Home About us Contact
|
Home About us Contact | ||
|
|
||
Various Distances (various + distance)
Selected AbstractsComputer-generated null models as an approach to detect perceptual range in mark,re-sight studies , an example with grasshoppersECOLOGICAL ENTOMOLOGY, Issue 2 2005Silke Hein Abstract., 1. Dispersal and habitat detection are key factors for the colonisation of habitat fragments in heterogeneous landscapes. The ability to recognise a habitat from a certain distance should increase the survival chances of a dispersing individual; however, due to methodological problems there is little information on the perceptual range of most species. 2. In a field experiment, 44 individually marked grasshoppers of the species Oedipoda caerulescens (Orthoptera: Acrididae: Locustinae) were released into an unfamiliar, hostile environment at various distances from a patch of preferred habitat. 3. Whether individuals reached the habitat or not was measured, as well as the daily movement distances. The number of individuals that reached the habitat was tested against computer-generated predictions based on different underlying rules for the movement behaviour of individuals but not accounting for the ability to detect habitat from distance. 4. On the first day a significantly higher proportion of grasshoppers arrived in the habitat than predicted by any of the null models. 5. It was concluded that individuals of O. caerulescens are able to detect their preferred habitat from a distance. 6. Edge permeability was very low as none of the individuals left the habitat once they had reached it. 7. Additional analyses showed that individuals changed movement behaviour from a directed walk with great daily distances in unsuitable habitat to a walk with significantly shorter daily distances within the preferred habitat. 8. The problems that arose in the field experiment are discussed and recommendations are given for further studies. [source] Influence of needle tip distance on barrier discharge and ozone generation for multiple needle-and-plane electrode configurationELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 7 2010Hideki Ueno Abstract The relationship between the barrier discharge characteristics and ozone generation on application of an AC voltage in a triple needle-plane configuration has been investigated for various distances among the triple needle tips (d=0 to 7.0 mm) with a constant distance between the needle tip and the plane (g=3.0 mm) in dry air. The characteristics of the barrier discharge and ozone generation depend on the needle tip distance. It is considered that the influence is caused by the presence of space charge and accumulated charge, as suggested by discharge images taken by a still camera and a CCD camera. The ozone generation efficiency is also estimated from the power consumption and the ozone concentration. It is found that when the distance among the triple needle tips is small, the above influence is strengthened. In this case, the ozone generation efficiency is improved. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(7): 32,41, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10289 [source] Characterization of nickel-resistant bacteria isolated from serpentine soilENVIRONMENTAL MICROBIOLOGY, Issue 11 2001A. Mengoni In the present study, heterotrophic nickel-resistant bacteria were isolated and characterized from three different serpentine outcrops in central Italy populated by the nickel-hyperaccumulating plant Alyssum bertolonii. Bacteria were isolated from the rhizosphere of the plant and from soil portions at various distances from the plant. The proportion of nickel-resistant cfu was higher in proximity to the plant than in free soil. A total of 138 isolates was collected and grouped into 47 different operational taxonomic units (OTUs) by means of amplified ribosomal DNA restriction analysis (ARDRA) and into 25 heavy-metal resistant phenotypes. The phylogenetic position of strains belonging to 20 OTUs, representing more than the 70% of the total isolates, was determined by 16S rDNA sequencing. These analyses showed that the most represented genera in all three different outcrops were Pseudomonas and Streptomyces. Pseudomonas strains were found to be predominant in the plant rhizosphere, whereas Streptomyces strains were mainly present in the soil. [source] Wavefront healing: a banana,doughnut perspectiveGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2001S.