Experimental Study of the Inductance of Pinned Vortices in Superconducting YBa2Cu3O7-d Films

Using a two-coil mutual inductance method, we have measured the complex resistivity, rho_v(T,Be), of pinned vortices in c-axis pulsed laser deposited YBa2Cu3O7-d films with magnetic field Be applied perpendicular to the film. At low frequencies, (<100 kHz), rho_v is inductive and is inversely proportional to the Labusch parameter, the average vortex pinning force constant, kappa_exp. The observed weakening of kappa_exp with Be is consistent with a simple model based on linear pinning defects. Adding classical thermal fluctuations to the model in a simple way describes the observed linear T dependence of rho_v, below ~15 K and provides reasonable values for the effective radius (.3 nm to >.8 nm) of the defects and the depth of the pinning potential. The success of this model implies that thermal supercurrent (phase) fluctuations have their full classical amplitude down to 5 K for frequencies below the characteristic depinning frequency. To date, no sufficient theory exists to explain the data between ~15 K and the vortex glass melting temperature.Comment: 31 pages, 8 figures. Subm. to PR

Theoretical and Experimental Studies of Schottky Diodes That Use Aligned Arrays of Single Walled Carbon Nanotubes

We present theoretical and experimental studies of Schottky diodes that use aligned arrays of single walled carbon nanotubes. A simple physical model, taking into account the basic physics of current rectification, can adequately describe the single-tube and array devices. We show that for as grown array diodes, the rectification ratio, defined by the maximum-to-minimum-current-ratio, is low due to the presence of m-SWNT shunts. These tubes can be eliminated in a single voltage sweep resulting in a high rectification array device. Further analysis also shows that the channel resistance, and not the intrinsic nanotube diode properties, limits the rectification in devices with channel length up to ten micrometer.Comment: Nano Research, 2010, accepte

Effect of Thermal Phase Fluctuations on the Inductances of Josephson Junctions, Arrays of Junctions, and Superconducting Films

We calculate the factor by which thermal phase fluctuations, as distinct from phase-slip fluctuations, increase the inductance, LJ, of a resistively-shunted Josephson junction (JJ) above its mean-field value, L0. We find that quantum mechanics suppresses fluctuations when T drops below a temperature, TQ = h/kBGL0, where G is the shunt conductance. Examination of the calculated sheet inductance, LA(T)/L0(T), of arrays of JJ's reveals that 2-D interconnections halve fluctuation effects, while reducing phase-slip effects by a much larger factor. Guided by these results, we calculate the sheet inductance, LF(T)/L0(T), of 2-D films by treating each plasma oscillation mode as an overdamped JJ. In disordered s-wave superconductors, quantum suppression is important for LF(0)/LF(T) > 0.14, (or, T/TC0 < 0.94). In optimally doped YBCO and BSCCO quantum suppression is important for l2(0)/l2(T) > 0.25, where l is the penetration depth.Comment: 15 pages; 4 figures. Submitted to Physical Review B, May 199

Radio frequency analog electronics based on carbon nanotube transistors

The potential to exploit single-walled carbon nanotubes (SWNTs) in advanced electronics represents a continuing, major source of interest in these materials. However, scalable integration of SWNTs into circuits is challenging because of difficulties in controlling the geometries, spatial positions, and electronic properties of individual tubes. We have implemented solutions to some of these challenges to yield radio frequency (RF) SWNT analog electronic devices, such as narrow band amplifiers operating in the VHF frequency band with power gains as high as 14 dB. As a demonstration, we fabricated nanotube transistor radios, in which SWNT devices provide all of the key functions, including resonant antennas, fixed RF amplifiers, RF mixers, and audio amplifiers. These results represent important first steps to practical implementation of SWNTs in high-speed analog circuits. Comparison studies indicate certain performance advantages over silicon and capabilities that complement those in existing compound semiconductor technologies

INSTRUMENTO DE COMUNICAÇÃO DE ENFERMAGEM. Estudo da implantação de um modelo de comunicação escrita entre as equipes de enfermagem das unidades cirúrgicas e do centro cirúrgico

A study to introduce a nursing communication toot to make easier the continuity of nursing care of the surgical patient in the pre, per and postoperative periods. The communication tool consists in two parts: preoperative and peroperative notes form. This tool was aplied to 327 patients undergoing surgical treatment who were interned in three general surgical units and in three specialized units in a general hospital. The application of the tool was made by nursing staff of the surgical units and the operating room of the hospital. It was verified, by the analysis of results, that the frequency of the filling-in items on the preoperative form was higher than 83%, above the 70% established in this present study. The percentage of items registered on the peroperative form was above 85%, excepting pulse rate and blood pressure that showed less than 70%. The frequency of the filling-in of the items on the two forms, preoperative and peroperative, was analyzed separately for each six surgical units. The percentual variation of the filling-in was between 83 and 100% which makes possible the inference that this nursing communication tool is certainly applicable to patients undergoing general specialized surgery.Estudo da implantação de um Instrumento de Comunicação de Enfermagem que propicie a continuidade de assistência ao paciente cirúrgico, nos períodos pré, trans e pós-operatório. O Instrumento de Comunicação compreende duas partes: Ficha Pré-operatória de Enfermagem e Ficha Transoperatória de Enfermagem. O instrumento foi aplicado, pelas equipes de enfermagem das unidades cirúrgicas e do centro cirúrgico, a 327 pacientes submetidos a tratamento cirúrgico, internados em três unidades cirúrgicas gerais e três especializadas, em um hospital geral. Pela análise dos resultados apresentados, verificou-se que a freqüência de preenchimento dos itens propostos na Ficha Prê-operatória de Enfermagem obteve percentual acima de 83%, superior ao estabelecido neste estudo (70%). O percentual de preenchimento dos itens da Ficha Transoperatória de Enfermagem foi acima de 85%, exceto o dos itens pulso e pressão arterial, que se apresentou abaixo de 70%. A freqüência de preenchimento dos itens das Fichas Pré-operatória e Transoperatória de Enfermagem foi analisada separadamente, em relação a cada uma das seis unidades cirúrgicas de internação. A variação do percentual quanto à freqüência de preenchimento dos itens propostos foi de 83% a 100% nas seis unidades cirúrgicas, o que permite inferir que o Instrumento de Comunicação de Enfermagem é passível de aplicação, tanto aos pacientes submetidos a cirurgias gerais como a especializadas