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Curve Shape (curve + shape)
Selected AbstractsBioaccumulation and biotransformation of polycyclic aromatic hydrocarbons during sediment tests with oligochaetes (Lumbriculus variegatus)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2007Merja Lyytikäinen Abstract In some kinetic studies with aquatic invertebrates, the bioaccumulation of polyaromatic hydrocarbons (PAHs) has been observed to peak at the beginning of the test. This has been explained by the depletion of PAHs from pore water due to limited desorption during the bioaccumulation test or, alternatively, by the activation of biotransformation mechanisms in the organisms. In the present study, we exposed the aquatic oligochaetes, Lumbriculus variegatus, to creosote oil,contaminated sediments to examine the bioaccumulation of PAHs and to clarify the importance of contaminant depletion and biotransformation for it. The contaminant depletion was studied by replanting test organisms into fresh, nondepleted test sediments at 3-d intervals over 12 d and by comparing the resulting body burdens to those of the organisms that were not replanted. The biotransformation capability of L. variegatus was assessed by following the concentration of 1-hydroxypyrene (1-HP), a phase I metabolite of pyrene, in oligochaete tissue during a 15-d test. We observed that the bioaccumulation of most PAHs indeed peaked at the beginning of the test. The concentrations in the replanted organisms were only 1.5 to 2 times higher than in nonreplanted organisms during the first 9 d of the test and, by day 12, no differences were detected. 1-Hydroxypyrene was detected in oligochaete tissue throughout the exposures, and concentrations decreased over time. However, the proportion of 1-HP to pyrene increased linearly during the test. These results indicated that the depletion of contaminants has only a minor effect on their bioaccumulation in oligochaetes and that the cause for the observed bioaccumulation curve shape is rapid elimination of the contaminants and, possibly to some degree, their metabolites. [source] Mapping responses to frequency sweeps and tones in the inferior colliculus of house miceEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2003Steffen R. Hage Abstract In auditory maps of the primary auditory cortex, neural response properties are arranged in a systematic way over the cortical surface. As in the visual system, such maps may play a critical role in the representation of sounds for perception and cognition. By recording from single neurons in the central nucleus of the inferior colliculus (ICC) of the mouse, we present the first evidence for spatial organizations of parameters of frequency sweeps (sweep speed, upward/downward sweep direction) and of whole-field tone response patterns together with a map of frequency tuning curve shape. The maps of sweep speed, tone response patterns and tuning curve shape are concentrically arranged on frequency band laminae of the ICC with the representation of slow speeds, build up response types and sharp tuning mainly in the centre of a lamina, and all (including high) speeds, phasic response types and broad tuning mainly in the periphery. Representation of sweep direction shows preferences for upward sweeps medially and laterally and downward sweeps mainly centrally in the ICC (either striped or concentric map). These maps are compatible with the idea of a gradient of decreasing inhibition from the centre to the periphery of the ICC and by gradients of intrinsic neuronal properties (onset or sustained responding). The maps in the inferior colliculus compare favourably with corresponding maps in the primary auditory cortex, and we show how the maps of sweep speed and direction selectivity of the primary auditory cortex could be derived from the here-found maps of the inferior colliculus. [source] Subglacial drainage system structure and morphology of Brewster Glacier, New ZealandHYDROLOGICAL PROCESSES, Issue 3 2009Ian Willis Abstract A global positioning system and ground penetrating radar surveys is used to produce digital elevation models of the surface and bed of Brewster Glacier. These are used to derive maps of subglacial hydraulic potential and drainage system structure using three different assumptions about the subglacial water pressure (Pw): (i) Pw = ice overburden; (ii) Pw = half ice overburden; (iii) Pw = atmospheric. Additionally, 16 dye-tracing experiments at 12 locations were performed through a summer melt season. Dye return curve shape, together with calculations of transit velocity, dispersivity and storage, are used to infer the likely morphology of the subglacial drainage system. Taken together, the data indicate that the glacier is underlain by a channelised but hydraulically inefficient drainage system in the early summer in which water pressures are close to ice overburden. By mid-summer, water pressures are closer to half-ice overburden and the channelised drainage system is more hydraulically efficient. Surface streams that enter the glacier close to the location of major subglacial drainage pathways are routed quickly to the channels and then to the glacier snout. Streams that enter the glacier further away from the drainage pathways are routed slowly to the channels and then to the snout because they first flow through a distributed drainage system. Copyright © 2008 John Wiley & Sons, Ltd. [source] Broad versus narrow auditory tuning and corresponding bat-evasive flight behaviour in praying mantidsJOURNAL OF ZOOLOGY, Issue 1 2001Jeffrey D. Triblehorn Abstract Most praying mantids possess a single tympanal ear located in the ventral midline between the metathoracic legs. The