764 research outputs found

    Ultrafast photodoping and effective Fermi-Dirac distribution of the Dirac particles in Bi2Se3

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    We exploit time- and angle- resolved photoemission spectroscopy to determine the evolution of the out-of-equilibrium electronic structure of the topological insulator Bi2Se. The response of the Fermi-Dirac distribution to ultrashort IR laser pulses has been studied by modelling the dynamics of the hot electrons after optical excitation. We disentangle a large increase of the effective temperature T* from a shift of the chemical potential mu*, which is consequence of the ultrafast photodoping of the conduction band. The relaxation dynamics of T* and mu* are k-independent and these two quantities uniquely define the evolution of the excited charge population. We observe that the energy dependence of the non-equilibrium charge population is solely determined by the analytical form of the effective Fermi-Dirac distribution.Comment: 5 Pages, 3 Figure

    Circular dichroism and bilayer splitting in the normal state of underdoped (Pb,Bi)2_2Sr2_2(Cax_xY1x_{1-x})Cu2_2O8+δ_{8+\delta} and overdoped (Pb,Bi)2_2Sr2_2CaCu2_2O8+δ_{8+\delta}

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    We report an ARPES investigation of the circular dichroism in the first Brillouin zone (BZ) of under- and overdoped Pb-Bi2212 samples. We show that the dichroism has opposite signs for bonding and antibonding components of the bilayer-split CuO-band and is antisymmetric with respect to reflections in both mirror planes parallel to the c-axis. Using this property of the energy and momentum intensity distributions we prove the existence of the bilayer splitting in the normal state of the underdoped compound and compare its value with the splitting in overdoped sample. In agreement with previous studies the magnitude of the interlayer coupling does not depend significantly on doping. We also discuss possible origins of the observed dichroism.Comment: 4 RevTex pages, 4 EPS figure

    Evidence of reduced surface electron-phonon scattering in the conduction band of Bi_{2}Se_{3} by non-equilibrium ARPES

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    The nature of the Dirac quasiparticles in topological insulators calls for a direct investigation of the electron-phonon scattering at the \emph{surface}. By comparing time-resolved ARPES measurements of the TI Bi_{2}Se_{3} with different probing depths we show that the relaxation dynamics of the electronic temperature of the conduction band is much slower at the surface than in the bulk. This observation suggests that surface phonons are less effective in cooling the electron gas in the conduction band.Comment: 5 pages, 3 figure

    COMPARATIVE ANALYSIS OF TECHNICAL, ECONOMICAL AND ENVIRONMENTAL FEASIBILITY OF COGENERATION PLANT USING WOOD BIOMASS

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    After having identified, in a previous work [6], the possible sites for the location of a new cogeneration plant using wood biomass in the Mountain Community of Carnia, Friuli Venezia Giulia Region (Italy), the technical and economic feasibility and environmental sustainability of such a system has been carried out in order to evaluate the feasibility of the proposed solution

    Health care providers' perception of the frequent emergency department user issue and of targeted case management interventions: a cross-sectional national survey in Switzerland

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    Frequent users of emergency departments (FUEDs) (≥5 ED visits/year) represent a vulnerable population with complex needs accounting for a significant number of emergency department (ED) consultations, thus contributing to EDs overcrowding. Research exploring ED staff perceptions of FUEDs is scarce. The current study aimed to evaluate in ED staff a) the extent to which FUEDs are perceived as an issue; b) their perceived levels of knowledge and understanding of FUEDs; c) levels of perceived usefulness of case management (CM) and interest in implementing this intervention in their ED service. Head physicians of the EDs at all public hospitals in Switzerland (of various level of specialization) were sent a 19-item web-based survey, pilot tested prior to its dissemination. The head physicians were asked to forward the survey to ED staff members from different health professional backgrounds. The hospital response rate was 81% (85/106). The exploitable hospital response rate was 71% (75/106 hospitals) including 208 responding health professionals. Issues and difficulties around FUEDs were perceived as important by 64% of respondents. The perceived frequency of being confronted with FUEDs was higher among nurses in more specialized EDs. In total, 64% of respondents felt poorly informed about FUEDs, nurses feeling less informed than physicians. The understanding of FUEDs was lower in the French-Italian-speaking parts (FISP) of Switzerland than in the German-speaking part. Eighty-one percent of respondents had no precise knowledge of FUED-related interventions. The perceived usefulness of CM interventions after receiving explanations about it was high (92%). However, the overall level of interest for CM implementation was 59%. The interest in CM by physicians was low across all regions and ED categories. Nurses, on the other hand, showed more interest, especially those in EDs of high specialization. The majority of ED staff reported being confronted with FUEDs on a regular basis. Staff perceived FUEDs as a vulnerable population, yet, they felt poorly informed about how to manage the issue. The majority of ED staff thought a CM intervention would be useful for FUEDs, however there appears to be a gap in their desire or willingness to implement such interventions