-H. Hung SUMMARY Wavefront healing is a ubiquitous diffraction phenomenon that affects cross-correlation traveltime measurements, whenever the scale of the 3-D variations in wave speed is comparable to the characteristic wavelength of the waves. We conduct a theoretical and numerical analysis of this finite-frequency phenomenon, using a 3-D pseudospectral code to compute and measure synthetic pressure-response waveforms and ,ground truth' cross-correlation traveltimes at various distances behind a smooth, spherical anomaly in an otherwise homogeneous acoustic medium. Wavefront healing is ignored in traveltime tomographic inversions based upon linearized geometrical ray theory, in as much as it is strictly an infinite-frequency approximation. In contrast, a 3-D banana,doughnut Fréchet kernel does account for wavefront healing because it is cored by a tubular region of negligible traveltime sensitivity along the source,receiver geometrical ray. The cross-path width of the 3-D kernel varies as the square root of the wavelength , times the source,receiver distance L, so that as a wave propagates, an anomaly at a fixed location finds itself increasingly able to ,hide' within the growing doughnut ,hole'. The results of our numerical investigations indicate that banana,doughnut traveltime predictions are generally in excellent agreement with measured ground truth traveltimes over a wide range of propagation distances and anomaly dimensions and magnitudes. Linearized ray theory is, on the other hand, only valid for large 3-D anomalies that are smooth on the kernel width scale ,(, L). In detail, there is an asymmetry in the wavefront healing behaviour behind a fast and slow anomaly that cannot be adequately modelled by any theory that posits a linear relationship between the measured traveltime shift and the wave-speed perturbation. [source] Internal wave computations using the ghost fluid method on unstructured gridsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2005Sangmook Shin Abstract Two-layer incompressible flows are analysed using the ghost fluid method on unstructured grids. Discontinuities in dynamic pressure along interfaces are captured in one cell without oscillations. Because of data reconstructions based on gradients, the ghost fluid method can be adopted without additional storages for the ghost nodes at the expense of modification in gradient calculations due to the discontinuity. The code is validated through comparisons with experimental and other numerical results. Good agreements are achieved for internal waves generated by a body moving at transcritical speeds including a case where upstream solitary internal waves propagate. The developed code is applied to analyse internal waves generated by a NACA0012 section moving near interfaces. Variations of the lift acting on the body and configurations of the interfaces are compared for various distances between the wing and the interface. The effects of the interface are compared with the effects of a solid wall. Copyright © 2004 John Wiley & Sons, Ltd. [source] Fluorescence and coloration of grey hairINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 5 2009S. Daly Synopsis Grey hair samples were collected from 11 individuals and separated into un-pigmented and pigmented fibres (International Hair Importers). Fluorescence measurements were obtained by using a double-grating fluorescence spectrophotometer and a bifurcated fibre optics accessory to measure the spectra directly from the surface of hair at various distances from the fibre root. Colour measurements were carried out by using a Hunter colorimeter. The fluorescence spectra of un-pigmented hair obtained by the excitation at 290 nm show a peak at 356 nm [tryptophan (Trp)], and multi-peak emissions in the range from 395 to 500 nm. A significant variation in the Trp emission intensity at 356 nm vs. the intensity of emission in the 395,500 nm range was observed for hair collected from various individuals with yellow coloured hair producing stronger relative emission in 395,500 nm range. Quantitative measurements of coloration and the calculation of the Yellowness Index (YI) showed linear correlation between YI and the ratio of fluorescence intensities I440/I356 The spectra obtained by excitation at 320 nm showed the emission peaks at 395 nm (unidentified), 420 nm (N -formylkynurenine), 460 nm (kynurenine), and 495 nm (3-hydroxykynurenine), which are the products of oxidative or metabolic conversion of tryptophan. Un-pigmented, yellow hair showed a build-up of the fluorescence band corresponding to 3-hydroxykynurenine at 495 nm. The data also showed the fluorescence quenching effect of melanin resulting in the lowering of the fluorescence intensity of pigmented hair. The spectra obtained at various positions along the fibres demonstrated gradual photo-decomposition of hair chromophores during their lifetimes. This was indicated