auditory system is generally most sensitive to ultrasound in the 25,50 kHz range. Flying males exhibit a short-latency, stereotyped, multi-component response to ultrasound that allows them to escape from attacking bats. This study describes a small subset of species that differs in three major respects from the majority of mantis species: (1) their auditory tuning is 1.5,2 times broader; (2) they are sensitive to frequencies above 60 kHz (up to 130 kHz in some species) with thresholds as low or lower than at 25,50 kHz; (3) the behavioural response of the broadly tuned (BT) species includes 10,50 times more flight cessations and can be far less stereotyped, i.e. more ,evitable', than that of narrowly tuned (NT) species. However, BT species do not differ from NT species in overall sensitivity. Two species from one subfamily, the Amelinae (family Mantidae), stand out because they are among the least sensitive of any hearing mantids so far tested. Although the two amelines differ from one another in tuning curve shape, they are both more broadly tuned than most mantids. The occurrence of BT species does not follow any obvious phylogenetic pattern; they are patchily distributed among the mantis families, and both BT and NT species can be found in the same subfamily or tribe. We suggest that BT species are responding to a shared ecological pressure. Based on their tuning, the nature of their behavioural response, and their geographic distribution, we hypothesize that high duty cycle (HDC) bats (Rhinolophidae and Hipposideridae) pose a special danger to BT mantids in addition to the threat that all flying mantids face from the more common and widely distributed low duty cycle (LDC) bats. [source] Thermal annealing effects on the TL response of beta-irradiated HPHT Ib type synthetic diamondPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2007S. Preciado-Flores Abstract It is known that room temperature beta-irradiated Ib type diamond generates a non-reproducible TL glow curve shape, due to mobility of the impurity-vacancy (I ,V) and interstitials (I) defects in the 30,800 °C temperature range. This situation may hinder the use of this type of diamond material in dose assessment applications. The recurring heating of the Ib type diamond sample changes the defects concentration and consequently the intensity of the TL glow peaks associated to the characteristic temperature annealing stages. In the present work we have performed thermal annealing (TA) treatment on an Ib type diamond in the 100,800 °C range previous to beta irradiation. It was observed that after the 800 °C annealing treatment the TL glow curve showed 3,5% reproducibility, in contrast to the non-reproducible TL observed in non-annealed diamond, and remained the same after two months of successive TL read outs. Moreover, the 800 °C annealing treatment assured a linear integrated TL dose behavior, a significant improvement over non-annealed samples that could facilitate the employment of Ib type synthetic diamond in dosimetric applications. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Exposure assessment of electromagnetic fields near electrosurgical unitsBIOELECTROMAGNETICS, Issue 7 2010Jonna Wilén Abstract Electrosurgical units (ESU) are widely used in medical health services. By applying sinusoidal or pulsed voltage in the frequency range of 0.3,5,MHz to the electrode tip, the desired mixture of coagulation and cutting are achieved. Due to the high voltage and current in the cable, strong electromagnetic fields appear near the ESU. The surgeon and others inside the operating room such as nurses, anesthesiologists, etc., will be highly exposed to these fields. The stray fields surrounding the ESU have previously been measured, but now a deeper analysis has been made of the curve shape of the field and the implication of this when assessing exposure from a commonly used ESU in accordance with the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. The result showed that for some of the modes, especially those using high-pulsed voltage with only a few sinusoidal periods, the E-field close to the cable could reach linear spatially averaged values of 20,kV/m compared to the 2.1,kV/m stated in ICNIRP guidelines. Assessing the E- and B-field from ESU is not straightforward since in this frequency range, both induced current density and specific absorption rate are restricted by the ICNIRP guidelines. Nevertheless, work needs to be done to reduce the stray fields from ESU. Bioelectromagnetics 31:513,518, 2010. © 2010 Wiley-Liss, Inc. [source] Bayesian Hierarchical Functional Data Analysis Via Contaminated Informative PriorsBIOMETRICS, Issue 3 2009Bruno Scarpa Summary A variety of flexible approaches have been proposed for functional data analysis, allowing both the mean curve and the distribution about the mean to be unknown. Such methods are most useful when there is limited prior information. Motivated by applications to modeling of temperature curves in the menstrual cycle, this article proposes a flexible approach for incorporating prior information in semiparametric Bayesian analyses of hierarchical functional data. The proposed approach is based on specifying the distribution of functions as a mixture of a parametric hierarchical model and a nonparametric contamination. The parametric component is chosen based on prior knowledge, while the contamination is characterized as a functional Dirichlet process. In the motivating application, the contamination component allows unanticipated curve shapes in unhealthy menstrual cycles. Methods are developed for posterior computation, and the approach is applied to data from a European fecundability study. [source] | ||||||||||