479 research outputs found
Stationarity and geometric ergodicity of a class of nonlinear ARCH models
A class of nonlinear ARCH processes is introduced and studied. The existence
of a strictly stationary and -mixing solution is established under a
mild assumption on the density of the underlying independent process. We give
sufficient conditions for the existence of moments. The analysis relies on
Markov chain theory. The model generalizes some important features of standard
ARCH models and is amenable to further analysis.Comment: Published at http://dx.doi.org/10.1214/105051606000000565 in the
Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute
of Mathematical Statistics (http://www.imstat.org
Comparative Measurements of Inverse Spin Hall and Magnetoresistance in YIG|Pt and YIG|Ta
We report on a comparative study of spin Hall related effects and
magnetoresistance in YIG|Pt and YIG|Ta bilayers. These combined measurements
allow to estimate the characteristic transport parameters of both Pt and Ta
layers juxtaposed to YIG: the spin mixing conductance
at the YIGnormal metal interface, the spin Hall angle , and the
spin diffusion length in the normal metal. The inverse spin Hall
voltages generated in Pt and Ta by the pure spin current pumped from YIG
excited at resonance confirm the opposite signs of spin Hall angles in these
two materials. Moreover, from the dependence of the inverse spin Hall voltage
on the Ta thickness, we extract the spin diffusion length in Ta, found to be
nm. Both the YIG|Pt and YIG|Ta systems
display a similar variation of resistance upon magnetic field orientation,
which can be explained in the recently developed framework of spin Hall
magnetoresistance.Comment: 8 pages, 5 figures, 1 tabl
Detection of the microwave spin pumping using the inverse spin Hall effect
We report electrical detection of the dynamical part of the spin pumping
current emitted during ferromagnetic resonance (FMR) using the inverse Spin
Hall Effect (ISHE). The experiment is performed on a YIGPt bilayer. The
choice of YIG, a magnetic insulator, ensures that no charge current flows
between the two layers and only pure spin current produced by the magnetization
dynamics are transferred into the adjacent strong spin-orbit Pt layer via spin
pumping. To avoid measuring the parasitic eddy currents induced at the
frequency of the microwave source, a resonance at half the frequency is induced
using parametric excitation in the parallel geometry. Triggering this nonlinear
effect allows to directly detect on a spectrum analyzer the microwave component
of the ISHE voltage. Signals as large as 30 V are measured for precession
angles of a couple of degrees. This direct detection provides a novel efficient
means to study magnetization dynamics on a very wide frequency range with great
sensitivity
Sex differences in the association of postural control with indirect measures of body representations
Besides anthropometric variables, high-order body representations have been hypothesised to influence postural control. However, this has not been directly tested before. Moreover, some studies indicate that sex moderates the relationship of anthropometry and postural control. Therefore, as a proof of concept we investigated the association of body representations with postural control as well as the influence of participants’ sex/gender. Body image measures were assessed with a figural drawing task. Body schema was tested by a covert and an overt task. Body sway was measured during normal bipedal quiet standing with eyes closed (with/without neck extended). Statistical analysis consisted of hierarchical multiple linear regressions with the following regression steps: (1) sensory condition, (2) sex/gender, (3) age, (4) anthropometry, (5) body schema, (6) body image, (7) sex/gender-interactions. Across 36 subjects (19 females), body schema was significantly associated with body sway variability and open-loop control, in addition to commonly known influencing factors, such as sensory condition, gender, age and anthropometry. While in females, also body image dissatisfaction substantially was associated with postural control, this was not the case in males. Sex differences and possible causes why high-order body representations may influence concurrent sensorimotor control of body sway are discussed
Adhesive systems modified with antimicrobial agents: a literature review
A cárie secundária é a principal causa de falha da restauração. Assim, o desenvolvimento de adesivos com ação antimicrobiana é uma opção vantajosa para sua inibição. No entanto, esse efeito deve ser comprovado, bem como que o benefício adicional não interfere nas propriedades mecânicas do material ou na biocompatibilidade. Analisamos adesivos com ação antimicrobiana por meio de testes microbiológicos, resistência de união, grau de conversão e citotoxicidade. Analisamos 32 estudos com adesivos antimicrobianos disponíveis comercialmente (Clearfil ™ SE Protect Bond / MDPB, Gluma 2Bond / glutaraldeído, Peak Universal Bond / clorexidina) e materiais experimentais ou adesivos comerciais modificados com agentes antimicrobianos, incluindo materiais com metacrilato de amônio quaternário (QAM) [metacrilato de dimetilaminododecil (DMADDM) e