Surface-scribed transparency-based microplates

Transparency sheets, which are normally associated with use on overhead projectors, offer lowered costs and high amenability for optical diagnostics in microplate instrumentation. An alternative microplate design in which circles are scribed on the surface of the transparency to create the boundaries to hold the drop in place is investigated here. The 3D profile of the scribed regions obtained optically showed strong likelihood of affecting three-phase contact line interactions. During dispensation, the contact angle (?95°) was larger than the drop advancing state (?80°) due to a period of nonadhesion, where the contact angle later reduced to the drop advancing state followed by increase in the liquid area coverage on the substrate. It was established that 50 ?L was needed to fill the well fully, and the maximum volume retainable before breaching was 190 ?L. While the tilt angle needed for displacement reduced significantly from 50 to 95 ?L, this was markedly better than nonscribed surfaces, where tilt angles always had to be kept to within 30°. It was found that there was greater ability to fill the well with smaller volumes with dispensation at the center. This was attributed to the growing contact line not meeting the scribed edge in parallel if liquid was dispensed closer to it, wherein pinning reduction in some directions permitted liquid travel along the scribed edge to undergo contact angle hysteresis. Fluorescence measurements conducted showed no performance compromise when using scribed transparency microplates over standard microplates.

Effect of δ-ferrite co-existence on hot deformation and recrystallization of austenite

This work evaluates the effect of co-existence of a large volume fraction of δ-ferrite on the hot deformation and dynamic recrystallization (DRX) of austenite using comparative hot torsion tests on AISI 304 austenitic and 2205 duplex stainless steels. The comparison was performed under similar deformation conditions (i.e. temperature and strain rate) and also under similar Zener-Hollomon, Z, values. The torsion data were combined with electron backscatter diffraction (EBSD) analysis to study the microstructure development. The results imply a considerable difference between DRX mechanisms, austenite grain sizes and also DRX kinetics of two steels. Whereas austenitic stainless steel shows the start of DRX at very low strains and then development of that microstructure based on the necklace structure, the DRX phenomena in the austenite phase of duplex structure does not proceed to a very high fraction. Also, the DRX kinetics in the austenitic steel are much higher than the austenite phase of the duplex steel. The results suggest that at a similar deformation condition the DRX grain size of austenitic steel is almost three times larger than the DRX grains of austenite phase in duplex steel. Similarly, the ratio of DRX grain size in the austenitic to the duplex structure at the same Z values is about 1.5.

Depinning do fluxo de Josephson em compósitos YBa 2 Cu 3 O 7-delta/Ag

Apresenta-se neste trabalho um estudo experimental da dinâmica do fluxo magnético intergranular no cuprato supercondutor Y Ba2Cu3O7 e nos compósitos Y Ba2CU3O7 fi/Ag para várias concentrações de prata. Verificou-se que sob certas condições é possível separar os efeitos da dinâmica do fluxo de Josephson daqueles resultantes da dinâmica de Abrikosov. Através da técnica de medidas de magnetização DC foram obtidas as linhas de depinning inicial e de irreversibilidade magnética em campo magnético aplicado até 120 Oe. O revestimento dos grãos supercondutores aparentemente não afeta a energia de acoplamento dos elos fracos entre os grãos e o potencial de pinning até 16.1 % em peso de prata. A vantagem da mistura da prata é que esta melhora as propriedades mecânicas dos óxidos supercondutores além de melhorar as correntes críticas do sistema. Observamos que o depinning do fluxo de Josephson começa numa temperatura bem definida, dependendo do campo magnético aplicado e gradualmente aumenta com a temperatura até ou muito próximo do limite de irreversibilidade, acima do qual todo o fluxo intergranular (e intragranular) está livre. As linhas de irreversibilidade das nossas amostras podem ser entendidas dentro do modelo do Vidro supercondutor.

