Synchronization in the presence of memory

We study the effect of memory on synchronization of identical chaotic systems driven by common external noises. Our examples show that while in general synchronization transition becomes more difficult to meet when memory range increases, for intermediate ranges the synchronization tendency of systems can be enhanced. Generally the synchronization transition is found to depend on the memory range and the ratio of noise strength to memory amplitude, which indicates on a possibility of optimizing synchronization by memory. We also point out on a close link between dynamics with memory and noise, and recently discovered synchronizing properties of networks with delayed interactions

The Ferromagnetic Potts model under an external magnetic field: an exact renormalization group approach

The q-state ferromagnetic Potts model under a non-zero magnetic field coupled with the 0^th Potts state was investigated by an exact real-space renormalization group approach. The model was defined on a family of diamond hierarchical lattices of several fractal dimensions d_F. On these lattices, the renormalization group transformations became exact for such a model when a correlation coupling that singles out the 0^th Potts state was included in the Hamiltonian. The rich criticality presented by the model with q=3 and d_F=2 was fully analyzed. Apart from the Potts criticality for the zero field, an Ising-like phase transition was found whenever the system was submitted to a strong reverse magnetic field. Unusual characteristics such as cusps and dimensional reduction were observed on the critical surface.Comment: 8 pages, 6 figures. Accepted to be published in Phys. Rev B (2006

Vertical distribution and trophic structure of the macrozooplankton in a shallow temperate estuary (Ria de Aveiro, Portugal)

The zooplankton of the lower part of Canal de Mira (Ria de Aveiro) was sampled during one lunar month. The sampling programme consisted of nine 25 hour fixed-cycles, separated weekly. In each cycle, samples were collected every two hours at three depths (surface, mid-water and above the bottom) with a 500 µm mesh net. The overall effect of the tidal phase was analyzed, taking into account the day and depth of the vertical position of the organisms through a 3-way analysis of variance (ANOVA). The zooplankton densities were, in general, higher at the surface during the night and near the bottom during the day, mainly at spring tide. The variation in the number of species followed a similar pattern to that observed for abundance. Significant differences (p<0.01) between diel and tidal phases were observed. Interaction between phase of the day and depth was also significant (p<0.05), with higher organism densities observed during night periods near the bottom. From a trophic point of view the zooplankton community of Canal de Mira was mainly composed of carnivorous and omnivorous species. Carnivores were significantly more abundant around the new and full moon (p<0.001), the omnivores at the new moon (p<0.001) and the herbivores and detritivores at the first quarter of the moon cycles (p<0.001). The density of carnivores was significantly higher at the surface at night and near the bottom during the day (p<0.05). Significant differences in the abundance of omnivores were observed between phases of the day and between depths, with higher values near the bottom during the day. The herbivores and detritivores had significantly higher densities during flood tides (p<0.001).DISTIBUICIÓN VERTICAL Y ESTRUCTURA TRÓFICA DEL MACROZOOPLANCTON EN UN ESTUARIO TEMPLADO (RIA DE AVEIRO). – El zooplancton de la parte inferior del Canal de Mira (Ria de Aveiro) fue muestreado durante un mes lunar. El programa de muestreo consistió en nueve ciclos de 25 horas, con periodicidad semanal. En cada ciclo, las muestras fueron recogidas cada dos horas, a tres profundidades (superficie, columna de agua y sobre el fondo) con una red de 500 µm. El efecto total de la fase de la marea fue analizado, teniendo en consideración el día y la profundidad en la posición vertical de los organismos con un análisis 3-Way ANOVA. Las densidades del zooplancton fueron en general más altas en la superficie durante la noche y cercanas al fondo durante el día, principalmente em la marea viva. La variación en el número de especies siguió un patrón similar al observado para la abundancia. Se observaron diferencias significativas (p<0.01) entre las fases del día y las fases de marea. La interacción entre la fase del día y la profundidad fue también significativa (p<0.05) con densidades de organismos más altas durante los periodos nocturnos en el fondo. De un punto de vista trófico, la comunidad zooplanctónica del Canal de Mira está principalmente compuesta por especies carnívoras y omnívoras. Los carnívoros fueram significativamente más abundantes cerca de la luna nueva y de la luna llena (p<0.001), los omnívoros en la luna nueva (p<0.001) y los herbívoros e detritívoros en el primero cuarto de los ciclos de la luna (p<0.001). La densidad de los carní- voros fue significativamente más alta en la superficie durante la noche y en el fondo durante el día (p<0.05). Para los omní- voros, fueron observadas diferencias significativas entre las fases del día y la profundidad, registando valores más elevados en el fondo durante el día. Los herbívoros y los detritívoros presentaron densidades significativamente superiores durante los ciclos de marea (p<0.001)

