High-temperature superconducting fault current microlimiters

High-temperature superconducting microbridges implemented with YBa(2)Cu(3)O(7-delta) thin-films are shown to be possible fault current limiters for microelectronic devices with some elements working at temperatures below the superconducting critical temperature and, simultaneously, under very low power conditions (below 1W). This is the case in the important applications of superconductors as SQUID based electronics, and technologies for communication or infrared detectors. In this paper it is shown that the good thermal behavior of these microlimiters allows working in a regime where even relatively small faults induce their transition to highly dissipative states, dramatically increasing their limitation efficiency. The conditions for optimal refrigeration and operation of these microlimiters are also proposed.Comment: 10 pages, 3 figures. LaTeX and EPS file

The structure of intercalated water in superconducting Na0.35_{0.35}CoO2⋅_{2}\cdot1.37D2_{2}O: Implications for the superconducting phase diagram

We have used electron and neutron powder diffraction to elucidate the structural properties of superconducting \NaD. Our measurements show that our superconducting sample exhbits a number of supercells ranging from ${1/3}a^{*}$ to ${1/15}a^{*}$, but the most predominant one, observed also in the neutron data, is a double hexagonal cell with dimensions \dhx. Rietveld analysis reveals that \deut\space is inserted between CoO$_{2}$ sheets as to form a layered network of NaO$_{6}$ triangular prisms. Our model removes the need to invoke a 5K superconducting point compound and suggests that a solid solution of Na is possible within a constant amount of water $y$.Comment: 4 pages, 3 figure

Revised superconducting phase diagram of hole doped Nax_{x}(H3_{3}O)z_{z}CoO2⋅y_{2}\cdot yH2_{2}O

We have studied the superconducting phase diagram of \NaH\space as a function of electronic doping, characterizing our samples both in terms of Na content $x$ and the Co valence state. Our findings are consistent with a recent report that intercalation of \oxp\space ions into Na$_{x}$CoO$_{2}$, together with water, act as an additional dopant indicating that Na sub-stochiometry alone does not control the electronic doping of these materials. We find a superconducting phase diagram where optimal \Tc\space is achieved through a Co valence range of 3.24 - 3.35, while \Tc\space decreases for materials with a higher Co valence. The critical role of dimensionality in achieving superconductivity is highlighted by similarly doped non-superconducting anhydrous samples, differing from the superconducting hydrate only in inter-layer spacing. The increase of the interlayer separation between CoO$_{2}$ sheets as Co valence is varied into the optimal \Tc\space region is further evidence for this criticality.Comment: Paper updated on 29/10/2004, 4 pages, 4 figures. Physical Review Letters (in press

The stall-design paradox: Neck rails increase lameness but improve udder and stall hygiene

Housing conditions for dairy cows are thought to af-fect lameness, but almost no experimental work has addressed this link. The aim was to assess the effect of one feature of free-stall design, the position of the neck rail, testing the prediction that cows will be more likely to become lame if using pens with the neck rail positioned such that it prevents standing fully inside the stall. Cows (n = 32) were housed in 8 pens. Treat-ments were tested using a crossover design; treatments were allocated alternately to pens at the beginning of the experiment and switched halfway through the 10-wk experiment. Cows spent 27 ± 3 min/d standing with all 4 feet in stalls with less restrictive neck rails. In contrast, cows averaged just 1 ± 3 min/d when the neck rail was positioned restrictively. Cows spent less time standing with only the front 2 feet in the stall with less restrictive neck rails (33 vs. 49 ± 6 min/d). Gait scores improved when cows were kept in the less restrictive stalls and worsened when cows were kept in pens with the restrictive neck rail (median score 2.5 vs. 3.5 after 5 wk on treatment). Of 13 new cases of lame-ness, 11 occurred in pens with the restrictive neck-rail position. Similarly, of the 16 new cases of sole lesions, 15 occurred during the period when cows were housed in pens with a restrictive neck rail. Stalls with the neck rail positioned less restrictively had higher contamina-tion scores than stalls with the restrictive neck rails (3.7 vs. 0.4 ± 0.2), and cows using those stalls had dirtier udders and longer teat-cleaning times (8.3 vs. 7.0 ± 0.2 min for 12 cows). This study provides the first experimental evidence that aspects of stall design can reduce the risk of lameness and hoof disease. The results illustrated that changes in design that resulted in improvements in cow comfort and hoof health came at the expense of cow and stall cleanliness

