Exponential Temperature Dependence of Penetration Depth in Single Crystal MgB_2

The temperature dependence of the London penetration depth,lambda(T), was measured in both single crystal and polycrystalline MgB_2 samples by a high-resolution, radio frequency technique. A clear exponential temperature dependence of lambda(T) was observed at low temperature, indicating s-wave pairing. A BCS fit to the lowest temperature data gives an in-plane energy gap Delta of 2.6\pm0.2 meV (2\Delta/T_c=1.5\pm0.1), which is significantly smaller than the standard BCS weak coupling value of 3.5. We find that the data are best described by a two-gap model.Comment: Minor corrections added, as per published articl

Selenoxopropadienylidene (CCCSe) as a bridging ligand

The reaction of [W(≡CC≡CSiMe3)(CO)2(Tp*)] (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) with [nBu4N]F and selenium in the presence of [RuCl(PPh3)2(η-C5H5)] affords a mixture of the tricarbido complex [WRu(μ-CCC)(CO)2(PPh3)2(η-C5H5)(Tp*)] and the selenoxopropadienylidene (C3Se) complex [WRu(μ-CCCSe)(CO)2(PPh3)2(η-C5H5)(Tp*)], both of which were structurally characterized. The formation of the bimetallic C3Se complex is consistent with the intermediacy of the salt [nBu4N] [W(≡CC≡CSe)(CO)2(Tp*)], which could be observed spectroscopically and computationally interrogated, but not yet isolated.This work was supported by the Australian Research Council (DP130102598 and DP110101611)

Pump-and-probe optical transmission phase shift as a quantitative probe of the Bogoliubov dispersion relation in a nonlinear channel waveguide

We theoretically investigate the dispersion relation of small-amplitude optical waves superimposing upon a beam of polarized monochromatic light propagating along a single-mode channel waveguide characterized by an instantaneous and spatially local Kerr nonlinearity. These small luminous fluctuations propagate along the waveguide as Bogoliubov elementary excitations on top of a one-dimensional dilute Bose quantum fluid evolve in time. They consequently display a strongly renormalized dispersion law, of Bogoliubov type. Analytical and numerical results are found in both the absence and the presence of one- and two-photon losses. Silicon and silicon-nitride waveguides are used as examples. We finally propose an experiment to measure this Bogoliubov dispersion relation, based on a stimulated four-wave mixing and interference spectroscopy techniques.Comment: 17 pages, 7 figure

Hydrogen vs. Battery in the long-term operation. A comparative between energy management strategies for hybrid renewable microgrids

The growth of the world’s energy demand over recent decades in relation to energy intensity and demography is clear. At the same time, the use of renewable energy sources is pursued to address decarbonization targets, but the stochasticity of renewable energy systems produces an increasing need for management systems to supply such energy volume while guaranteeing, at the same time, the security and reliability of the microgrids. Locally distributed energy storage systems (ESS) may provide the capacity to temporarily decouple production and demand. In this sense, the most implemented ESS in local energy districts are small–medium-scale electrochemical batteries. However, hydrogen systems are viable for storing larger energy quantities thanks to its intrinsic high mass-energy density. To match generation, demand and storage, energy management systems (EMSs) become crucial. This paper compares two strategies for an energy management system based on hydrogen-priority vs. battery-priority for the operation of a hybrid renewable microgrid. The overall performance of the two mentioned strategies is compared in the long-term operation via a set of evaluation parameters defined by the unmet load, storage efficiency, operating hours and cumulative energy. The results show that the hydrogen-priority strategy allows the microgrid to be led towards island operation because it saves a higher amount of energy, while the battery-priority strategy reduces the energy efficiency in the storage round trip. The main contribution of this work lies in the demonstration that conventional EMS for microgrids’ operation based on battery-priority strategy should turn into hydrogen-priority to keep the reliability and independence of the microgrid in the long-term operation

Substituição da espiga de milho desintegrada com palha e sabugo pela mandioca integral seca na alimentação de equinos.

O objetivo de estudar a viabilidade da substituição parcial/total da espiga de milho desintegrada ecom palha e sabugo (MDPS) pela mandioca integral (raiz + parte aérea) seca (MIS) ao sol, na alimentação de poltras da raça Arabe, por meio de consumo, ganho de peso e coeficiente de digestibilidade(CD) da MS, PB, FB, e EB

A Violência no Local de Trabalho em Instituições de Saúde: Um Estudo Monocêntrico sobre Causas, Consequências e Estratégias de Prevenção