Programa computacional para análise dinâmica de estruturas incluindo amortecimento viscoelástico

Neste trabalho apresenta-se a implementação da matriz de amortecimento viscoelástica para um programa computacional de análise de cascas laminadas de materiais compósitos. A formulação apresentada permite realizar análises dinâmicas de estruturas laminadas com a consideração do efeito do amortecimento para dois modelos diferentes: Kelvin e Zener. A matriz de amortecimento foi implementada de duas formas: proporcional à massa ou proporcional à rigidez. A equação do movimento do sistema dinâmico foi resolvida utilizando-se o método de Newmark para integração direta. Para o modelo Zener foi desenvolvida uma análise para um elemento com 1 grau de liberdade. Apresentam-se exemplos de aplicações da formulação para modelos viscosos, implementadas no programa de elementos finitos, submetidos a diferentes tipos de carregamentos, como carga distribuída e cargas de impacto com diferentes tipos de excitações. Comparações entre o comportamento dos modelos Kelvin e Zener foram realizadas para validar os resultados obtidos.

Ultra-som pulsado de baixa intensidade em fraturas diafisárias: aplicação clínica em cães

Os efeitos da estimulação ultra-sônica sobre a consolidação óssea têm sido demonstrados por trabalhos experimentais e clínicos. Este estudo teve por objetivo investigar a aplicação clínica do ultra-som pulsado de baixa intensidade como tratamento adjuvante de fraturas diafisárias em cães. Foram utilizados 16 cães de raças variadas, com faixa etária entre sete meses e seis anos, peso corpóreo entre 2,5 e 43kg, portadores de fraturas diafisárias fechadas recentes localizadas no rádio e ulna, fêmur ou tíbia e fíbula, estabilizadas por procedimentos de osteossíntese (fixação esquelética externa, pinos intramedulares ou a associação desses métodos). Os cães foram divididos em dois grupos: fraturas estabilizadas tratadas por ultra-som de baixa intensidade (grupo tratado, n=8); fraturas estabilizadas, não tratadas por estimulação ultra-sônica, (grupo controle, n=8). Os animais foram avaliados por exames clínicos e radiográficos nos períodos pré-operatório, pós-operatório imediato e a cada 30 dias posteriores aos procedimentos cirúrgicos. Realizou-se tratamento com ultra-som pulsado (sinal senoidal com freqüência de 1,5MHz, largura de pulso de 200µs e freqüência de repetição de 1kHz) de baixa intensidade (30mW cm-2), aplicado de modo estacionário no foco de fratura. A terapia ultra-sônica foi realizada 20 minutos por dia, durante 21 dias consecutivos, a partir do período compreendido entre o 1° e o 9° dia pós-operatório. O teste t de Student, empregado na análise estatística, mostrou diferença significante (P<0,001 e alfa=0,05) entre as médias dos parâmetros de tempo para consolidação óssea observadas nos animais dos grupos tratado (média de 67,5 dias) e controle (média de 106 dias). Este protocolo de estimulação ultra-sônica promoveu sinais clínicos e radiográficos acelerados da consolidação óssea nas fraturas tratadas. Os resultados deste estudo sugerem que o ultra-som pulsado de baixa intensidade pode ser indicado como terapia adjuvante de fraturas diafisárias recentes em cães.

Vortex-Antivortex Dynamics in a Mesoscopic Superconducting Prism with a Centered Antidot

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Vortex-antivortex annihilation dynamics in a square mesoscopic superconducting cylinder

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A quantum chemical study on the formation of phosphorus mononitride

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

On the dynamic behaviour of a mass supported by a parallel combination of a spring and an elastically connected damper

This paper presents a consistent and concise analysis of the free and forced vibration of a mass supported by a parallel combination of a spring and an elastically supported damper (a Zener model). The results are presented in a compact form and the physical behaviour of the system is emphasised. This system is very similar to the conventional single-degree-of freedom system (sdof)-(Voigt model), but the dynamics can be quite different depending on the system parameters. The usefulness of the additional spring in series with the damper is investigated, and optimum damping values for the system subject to different types of excitation are determined and compared.There are three roots to the characteristic equation for the Zener model; two are complex conjugates and the third is purely real. It is shown that it is not possible to achieve critical damping of the complex roots unless the additional stiffness is at least eight times that of the main spring. For a harmonically excited system, there are some possible advantages in using the additional spring when the transmitted force to the base is of interest, but when the displacement response of the system is of interest then the benefits are marginal. It is shown that the additional spring affords no advantages when the system is excited by white noise. (c) 2007 Elsevier Ltd. All rights reserved.

