Vortex state microwave resistivity in Tl-2212 thin films

We present measurements of the field induced changes in the 47 GHz complex resistivity, $\Delta \tilde \rho(H,T)$, in Tl$_{2}$Ba$_{2}$CaCu$_{2}$O$_{8+x}$ (TBCCO) thin films with $T_{c}\simeq$ 105 K, prepared on CeO$_{2}$ buffered sapphire substrates. At low fields ($\mu_{0}H<$10 mT) a very small irreversible feature is present, suggesting a little role of intergranular phenomena. Above that level $\Delta \tilde \rho(H,T)$ exhibits a superlinear dependence with the field, as opposed to the expected (at high frequencies) quasilinear behaviour. We observe a crossover between predominantly imaginary to predominantly real (dissipative) response with increasing temperature and/or field. In addition, we find the clear scaling property $\Delta \tilde \rho(H,T)=\Delta \tilde \rho[H/H^{*}(T)]$, where the scaling field $H^{*}(T)$ maps closely the melting field measured in single crystals. We discuss our microwave results in terms of loss of flux lines rigidity.Comment: 8 pages, 3 figures, proceedings of 9th HTSHFF, accepted for publication on J. Supercon

Anisotropic renormalized fluctuations in the microwave resistivity in YBCO

We discuss the excess conductivity above Tc due to renormalized order-parameter fluctuations in YBCO at microwave frequencies. We calculate the effects of the uniaxial anisotropy on the renormalized fluctuations in the Hartree approximation, extending the isotropic theory developed by Dorsey [Phys. Rev. B 43, 7575 (1991)]. Measurements of the real part of the microwave resistivity at 24 and 48 GHz and of the dc resistivity are performed on different YBCO films. The onset of the superconducting transition and the deviation from the linear temperature behavior above Tc can be fully accounted for by the extended theory. According to the theoretical calculation here presented, a departure from gaussian toward renormalized fluctuations is observed. Very consistent values of the fundamental parameters (critical temperature, coherence lenghts, penetration depth) of the superconducting state are obtained.Comment: RevTex, 8 pages with 5 figures included, to be published in Physical Review

Mixed-state microwave response in superconducting cuprates

We report measurements of the magnetic-field induced microwave complex resistivity in REBa$_{2}$Cu$_{3}$O$_{7-\delta}$ thin films, with RE = Y, Sm. Measurements are performed at 48 GHz by means of a resonant cavity in the end-wall-replacement configuration. The magnetic field dependence is investigated by applying a moderate (0.8 T) magnetic field along the c-axis. The measured vortex state complex resistivity in YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ and SmBa$_{2}$Cu$_{3}$O$_{7-\delta}$ is analyzed within the well-known models for vortex dynamics. It is shown that attributing the observed response to vortex motion alone leads to inconsistencies in the as-determined vortex parameters (such as the vortex viscosity and the pinning constant). By contrast, attributing the entire response to field-induced pair breaking leads to a nearly quantitative description of the data.Comment: 6 pages, 4 figures, to be published in J. Supercond. as proceedings of 8th HTSHFF (May 26th-29th, 2004, Begur, Spain

Scaling of the microwave magneto-impedance in Tl2_2Ba2_2CaCu2_2O8+δ_{8+\delta} thin films

We present measurements of the magnetic field-induced microwave complex resistivity changes at 47 GHz in Tl$_2$Ba$_2$CaCu$_2$O$_{8+\delta}$ (TBCCO) thin films, in the ranges 58 K$<T<T_{c}$ and 0$<\mu_{0}H<$0.8 T. The large imaginary part $\Delta\rho_{2}(H)$ points to strong elastic response, but the data are not easily reconciled with a rigid vortex model. We find that, over a wide range of temperatures, all the pairs of curves $\Delta\rho_{1}(H)$ and $\Delta\rho_{2}(H)$ can be collapsed on a pair of scaling curves $\Delta\rho_{1}[H/H^{*}(T)]$, $\Delta\rho_{2}[H/H^{*}(T)]$, with the same scaling field $H^{*}(T)$. We argue that $H^{*}(T)$ is related to the loss of vortex rigidity due to a vortex transformation.Comment: Two printed pages, Proceedings of M2S (Dresden, 2006), to appear in Physica

