-risk assessment is becoming a valuable tool for land planning, emergency management and the deployment of mitigation strategies. Multi-risk maps combine all available information about hazard, vulnerability, and exposed values related to different dangerous phenomena, and provide a quantitative support to complex decision making. We analyse and integrate through an indicator-based approach nine major threats affecting the Lombardy Region (Northern Italy, 25 000 km2), namely landslide, avalanche, flood, wildfire, seismic, meteorological, industrial (technological) risks; road accidents, and work injuries. For each threat, we develop a set of indicators that express the physical risk and the coping capacity or system resilience. By combining these indicators through different weighting strategies (i.e. budgetary allocation, and fuzzy logic), we calculate a total risk for each threat. Then, we integrate these risks by applying AHP (Analytic Hierarchy Process) weighting, and we derive a set of multi-risk maps. Eventually, we identify the dominant risks for each zone, and a number of risk hot-spot areas. The proposed approach can be applied with different degree of detail depending on the quality of the available data. This allows the application of the method even in case of non homogeneous data, which is often the case for regional scale analyses. Moreover, it allows the integration of different risk types or metrics. Relative risk scores are provided from this methodology, not directly accounting for the temporal occurrence probability of the phenomena

    A study on factors that drive variation in the levels of social capital among people living with HIV/AIDS in Iran

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    INTRODUCTION: Social capital is increasingly used in relation to health issues, particularly in sexually transmitted diseases/infections and health behaviors. Experiences indicated that social capital can contribute in changing HIV related risk behaviors and a decline of HIV infection through social groups and networking and make more effective use of HIV/AIDS prevention, care, and treatment services. We aimed to assess social capital in these persons through a quantitative study. METHOD: This cross-sectional study was performed with a convenience sample of 300 people living HIV/AIDS referred to a counseling center of behavioral diseases, in Imam Khomeini Hospital, in Tehran, the capital of Iran, during September 2011 to May 2012. Data collection tools were a demographic questionnaire and World Bank Social Capital Questionnaire (SC-IQ). The analysis of data was performed by the SPSS statistic software version 18. To identify factors influencing social capital in participations, Pearson correlation coefficient, ANOVA, t-test, and a multiple regression were applied. The significant level was considered 0.05 in this study. RESULTS: 165 (55) were male and the rest female. The mean age of participants was 34.3 ± 7.5. The mean score of total social capital was 2.34 ± 0.5 in all participants. The domain of individual trust had the highest mean score (2.53 ± 0.66). The lowest mean score was related to the domain of social trust and associative relations (2.23 ± 0.62). Variables such as ethnicity, age, and middle economic status had a significant impact on the domain of individual trust so that the mean score of this component of social capital was lower among women (0.396) than men. Factors affecting total social capital were ethnicity and middle economic status. CONCLUSION: Finding emphasized on the role of economic status, ethnicity and gender in persons living with HIV/AIDS. Thus recommended that policy makers and program managers consider social groups and networks, especially in women in the design and delivery of intervention strategies to reduce HIV transmission

    Tight lower bound to the geometric measure of quantum discord

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    Dakic, Vedral and Brukner [Physical Review Letters \tf{105},190502 (2010)] gave a geometric measure of quantum discord in a bipartite quantum state as the distance of the state from the closest classical quantum (or zero discord) state and derived an explicit formula for a two qubit state. Further, S.Luo and S.Fu [Physical Review A \tf{82}, 034302 (2010)] obtained a generic form of this geometric measure for a general bipartite state and established a lower bound. In this brief report we obtain a rigorous lower bound to the geometric measure of quantum discord in a general bipartite state which dominates that obtained by S.Luo and S.Fu.Comment: 10 pages,2 figures. In the previous versions, a constraint was ignored while optimizing the second term in Eq.(5), in which case, only a lower bound on the geometric discord can be obtained. The title is also consequently changed. Accepted in Phys.Rev.

