161 research outputs found

    Are There Any Redshift >8 Gamma-Ray Bursts in the BATSE Catalog?

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    Several luminosity indicators have been found for Gamma-Ray Bursts (GRBs) wherein measurable light curve and spectral properties are well-correlated with the peak luminosity. Several papers have each applied one different luminosity relation to find redshifts for BATSE GRBs and claim to identify specific bursts with z>8. The existence of such high redshift events is not surprising, as BATSE has enough sensitivity to see them and GRBs are expected out to the redshift of the first star formation. To improve results we used five luminosity relations with updated calibrations to determine redshifts with error bars. Combining these relations, we calculated the redshifts of 36 BATSE GRBs with claimed z>8. Our results include 13 bursts with our derived best redshift z_best>8, which looks promising at first. But the calculated redshift uncertainties are significantly large in these selected cases. With only one exception, all of our bursts have z_1siglow<9. The one exception (BATSE trigger 2035) is likely a short duration burst at z>~4. Our best case for a very high redshift event is BATSE trigger 3142 with z_best>20 and z_1siglow=8.9, however we can only say z>4.1 at the two-sigma confidence level. In all, we cannot point toward any one BATSE burst as confidently having z>8. One implication is to greatly weaken prior claims that GRBs have a steeply rising rate-density out to high redshifts.Comment: ApJ in press, 18 page

    Assessment of hydrogen storage in activated carbons produced from hydrothermally treated organic materials

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    12 activated carbons (ACs) were prepared by KOH activation using hydrochars as precursors. These hydrochars were prepared by hydrothermal carbonisation (HTC) of sucrose solutions at concentrations ranging from 0.2 to 1.6 mol L-1. The KOH to hydrochar weight ratio (W) was varied from 1 to 5, and the activation temperature was set to 1023K. ACs texture was assessed by nitrogen and carbon dioxide adsorption at 77 and 273 K, respectively; pore size distribution was calculated by using both isotherms and the SAIEUS© software. ACs with surface areas between 790 and 2240 m2 g-1 were obtained. Hydrogen excess adsorption was determined at 298K and pressures up to 10 MPa in a volumetric device, and the isosteric heat of adsorption (Qst) was calculated for four ACs, using hydrogen isotherms obtained at 278, 298 and 308K. Potassium intercalation between graphitic planes was assumed to account for the high Qst values, 7-8 kJ mol-1. Hydrogen uptake at 2 MPa was compared with hydrogen adsorption data of 38 other ACs reported in the open literature. Hydrogen adsorption fundamentally depends on micropore volume and preliminary HTC did not enhance hydrogen storage although it could be a good strategy for doping carbon with heteroelements.The authors gratefully acknowledge the financial support of the CPER 2007-2013 “Structuration du Pôle de Compétitivité Fibres Grand’Est” (Competitiveness Fibre Cluster), through local (Conseil Général des Vosges), regional (Région Lorraine), national (DRRT and FNADT) and European (FEDER) funds. Part of this work was supported by CHEERS project (FEDER funds) and the COST Action MP1103 “Nanostructured materials for solid-state hydrogen storage”.Peer reviewe

    Editorial: Participatory Evaluation and Impact Assessment in Citizen Science

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    Editorial to the fteval Journal's special issue #5

    Transforming identities and co-constructing careers of career counselors

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    New theories for practice, which take account of contextual shifts such as labor market volatility, are essential for maintaining the professional status of career counseling. Career construction theory (CCT), as an exemplar of an innovative, contextually sensitive approach not only provides a way of making sense of the turbulent landscapes in which career transitions are taking place, but also provides practical tools to facilitate individual adaptation to change. However, development and evaluation of new theories and related tools have tended to overlook the career development and support needs of career counselors in the adoption and integration of these approaches into their practice with clients, as well as into their own career development. Here, the focus is on supporting the continuing professional development of career counselors as crucial for the enhancement of practice, through the provision in 2017 of an open access online learning program relating to the changing world of work, with facilitation of dialogue and reflection. The adaptive responses of an international group of participants facing challenges of identity transformation in the workplace, which emerged as they worked through the online learning resource, are examined. Four hundred and two international participants registered, with 86 actively engaging in the course, which was made available over three months, with content analysis of their online dialogue providing insights into the processes of psycho-social adaptation to the career-related challenges they faced. The learning design and course delivery were underpinned by the theory of professional identity transformation (PIT), with a commitment to supporting participants both individually collectively to shape their evolving roles and identities in ways compatible with their life themes. In order to progress toward that goal, processes of co-construction, also central to career construction theory, emerged strongly from the content analysis of data

    Empowering Public Employment Service Practitioners’ peer facilitation with peer coaching training

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    In a changing world of work with high youth unemployment rates, an ageing society and flexible work force, practitioners in Public Employment Services need to cope with continually growing demands. In this paper we present the EmployID project which introduced a blended learning approach for Public Employment Services in Croatia, designed to support professional identity transformation through peer facilitation and learning. The evaluation shows that learners benefited from higher knowledge and skills development related to peer coaching, along with an increase in activities related to collaborative, reflective learning

    Supercritical fluid extraction of corn germ oil: Study of the influence of process parameters on the extraction yield and oil quality

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    The supercritical fluid extraction of corn germ oil has been studied in this work. Extractions were carried out at different pressure, temperature and flow rate to analyze the influence of these variables on the extraction kinetics and the oil quality obtained. Extraction curves are initially linear with a slope close to the oil solubility value in supercritical CO2. Based on these results a mathematical model was successfully applied to describe the extraction curves. Characterization of supercritical crude corn oil was performed by determining some physical parameters such as refraction index, density and color. Additionally, the fatty acid composition, neutral lipids, the content of tocopherols, acid index, peroxide value, antioxidant capacity and the oxidative stability were determined in the corn oil extracted. Fatty acid composition was compared with that for crude germ oil and no significant differences between the oils extracted by both methods were found. Oxidative stability test using the Rancimat showed that supercritical CO2 extracted corn oil is less protected against oxidation than n-hexane extracted oils
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