209 research outputs found

    Field dependence of the magnetocaloric effect in core-shell nanoparticles

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    The field dependence of the magnetic entropy change peak at the low temperature surface spin freezing transition in chemically synthesized, monodispersed Co, Co–Ag, and Ni–Ag core-shell nanoparticles is studied, with the aim of gaining insight into the critical exponents of this transition. It is evidenced that although the magnitude of the peak entropy change and position of the peak can be tuned by changing the composition and nature (metallic or organic) of the shell and surfactant layers, the characteristics of the spin freezing transition are not altered. The field dependence of the refrigerant capacity also confirms this findin

    Nature of Sonoluminescence: Noble Gas Radiation Excited by Hot Electrons in "Cold" Water

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    We show that strong electric fields occurring in water near the surface of collapsing gas bubbles because of the flexoelectric effect can provoke dynamic electric breakdown in a micron-size region near the bubble and consider the scenario of the SBSL. The scenario is: (i) at the last stage of incomplete collapse of the bubble the gradient of pressure in water near the bubble surface has such a value and sign that the electric field arising from the flexoelectric effect exceeds the threshold field of the dynamic electrical breakdown of water and is directed to the bubble center; (ii) mobile electrons are generated because of thermal ionization of water molecules near the bubble surface; (iii) these electrons are accelerated in ''cold'' water by the strong electric fields; (iv) these hot electrons transfer noble gas atoms dissolved in water to high-energy excited states and optical transitions between these states produce SBSL UV flashes in the trasparency window of water; (v) the breakdown can be repeated several times and the power and duration of the UV flash are determined by the multiplicity of the breakdowns. The SBSL spectrum is found to resemble a black-body spectrum where temperature is given by the effective temperature of the hot electrons. The pulse energy and some other characteristics of the SBSL are found to be in agreement with the experimental data when realistic estimations are made.Comment: 11 pages (RevTex), 1 figure (.ps

    The brachiopod record in the Lower Toarcian (Jurassic) of the Rabaçal-Condeixa region (Portugal): stratigraphic distribution and palaeobiogeography

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    Se estudian los braquiópodos del Toarciense Inferior de la región de Rabaçal-Condeixa (Cuenca Lusitánica). En la Zona Polymorphum se ha registrado un conjunto muy diverso que incluye taxones de las provincias Noroeste Europea y Mediterránea. También se han encontrado en esta zona las especies típicas de la llamada “Fauna de Koninckella”, supuestamente asociada a ambientes profundos o pobres en oxígeno. Los Braquiópodos desaparecen en los primeros niveles de la Zona Levisoni, cuando comienza la sedimentación del miembro Calizas nodulosas en plaquetas de la Formación S. Gião. La recuperación coincide con el registro de Soaresirhynchia bouchardi, seguido de formas características de la “Fauna Española” - especies de Telothyris, Homoeorhynchia y Choffatirhynchia - que se encuentran también en los primeros niveles de la Zona Bifrons.São estudados os braquiópodes do Toarciano inferior da região de Rabaçal-Condeixa (Bacia Lusitânica). A Zona Polymorphum mostra uma associação muito diversa que inclui taxas das províncias do Noroeste da Europa e Mediterrânica. Registam-se igualmente nesta zona as espécies típicas da chamada “Fauna de Koninckella”, supostamente associada a ambientes sedimentares profundos ou pobres em oxigénio. Os Braquiópodes desaparecem nos primeiros níveis da Zona Levisoni, associados ao membro Calcários nodulosos em plaquetas da Formação de S. Gião. A recuperação coincide com o registo de Soaresirhynchia bouchardi, seguido de formas características da ”Fauna Espanhola” – espécies de Telothyris, Homoeorhynchia e Choffatirhynchia - que se encontram também nos primeiros níveis da Zona BifronsThe brachiopods from the Lower Toarcian of the Rabaçal- Condeixa (Lusitanian Basin) area are studied. A very diverse assemblage is recorded in the Polymorphum Zone, including both NW European and Mediterranean taxa. The typical species of the socalled “Koninckella Fauna”, that is supposedly associated to deep or oxigen-poor environments are also recorded throughout this Zone. Brachiopods disappear in the first levels of the Levisoni Zone and beginning of the Thin nodular limestones member of the S. Gião Formation. Brachiopods recovery is marked by the appearance of Soaresirhynchia bouchardi, followed by the typical representatives of the “Spanish Fauna” - species of Telothyris, Homoeorhynchia and Choffatirhynchia - that are distributed also in the first levels of the Bifrons ZoneDepto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasFALSEFundación Española para la Ciencia y la TecnologíaEspaña. Ministerio de Innovación y Cienciapu

