Manifestation of geometric resonance in current dependence of AC susceptibility for unshunted array of Nb-AlOx-Nb Josephson junctions

A pronounced resonance-like structure has been observed in the current dependence of AC susceptibility for two-dimensional array of unshunted Nb-AlOx-Nb Josephson junctions. Using a single-plaquette approximation, we were able to successfully fit our data assuming that resonance structure is related to the geometric (inductive) properties of the array.Comment: to appear in Physica C (in press

Universal R-C crossover in current-voltage characteristics for unshunted array of overdamped Nb-AlO_x-Nb Josephson junctions

We report on some unusual behavior of the measured current-voltage characteristics (CVC) in artificially prepared two-dimensional unshunted array of overdamped Nb-AlO_x-Nb Josephson junctions. The obtained nonlinear CVC are found to exhibit a pronounced (and practically temperature independent) crossover at some current I_{cr}=\left(\frac{1}{2\beta_C}-1\right)I_C from a resistance R dominated state with V_R=R\sqrt{I^2-I_C^2} below I_{cr} to a capacitance C dominated state with V_C=\sqrt{\frac{\hbar}{4eC}} \sqrt{I-I_C} above I_{cr}. The origin of the observed behavior is discussed within a single-plaquette approximation assuming the conventional RSJ model with a finite capacitance and the Ambegaokar-Baratoff relation for the critical current of the single junction

Subtransmission overhead lines mechanical monitoring for fast detection of damaging events

Different harmful events affecting high voltage overhead lines (OHLs) cause changes in the mechanical tension (tensile strength) of conductors. A mechanical monitoring of OHLs, therefore, can provide useful additional information (compared with the information provided by the widely used SCADA systems) about the power system state. The tension measurements combined with a few environmental measurements (air temperature, wind speed) can be used for an automatic (fast) detection of different events and for their approximate location along an OHL, reducing the impact of these events. Referring to 132-150 kV sub-transmission OHLs, this paper proposes some original algorithms, based on the mechanical monitoring of OHLs, for the automatic detection of the following events: conductor breaking, fall of trees on the conductors, ice/snow sleeve accretion on the conductors, strands breaking and galloping. The proposed algorithms require a limited number of sensors placed along the OHLs for measurements of the conductor tension and weather-related quantities

Unveiling the mono-rhamnolipid and di-rhamnolipid mechanisms of action upon plasma membrane models

Rhamnolipids (RLs) are biosurfactants with significant tensioactive and emulsifying properties. They are mainly composed by mono-RL and di-RL components. Although there are numerous studies concerning their molecular properties, information is scarce regarding the mechanisms by which each of the two components interacts with cell membranes. Herein, we performed phase-contrast and fluorescence microscopy experiments on plasma membrane models represented by giant-unilamellar-vesicles (GUVs) composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 2-[[(E,2S,3R)-1,3-dihydroxy-2-(octadecanoylamino) octadec-4-enyl]peroxy-hydroxyphosphoryl]oxyethyl-trimethylazanium (sphingomyelin, SM) and (3β)-cholest-5-en-3-ol (cholesterol, CHOL) (1:1:1 M ratio), which present liquid-order (Lo) liquid-disorder (Ld) phase coexistence, in the presence of either mono-RL or di-RL in 0.06–0.25 mM concentration range. A new method has been developed to determine area and volume of GUVs with asymmetrical shape and a kinetic model describing GUV-RL interaction in terms of two mechanisms, RL-insertion and pore formation, has been worked out. Results show that the insertion of mono-RL in the membrane outer leaflet is the dominant process with no pore formation and a negligible effect in modifying membrane permeability, but induces lipid mixing. Conversely, the di-RL-GUV interaction begins with the insertion mechanism and, as the time passes by, the pore formation process occurs. The analyses of di-RL show that the whole process is only relevant in the Ld phase with a higher extent to 0.25 mM than to 0.06 mM

Magnetically controlled exciton transfer in hybrid quantum dot-quantum well nanostructures

A magnetophotoluminescence study of the carrier transfer with hybrid InAs/GaAs quantum dot(QD)-InGaAs quantum well (QW) structures is carried out where we observe an unsual dependence of the photoluminescence (PL) on the GaAs barrier thickness at strong magnetic field and excitation density. For the case of a thin barrier the QW PL intensity is observed to increase at the expense of a decrease in the QD PL intensity. This is attributed to changes in the interplane carrier dynamics in the QW and the wetting layer (WL) resulting from increasing the magnetic field along with changes in the coupling between QD excited states and exciton states in the QW and the WL

Aharonov-Bohm interference in quantum ring exciton: effects of built-in electric fields

