ALBERT

Notes: This paper examines how companies can achieve competitive advantage by fitting their business strategies to the way in which new technology implementation is managed. In particular, the inter-relationship between strategy, technology and performance is examined. Five strategic types and seven types of technological objectives were used to find combinations which were associated with high performance. It was found that companies pursuing a prospector strategy (a strategy based on product innovation) combined with technological objectives emphasizing marketing, image and technical development were the highest performing group of companies. The lowest performing companies were those where strategy was dominated by price competition.The general conclusion of the paper is that, in order to achieve competitive advantage, companies need to see technology objectives as an inherent part of strategy. The study was carried out on a sample of twenty companies within the polymer processing industry, but the findings should be applicable to companies in other industries, and particularly to smaller companies.

Notes: High concentrations of dissolved iron in ground water of coastal plain or alluvial aquifers contribute to the biofouling of public supply wells for which treatment and remediation is costly. Many of these aquifers, however, contain zones in which microbial sulfate reduction and the associated precipitation of iron-sulfide minerals decreases iron mobility. The principal water- bearing aquifer (Magothy Aquifer of Cretaceous age) hi Suffolk County, New York, contains localized sulfate-redudng zones hi and near lignite deposits, which generally are associated with clay lenses. Microbial analyses of core samples amended with [14C]-acetate indicate that microbial sulfate reduction is the predominant terminal-electron-accepting process (TEAP) in poorly permeable, lignite-rich sediments at shallow depths and near the ground water divide. The sulfate-reducing zones are characterized by abundant lignite and iron-sulfide minerals, low concentrations of Fe(III) oxyhydroxides, and by proximity to clay lenses that contain pore water with relatively high concentrations of sulfate and dissolved organic carbon. The low permeability of these zones and, hence, the long residence time of ground water within them, permit the preservation and (or) allow the formation of iron-sulfide minerals, including pyrite and marcasite. Both sulfate-reducing bacteria (SRB) and iron-reducing bacteria (IRB) are present beneath and beyond the shallow sulfate-reducing zones. A unique Fe(HI)-reducing organism, MD-612, was found in core sediments from a depth of 187 m near the southern shore of Long Island. The distribution of poorly permeable, lignite-rich, sulfate-reducing zones with decreased iron concentration is varied within the principal aquifer and accounts for the observed distribution of dissolved sulfate, iron, and iron suit Ides in the aquifer. Locating such zones for the placement of production wells would be difficult, however, because these zones are of limited aerial extent.

Notes: Zeroth-order ray theory is frequently used to calculate synthetic seismograms in media which are both anisotropic and inhomogeneous. One of the principal features of such media is that the polarization vectors of the two quasi-shear (qS) waves are determined by the nature of the anisotropy. Thus, a shear wave entering a region of anisotropy will generally be split into two separate polarizations. Ray theory predicts that these two waves will propagate independently, at different velocities, throughout the anisotropic region. Ray theory solutions also show that in inhomogeneous media, the polarization vectors will rotate along the ray. The rotations of these polarization vectors are strongly influenced by the symmetry and orientation of the anisotropy system, but only weakly depend upon the strength of the anisotropy. In contrast, in isotropic media the polarization of S-waves is determined from the initial conditions and only varies slowly due to the ray curvature. The polarization only changes in the ray direction and at any point does not rotate about the ray.In this paper we show that in the limit of infinitely weak anisotropy, solutions calculated using ray theory in anisotropic media conflict with the known results calculated for a similar isotropic medium. We show this fundamental breakdown in ray theory occurs because coupling between the qS waves is ignored in the zeroth approximation. Thus, the isotropic limit is not equivalent to the high-frequency limit of anisotropic ray theory. The coupling is particularly important in weakly anisotropic media, where the qS velocities are similar, but the same effect is still present in media exhibiting stronger anisotropy. This coupling must be taken into account when calculating waveforms.We show that this coupling may be modelled by treating the ‘error’ terms, produced by substituting a zeroth-order ray theory Green's function into the wave equation, as source terms distributed throughout the medium. For weakly anisotropic media where the qS ray paths are similar, this volume integral may be simplified using perturbation and asymptotic methods and evaluated as a simple integral along the ray path. In the isotropic limit this expression correctly describes the polarization of shear waves along the ray. This integral is easy to compute, requiring only quantities already used in ray tracing and traveltime calculations. A prior knowledge of the location, or even the existence of kiss, intersection, point or other singularities along the ray path, is not required for the method to give accurate results. We present some numerical examples for some simple cases previously investigated by less general or more expensive techniques.

Notes: Recirculating wells are increasingly being used for ground water remediation and aquifer characterization investigations. Determination of flow rate is required for proper design and spacing of recirculation wells. The measurement of flow rate, however, can be difficult using standard equipment. To overcome some of the flow measurement problems associated with more common measurement systems, a new device in the form of a downhole weir was developed for recirculating wells that use a two-casing design. The weir was designed to measure flow rates between 10 and 40 gpm. In this flow range, the weir had an accuracy of ±2.8 gpm. This accuracy may be improved with some modifications.

