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  • 1
    Digitale Medien
    Digitale Medien
    The disturbance of drilling mud on rock formation and a method for error elimination on acoustic log curves (2003)
    PO Box 1354, 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Publishing Ltd
    Geophysical prospecting 51 (2003), S. 0 
    Details
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: Errors in acoustic logs have a significant influence on the assessment of formations, the description of oil deposits and modelling using synthetic seismograms. The elimination of these errors is a problem that many researchers have been trying to solve for many years. We derive theoretical formulae for calculating the radial depth of investigation of acoustic logging, and analyse the relationship between the error in acoustic interval transit time and the altered zone thickness. We explain in detail how mud affects the acoustic interval transit time. We also describe the variation of altered zone thickness with time and a method for calculating the altered zone thickness. Finally, we present a set of new methods that can be directly applied to correct the disturbing influence on acoustic curves. Our results are obtained based on the fact that acoustic velocities in the altered zone show a small lateral variation. Examples are given of analysing the acoustic log data, which are collected from a BS well at three different times. This paper is significant both for selection of the acoustic logging device with proper transmitter-to-receiver distance (spacing) and improvement of the device.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/J.1365-2478.2003.00387.X
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  • 2
    Digitale Medien
    Digitale Medien
    Seismic modelling study of a subglacial lake (2003)
    PO Box 1354, 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Publishing Ltd
    Geophysical prospecting 51 (2003), S. 0 
    Details
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: We characterize the seismic response of Lake Vostok, an Antarctic subglacial lake located at nearly 4 km depth below the ice sheet. This study is relevant for the determination of the location and morphology of subglacial lakes. The characterization requires the design of a methodology based on rock physics and numerical modelling of wave propagation. The methodology involves rock-physics models of the shallow layer (firn), the ice sheet and the lake sediments, numerical simulation of synthetic seismograms, ray tracing, τ–p transforms, and AVA analysis, based on the theoretical reflection coefficients. The modelled reflection seismograms show a set of straight events (refractions through the firn and top-ice layer) and the two reflection events associated with the top and bottom of the lake. Theoretical AVA analysis of these reflections indicates that, at near offsets, the PP-wave anomaly is negative for the ice/water interface and constant for the water/sediment interface. This behaviour is shown by AVA analysis of the synthetic data set. This study shows that subglacial lakes can be identified by using seismic methods. Moreover, the methodology provides a tool for designing suitable seismic surveys.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2478.2003.00388.x
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  • 3
    Digitale Medien
    Digitale Medien
    Fracture characterization from walkaround VSPs (2003)
    PO Box 1354, 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Publishing Ltd
    Geophysical prospecting 51 (2003), S. 0 
    Details
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: A walkaround VSP is a novel acquisition geometry comprising multiple sources azimuthally distributed around a fixed multi-component receiver at approximately the same offset. Such a configuration allows the robust measurement of fracture-induced anisotropy by the analysis of certain seismic attributes with respect to azimuth.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2478.2003.00391.x
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  • 4
    Digitale Medien
    Digitale Medien
    Petrophysical inversion of AVA data (2003)
    PO Box 1354, 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Publishing Ltd
    Geophysical prospecting 51 (2003), S. 0 
    Details
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: We investigate the interactions between the elastic parameters, VP, VS and density, estimated by non-linear inversion of AVA data, and the petrophysical parameters, depth (pressure), porosity, clay content and fluid saturation, of an actual gas-bearing reservoir. In particular, we study how the ambiguous solutions derived from the non-uniqueness of the seismic inversion affect the estimates of relevant rock properties. It results that the physically admissible values of the rock properties greatly reduce the range of possible seismic solutions and this range contains the actual values given by the well. By means of a statistical inversion, we analyse how approximate a priori knowledge of the petrophysical properties and of their relationships with the seismic parameters can be of help in reducing the ambiguity of the inversion solutions and eventually in estimating the petrophysical properties of the specific target reservoir. This statistical inversion allows the determination of the most likely values of the sought rock properties along with their uncertainty ranges. The results show that the porosity is the best-resolved rock property, with its most likely value closely approaching the actual value found by the well, even when we insert somewhat erroneous a priori information. The hydrocarbon saturation is the second best-resolved parameter, but its most likely value does not match the well data. The depth of the target interface is the least-resolved parameter and its most likely value is strongly dependent on a priori information. Although no general conclusions can be drawn from the results of this exercise, we envisage that the proposed AVA–petrophysical inversion and its possible extensions may be of use in reservoir characterization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2478.2003.00389.x
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  • 5
    Digitale Medien
    Digitale Medien
    Joint AVO inversion, wavelet estimation and noise-level estimation using a spatially coupled hierarchical Bayesian model (2003)
    PO Box 1354, 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Publishing Ltd
    Geophysical prospecting 51 (2003), S. 0 
    Details
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: The main objective of the AVO inversion is to obtain posterior distributions for P-wave velocity, S-wave velocity and density from specified prior distributions, seismic data and well-log data. The inversion problem also involves estimation of a seismic wavelet and the seismic-noise level. The noise model is represented by a zero mean Gaussian distribution specified by a covariance matrix. A method for joint AVO inversion, wavelet estimation and estimation of the noise level is developed in a Bayesian framework. The stochastic model includes uncertainty of both the elastic parameters, the wavelet, and the seismic and well-log data. The posterior distribution is explored by Markov-chain Monte-Carlo simulation using the Gibbs' sampler algorithm. The inversion algorithm has been tested on a seismic line from the Heidrun Field with two wells located on the line. The use of a coloured seismic-noise model resulted in about 10% lower uncertainties for the P-wave velocity, S-wave velocity and density compared with a white-noise model. The uncertainty of the estimated wavelet is low. In the Heidrun example, the effect of including uncertainty of the wavelet and the noise level was marginal with respect to the AVO inversion results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2478.2003.00390.x
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  • 6
    Digitale Medien
    Digitale Medien
    Velocity and attenuation in partially saturated rocks: poroelastic numerical experiments (2003)
    PO Box 1354, 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Publishing Ltd
    Geophysical prospecting 51 (2003), S. 0 
    Details
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: We use a poroelastic modelling algorithm to compute numerical experiments on wave propagation in a rock sample with partial saturation using realistic fluid distribution patterns from tomography scans. Frequencies are in the range 10 to 500 kHz. The rock is a homogeneous isotropic sandstone partially filled with gas and water, which are defined by their characteristic values of viscosity, compressibility and density. We assume no mixing and that the two different pore-fills occupy different macroscopic regions. The von Kármán self-similar correlation function is used, employing different fractal parameters to model uniform and patchy fluid distributions, respectively, where effective saturation is varied in steps from full gas to full water saturation.Without resorting to additional matrix–fluid interaction mechanisms, we are able to reproduce the main features of the variation in wave velocity and attenuation with effective saturation and frequency, as those of published laboratory experiments. Furthermore, the behaviour of the attenuation peaks versus water saturation and frequency is similar to that of White's model. The conversion of primary P-wave energy into dissipating slow waves at the heterogeneities is shown to be the main mechanism for attenuating the primary wavefield. Fluid/gas patches are shown to affect attenuation more than equivalent patches in the permeability or solid-grain properties.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2478.2003.00393.x
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  • 7
    Digitale Medien
    Digitale Medien
    3D wavepath migration (2003)
    PO Box 1354, 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Publishing Ltd
    Geophysical prospecting 51 (2003), S. 0 
    Details
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: 3D Kirchhoff migration (KM) smears a trace's time sample along a quasi-ellipsoid in the model space. This is a costly and sometimes noisy process as reflection energy is smeared far away from the actual reflector position, introducing far-field migration artefacts. As a reduced form of 3D KM, 3D wavepath migration (WM) smears a picked reflection arrival to a small Fresnel zone portion centred about the specular reflection point, leading to fewer migration artefacts and reduced computation time. Both the traveltime and the angle of incidence are required by WM for locating the specular reflection point. Our results with 3D prestack synthetic data show that WM generates fewer migration artefacts and can sometimes define complex structure better than KM. Our results with 3D prestack field data show that WM can mostly suppress migration artefacts and can sometimes resolve reflection interfaces better than KM. The CPU comparison shows that, for both the synthetic and field data examples, WM can be more than an order of magnitude faster than KM. The limitation with 3D WM is that the angle of incidence calculation is sensitive to the recording geometry and the signal-to-noise (S/N) ratio, which can lead to blurred images.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2478.2003.00380.x
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  • 8
    Digitale Medien
    Digitale Medien
    Computations of secondary potential for 3D DC resistivity modelling using an incomplete Choleski conjugate-gradient method (2003)
    PO Box 1354, 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Publishing Ltd
    Geophysical prospecting 51 (2003), S. 0 
    Details
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: An accurate and efficient 3D finite-difference (FD) forward algorithm for DC resistivity modelling is developed. In general, the most time-consuming part of FD calculation is to solve large sets of linear equations: Ax=b, where A is a large sparse band symmetric matrix. The direct method using complete Choleski decomposition is quite slow and requires much more computer storage. We have introduced a row-indexed sparse storage mode to store the coefficient matrix A and an incomplete Choleski conjugate-gradient (ICCG) method to solve the large linear systems. By taking advantage of the matrix symmetry and sparsity, the ICCG method converges much more quickly and requires much less computer storage. It takes approximately 15 s on a 533 MHz Pentium computer for a grid with 46 020 nodes, which is approximately 700 times faster than the direct method and 2.5 times faster than the symmetric successive over-relaxation (SSOR) conjugate-gradient method. Compared with 3D finite-element resistivity modelling with the improved ICCG solver, our algorithm is more efficient in terms of number of iterations and computer time. In addition, we solve for the secondary potential in 3D DC resistivity modelling by a simple manipulation of the FD equations. Two numerical examples of a two-layered model and a vertical contact show that the method can achieve much higher accuracy than solving for the total potential directly with the same grid nodes. In addition, a 3D cubic body is simulated, for which the dipole–dipole apparent resistivities agree well with the results obtained with the finite-element and integral-equation methods. In conclusion, the combination of several techniques provides a rapid and accurate 3D FD forward modelling method which is fundamental to 3D resistivity inversion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2478.2003.00392.x
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  • 9
    Digitale Medien
    Digitale Medien
    Use of VFSA for resolution, sensitivity and uncertainty analysis in 1D DC resistivity and IP inversion (2003)
    PO Box 1354, 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Publishing Ltd
    Geophysical prospecting 51 (2003), S. 0 
    Details
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: We present results from the resolution and sensitivity analysis of 1D DC resistivity and IP sounding data using a non-linear inversion. The inversion scheme uses a theoretically correct Metropolis–Gibbs' sampling technique and an approximate method using numerous models sampled by a global optimization algorithm called very fast simulated annealing (VFSA). VFSA has recently been found to be computationally efficient in several geophysical parameter estimation problems. Unlike conventional simulated annealing (SA), in VFSA the perturbations are generated from the model parameters according to a Cauchy-like distribution whose shape changes with each iteration. This results in an algorithm that converges much faster than a standard SA. In the course of finding the optimal solution, VFSA samples several models from the search space. All these models can be used to obtain estimates of uncertainty in the derived solution. This method makes no assumptions about the shape of an a posteriori probability density function in the model space. Here, we carry out a VFSA-based sensitivity analysis with several synthetic and field sounding data sets for resistivity and IP. The resolution capability of the VFSA algorithm as seen from the sensitivity analysis is satisfactory. The interpretation of VES and IP sounding data by VFSA, incorporating resolution, sensitivity and uncertainty of layer parameters, would generally be more useful than the conventional best-fit techniques.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2478.2003.00379.x
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  • 10
    Digitale Medien
    Digitale Medien
    Using a non-integer moment of the impulse response to estimate the half-space conductivity (2003)
    PO Box 1354, 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Publishing Ltd
    Geophysical prospecting 51 (2003), S. 0 
    Details
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: The nth-order moments of the electromagnetic impulse response are useful for interpreting electromagnetic data. We have derived an analytic expression for the half-order moment of a conductive half-space. By inverting this expression, the measured half-order moment can be used to estimate an apparent conductivity of the ground. The first-order moment can also be used to estimate the half-space conductivity. A sensitivity analysis indicates that for an airborne EM configuration, the half-order moment will be most sensitive to material in the top 26–48 m, while the first-order moment will be sensitive to deeper material (down to depths between 66 and 127 m).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2478.2003.00383.x
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  • 11
    Digitale Medien
    Digitale Medien
    The Wilson–Burg method of spectral factorization with application to helical filtering (2003)
    PO Box 1354, 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Publishing Ltd