    Chronic obstructive pulmonary disease subtypes. transitions over time

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    Background Although subtypes of chronic obstructive pulmonary disease are recognized, it is unknown what happens to these subtypes over time. Our objectives were to assess the stability of cluster-based subtypes in patients with stable disease and explore changes in clusters over 1 year. Methods Multiple correspondence and cluster analysis were used to evaluate data collected from 543 stable patients included consecutively from 5 respiratory outpatient clinics. Results Four subtypes were identified. Three of them, A, B, and C, had marked respiratory profiles with a continuum in severity of several variables, while the fourth, subtype D, had a more systemic profile with intermediate respiratory disease severity. Subtype A was associated with less dyspnea, better health-related quality of life and lower Charlson comorbidity scores, and subtype C with the most severe dyspnea, and poorer pulmonary function and quality of life, while subtype B was between subtypes A and C. Subtype D had higher rates of hospitalization the previous year, and comorbidities. After 1 year, all clusters remained stable. Generally, patients continued in the same subtype but 28% migrated to another cluster. Together with movement across clusters, patients showed changes in certain characteristics (especially exercise capacity, some variables of pulmonary function and physical activity) and changes in outcomes (quality of life, hospitalization and mortality) depending on the new cluster they belonged to Conclusions Chronic obstructive pulmonary disease clusters remained stable over 1 year. Most patients stayed in their initial subtype cluster, but some moved to another subtype and accordingly had different outcomes

    Microscopic Theory of Josephson Mesoscopic Constrictions

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    We present a microscopic theory for the d.c. Josephson effect in model mesoscopic constrictions. Our method is based on a non-equilibrium Green function formalism which allows for a self-consistent determination of the order parameter profile along the constriction. The various regimes defined by the different length scales (Fermi wavelength λF\lambda_F, coherence length ξ0\xi_0 and constriction length LCL_C) can be analyzed, including the case where all these lengths are comparable. For the case λF<~(LC,ξ0)\lambda_F \tilde{<} (L_C,\xi_0) phase oscillations with spatial period λF/2\lambda_F/2 can be observed. In the case of LC>ξ0L_C>\xi_0 solutions with a phase-slip center inside the constriction can be found, in agreement with previous phenomenological theories.Comment: 4 pages (RevTex 3.0), 3 postscript figures available upon request, 312456-C

    Barriers to ecological restoration in Europe: expert perspectives

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    Ecological restoration is key to counteracting anthropogenic degradation of biodiversity and to reducing disaster risk. However, there is limited knowledge of barriers hindering the wider implementation of restoration practices, despite high-level political priority to halt the loss of biodiversity. In Europe, progress on ecological restoration has been slow and insufficient to meet international agreements and comply with European Union Nature Directives. We assessed European restoration experts' perceptions on barriers to restoration in Europe, and their relative importance, through a multiple expert consultation using a Delphi process. We found that experts share a common multi-dimensional concept of ecological restoration. Experts identified a large number of barriers (33) to the advancement of ecological restoration in Europe. Major barriers pertained to the socio-economic, not the environmental, domain. The three most important being insufficient funding, conflicting interests among different stakeholders, and low political priority given to restoration. Our results emphasize the need to increase political commitment at all levels, comply with existing nature laws, and optimize the use of financial resources by increasing funds for ecological restoration and eradicate environmentally harmful subsidies. The experts also call for the integration of ecological restoration into land-use planning and facilitating stakeholders' collaboration. Our study identifies key barriers, discusses ways to overcome the main barriers to ER in Europe, and contributes knowledge to support the implementation of the European Biodiversity Strategy for 2030, and the EU 2030 Restoration Plan in particular. © 2021 The Authors. Restoration Ecology published by Wiley Periodicals LLC. on behalf of Society for Ecological Restoration.We are particularly thankful to experts participating in the Delphi process for their generosity in sharing their time and knowledge, and the European Chapter of the Society for Ecological Restoration (SERE), Réseau d'Échanges et de Valorisation en Écologie de la Restauration (REVER), Finnish Board on Ecological Restoration (FBER), Working Group on Ecological Restoration of the Spanish Association for Terrestrial Ecology (ER-AEET), Dutch Knowledge Network for Restoration and Management of Nature (OBN), German Restoration Network (GRN), UK Chartered Institute of Ecology and Environmental Management (CIEEM), Portuguese Network of Ecological Restoration (RPRE), Iberian Center for River Restoration (CIREF), and European Federation of Soil Bioengineering (EFIB) for suggesting candidates to the consulting process. We appreciate the support given by BiodivERsA (project funded under the EU Horizon 2020 ERA-NET COFUND scheme), and the EKLIPSE project (European Union Horizon 2020 grant agreement 690474), and particularly by Juliette C. Young. JCS research is financially supported by the Spanish Ministry of Science, Education and Universities and European Regional Development Funds (FEDER; project COSTERA, RTI2018-095954-B-I00). PMRG research is funded by the Portuguese Foundation for Science and Technology (FCT) through FCT Investigator Program grant number IF/00059/2015, and Centro de Estudos Florestais is supported by FCT grants UID/AGR/00239/2019 and UIDB/00239/2020

    A comprehensive review on carotenoids in foods and feeds: status quo, applications, patents, and research needs