Notes: Changes in color due to thermal pasteurization of two cultivars of red grapefruit juice were studied. Juices were pasteurized at 91°C using a plate heat exchanger. Apparently, thermal pasteurization changed all three color parameters (CIE L*, a*, b*) in the juice, causing a slight color shift towards lighter and brighter. Thermal pasteurization especially affected CIE b* value and chroma in juice. The reflectance spectrum in the visible region (400 nm to 700 nm) clearly showed changes in spectral distribution of light reflected from juice after pasteurization. There were no changes (P〉0.05) in major carotenoid pigments (β-carotene and lycopene) in the juices after pasteurization.

Notes: The primary purpose of this paper is to study the accuracy with which two single scattering approximate methods model the propagation of elastic waves in media containing complicated structure. The modelling methods we shall examine are the (Conventional) Born approximation, and the Generalized Born approximation. The first of these methods is in wide-spread use in seismology for both forward and inverse modelling in acoustic and elastic media. The Generalized Born method has been introduced more recently for forward-modelling applications in both acoustic and elastic media.A secondary aim of this paper is to attempt to better understand the relationship between the characteristics of the model, (e.g. the spatial variation of the seismic-wave impedances and velocities), and the characteristics of the recorded seismograms (e.g. fluctuations in traveltimes, amplitudes and power spectra).Previous studies of the accuracy of approximate methods have usually been of one of two types; either analytic, where the relative magnitude of the terms kept in the approximate solution and those neglected are compared, or numerical comparisons based on simple canonical models, such as point scatterers or interfaces, for which exact analytic solutions are known. Neither of these approaches yield completely satisfactory results. In this study we take advantage of recent advances in computer technology which allow us to generate finite difference results for realistic, relatively small 2-D elastic models. By realistic we mean a model which contains a degree of complexity similar to that likely to be found in the Earth. These finite difference results, which we treat as ‘exact’ solutions, may then be compared with the approximate results in both the time and frequency domains to give an indication of the accuracy of these approximations.These models are generated as realizations of Gaussian or Exponential autocorrelation functions and are specified on a rectangular grid. The models examined may be catagorized into two groups. In one, the ‘impedance’ models, the P- and S-wave velocities are kept fixed and the P- and S-wave impedances vary with position. In the other, the ‘velocity’ models, the P & S wave impedances are kept fixed but the P and S-wave velocities vary (the ratio of P to S-wave velocity is constant in every example shown). The results may be summarized by saying that in the impedance models the scattering is weak and the approximate solutions do an adequate job of modelling wave propagation. In the velocity models, however, the scattering is strong and neither of the approximate solutions model the scattering very well. The Generalized Born method, however, does significantly better than the Conventional Born approach.

Notes: It is well known that when a seismic wave propagates through an elastic medium with gradients in the parameters which describe it (e.g. slowness and density), energy is scattered from the incident wave generating low-frequency partial reflections. Many approximate solutions to the wave equation, e.g. geometrical ray theory (GRT), Maslov theory and Gaussian beams, do not model these signals. The problem of describing partial reflections in 1-D media has been extensively studied in the seismic literature and considerable progress has been made using iterative techniques based on WKBJ, Airy or Langer type ansätze. In this paper we derive a first-order scattering formalism to describe partial reflections in 3-D media. The correction term describing the scattered energy is developed as a volume integral over terms dependent upon the first spatial derivatives (gradients) of the parameters describing the medium and the solution. The relationship we derive could, in principle, be used as the basis for an iterative scheme but the computational expense, particularly for elastic media, will usually prohibit this approach. The result we obtain is closely related to the usual Born approximation, but differs in that the scattering term is not derived from a perturbation to a background model, but rather from the error in an approximate Green's function. We examine analytically the relationship between the results produced by the new formalism and the usual Born approximation for a medium which has no long-wavelength heterogeneities. We show that in such a case the two methods agree approximately as expected, but that in a media with heterogeneities of all wavelengths the new gradient scattering formalism is superior. We establish analytically the connection between the formalism developed here and the iterative approach based on the WKBJ solution which has been used previously in 1-D media. Numerical examples are shown to illustrate the examples discussed.

Notes: Ray perturbation theory and the Born approximation have both been used extensively in seismological studies to describe the effects of a slowness perturbation on body and surface wavefields. The relationship between the expressions for the perturbed wavefield calculated using the two methods is investigated here. Using the symplectic symmetry of the ray equations we demonstrate the agreement, in the far field, of the two methods to first order in the slowness perturbation and to leading order in the asymptotic ray series. Thus it is shown that geometrical ray effects, like the traveltime perturbation, ray bending and focusing, are contained within the Born scattering formalism, provided these effects are small. The propagator formalism used to present the results is sufficiently general to include body and surface waves with a smoothly varying inhomogeneous elastic reference medium.

Notes: [Auszug] To the editor—Soldan et al. report an increased IgM response to HHV-6 early antigen (p41/38) and detection of serum HHV-6 DNA in relapsing-remitting MS1 and, confirming the work of Challoner et al.2, propose an association between HHV-6 and the etiology and pathogenesis of MS. We urge caution ...