    Geophysical prospecting 51 (2003), S. 0 
    Details
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: Spectral factorization is a computational procedure for constructing minimum-phase (stable inverse) filters required for recursive inverse filtering. We present a novel method of spectral factorization. The method iteratively constructs an approximation of the minimum-phase filter with the given autocorrelation by repeated forward and inverse filtering and rearranging of the terms. This procedure is especially efficient in the multidimensional case, where the inverse recursive filtering is enabled by the helix transform.To exemplify a practical application of the proposed method, we consider the problem of smooth two-dimensional data regularization. Splines in tension are smooth interpolation surfaces whose behaviour in unconstrained regions is controlled by the tension parameter. We show that such surfaces can be efficiently constructed with recursive filter preconditioning and we introduce a family of corresponding two-dimensional minimum-phase filters. The filters are created by spectral factorization on a helix.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2478.2003.00382.x
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  • 12
    Digitale Medien
    Digitale Medien
    Frequency-dependent anisotropy due to meso-scale fractures in the presence of equant porosity (2003)
    PO Box 1354, 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Publishing Ltd
    Geophysical prospecting 51 (2003), S. 0 
    Details
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: Fractured rock is often modelled under the assumption of perfect fluid pressure equalization between the fractures and equant porosity. This is consistent with laboratory estimates of the characteristic squirt-flow frequency. However, these laboratory measurements are carried out on rock samples which do not contain large fractures. We consider coupled fluid motion on two scales: the grain scale which controls behaviour in laboratory experiments and the fracture scale. Our approach reproduces generally accepted results in the low- and high-frequency limits. Even under the assumption of a high squirt-flow frequency, we find that frequency-dependent anisotropy can occur in the seismic frequency band when larger fractures are present. Shear-wave splitting becomes dependent on frequency, with the size of the fractures playing a controlling role in the relationship. Strong anisotropic attenuation can occur in the seismic frequency band. The magnitude of the frequency dependence is influenced strongly by the extent of equant porosity. With these results, it becomes possible in principle to distinguish between fracture- and microcrack-induced anisotropy, or more ambitiously to measure a characteristic fracture length from seismic data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2478.2003.00384.x
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  • 13
    Digitale Medien
    Digitale Medien
    Reflection and transmission responses of layered transversely isotropic viscoelastic media (2003)
    PO Box 1354, 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Publishing Ltd
    Geophysical prospecting 51 (2003), S. 0 
    Details
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: We consider a layered heterogeneous viscoelastic transversely isotropic medium with a vertical symmetry axis (a viscoelastic TIV medium) and parameters that depend on depth only. This takes into account intrinsic attenuation, anisotropy and thin layering. The seismic wavefield is decomposed into up- and downgoing waves scaled by the vertical energy flux. This scaling gives important symmetry relationships for both reflection and transmission (R/T) responses. For a stack of homogeneous layers, the exact reflection response can be computed in a numerically stable way by a simple layer-recursive algorithm. We derive exact plane-wave R/T coefficients and several linear and quadratic approximations between two viscoelastic TIV media, as functions of the real-valued horizontal slowness. The approximations are valid for pre- and post-critical values of horizontal slowness provided that the proper complex square roots are used when computing the vertical slowness. Numerical examples demonstrate that the quadratic approximations can be used for large differences in medium parameters, while the linear approximations can be used for small differences. For weak anisotropy it is sufficient to use an isotropic background medium, while for strong anisotropy it is necessary to use a weak TIV or TIV background medium. We also extend the O'Doherty–Anstey formula to the P- and SV-wave transmission responses of a stack of viscoelastic TIV layers, taking into account intrinsic attenuation, anisotropy and thin layering.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2478.2003.00381.x
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  • 14
    Digitale Medien
    Digitale Medien
    Traveltime computation for 3D anisotropic media by a finite-difference perturbation method (2003)
    PO Box 1354, 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Publishing Ltd
    Geophysical prospecting 51 (2003), S. 0 
    Details
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: The first-order perturbation theory is used for fast 3D computation of quasi-compressional (qP)-wave traveltimes in arbitrarily anisotropic media. For efficiency we implement the perturbation approach using a finite-difference (FD) eikonal solver. Traveltimes in the unperturbed reference medium are computed with an FD eikonal solver, while perturbed traveltimes are obtained by adding a traveltime correction to the traveltimes of the reference medium. The traveltime correction must be computed along the raypath in the reference medium. Since the raypath is not determined in FD eikonal solvers, we approximate rays by linear segments corresponding to the direction of the phase normal of plane wavefronts in each cell. An isotropic medium as a reference medium works well for weak anisotropy. Using a medium with ellipsoidal anisotropy as a background medium in the perturbation approach allows us to consider stronger anisotropy without losing computational speed. The traveltime computation in media with ellipsoidal anisotropy using an FD eikonal solver is fast and accurate. The relative error is below 0.5% for the models investigated in this study. Numerical examples show that the reference model with ellipsoidal anisotropy allows us to compute the traveltime for models with strong anisotropy with an improved accuracy compared with the isotropic reference medium.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2478.2003.00385.x
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  • 15
    Digitale Medien
    Digitale Medien
    Modelling frequency-dependent seismic anisotropy in fluid-saturated rock with aligned fractures: implication of fracture size estimation from anisotropic measurements (2003)
    PO Box 1354, 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Publishing Ltd
    Geophysical prospecting 51 (2003), S. 0 
    Details
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: Measurements of seismic anisotropy in fractured rock are used at present to deduce information about the fracture orientation and the spatial distribution of fracture intensity. Analysis of the data is based upon equivalent-medium theories that describe the elastic response of a rock containing cracks or fractures in the long-wavelength limit. Conventional models assume frequency independence and cannot distinguish between microcracks and macrofractures. The latter, however, control the fluid flow in many subsurface reservoirs. Therefore, the fracture size is essential information for reservoir engineers. In this study we apply a new equivalent-medium theory that models frequency-dependent anisotropy and is sensitive to the length scale of fractures. The model considers velocity dispersion and attenuation due to a squirt-flow mechanism at two different scales: the grain scale (microcracks and equant matrix porosity) and formation-scale fractures. The theory is first tested and calibrated against published laboratory data. Then we present the analysis and modelling of frequency-dependent shear-wave splitting in multicomponent VSP data from a tight gas reservoir. We invert for fracture density and fracture size from the frequency dependence of the time delay between split shear waves. The derived fracture length matches independent observations from borehole data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2478.2003.00386.x
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  • 16
    Digitale Medien
    Digitale Medien
    Are Hispanic Immigrants in English-Only States at a Homeownership Disadvantage? Evidence from the 1980 and 1990 U.S. Censuses (2003)
    Boston, USA and Oxford, UK : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: Utilizing data from the 1980 and 1990 U.S. census, this study investigates whether the passage of official-English legislation at the state level during the 1980s affected the housing acquisition of foreign-born Hispanics. The results suggest that both limited-English-proficient (LEP) and English-fluent Hispanic immigrants who resided in states that passed English-only legislation were less likely to acquire a home during the 1980s compared to their counterparts in other areas. Consistent with economic theory, however, the group that seemed to be most affected included older LEP residents. One explanation for these findings is that the official-English legislation mirrored growing xenophobia against foreign-born Hispanics, resulting in additional social stratification on the basis of ethnicity in housing markets.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-2257.00198
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  • 17
    Digitale Medien
    Digitale Medien
    The Call of the Wild: Call Centers and Economic Development in Rural Areas (2003)
    Boston, USA and Oxford, UK : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: This paper attempts to reflect critically on the role which telephone call centers might play in the economic development of rural places in the ‘information age’, drawing mainly on a case study of the Highlands and Islands of Scotland. It argues that although call center employment tends mainly to be urban-based, the growth of this form of work does present opportunities for some rural areas. The paper considers the locational factors rural areas would have to possess or develop in order to attract such work. It suggests call centers can make a valuable, though limited, contribution towards rural economic development, principally through the creation of additional employment opportunities and the stimulation of new skills and competencies. It also suggests that call centers do not represent a panacea for rural areas and that, indeed, it would be dangerous for rural areas to become over-reliant on employment in this sector.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-2257.00200
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  • 18
    Digitale Medien
    Digitale Medien
    Errata (2003)
    Boston, USA and Oxford, UK : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-2257.00202
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  • 19
    Digitale Medien
    Digitale Medien
    Telecommunications Infrastructure in the Southeastern United States: Urban and Rural Variation (2003)
    Boston, USA and Oxford, UK : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: The capabilities of central office (CO) telephone switches in four southeastern states (Kentucky, Mississippi, North Carolina, and Tennessee) provide detail on spatial variation in telecommunications technologies. A proposed six-level hierarchy of switch capability was used. Switches with digital capability are concentrated disproportionately in metropolitan areas, largely in response to larger numbers of business establishments. The overall picture in the Southeast is one of tremendous variation—variation across states and variation within the four states being studied. Rural (nonmetro) counties generally, but not always, have both fewer switches overall and fewer switches with digital capability. North Carolina and Tennessee, the two most urban of the four states, also have seen the greatest entry by new telecommunications competitors. These two states have the largest percentages of advanced (digital) switches in both metro and rural counties. At the county level, the number of switches is primarily a function of a county's population but, even more significantly in three states, of the number of business establishments in the county. On the whole, it is residents of metropolitan—not rural—areas who are most likely to be served by newer forms of digital telecommunications.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-2257.00201
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  • 20
    Digitale Medien
    Digitale Medien
    Globalization, E-economy, and Transport (2003)
    Oxford, UK and Malden, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.0017-4815.2003.00226.x
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  • 21
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    Digitale Medien
    The E-economy and the Rise of Technocapitalism: Networks, Firms, and Transportation (2003)
    Oxford, UK and Malden, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: The e-economy is part of a larger phenomenon, technocapitalism, that is transforming business organizations and the ways in which they transact, produce, and ship their goods. Technocapitalism is an evolution of market capitalism that is rooted in technological innovation and supported by such intangibles as creativity and knowledge. This paper considers first the main characteristics of networks that support the e-economy and its source phenomenon, the emergence of technocapitalism. Networks are thought to be the main vehicle through which the e-economy spreads, and they have major effects on the organization of business firms. The culture of technocapitalism, with its emphasis on continuous innovation and rapid adjustment, is largely behind the rising importance of networks. A second section then considers the deconstruction of business firms and its relation to networks, the e-economy, and the rise of technocapitalism. A historical perspective is provided to show the contrast with previous eras. The deconstruction of business organizations involves a major transformation of the norms and ways in which firms are run and structured. Finally, the likely implications for transportation and shipping of the rise of the e-economy, its networks, and the deconstruction of firms are discussed. The logistics, pricing, and infrastructure of shipping are likely to be substantially affected by the spread of the e-economy, its networks, and the deconstruction of firms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.0017-4815.2003.00227.x
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  • 22
    Digitale Medien
    Digitale Medien
    Index to Volume 34 (2003)
    Oxford, UK and Malden, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.0017-4815.2003.00234.x
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  • 23
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    Digitale Medien
    The Agglomeration Dilemma: “Should I Stay or Should I Go?” (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: This paper presents a critical survey of some recent developments in the theory of international trade. Particular emphasis is given to the role of increasing returns to scale and labor mobility in shaping the pattern of industrial location across integrating countries. The goal is to review and discuss the novel insights and predictions of the so-called “new” theories in order to pose and stimulate avenues for future research.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-2257.00218
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  • 24
    Digitale Medien
    Digitale Medien
    Jobs, Houses, and Trees: Changing Regional Structure, Local Land-Use Patterns, and Forest Cover in Southern Indiana (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: Land-use and -cover change is a topic of increasing concern as interest in forest and agricultural land preservation grows. Urban and residential land use is quickly replacing extractive land use in southern Indiana. The interaction between land quality and urban growth pressures is also causing secondary forest growth and forest clearing to occur jointly in a complex spatial pattern. It is argued that similar processes fuel the abandonment of agricultural land leading to private forest regrowth, changes in topography and land quality, and declining real farm product prices. However, the impact of urban growth and development on forests depends more strongly on changes in both the residential housing and labor markets. Using location quotient analysis of aggregate employment patterns, and the relationship between regional labor market changes, the extent of private forest cover was examined from 1967 to 1998. Then an econometric model of land-use shares in forty southern Indiana counties was developed based on the net benefits to agriculture, forestland, and urban uses. To test the need to control explicitly for changes in residential demand and regional economic structure, a series of nested models was estimated. Some evidence was found that changing agricultural profitability is leading to private forest regrowth. It was also uncovered that the ratio of urban to forest land uses is better explained by incorporating measures of residential land value and industrial concentration than simply considering population density alone.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-2257.00220