The in-plane paraconductivity in La_{2-x}Sr_xCuO_4 thin film superconductors at high reduced-temperatures: Independence of the normal-state pseudogap

The in-plane resistivity has been measured in $La_{2-x}Sr_xCuO_4$ (LSxCO) superconducting thin films of underdoped ($x=0.10,0.12$), optimally-doped ($x=0.15$) and overdoped ($x=0.20,0.25$) compositions. These films were grown on (100)SrTiO$_3$ substrates, and have about 150 nm thickness. The in-plane conductivity induced by superconducting fluctuations above the superconducting transition (the so-called in-plane paraconductivity, $\Delta\sigma_{ab}$) was extracted from these data in the reduced-temperature range 10^{-2}\lsim\epsilon\equiv\ln(T/\Tc)\lsim1. Such a $\Delta\sigma_{ab}(\epsilon)$ was then analyzed in terms of the mean-field--like Gaussian-Ginzburg-Landau (GGL) approach extended to the high-$\epsilon$ region by means of the introduction of a total-energy cutoff, which takes into account both the kinetic energy and the quantum localization energy of each fluctuating mode. Our results strongly suggest that at all temperatures above Tc, including the high reduced-temperature region, the doping mainly affects in LSxCO thin films the normal-state properties and that its influence on the superconducting fluctuations is relatively moderate: Even in the high-$\epsilon$ region, the in-plane paraconductivity is found to be independent of the opening of a pseudogap in the normal state of the underdoped films.Comment: 35 pages including 10 figures and 1 tabl

Defect Localization By an Extended Laser Source on a Hemisphere

The primary goal of this study is to localize a defect (cavity) in a curved geometry. Curved topologies exhibit multiple resonances and the presence of hotspots for acoustic waves. Launching acoustic waves along a specific direction e.g. by means of an extended laser source reduces the complexity of the scattering problem. We performed experiments to demonstrate the use of a laser line source and verified the experimental results in FEM simulations. In both cases, we could locate and determine the size of a pit in a steel hemisphere which allowed us to visualize the defect on a 3D model of the sample. Such an approach could benefit patients by enabling contactless inspection of acetabular cups. © 2021, The Author(s).Open access funded by University of Helsinki Library

Bioprospecção de extratos vegetais ativos sobre larvas do carrapato Rhipicephalus (Boophilus) microplus

Introdução: O carrapato bovino tem grande importância sanitária no Brasil, mas encontra-se muito resistente aos acaricidas sintéticos disponíveis [1]. Dessa forma, esse estudo teve por objetivo investigar a ação de extratos vegetais sobre larvas de R. microplus. Métodos: Envelopes de papel de filtro contendo ± 100 larvas e impregnados com os extratos foram incubados por 24h em B.O.D. ± 28°C e UR >80% [2]. Foram avaliados em 3 repetições: extrato metanólico da raiz de Curcuma longa (20 mg), extrato diclorometano das folhas de Hortia brasiliana (10 mg), extrato metanólico do tronco de Hortia superba (10 mg), extrato etanólico do caule (20 mg) e partição hexânica, dicloro, acetato de etila e etanólica das folhas de Euxylophora paraensis (15, 15, 17 e 20 mg), extrato hidrometanólico das cascas do fruto (253 mg) e etanólico de folhas e galhos de Trichilia elegans (20 mg); extrato hexânico da semente de Annona muricata, extrato etanólico da raiz de Zingiber oficinalle e de galhos de Uncaria tomentosa (20 mg). Testaram-se também os óleos brutos de Carapa guianensis e de Copaifera reticulata a 3%, 7,5% e 15%. Os extratos tiveram seus solventes evaporados e depois testados a 100%, 50% e 25% da massa inicial, adicionando-se água, ou etanol a 30% e/ou tween 80 a 2%. Os controles foram preparados com os mesmos solventes. Resultados e Discussão/ Conclusão: O extrato metanólico da raiz de C. longa causou lentidão no movimento das larvas nas concentrações de 100 e 50%. C. reticulata causou mortalidade de 4%, 18,6% e 28,3% nas concentrações de 3%, 7,5% e 15%, respectivamente. Portanto, as espécies vegetais não foram eficazes, ou economicamente viáveis no caso de C. reticulata, nas concentrações avaliadas. 1.Grisi, L. et al. (2002) A Hora Vet. 125: 8-10. 2.Fao Plant Protection Bulletin (1971) FAO method n.º7 19: 15-18