    Study of wind waves using satellite altimetry in the coast of south-western Caspian Sea (Gilan Province)

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    576-581Waves are an important phenomena in the sea but in view of complicated nature are difficult to study. This research, with the aim of showing a primary research on satellite altimetry, studied significant wave height in offshore waters near Gilan province in the south-east of Caspian region during 2014. So wave’s data including significant wave height and wind speed were obtained in a time interval from satellite. The significant wave height data were verified with buoy significant wave height data and their graphs generated. Using wave data and SPM method, the significant wave height and wave period obtained. The contour figure of significant wave height was depicted. The comparison of satellite significant wave height data and result of SPM method by buoy data showed that the satellite data has less error than SPM method result. The result of this research has shown that the effective parameters on wind waves are formation of high and low pressure atmospheric system. The maximum value of mean altimetry significant wave height is 0.70 m in November and 0.80 m in December. The maximum of significant wave height occurs in north portion of study region. The dominate direction of waves is north-western in coasts of Gilan province

    On the nature of the ISO-selected sources in the ELAIS S2 region

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    We have studied the optical, near-IR and radio properties of a complete sample of 43 sources detected at 15-micron in one of the deeper ELAIS repeatedly observed region. The extragalactic objects in this sample have 15-micron flux densities in the range 0.4-10 mJy, where the source counts start diverging from no evolution models. About 90% of the sources (39 out of 43) have optical counterparts brighter than I=21 mag. Eight of these 39 sources have been identified with stars on the basis of imaging data, while for another 22 sources we have obtained optical spectroscopy, reaching a high identification percentage (30/43, ~70%). All but one of the 28 sources with flux density > 0.7 mJy are identified. Most of the extragalactic objects are normal spiral or starburst galaxies at moderate redshift (z_med~0.2); four objects are Active Galactic Nuclei. We have used the 15-micron, H_alpha and 1.4-GHz luminosities as indicators of star-formation rate and we have compared the results obtained in these three bands. While 1.4-GHz and 15-micron estimates are in good agreement, showing that our galaxies are forming stars at a median rate of ~40 Mo/yr, the raw H_alpha-based estimates are a factor ~5-10 lower and need a mean correction of ~2 mag to be brought on the same scale as the other two indicators. A correction of ~2 mag is consistent with what suggested by the Balmer decrements H_alpha/H_beta and by the optical colours. Moreover, it is intermediate between the correction found locally for normal spirals and the correction needed for high-luminosity 15-micron objects, suggesting that the average extinction suffered by galaxies increases with infrared luminosity.Comment: 19 pages, 11 figures (3 in JPEG format), MNRAS, accepte

    Multipartite entanglement in fermionic systems via a geometric measure

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    We study multipartite entanglement in a system consisting of indistinguishable fermions. Specifically, we have proposed a geometric entanglement measure for N spin-1/2 fermions distributed over 2L modes (single particle states). The measure is defined on the 2L qubit space isomorphic to the Fock space for 2L single particle states. This entanglement measure is defined for a given partition of 2L modes containing m >= 2 subsets. Thus this measure applies to m <= 2L partite fermionic system where L is any finite number, giving the number of sites. The Hilbert spaces associated with these subsets may have different dimensions. Further, we have defined the local quantum operations with respect to a given partition of modes. This definition is generic and unifies different ways of dividing a fermionic system into subsystems. We have shown, using a representative case, that the geometric measure is invariant under local unitaries corresponding to a given partition. We explicitly demonstrate the use of the measure to calculate multipartite entanglement in some correlated electron systems. To the best of our knowledge, there is no usable entanglement measure of m > 3 partite fermionic systems in the literature, so that this is the first measure of multipartite entanglement for fermionic systems going beyond the bipartite and tripartite cases.Comment: 25 pages, 8 figure

    Entanglement Capacity of Nonlocal Hamiltonians : A Geometric Approach

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    We develop a geometric approach to quantify the capability of creating entanglement for a general physical interaction acting on two qubits. We use the entanglement measure proposed by us for NN-qubit pure states (PRA \textbf{77}, 062334 (2008)). Our procedure reproduces the earlier results (PRL \textbf{87}, 137901 (2001)). The geometric method has the distinct advantage that it gives an experimental way to monitor the process of optimizing entanglement production.Comment: 8 pages, 1 figure
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