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    Digitale Medien
    Digitale Medien
    Transitions at Growth and Change (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-2257.00225
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  • 26
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    Digitale Medien
    Alliances, Networks and Competitive Strategy: Rethinking Clusters of Innovation (2003)
    Boston, USA and Oxford, UK : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: Networks of interaction have assumed particular significance in recent years because of their presumed importance for learning and innovation. Alliances between related firms are thought to encourage interactive learning between participating organizations through the sharing of knowledge and information, which is itself facilitated through trust, shared values and ways of working. The vast body of literature that has emerged is, however, incredibly fragmented, encompassing an array of theoretical positions and perspectives. This paper focuses upon two issues which are believed to be of particular significance and which need clarification in order to move to a clearer understanding of the ways in which networks of interaction evolve, and of their capabilities and limitations in relation to economic performance and competitiveness: (1) the importance of network structure, arguing that innovative activity requires flexibility with regard to network formation. (2) The role of geography in relation to the construction and functioning of alliances. It is the contention here that networks are likely to be increasingly international in scope.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-2257.00196
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  • 27
    Digitale Medien
    Digitale Medien
    Book Review (2003)
    Boston, USA and Oxford, UK : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: Constantinos I. Chlomoudis and Athanasios A. Pallis, European Union Port Policy: The Movement Towards A Long Term Strategy
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-2257.00203
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  • 28
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    Digitale Medien
    OPTICAL SINGLE TRANSPORTER RECORDING: Transport Kinetics in Microarrays of Membrane Patches (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 47-67 
    Details
    ISSN: 1056-8700
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Biologie , Physik
    Notizen: Abstract Optical single transporter recording (OSTR) is an emerging technique for the fluorescence microscopic measurement of transport kinetics in membrane patches. Membranes are attached to transparent microarrays of cylindrical test compartments (TCs) ~0.1-100 mum in diameter and ~10-100 mum in depth. Transport across membrane patches that may contain single transporters or transporter populations is recorded by confocal microscopy. By these means transport of proteins through single nuclear pore complexes has been recorded at rates of 〈1 translocation/s. In addition to the high sensitivity in terms of measurable transport rates OSTR features unprecedented spatial selectivity and parallel processing. This article reviews the conceptual basis of OSTR and its realization. Applications to nuclear transport are summarized. The further development of OSTR is discussed and its extension to a diversity of transporters, including translocases and ATP-binding cassette (ABC) pumps, projected.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.biophys.32.110601.142429
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  • 29
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    Digitale Medien
    STRUCTURE AND FUNCTION OF NATURAL KILLER CELL SURFACE RECEPTORS* (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 93-114 
    Details
    ISSN: 1056-8700
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Biologie , Physik
    Notizen: Abstract Since mid-1990, with cloning and identification of several families of natural killer (NK) receptors, research on NK cells began to receive appreciable attention. Determination of structures of NK cell surface receptors and their ligand complexes led to a fast growth in our understanding of the activation and ligand recognition by these receptors as well as their function in innate immunity. Functionally, NK cell surface receptors are divided into two groups, the inhibitory and the activating receptors. Structurally, they belong to either the immunoglobulin (Ig)-like receptor superfamily or the C-type lectin-like receptor (CTLR) superfamily. Their ligands are either members of class I major histocompatibility complexes (MHC) or homologs of class I MHC molecules. The inhibitory form of NK receptors provides the protective immunity through recognizing class I MHC molecules with self-peptides on healthy host cells. The activating, or the noninhibitory, NK receptors mediate the killing of tumor or virally infected cells through their specific ligand recognition. The structures of activating and inhibitory NK cell surface receptors and their complexes with the ligands determined to date, including killer immunoglobulin-like receptors (KIRs) and their complexes with HLA molecules, CD94, Ly49A, and its complex with H-2Dd, and NKG2D receptors and their complexes with class I MHC homologs, are reviewed here.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.biophys.32.110601.142347
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  • 30
    Digitale Medien
    Digitale Medien
    THE POWER AND PROSPECTS OF FLUORESCENCE MICROSCOPIES AND SPECTROSCOPIES (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 161-182 
    Details
    ISSN: 1056-8700
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Biologie , Physik
    Notizen: Abstract Recent years have witnessed a renaissance of fluorescence microscopy techniques and applications, from live-animal multiphoton confocal microscopy to single-molecule fluorescence spectroscopy and imaging in living cells. These achievements have been made possible not so much because of improvements in microscope design, but rather because of development of new detectors, accessible continuous wave and pulsed laser sources, sophisticated multiparameter analysis on one hand, and the development of new probes and labeling chemistries on the other. This review tracks the lineage of ideas and the evolution of thinking that have led to the actual developments, and presents a comprehensive overview of the field, with emphasis put on our laboratory's interest in single-molecule microscopy and spectroscopy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.biophys.32.110601.142525
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  • 31
    Digitale Medien
    Digitale Medien
    NEW INSIGHT INTO SITE-SPECIFIC RECOMBINATION FROM FLP RECOMBINASE-DNA STRUCTURES (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 135-159 
    Details
    ISSN: 1056-8700
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Biologie , Physik
    Notizen: Abstract The lamba integrase, or tyrosine-based family of site-specific recombinases, plays an important role in a variety of biological processes by inserting, excising, and inverting DNA segments. Flp, encoded by the yeast 2-mum plasmid, is the best-characterized eukaryotic member of this family and is responsible for maintaining the copy number of this plasmid. Over the past several years, structural and biochemical studies have shed light on the details of a common catalytic scheme utilized by these enzymes with interesting variations under different biological contexts. The emergence of new Flp structures and solution data provides insights not only into its unique mechanism of active site assembly and activity regulation but also into the specific contributions of certain protein residues to catalysis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.biophys.32.110601.141732
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  • 32
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    Digitale Medien
    X-RAY CRYSTALLOGRAPHIC ANALYSIS OF LIPID-PROTEIN INTERACTIONS IN THE BACTERIORHODOPSIN PURPLE MEMBRANE* (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 285-310 
    Details
    ISSN: 1056-8700
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Biologie , Physik
    Notizen: Abstract The past decade has witnessed increasingly detailed insights into the structural mechanism of the bacteriorhodopsin photocycle. Concurrently, there has been much progress within our knowledge pertaining to the lipids of the purple membrane, including the discovery of new lipids and the overall effort to localize and identify each lipid within the purple membrane. Therefore, there is a need to classify this information to generalize the findings. We discuss the properties and roles of haloarchaeal lipids and present the structural data as individual case studies. Lipid-protein interactions are discussed in the context of structure-function relationships. A brief discussion of the possibility that bacteriorhodopsin functions as a light-driven inward hydroxide pump rather than an outward proton pump is also presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.biophys.32.110601.142516
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  • 33
    Digitale Medien
    Digitale Medien
    THE CRYSTALLOGRAPHIC MODEL OF RHODOPSIN AND ITS USE IN STUDIES OF OTHER G PROTEIN-COUPLED RECEPTORS (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 375-397 
    Details
    ISSN: 1056-8700
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Biologie , Physik
    Notizen: Abstract G protein-coupled receptors (GPCRs) are integral membrane proteins that respond to environmental signals and initiate signal transduction pathways activating cellular processes. Rhodopsin is a GPCR found in rod cells in retina where it functions as a photopigment. Its molecular structure is known from cryo-electron microscopic and X-ray crystallographic studies, and this has reshaped many structure/function questions important in vision science. In addition, this first GPCR structure has provided a structural template for studies of other GPCRs, including many known drug targets. After presenting an overview of the major structural elements of rhodopsin, recent literature covering the use of the rhodopsin structure in analyzing other GPCRs will be summarized. Use of the rhodopsin structural model to understand the structure and function of other GPCRs provides strong evidence validating the structural model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.biophys.32.110601.142520
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  • 34
    Digitale Medien
    Digitale Medien
    PROTEOME ANALYSIS BY MASS SPECTROMETRY* (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 399-424 
    Details
    ISSN: 1056-8700
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Biologie , Physik
    Notizen: Abstract The coupling of high-performance mass spectrometry instrumentation with highly efficient chromatographic and electrophoretic separations has enabled rapid qualitative and quantitative analysis of thousands of proteins from minute samples of biological materials. Here, we review recent progress in the development and application of mass spectrometry-based techniques for the qualitative and quantitative analysis of global proteome samples derived from whole cells, tissues, or organisms. Techniques such as multidimensional peptide and protein separations coupled with mass spectrometry, accurate mass measurement of peptides from global proteome digests, and mass spectrometric characterization of intact proteins hold great promise for characterization of highly complex protein mixtures. Advances in chemical tagging and isotope labeling techniques have enabled quantitative analysis of proteomes, and highly specific isolation strategies have been developed aimed at selective analysis of posttranslationally modified proteins.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.biophys.32.110601.141854
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  • 35
    Digitale Medien
    Digitale Medien
    STANLEY CORRSIN: 1920-1986 (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 35 (2003), S. 1-10 
    Details
    ISSN: 0066-4189
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.fluid.35.101101.161055
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  • 36
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    Digitale Medien
    MECHANISMS ON TRANSVERSE MOTIONS IN TURBULENT WALL FLOWS (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 35 (2003), S. 45-62 
    Details
    ISSN: 0066-4189
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Maschinenbau , Physik
    Notizen: Abstract Drag reduction in wall-bounded flows can be achieved by transverse motions imposed by passive means, e.g., riblets, or by external forcing, such as wall oscillation or transverse traveling-wave excitation. In this article, we review possible physical mechanisms responsible for turbulent drag reduction and corresponding near-wall flow modification.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.fluid.35.101101.161213
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    Digitale Medien
    AERODYNAMICS OF SMALL VEHICLES (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 35 (2003), S. 89-111 
    Details
    ISSN: 0066-4189
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Maschinenbau , Physik
    Notizen: Abstract In this review we describe the aerodynamic problems that must be addressed in order to design a successful small aerial vehicle. The effects of Reynolds number and aspect ratio (AR) on the design and performance of fixed-wing vehicles are described. The boundary-layer behavior on airfoils is especially important in the design of vehicles in this flight regime. The results of a number of experimental boundary-layer studies, including the influence of laminar separation bubbles, are discussed. Several examples of small unmanned aerial vehicles (UAVs) in this regime are described. Also, a brief survey of analytical models for oscillating and flapping-wing propulsion is presented. These range from the earliest examples where quasi-steady, attached flow is assumed, to those that account for the unsteady shed vortex wake as well as flow separation and aeroelastic behavior of a flapping wing. Experiments that complemented the analysis and led to the design of a successful ornithopter are also described.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.fluid.35.101101.161102
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    Digitale Medien
    MIXING EFFICIENCY IN STRATIFIED SHEAR FLOWS (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 35 (2003), S. 135-167 
    Details
    ISSN: 0066-4189
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Maschinenbau , Physik
    Notizen: Abstract The issue of the physical mechanism(s) that control the efficiency with which the density field in stably stratified fluid is mixed by turbulent processes has remained enigmatic. Similarly enigmatic has been an explanation of the numerical value of ~0.2, which is observed to characterize this efficiency experimentally. We review recent work on the turbulence transition in stratified parallel flows that demonstrates that this value is not only numerically predictable but also that it is expected to be a nonmonotonic function of the Richardson number that characterizes preturbulent stratification strength. This value of the mixing efficiency appears to be characteristic of the late-time behavior of the turbulent flow that develops after an initially laminar shear flow has undergone the transition to turbulence through an intermediate instability of Kelvin-Helmholtz type.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.fluid.35.101101.161144
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    Digitale Medien
    SMALL-SCALE HYDRODYNAMICS IN LAKES (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 35 (2003), S. 373-412 
    Details
    ISSN: 0066-4189
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Maschinenbau , Physik
