Pectoral Sandpiper Calidris melanotos: first record for Tanzania

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Infrainguinal arterial reconstruction with non-reversed autologous vein after angioscopy guided valvulotomy ex situ

Aims:The advantages of in situ autologous vein grafts for long infrainguinal arterial reconstructions are the tapered conduit, minimising size mismatch at proximal and distal anastomoses, and the possibility of using small sized veins with good results. Unfortunately, in about 30% of legs the ipsilateral saphenous vein is inadequate rendering in situ bypass grafting impossible. To profit from a valveless autologous vein graft in these cases we routinely performed ex situ valvulotomy after harvesting the contralateral saphenous vein or good quality segments of the ipsilateral saphenous vein.Methods:The ex situ valvulotomy was performed under angioscopic guidance using a flushing-type Mill's valvulotome.Results:Fifty non reversed grafts in 46 patients entered a prospective surveillance program. Primary and primary-assisted patency rates at 2 years were 68% and 82% respectively, early graft thrombosis 2%, late stenosis 8% and major amputation rate with a patent graft 6%. No technique related problems were noticed.Conclusion:Angioscopy guided valvulotomy was safe and simple and allowed good quality control of the veins. The presented results in this study are comparable to other recently reported series of in situ bypass. The clinical use of small flexible endoscopes allows a safe and atraumatic valvulotomy and simultaneous quality control of autologous vein grafts

A simple method for measuring plasma power in rf-GDOES instruments

A method for determining plasma power in rf-GDOES is presented. It is based on an effective resistance located in the inductive coil of the impedance matching. The amount of electrical power consumed in the matching system depends on the capacitive current flowing through the matching system, which depends on the applied voltage, the stray capacity, and the frequency. This correction method is experimentally evaluated and compared with the integral plasma power calculatio

Theory and simulation of photogeneration and transport in Si-SiOx superlattice absorbers

Si-SiOx superlattices are among the candidates that have been proposed as high band gap absorber material in all-Si tandem solar cell devices. Owing to the large potential barriers for photoexited charge carriers, transport in these devices is restricted to quantum-confined superlattice states. As a consequence of the finite number of wells and large built-in fields, the electronic spectrum can deviate considerably from the minibands of a regular superlattice. In this article, a quantum-kinetic theory based on the non-equilibrium Green's function formalism for an effective mass Hamiltonian is used for investigating photogeneration and transport in such devices for arbitrary geometry and operating conditions. By including the coupling of electrons to both photons and phonons, the theory is able to provide a microscopic picture of indirect generation, carrier relaxation, and inter-well transport mechanisms beyond the ballistic regime

Theory and simulation of quantum photovoltaic devices based on the non-equilibrium Green's function formalism

This article reviews the application of the non-equilibrium Green's function formalism to the simulation of novel photovoltaic devices utilizing quantum confinement effects in low dimensional absorber structures. It covers well-known aspects of the fundamental NEGF theory for a system of interacting electrons, photons and phonons with relevance for the simulation of optoelectronic devices and introduces at the same time new approaches to the theoretical description of the elementary processes of photovoltaic device operation, such as photogeneration via coherent excitonic absorption, phonon-mediated indirect optical transitions or non-radiative recombination via defect states. While the description of the theoretical framework is kept as general as possible, two specific prototypical quantum photovoltaic devices, a single quantum well photodiode and a silicon-oxide based superlattice absorber, are used to illustrated the kind of unique insight that numerical simulations based on the theory are able to provide.Comment: 20 pages, 10 figures; invited review pape

SU(2) symmetry in a Hubbard model with spin-orbit coupling

We study the underlying symmetry in a spin-orbit coupled tight-binding model with Hubbard interaction. It is shown that, in the absence of the on-site interaction, the system possesses the SU(2) symmetry arising from the timereversal symmetry. The influence of the on-site interaction on the symmetry depends on the topology of the networks: The SU(2) symmetry is shown to be the spin rotation symmetry of a simply-connected lattice, so it still holds in the presence of the Hubbard correlation. In contrary, the on-site interaction breaks the SU(2) symmetry of a multi-connected lattice.Comment: 5 pages, 2 figure

Analytical solutions for semiconductor luminescence including Coulomb correlations with applications to dilute bismides

In this paper we introduce analytical solutions of interband polarization, which is the self-energy of the Dyson equation for the photon Green’s functions, and apply them to studying photoluminescence of Coulomb-correlated semiconductor materials. The accuracy of the easily programmable solutions is proven by consistently demonstrating the low-temperature s-shape of the luminescence peak of dilute bismide semiconductors. The different roles of homogeneous versus inhomogeneous broadening at low and high temperatures are described, as well as the importance of many body effects, which are in very good agreement with experiments

Disability quotas: past or future policy?

This article considers the issues associated with the use of quota systems for the employment of workers with a disability. It examines the use and experiences of such quotas in Italy, Russia and the United Kingdom. Italy has a long established quota for the employment of such workers, whilst the modern Russian system it is a more recent innovation. In contrast the UK abandoned its quotas in the 1990s. We draw on the experiences of the three countries to consider generally whether the use of quotas is either an acceptable means of encouraging employers to take on disabled workers, or is necessary to achieve this objective