3,419 research outputs found
Resonance induced by repulsive interactions in a model of globally-coupled bistable systems
We show the existence of a competition-induced resonance effect for a generic
globally coupled bistable system. In particular, we demonstrate that the
response of the macroscopic variable to an external signal is optimal for a
particular proportion of repulsive links. Furthermore, we show that a resonance
also occurs for other system parameters, like the coupling strength and the
number of elements. We relate this resonance to the appearance of a multistable
region, and we predict the location of the resonance peaks, by a simple
spectral analysis of the Laplacian matrix
Revestimentos decorativos pelo efeito SPR obtido pela adição de Au a matrizes dieléctricas
A SPR (ressonância dos plasmões de superfície) originada pela introdução de nanopartículas metálicas em matrizes dieléctricas possui um elevado leque de aplicações, sendo alvo de uma actividade intensa de investigação. De modo a tirar partido da forte extinção da luz em certas gamas do visível que estes sistemas proporcionam, foi objectivo deste trabalho desenvolver revestimentos nanocompósitos com efeito SPR para aplicações decorativas. Para tal, recorreu-se à técnica de pulverização catódica reactiva para depositar os revestimentos nanocompósitos consistindo em nanopartículas de Au dispersas em matrizes de WO3 e Al2O3. Por outro lado, pela aplicação de tratamentos térmicos pós-deposição foi promovido o crescimento das nanopartículas de Au.
A incorporação crescente de diferentes teores em Au na matriz permitiu a presença de nanopartículas com tamanhos
maiores. Além disso, os tratamentos térmicos influenciaram com sucesso o crescimento das nanopartículas de Au na matriz, permitindo alterar a posição, forma e intensidade dos picos de SPR e, onsequentemente, a coloração obtida para as amostras. Contudo, também as propriedades estruturais e dieléctricas da matriz foram afectadas pela temperatura de recozimento,
como por exemplo um aumento do índice de refracção que promoveu um deslocamento da posição dos picos de SPR para o “vermelho” (sistema W-O+Au). Nos resultados alcançados houve por isso um efeito combinado entre o crescimento das
nanopartículas e a variação do índice de refracção da matriz. Através da variação de três parâmetros, matriz, composição
química e temperatura de recozimento, foi possível depositar revestimentos nanocompósitos de WO3+Au e AlO+Au com
diferentes cores pelo ajuste dos picos de SPR das nanopartículas de Au.The deposition of thin films consisting of metallic clusters embedded in dielectric matrixes can originate a
strong SPR (Surface Plasmon Resonance) signal that has a wide range of applications, being the subject of an intense research
nowadays. The main idea of this research work was to utilize the strong extinction of light that arises in these systems
in certain zones of the visible spectrum for decorative coatings. Nanocomposite coatings consisting of Au clusters embedded
in a WO3 or Al2O3 matrix were prepared by reactive sputtering with different Au contents. The higher the Au contents in the
coatings the larger the nanoparticles were. By further annealing these samples at increasing temperatures, the Au segregation
in the matrix was promoted. Both events permit to determine the SPR peak position along with its shape and intensity and,
consequently, the optical properties of the coatings. Moreover, the thermal treatments also influenced the optical characteristics
of the matrix, e.g. the refractive index was increased, leading to the redishing of the SPR position. Thus, the final results
attained in the SPR peak shape, intensity and position for each case were mainly due to a combined effect between the Au
cluster size and the refractive index of the oxide matrix.
By varying the three major experimental parameters, the oxide matrix, the Au composition and the annealing temperature, it
was possible to achieve nanocomposite coatings of WO3+Au and AlO+Au with different colours by tailoring the SPR peak
shape and position.FCT - DECOMAT (PTDC/CTM/70037/2006), FEDER, através do programa COMPETE - Programa Operacional Factores de Competitividade
Rate adaptation for wireless video streaming based on error statistics
This paper presents a new rate-control algorithm for live video streaming over wireless IP networks, which is based on selective frame discarding. In the proposed mechanism excess 'P' frames are dropped from the output queue at the sender using a congestion estimate based on packet loss statistics obtained from RTCP feedback and from the Data Link (DL) layer. The performance of the algorithm is evaluated through computer simulation. This paper also presents a characterisation of packet losses owing to transmission errors and congestion, which can help in choosing appropriate strategies to maximise the video quality experienced by the end user. Copyright © 2007 Inderscience Enterprises Ltd
The Quantum Stress-Tensor in Self-Similar Spherical Dust Collapse
We calculate the quantum stress tensor for a massless scalar field in the 2-d
self-similar spherical dust collapse model which admits a naked singularity. We
find that the outgoing radiation flux diverges on the Cauchy horizon. This may
have two consequences. The resultant back reaction may prevent the naked
singularity from forming, thus preserving cosmic censorship through quantum
effects. The divergent flux may lead to an observable signature differentiating
naked singularities from black holes in astrophysical observations.Comment: Latex File, 19 page
Stress-Related Mucosal Disease: Incidence of Bleeding and the Role of Omeprazole in its Prophylaxis
BACKGROUND: Upper gastrointestinal bleeding is the severe complication of stress-related mucosal disease in hospitalized patients. In intensive care units (ICU), risk factors are well defined and only mechanical ventilation and coagulopathy proved to be relevant for significant bleeding. On the contrary, in non-ICU settings there is no consensus about this issue. Nevertheless, omeprazole is still widely used in prophylaxis of bleeding. The objective of our study was to evaluate the relevance of stress-related mucosal disease bleeding in patients admitted to an internal medicine ward, and the role of omeprazole in its prophylaxis.