Reintrodução na natureza do tamanduá-bandeira (Myrmecophaga tridactyla)após osteossíntese de rádio e ulna

A female, adult, 27 kg Giant Anteater (Myrmecophaga tridactyla) was directed to the veterinary hospital by the Center ofSelection of Wild Animals (Cetas) of the Brazilian Institute for the Environment and Renewable Natural Resources (Ibama), afterit was found on a highway. After clinical and radiologic examination, radius and ulna fractures of the left thoracic memberwere observed. Taking in consideration to the physical status of the animal, its size, the type of fracture and resources availablein the hospital veterinary, internal fixation with Intramedullary Pinning (on the Radius and Ulna) was the treatment methodchosen. About 35 days after the surgery the animal was walking without difficulties and by x-ray it was possible to observeformation of callus. The presence of decurrent bony deformities due to the type of fixation was not found. As the animal presentedno more difficulties in walking, we opted for its reintroduction to its original environment. The aim of the present casestudy is sharing the results of the Intramedullary Pinning implantation technique, widely used in dogs and cats, now used in a Giant Anteater (Myrmecophaga tridactyla).

Influence of ball-milled low purity boron powder on the superconductivity of MgB2

MgB2 samples were prepared using as-supplied commercial 96% boron with strong crystalline phase and the same 96% boron (B) after ball milling. The effects of the properties of the starting B powder on the superconductivity were evaluated. We observed that samples using ball-milled 96% B, in comparison with the one made from the as-supplied 96% B, were character- ized by small grain size, broadened full width at half maximum (FWHM), and enhanced magnetic critical current density (J(c)). J(c) reached 2 x 10(3) Acm(-2) at 5 K and 8 T. The improved pinning of these samples seems to be caused by enhanced grain boundary pinning at high field.

Addition of Ca-compounds nanoparticles in melt-textured Bi : 2212

Superconducting BSCCO samples made by melt-texturing process were prepared with the addition of calcium zirconate and calcium silicate nanoparticles. Bi:2212 melt-textured composites prepared with I wt.% of either addition showed different behavior for the critical current density as a function of the applied field, indicating that for each additional compound the improvement can be associated to different enhancement mechanisms, such as the creation of pinning centers and the increase on the connectivity of the grains. The estimated pinning forces indicated higher values for the calcium compound containing samples. (c) 2007 Elsevier B.V. All rights reserved.

The effect of microwave annealing on the electrical characteristics of lanthanum doped bismuth titanate films obtained by the polymeric precursor method

Lanthanum doped bismuth titanate thin films (Bi3.25La0.75Ti3O12-BLT) were produced by the polymeric precursor method and crystallized in a domestic microwave oven and in conventional furnace. Using platinum coated silicon substrates configuration, ferroelectric properties of the films were determined with remanent polarization P-r and a coercive field E-c of 3.9 mu C/cm(2) and 70 kV/cm for the film annealed in the microwave oven and 20 mu C/cm(2) and 52 kV/cm for the film annealed in conventional furnace, respectively. The films annealed in conventional furnace exhibited excellent retention-free characteristics at low infant periods indicating that BLT thin films can be a promise material for use in nonvolatile memories. on the other hand, the pinning of domains wall causes a strong decay at low infant periods for the films annealed in the microwave furnace which makes undesireable the application for future FeRAMS memories. (c) 2005 Elsevier B.V. All rights reserved.

Surface effects on moving vortices in superconducting stripes

Size and surface dynamical effects are investigated in thin superconducting stripes with variable width. We perform numerical simulations of the vortex dynamics, with the inclusion of the surface confining potential and a random distribution of pinning centers. To fully characterize the vortex flow, we calculate the differential resistance, the transverse diffusion coefficient, the structure factor and the intensity of the Bragg peaks, as functions of the transport force. We found that surface effects induce a premature ordering of the flux line lattice, and the system displays plastic and smectic behavior only in a very narrow range of forces. (c) 2007 Elsevier B.V. All rights reserved.

Structural and dielectric properties of Ba0.5Sr0.5(SnxTi1-x)O-3 ceramics obtained by the soft chemical method

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)