Band bending inversion in Bi2_2Se3_3 nanostructures

Shubnikov-de-Haas oscillations were studied under high magnetic field in Bi$_2$Se$_3$ nanostructures grown by Chemical Vapor Transport, for different bulk carrier densities ranging from $3\times10^{19}\text{cm}^{-3}$ to $6\times10^{17}\text{cm}^{-3}$. The contribution of topological surface states to electrical transport can be identified and separated from bulk carriers and massive two-dimensional electron gas. Band bending is investigated, and a crossover from upward to downward band bending is found at low bulk density, as a result of a competition between bulk and interface doping. These results highlight the need to control electrical doping both in the bulk and at interfaces in order to study only topological surface states.Comment: 6 pages, 4 figure

RSSI-based localization of a wireless sensor node with a flying robot

We consider the problem of navigating a ying robot to a specific sensor node within a wireless sensor network. This target sensor node periodically sends out beacons. The robot is capable of sensing the received signal strength of each received beacon (RSSI measurements). Existing approaches for solving the sensor spotting problem with RSSI measurements do not deal with noisy channel conditions and/or heavily depend on additional hardware capabilities. In this work we reduce RSSI uctuations due to noise by continuously sampling RSSI values and maintaining an exponential moving average (EMA). The EMA values enable us to detect significant decrease of the received signal strength. In this case it is reasoned that the robot is moving away from the sensor. We present two basic variants to decide a new moving direction when the robot moves away from the sensor. Our simulations show that our approaches outperform competing algorithms in terms of success rate and ight time. Infield experiments with real hardware, a ying robocopter successfully and quickly landed near a sensor placed in an outdoor test environment. Traces show robustness to additional environmental factors not accounted for in our simulations

Ziffern und ihre Anordnung im Flankerexperiment

Flankerexperimente tragen als weit verbreitetes Paradigma zur Aufklärung der Struktur visueller Aufmerksamkeit bei. Diese Studie untersucht in Anlehnung an frühere Studien die räumliche Struktur der Aufmerksamkeit in einem Flankerexperiment mit Ziffern in horizontaler und vertikaler Anordnung. Dazu wurden die Daten von 75 Probanden (40 männlich, 35 weiblich) im Alter zwischen 18 und 64 Jahren ausgewertet. Für die typischen Reaktionszeiten und die Fehlerraten wurden separate 2x2x2-faktorielle Varianzanalysen mit den Faktoren Anordnung und den beiden Flankerkompatibilitäten durchgeführt. Das Bild der Reaktionszeiten bestätigt frühere Befunde zur räumlichen Struktur der Aufmerksamkeit auch für die Verwendung von Ziffern: Horizontale Flanker haben einen stärkeren Effekt als vertikale Flanker und in Leserichtung vorhergehende (linke bzw. obere) Flanker haben einen stärkeren Effekt als nachfolgende (rechte bzw. untere) Flanker. In den Fehlerquoten ergibt sich in vertikaler Anordnung ein umgekehrtes Bild: Der untere Flanker hat einen stärkeren Einfluss auf die Fehlerrate als der obere Flanker. Die Befunde werden mit Bezug zu Lesegewohnheiten in die Verarbeitungskette aus Wahrnehmung, Klassifikation, Reaktionsgenerierung und Reaktionauswahl bei Flankerexperimenten eingeordnet und mit unterschiedlichen Wirkmechanismen auf Reaktionszeit und Fehlerrate erklärt. Weiterführende Experimente werden zur weiteren Untersuchung der Befunde vorgeschlagen

Parallel evolution of cox genes in H2S-tolerant fish as key adaptation to a toxic environment

Populations that repeatedly adapt to the same environmental stressor offer a unique opportunity to study adaptation, especially if there are a priori predictions about the genetic basis underlying phenotypic evolution. Hydrogen sulphide (H2S) blocks the cytochrome-c oxidase complex (COX), predicting the evolution of decreased H2S susceptibility of the COX in three populations in the Poecilia mexicana complex that have colonized H2S-containing springs. Here, we demonstrate that decreased H2S susceptibility of COX evolved in parallel in two sulphide lineages, as evidenced by shared amino acid substitutions in cox1 and cox3 genes. One of the shared substitutions likely triggers conformational changes in COX1 blocking the access of H2S. In a third sulphide population, we detect no decreased H2S susceptibility of COX, suggesting that H2S resistance is achieved through another mechanism. Our study thus demonstrates that even closely related lineages follow both parallel and disparate molecular evolutionary paths to adaptation in response to the same selection pressure

Catalyst-free Growth of Single Crystalline Bi 2 Se 3 Nanostructures for Quantum Transport Studies

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Band Bending Inversion in Bi₂Se₃ Nanostructures

Shubnikov–de Haas oscillations were studied under high magnetic field in Bi₂Se₃ nanostructures grown by chemical vapor transport, for different bulk carrier densities ranging from 3 × 10¹⁹ cm^–3 to 6 × 10¹⁷ cm^–3. The contribution of topological surface states to electrical transport can be identified and separated from bulk carriers and massive two-dimensional electron gas. Band bending is investigated, and a crossover from upward to downward band bending is found at low bulk density as a result of a competition between bulk and interface doping. These results highlight the need to control electrical doping both in the bulk and at interfaces in order to study only topological surface states

Search for pair-produced vector-like B quarks in proton-proton collisions at s\sqrt{s} = 8 TeV

A search for the production of a heavy B quark, having electric charge -1/3 and vector couplings to W, Z, and H bosons, is carried out using proton-proton collision data recorded at the CERN LHC by the CMS experiment, corresponding to an integrated luminosity of 19.7 inverse femtobarns. The B quark is assumed to be pair-produced and to decay in one of three ways: to tW, bZ, or bH. The search is carried out in final states with one, two, and more than two charged leptons, as well as in fully hadronic final states. Each of the channels in the exclusive final-state topologies is designed to be sensitive to specific combinations of the B quark-antiquark pair decays. The observed event yields are found to be consistent with the standard model expectations in all the final states studied. A statistical combination of these results is performed and upper limits are set on the cross section of the strongly produced B quark-antiquark pairs as a function of the B quark mass. Lower limits on the B quark mass between 740 and 900 GeV are set at a 95% confidence level, depending on the values of the branching fractions of the B quark to tW, bZ, and bH. Overall, these limits are the most stringent to date

Search for supersymmetry with photons in pp collisions at s\sqrt s = 8 TeV

Two searches for physics beyond the standard model in events containing photons are presented. The data sample used corresponds to an integrated luminosity of 19.7 inverse femtobarns of proton-proton collisions at $\sqrt{s}$ = 8 TeV, collected with the CMS experiment at the CERN LHC. The analyses pursue different inclusive search strategies. One analysis requires at least one photon, at least two jets, and a large amount of transverse momentum imbalance, while the other selects events with at least two photons and at least one jet, and uses the razor variables to search for signal events. The background expected from standard model processes is evaluated mainly from data. The results are interpreted in the context of general gauge-mediated supersymmetry, with the next-to-lightest supersymmetric particle either a bino- or wino-like neutralino, and within simplified model scenarios. Upper limits at 95% confidence level are obtained for cross sections as functions of the masses of the intermediate supersymmetric particles