Three-dimensional topological insulators host surface states with linear dispersion, which manifest as a Dirac cone. Nanoscale transport measurements provide direct access to the transport properties ...of the Dirac cone in real space and allow the detailed investigation of charge carrier scattering. Here, we use scanning tunnelling potentiometry to analyse the resistance of different kinds of defects at the surface of a (Bi0.53Sb0.47)2Te3 topological insulator thin film. The largest localized voltage drop we find to be located at domain boundaries in the topological insulator film, with a resistivity about four times higher than that of a step edge. Furthermore, we resolve resistivity dipoles located around nanoscale voids in the sample surface. The influence of such defects on the resistance of the topological surface state is analysed by means of a resistor network model. The effect resulting from the voids is found to be small compared to the other defects.
A combined theoretical and experimental study reveals evidence for the dual
topological insulating character of the stoichiometric natural superlattice
phase ...$\mathrm{Bi_{1}Te_{1}}=\mathrm{Bi_{2}_{1}Bi_{2}Te_{3}_{2}}$, being a
stack of alternating Bi bilayers and two quintuple layers of
$\mathrm{Bi_{2}Te_{3}}$. We identify $\mathrm{Bi_{1}Te_{1}}$ by density
functional theory to exhibit a non trivial time-reversal symmetry-driven
character of $\mathbb{Z}_{2}=(0;001)$ and additionally a mirror-symmetry
induced mirror Chern number of $n_{{\cal M}}=-2$, which indicates that
$\mathrm{Bi_{1}Te_{1}}$ is both a weak topological insulator and a topological
crystalline insulator. The coexistence of the two phenomena preordains distinct
crystal planes to host topological surface states that are protected by the
respective symmetries. The surface perpendicular to the stacking direction is
the 'dark' surface of the weak topological insulator, while hosting
mirror-symmetry protected surface states along the $\bar{\Gamma\mathrm{M}}$
direction at non-time-reversal invariant momenta points. We confirm the
stacking sequence of our MBE-grown $\mathrm{Bi_{1}Te_{1}}$ thin films by X-ray
diffraction and transmission electron microscopy, and find indications of the
topological crystalline and weak topological character in the surface
electronic spin structure by spin- and angle-resolved photoemission
spectroscopy, which nicely match the results from density functional theory.
This article presents UMICore, a software tool for the demonstration and visualization of various physical layer concepts as well as various channel models. The capabilities of UMICore are ...illustrated using UMTS LTE as exemplary physical layer with different chaYXB1-00438-A012nnel models.
Implementation of the National Kidney Foundation-Dialysis Outcomes Quality Initiative (NKF-DOQI) Guidelines for the treatment of the anemia of chronic renal failure is a great challenge to all ...concerned with the improvement in the quality of life and survival of patients with chronic renal failure. These include physicians, nurses, technicians, dietitians, social workers, administrators, and private and public (Health Care Financing Administration) payers of the care. The principles of the process of implementation are reviewed and the barriers that can prevent implementation are discussed, showing how most of these can be overcome. Several of the more controversial Guidelines are discussed in detail, showing that with protocols that address the means for implementation, the goals of these Guidelines can be achieved.
A combined theoretical and experimental study reveals evidence for the dual topological insulating character of the stoichiometric natural superlattice phase ...\(\mathrm{Bi_{1}Te_{1}}=\mathrm{Bi_{2}_{1}Bi_{2}Te_{3}_{2}}\), being a stack of alternating Bi bilayers and two quintuple layers of \(\mathrm{Bi_{2}Te_{3}}\). We identify \(\mathrm{Bi_{1}Te_{1}}\) by density functional theory to exhibit a non trivial time-reversal symmetry-driven character of \(\mathbb{Z}_{2}=(0;001)\) and additionally a mirror-symmetry induced mirror Chern number of \(n_{{\cal M}}=-2\), which indicates that \(\mathrm{Bi_{1}Te_{1}}\) is both a weak topological insulator and a topological crystalline insulator. The coexistence of the two phenomena preordains distinct crystal planes to host topological surface states that are protected by the respective symmetries. The surface perpendicular to the stacking direction is the 'dark' surface of the weak topological insulator, while hosting mirror-symmetry protected surface states along the \(\bar{\Gamma\mathrm{M}}\) direction at non-time-reversal invariant momenta points. We confirm the stacking sequence of our MBE-grown \(\mathrm{Bi_{1}Te_{1}}\) thin films by X-ray diffraction and transmission electron microscopy, and find indications of the topological crystalline and weak topological character in the surface electronic spin structure by spin- and angle-resolved photoemission spectroscopy, which nicely match the results from density functional theory.
Hemodialyzer reuse: Estimation of area loss from clearance data. A procedure is described for estimating the loss in effective membrane area of a dialyzer during repeated reuse. The technique ...involves the accurate measurement of dialyzer clearance both before and after reuse. Either large or small molecule clearance can be used to estimate the area loss and clearances can be determined either in vivo or in vitro following the dialysis. Excellent agreement has been obtained between theoretical estimates of fiber bundle loss in hollow fiber artificial kidneys (based on clearance data) and values determined by saline rinse techniques. It should be possible to extend this theoretical procedure to flat-plate dialyzers for which there is no analogous procedure to fiber bundle loss for determining loss in effective membrane area with repeated reuse. Extension of the procedure to determine area losses for coil dialyzers is not recommended.
Réutilisation d'hémodialyseur: Évaluation de la perte de surface au moyen des valeurs de clearance. Un procédé d'estimation de la perte de surface efficace de la membrane d'un dialyseur au cours des réutilisations itératives est décrit. La technique implique la détermination précise de la clearance du dialyseur avant et après réutilisation. Les clearances des grosses ou des petites molécules peuvent être utilisées pour évaluer la perte de surface. Les clearances peuvent être déterminées soit in vivo soit in vitro après la dialyse. Une excellente concordance a été obtenue entre les évaluations théoriques (fondées sur les valeurs des clearances) de pertes de faisceaux de fibres dans des reins artificiels à fibres creuses et les valeurs déterminées par les techniques de rinçage avec du soluté salé. Il devrait être possible d'étendre ce procédé théorique aux dialyseurs en plaques pour lesquels il n'existe pas de procédé analogue à celui utilisé avec des fibres creuses pour déterminer la perte de membrane efficace en fonction de la réutilisation. L'extension du procédé aux dialysuers à bobine nest pas recommandée.
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