by a decrease of Trp fluorescence intensity, which was relatively fast (8·10,4,1.5·10,3 [day,1] as calculated for hair obtained from various individuals) for un-pigmented hair and slower for pigmented hair. A decrease in Trp emission was accompanied by an increase in the yellow coloration toward the ends of un-pigmented fibres. Resume Des échantillons de cheveux gris ont été collectés chez onze personnes et triés entre fibres non pigmentés et fibres pigmentés (International Hair Importers). Les mesures de fluorescence ont été réalisées à l'aide d'un spectrophotomètre de fluorescence double grille et d'un accessoire constitué d'une fibre optique bifurquée. Ce dispositif permet la mesure du spectre directement depuis la surface d'un cheveu à diverses distances de sa racine. Les mesures de couleur ont été réalisées à l'aide d'un colorimètre HUNTER. Le spectre de fluorescence d'un cheveu non pigmenté obtenu par excitation à 290 nm montre un pic à 356 nm (tryptophane : Trp) et des émissions multi pics dans l'intervalle 395 à 500 nm. On observe une variation significative de l'intensité du Trp à 356 nm par rapport à l'intensité d'émission dans l'intervalle 395,500 nm sur les cheveux prélevés sur diverses personnes, les cheveux colorés en jaune produisant une émission relative plus forte dans l'intervalle 395,500 nm. Les mesures quantitatives de la couleur et le calcul de l'indice de jaunissement (YI) montrent une corrélation linéaire entre YI et le rapport des intensités de fluorescence I 440/I356. Le spectre obtenu par excitation à 320 nm montre des pics d'émission à 395 nm (non identifiés), 420 nm (N-formylkynurenine), 460 nm (kynurenine), 495 nm (3-hydroxy kinurenine) propres aux produits d'oxydation ou de conversion métabolique du Tryptophane. Les cheveux jaunes non pigmentés présentent une saturation de la bande de fluorescence correspondant à la 3-hydroxykynurenine à 495 nm. Ces données montrent également l'effet de quenching de la mélanine entraînant un affaiblissement de l'intensité de la fluorescence des cheveux pigmentés. Le spectre obtenu en divers endroits le long des fibres indique une photodécomposition graduelle des chromophores des cheveux durant leur temps de vie. Ceci se traduit par une diminution de l'intensité de fluorescence du Trp qui est relativement rapide pour les cheveux non pigmentés (8,10,4,1,5,10,3 [jour , 1], conformément aux calculs effectués sur des cheveux prélevés sur différents individus) et par une diminution plus lente pour les cheveux pigmentés. Une diminution de l'émission du Trp s'accompagne d'une augmentation de la coloration jaune de l'extrémité des cheveux, détectable sur des cheveux non pigmentés. [source] Performance of a confocal multilayer X-ray opticJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2002J. Kusz In recent years, several companies have developed the technique of arranging two multilayer mirrors in confocal optics for monochromatizing X-rays. In this study, a focusing device of Osmic Inc., with a source-to-focus distance of 1005,mm, has been used. The goal was to measure the homogeneity of the beam, the cross section at various distances from the focus and the efficiency of the optic when it is operated with vacuum and with air in the beam path. A small crystal sphere set at various distances is used to compare the intensities and the widths of reflections with those of a flat graphite monochromator. In a standard diffraction experiment (crystal size 0.25,mm), the gain factor with respect to graphite is roughly ten at a position where the beam plateau is 0.5,mm. The suppression of the Cu K, radiation and of higher harmonics of K, is very good. [source] Fusarium eumartii Growth in Resistant and Susceptible Oak SpeciesJOURNAL OF PHYTOPATHOLOGY, Issue 9 2001A. Ragazzi Fusarium eumartii is a fungus associated with declining Quercus robur, in which it is found in the vessels. The response of oak species to infection is known to vary: Q. robur is susceptible, but Quercus cerris and Quercus pubescens are resistant. An experiment was carried out in 1996 and repeated in 1997, to examine how F. eumartii colonization differed in oak species that were susceptible or resistant to the fungus by counting the number of vessels with mycelium at various distances from the inoculation site in infected seedlings and by determining the amount of viable fungus in infected tissue. Infected vessels with mycelium were counted on sections (10 ,m thick) cut at 0, 2, 4, 6, 8 and 10 cm from the inoculation site on 1-year-old inoculated seedlings as well as on sections cut every 2 cm to the seedling tip. The amount of viable fungus was determined by counting the colony forming units (CFUs) in