Critical current of a superconductor measured via injection of spin polarized carriers

In this paper we report a direct evidence of the suppression of critical current due to pair-breaking in a superconducting micro-bridge when the measurement is carried out by injecting spin polarised carriers instead of normal electrons. A thin layer of La0.7Ca0.3MnO3 was used as the source of spin polarised carriers. The micro-bridge was formed on the DyBa2Cu3O7-d thin film by photo-lithographic techniques. The design of our spin-injection device allowed us to inject spin-polarised carriers from the La0.7Ca0.3MnO3 layer directly to the DyBa2Cu3O7- d micro-bridge (without any insulating buffer layer) making it possible to measure the critical current when polarised electrons alone are injected into the superconductor. Our results confirm the role of polarised carriers in breaking the Cooper pairs in the superconductor.Comment: 8 pages, 4 figure

A study of global monopole in Lyra geometry

A class of exact static solution around a global monopole resulting from the breaking of a global S0(3) symmetry is obtained in the context of Lyra geometry. Our solution is shown to possess an interesting feature like wormholes space-time. It has been shown that the global monopole exerts no gravitational force on surrounding non-relativistic matter.Comment: 6 pages, Published in Mod.Phys.Lett.A19:2785-2790,200

Dependence of the 0.5(2e2/h) conductance plateau on the aspect ratio of InAs quantum point contacts with in-plane side gates

The observation of a 0.5 conductance plateau in asymmetrically biased quantum point contacts with in-plane side gates has been attributed to the onset of spin-polarized current through these structures. For InAs quantum point contacts with the same width but longer channel length, there is roughly a fourfold increase in the range of common sweep voltage applied to the side gates over which the 0.5 conductance plateau is observed when the QPC aspect ratio (ratio of length over width of the narrow portion of the structure) is increased by a factor 3. Non-equilibrium Green s function simulations indicate that the increase in the size of the 0.5 conductance plateau is due to an increased importance, over a larger range of common sweep voltage, of the effects of electron-electron interactions in QPC devices with larger aspect ratio. The use of asymmetrically biased QPCs with in-plane side gates and large aspect ratio could therefore pave the way to build robust spin injectors and detectors for the successful implementation of spin field effect transistorsComment: 30 pages, 9 figure

Conservation and sustainable use of tropical fruit species diversity: Bioversity's efforts in Asia, the Pacific and Oceania

Asia, the Pacific and Oceania region is very rich in genetic diversity of tropical fruits. Although, fruits have always been important agricultural species, it is only in recent years that there is an increasing awareness of the potential of native tropical fruit species as good sources of dietary vitamins, minerals and energy. They also play a very signifi cant role for the wellbeing of the people through enhancing household income, employment generation particularly for women, and environmental protection. At the same time, their genetic diversity and even the species diversity is threatened due to various human interventions and concerted efforts are required to take corrective measures. Bioversity International, in collaboration with national partners, implemented in recent past several programmes for effective conservation and sustainable use of genetic resources of tropical fruits in the region and is continuing to do so. This paper describes the results of studies on various aspects of tropical fruit genetic diversity and species diversity as well as their sustainable use in major fruit growing countries in Asia, the Pacifi c and Oceania in the last decade and half. The studies included exploration and collecting, characterization and evaluation, identifi cation of promising/elite lines, documentation, conservation, training and capacity building, socio-economic analysis, information dissemination, collaboration and networking, impacts and sustainability of efforts. The paper also touches on the current efforts and future thrusts for tropical fruit species genetic resources conservation, management and sustainable use

Изменение диэлектрических потерь резин на основе этилен-пропиленовых каучуков со временем ионизационного старения

В работе изучалось влияние вулканизующей группы и наполнителя на диэлектрические потери резин на основе этилен-пропиленовых каучуков и изменение диэлектрических потерь со временем ионизационного старения. Установлено, что диэлектрические потери и изменения их со временем ионизационного старения в значительной степени зависят от типа вулканизующей группы и наполнителя

Poluklasični gravitacijski efekti blizu kozmičke strune u Lyrinoj geometriji

In recent past, W. A. Hiscock [Phys. Lett. B 188 (1987) 317] studied the semi-classical gravitational effects near cosmic strings. He obtained the vacuum expectation value of the stress-energy tensor of an arbitrary collection of conformal massless free-quantum fields (scalar, spinor and vectors) in the presence of a static, cylindrically symmetric cosmic string. With this stress-energy tensor, we study the semi-classical gravitational effects of a cosmic string in the context of Lyra geometry.Nedavno je W. A. Hiscock [Phys. Lett. B 188 (1987) 317] proučavao poluklasične gravitacijske efekte u blizini kozmičkih struna. Izveo je vakuumsku očekivanu vrijednost za tenzor naprezanja-energije za proizvoljan skup konformnih, bezmasenih i slobodnih kvantnih polja (skalara, spinora i vektora) u prisustvu statičke cilindrično-simetrične kozmičke strune. S tim tenzorom proučavamo poluklasične gravitacijske efekte kozmičke strune u okviru Lyrine geometrije

Poluklasični gravitacijski efekti blizu kozmičke strune u Lyrinoj geometriji

In recent past, W. A. Hiscock [Phys. Lett. B 188 (1987) 317] studied the semi-classical gravitational effects near cosmic strings. He obtained the vacuum expectation value of the stress-energy tensor of an arbitrary collection of conformal massless free-quantum fields (scalar, spinor and vectors) in the presence of a static, cylindrically symmetric cosmic string. With this stress-energy tensor, we study the semi-classical gravitational effects of a cosmic string in the context of Lyra geometry.Nedavno je W. A. Hiscock [Phys. Lett. B 188 (1987) 317] proučavao poluklasične gravitacijske efekte u blizini kozmičkih struna. Izveo je vakuumsku očekivanu vrijednost za tenzor naprezanja-energije za proizvoljan skup konformnih, bezmasenih i slobodnih kvantnih polja (skalara, spinora i vektora) u prisustvu statičke cilindrično-simetrične kozmičke strune. S tim tenzorom proučavamo poluklasične gravitacijske efekte kozmičke strune u okviru Lyrine geometrije

Proučavanje globalnih struna u Lyrinoj geometriji

An exact solution for the space-time outside the core of a U(1) static global string in Lyra geometry is presented. Our global string is nonsingular at a finite distance from the string core. The gravitational field of the global string is shown to be attractive in nature.Dajemo egzaktno rješenje za prostor-vrijeme izvan sredice mirne globalne U(1) strune u Lyrinoj geometriji. Nalazi se da globalna struna nije singularna na konačnoj daljini od sredice strune. Pokazuje se da je gravitacijsko polje globalne strune privlačno

Proučavanje globalnih struna u Lyrinoj geometriji

An exact solution for the space-time outside the core of a U(1) static global string in Lyra geometry is presented. Our global string is nonsingular at a finite distance from the string core. The gravitational field of the global string is shown to be attractive in nature.Dajemo egzaktno rješenje za prostor-vrijeme izvan sredice mirne globalne U(1) strune u Lyrinoj geometriji. Nalazi se da globalna struna nije singularna na konačnoj daljini od sredice strune. Pokazuje se da je gravitacijsko polje globalne strune privlačno