    Notizen: Abstract Recent small-scale turbulence observations allow the mixing regimes in lakes, reservoirs, and other enclosed basins to be categorized into the turbulent surface and bottom boundary layers as well as the comparably quiet interior. The surface layer consists of an energetic wave-affected thin zone at the very top and a law-of-the-wall layer right below, where the classical logarithmic-layer characteristic applies on average. Short-term current and dissipation profiles, however, deviate strongly from any steady state. In contrast, the quasi-steady bottom boundary layer behaves almost perfectly as a logarithmic layer, although periodic seiching modifies the structure in the details. The interior stratified turbulence is extremely weak, even though much of the mechanical energy is contained in baroclinic basin-scale seiching and Kelvin waves or inertial currents (large lakes). The transformation of large-scale motions to turbulence occurs mainly in the bottom boundary and not in the interior, where the local shear remains weak and the Richardson numbers are generally large.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.fluid.35.101101.161220
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  • 40
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    Digitale Medien
    FLOW AND DISPERSION IN URBAN AREAS (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 35 (2003), S. 469-496 
    Details
    ISSN: 0066-4189
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Maschinenbau , Physik
    Notizen: Abstract Increasing urbanization and concern about sustainability and quality of life issues have produced considerable interest in flow and dispersion in urban areas. We address this subject at four scales: regional, city, neighborhood, and street. The flow is one over and through a complex array of structures. Most of the local fluid mechanical processes are understood; how these combine and what is the most appropriate framework to study and quantify the result is less clear. Extensive and structured experimental databases have been compiled recently in several laboratories. A number of major field experiments in urban areas have been completed very recently and more are planned. These have aided understanding as well as model development and evaluation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.fluid.35.101101.161147
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  • 41
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    Digitale Medien
    BIFURCATING AND BLOOMING JETS (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 35 (2003), S. 295-315 
    Details
    ISSN: 0066-4189
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Maschinenbau , Physik
    Notizen: Abstract It is classically assumed that the far field of a round turbulent jet discharging into quiescent fluid has a unique behavior characterized only by its momentum flux. However, there is now considerable evidence that different discharge conditions at the jet nozzle exit can give rise to very different far-field flows. Perhaps the most striking examples of these are the bifurcating and blooming jets produced by appropriate combinations of controlled axial and circumferential excitations at the nozzle exit. With the right excitations, a jet can be made to divide into two separate jets (bifurcating jet), each of which carries half the axial momentum and spreads in a manner similar to a single jet. Trifurcating jets can also be produced. Other excitations can produce blooming jets, in which the jet explodes into a shower of vortex rings, producing a far-field flow that is quite unlike a normal unexcited jet. Bifurcating and blooming jets exhibit much greater mixing than normal jets, suggesting possible applications in flow control. This article summarizes our work on bifurcating and blooming jets, which began with our discovery of them in the early 1980s and continued through the mid- 1990s. One of us (D.E.P.) continued exploration of flow control using excited jets, first at the McDonnell Douglas Corporation, and more recently at the Georgia Institute of Technology. The key to flow control is the manipulation of the large vortical structures in the near field of the jet. Ultimately this work, and that of others, led to full-scale testing of jet engine exhaust mixing control. There it was shown that the jet temperature downstream of the engine can be very significantly reduced by application of well-designed and easily implemented excitation at the engine discharge, thereby solving problems encountered during ground operations. Related jet control work by other investigators is included in this review.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.fluid.35.101101.161128
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    Digitale Medien
    STABILITY AND TRANSITION OF THREE-DIMENSIONAL BOUNDARY LAYERS (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 35 (2003), S. 413-440 
    Details
    ISSN: 0066-4189
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Maschinenbau , Physik
    Notizen: Abstract The recent progress in three-dimensional boundary-layer stability and transition is reviewed. The material focuses on the crossflow instability that leads to transition on swept wings and rotating disks. Following a brief overview of instability mechanisms and the crossflow problem, a summary of the important findings of the 1990s is given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.fluid.35.101101.161045
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    THE STRUCTURE OF MAMMALIAN CYCLOOXYGENASES (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 183-206 
    Details
    ISSN: 1056-8700
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Biologie , Physik
    Notizen: Abstract Cyclooxygenases-1 and -2 (COX-1 and COX-2, also known as prostaglandin H2 synthases-1 and -2) catalyze the committed step in prostaglandin synthesis. COX-1 and -2 are of particular interest because they are the major targets of nonsteroidal antiinflammatory drugs (NSAIDs) including aspirin, ibuprofen, and the new COX-2-selective inhibitors. Inhibition of the COXs with NSAIDs acutely reduces inflammation, pain, and fever, and long-term use of these drugs reduces the incidence of fatal thrombotic events, as well as the development of colon cancer and Alzheimer's disease. In this review, we examine how the structures of COXs relate mechanistically to cyclooxygenase and peroxidase catalysis and how alternative fatty acid substrates bind within the COX active site. We further examine how NSAIDs interact with COXs and how differences in the structure of COX-2 result in enhanced selectivity toward COX-2 inhibitors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.biophys.32.110601.141906
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    COMPUTER SIMULATIONS OF ENZYME CATALYSIS: Methods, Progress, and Insights (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 425-443 
    Details
    ISSN: 1056-8700
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Biologie , Physik
    Notizen: Abstract Understanding the action of enzymes on an atomistic level is one of the important aims of modern biophysics. This review describes the state of the art in addressing this challenge by simulating enzymatic reactions. It considers different modeling methods including the empirical valence bond (EVB) and more standard molecular orbital quantum mechanics/molecular mechanics (QM/MM) methods. The importance of proper configurational averaging of QM/MM energies is emphasized, pointing out that at present such averages are performed most effectively by the EVB method. It is clarified that all properly conducted simulation studies have identified electrostatic preorganization effects as the source of enzyme catalysis. It is argued that the ability to simulate enzymatic reactions also provides the chance to examine the importance of nonelectrostatic contributions and the validity of the corresponding proposals. In fact, simulation studies have indicated that prominent proposals such as desolvation, steric strain, near attack conformation, entropy traps, and coherent dynamics do not account for a major part of the catalytic power of enzymes. Finally, it is pointed out that although some of the issues are likely to remain controversial for some time, computer modeling approaches can provide a powerful tool for understanding enzyme catalysis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.biophys.32.110601.141807
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  • 45
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    Digitale Medien
    MASSIVE STARS IN THE LOCAL GROUP: Implications for Stellar Evolution and Star Formation (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Astronomy and Astrophysics 41 (2003), S. 15-56 
    Details
    ISSN: 0066-4146
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Physik
    Notizen: The galaxies of the Local Group serve as important laboratories for understanding the physics of massive stars. Here I discuss what is involved in identifying various kinds of massive stars in nearby galaxies: the hydrogen-burning O-type stars and their evolved He-burning evolutionary descendants, the luminous blue variables, red supergiants, and Wolf-Rayet stars. Primarily I review what our knowledge of the massive star population in nearby galaxies has taught us about stellar evolution and star formation. I show that the current generation of stellar evolutionary models do well at matching some of the observed features and provide a look at the sort of new observational data that will provide a benchmark against which new models can be evaluated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.astro.41.071601.170033
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    Digitale Medien
    ACTION AT A DISTANCE AND COSMOLOGY: A Historical Perspective (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Astronomy and Astrophysics 41 (2003), S. 169-189 
    Details
    ISSN: 0066-4146
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Physik
    Notizen: The first law of theoretical physics, the Newtonian law of gravitation, relies on the concept of action at a distance. The success of this law led to the concept being applied to electricity and magnetism, which were next to be explored in depth. Here the action at a distance had a limited success and ultimately had to be abandoned in favor of the increasingly more popular field theory. Nevertheless, in the 1940s, an attempt was made to revive the concept of action at a distance in a relativistically invariant way by Wheeler & Feynman (1945, 1949). It inspired a series of investigations in both electrodynamics and gravity in which the field concept was not used but the interaction was described as taking place directly between particles. As it impinged very intimately on cosmology, Hoyle was keenly interested in it. This review discusses the work by Hoyle, the author, and others on the development of electrodynamics and gravitation as direct particle theories. In this review, the author discusses how the work was started and went through stages of increasing sophistication, e.g., extending the Wheeler-Feynman electrodynamics to curved spacetime, its consequences in different cosmologies, and the issues arising from its quantization. The resolution of ultraviolet divergences in quantum electrodynamics is also briefly discussed. The parallel development of a Machian theory of gravitation followed the lead from electrodynamics. In both theories one sees a strong link between the large-scale structure of the universe and local physics, as might be expected from an action-at-a-distance framework.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.astro.41.112202.151716
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    LABORATORY X-RAY ASTROPHYSICS (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Astronomy and Astrophysics 41 (2003), S. 343-390 
    Details
    ISSN: 0066-4146
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Physik
    Notizen: Targeted laboratory astrophysics measurements are being conducted to address the needs of X-ray astronomy. The measurements are producing large sets of reliable atomic data, which include ionization and recombination cross sections for charge balance calculations, as well as line lists, excitation cross sections, and dielectronic recombination rates for interpreting X-ray line formation. Additional experiments focus on resolving specific puzzles posed by astrophysical observations, as well as on calibrating existing and developing new X-ray line diagnostics. We discuss the types of data produced and illustrate how the laboratory measurements support such missions as ASCA, EUVE, Chandra, XMM, and ASTRO-E2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.astro.41.011802.094825
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    QUANTITATIVE SPECTROSCOPY OF PHOTOIONIZED CLOUDS (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Astronomy and Astrophysics 41 (2003), S. 517-554 
    Details
    ISSN: 0066-4146
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Physik
    Notizen: Photoionized clouds are ubiquitous. They define the endpoints of stellar evolution (H II regions and planetary nebulae), constitute the interstellar and intergalactic media, and are found in high redshift quasars and star-forming galaxies. The spectra of these objects are dominated by emission lines that are sensitive to details of the emitting gas. These details include the microscopic atomic processes that cause the gas to glow; the density, composition, and temperature of the gas; and the radiation field of the central continuum source. Large-scale numerical codes that incorporate all the needed physics and predict the observed spectrum have become essential tools in understanding these objects. This article reviews the current status of the numerical simulations of emitting gas, with particular emphasis on photoionized clouds and the underlying simplicity that governs these nebulae; the types of questions that can be addressed by today's codes; and the big questions that remain unanswered.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.astro.41.011802.094836
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    Digitale Medien
    THE FLOW OF HUMAN CROWDS (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 35 (2003), S. 169-182 
    Details
    ISSN: 0066-4189
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Maschinenbau , Physik
    Notizen: Abstract The modern study of a crowd as a flowing continuum is a recent development. Distinct from a classical fluid because of the property that a crowd has the capacity to think, interesting new physical ideas are involved in its study. An appealing property of a crowd in motion is that the nonlinear, time-dependent, simultaneous equations representing a crowd are conformably mappable. This property makes many interesting applications analytically tractable. In this review examples are given in which the theory has been used to provide possible assistance in the annual Muslim Hajj, to understand the Battle of Agincourt, and, surprisingly, to locate barriers that actually increase the flow of pedestrians above that when there are no barriers present. Modern developments may help prevent some of the approximately two thousand deaths that annually occur in accidents owing to crowding.The field of crowd motion, that is, the field of "thinking fluids," is an intriguing area of research with great promise.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.fluid.35.101101.161136
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    Digitale Medien
    RAPID GRANULAR FLOWS (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 35 (2003), S. 267-293 
    Details
    ISSN: 0066-4189
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Maschinenbau , Physik
    Notizen: Abstract The recent avalanche of research activity in the field of granular matter has yielded much progress. The use of state-of-the-art (and other) computational and experimental methods has led to the discovery of new states and patterns and enabled detailed tests of theories and models. The application of statistical mechanical methods and phenomenology has contributed to the understanding of the microscopic a nd macroscopic properties of granular systems. Some previously open problems seem to be solved. Fluidized granular systems (rapid granular flows), recently referred to as granular gases, are often modeled by hydrodynamic equations of motion, some of which are based on systematic expansions applied to the pertinent Boltzmann equation. The undeniable success of granular hydrodynamics is somewhat surprising in view of the lack of scale separation in these systems and the neglect of certain correlations in most derivations of the hydrodynamic equations. Microstructures have been recognized as key features of granular gases; explanations for their existence have been proposed, and many of their properties elucidated. Granular-gas multistability can often be traced back to microstructure dynamics. In spite of these and other impressive advances, this field still poses serious challenges.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.fluid.35.101101.161114
