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  • Springer  (29)
  • 1995-1999  (29)
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  • 1
    Electronic Resource
    Electronic Resource
    An Evaluation on H/V Ratio vs. Spectral Ratio for Site-response Estimation Using the 1994 Northridge Earthquake Sequences (1999)
    Springer
    Pure and applied geophysics 156 (1999), S. 631-649 
    Details
    ISSN: 1420-9136
    Keywords: Key Words: H/V ratio, spectral ratio, site response, microtremor, resonant frequency, amplification.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —The applicability of the single-station H/V method, based on the spectral ratio between the horizontal and the vertical components of strong ground motions, is examined for site-response estimation using the high quality data from the 1994 Northridge earthquake sequence. Instead of using Rayleigh-wave data from microtremors, the large amplitude-wave part of the S-wave data is used and based on the 1994 Northridge mainshock and aftershock recordings. We have found that upon averaging over a number of recordings for a given station, the station site responses, derived both from the single-station H/V ratio and from the standard spectral ratio (with respect to a reference rock-site station) are sufficiently close for practical purposes. We therefore conclude that the H/V ratio can reasonably predict the resonant frequency and the amplification level of a site response, especially for sites in the neighborhood of the epicenters. In the absence of a reference rock-site station, the H/V ratio provides a practical alternative to the standard site-response estimation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000240050316
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  • 2
    Electronic Resource
    Electronic Resource
    Evidence for coupling between Na+ pump activity and TEA-sensitive K+ currents in Xenopus laevis oocytes (1995)
    Springer
    The journal of membrane biology 143 (1995), S. 29-35 
    Details
    ISSN: 1432-1424
    Keywords: Na+-K+-ATPase ; Electrophysiology ; K+ channel ; Tetraethylammonium ; Conductance regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Using the two-microelectrode voltage clamp technique in Xenopus laevis oocytes, we estimated Na+-K+-ATPase activity from the dihydroouabain-sensitive current (I DHO) in the presence of increasing concentrations of tetraethylammonium (TEA+; 0, 5, 10, 20, 40 mm), a well-known blocker of K+ channels. The effects of TEA+ on the total oocyte currents could be separated into two distinct parts: generation of a nonsaturating inward current increasing with negative membrane potentials (V M) and a saturable inhibitory component affecting an outward current easily detectable at positive V M. The nonsaturating component appears to be a barium-sensitive electrodiffusion of TEA+ which can be described by the Goldman-Hodgkin-Katz equation, while the saturating component is consistent with the expected blocking effect of TEA+ on K+ channels. Interestingly, this latter component disappears when the Na+-K+-ATPase is inhibited by 10 μm DHO. Conversely, TEA+ inhibits a component of I DHO with a k d of 25±4 mm at +50 mV. As the TEA+-sensitive current present in I DHO reversed at −75 mV, we hypothesized that it could come from an inhibition of K+ channels whose activity varies in parallel with the Na+-K+-ATPase activity. Supporting this hypothesis, the inward portion of this TEA+-sensitive current can be completely abolished by the addition of 1 mm Ba2+ to the bath. This study suggests that, in X. laevis oocytes, a close link exists between the Na-K-ATPase activity and TEA+-sensitive K+ currents and indicates that, in the absence of effective K+ channel inhibitors, I DHO does not exclusively represent the Na+-K+-ATPase-generated current.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232521
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  • 3
    Electronic Resource
    Electronic Resource
    Solid/free-surface juncture boundary layer and wake (1998)
    Springer
    Experiments in fluids 25 (1998), S. 283-297 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  The Reynolds-averaged flow for a solid/free-surface juncture boundary layer and wake is documented. The three mean-velocity components and five of the Reynolds stresses are measured for a surface-piercing flat plate in a towing tank using a laser-Doppler velocimeter system for both boundary-layer and wake planes in regions close to the free surface. The experimental method is described, including the foil-plate model, laser-Doppler velocimeter system, conditions, and uncertainty analysis. The underlying flow data is in excellent agreement with benchmark data. Inner (near the plate and wake centerplane and below the free surface) and outer (near the free surface) regions of high streamwise vorticity of opposite sign are observed, which transport, respectively, high mean velocity and low turbulence from the outer to the inner and low mean velocity and high turbulence from the inner to the outer portions of the boundary layer and wake. For the wake, the inner region of vorticity is relatively weak. The physical mechanism for the streamwise vorticity is analyzed with regard to the Reynolds-averaged streamwise vorticity equation. The anisotropy of the crossplane normal Reynolds stresses closely correlates with the vorticity and, additionally, indicates similarity, i.e., its nature is such that it only depends on the proximity to the plate and free surface boundaries or wake centerplane symmetry plane. Free-surface effects on the Reynolds stresses are analyzed with regard to the behavior close to the free surface of the turbulent kinetic energy and the normal components of the anisotropy tensor and the anisotropy invariants. Close to the free surface, the turbulent kinetic energy is nearly constant and increases for the inner and outer portions, respectively, of the boundary layer and wake and the normal components of the anisotropy tensor and the anisotropy invariants roughly correspond to the limiting values for two-component turbulence. The similarities and differences between the present results and analysis with those from related studies are discussed. The data and analysis should have practical application with regard to the development of turbulence models for computational fluid dynamics methods for the Reynolds-averaged Navier–Stokes equations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003480050232
