Temperature Dependence of the Intergranular Critical Current Density in Uniaxially Pressed Bi(1.65)Pb(0.35)Sr(2)Ca(2)Cu(3)O(10+delta) Samples

We have studied the normal and superconducting transport properties of Bi(1.65)Pb(0.35)Sr(2)Ca(2)Cu(3)O(10+delta) (Bi-2223) ceramic samples. Four samples, from the same batch, were prepared by the solid-state reaction method and pressed uniaxially at different compacting pressures, ranging from 90 to 250 MPa before the last heat treatment. From the temperature dependence of the electrical resistivity, combined with current conduction models for cuprates, we were able to separate contributions arising from both the grain misalignment and microstructural defects. The behavior of the critical current density as a function of temperature at zero applied magnetic field, J (c) (T), was fitted to the relationship J (c) (T)ae(1-T/T (c) ) (n) , with na parts per thousand 2 in all samples. We have also investigated the behavior of the product J (c) rho (sr) , where rho (sr) is the specific resistance of the grain-boundary. The results were interpreted by considering the relation between these parameters and the grain-boundary angle, theta, with increasing the uniaxial compacting pressure. We have found that the above type of mechanical deformation improves the alignment of the grains. Consequently the samples exhibit an enhance in the intergranular properties, resulting in a decrease of the specific resistance of the grain-boundary and an increase in the critical current density.

Spin current in the Mobius cyclacene belts

We report on density functional theory studies of the electronic structure and magnetic properties of Mobius-[n]cyclacenes. The geometry of Mobius bands presents a modulation of bond lengths that is needed to accommodate the twist. This modulation takes the form of bond alternation defects analogous to those of solitons in polyacetylene. The ground state of all Mobius bands is a triplet, with a spin density distribution that follows the bond length modulation. A molecular dynamics simulation of the Mobius cyclacene at 300 K shows that the twist travels around the belt inducing a magnetic current. (C) 2009 Elsevier B. V. All rights reserved.

Study of sodium tellurite glass using the thermally stimulated depolarization current technique (TSDC)

In order to have a better understanding of the role of the structure and the defects involved in the polarization processes in an 85TeO(2)-15Na(2)O mol% glass, we used the thermally stimulated depolarization currents (TSDC technique). The TSDC of the non-irradiated sample presented a strong negative peak of current at the temperature of 340 K, preceded by a relatively weak positive peak at about 300 K. after different d.c. voltages of 1200, 1500 and 2000 V were applied. No response was obtained with 1000 V. but the peak intensity increased considerably for voltages above 1200 V. After gamma-irradiation of 25 and 50 KGy doses, a depolarization of the negative peak was observed in the sample submitted to 25 KGy, whereas for the sample irradiated with 50 KGy, six TSDC peaks appeared at regular intervals of 5 KGy, in the temperature range of 100 and 300 K. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.

Quantum current algebra for the AdS(5) x S(5) superstring

The sigma model describing the dynamics of the superstring in the AdS(5) x S(5) background can be constructed using the coset PSU(2, 2 vertical bar 4)/SO(4, 1) x SO(5). A basic set of operators in this two dimensional conformal field theory is composed by the left invariant currents. Since these currents are not (anti) holomorphic, their OPE`s is not determined by symmetry principles and its computation should be performed perturbatively. Using the pure spinor sigma model for this background, we compute the one-loop correction to these OPE`s. We also compute the OPE`s of the left invariant currents with the energy momentum tensor at tree level and one loop.

Neuropsychological Assessment of Current and Past Crack Cocaine Users

Background: Cognitive changes due to crack cocaine consumption remain unclear Methods: For clarification, 55 subjects were assigned to three groups: control group, crack cocaine current users, and ex-users. Participants were submitted to Mini-Mental State Examination (MMSE) and tasks evaluating executive functioning and verbal memory Mood state was also measured. Intergroup comparisons were carried out. Results: Control group performance on the MMSE was better than that of users and ex-users. Verbal memory performance for logical memory of users was impaired. Ex-users scored lower on DSST and Trail Making Test (Part B). Conclusion: Chronic crack cocaine use seems to disrupt general cognitive functioning (MMSE), verbal memory, and attentional resources, but findings suggest that some of these effects could be reversed by abstinence.

Potassium Current in Mature Bovine Spermatozoa

Ion channels have been assigned a pivotal importance in various sperm functions and are therefore promising targets for contraceptive development. The lack of data on channel functionality and pharmacology has hampered this goal. This is a consequence of technical problems of applying electrophysiological techniques to spermatozoa due to their small size and form. By using a laminin coating to increase adherence of spermatozoa and nystatin in the patch pipette for pore formation, we have adapted the whole-cell recording technique to study currents in mature uncapacitated bovine spermatozoa. Employing these conditions, in the head region, patched spermatozoa could be transferred into the whole-cell configuration. For the first time we document an outward rectifying current in mature bovine spermatozoa was blocked by tetraethyl ammonium (TEA) chloride. The observation of a shift in the reversal potential as a response to changes in the extracellular concentration of K+ ions allowed us to identify this current as K+ selective. This result shows that K+ channels in the head region of mature uncapacitated bovine spermatozoa can be suitably investigated using the whole-cell recording patch-clamp technique.

