Specifying Hardware Timing with ET-LOTOS (extended version)

It is explained how DILL (Digital Logic in LOTOS) can be used to specify and analyse hardware timing characteristics using ET-LOTOS (Enhanced Timed LOTOS), a timed extension of the ISO standard formal language LOTOS (Language of Temporal Ordering Specification). Hardware component functionality and timing characteristics are rigorously specified and then validated. As will be seen, subtle timing problems can be found by using this approach

Multiple Functionality in Nanotube Transistors

Calculations of quantum transport in a carbon nanotube transistor show that such a device offers unique functionality. It can operate as a ballistic field-effect transistor, with excellent characteristics even when scaled to 10 nm dimensions. At larger gate voltages, channel inversion leads to resonant tunneling through an electrostatically defined nanoscale quantum dot. Thus the transistor becomes a gated resonant tunelling device, with negative differential resistance at a tunable threshold. For the dimensions considered here, the device operates in the Coulomb blockade regime, even at room temperature.Comment: To appear in Phys. Rev. Let

Poole-Frenkel Effect and Phonon-Assisted Tunneling in GaAs Nanowires

We present electronic transport measurements of GaAs nanowires grown by catalyst-free metal-organic chemical vapor deposition. Despite the nanowires being doped with a relatively high concentration of substitutional impurities, we find them inordinately resistive. By measuring sufficiently high aspect-ratio nanowires individually in situ, we decouple the role of the contacts and show that this semi-insulating electrical behavior is the result of trap-mediated carrier transport. We observe Poole-Frenkel transport that crosses over to phonon-assisted tunneling at higher fields, with a tunneling time found to depend predominantly on fundamental physical constants as predicted by theory. By using in situ electron beam irradiation of individual nanowires we probe the nanowire electronic transport when free carriers are made available, thus revealing the nature of the contacts

Impact of Cognitive Impairment on Functional Outcome in Stroke

The aim of this study was to investigate the effect of the cognitive impairment on functional status in patients with subacute stroke. Fifty-two patients with subacute stroke were included in the study. Mini mental state examination (MMSE) test was used for the evaluation of cognitive status. Patients were separated into two groups according to their cognitive functions. Functional follow-up parameters were activities of daily living (ADL), global recovery and ambulation status. All patients were evaluated on admission to rehabilitation unit, at discharge and 6 months after discharge. Forty-four patients were completed the study. Mean age was 66 and 57 years; disease duration on admission was 4,8 and 3,5 months in the cognitively impaired and normal groups, respectively. Significant improvement was found in terms of functional follow-up parameters in both groups at discharge (P < .05). Functional follow-up parameters did not show statistically significant difference between the groups. But community ambulation rate was higher in cognitively normal group at the sixth month visit. As a result of this study, inpatient rehabilitation was effective both cognitively normal and impaired subacute stroke patients

Theory of enhancement of thermoelectric properties of materials with nanoinclusions

Based on the concept of band bending at metal/semiconductor interfaces as an energy filter for electrons, we present a theory for the enhancement of the thermoelectric properties of semiconductor materials with metallic nanoinclusions. We show that the Seebeck coefficient can be significantly increased due to a strongly energy-dependent electronic scattering time. By including phonon scattering, we find that the enhancement of ZT due to electron scattering is important for high doping, while at low doping it is primarily due to a decrease in the phonon thermal conductivity

Following microscopic motion in a two dimensional glass-forming binary fluid

The dynamics of a binary mixture of large and small discs are studied at temperatures approaching the glass transition using an analysis based on the topology of the Voronoi polygon surrounding each atom. At higher temperatures we find that dynamics is dominated by fluid-like motion that involves particles entering and exiting the nearest-neighbour shells of nearby particles. As the temperature is lowered, the rate of topological moves decreases and motion becomes localised to regions of mixed pentagons and heptagons. In addition we find that in the low temperature state particles may translate significant distances without undergoing changes in their nearest neig hbour shell. These results have implications for dynamical heterogeneities in glass forming liquids.Comment: 12 pages, 7 figure

A JKO splitting scheme for Kantorovich-Fisher-Rao gradient flows

In this article we set up a splitting variant of the JKO scheme in order to handle gradient flows with respect to the Kantorovich-Fisher-Rao metric, recently introduced and defined on the space of positive Radon measure with varying masses. We perform successively a time step for the quadratic Wasserstein/Monge-Kantorovich distance, and then for the Hellinger/Fisher-Rao distance. Exploiting some inf-convolution structure of the metric we show convergence of the whole process for the standard class of energy functionals under suitable compactness assumptions, and investigate in details the case of internal energies. The interest is double: On the one hand we prove existence of weak solutions for a certain class of reaction-advection-diffusion equations, and on the other hand this process is constructive and well adapted to available numerical solvers.Comment: Final version, to appear in SIAM SIM

Can Electric Field Induced Energy Gaps In Metallic Carbon Nanotubes?

The low-energy electronic structure of metallic single-walled carbon nanotube (SWNT) in an external electric field perpendicular to the tube axis is investigated. Based on tight-binding approximation, a field-induced energy gap is found in all (n, n) SWNTs, and the gap shows strong dependence on the electric field and the size of the tubes. We numerically find a universal scaling that the gap is a function of the electric field and the radius of SWNTs, and the results are testified by the second-order perturbation theory in weak field limit. Our calculation shows the field required to induce a 0.1 ${\rm eV}$ gap in metallic SWNTs can be easily reached under the current experimental conditions. It indicates a kind of possibility to apply nanotubes to electric signal-controlled nanoscale switching devices

Système électro-optique pour l'optogénétique cardiaque et l'enregistrement d'ECG

Depuis quelques temps, l'optogénétique est utilisée en recherche pour remplacer la stimulation électrique de neurones par la photo-stimulation. Des scientifiques cherchent désormais à étendre l'optogénétique à la recherche sur le coeur. Plusieurs ont prouvés la possibilité de contrôler les battements cardiaques à l'aide de lumière en laboratoire sur des rongeurs. Les expérimentations effectuées sur le coeur jusqu'à maintenant reposent sur des systèmes filaires et encombrants qui permettent la mesure de l'électrocardiogramme (ECG) à l'aide d'électrode et la photo-stimulation à l'aide d'une fibre optique. Ces systèmes augmentent le stress chez les animaux de laboratoire ce qui peut induire des erreurs dans les mesures. Ce mémoire décrit la conception d'un système répondant à cette problématique. Le système développé permet la photo-stimulation cardiaque et l'enregistrement d'ECG sans-fil à l'aide d'un implant et d'un circuit basse consommation, le tout alimenté par batterie. Étant donné la présence d'artefact de mouvement dans les ECG mesurés lors de tests préliminaires, le système comporte aussi un algorithme de filtrage des artefacts en temps réel. Finalement, le fonctionnement du prototype est démontré par différents tests in-vivo.In the past few years, optogenetics was used in research to replace electrical stimulation of neurons by photo-stimulation. Scientists now search a way to extend optogenetics to cardiac research. Many were able to control the heartbeat of rodents using light. These experiments were conducted using wired and cumbersome equiments with electrocardiogram (ECG) recording using electrodes and photo-stimulation using optical fibers. These systems increase tests subjects stress which can induce measurements errors. This master's thesis describes the design of a device answering this problem. The developed system enables cardiac photostimulation and ECG recording wirelessly with an implant and a low power electronic circuit. The device also includes a real-time algorithm to reduce motion artifacts shown in preliminary testing. Finally, the operation of the prototype is demonstrated during in-vivo experiments