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  • 4
    Electronic Resource
    Electronic Resource
    Component Specifications for Robotics Integration (1999)
    Springer
    Autonomous robots 6 (1999), S. 247-264 
    Details
    ISSN: 1573-7527
    Keywords: software components ; software reuse ; frameworks ; intelligent systems ; software architectures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Robotics researchers have been unable to capitalize easily on existing software components to speed up their development efforts and maximize their system's capabilities. A component-based approach for building the software for robotics systems can provide reuse and sharing abilities to the research community. The software engineering community has been studying reuse techniques for three decades. We present several results from those efforts that are applicable to the robotics software integration problem. We describe how to specify a software component so that a potential user may understand its capabilities and facilitate its application to his or her system. At the National Institute of Standards and Technology, we have developed a three-stage, component-specification approach. We illustrate this approach for a component that is relevant to robotics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008980211618
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  • 5
    Electronic Resource
    Electronic Resource
    Objective measures of the information density of satellite data (1996)
    Springer
    Meteorology and atmospheric physics 60 (1996), S. 105-117 
    Details
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary We propose and objective method whereby the density of Shannon's “information” associated with the retrieval of a profile of atmospheric variables from satellite-derived infrared radiance measurements may be estimated. The technique is a natural extension of one we previously proposed to estimate the effective data density in a profile. We test the method in a comparison of simulated satellite instruments to show that the method does indeed provide an objective summary of the spatial distribution of each instrument's information content. We propose that further extensions of the method be developed to include other more traditional data sources in a fully three-dimensional scheme. We also note that analogous and compatible methods may be used to diagnose the information content of meteorological analysis and forecast fields relative to the information contained in the covariance, at the appropriate season, of the corresponding climate fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01029788
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  • 6
    Electronic Resource
    Electronic Resource
    Normal Wedge Indentation in Rocks with Lateral Confinement (1998)
    Springer
    Rock mechanics and rock engineering 31 (1998), S. 81-94 
    Details
    ISSN: 1434-453X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Summary The paper reports results of a numerical analysis of the wedge indentation problem. The main objective of this research is to investigate the influence of the lateral confining stress on the development of the plastic zone under the indenter and on the initiation of tensile fractures. Numerical analysis indicates that the location of maximum tensile stress (interpreted as the point of crack initiation) moves away from the indentation axis as the lateral confinement increases. It is found that a small increase in the confining stress from zero induces a large increase in the inclination of this point on the indentation axis. However, the confinement does not reduce significantly the maximum tensile stress and it hardly influences the indentation pressure. These numerical results shed some light on the mechanism of formation of lateral or sub-horizontal tensile cracks observed in the indentation experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s006030050010
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  • 7
    Electronic Resource
    Electronic Resource
    An extension of digital PIV-processing to double-exposed images (1998)
    Springer
