Dynamical reentrance and geometry imposed quantization effects in Nb-AlOx-Nb Josephson junction arrays

In this paper, we report on different phenomena related to the magnetic properties of artificially prepared highly ordered (periodic) two-dimensional Josephson junction arrays (2D-JJA) of both shunted and unshunted Nb-AlOx-Nb tunnel junctions. By employing mutual-inductance measurements and using a high-sensitive bridge, we have thoroughly investigated (both experimentally and theoretically) the temperature and magnetic field dependence of complex AC susceptibility of 2D-JJA. We also demonstrate the use of the scanning SQUID microscope for imaging the local flux distribution within our unshunted arrays

Irreversibility line and low-field grain-boundary pinning in electron-doped superconducting thin films

AC magnetic susceptibilities of electron-doped Pr_{1.85}Ce_{0.15}CuO_4 (PCCO) and Sm_{1.85}Ce_{0.15}CuO_4 (SCCO) granular thin films have been measured as a function of temperature and magnetic-field strength. Depending on the level of homogeneity of our films, two different types of the irreversibility line (IL) defined as the intergrain-loss peak temperature in the imaginary part of susceptibility have been found. The obtained results are described via the critical-state model taking into account the low-field grain-boundary pinning. The extracted pinning-force densities in more granular SCCO films turn out to be four times larger than their counterparts in less granular PCCO films

Manifestation of geometric quantization effects in temperature behavior of AC magnetic response of Josephson Junction Arrays

By improving resolution of home-made mutual-inductance measurements technique, a pronounced step-like structure (with the number of steps n=4 for all AC fields) has been observed in the temperature dependence of AC susceptibility in artificially prepared two-dimensional Josephson Junction Arrays (2D-JJA) of unshunted Nb-AlO_x-Nb junctions with \beta_L(4.2K)=30. Using a single-plaquette approximation of the overdamped 2D-JJA model, we were able to successfully fit our data assuming that steps are related to the geometric properties of the plaquette. The number of steps n corresponds to the number of flux quanta that can be screened by the maximum critical current of the junctions. The steps are predicted to manifest themselves in arrays with the inductance related parameter \beta_L(T) matching a "quantization" condition \beta_L(0)=2\pi (n+1).Comment: 4 pages (jetpl style), 3 figure

Consumo e digestibilidade aparente de nutrientes em dietas para ovinos, com diferentes níveis de feno de erva-sal (Atriplex nummularia Lindl.).

Foram determinados os consumos e as digestibilidades aparente, de nutrientes em dietas para carneiros comdiferentes nÌveis do feno de erva-sal (Atriplex nummularia Lindl.). Foram utilizados vinte carneiros naturalizados,com peso vivo mÈdio inicial de 23,0 kg, submetidos a um delineamento inteiramente casualizado e alimentados emgaiolas para metabolismo. Cinco dietas contendo diferentes nÌveis de feno de erva-sal: 38,30; 52,55; 64,57; 74,85e 83,72%, associadas ? melancia forrageira (Citrulus lanatus cv. citroides) e ? raspa de mandioca (Manihot esculentaCrantz) enriquecida com 5% de urÈia, foram formuladas. O consumo do NDT, expresso em g/dia; do EE e do NDTexpressos respectivamente em %PV e g.kgPV-0,75, diminuÌram linearmente, em funÁ?o de percentuais de volumososutilizados nas dietas, n?o ocorrendo efeitos para MS, MO, PB, FDN e CHO. O nÌvel de erva-sal na dieta influencioua digestibilidade aparente da matÈria seca, a qual diminuiu de 68,94 para 49,89%, da matÈria org?nica de 68,13 a43,63%, da fibra em detergente neutro de 62,03 para 31,87% e dos carboidratos totais de 61,98 para 33,25%. Osresultados obtidos para o consumo e para a digestibilidade aparente, da maioria dos nutrientes, revelaram um bompotencial para combinaÁ?o entre o feno da erva-sal com a melancia forrageira e a raspa de mandioca, em dietaspara ovinos no semi-·rido nordestino

Nutrientes acumulados em plantas de milho para silagem, cultivadas sob diferentes espécies de cobertura na Região Central de Minas Gerais.

Fertbio 2012