stem segments from the same seedlings. Quercus robur seedlings had the greatest number of infected vessels and the greatest number of CFUs. Forty days after inoculation, the extent of vertical fungal spread was 28.12 cm in Q. robur, 3.15 cm in Q. cerris and 3.00 cm in Q. pubescens. The greatest number of CFUs was found in Q. robur at day 5 after inoculation. Analysis of variance confirmed the results. [source] Blood Flow in Snake Infrared Organs: Response-Induced Changes in Individual VesselsMICROCIRCULATION, Issue 2 2007RICHARD C. GORIS ABSTRACT Objective: In the past the microkinetics of blood flow in the infrared pit organs of pit vipers has been studied with Doppler flowmetry using various infrared stimuli such as a human hand or soldering iron at various distances, lasers of various wavelengths, etc. Quick-acting variations in blood flow were recorded, and interpreted as a cooling mechanism for avoiding afterimage in the infrared receptors. However, the Doppler measurements provided only the summation of blood flow in a number of vessels covered by the sensing probe, but did not give data on flow in individual vessels. Methods: In the present work the authors introduced into the bloodstream of Gloydius and Trimeresurus pit vipers fluorescent microspheres labeled with fluorescein isothiocyanate (FITC) contained in a solution of FITC-dextran in physiological saline. They observed the passage of the microspheres through individual pit organ vessels with a fluorescent microscope to which was attached a high-speed video camera and image intensifier. Output of the camera was recorded before, during, and after stimulus with a 810-nm diode laser. Recording was done at 250 frames/s on high-speed video apparatus and downloaded to a hard disk. Disk files were loaded into proprietary software and particles were tracked and average velocities calculated. The data were then tested for significance by ANOVA with post hoc tests. Results: A significant (p < .05) increase in blood velocity was found at the focal point of the stimulus laser, but not anywhere removed from this point. Proximal severing of the pit sensory nerves caused degeneration of the pit receptor terminals and abolished stimulus-induced blood flow changes, but did not affect normal blood flow. Conclusions: The authors conclude that the receptors themselves are directly and locally controlling the smooth muscle elements of the blood vessels, in response to heating of the receptors by infrared radiation. They speculate that the heavy vascularization constitutes a cooling system for the radiation-encoding receptors, and further that the agent of control may be a volatile neuromediator such as nitric oxide. [source] The terminal nerve and its relation with extrabulbar "olfactory" projections: Lessons from lampreys and lungfishesMICROSCOPY RESEARCH AND TECHNIQUE, Issue 1-2 2004Christopher S. Von BartheldArticle first published online: 29 NOV 200 Abstract The definition of the terminal nerve has led to considerable confusion and controversy. This review analyzes the current state of knowledge as well as diverging opinions about the existence, components, and definition of terminal nerves or their components, with emphasis on lampreys and lungfishes. I will argue that the historical terminology regarding this cranial nerve embraces a definition of a terminal nerve that is compatible with its existence in all vertebrate species. This review further summarizes classical and more recent anatomical, developmental, neurochemical, and molecular evidence suggesting that a multitude of terminalis cell types, not only those expressing gonadotropin-releasing hormone, migrate various distances into the forebrain. This results in numerous morphological and neurochemically distinct phenotypes of neurons, with a continuum spanning from olfactory receptor-like neurons in the olfactory epithelium to typical large ganglion cells that accompany the classical olfactory projections. These cell bodies may lose their peripheral connections with the olfactory epithelium, and their central projections or cell bodies may enter the forebrain at several locations. Since "olfactory" marker proteins can be expressed in bona fide nervus terminalis cells, so-called extrabulbar "olfactory" projections may be a collection of disguised nervus terminalis components. If we do not allow this pleiomorphic collection of nerves to be considered within a terminal nerve framework, then the only alternative is to invent a highly species- and stage-specific, and, ultimately, thoroughly confusing nomenclature for neurons and nerve fibers that associate with the olfactory nerve and forebrain. Microsc. Res. Tech. 65:13,24, 