    COMPARATIVE ANALYSIS OF TECHNICAL, ECONOMICAL AND ENVIRONMENTAL FEASIBILITY OF COGENERATION PLANT USING WOOD BIOMASS

    Get PDF
    After having identified, in a previous work [6], the possible sites for the location of a new cogeneration plant using wood biomass in the Mountain Community of Carnia, Friuli Venezia Giulia Region (Italy), the technical and economic feasibility and environmental sustainability of such a system has been carried out in order to evaluate the feasibility of the proposed solution

    Pulsed electric field processing of red grapes (cv. Rondinella): Modifications of phenolic fraction and effects on wine evolution

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    Pulsed electric field (PEF) is a non-thermal technology able to promote color and polyphenols extraction from grape skins. Most of the publications about PEF in winemaking report data concerning international varieties, poorly considering minor cultivars and the medium/long-term effects of the treatment on wine composition during storage. PEF was applied at different specific energies (2, 10, and 20 kJ kg\u20131) on grapes of the low-color red cv. Rondinella, after crushing-destemming. Pressing yield, the evolution of color, and total phenolic index (TPI) were measured during skin maceration. Moreover, the wines were characterized for basic compositional parameters, color, anthocyanin profile, phenolic composition (glories indices), metal content (Fe, Cr, and Ni), and sensory characters, two and twelve months after the processing, in comparison with untreated samples and pectolytic enzymes (PE). PEF did not affect fermentation evolution, nor did it modify wine basic composition or metal content. Treatments at 10 and 20 kJ kg\u20131 led to higher color and TPI in wines, in comparison to PE, because of increased content of anthocyanins and tannins. The sensory evaluation confirmed these findings. Modifications remained stable in wines after twelve months. Glories indices and vitisin A content highlighted greater potential stability of wine color in PEF-treated wines

    Chemical composition of microplastic in sediments and protected detritivores from different marine habitats (Salina Island)

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    This study estimates chemical composition of microplastic in sediments and benthic detritivores (sea cucumbers) collected from different marine rocky bottom habitat types (bank, landslide, cliff) of Salina Island (Aeolian Archipelago, Italy). Also, species richness and bottom coverings by benthic species were recorded at each sampling station. Correlations among chemical composition of microplastic in sediments and in detritivores were explored linking recorded variability to the factor \u201chabitat type\u201d. Results evidence that the habitat types considered in this study are characterized by wide species richness and by high percentages of bottom coverage by protected species by international conventions. In spite of the high ecological value of habitats considered in this study, microplastics were recorded both in sediments (PVC, PET, PE, PS, PA, PP) and in stomach contents of sea cucumbers (PET, PA) collected in all sampling sites, confirming the exposure of benthic species to microplastic pollution

    Risky substance use and peer pressure in Swiss young men : Test of moderation effects

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    Peer pressure (PP) toward misconduct is a well-known risk factor for substance use. However, the way it interacts with social factors and the associations of the aspects of PP other than PP toward misconduct have been understudied. This study examined the associations of three aspects of PP with risky substance use and tested whether the associations of PP toward misconduct were moderated by social factors. A representative sample of 5,680 young Swiss males completed a questionnaire assessing risky alcohol, cigarette, and cannabis use, PP toward misconduct, toward peer involvement, and toward peer conformity, as well as social support (SS) and neighbourhood cohesion. Multinomial logistic regression models were used. PP toward misconduct was positively associated with all substance use outcomes. The PP toward misconduct-risky alcohol use association was stronger in individuals reporting high than in those reporting low levels of PP toward peer involvement, SS, and neighbourhood cohesion. The PP toward misconduct-risky cannabis use association was stronger in individuals reporting high than in those reporting low levels of SS and neighbourhood cohesion. The PP toward misconduct-smoking association was stronger in individuals reporting high than in those reporting low levels of PP toward peer involvement. The risk for substance use associated with PP toward misconduct varies as a function of social factors. Being well connected with others (high level of PP toward peer involvement and SS), and living in a cohesive neighbourhood may amplify the risk for risky substance use associated with PP toward misconduct
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