Interferometric mapping of Magnetic fields: G30.79 FIR 10

We present polarization maps of G30.79 FIR 10 (in W43) from thermal dust emission at 1.3 mm and from CO J=$2 \to 1$ line emission. The observations were obtained using the Berkeley-Illinois-Maryland Association array in the period 2002-2004. The G30.79 FIR 10 region shows an ordered polarization pattern in dust emission, which suggests an hourglass shape for the magnetic field. Only marginal detections for line polarization were made from this region. Application of the Chandrashkar-Fermi method yielded $B_{pos} \approx 1.7$ mG and a statistically corrected mass to magnetic flux ratio $\lambda_{C} \approx 0.9$, or essentially critical.Comment: 11 pages, 2 Figures, Published in Ap

The effect of neural adaptation of population coding accuracy

Most neurons in the primary visual cortex initially respond vigorously when a preferred stimulus is presented, but adapt as stimulation continues. The functional consequences of adaptation are unclear. Typically a reduction of firing rate would reduce single neuron accuracy as less spikes are available for decoding, but it has been suggested that on the population level, adaptation increases coding accuracy. This question requires careful analysis as adaptation not only changes the firing rates of neurons, but also the neural variability and correlations between neurons, which affect coding accuracy as well. We calculate the coding accuracy using a computational model that implements two forms of adaptation: spike frequency adaptation and synaptic adaptation in the form of short-term synaptic plasticity. We find that the net effect of adaptation is subtle and heterogeneous. Depending on adaptation mechanism and test stimulus, adaptation can either increase or decrease coding accuracy. We discuss the neurophysiological and psychophysical implications of the findings and relate it to published experimental data.Comment: 35 pages, 8 figure

Combining Radio and PIT-Telemetry to Study the Large and Fine-Scale Movements of Stocked and Wild Brown Trout (Salmo trutta L.) in a Northeastern Stream, Portugal

Stream-resident salmonid movements have been the subject of numerous studies and their behaviour is relatively well-known (Harcup et al., 1984; Heggenes, 1988). For example, brown trout (Salmo trutta) is described as a sedentary species based on the behaviour displayed, often associated to the strong site attachment to a territory or home range (Bridcut & Giller, 1993; Armstrong & Herbert, 1997). Other salmonids like brook (Salvelinus fontinalis) (Roghair & Dolloff, 2005) and cutthroat trout (Oncorhynchus clarki) (Hegennes et al., 1991) showed similar behaviour. However, there are studies reporting a wide range of movements for brown (Meyers et al., 1992; Young, 1994), cutthroat (Hilderbrand & Kershner, 2000) and brook (Gowan & Fausch, 1996) trout populations. Trout behaviour can be modified by natural (e.g. fish density, food availability) and especially by man induced factors (e.g. environmental degradation, harvest and stocking) responsible for major threats of wild populations (Laikre et al., 2000). Indeed, stocking of hatchery-reared brown trout is a management tool commonly used to improve the recreational fishing (Cowx, 1999). This activity is responsible for a sudden artificial increase of fish density in a particular area. Negative impacts on wild populations, such as genetic contamination, competition, predator attraction and disease transmission were often referred (White et al., 1995; Einum & Fleming, 2001; Weber & Fausch, 2003) and are potentially amplified with the dispersal failure, since many hatchery-reared trout tend to remain near of the stocking site (Cresswell, 1981; Aarestrup et al., 2005). There are also contradictory results, as reported by Bettinger & Bettoli (2002) where stocked trout dispersal reached over 12 km in the downstream direction, just 24 hours after their release. Cortes et al. (1996) found for Portuguese salmonid streams that, during three successive years (2000 to 2003), less than 20% of stocked brown trout remained in the stream segment, one month after the release. However, in this study a mark-recapture method was used that did not allow to assess the main causes of the fish depletion and was not appropriate for the observation of fish behaviour

Statistical Mechanics of Support Vector Networks

Using methods of Statistical Physics, we investigate the generalization performance of support vector machines (SVMs), which have been recently introduced as a general alternative to neural networks. For nonlinear classification rules, the generalization error saturates on a plateau, when the number of examples is too small to properly estimate the coefficients of the nonlinear part. When trained on simple rules, we find that SVMs overfit only weakly. The performance of SVMs is strongly enhanced, when the distribution of the inputs has a gap in feature space.Comment: REVTeX, 4 pages, 2 figures, accepted by Phys. Rev. Lett (typos corrected

Interferometric Mapping of Magnetic fields: NGC2071IR

We present polarization maps of NGC2071IR from thermal dust emission at 1.3 mm and from CO J=$2 \to 1$ line emission. The observations were obtained using the Berkeley-Illinois-Maryland Association array in the period 2002-2004. We detected dust and line polarized emission from NGC2071IR that we used to constrain the morphology of the magnetic field. From CO J=$2 \to 1$ polarized emission we found evidence for a magnetic field in the powerful bipolar outflow present in this region. We calculated a visual extinction $A_{\rm{v}} \approx 26$ mag from our dust observations. This result, when compared with early single dish work, seems to show that dust grains emit polarized radiation efficiently at higher densities than previously thought. Mechanical alignment by the outflow is proposed to explain the polarization pattern observed in NGC2071IR, which is consistent with the observed flattening in this source.Comment: 17 pages, 4 Figures, Accepted for publication in Ap

Recomendações para coleta e envio de material ao laboratório de fitopatologia para diagnóstico de doenças em plantas.

Introdução. Registro de informações no campo. Recomendações gerais. Amostragem de plantas. Folhas e plantas pequenas. Plantas murchas. Vagens. Raízes. Horário de amostragem. Informações adicionais. Recebimento de amostras e procedimentos no laboratório. Observação direta em lupa e em microscópio. Isolamento de fungos fitopatogênicos. Extração de nematóides. Métodos moleculares. Serviços disponíveis. Referências.bitstream/item/86624/1/seriedocumentos-271.pd

Hysteresis and bi-stability by an interplay of calcium oscillations and action potential firing

Many cell types exhibit oscillatory activity, such as repetitive action potential firing due to the Hodgkin-Huxley dynamics of ion channels in the cell membrane or reveal intracellular inositol triphosphate (IP$_3$) mediated calcium oscillations (CaOs) by calcium-induced calcium release channels (IP$_3$-receptor) in the membrane of the endoplasmic reticulum (ER). The dynamics of the excitable membrane and that of the IP$_3$-mediated CaOs have been the subject of many studies. However, the interaction between the excitable cell membrane and IP$_3$-mediated CaOs, which are coupled by cytosolic calcium which affects the dynamics of both, has not been studied. This study for the first time applied stability analysis to investigate the dynamic behavior of a model, which includes both an excitable membrane and an intracellular IP$_3$-mediated calcium oscillator. Taking the IP$_3$ concentration as a control parameter, the model exhibits a novel rich spectrum of stable and unstable states with hysteresis. The four stable states of the model correspond in detail to previously reported growth-state dependent states of the membrane potential of normal rat kidney fibroblasts in cell culture. The hysteresis is most pronounced for experimentally observed parameter values of the model, suggesting a functional importance of hysteresis. This study shows that the four growth-dependent cell states may not reflect the behavior of cells that have differentiated into different cell types with different properties, but simply reflect four different states of a single cell type, that is characterized by a single model.Comment: 29 pages, 6 figure