Leakage current, ferroelectric and structural properties in Pb(1-x)Ba(x)TiO(3) thin films prepared by chemical route

Single-phase perovskite structure Pb(1-x)Ba(x)TiO(3) thin films (x = 0.30, 0.50 and 0.70) were deposited on Pt/Ti/SiO(2)/Si substrates by the spin-coating technique. The dielectric study reveals that the thin films undergo a diffuse type ferroelectric phase transition, which shows a broad peak. An increase of the diffusivity degree with the increasing Barium contents was observed, and it was associated to a grain decrease in the studied composition range. The temperature dependence of the phonon frequencies was used to characterize the phase transition temperatures. Raman modes persist above tetragonal to cubic phase transition temperature, although all optical modes should be Raman inactive. The origin of these modes was interpreted in terms of breakdown of the local cubic symmetry by chemical disorder. The absence of a well-defined transition temperature and the presence of broad bands in some interval temperature above FE-PE phase transition temperature Suggested a diffuse type phase transition. This result corroborates the dielectric constant versus temperature data, which showed a broad ferroelectric phase transition in these thin films. The leakage Current density of the PBT thin films was studied at different temperatures and the data follow the Schottky emission model. Through this analysis the Schottky barrier height values 0.75, 0.53 and 0.34 eV were obtained to the PBT70, PBT50 and PBT30 thin films, respectively. (C) 2008 Elsevier Ltd. All rights reserved.

Current and future shopping conditions in Sälen

Going from having bought the most essential at the small shops close to home, better communications and an increasingly consumption oriented lifestyle has created a change in shopping behavior and has led to phenomenon such as shopping centres and more. These are constantly being built in Sweden: in the cities, outside the cities and more recently even in small cities -small cities as for one reason or another have access to a larger customer base which can have businesses to flourish economically. During the first decade of the 21st century, shopping centres have been established along the Swedish/Norwegian border. Since the Norwegian Krone is much stronger than the Swedish Krona Norwegians save a great deal of money on going to Sweden to shop. During the shopping trips to Sweden, it is mostly alcohol, meat, tobacco and candy that are being bought. However, other products such as clothing, technology, household appliances and more are also being purchased, all to save money on the trip. Together these cross border shoppers spent 11, 6 billion in Sweden during the year of 2010. This gives an average spending of approximately 10 900 SEK per cross border shopper on annual basis. Nordby, Töcksfors and Charlottenberg (small cities located in southwestern Sweden) are places characterized by Norwegian cross border shopping. Together, they generate billions every year and this only seems to increase. These places are relatively small in size but have prominent attributes such as proximity to the Norwegian border. Apart from these resorts and shopping centres, there are few or none similar places near the Norwegian border in the rest of Sweden. However, a place which is geographically well located and has a relatively large Norwegian and Swedish customer base is the ski resort of Sälen in west central of Sweden. Sälen is a village located near the Norwegian border, although fairly sparsely populated. The destination has annually about one million official guest nights, based on the 414 000 visitors who stay an average of about 4, 5 days.  Per visit, these tourists individually spend an average of 862 SEK on shopping at the destination. The expenditure of the mountain tourists together with the Norwegian border shoppers makes it very interesting to explore the opportunities for shopping development in terms of a shopping centre in the region of Sälen.

Dynamic whole system testing of combined renewable heating systems : the current state of the art

Objective: For the evaluation of the energetic performance of combined renewable heating systems that supply space heat and domestic hot water for single family houses, dynamic behaviour, component interactions, and control of the system play a crucial role and should be included in test methods. Methods: New dynamic whole system test methods were developed based on “hardware in the loop” concepts. Three similar approaches are described and their differences are discussed. The methods were applied for testing solar thermal systems in combination with fossil fuel boilers (heating oil and natural gas), biomass boilers, and/or heat pumps. Results: All three methods were able to show the performance of combined heating systems under transient operating conditions. The methods often detected unexpected behaviour of the tested system that cannot be detected based on steady state performance tests that are usually applied to single components. Conclusion: Further work will be needed to harmonize the different test methods in order to reach comparable results between the different laboratories. Practice implications: A harmonized approach for whole system tests may lead to new test standards and improve the accuracy of performance prediction as well as reduce the need for field tests.

Must teachers be social workers, as well …? : Reflections on the current teacher role in the Swedish upper secondary school and how it affects teacher training

The Swedish upper secondary school has made a transition from a school for the elite to be a school for everybody. When almost every youth nowadays chooses to continue studying, for some of them this is not what they want to do most of all. However, as there in practice is no choice, there come up problems and many upper secondary school teachers experience a growing frustration. We will here discuss some aspects of the following questions: -  How do upper secondary schoolteachers handle their working-conditions in a new situation? - What possible consequences do this have on teacher education?