910 research outputs found

    Organocatalysis and beyond: Activating reactions with two catalytic species

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    Since the beginning of the millennium, organocatalysis has been gaining a predominant role in asymmetric synthesis and it is, nowadays, a foundation of catalysis. Synergistic catalysis, combining two or more different catalytic cycles acting in concert, exploits the vast knowledge acquired in organocatalysis and other fields to perform reactions that would be otherwise impossible. Merging organocatalysis with photo-, metallo- and organocatalysis itself, researchers have ingeniously devised a range of activations. This feature review, focusing on selected synergistic catalytic approaches, aims to provide a flavor of the creativity and innovation in the area, showing ground-breaking examples of organocatalysts, such as proline derivatives, hydrogen bond-mediated, Cinchona alkaloids or phosphoric acids catalysts, which work cooperatively with different catalytic partners

    Thermal effects in freeze-in neutrino dark matter production

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    We present a detailed study of the production of dark matter in the form of a sterile neutrino via freeze-in from decays of heavy right-handed neutrinos. Our treatment accounts for thermal effects in the effective couplings, generated via neutrino mixing, of the new heavy neutrinos with the Standard Model gauge and Higgs bosons and can be applied to several low-energy fermion seesaw scenarios featuring heavy neutrinos in thermal equilibrium with the primordial plasma. We find that the production of dark matter is not as suppressed as to what is found when considering only Standard Model gauge interactions. Our study shows that the freeze-in dark matter production could be efficient

    Designing and conducting qualitative research across countries and cultures: challenges for inclusiveness and rigour

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    Qualitative research is fundamental to understanding the nature and complexity of human phenomena. While cultural and psychometric validations exist for quantitative tools, the same cannot be said of qualitative ones. There are other many challenges when conducting a multinational qualitative study, which includes different cultural and linguistic 'biases'. This paper presents some key issues that researchers may encounter when designing and developing multinational and multicultural qualitative studies, and also provides some strategies to overcome difficulties and ensure rigour

    Indole Synthesis Using Silver Catalysis

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    Indoles are amongst the most important class of heteroaromatics in organic chemistry, being commonly found in biologically active natural products and therapeutically useful compounds. The synthesis of indoles is therefore important and several methods for their synthesis that make use of silver(I) catalysts and reagents have been developed in recent years. This Focus Review contains, to the best of our knowledge, a comprehensive coverage of silver-mediated indole forming reactions since the first reaction of this type was reported in 2004

    Model independent bounds on the tau lepton electromagnetic and weak magnetic moments

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    Using LEP1, SLD and LEP2 data, for tau lepton production, and data from CDF, D0 and LEP2, for W decays into tau leptons, we set model independent limits on non-standard electromagnetic and weak magnetic moments of the tau lepton. The most general effective Lagrangian giving rise to tau moments is used without further assumptions. Precise bounds (2σ2\sigma) on the non-standard model contributions to tau electromagnetic (0.007<aγ<0.005-0.007<a_\gamma< 0.005), tau Z-magnetic (0.0024<aZ<0.0025-0.0024 <a_Z< 0.0025) and tau W-magnetic (0.003<κW<0.004-0.003 < \kappa^W < 0.004) dipole moments are set from the analysis.Comment: 19 pages, 2 figures, elsart.sty. Revised version with new data. Accepted for publication in Nucl. Phys.

    Desarrollo, seguimiento y evaluación de la formación especializada en el modelo troncal.

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    La implantación de la troncalidad en la formación sanitaria especializada en España es el cambio más profundo y complejo que se introduce en la regulación del sistema de formación especializada desde el año 1978. Este hecho hace imprescindible la puesta en marcha de un conjunto de elementos estructurales, organizativos y de acción dirigidos específicamente a garantizar que el proceso se implante siguiendo las premisas y calendarios previstos en las disposiciones legales que le dan soporte y de acuerdo con conceptos y evidencias científicamente fundados y que traduzcan también la experiencia acumulada en España y otros países en relación con estos temas

    Synthesis of 4-substituted-1,2-dihydroquinolines by means of gold-catalyzed intramolecular hydroarylation reaction of n-ethoxycarbonyl-n-propargylanilines

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    An alternative Au(I)-catalyzed synthetic route to functionalized 1,2-dihydroquinolines is reported. This novel approach is based on the use of N-ethoxycarbonyl protected-Npropargylanilines as building blocks that rapidly undergo the IMHA reaction affording the 6-endo cyclization product in good to high yields. In the presence of N-ethoxycarbonyl-N-propargyl-metasubstituted anilines, the regiodivergent cyclization at the ortho-/para-position is achieved by the means of catalyst fine tuning

    Bounds on the Tau Magnetic Moments: Standard Model and Beyond

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    We obtain new bounds for the magnetic dipole moments of the tau lepton. These limits on the magnetic couplings of the tau to the electroweak gauge bosons (gamma, W, Z) are set in a model independent way using the most general effective Lagrangian with the SU(2)_L x U(1)_Y symmetry. Comparison with data from the most precise experiments at high energies shows that the present limits are more stringent than the previous published ones. For the anomalous magnetic moment the bounds are, for the first time, within one order of magnitude of the standard model prediction.Comment: 8 pages, 1 figure; to appear in the proceedings of the 6th International Workshop on Tau Lepton Physics, 18-21 September (2000), Victoria (Canada

    Lepton flavor violation induced by dark matter

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    CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOGuided by gauge principles we discuss a predictive and falsifiable UV complete model where the Dirac fermion that accounts for the cold dark matter abundance in our Universe induces the lepton flavor violation (LFV) decays mu -gt; e gamma and mu -gt; eee as well as mu - e conversion. We explore the interplay between direct dark matter detection, relic density, collider probes and lepton flavor violation to conclusively show that one may have a viable dark matter candidate yielding flavor violation signatures that can be probed in the upcoming experiments. In fact, keeping the dark matter mass at the TeV scale, a sizable LFV signal is possible, while reproducing the correct dark matter relic density and meeting limits from direct-detection experiments.977111CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOsem informação2016/01343-
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