metacrilato de dimetilaminohexadecil (DMAHDM)], nanopartículas [prata (NAg), dióxido de titânio (TiO2), óxido de zinco (ZnO)], vidro bioativo dopado com prata ou zinco (BAG), titânio, iodo de titânio, cobre e compostos como triclosan, quercetina, extrato de semente de uva, entre outros. O uso de agentes antimicrobianos é uma perspectiva favorável para a funcionalização de sistemas adesivos para inibir a cárie secundária. No entanto, mais estudos clínicos precisam provar a eficácia desses materiais.Secondary caries is the primary cause of restoration failure. Thus, the development of adhesives with antimicrobial action is an advantageous option for their inhibition. However, this effect must be proven, as well as that the additional benefit does not interfere with material mechanical properties or biocompatibility. We analyzed adhesives with antimicrobial action by microbiological tests, bond strength, degree of conversion, and cytotoxicity. We analyzed 32 studies with commercially available antimicrobial adhesives (Clearfil™ SE Protect Bond/ MDPB, Gluma 2Bond/ glutaraldehyde, Peak Universal Bond/chlorhexidine), and experimental materials or commercial adhesives modified with antimicrobial agents, including materials with quaternary ammonium methacrylate (QAM) [dimethylaminododecyl methacrylate (DMADDM) and dimethylaminohexadecyl methacrylate (DMAHDM)], nanoparticles [silver (NAg), titanium dioxide (TiO2), zinc oxide (ZnO)], silver or zinc doped bioactive active glass (BAG), titanium, copper iodide, and compounds such as triclosan, quercetin, grape seed extract, among others. The use of antimicrobial agents is a favorable perspective for the functionalization of adhesive systems to inhibit secondary caries. However, more clinical studies need to prove the efficacy of these materials
FPGA Implementation Of Diffusive Realization For A Distributed Control Operator
International audienceWe focus on the question of real-time computation for optimal distributed filtering or control applicable to MEMS Arrays. We present an algorithm for the realization of a linear operator solution to a functional equation through its application to a Lyapunov operatorial equation associated to the heat equation in one dimension. It is based on the diffusive realization, and turns to be well suited for fined grained parallel computer architecture as Field Programmable Gate Arrays (FPGA). An effective FPGA implementation has been successfully carried out. Here, we report the main implementation steps and the final measured performances
Avaliação da contração de polimerização de três resinas compactáveis, medida por picnômetro a gás
Modern restorative dentistry has been playing an outstanding role lately since composite resins, allied to adhesive systems, have been widely applied on anterior and posterior teeth restorations. The evolution of composite resins has mostly been verified due to the improvement of their aesthetic behavior and the increase in their compressive and abrasive strengths. In spite of these developments, the polymerization shrinkage inherent to the material has been a major deficiency that, so far, has been impossible to avoid. Using a gas pycnometry, this research investigated the polymerization shrinkage of three packable composite resins: Filtek P60 (3M), Prodigy Condensable (Kerr), and SureFil (Dentsply/Caulk), varying the distance from the light source to the surface of the resins (2 mm or 10 mm). The pycnometer Accupyc 1330 (Micromeritics, USA) precisely records helium displacement, allowing fast and reliable measurements of the volume of composite resin immediately before and after polymerization, without interference of temperature or humidity. Results were not found to be statistically different for the three tested resins, either for 2 mm or 10 mm-distance from the light source to the composite surface.A Odontologia Restauradora moderna tem se destacado nos últimos anos e as resinas compostas, aliadas aos sistemas adesivos, têm sido muito empregadas para restaurações de dentes anteriores e posteriores. A evolução das resinas compostas tem sido constatada na melhoria do seu comportamento estético e no aumento da sua resistência à compressão e à abrasão. Apesar dos avanços mencionados, a contração de polimerização, inerente a esse material, continua sendo uma grande deficiência e, por enquanto, impossível de ser evitada. Nesta pesquisa a contração de polimerização de três resinas compostas compactáveis, Filtek P60 (3M), Prodigy Condensável (Kerr) e SureFil (Dentsply/Caulk), variando-se a distância entre a fonte de luz e a superfície das resinas em 2 mm e 10 mm, foi avaliada pelo método da picnometria a gás. O aparelho picnômetro Accupyc 1330 (Micromeritics, EUA) mede o deslocamento de gás hélio com grande precisão, permitindo medições rápidas e fiéis do volume das resinas compostas antes e após a polimerização, sem interferência da temperatura e da umidade. Os resultados mostraram que não houve diferenças estatisticamente significantes entre as três resinas avaliadas. Independentemente do tipo de resina composta, também não houve diferenças significantes para as distâncias de polimerização de 2 mm e 10 mm
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