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Band Frequencies (band + frequency)
Selected AbstractsHigh-frequency gamma oscillations coexist with low-frequency gamma oscillations in the rat visual cortex in vitroEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2010Olaleke O. Oke Abstract Synchronization of neuronal activity in the visual cortex at low (30,70 Hz) and high gamma band frequencies (> 70 Hz) has been associated with distinct visual processes, but mechanisms underlying high-frequency gamma oscillations remain unknown. In rat visual cortex slices, kainate and carbachol induce high-frequency gamma oscillations (fast-,; peak frequency , 80 Hz at 37°C) that can coexist with low-frequency gamma oscillations (slow-,; peak frequency , 50 Hz at 37°C) in the same column. Current-source density analysis showed that fast-, was associated with rhythmic current sink-source sequences in layer III and slow-, with rhythmic current sink-source sequences in layer V. Fast-, and slow-, were not phase-locked. Slow-, power fluctuations were unrelated to fast-, power fluctuations, but were modulated by the phase of theta (3,8 Hz) oscillations generated in the deep layers. Fast-, was spatially less coherent than slow-,. Fast-, and slow-, were dependent on ,-aminobutyric acid (GABA)A receptors, ,-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and gap-junctions, their frequencies were reduced by thiopental and were weakly dependent on cycle amplitude. Fast-, and slow-, power were differentially modulated by thiopental and adenosine A1 receptor blockade, and their frequencies were differentially modulated by N -methyl- d -aspartate (NMDA) receptors, GluK1 subunit-containing receptors and persistent sodium currents. Our data indicate that fast-, and slow-, both depend on and are paced by recurrent inhibition, but have distinct pharmacological modulation profiles. The independent co-existence of fast-, and slow-, allows parallel processing of distinct aspects of vision and visual perception. The visual cortex slice provides a novel in vitro model to study cortical high-frequency gamma oscillations. [source] Genetic Relationship of Pyrenophora graminea, P. teres f. maculata and P. teres f. teres Assessed by RAPD AnalysisJOURNAL OF PHYTOPATHOLOGY, Issue 2 2007J. Bakonyi Abstract Barley-pathogenic Pyrenophora isolates are P. graminea (PG), P. teres f. maculata (PTM) and P. teres f. teres (PTT), which cause foliar leaf stripe, spot blotch and net blotch lesions, respectively. However, the species are often indistinguishable by morphological and cultural characteristics. Random amplified polymorphic DNA (RAPD) analysis has been used to study the genetic relationship amongst 11 PG, 9 PTM and 23 PTT isolates from distant geographical locations. Using seven primers, 55 (52.38%) polymorphic DNA bands were detected out of 105 different fragments amplified in the three pathogens. Genotypic diversity was high as all but two PTT strains had distinct multilocus RAPD fingerprints. Unweighted pair-group method with arithmetic average (UPGMA) clustering separated the isolates into three main clusters, corresponding to the three pathogens studied. No clear geographical substructuring was found. Nei's gene diversity analysis detected only small differences (max. 6.6%) in band frequencies but considerable levels of differentiation were observed among the pathogen species/forms. However, the variability among the Pyrenophora species/forms (max. 42.0%) was less than within species/forms (max. 58%). Nei's unbiased genetic distance values were in agreement with UPGMA clustering and gene diversity analysis: the two forms of P. teres showed higher divergence from one another (D = 0.132) than the distance found between PG and PTM (D = 0.094). The results suggest that the present taxonomical classification of these morphological taxa may not correspond to their phylogenetic relationship and that there is a very close genetic relationship amongst barley-pathogenic Pyrenophora species, but genetic exchanges between them could be infrequent. [source] High pressure Raman study of carotene-encapsulating single-wall carbon nanotubesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2009J. Arvanitidis Abstract The pressure response of carotene-encapsulating single-wall carbon nanotubes is investigated by means of Raman spectroscopy. The pressure evolution of the tangential G band frequencies of the carbon nanotubes is linear without any specific features. On the other hand, the pressure response of the carotene's ,1 mode frequency is quite distinct, having a smaller low pressure slope than that reported in the literature for the molecule. This behaviour is compatible with the pressure screening effect in the interior of carbon nanotubes. For pressure higher than 2 GPa, the pressure slope becomes even smaller, an effect which can be attributed to the theoretically predicted cross-section deformation of the encapsulating tubes. