Features in Evanescent Aharonov-Bohm interferometry

In this work we analyze an Aharonov-Bohm interferometer in the tunneling regime. In this regime, current magnification effect which arises in presence of transport currents is absent. A slight modification in the form of a quantum well incorporated in one of the arms leads to revival of current magnification. Systematics in magneto-conductance oscillations are observed in this evanescent wave geometry. In this framework we also see absence of Fano lineshapes in transmission resonances but once again one can recover these if the direct path supports propagating modes.Comment: 7 pages, 7 figures. Minor changes made. Accepted for publication in Phys. Rev.

Current magnification effect in mesoscopic systems at equilibrium

We study the current magnification effect and associated circulating currents in mesoscopic systems at equilibrium. Earlier studies have revealed that in the presence of transport current(non-equilibrium situation), circulating currents can flow in a ring even in the absence of magnetic field. This was attributed to current magnification which is quantum mechanical in origin. We have shown that the same effect can be obtained in equilibrium systems, however, in the presence of magnetic flux. For this we have considered an one-dimensional open mesoscopic ring connected to a bubble, and the system is in contact with a single reservoir. We have considered a special case where bubble does not enclose magnetic flux, yet circulating currents can flow in it due to current magnification.Comment: 4 pages, 4 figures. Minor corrections made and journal reference adde

Equilibrium currents in quantum double ring system: A non-trivial role of system-reservoir coupling

Amperes law states that the magnetic moment of a ring is given by current times the area enclosed. Also from equilibrium statistical mechanics it is known that magnetic moment is the derivative of free energy with respect to magnetic field. In this work we analyze a quantum double ring system interacting with a reservoir. A simple S-Matrix model is used for system-reservoir coupling. We see complete agreement between the aforesaid two definitions when coupling between system and reservoir is weak, increasing the strength of coupling parameter however leads to disagreement between the two. Thereby signifying the important role played by the coupling parameter in mesoscopic systems.Comment: 6 pages, 3 figure

The local dayside reconnection rate for oblique interplanetary magnetic fields

We present an analysis of local properties of magnetic reconnection at the dayside magnetopause for various interplanetary magnetic field (IMF) orientations in global magnetospheric simulations. This has heretofore not been practical because it is difficult to locate where reconnection occurs for oblique IMF, but new techniques make this possible. The approach is to identify magnetic separators, the curves separating four regions of differing magnetic topology, which map the reconnection X-line. The electric field parallel to the X-line is the local reconnection rate. We compare results to a simple model of local two-dimensional asymmetric reconnection. To do so, we find the plasma parameters that locally drive reconnection in the magnetosheath and magnetosphere in planes perpendicular to the X-line at a large number of points along the X-line. The global magnetohydrodynamic simulations are from the three-dimensional Block-Adaptive, Tree Solarwind Roe-type Upwind Scheme (BATS-R-US) code with a uniform resistivity, although the techniques described here are extensible to any global magnetospheric simulation model. We find that the predicted local reconnection rates scale well with the measured values for all simulations, being nearly exact for due southward IMF. However, the absolute predictions differ by an undetermined constant of proportionality, whose magnitude increases as the IMF clock angle changes from southward to northward. We also show similar scaling agreement in a simulation with oblique southward IMF and a dipole tilt. The present results will be an important component of a full understanding of the local and global properties of dayside reconnection.Comment: 12 pages, 7 figures, 1 table, Submitted to Journal Geophysical Research Space Physics February 12, 2016; Revised April 28, 201

Study of quantum current enhancement, eigenenergy spectra and magnetic moments in a multiply connected system at equilibrium

A multiply connected system in both its open and closed form variations but in equilibrium is studied using quantum waveguide theory. The system exhibits remarkable features, in its open form variation we see current enhancement, hitherto seen only in non-equilibrium systems in absence of magnetic flux. In its closed form analog parity effects are broken. Further we analyse the global and local current densities of our system and also show that the orbital magnetic response of the system calculated from the current densities (and inherently linked to the topological configuration) is qualitatively not same as that calculated from the eigenenergy spectra.Comment: 10 pages, 15 figures, 3 table