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    TEXTBOOK MULTIGRID EFFICIENCY FOR FLUID SIMULATIONS* (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 35 (2003), S. 317-340 
    Details
    ISSN: 0066-4189
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Maschinenbau , Physik
    Notizen: Abstract Recent advances in achieving textbook multigrid efficiency for fluid simulations are presented. Textbook multigrid efficiency is defined as attaining the solution to the governing system of equations in a computational work that is a small multiple of the operation counts associated with discretizing the system. Strategies are reviewed to attain this efficiency by exploiting the factorizability properties inherent to a range of fluid simulations, including the compressible Navier-Stokes equations. Factorizability is used to separate the elliptic and hyperbolic factors contributing to the target system; each of the factors can then be treated individually and optimally. Boundary regions and discontinuities are addressed with separate (local) treatments. New formulations and recent calculations demonstrating the attainment of textbook efficiency for aerodynamic simulations are shown.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.fluid.35.101101.161209
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    PROTEIN ANALYSIS BY HYDROGEN EXCHANGE MASS SPECTROMETRY (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 1-25 
    Details
    ISSN: 1056-8700
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Biologie , Physik
    Notizen: Abstract Mass spectrometry has provided a powerful method for monitoring hydrogen exchange of protein backbone amides with deuterium from solvent. In comparison to popular NMR approaches, mass spectrometry has the advantages of higher sensitivity, wider coverage of sequence, and the ability to analyze larger proteins. Proteolytic fragmentation of proteins following the exchange reaction provides moderate structural resolution, in some cases enabling measurements from single amides. The technique has provided new insight into protein-protein and protein-ligand interfaces, as well as conformational changes during protein folding or denaturation. In addition, recent studies illustrate the utility of hydrogen exchange mass spectrometry toward detecting protein motions relevant to allostery, covalent modifications, and enzyme function.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.biophys.32.110601.142417
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    Digitale Medien
    CATIONS AS HYDROGEN BOND DONORS: A View of Electrostatic Interactions in DNA (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 27-45 
    Details
    ISSN: 1056-8700
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Biologie , Physik
    Notizen: Abstract Cations are bound to nucleic acids in a solvated state. High-resolution X-ray diffraction studies of oligonucleotides provide a detailed view of Mg2+, and occasionally other ions bound to DNA. In a survey of several such structures, certain general observations emerge. First, cations bind preferentially to the guanine base in the major groove or to phosphate group oxygen atoms. Second, cations interact with DNA most frequently via water molecules in their primary solvation shell, direct ion-DNA contacts being only rarely observed. Thus, the solvated ions should be viewed as hydrogen bond donors in addition to point charges. Finally, ion interaction sites are readily exchangeable: The same site may be occupied by any ion, including spermine, as well as by a water molecule.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.biophys.32.110601.141726
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    Digitale Medien
    THE ROLE OF DYNAMICS IN ENZYME ACTIVITY (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 69-92 
    Details
    ISSN: 1056-8700
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Biologie , Physik
    Notizen: Abstract Although protein function is thought to depend on flexibility, precisely how the dynamics of the molecule and its environment contribute to catalytic mechanisms is unclear. We review experimental and computational work relating to enzyme dynamics and function, including the role of solvent. The evidence suggests that fast motions on the 100 ps timescale, and any motions coupled to these, are not required for enzyme function. Proteins where the function is electron transfer, proton tunneling, or ligand binding may have different dynamical dependencies from those for enzymes, and enzymes with large turnover numbers may have different dynamical dependencies from those that turn over more slowly. The timescale differences between the fastest anharmonic fluctuations and the barrier-crossing rate point to the need to develop methods to resolve the range of motions present in enzymes on different time- and lengthscales.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.biophys.32.110601.142445
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    NUCLEIC ACID RECOGNITION BY OB-FOLD PROTEINS (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 115-133 
    Details
    ISSN: 1056-8700
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Biologie , Physik
    Notizen: Abstract The OB-fold domain is a compact structural motif frequently used for nucleic acid recognition. Structural comparison of all OB-fold/nucleic acid complexes solved to date confirms the low degree of sequence similarity among members of this family while highlighting several structural sequence determinants common to most of these OB-folds. Loops connecting the secondary structural elements in the OB-fold core are extremely variable in length and in functional detail. However, certain features of ligand binding are conserved among OB-fold complexes, including the location of the binding surface, the polarity of the nucleic acid with respect to the OB-fold, and particular nucleic acid-protein interactions commonly used for recognition of single-stranded and unusually structured nucleic acids. Intriguingly, the observation of shared nucleic acid polarity may shed light on the longstanding question concerning OB-fold origins, indicating that it is unlikely that members of this family arose via convergent evolution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.biophys.32.110601.142506
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    Digitale Medien
    LIQUID-LIQUID IMMISCIBILITY IN MEMBRANES (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biophysics and Biomolecular Structure 32 (2003), S. 469-492 
    Details
    ISSN: 1056-8700
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Biologie , Physik
    Notizen: Abstract The observation of liquid-liquid immiscibility in cholesterol-phospholipid mixtures in monolayers and bilayers has opened a broad field of research into their physical chemistry. Some mixtures exhibit multiple immiscibilities. This unusual property has led to a thermodynamic model of "condensed complexes." These complexes are the consequence of an exothermic, reversible reaction between cholesterol and phospholipids. In this quantitative model the complexes are sometimes concentrated in a separate liquid phase. The phase separation into a complex-rich phase depends on membrane composition and intensive variables such as temperature. The properties of defined cholesterol-phospholipid mixtures provide a conceptual foundation for the exploration of a number of aspects of the biophysics and biochemistry of animal cell membranes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.biophys.32.110601.141704
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    MY LIFE IN ASTROPHYSICS* (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Astronomy and Astrophysics 41 (2003), S. 1-14 
    Details
    ISSN: 0066-4146
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Physik
    Notizen: Astrophysics has been an important part of my personal and scientific life three times. The first was in 1938 when I did work on stellar energy production. The second was a joyful period nearly 30 years later when that work was rewarded with the Nobel Prize in physics. And the third has lasted over the time since my retirement in 1975 during which Gerry Brown and I have had a very satisfactory collaboration exploring various aspects of supernovae and, more recently, binary pairs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.astro.41.011802.094853
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    MASS LOSS FROM THE NUCLEI OF ACTIVE GALAXIES (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Astronomy and Astrophysics 41 (2003), S. 117-167 
    Details
    ISSN: 0066-4146
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Physik
    Notizen: Blueshifted absorption lines in the UV and X-ray spectra of active galaxies reveal the presence of massive outflows of ionized gas from their nuclei. The "intrinsic" UV and X-ray absorbers show large global covering factors of the central continuum source, and the inferred mass loss rates are comparable to the mass accretion rates. Many absorbers show variable ionic column densities, which are attributed to a combination of variable ionizing flux and motion of gas into and out of the line of sight. Detailed studies of the intrinsic absorbers, with the assistance of monitoring observations and photoionization models, provide constraints on their kinematics, physical conditions, and locations relative to the central continuum source, which range from the inner nucleus (~0.01 pc) to the galactic disk or halo (~10 kpc). Dynamical models that make use of thermal winds, radiation pressure, and/or hydromagnetic flows have reached a level of sophistication that permits comparisons with the observational constraints.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.astro.41.082801.100328
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    Digitale Medien
    COOL WHITE DWARFS* (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Astronomy and Astrophysics 41 (2003), S. 465-515 
    Details
    ISSN: 0066-4146
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Physik
    Notizen: Old, cool white dwarfs convey valuable information about the early history of our Galaxy. They have been used to determine the age of the galactic disk, several open clusters, and a globular cluster. We review the current understanding of the physics of cool white dwarfs, including their mass distribution, chemical evolution, magnetism, and cooling. We also examine the role of white dwarfs as tracers of various stellar populations, both in terms of observational searches and theoretical models.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.astro.41.081401.155117
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    EVOLUTION OF A HABITABLE PLANET (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Astronomy and Astrophysics 41 (2003), S. 429-463 
    Details
    ISSN: 0066-4146
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Physik
    Notizen: Giant planets have now been discovered around other stars, and it is only a matter of time until Earth-sized planets are detected. Whether any of these planets are suitable for life depends on their volatile abundances, especially water, and on their climates. Only planets within the liquid-water habitable zone (HZ) can support life on their surfaces and, thus, can be analyzed remotely to determine whether they are inhabited. Fortunately, current models predict that HZs are relatively wide around main-sequence stars not too different from our sun. This conclusion is based on studies of how our own planet has evolved over time. Earth's climate has remained conducive to life for the past 3.5 billion years or more, despite a large increase in solar luminosity, probably because of previous higher concentrations of CO2 and/or CH4. Both these gases are involved in negative feedback loops that help to stabilize the climate. In addition to these topics, we also briefly discuss the rise of atmospheric O2 and O3, along with their possible significance as indicators of life on other planets.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.astro.41.071601.170049
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    EMBEDDED CLUSTERS IN MOLECULAR CLOUDS (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Astronomy and Astrophysics 41 (2003), S. 57-115 
    Details
    ISSN: 0066-4146
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Physik
    Notizen: Stellar clusters are born embedded within giant molecular clouds (GMCs) and during their formation and early evolution are often only visible at infrared wavelengths, being heavily obscured by dust. Over the past 15 years advances in infrared detection capabilities have enabled the first systematic studies of embedded clusters in galactic molecular clouds. In this article we review the current state of empirical knowledge concerning these extremely young protocluster systems. From a survey of the literature we compile the first extensive catalog of galactic embedded clusters. We use the catalog to construct the mass function and estimate the birthrate for embedded clusters within ~2 kpc of the sun. We find that the embedded cluster birthrate exceeds that of visible open clusters by an order of magnitude or more indicating a high infant mortality rate for protocluster systems. Less than 4-7% of embedded clusters survive emergence from molecular clouds to become bound clusters of Pleiades age. The vast majority (90%) of stars that form in embedded clusters form in rich clusters of 100 or more members with masses in excess of 50 Mo. Moreover, observations of nearby cloud complexes indicate that embedded clusters account for a significant (70-90%) fraction of all stars formed in GMCs. We review the role of embedded clusters in investigating the nature of the initial mass function (IMF) that, in one nearby example, has been measured over the entire range of stellar and substellar mass, from OB stars to substellar objects near the deuterium burning limit. We also review the role embedded clusters play in the investigation of circumstellar disk evolution and the important constraints they provide for understanding the origin of planetary systems. Finally, we discuss current ideas concerning the origin and dynamical evolution of embedded clusters and the implications for the formation of bound open clusters.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.astro.41.011802.094844
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    Digitale Medien
    POST-AGB STARS (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Astronomy and Astrophysics 41 (2003), S. 391-427 
    Details
    ISSN: 0066-4146
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Physik
    Notizen: In this contribution, a review is presented on the ample data obtained on post-AGB stars, both on the central stars and their circumstellar material. The fast evolutionary phase is characterized by a rapid change in the properties of the objects, but the variety is so large that there is yet no clear consensus on how the detailed studies of individual objects are linked together by evolutionary channels. The absence of strong molecular veiling in the photospheres of the central stars, together with a spread in intrinsic metallicity make post-AGB stars very useful in constraining AGB chemical evolutionary models. We discuss the surprisingly wide variety of chemical signatures observed. The onset in the creation process of the panoply of structures and shapes observed in planetary nebulae occurs during the short post-AGB evolution, but the physical nature of the processes involved is still badly understood. In the rapidly growing field of circumstellar mineralogy, post-AGB stars have their story to tell and also the molecular envelope changes significantly due to dilution and hardening of the stellar radiation. The real-time evolution of some objects suffering a late thermal flash is reviewed and their possible link to other hydrogen-deficient objects is discussed. Any review on stellar evolution has a section on binaries and this contribution is no exception because binaries make up a significant fraction of the post-AGB stars known to date.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.astro.41.071601.170018
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    Digitale Medien
    AIRCRAFT ICING (2003)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 35 (2003), S. 11-21 
    Details
    ISSN: 0066-4189
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Maschinenbau , Physik
    Notizen: Abstract Full-scale icing experiments and, therefore, certification time and cost can be significantly reduced by developing calculation methods to evaluate the aircraft and system performance for a wide range of icing conditions. This article summarizes calculation methods for icing that include ice accretion, ice system performance, and icing effects on aircraft.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1146/annurev.fluid.35.101101.161217