We report a comprehensive discussion of quantum interference effects due to the finite structure of excitons in quantum rings and their first experimental corroboration observed in the optical recombinations. Anomalous features that appear in the experiments are analyzed according to theoretical models that describe the modulation of the interference pattern by temperature and built-in electric fields.Comment: 6 pages, 7 figure

Morphological, electrical and optical properties of Si-doped GaAs grown by MBE on GaAs non-(100)-oriented substrates

The incorporation and amphoteric behavior of Si has been investigated in molecular beam epitaxy (MBE) GaAs samples grown on (311)A, (211)A and (111)A substrates at different growth conditions. Hall effect measurements have revealed that the doping changes from p- to n-type when the V4/III flux ratio is increased and the growth temperature is decreased. The transition flux ratio is lower for the (211)A than for the (311)A surfaces. Photoluminescence measurements have shown that, when the V4/III flux ratio is increased or the growth temperature is decreased, arsenic vacancy defects are changed into pairs of Ga vacancy and Ga antisite defects. These results are explained by considering the kinetics of the MBE growth process and the orientation dependence of the surface bonding

Electrical control of glass-like dynamics in vanadium dioxide for data storage and processing

Metal–oxide–semiconductor junctions are the building blocks of modern electronics and can provide a variety of functionalities, from memory to computing. The technology, however, faces constraints in terms of further miniaturization and compatibility with post–von Neumann computing architectures. Manipulation of structural—rather than electronic—states could provide a path to ultrascaled low-power functional devices, but the electrical control of such states is challenging. Here we report electronically accessible long-lived structural states in vanadium dioxide that can provide a scheme for data storage and processing. The states can be arbitrarily manipulated on short timescales and tracked beyond 10,000 s after excitation, exhibiting features similar to glasses. In two-terminal devices with channel lengths down to 50 nm, sub-nanosecond electrical excitation can occur with an energy consumption as small as 100 fJ. These glass-like functional devices could outperform conventional metal–oxide–semiconductor electronics in terms of speed, energy consumption and miniaturization, as well as provide a route to neuromorphic computation and multilevel memories

Contributions des tradipraticiens de santé au traitement antirétroviral : Étude de cas à Nampula, Mozambique

Contexte: L’épidémie du virus de l’immunodéficience humaine au Mozambique est un problème grave de santé publique et le Ministère de la Santé a étendu le traitement antirétroviral à tous les districts du pays. Cependant, on constate un nombre élevé d’abandon du traitement encore insuffisamment évalué. L’Organisation Mondiale de la Santé recommande que les tradipraticiens de santé collaborent avec les systèmes nationaux de santé dans les pays en développement, pour combattre cette épidémie, mais il existe peu d’actions dans ce domaine à ce jour. Objectif: Évaluer la connaissance des tradipraticiens sur l’infection et leur disponibilité à coopérer avec les services de santé dans la Province de Nampula au Mozambique, pour améliorer les résultats du traitement antirétroviral. Lieux: Cinq centres de santé des districts de la Province de Nampula, au Nord du Mozambique, avec des taux élevés d’incidence du virus d’immunodéficience humaine et d’abandon du traitement. Méthodes: Une étude mixte transversale, utilisant des interviews ciblés et des discussions de groupes focaux. Les données quantitatives étaient traitées par fréquence et les données qualitatives par analyse de discours et ethnographie locale. Résultats: Nous avons interviewé 79 tradipraticiens de santé. La perte de poids était souvent considérée comme le signal principal de suspicion d’infection par le virus d’immunodéficience humaine et certains tradipraticiens ne pas les signes de la maladie ; la majorité pensait que les antirétroviraux améliorent la qualité de vie des patients, ne prétendait pas traiter l’infection, savait qu’elle n’est pas curable, avait une idée sur le concept de bonne adhésion au traitement et référait les cas compliqués au centre de santé. En ce qui concerne l’alimentation, la moitié considérait exclusivement les céréales comme l’aliment principal ; les fruits étaient importants pour un quart ; l’eau potable est ignorée. La majorité était prête à collaborer avec le système de santé et avait des propositions de coopération pratique : la qualification et la reconnaissance individuelle et la formation intégrée avec les professionnels de santé. Conclusion: Les tradipraticiens connaissaient l’infection par le virus d’immunodéficience humaine et les facteurs associés, mais il y a des lacunes. Ils ont signalé qu’ils utilisaient principalement les plantes médicinales, ce qui peut contribuer au traitement des infections opportunistes et la majorité référait déjà des patients au centre de santé ; mais la collaboration nécessite une procédure éducative et une articulation structurée. Les lacunes de connaissance empêchent une coopération efficace dans le combat contre l’épidémie. Le groupe est disponible pour coopérer avec le système de santé pour améliorer les résultats du traitement antirétroviral, mais pour ça il est nécessaire d’informer et former les tradipraticiens dans un processus intégré de collaboration avec les professionnels de santé conventionnels