Proteostasis and ageing: insights from long-lived mutant mice

The global increase in life expectancy is creating significant medical, social and economic challenges to current and future generations. Consequently, there is a need to identify the fundamental mechanisms underlying the ageing process. This knowledge should help develop realistic interventions capable of combatting age-related disease, and thus improving late-life health and vitality. While several mechanisms have been proposed as conserved lifespan determinants, the loss of proteostasis- where proteostasis is defined here as the maintenance of the proteome- appears highly relevant to both ageing and disease. Several studies have shown that multiple proteostatic mechanisms, including the endoplasmic reticulum (ER)-induced unfolded protein response (UPR), the ubiquitin-proteasome system (UPS) and autophagy, all appear indispensable for longevity in many long-lived invertebrate mutants. Similarly, interspecific comparisons suggest that proteostasis may be an important lifespan determinant in vertebrates. Over the last 20 years a number of long-lived mouse mutants have been described, many of which carry single-gene mutations within the growth-hormone, insulin/IGF-1 or mTOR signalling pathways. However, we still do not know how these mutations act mechanistically to increase lifespan and healthspan, and accordingly whether mechanistic commonality occurs between different mutants. Recent evidence supports the premise that the successful maintenance of the proteome during ageing may be linked to the increased lifespan and healthspan of long-lived mouse mutants

Friction and Inertia: Business Change, Corporate Real Estate Portfolios and the U.K. Office Market

It has been asserted that business reorganization and new working practices are transforming the nature of demand for business space. Downsizing, delayering, business process re-engineering and associated initiatives alter the amount, type and location of space required by firms. The literature has neglected the impact of real estate market structures on the ability of organizations to implement these new organizational forms or contemporary working practices successfully. Drawing from research in the United Kingdom, the article demonstrates that, while new working practices are widespread, their impact on the corporate real estate portfolio is less dramatic than often supposed. In part, this is attributed to inflexibility in market structures, which constrains the supply of appropriate space.

Instabilities in Zakharov Equations for Laser Propagation in a Plasma

F.Linares, G.Ponce, J-C.Saut have proved that a non-fully dispersive Zakharov system arising in the study of Laser-plasma interaction, is locally well posed in the whole space, for fields vanishing at infinity. Here we show that in the periodic case, seen as a model for fields non-vanishing at infinity, the system develops strong instabilities of Hadamard's type, implying that the Cauchy problem is strongly ill-posed

Role of quantum entanglement due to a magnetic impurity on current magnification effect in mesoscopic open rings

We study the current magnification effect in presence of exchange scattering of electron from a magnetic impurity placed in one arm of an open mesoscopic ring. The exchange interaction causes entanglement of electron spin and impurity spin. Earlier studies have shown that such an entanglement causes reduction or loss of interference in the Aharonov-Bohm oscillations leading to decoherence. We find however, that this entanglement, in contradiction to the naive expectation of a reduction of current magnification, leads to enhancement as well as suppression of the effect. We also observe additional novel features like new resonances and current reversals.Comment: 5 pages RevTex, 5 figures include

Instability of fixed, low-thrust drag compensation

FORCED drag compensation using continuous low-thrustpropulsion has been considered for satellites in low Earth orbit. This simple, but nonoptimal, scheme merely requires that the thrust vector is directed opposite to the drag vector and that the magnitude of the two are equal. In principle, the drag force acting on the spacecraft could be determined onboard using accurate accelerometers. However, for small, low-cost spacecraft such sensors may beunavailable. An alternative strategy would be to Ž x the thrust magnitude equal to the expected air drag that would be experienced by the spacecraft. The thrust levelwould be periodically updated based on ground-based orbit determination. In this Engineering Note, it is shown that such a forced circular orbit with a Ž fixed thrust levelis exponentially unstable for all physically reasonable atmosphere models