2004. © 2004 Wiley-Liss, Inc. [source] Xylem Flow and its Driving Forces in a Tropical Liana: Concomitant Flow-Sensitive NMR Imaging and Pressure Probe MeasurementsPLANT BIOLOGY, Issue 6 2000N. Wistuba Abstract: Flow-sensitive NMR imaging and pressure probe techniques were used for measuring xylem water flow and its driving forces (i.e., xylem pressure as well as cell turgor and osmotic pressure gradients) in a tropical liana, Epipremnum aureum. Selection of tall specimens allowed continuous and simultaneous measurements of all parameters at various distances from the root under diurnally changing environmental conditions. Well hydrated plants exhibited exactly linearly correlated dynamic changes in xylem tension and flow velocity. Concomitant multiple-probe insertions along the plant shoot revealed xylem and turgor pressure gradients with changing magnitudes due to environmental changes and plant orientation (upright, apex-down, or horizontal). The data suggest that in upright and - to a lesser extent - in horizontal plants the transpirational water loss by the cells towards the apex during the day is not fully compensated by water uptake through the night. Thus, longitudinal cellular osmotic pressure gradients exist. Due to the tight hydraulic coupling of the xylem and the tissue cells these gradients represent (besides the transpiration-induced tension in the xylem) an additional tension component for anti-gravitational water movement from the roots through the vessels to the apex. [source] Improvement of the Accuracy in the Optical Hematocrit Measurement by Optimizing Mean Optical Path LengthARTIFICIAL ORGANS, Issue 9 2009Shiori Oshima Abstract Optical techniques have been developed to acquire blood information (e.g., hematocrit [Hct], saturation of oxygen, thrombus) noninvasively and continuously in an artificial heart. For the practical use of an optical Hct measurement, Twersky's theory has been shown to be useful and have a good agreement in forward-scattered measurements. However, it was not applied to backward-scattered measurements, which can provide the measurement with a less demanding spatial requirement. Additionally, optimal measurement for accuracy is not well examined. Therefore, we developed an accurate Hct measurement in an artificial heart using current optical devices. To this end, we focused on optimizing an emitter,detector distance to provide a maximum optical path length. We attached optical emitter and detector fibers on Tygon tubing at various distances to measure forward- and backward-scattered light. Fresh bovine blood (Hct: 30,50%) was circulated in the tubing by a nonpulsatile artificial heart. We calculated the optical path length at various emitter,detector distances by fitting the measured optical outputs and the reference Hcts to Twersky's theory. Then, we performed Hct measurements. As a result, Twersky's theory is applicable not only to forward- but also to backward-scattered measurements in the physiogical Hct range. In both forward- and backward-scattered measurements, calculated optical path lengths become maximum at the same emitter,detector distance. The accuracy of Hct measurement is improved two to three times with the emitter,detector distance compared with other distances. The mean error is less than 1 Hct%. This result shows that an accurate Hct measurement is realized by selecting the optimal emitter,detector distance, which provides maximum optical path length defined by Twersky's theory. Our study provides a framework for the practical and less restrictive application of the optical Hct measurement to patients with an artificial heart. [source] How Infants Learn About the Visual WorldCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 7 2010Scott P. Johnson Abstract The visual world of adults consists of objects at various distances, partly occluding one another, substantial and stable across space and time. The visual world of young infants, in contrast, is often fragmented and unstable, consisting not of coherent objects but rather surfaces that move in unpredictable ways. Evidence from computational modeling and from experiments with human infants highlights three kinds of learning that contribute to infants' knowledge of the visual world: learning via association, learning via active assembly, and learning via visual-manual exploration. Infants acquire knowledge by observing objects move in and out of sight, forming associations of these different views. In addition, the infant's own self-produced behavior,oculomotor patterns and manual experience, in particular,is an important means by which infants discover and construct their visual world. [source] | ||||||||||||||||