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    Carotenoids are isoprenoids widely distributed in foods that have been always part of the diet of humans. Unlike the other so-called food bioactives, some carotenoids can be converted into retinoids exhibiting vitamin A activity, which is essential for humans. Furthermore, they are much more versatile as they are relevant in foods not only as sources of vitamin A, but also as natural pigments, antioxidants, and health-promoting compounds. Lately, they are also attracting interest in the context of nutricosmetics, as they have been shown to provide cosmetic benefits when ingested in appropriate amounts. In this work, resulting from the collaborative work of participants of the COST Action European network to advance carotenoid research and applications in agro-food and health (EUROCAROTEN, www.eurocaroten.eu, https://www.cost.eu/actions/CA15136/#tabs|Name:overview) research on carotenoids in foods and feeds is thoroughly reviewed covering aspects such as analysis, carotenoid food sources, carotenoid databases, effect of processing and storage conditions, new trends in carotenoid extraction, daily intakes, use as human, and feed additives are addressed. Furthermore, classical and recent patents regarding the obtaining and formulation of carotenoids for several purposes are pinpointed and briefly discussed. Lastly, emerging research lines as well as research needs are highlighted.This article is based upon work from COST Action (European network to advance carotenoid research and applications in agro-food and health, EUROCAROTEN, CA15136, www.eurocaroten.eu, https://www. cost.eu/actions/CA15136/#tabsjName:overview) supported by COST (European Cooperation in Science and Technology, http://www.cost. eu/).info:eu-repo/semantics/publishedVersio

    Measurement of the photon+b+b-jet production differential cross section in ppˉp\bar{p} collisions at \sqrt{s}=1.96~\TeV

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    We present measurements of the differential cross section dsigma/dpT_gamma for the inclusive production of a photon in association with a b-quark jet for photons with rapidities |y_gamma|< 1.0 and 30<pT_gamma <300 GeV, as well as for photons with 1.5<|y_gamma|< 2.5 and 30< pT_gamma <200 GeV, where pT_gamma is the photon transverse momentum. The b-quark jets are required to have pT>15 GeV and rapidity |y_jet| < 1.5. The results are based on data corresponding to an integrated luminosity of 8.7 fb^-1, recorded with the D0 detector at the Fermilab Tevatron ppˉp\bar{p} Collider at sqrt(s)=1.96 TeV. The measured cross sections are compared with next-to-leading order perturbative QCD calculations using different sets of parton distribution functions as well as to predictions based on the kT-factorization QCD approach, and those from the Sherpa and Pythia Monte Carlo event generators.Comment: 10 pages, 9 figures, submitted to Phys. Lett.

    Limits on anomalous trilinear gauge boson couplings from WW, WZ and Wgamma production in pp-bar collisions at sqrt{s}=1.96 TeV

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    We present final searches of the anomalous gammaWW and ZWW trilinear gauge boson couplings from WW and WZ production using lepton plus dijet final states and a combination with results from Wgamma, WW, and WZ production with leptonic final states. The analyzed data correspond to up to 8.6/fb of integrated luminosity collected by the D0 detector in pp-bar collisions at sqrt{s}=1.96 TeV. We set the most stringent limits at a hadron collider to date assuming two different relations between the anomalous coupling parameters Delta\kappa_\gamma, lambda, and Delta g_1^Z for a cutoff energy scale Lambda=2 TeV. The combined 68% C.L. limits are -0.057<Delta\kappa_\gamma<0.154, -0.015<lambda<0.028, and -0.008<Delta g_1^Z<0.054 for the LEP parameterization, and -0.007<Delta\kappa<0.081 and -0.017<lambda<0.028 for the equal couplings parameterization. We also present the most stringent limits of the W boson magnetic dipole and electric quadrupole moments.Comment: 10 pages, 5 figures, submitted to PL

    Search for pair production of the scalar top quark in muon+tau final states

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    We present a search for the pair production of scalar top quarks (t~1\tilde{t}_{1}), the lightest supersymmetric partners of the top quarks, in ppˉp\bar{p} collisions at a center-of-mass energy of 1.96 TeV, using data corresponding to an integrated luminosity of {7.3 fb1fb^{-1}} collected with the \dzero experiment at the Fermilab Tevatron Collider. Each scalar top quark is assumed to decay into a bb quark, a charged lepton, and a scalar neutrino (ν~\tilde{\nu}). We investigate final states arising from t~1t~1ˉbbˉμτν~ν~\tilde{t}_{1} \bar{\tilde{t}_{1}} \rightarrow b\bar{b}\mu\tau \tilde{\nu} \tilde{\nu} and t~1t~1ˉbbˉττν~ν~\tilde{t}_{1} \bar{\tilde{t}_{1}} \rightarrow b\bar{b}\tau\tau \tilde{\nu} \tilde{\nu}. With no significant excess of events observed above the background expected from the standard model, we set exclusion limits on this production process in the (mt~1m_{\tilde{t}_{1}},mν~m_{\tilde{\nu}}) plane.Comment: Submitted to Phys. Lett.
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