    Experiments in fluids 24 (1998), S. 364-372 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  In this paper digital processing techniques for PIV (Partical Image Velocimetry) using double-exposed particle images have been studied. It has been found that a pattern matching technique is significantly superior to the traditional autocorrelation method in the case that a large particle displacement between the double exposures is present on the image. In PIV using double-exposed images, the image shifting technique is usually used to solve the directional ambiguity problem. The performance of PIV using autocorrelation technique is dependent on the flow speed and the amount of image shift applied. This dependence, for example, causes a difficulty of autocorrelation in flows close to a solid boundary. The present study shows that a pattern matching technique eliminates such a difficulty. At the same signal-to-noise ratio, the pattern matching techndique has a better spatial resolution than that of autocorrelation. In concert with the pattern matching technique, PID (Particle Image Distortion) can be applied to double-exposed images, further improving the reliability and accuracy of velocity estimates of PIV in the presence of large velocity gradients. Generally speaking, PIP-matching and PID extend the validity of PIV using double-exposed images. The total processing time required by the PIV using the pattern matching technique and one PID iteration is of the same order as that required by the PIV using autocorrelation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003480050184
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  • 8
    Electronic Resource
    Electronic Resource
    A DPIV study of a starting flow downstream of a backward-facing step (1997)
    Springer
    Experiments in fluids 23 (1997), S. 395-404 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  In this paper an experimental investigation of a starting water flow downstream of a backward-facing step is described. The Reynolds number of the asymptotic steady flow is Re≈4300 based on the step height of s=2 cm and the free stream velocity of U=21.4 cm/s. Velocity measurements were performed with video-based DPIV (Digital Particle Image Velocimetry) at a sampling frequency of 25 Hz. The main purpose of this study is to reveal the temporal development of global structures which could not be analyzed with single-point probes. It was found that at initialization of the flow a regular vorticity street is formed, which collapses at a normalized time t * =U t/s≈17 due to vorticity interactions. After this the flow is dominated by complicated vorticity roll-up and shedding dynamics in the recirculation region. The starting phase is terminated for t * 〉40. Prior to the collapse of the vorticity street values of 9 times the steady state asymptotic wall normal stress and of twice the steady state negative wall shear stress were observed. The early increasing slope of the reattachment length is constant over a time of approximately t * =8. The collapse of the vorticity street and the vorticity interactions thereafter cause fluctuations both in the velocity in the free shear layer and in the reattachment length. The fully developed flow has a dominant frequency corresponding to a Strouhal number St=fs/U≈0.04.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003480050127
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  • 9
    Electronic Resource
    Electronic Resource
    Cytokeratin-19 associated with apoptosis and chemosensitivity in human cervical cancer cells (1997)
    Springer
    Apoptosis 2 (1997), S. 101-105 
    Details
    ISSN: 1573-675X
    Keywords: Apoptosis ; cytokeratin ; drug resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Cytokeratins are one group of intermediate filament proteins responsible for the integrity of cell structure, and have been recently reported to play a role in conferring a drug resistance phenotype. MAb Cx-99 is a monoclonal antibody exhibiting the specificity toward its corresponding antigen which was recently identified as the cytokeratin-19 protein. In the present study, we found that the level of cytokeratin-19 in cervical cancer cells could be decreased by incubation of cancer cells with MAb Cx-99. The reduction of cytokeratin-19 level had a killing effect on cervical carcinoma SIHA and HeLa S3 cell lines. The DNA ladder pattern, convoluted nuclei and blebbing morphology were observed with these cells after exposure to MAb Cx-99 for 72 h, suggesting that the cytotoxic mechanism of reduced cytokeratin-19 was mediated by induction of apoptosis. Moreover, the MAb Cx-99 treatment could increase the cytotoxicities of cancer chemotherapeutic agents such as cisplatin and vinblastine to both cervical carcinoma cell lines. The LD80 values were at least 15-fold reduced when cancer cells were treated with cisplatin or vinblastine in the presence of MAb Cx-99. These results suggest that the functional role of cytokeratin-19 was associated with the apoptosis prevention and drug resistance of cervical cancer cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026448027870
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  • 10
    Electronic Resource
    Electronic Resource
    High-performance capillary electrophoretic analysis of synthetic food colorants (1998)
    Springer
    Chromatographia 47 (1998), S. 249-256 
    Details
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Cyclodextrin mobile phase additives ; Synthetic food colorants ; Selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high-performance capillary electrophoresis method with diode-array detection has been developed for analysis of synthetic food colorants. The influence of buffer composition on the separation of the food colorants was examined, as were the effects of α-, β- and γ-c-yclodextrins on analyte migration behavior. Eight food colorants were completely separated within 10 min using pH 9.5 borax—NaOH buffer containing 5 mM β-cyclodextrin. Experimental results indicate that the relative standard deviations of analyte migration times were〈0.88% under the optimized separation condition. Correlation coefficients of the linear calibration plots of the analytes exceeded 0.998. The method was suitable for determination of the quantities of synthetic food colorantsi in ice cream bars and fruit soda drinks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466528
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