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    Digitale Medien
    E-commerce, Transportation, and Economic Geography (2003)
    Oxford, UK and Malden, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: This paper explores possible ways in which growth in Internet retailing (e-retailing) may affect the spatial distribution of economic activities. After a brief overview of e-retailing, a categorization of possible spatial impacts is introduced. These include impacts on the retail industry, such as substitution of e-retail for brick-and-mortar retail, impacts on transportation, such as substitution of freight transportation for personal transportation in goods delivery, and pervasive impacts that affect the whole economy. The latter category includes uniform delivered pricing, spatial leveling of accessibility, and marketing strategies that target individuals rather than regions. The question of whether e-retailing and brick-and-mortar retailing are truly substitutes is taken up in the next section, along with potential implications of multi-channel retailing. The final section of the paper defines some critical research directions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.0017-4815.2003.00228.x
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    Emerging Global Logistics Networks: Implications for Transport Systems and Policies (2003)
    Oxford, UK and Malden, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: Logistics chains are constantly changing to facilitate increasingly global movements. In qualitative terms, long term trends in logistics services indicate a growing degree of product customization and an increased responsiveness in order delivery. These trends impact on the development of technology and the growth of welfare in different world regions in different ways. This paper drafts a research agenda which will help to improve understanding of the interrelationships between trade, logistics, transport, and regional development at a global scale. Rather than being an exhaustive or detailed inventory of trends, the paper provides a focus on “supply chain by thinking.” The key starting point is the need for more and more efficient transportation and sophisticated logistics processes. Three subjects are treated: First, the strategic implications of borderless supply chain management on the choice of alternative logistics structures in supply chains are considered; second, the possible impacts of the expected changes in supply chain processes upon regional economic activities are examined; third, the impacts of changes in global logistic processes on the transportation system and, in turn, on the environment are explored. This discussion leads to the identification of some new research challenges in the field of transportation and logistics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.0017-4815.2003.00230.x
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    Digitale Medien
    ICT and Sustainable Mobility: From Impacts to Policy (2003)
    Oxford, UK and Malden, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: The question “Will using Information and Communication Technology (ICT) systems enable a more sustainable mobility?” is answered through analyzing current ICT policy in the EU and the United States of America (USA), through developing a conceptual model to structure the expected direct and indirect effects of ICT systems on mobility, and through building models for three selected ICT systems to estimate their quantitative effects on mobility. Based on the models, ICT systems seem to have limited mobility reduction potential (in terms of CO2 emissions and kilometer savings). On the short term, because of efficiency gains, ICT systems have a positive impact. In the long term, better quality of mobility will attract new demand and this will again result in an increase of travel. For policymakers this implies that ICT systems in the short run can make mobility more efficient. In the long run, to prevent the more efficient mobility from attracting new traffic, the implementation of any ICT system should be accompanied by a stronger pricing policy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.0017-4815.2003.00231.x
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    The Onset of Health Problems and the Propensity of Workers to Change Employers and Occupations (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: Although many studies have investigated how poor health affects hours of work and labor force participation, few have examined the extent to which individuals adapt in order to remain in the labor market. Individuals experiencing health problems may move to different types of work in order to remain in the labor force or to reduce the negative labor market consequences of illness. This paper investigates the movement between employers, and among occupation categories when changing employers, using data from the Health and Retirement Study (HRS). One advantage of the HRS is that its questions on life-cycle employment and health patterns permit a long-term perspective on job mobility that is unavailable in most other datasets. Workers with health problems are more likely than healthy workers to remain with their current employer than to switch employers. But among those who switch employers, those with health problems are more likely to change broad occupational categories than are healthy workers. While many individuals remain with the same employer after the onset of health problems, many do switch employers and occupations, even in the presence of ADA legislation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-2257.00219
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    Digitale Medien
    Property Values in a Low Populated Area when Dual Noxious Facilities are Present (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: This paper examines how the presence of dual, disparate environmental disamenities located near each other impact property values in a semi-rural area. A heavy metals manufacturing facility and a rubber-compounding factory operate two and one half miles apart in a small community. The heavy metals manufacturing facility uses low-level depleted uranium in its production. The level of production is small and the production process does not emit visible air pollution or odors that can be easily identified. Thus, if the surrounding community negatively perceives a potential risk, it is not through the channels of sight or smell. The rubber-compounding factory emits foul odors and some visible air pollution. Thus, its negative externalities and potential risks are easily perceptible. Using the hedonic price technique, this paper examines the impact of the use of a non-perceptible hazardous material in the production of a good on housing prices in a community when another more visible, noxious facility is present. The results show that noticeable disamenities are capitalized into housing values, while non-visible ones are not.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-2257.00222
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    Some Micro-Evidence on the “Porter Hypothesis” from Austrian VOC Emission Standards (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: This paper presents some micro-evidence relevant to the “Porter Hypothesis” on the techno-economic consequences of Austrian Volatile Organic Compound (VOC) emission standards, the most restrictive of their kind in the world. Using firm-level survey data and complementing it with highly disaggregated foreign trade data, the paper explores whether the standards had a palpable impact on the competitiveness of Austrian manufacturers of paints, coatings, printing inks, and adhesives, whether compliance stimulated innovation in this industry, whether the standards crowded out other, more productive Research and Development (R&D), and whether compliance efforts gave rise to unexpected benefits of compliance. It finds no unequivocal aggregate impact on the competitiveness of regulated firms, yet does find some interesting variation with firm size. Moreover, the standards appear to have dampened import competition. The standards gave rise to considerable changes in firms’ product range and appear to have accelerated the rate of product innovation in the regulated industry. R&D spending to develop compliant products is found to be very unevenly distributed, mainly due to technological and, to a lesser extent, organizational factors. There is evidence that compliance efforts displaced or postponed existing R&D projects. However, there is also evidence that search for compliant products yielded unexpected and beneficial ideas, knowledge, and competencies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-2257.00223
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    Digitale Medien
    Impacts of IT Advances and E-commerce on Transportation in Producer Services (2003)
    Oxford, UK and Malden, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: Producer services have been among the most rapidly growing industries, as measured by employment, in the United States and in Europe in recent decades. The production and delivery of these specialized forms of service industry work require the use of transportation and communications systems in a variety of ways, including the physical movement of people working in these industries, as well as the movement of the information related to the production and distribution of their work. Some of this work is performed in localized markets, requiring travel between clients and suppliers in local transportation modes, such as auto, bus, or other types of transportation. Other work is done by specialists who travel interregionally and globally to do their work, primarily traveling to their clients. There is little knowledge of how these production relationships have changed with the advent of the Internet and the widespread use of e-mail in the business production process. Within the framework of this STELLA initiative, this paper outlines research needs in this area, and frames an approach that would produce badly needed knowledge about impacts on the producer services of the Internet and related e-commerce initiatives on physical transportation systems at a local to interregional scale.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.0017-4815.2003.00229.x
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    Digitale Medien
    Thanks to Manuscript Reviewers (2003)
    Oxford, UK and Malden, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.0017-4815.2003.00233.x
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  • 72
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    Logistics Strategy and Transport Service Choices: An Adaptive Stated Preference Experiment (2003)
    Oxford, UK and Malden, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: This paper presents the results of a microanalysis of freight transport demand in a logistics context. Current research concentrates, with few exceptions, on shippers’ choice of a transport mode. However, in a global context, shippers’ behavior has to be conceived as a complex decision, which considers transport mode choice as only a part of a firm's logistics strategy. Since no data exist to directly estimate the marginal values for different qualities of transport and logistics services, a stated preference approach is applied. Adaptive stated preference experiments were performed for twenty-two firms in Italy and in Switzerland. The experimental results—forty hypothetical binary choices per firm—were completed by background information on the firms’ long-term logistics strategies. The results confirm the relevance of the logistics context (e.g., JIT strategies on the supplier's or customer's side) for transport demand. The calculated marginal values of time and characteristics (reliability, frequency, etc.) provide important insights and permit generalized costs in freight transport models to be recalibrated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.0017-4815.2003.00232.x
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  • 73
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    Digitale Medien
    Mergers and Acquisitions in the Telecommunications Industry (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: The 1990s witnessed an enormous wave of mergers and acquisitions dramatically reconfigure the market structure of global telecommunications. In Europe and the U.S., telecommunications firms have steadily consolidated into a shrinking pool of providers, rapidly oligopolizing the industry. This paper reviews the number and size of mergers and acquisitions globally in the 1990s and charts the national patterns of purchasers and target firms, noting the overwhelming hegemony of American corporations. The reasons behind this process include globalization, deregulation, the convergence of digital technologies, the search for economies of scale and scope, and U.S. corporate tax laws. It also points to the impacts of this oligopolization on consumer prices, labor, equity of access to telecommunications services, and the political and cultural repercussions of increasingly concentrated ownership.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-2257.00221
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    Digitale Medien
    Mark C. Berger (1955-2003) (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-2257.00224
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    Digitale Medien
    Local Industry Agglomeration and New Business Activity (2003)
    Boston, USA and Oxford, UK : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: New businesses are highly involved in innovative activity, which enhances worker productivity and leads to increased economic output. This paper investigates the effects of industry concentration on the incidence of new business openings in the 5,504 Maine county-industries. Empirical findings indicate that new business activity increases with the number of incumbent establishments in a county-industry and its concentration level relative to the U.S. economy. Model simulations show that raising county-industries, with no initial industry presence, to concentration levels similar to that of the industry in the U.S. economy results in a 1.7 to 8.9 percent increase in the expected number of business openings over a three-year period. Empirical results also suggest that industry clusters comprised of young and small establishments are more conducive to new business formation than clusters made up of mature and large companies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-2257.00197
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    Digitale Medien
    Does Public Lands Policy Affect Local Wage Growth? (2003)
    Boston, USA and Oxford, UK : Blackwell Publishing Ltd
    Growth and change 34 (2003), S. 0 
    Details
    ISSN: 1468-2257
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Wirtschaftswissenschaften
    Notizen: The effects on wage growth of management practices applied on public lands in the Northern Forest region of the United States are quantified. A central objective is to determine if the management of public lands for preservationist uses results in lower average wages. This is a frequent claim made by critics of land preservation who argue that preservationist management, by prohibiting resource extraction, causes the composition of employment to shift from high-wage jobs in resource-based manufacturing to low-wage jobs in the service sector. A model of simultaneous employment and net migration growth is estimated with data on non-metropolitan counties over the period 1990 to 1999 and applied in a recursive relationship to wage growth. In earlier studies, models of this type have typically been specified in levels. Time-series evidence that supports a preference for growth rates is provided as the form for such models. Exogenous variables in this model include the 1990 shares of the county land base that are publicly owned and managed for preservationist (non-extractive) uses and multiple (including extractive) uses. It was found that wage growth rates are not significantly affected by the shares of land under either management regime. As well, recent declines in national forest timber sales are found to have no effect on wage growth.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-2257.00199
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    Digitale Medien
    Knowledge acquisition in incomplete fuzzy information systems via the rough set approach (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Expert systems 20 (2003), S. 0 
    Details
    ISSN: 1468-0394
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Informatik