METHODS: We conducted a retrospective study in which we analysed consecutive patients who were admitted to our ward over a year. We recorded demographic characteristics of the patients, potential risk factors for stress-related mucosal disease (clinical data, laboratory, and medication), administration of prophylactic omeprazole, and total cost of this prophylaxis. Patients with active gastrointestinal bleeding on the admission were excluded. We recorded every upper gastrointestinal bleeding event with clinical relevance.
RESULTS: Five hundred and thirty-five patients, mean age 70 years, mean length of stay 9.6+/-7.7 days; 140 (26.2%) patients were treated with 40 mg of omeprazole intravenously, 193 (36.1%) with 20mg of omeprazole orally, and 202 (37.8%) patients had no prophylaxis. There was only one episode (0.2%) of clinically relevant bleeding.
CONCLUSION: In patients admitted to an internal medicine ward, incidence of upper gastrointestinal bleeding as a complication of stress-related mucosal disease is low. We found that there is no advantage in prophylaxis with omeprazole
Switching of +/-360deg domain wall states in a nanoring by an azimuthal Oersted field
We demonstrate magnetic switching between two domain wall vortex
states in cobalt nanorings, which are candidate magnetic states for robust and
low power MRAM devices. These domain wall (DW) or "twisted onion"
states can have clockwise or counterclockwise circulation, the two states for
data storage. Reliable switching between the states is necessary for any
realistic device. We accomplish this switching by applying a circular Oersted
field created by passing current through a metal atomic force microscope tip
placed at the center of the ring. After initializing in an onion state, we
rotate the DWs to one side of the ring by passing a current through the center,
and can switch between the two twisted states by reversing the current, causing
the DWs to split and meet again on the opposite side of the ring. A larger
current will annihilate the DWs and create a perfect vortex state in the rings.Comment: 5 pages, 5 figure
Using plantar pressures for improving arch support for shoe customization
The footwear industry is evolving from a laborintensive work to a knowledge-based
manufacturing process, developing customized
and personalized products in order to meet the
customer needs [1]. Pathologies like high arch
and flat foot are widely studied and some
orthoses have shown positive results in treatment
[1, 4]. The objective of this work was to
customize the design of a comfort shoe
(Arcopédico), so it could be adapted to three
major foot types (pes cavus, planus and normal).N/
The effect of feed supplementation with inulin on boar taint levels and meat quality of entire male pigs
Received: March 19th, 2022 ; Accepted: May 3rd, 2022 ; Published: July 5th, 2022 ; Correspondence: [email protected] and androstenone are the two main compounds responsible for the foul odour
in entire male pigs’ meat, known as boar taint. This study evaluated the effect of feed
supplementation with inulin on the boar taint levels of 30 entire male pigs. Two months before
slaughter, the animals were allocated into three groups (n = 10). The control group received a
standard commercial diet. The other groups were fed the same commercial diet with 3% and 6%
added inulin, respectively. Results showed that inulin addition to the feed significantly reduced
skatole levels in the pigs’ adipose tissue compared with the control group. The levels of
androstenone were not affected by the dietary approach. Although there were differences in some
parameters, the supplementation with inulin did not promote extensive changes in the meat
quality parameters between the tested groups. When raising entire males, supplementation with
inulin in finishing diets could be considered to reduce the boar taint perception by the consumer
Thermal analysis in drilling of ex vivo bovine bones
Bone drilling is a common procedure in Medicine, mainly in traumatology and orthopedic procedure for fractures fixation and in reconstructive surgery. The success of this surgical procedure is dependent on many factors, namely, on heat generation control during the bone drilling. The main concern in bone drilling is the mechanical and thermal damage of the bone induced by inappropriate parameters such as drill speed and feed-rate during the drilling. This study focuses on the temperature generated during drilling of cortical bone tissue (bovine origin) and solid rigid polyurethane foams with similar mechanical properties to the human bone tissue. Different parameters such as drill speed, feed-rate and hole depth were tested. All results showed that improvement of the drilling parameters and the drill temperatures can be estimated. It was concluded that when the drill speed and feed-rate were higher, the bone temperature increase was lower. The obtained results of temperature in the drilling process of polyurethane foam blocks or bovine bone were compared with a good agreement in between both. © 2017 World Scientific Publishing Company.This research was supported by the Portuguese Foundation of Science and Technology under research project UID/EMS/50022/2013.info:eu-repo/semantics/publishedVersio
Soliton Induced Singularities in 2 d Gravity and their Evaporation
Positive energy singularities induced by Sine-Gordon solitons in 1+1
dimensional dilaton gravity with positive and negative cosmological constant
are considered. When the cosmological constant is positive, the singularities
combine a white hole, a timelike singularity and a black hole joined smoothly
near the soliton center. When the cosmological constant is negative, the
solutions describe two timelike singularities joined smoothly near the soliton
center. We describe these spacetimes and examine their evaporation in the one
loop approximation.Comment: 15 pages (37.7 kb), PHYZZX. Figures available from authors
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