Introduction: Workplace violence is one of the main risk factors in the professional world. Healthcare workers are at higher risk when compared to other sectors. Our study aimed to characterize physical and verbal violence in a public hospital and to define occupational health prevention and surveillance strategies. Material and Methods: Single center observational cross-sectional study, carried amongst healthcare workers in a public hospital in Lisbon. A qualitative survey was carried out through six in-depth interviews. A quantitative survey was carried through questionnaires delivered to 32 workers. A significance level of 5% was accepted in the assessment of statistical differences. The Mann-Whitney test and the Fisher’s exact test were used to calculate p values. Results: The main results are: (1) 41 violence incidents were reported in the quantitative phase; (2) 5/21 [23.81%] victims notified the incident to the occupational health department; (3) 18/21 [85.71%] victims reported a permanent state of hypervigilance; (4) 22/28 [78.57%] participants self-reported poor or no familiarity with internal reporting procedures; (5) 24/28 [85.71%] participants believed it is possible to minimize workplace violence. Discussion: Workplace violence is favored by unrestricted access to working areas, absence of security guards and police officers or scarce intervention. The low notification rate contributes to organizational lack of action. The state of hypervigilance reported in our study reflects the negative effects of threatening occupational stressors on mental health. Conclusion: Our results show that workplace violence is a relevant risk factor that significantly impacts workers’ health in a noxious manner, deserving a tailored occupational health approach whose priority areas and strategies have been determined.Introdução: A violência no local de trabalho é um dos principais fatores de risco no mundo do trabalho. Os trabalhadores da saúde apresentam um risco superior. O nosso estudo teve como objetivo caracterizar a violência física e verbal num hospital público e definir estratégias de prevenção e vigilância em saúde ocupacional. Material e Métodos: Estudo observacional transversal monocêntrico, conduzido num hospital público em Lisboa com trabalhadores da saúde. Foi realizado um inquérito qualitativo com entrevistas em profundidade a seis trabalhadores e um inquérito quantitativo com questionários a 32 trabalhadores. Aceitou-se um nível de significância de 5% na avaliação das diferenças estatísticas. O teste de Mann-Whitney e o teste exato de Fisher foram usados para calcular os valores de p. Resultados: Os principais resultados são: (1) 41 episódios reportados na fase quantitativa; (2) 5/21 [23,81%] vítimas notificaram o incidente; (3) 18/21 [85.71%] vítimas reportaram estados de hipervigilância permanente; (4) 22/28 [78,57%] participantes não conheciam ou conheciam mal os procedimentos de notificação; (5) 24/28 [85,71%] consideravam possível minimizar o problema. Discussão: A violência é favorecida pelo acesso livre às zonas de trabalho, ausência de agentes de segurança e polícia ou falta da respetiva intervenção. A baixa notificação contribui para a ausência de medidas organizacionais. O estado de hipervigilância relatado reflete o efeito prejudicial da exposição a fontes de stress e ameaça. Conclusão: A violência no local de trabalho é um fator de risco relevante, com impacto negativo na saúde dos trabalhadores e merece uma abordagem individualizada no âmbito da saúde ocupacional, cujas áreas e estratégias prioritárias foram definidas neste estudo. Palavras-chave: Fatores de Risco Profissionais; Prevenção; Saúde Ocupacional; Trabalhadores da Saúde; Violência no Local de trabalho.info:eu-repo/semantics/publishedVersio

Quantum transport in quantum networks and photosynthetic complexes at the steady state

Recently, several works have analysed the efficiency of photosynthetic complexes in a transient scenario and how that efficiency is affected by environmental noise. Here, following a quantum master equation approach, we study the energy and excitation transport in fully connected networks both in general and in the particular case of the Fenna-Matthew-Olson complex. The analysis is carried out for the steady state of the system where the excitation energy is constantly "flowing" through the system. Steady state transport scenarios are particularly relevant if the evolution of the quantum system is not conditioned on the arrival of individual excitations. By adding dephasing to the system, we analyse the possibility of noise-enhancement of the quantum transport.Comment: 10 pages, single column, 6 figures. Accepted for publication in Plos On

Relativistic Klein-Gordon charge effects by information-theoretic measures

The charge spreading of ground and excited states of Klein-Gordon particles moving in a Coulomb potential is quantitatively analyzed by means of the ordinary moments and the Heisenberg measure as well as by use of the most relevant information-theoretic measures of global (Shannon entropic power) and local (Fisher's information) types. The dependence of these complementary quantities on the nuclear charge Z and the quantum numbers characterizing the physical states is carefully discussed. The comparison of the relativistic Klein-Gordon and non-relativistic Schrodinger values is made. The non-relativistic limits at large principal quantum number n and for small values of Z are also reached.Comment: Accepted in New Journal of Physic

Characteristic features of the temperature dependence of the surface impedance in polycrystalline MgB2_2 samples

The real $R_s(T)$ and imaginary $X_s(T)$ parts of the surface impedance $Z_s(T)=R_s(T)+iX_s(T)$ in polycrystalline MgB$_2$ samples of different density with the critical temperature $T_c\approx 38$ K are measured at the frequency of 9.4 GHz and in the temperature range $5\le T<200$ K. The normal skin-effect condition $R_s(T)=X_s(T)$ at $T\ge T_c$ holds only for the samples of the highest density with roughness sizes not more than 0.1 $\mu$m. For such samples extrapolation $T\to 0$ of the linear at $T<T_c/2$ temperature dependences $\lambda_L(T)=X_s(T)/\omega\mu_0$ and $R_s(T)$ results in values of the London penetration depth $\lambda_L(0)\approx 600$ \AA and residual surface resistance $R_{res}\approx 0.8$ m$\Omega$. In the entire temperature range the dependences $R_s(T)$ and $X_s(T)$ are well described by the modified two-fluid model.Comment: 7 pages, 3 figures. Europhysics Letters, accepted for publicatio

Evidence for Surface Andreev Bound states in Cuprate Superconductors from Penetration Depth Measurements

Tunneling and theoretical studies have suggested that Andreev bound states form at certain surfaces of unconventional superconductors. Through studies of the temperature and field dependence of the in-plane magnetic penetration depth lambda_ab at low temperature, we have found strong evidence for the presence of these states in clean single crystal YBCO and BSCCO. Crystals cut to expose a [110] interface show a strong upturn in lambda_ab at around 7K, when the field is oriented so that the supercurrents flow around this surface. In YBCO this upturn is completely suppressed by a field of ~0.1 T.Comment: 4 pages 2 column revtex + 4 postscript figures. Submitted to PR