    Notizen: Abstract: Machine learning can extract desired knowledge from training examples and ease the development bottleneck in building expert systems. Most learning approaches derive rules from complete and incomplete data sets. If attribute values are known as possibility distributions on the domain of the attributes, the system is called an incomplete fuzzy information system. Learning from incomplete fuzzy data sets is usually more difficult than learning from complete data sets and incomplete data sets. In this paper, we deal with the problem of producing a set of certain and possible rules from incomplete fuzzy data sets based on rough sets. The notions of lower and upper generalized fuzzy rough approximations are introduced. By using the fuzzy rough upper approximation operator, we transform each fuzzy subset of the domain of every attribute in an incomplete fuzzy information system into a fuzzy subset of the universe, from which fuzzy similarity neighbourhoods of objects in the system are derived. The fuzzy lower and upper approximations for any subset of the universe are then calculated and the knowledge hidden in the information system is unravelled and expressed in the form of decision rules.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-0394.00252
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    Digitale Medien
    Probabilistic approaches to rough sets (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Expert systems 20 (2003), S. 0 
    Details
    ISSN: 1468-0394
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Informatik
    Notizen: Abstract: Probabilistic approaches to rough sets in granulation, approximation and rule induction are reviewed. The Shannon entropy function is used to quantitatively characterize partitions of a universe. Both algebraic and probabilistic rough set approximations are studied. The probabilistic approximations are defined in a decision-theoretic framework. The problem of rule induction, a major application of rough set theory, is studied in probabilistic and information-theoretic terms. Two types of rules are analyzed: the local, low order rules, and the global, high order rules.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-0394.00253
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    A rough set approach to knowledge reduction based on inclusion degree and evidence reasoning theory (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Expert systems 20 (2003), S. 0 
    Details
    ISSN: 1468-0394
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Informatik
    Notizen: Abstract: The theory of rough sets is an extension of set theory for studying intelligent systems characterized by insufficient and incomplete information. We discuss the basic concept and properties of knowledge reduction based on inclusion degree and evidence reasoning theory, and propose a knowledge discovery approach based on inclusion degree and evidence reasoning theory.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-0394.00254
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    Digitale Medien
    Acquisition of hierarchy-structured probabilistic decision tables and rules from data (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Expert systems 20 (2003), S. 0 
    Details
    ISSN: 1468-0394
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Informatik
    Notizen: Abstract: The paper is concerned with the creation of predictive models from data within the framework of the variable precision rough set model. It is focused on two aspects of the model derivation: computation of uncertain, in general, rules from information contained in probabilistic decision tables and forming hierarchies of decision tables with the objective of reduction or elimination of decision boundaries in the resulting classifiers. A new technique of creation of a linearly structured hierarchy of decision tables is introduced and compared to tree-structured hierarchy. It is argued that the linearly structured hierarchy has significant advantages over tree-structured hierarchy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-0394.00255
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    Digitale Medien
    News (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Expert systems 20 (2003), S. 0 
    Details
    ISSN: 1468-0394
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Informatik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-0394.00256
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    Digitale Medien
    Diary (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Expert systems 20 (2003), S. 0 
    Details
    ISSN: 1468-0394
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Informatik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-0394.00257
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    Digitale Medien
    On a responsive replenishment system: a fuzzy logic approach (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Expert systems 20 (2003), S. 0 
    Details
    ISSN: 1468-0394
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Informatik
    Notizen: In today's competitive business environment, it is important that customers are able to obtain their preferred items in the shops they visit, particularly for convenience store chains such as 7–Eleven where popular items are expected to be readily available on the shelves of the stores for buyers. To minimize the cost of running such store chains, it is essential that stocks be kept to a minimum and at the same time large varieties of popular items are available for customers. In this respect, the replenishment system needs to be able to cope with the taxing demands of minimal inventory but at the same time keeping large varieties of needed items. This paper proposes a replenishment system which is able to respond to the fluctuating demands of customers and provide a timely supply of needed items in a cost–effective way. The proposed system embraces the principle of fuzzy logic which is able to deal with uncertainties by virtue of its fuzzy rules reasoning mechanism, thereby leveraging the responsiveness of the entire replenishment system for the chain stores. To validate the feasibility of the approach, a case study has been conducted in an emulated environment with promising results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-0394.00221
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  • 84
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    Digitale Medien
    Providing Websites with capabilities of one–to–one marketing (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Expert systems 20 (2003), S. 0 
    Details
    ISSN: 1468-0394
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Informatik
    Notizen: A formidable synergy can be obtained by putting expert system technology into the Internet. The modern trend of embedding expert systems into Websites turns out to be very promising, in particular for the field of marketing via the Web. The last two years have seen a growing interest in providing Websites with suitable embedded expert systems for one–to–one marketing. One–to– one marketing means marketing in a personalized way, i.e. marketing in a way that is adaptive to the personal needs of the user. A basic feature of this marketing framework consists in personalized prioritizing of news, i.e. presenting information in an order that is relevant to the specific needs of the current user. If the personalized prioritizing of news is a very useful feature in wired Web, it becomes essential in wireless Web, the promising next generation of the Web.The paper presents a general methodology for personalized prioritizing of news. The methodology integrates decision theory with a deep–knowledge–based user model (i.e. causal knowledge linking user preferences to user goals). The deep–knowledge model of the user is a source of power of the methodology because it allows the system to know (and possibly explain) why the user acts the way he/she acts. Another relevant aspect of the methodology is that the burden of personalization is not placed on the user, and in fact the user does not have to declare his/her needs or interests or goals: they are automatically inferred from his/her profile data. In order to investigate the ideas underlying the proposal, a methodology example has been implemented in a prototype and then tested on real cases in the context of a supercomputing portal.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-0394.00220
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  • 85
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    Digitale Medien
    Diary (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Expert systems 20 (2003), S. 0 
    Details
    ISSN: 1468-0394
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Informatik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-0394.00224
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  • 86
    Digitale Medien
    Digitale Medien
    News (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Expert systems 20 (2003), S. 0 
    Details
    ISSN: 1468-0394
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Informatik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-0394.00223
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  • 87
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    Digitale Medien
    Fieldwork and Tropicality in French Indochina: Reflections on Pierre Gourou's Les Paysans Du Delta Tonkinois, 1936 (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Singapore journal of tropical geography 24 (2003), S. 0 
    Details
    ISSN: 1467-9493
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie
    Notizen: This paper examines the fieldwork undertaken by the distinguished French geographer Pierre Gourou (1900–99) in the Tonkin Delta (Red River Delta) of northern Vietnam in the 1920s and 1930s, and his wider configuration of “the tropical world” as a distinct space of knowledge and radical otherness. Gourou's fieldwork endeavours in French Indochina are interpreted in the light of recent work on “tropicality”: the idea that “the tropics” need to be understood as a western cultural construction and colonising discourse that essentialised the hot, wet regions of the world, and exalted the temperate world over its tropical counterpart. The paper focuses on Gourou's monumental 1936 study Les paysans du delta tonkinois, étude de géographie humaine. It is argued that in this study, and his later comparative work on the tropics, Gourou elaborated a distinct geographical variant of tropicality, but one that, ultimately, reinforced the essentialist logic and momentum of this discourse. Particular attention is paid to the geographical ideas, fieldwork techniques and discursive strategies that Gourou used in his 1936 study, and the French colonial context in which he worked. The article shows how Gourou appealed to western reason and science as tools of study, identified overpopulation as the key problem facing the Tonkin Delta, and suggested that colonial practices of modernisation had a limited place and ineffectual role in the rice plains of the region.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1467-9493.00149
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  • 88
    Digitale Medien
    Digitale Medien
    Under the Microscope: Fieldwork Practice and Cuba's Biotechnology Industry: A Reflexive Affair? (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Singapore journal of tropical geography 24 (2003), S. 0 
    Details
    ISSN: 1467-9493
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie
    Notizen: Through a re-reading of my Ph.D. fieldwork on Cuba's biotechnology industry, I empirically pull apart the relationship between fieldwork practice and knowledge production as experienced in my research. I argue that reflexivity is an insufficiently critiqued concept and, as a result, that its widespread influence in contemporary fieldwork practice works to obscure the influence of “others”, not just on the “doing” of research but on the conceptual development of the methodology itself. I make this argument by focusing on the various strategies I employed to actualise my research methodology, the problems I met with and the subsequent pull of my research in new directions. I cover such issues as gaining access, working in multiple locales across antagonistic polities, what happens when fieldwork goes wrong and the notion of “empirical drift”. I use these issues to examine how I was actively constructing both my field and my research methodology at the same time and through others. I try to show how the fact that fieldwork can be simultaneously a lived experience, a socially constructed performance and an episteme accounts for much of its distinctive qualities as a milieu in which existing knowledge is put to the test, or added to. I argue that these same qualities allow it to be a deeply intertextual process, or a joint work between the researcher and the field. This, I suggest, warrants greater recognition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1467-9493.00151
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  • 89
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    Digitale Medien
    Negotiating Expectations in the Field: Gatekeepers, Research Fatigue and Cultural Biases (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Singapore journal of tropical geography 24 (2003), S. 0 
    Details
    ISSN: 1467-9493
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie
    Notizen: This paper considers disjunctures between my expectations and experience of doing dissertation fieldwork, which I conducted in Benin between the autumns of 1997 and 1998. The research examined the nature of women's livelihood strategies and their associated outcomes in terms of material well-being. I now believe that my feminist worldview, and my growing exhaustion as the project progressed, resulted in my minimising the importance of key aspects of fieldwork in an African context. Specifically, I downplayed the importance of negotiating with male “gatekeepers” in gaining access to the women with whom I wanted to work. While most of the time I was able to manage this well enough, one day, in particular, stands out as a time when I handled these negotiations very poorly. This paper compares the experiences of that day with another much more productive and fruitful one to examine how and why expectations and experience can diverge. A consideration of some of the issues that resulted in the “lost day” might prove instructive for other researchers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1467-9493.00152
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  • 90
    Digitale Medien
    Digitale Medien
    Brainstorming, Modified Logframes and the Conversion of Research Hypotheses into Field Questions: Reflections from Team-based Fieldwork in Eastern India (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Singapore journal of tropical geography 24 (2003), S. 0 
    Details
    ISSN: 1467-9493
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie
    Notizen: This paper considers some practical problems associated with organising large-scale comparative field research in eastern India. The focus of the paper is on the use of brainstorming and “modified logframes” as two means by which hypotheses about the working of the local state from the point of view of the rural poor could be turned into concrete field questions. The paper is less concerned with ethical and positional issues relating to team-based research in “the tropics” (on this, see Williams et al., 2003a) than with the equally important if apparently more prosaic issues relating to the flawed but necessary search for objectivity and rigour in comparative field studies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1467-9493.00155
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  • 91
    Digitale Medien
    Digitale Medien
    Development and Governmentality (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Singapore journal of tropical geography 24 (2003), S. 0 
    Details
    ISSN: 1467-9493
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie
    Notizen: The subjectivity of individuals, the so-called speakers and hearers of political discourse, who actually, or even ideally, populate a state, needs to be understood in terms of enunciative modalities - the statuses, sites, and positions - of their existence as political subjects. Enunciative modalities refer to the ways a discursive practice is attached to bodies in space (Clifford, 2001:56).Governmental thought territorializes itself in different ways… We can analyze the ways in which the idea of a territorially bounded, politically governed nation state under sovereign authority took shape… One can trace anomalous governmental histories of smaller-scale territories… and one can also think of these [as] spaces of enclosure that governmental thought has imagined and penetrated… how [does it] happen that social thought territorializes itself on the problem of [for example] the slum in the nineteenth century (Rose, 1999:34–36)?