The role of the nature of the noise in the thermal conductance of mechanical systems

Focussing on a paradigmatic small system consisting of two coupled damped oscillators, we survey the role of the L\'evy-It\^o nature of the noise in the thermal conductance. For white noises, we prove that the L\'evy-It\^o composition (Lebesgue measure) of the noise is irrelevant for the thermal conductance of a non-equilibrium linearly coupled chain, which signals the independence between mechanical and thermodynamical properties. On the other hand, for the non-linearly coupled case, the two types of properties mix and the explicit definition of the noise plays a central role.Comment: 9 pages, 2 figures. To be published in Physical Review

Pneumatosis Coli Treated with Metronidazole and Hyperbaric Oxygen Therapy: A Successful Case

A pneumatose intestinal, caracterizada pela presença de gás na parede do cólon, é uma condição incomum com um espectro de apresentação variável. Pode ser idiopática ou secundária a outras doenças. A tomografia computorizada é o método de diagnóstico com maior sensibilidade. Na ausência de sinais e sintomas sugestivos de complicações, como a perfuração e a peritonite, a pneumatose intestinal pode ser tratada de forma conservadora. Apresenta-se o caso de uma mulher de 59 anos com pneumatose cólica secundária a teratoma ovárico benigno. Após a cirurgia, manteve-se sintomática e foi tratada com sucesso com metronidazol e oxigenoterapia hiperbárica

Benchtop SS-OCT – layout and performance evaluation

 Abstract1— Optical coherence tomography (OCT) is a non-invasive biomedical imaging technique that provides high speed and high resolution three dimensional and cross sectional images of biological samples, in vivo and in situ. OCT applications targeting small animals is believed to bring developments in medical techniques, instruments, diagnosis and therapies for a number of human diseases as always have been the case of animal experimentation. With the swept source OCT (SS-OCT) system presented in this work, we were able to achieve performance parameters that meet the requirements to image the retina of small animals. Performance characteristics include 105 dB for system sensitivity, a roll-off below 1 dB/mm over 3 mm depth and an axial resolution of 8 μm. We describe the layout and acquisition/processing solutions towards fast imaging of in vivo samples

Histological evaluation of the exposure to 3,4-dichloroaniline in the estuarine mysid Mesopodopsis slabberi, under experimental conditions

This work presents an experimental approach to test Mesopodopsis slabberi as a potential indicator of pollution. The toxic effects of 3,4-dichloroaniline (DCA) on the histology of this estuarine mysid were studied. After an acclimation period of two days, the mysids were exposed to different sublethal 3,4-DCA concentrations (0.10, 0.30, 0.50, 0.90, 1.00, 1.10, 1.20, 1.30 and 1.40 mg/L), for a period of 48 h. Each concentration had seven replicates, and one control. After the exposure period, organisms were sacrificed and submitted to a standard histological procedure with some modifications. Histological effects were analyzed in several tissues and damages were found in organisms exposed to concentrations higher then 0.30 mg/L. Muscular tissue, cuticular lens and gonads were clearly affected by 3,4-DCA, presenting accumulations of this toxic substance and lesions on the structures