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Affective response to 5 µT ELF magnetic field-induced physiological changesBIOELECTROMAGNETICS, Issue 2 2007Paul Stevens Abstract Research into effects of weak magnetic fields (MFs) at biologically relevant frequencies has produced ambiguous results. Although they do affect human physiology and behaviour, the direction of effects is inconsistent, with a range of complex and unrelated behaviours being susceptible. A possible explanation is that these effects, rather than being directly caused, are instead related to changes in affective state. A previous study showed that MFs altered the affective content of concurrent perceptions, but it was unclear whether the emotional response was direct or indirect. Here it is shown that exposure to a 0,5 µT MF (DC-offset sinudsoidal wave form) within EEG ,-band frequencies (8,12 Hz), results in a reported change in emotional state. This relates to a decrease global field power but lacks the frontal ,-asymmetry that would physiologically indicate a directly induced emotional state, suggesting that participant experiences are due to an interpretation of the effects of MF exposure. Bioelectromagnetics © 2006 Wiley-Liss, Inc. [source] Raman spectroscopy of secondary structure of elastinlike polymer poly(GVGVP)BIOPOLYMERS, Issue 3 2001Pavel Schmidt Abstract Raman spectra of the elastinlike polypentapeptide poly(GVGVP) were measured in H2O and D2O as solutions and, after increasing the temperature, as suspensions and sediments. In addition, spectra of the polypentapeptide in the solutions of increasing concentration and in the solid state were also investigated by gradually evaporating the water. Significant changes in band frequencies, intensities, and shapes were found for selected Raman bands in the measured spectra, particularly for the CH stretching, the glycine CH2 wagging, and some amide vibrations. The CH stretching vibrations are influenced predominantly by the presence of water, the glycine CH2 wagging vibrations are associated with conformational transitions. Three possible types of poly(GVGVP)s in the presence of water were indicated: polymer chains in a relatively extended state in the solution, a ,-spiral structure in the suspension, and irregularly bent chains in the sediment. © 2001 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 62: 150,157, 2001 [source] A novel selectivity technique for high impedance arcing fault detection in compensated MV networksEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2008Nagy I. Elkalashy Abstract In this paper, the initial transients due to arc reignitions associated with high impedance faults caused by leaning trees are extracted using discrete wavelet transform (DWT). In this way, the fault occurrence is localized. The feature extraction is carried out for the phase quantities corresponding to a band frequency 12.5,6.25,kHz. The detection security is enhanced because the DWT corresponds to the periodicity of these transients. The selectivity term of the faulty feeder is based on a novel technique, in which the power polarity is examined. This power is mathematically processed by multiplying the DWT detail coefficients of the phase voltage and current for each feeder. Its polarity identifies the faulty feeder. In order to reduce the computational burden of the technique, the extraction of the fault features from the residual components is examined. The same methodology of computing the power is considered by taking into account the residual voltage and current detail coefficients where the proposed algorithm performs best. Test cases provide evidence of the efficacy of the proposed technique. Copyright © 2007 John Wiley & Sons, Ltd. [source] Genetic variation in remnant Festuca hallii populations is weakly differentiated, but geographically associated across the Canadian PrairiePLANT SPECIES BIOLOGY, Issue 3 2009JIE QIU Abstract Genetic diversity is essential for predicting plant evolutionary potential and for formulating conservation strategies. However, little is known about the genetic variation of plains rough fescue [Festuca hallii (Vasey) Piper], a widespread and diagnostic grass in the Fescue Prairie. We used the amplified fragment length polymorphism (AFLP) technique to assess the genetic variation of 30 fragmented populations of F. hallii across the northern Canadian Prairie and its associations with 12 geographical, fragmentation and environmental attributes. Three AFLP primer pairs were used to screen 840 samples, representing approximately 30 samples from each population, and 246 polymorphic bands were scored. The fescue plant was genetically diverse, as revealed by the proportion of polymorphic bands (0.870,0.967), the mean band frequency (0.364,0.457) and the within-population variation (69.4,85.4). The genetic variation was not highly differentiated, with only 6.5% of the total AFLP variation residing among populations. A Mantel test revealed a significant correlation between genetic and geographical distances (r = 0.39; P < 0.004) and a spatial autocorrelation up to 60 km among populations was detected. The AFLP variation displayed a longitudinal decline and was significantly associated with environmental attributes related to moisture, indicating local adaptation. However, the AFLP variation was not significantly associated with the estimated population size and geographical distance to the nearest neighbor, suggesting that fragmentation has not generated considerable genetic impact on the fescue populations. Implications for fescue conservation, restoration and management are discussed. [source] | ||||||||||