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1467-9493.00140
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  • 92
    Digitale Medien
    Digitale Medien
    Book Reviews (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Singapore journal of tropical geography 24 (2003), S. 0 
    Details
    ISSN: 1467-9493
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie
    Notizen: Books reviewed:Nancy Leys Stepan, Picturing Tropical NatureAnne-Marie Hilsdon, Martha Macintyre, Vera Mackie and Maila Stivens (eds.), Human Rights and Gender Politics: Asia-Pacific PerspectivesElisabeth Croll, Endangered Daughters: Discrimination and Development in AsiaTai Yong Tan and Gyanesh Kudaisya, The Aftermath of Partition in South AsiaHal Hill and Joaõ M. Saldanha (eds.), East Timor: Development Challenges for the World's Newest NationRobert E. Rhoades (ed.), Bridging Human and Ecological Landscapes: Participatory Research and Sustainable Development in an Andean Frontier
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1467-9493.00147
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  • 93
    Digitale Medien
    Digitale Medien
    Intuitionistic fuzzy rough sets: at the crossroads of imperfect knowledge (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Expert systems 20 (2003), S. 0 
    Details
    ISSN: 1468-0394
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Informatik
    Notizen: Abstract: Just like rough set theory, fuzzy set theory addresses the topic of dealing with imperfect knowledge. Recent investigations have shown how both theories can be combined into a more flexible, more expressive framework for modelling and processing incomplete information in information systems. At the same time, intuitionistic fuzzy sets have been proposed as an attractive extension of fuzzy sets, enriching the latter with extra features to represent uncertainty (on top of vagueness). Unfortunately, the various tentative definitions of the concept of an ‘intuitionistic fuzzy rough set’ that were raised in their wake are a far cry from the original objectives of rough set theory. We intend to fill an obvious gap by introducing a new definition of intuitionistic fuzzy rough sets, as the most natural generalization of Pawlak's original concept of rough sets.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-0394.00250
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  • 94
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    Digitale Medien
    Book Review: (2003)
    Oxford, UK and Boston, USA : Blackwell Publishing Ltd
    Expert systems 20 (2003), S. 0 
    Details
    ISSN: 1468-0394
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Informatik
    Notizen: Book reviewed:Adrian A. Hopgood, Intelligent Systems for Engineers and Scientists
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/1468-0394.00222
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  • 95
    Digitale Medien
    Digitale Medien
    Marine birds breeding in Penny Strait and Queens Channel, Nunavut, Canada (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Polar research 22 (2003), S. 0 
    Details
    ISSN: 1751-8369
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Geologie und Paläontologie
    Notizen: Surveys of breeding birds on small islands in Penny Strait and Queens Channel, Nunavut Territory, Canada, were conducted in July 2002 and 2003. Approximately 3600 marine birds were observed, with the most common species being Arctic terns (Sterna paradisaea, N=2400) and common eiders (Somateria mollissima borealis, N=620). We observed no Ross's gulls (Rhodostethia rosed) in either year, and we found ivory gulls (Pagophila eburned) only in 2003, even though these species commonly bred here in the 1970s. This previously unsurveyed region supports numerous breeding marine birds, but reproductive success on these small islands may be dependent on annual ice conditions and consequent movements of Arctic foxes (Alopex lagopus).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1751-8369.2003.tb00121.x
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  • 96
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    Digitale Medien
    Decadal decrease of Antarctic sea ice extent inferred from whaling records revisited on the basis of historical and modern sea ice records (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Polar research 22 (2003), S. 0 
    Details
    ISSN: 1751-8369
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Geologie und Paläontologie
    Notizen: In previous work, whaling catch positions were used as a proxy record for the position of the Antarctic sea ice edge and mean sea ice extent greater than the present one spanning 2.8° latitude was postulated to have occurred in the pre-1950s period, compared to extents observed since 1973 from microwave satellite imagery. The previous conclusion of an extended northern latitude for ice extent in the earlier epoch applied only to the January (mid-summer) period. For this summer period, however, there are also possible differences between ship and satellite-derived measurements. Our work showed a consistent summer offset (November-December), with the ship-observed ice edge 1 - 1.5° north of the satellite-derived ice edge. We further reexamine the use of whale catch as an ice edge proxy where agreement was claimed between the satellite ice edge (1973-1987) and the ship whale catch positions. This examination shows that, while there may be a linear correlation between ice edge position and whale catch data, the slope of the line deviates from unity and the ice edge is also further north in the whale catch data than in the satellite data for most latitudes. We compare the historical (direct) record and modern satellite maps of ice edge position accounting for these differences in ship and satellite observations. This comparison shows that only regional perturbations took place earlier, without significant deviations in the mean ice extents, from the pre-1950s to the post-1970s. This conclusion contradicts that previously stated from the analysis of whale catch data that indicated Antarctic sea ice extent changes were circumpolar rather than regional in nature between the two periods.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1751-8369.2003.tb00091.x
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  • 97
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    Digitale Medien
    Interannual variability of dense shelf water salinities in the north-western Barents Sea (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Polar research 22 (2003), S. 0 
    Details
    ISSN: 1751-8369
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Geologie und Paläontologie
    Notizen: The maximum dense shelf water salinity formed during winter in the Svalbard Bank area of the north-western Barents Sea is reconstructed for the period 1952–2000 by analysing the transformation of summer remnants. The variability of 34.7 - 35.4, waters being at the freezing point, is mainly generated by interannual variations in the near surface salinity. On interannual time scales the latter is strongly linked to the sea ice import. In contrast, no correlation of the salinity of the Atlantic Water (AW) throughflow to the Arctic Ocean with the ice import is found. Salinities of both the dense shelf water site in the north-west Barents Sea and the north-eastward AW throughflow show a long term decrease, which can partly be explained by a less saline inflow of AW from the Norwegian Sea. The unusually low dense water salinities in the north-west Barents Sea during the 1990s appear to have a different origin, consistent with a response to oceanic heat advection and decreasing sea ice extent.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1751-8369.2003.tb00096.x
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  • 98
    Digitale Medien
    Digitale Medien
    Sea ice extent and the global climate system (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Polar research 22 (2003), S. 0 
    Details
    ISSN: 1751-8369
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Geologie und Paläontologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1751-8369.2003.tb00088.x
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  • 99
    Digitale Medien
    Digitale Medien
    Variability and climate sensitivity of fast ice extent in the north-eastern Kara Sea (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Polar research 22 (2003), S. 0 
    Details
    ISSN: 1751-8369
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Geologie und Paläontologie
    Notizen: This work investigates the temporal and spatial variation of shore-fast ice extent in the north-eastern part of the Kara Sea during 1953-1990 and its sensitivity to interannual variability of the regional climate. The area of fast ice in spring months shows a bimodal distribution. This indicates the existence of two different regimes of fast ice formation driven by the system of prevailing winds. The westward wind transport during the cold season gives larger fast ice extent while the eastward wind transport suppresses the expansion of fast ice. There is a significant correlation (ca. −0.55) between the average winter temperature and the area of fast ice. Linear trends for time records of shore-fast ice area in spring show a decrease during 1953-1990. This decrease is most pronounced in April: the mean fast ice area in April is 12% lower in 1988-1990 compared to 1953-55. A comparison of fast ice regimes for two particular years–1979 and 1985–revealed a significant influence of cyclone activity on fast ice development over the course of the cold season. It is shown that partial break-ups of fast ice in spring 1985 are associated with the passage of cyclones across the area of fast ice.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1751-8369.2003.tb00092.x
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  • 100
    Digitale Medien
    Digitale Medien
    High resolution simulations of Arctic sea ice, 1979–1993 (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Polar research 22 (2003), S. 0 
    Details
    ISSN: 1751-8369
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geographie , Geologie und Paläontologie
    Notizen: To evaluate improvements in modelling Arctic sea ice, we compare results from two regional models at 1/12° horizontal resolution. The first is a coupled ice-ocean model of the Arctic Ocean, consisting of an ocean model (adapted from the Parallel Ocean Program, Los Alamos National Laboratory [LANL]) and the “old” sea ice model. The second model uses the same grid but consists of an improved “new” sea ice model (LANL/CICE) with a simple ocean mixed layer. Both models are forced with European Centre for Medium-range Weather Forecasts reanalysis data for 1979–1993. A comparison of the two sea ice models focuses on the winter of 1987 to emphasize the internal ice stress and to minimize biases towards a particular Arctic climate regime. The “new” sea ice model gives improved ice deformation and drift fields. These improvements are associated at least in part with the multi-category representation of the ice thickness distribution and more realistic parameterization of the ice strength. Long, narrow features in ice divergence and shear fields resemble those observed in SAR imagery, except that their average width is overestimated, possibly due to insufficient horizontal resolution. We also compare the mean sea ice drift and its decadal variability in two “old” sea ice models at different horizontal resolutions: 18-km and 9-km. We find no significant change in ice drift between the two models, except in areas of significant ice-ocean interactions due to more realistic ocean currents and water mass properties in the 9-km model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1751-8369.2003.tb00097.x
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