Evolution of structural ({\alpha}) relaxation-time anomalies in GexSe1-x Chalcogenide glasses

We examine enthalpy relaxation across the chalcogenide glass series GexSe1-x, prepared over close-by compositions using conventional melt-quenching technique. We estimate the timescale {\tau}(Tg) characterizing enthalpic relaxation near the kinetic glass transition temperature, using the non-reversing heat-flow data obtained from MDSC (modulated differential scanning calorimetry) measurements over a wide range of compositions (2.1 {\lessthanequalto} r {\lessthanequalto} 2.8, r = 2x+2). Anomalies in the enthalpy-relaxation characteristic-times {\tau}g(r) are identified as marking rigidity-transitions encountered in successive Ge-doping of polymeric selenium chains.Comment: 10 pages, 3 figures, 30 reference

Defect tolerance in as-deposited selenium-alloyed cadmium telluride solar cells

The efficiency of cadmium telluride (CdTe) solar cells is limited primarily by voltage, which is known to depend on the carrier concentration and carrier lifetimes within the absorber layer of the cell. Here, cathodoluminescence measurements are made on an as-deposited CdSeTe/CdTe solar cell that show that selenium alloyed CdTe material luminesces much more strongly than non-alloyed CdTe. This reduction in non-radiative recombination in the CdSeTe suggests that the selenium gives it a certain defect tolerance. This has implications for carrier lifetimes and voltages in cadmium telluride solar cells

Responses of plasma transaminase activity in Cyprinus carpio var. communis to mercury toxicity

The present study reports the behavioural and enzymological responses in a freshwater teleost fish, Cyprinus carpio var. communis, exposed to acute and sublethal toxicities of mercuric chloride. During acute treatment, significant behavioural changes like erratic swimming, excess mucus secretion and increased opercular movements were noticed. During acute and sublethal treatments, both aspartate amino transferase and alanine amino transferase activity increased throughout the study period. Comparing the treatments, the changes in enzyme activities were found high in acute treatment and all the values were significant at 5% level. The above findings can be used as non-specific biomarkers of environmental pollutants

Formal Design of Asynchronous Fault Detection and Identification Components using Temporal Epistemic Logic

Autonomous critical systems, such as satellites and space rovers, must be able to detect the occurrence of faults in order to ensure correct operation. This task is carried out by Fault Detection and Identification (FDI) components, that are embedded in those systems and are in charge of detecting faults in an automated and timely manner by reading data from sensors and triggering predefined alarms. The design of effective FDI components is an extremely hard problem, also due to the lack of a complete theoretical foundation, and of precise specification and validation techniques. In this paper, we present the first formal approach to the design of FDI components for discrete event systems, both in a synchronous and asynchronous setting. We propose a logical language for the specification of FDI requirements that accounts for a wide class of practical cases, and includes novel aspects such as maximality and trace-diagnosability. The language is equipped with a clear semantics based on temporal epistemic logic, and is proved to enjoy suitable properties. We discuss how to validate the requirements and how to verify that a given FDI component satisfies them. We propose an algorithm for the synthesis of correct-by-construction FDI components, and report on the applicability of the design approach on an industrial case-study coming from aerospace.Comment: 33 pages, 20 figure

Helicopter gearbox bearing fault detection using separation techniques and envelope analysis

The main gearbox (MGB) is a crucial part of a helicopter. MGB bearings suffer intensively from stress and friction during flights hence concerns for their health condition and detecting potential defects become critical for the sake of operation safety and system reliability. In this study, bearing defects were seeded in the second epicyclic stage bearing of a commercial Class A helicopter MGB. Vibration and tachometer signals were recorded simultaneously for the purpose of fault diagnosis. The tests were carried out at different power and speed conditions for various seeded bearing defects. This paper presents a comparison of signal processing techniques employed to identify the presence of the defects masked by strong background noise generated from an operation helicopter MGB

A Component-oriented Framework for Autonomous Agents

The design of a complex system warrants a compositional methodology, i.e., composing simple components to obtain a larger system that exhibits their collective behavior in a meaningful way. We propose an automaton-based paradigm for compositional design of such systems where an action is accompanied by one or more preferences. At run-time, these preferences provide a natural fallback mechanism for the component, while at design-time they can be used to reason about the behavior of the component in an uncertain physical world. Using structures that tell us how to compose preferences and actions, we can compose formal representations of individual components or agents to obtain a representation of the composed system. We extend Linear Temporal Logic with two unary connectives that reflect the compositional structure of the actions, and show how it can be used to diagnose undesired behavior by tracing the falsification of a specification back to one or more culpable components

Magneto-optics of massive Dirac fermions in bulk Bi2Se3

We report on magneto-optical studies of Bi2Se3, a representative member of the 3D topological insulator family. Its electronic states in bulk are shown to be well described by a simple Dirac-type Hamiltonian for massive particles with only two parameters: the fundamental bandgap and the band velocity. In a magnetic field, this model implies a unique property - spin splitting equal to twice the cyclotron energy: Es = 2Ec. This explains the extensive magneto-transport studies concluding a fortuitous degeneracy of the spin and orbital split Landau levels in this material. The Es = 2Ec match differentiates the massive Dirac electrons in bulk Bi2Se3 from those in quantum electrodynamics, for which Es = Ec always holds.Comment: 5 pages, 3 figures and Supplementary materials, to be published in Physical Review Letter

Rod photoreceptors drive circadian photoentrainment across a wide range of light intensities.

In mammals, synchronization of the circadian pacemaker in the hypothalamus is achieved through direct input from the eyes conveyed by intrinsically photosensitive retinal ganglion cells (ipRGCs). Circadian photoentrainment can be maintained by rod and cone photoreceptors, but their functional contributions and their retinal circuits that impinge on ipRGCs are not well understood. Using mice that lack functional rods or in which rods are the only functional photoreceptors, we found that rods were solely responsible for photoentrainment at scotopic light intensities. Rods were also capable of driving circadian photoentrainment at photopic intensities at which they were incapable of supporting a visually guided behavior. Using mice in which cone photoreceptors were ablated, we found that rods signal through cones at high light intensities, but not at low light intensities. Thus, rods use two distinct retinal circuits to drive ipRGC function to support circadian photoentrainment across a wide range of light intensities

Ferromagnetism in Fe-substituted spinel semiconductor ZnGa2_2O4_4

Motivated by the recent experimental observation of long range ferromagnetic order at a relatively high temperature of 200K in the Fe-doped ZnGa$_2$O$_4$ semiconducting spinel, we propose a possible mechanism for the observed ferromagnetism in this system. We show, supported by band structure calculations, how a model similar to the double exchange model can be written down for this system and calculate the ground state phase diagram for the two cases where Fe is doped either at the tetrahedral position or at the octahedral position. We find that in both cases such a model can account for a stable ferromagnetic phase in a wide range of parameter space. We also argue that in the limit of high Fe$^{2+}$ concentration at the tetrahedral positions a description in terms of a two band model is essential. The two $e_g$ orbitals and the hopping between them play a crucial role in stabilizing the ferromagnetic phase in this limit. The case when Fe is doped simultaneously at both the tetrahedral and the octahedral position is also discussed.Comment: 10 pages, 9 figures, added text, J. Phys. Cond. Mat. (to appear