Gate stability of GaN-Based HEMTs with P-Type Gate

status: publishe

La enseñanza del fútbol sala en la formación de futuros profesionales de la Educación Física: la aproximación entre la teoría y la práctica

El trabajo describe una actividad realizada en la asignatura de fútbol sala del curso de formación de profesorado en Educación Física de la Universidade de Caxias do Sul (UCS) en Brasil. Los estudiantes impartieron clases de fútbol sala para niñas con edad entre los 11 y los 14 años en los centros de enseñanza de la ciudad de Caxias do Sul y su región. El objetivo de la actividad fue proporcionar a los futuros profesionales un mayor acercamiento a la realidad con la cual se deberán enfrentar en un futuro muy cercano, produciendo una formación más significativa y relevante. Al final del curso, después de los 18 partidos semanales previstos, más las clases para las chicas, los estudiantes respondieron un pequeño cuestionario adaptado en la escala de Likert sobre la importancia de la experiencia práctica para su formación. Los resultados determinaron que 7% de los alumnos del curso consideraron que la experiencia de enseñanza con las chicas presentó poca importancia para su formación como profesionales de Educación Física. Por otra parte 16% han considerado importante la actividad práctica. 37% dijeron que la experiencia fue bastante importante y 40% han respondido que la actividad fue de fundamental importancia. Ninguno contestó que la actividad fue nada importante. Así, concluimos que la utilización de esa metodología y experiencia didáctica ha permitido la reducción de las discrepancias entre la teoría y práctica existentes en las asignaturas de carácter práctico en los cursos de formación del profesorado

Usability improvements of the Thermipig model for precision pig farming

Pig livestock farming systems encounter several economic and environmental challenges, connected with meat price decrease, sanitary norms, emissions etc. To deal with these issues, methods and models to assess the performance of a pig production system have been developed. For instance, Thermipig model represents the pig fattening room and simulates performances of pigs at the batch level, taking into account interactions between the individual variability of pigs, farmer's practices, room characteristics and outdoor climate conditions. The model requires some static basic inputs fulfilled in several spreadsheets (such as rooms, pigs, and dietary characteristics) but also data files for voluminous variable inputs (such as outdoor temperature or climate control box parameters) for further modelling and outcome producing. This leads to challenges in data providing by the farmers and have to be improved. This paper deals with the implementation of the separate modules of the developed data warehouse system for usability improvements of the Thermipig model. The idea is to substitute input from the data files with online data input and automated variable processing by the model using the python script for connection to the remote data warehouse. The data warehouse system is extended with ‘Property Sets’ section dealing with all the operations that can be performed to a set of input variables. This approach demonstrates the ability of the data warehouse to act as data supplier for the remote model. As well the outcome of the model is also transferable back to the data warehouse for evaluation. This work is done within the Era-Net SuSan PigSys project - Improving pig system performance through a whole system approach

Dedicated breast computed-tomography in women with a personal history of breast cancer: A proof-of-concept study.

PURPOSE To compare the subjective image quality assessment using B-CT and digital mammography in women with personal history of breast cancer (PHBC). METHOD In this retrospective study 32 patients with PHBC were included. Each patient had undergone a B-CT examination and a previous mammogram in a time interval of less than 18 months between the two examinations. Two radiologists evaluated the two examinations independently with regard to the presence of lesions, BI-RADS classification, level of confidence for the overall exam interpretation, scar evaluation and image quality including image degradation due to clip artifacts. Level of confidence and image quality were assessed using a 5-point Likert scale. A p-value of less than 0.01 was considered statistically significant. RESULTS Thirty-seven operated and 27 non-operated breasts were included. Confidence for the overall interpretation with B-CT was equal or superior to mammography in 63 cases (98.4 %) for reader 1 and in 58 cases (90.6 %) for reader 2 (p <.001). Confidence for scar evaluation with B-CT was equal or superior to mammography in all cases for reader 1 and in 34 cases (91.9 %) for readers 2 (p <.001). One case with local recurrence in B-CT was identified by both readers and no false positive findings were reported. A moderate to high image degradation due to beam-hardening artifacts has been reported by both readers in 29.4 % of cases due to surgical clips in the B-CT volume. CONCLUSIONS B-CT in patients with PHBC provides high quality images that can be evaluated with confidence equal or superior to mammography