Pressure induced magnetic and magnetocaloric properties in NiCoMnSb Heusler alloy

The effect of pressure on the magnetic and the magnetocaloric properties around the martensitic transformation temperature in NiCoMnSb Heusler alloy has been studied. The martensitic transition temperature has significantly shifted to higher temperatures with pressure, whereas the trend is opposite with the application of applied magnetic field. The maximum magnetic entropy change around the martensitic transition temperature for Ni45Co5Mn38Sb12 is 41.4 J/kg K at the ambient pressure, whereas it is 33 J/kg K at 8.5 kbar. We find that by adjusting the Co concentration and applying suitable pressure, NiCoMnSb system can be tuned to achieve giant magnetocaloric effect spread over a large temperature span around the room temperature, thereby making it a potential magnetic refrigerant material for applications.Comment: 16 pages, 5 figure

Robustness of bipartite Gaussian entangled beams propagating in lossy channels

Subtle quantum properties offer exciting new prospects in optical communications. Quantum entanglement enables the secure exchange of cryptographic keys and the distribution of quantum information by teleportation. Entangled bright beams of light attract increasing interest for such tasks, since they enable the employment of well-established classical communications techniques. However, quantum resources are fragile and undergo decoherence by interaction with the environment. The unavoidable losses in the communication channel can lead to a complete destruction of useful quantum properties -- the so-called "entanglement sudden death". We investigate the precise conditions under which this phenomenon takes place for the simplest case of two light beams and demonstrate how to produce states which are robust against losses. Our study sheds new light on the intriguing properties of quantum entanglement and how they may be tamed for future applications.Comment: To be published - Nature Photonic

Disentanglement in Bipartite Continuous-Variable Systems

Entanglement in bipartite continuous-variable systems is investigated in the presence of partial losses, such as those introduced by a realistic quantum communication channel, e.g. by propagation in an optical fiber. We find that entanglement can vanish completely for partial losses, in a situa- tion reminiscent of so-called entanglement sudden death. Even states with extreme squeezing may become separable after propagation in lossy channels. Having in mind the potential applications of such entangled light beams to optical communications, we investigate the conditions under which entanglement can survive for all partial losses. Different loss scenarios are examined and we derive criteria to test the robustness of entangled states. These criteria are necessary and sufficient for Gaussian states. Our study provides a framework to investigate the robustness of continuous-variable entanglement in more complex multipartite systems.Comment: Phys. Rev. A (in press

Prevalência do uso de diagnóstico genético pré-Implantação na Unidade Clínica de Paramiloidose do Centro Hospitalar do Porto

Introduction: The Familial Amyloid Polyneuropathy, with the world’s largest focus in Portugal, is recognized by the National Board of Assisted Reproductive Technologies as a serious disease eligible for Preimplantation Genetic Diagnosis. This study aims to determine the prevalence of the use of Preimplantation Genetic Diagnosis in FAP carriers followed in Unidade Clínica de Paramiloidose, Centro Hospitalar do Porto, and to identify the associated factors. Material and Methods: Between January and May 2013, a representative sample of Portuguese Familial Amyloid Polyneuropathy carriers, aged between 18 and 55 years, was systematically recruited. The analysis is based on 111 carriers with previous familial diagnosis, who reported having ever tried to get pregnant after 2001. Data on sociodemographic characteristics and use of Preimplan¬tation Genetic Diagnosis were collected through a self-administered questionnaire. Proportions were compared using the chi-square test. Crude and adjusted odds ratios (OR) and the respective confidence intervals of 95% (95% CI) were estimated using multivariate logistic regression. Results: The prevalence of use of Preimplantation Genetic Diagnosis was 20.7% (95% CI: 13.6-29.5). After adjustment, a household income above 1000 €/month (OR = 11.87; 95% CI 2.87-49.15) was directly associated with the use of Preimplantation Genetic Diag¬nosis, while carriers with an individual diagnosis (OR = 0.15; 95% CI 0.04-0.57) and children born after 2001 (OR = 0.07; 95% CI 0.02- 0.32) revealed a prevalence of use significantly lower than those with a individual diagnosis and children born before 2001. Discussion: The low prevalence of use of Preimplantation Genetic Diagnosis, as well as the less frequent use of the technique by those with a lower household income, shows the importance of improving access to Preimplantation Genetic Diagnosis in the case of Familial Amyloid Polyneuropathy. Conclusion: This work contributes to increase the sensitivity of health professionals around the use and accessibility to Preimplanta¬tion Genetic Diagnosis among Familial Amyloid Polyneuropathy carriers.This study was based on the Public Health Master’s thesis by Kátia Valdrez, presented at the Faculty of Medicine of the University of Porto and is supported by FEDER funding through the COMPETE program and by National funding by the FCT – Fundação para a Ciência e Tecnologia through FCOMP-01-0124-FEDER-014453 (FCT PTDC/CS-ECS/110220/2009) project and the Investigador FCT (IF/00956/2013) progra

Central and tensor components of three-nucleon forces in low-energy proton-deuteron scattering

Contributions of three-nucleon forces (3NF) to proton-deuteron scattering observables at energies below the deuteron breakup threshold are studied by solving the Faddeev equation that includes the Coulomb interaction. At E_p=3.0 MeV, we find that the central part of a two-pion exchange 3NF removes the discrepancy between measured cross sections and the calculated ones by two-nucleon forces, and improves the agreement with T_{22} experimental data. However, the tensor part of the 3NF fails in reproducing data of the analyzing power T_{21} by giving worse agreement between the measured and the calculated. Detailed examinations of scattering amplitudes suggest that a P-wave contribution in spin quartet tensor amplitudes has unsuitable sign for reproducing the T_{21} data.Comment: 6 pages, 6 figure