Recently it has been shown that the initial stages of bacterial adhesion to a model-surface of sulphated polystyrene can best be described using hydrophobic and electrostatic parameters. In the present study it is tested whether these parameters can generally be applied to predict bacterial adhesion by using (i) glass, as a model for hydrophilic and natural surfaces of silicates and oxides, (ii) polystyrene coated with proteins, as a model for a surface coated with an organic layer, and (iii) river Rhine sediment, as an example of a natural surface. Adhesion to glass was dominated by electrostatic interaction, whereas adhesion to polystyrene coated with various types of proteins depended on the surface characteristics of the bacteria and the type of protein. By relating Van der Waals interactions to hydrophobicity of the interacting species, the adhesion of bacteria to the various surfaces including the river Rhine sediments could be interpreted in terms of the DLVO-theory. It is therefore concluded that the conceptual principles of the DLVO-theory (interplay of Van der Waals and electrostatic interactions) are suitable to describe, at least qualitatively, the initial processes of bacterial adhesion to a wide range of surfaces. 相似文献
A regional gravity study of Honduras was performed as part of a major study of the geothermal resource potential of Honduras. This study was conducted by Los Alamos National Laboratory, in cooperation with the Honduras government. Regional offshore free-air and onshore Bouguer gravity maps, and residual/isostatic gravity maps of Honduras and surrounding regions were produced. From these data several regional crustal and upper mantle models were produced. These models pass through two local geothermal sites, Platanares and San Ignacio. The regional geologic and tectonic implications of the models and their relevance to the geothermal potential of Honduras and to six well known geothermal sites in particular are examined. No obvious regional structures observed in the gravity data can explain the thermal enhancement in general or the specific geothermal sites. More local tectonic or structural conditions must control the distribution of the thermally enhanced areas. 相似文献
Geophysical studies were carried out in Platanares in Western Honduras, as part of an investigation of the geothermal resource potential of Honduras by Los Alamos National Laboratory in cooperation with the Honduran government and the U.S. Geological Survey. Geological and geochemical studies later followed by exploratory bore-holes indicate this area of rugged topography has the best geothermal potential in Honduras. In order to better understand the geology of the area, gravity, audiomagnetotelluric and telluric surveys were carried out. The site is in a graben of Tertiary volcanics and Cretaceous red beds, with numerous hot springs along faults in the center of the graben. Gravity mapped the thickness of low-density tuffs and the position of associated normal faults. It also indicated the presence of persuasive, shallow, highly silicified, high-density tuffs and gravels. The electrical surveys mapped shallow, high-resistivity silicified zones and faults as low-resistivity zones. The red beds below the tuffs are considered to contain the geothermal reservoir, but their maximum thickness could not be determined by these surveys due to the lack of density contrast and the high surface electrical conductivities. Three geologic cross-sections constructed by others have been re-evaluated using gravity modeling and analysis of eletrical anomalies, showing general agreement but in detail significant differences. 相似文献
The variation of elastic lithospheric thickness within the Canadian landmass is determined using the coherence between surface topography and Bouguer gravity anomalies. Estimates of elastic thickness (or, equivalently, rigidity) are derived by minimizing the difference between the observed coherence and that predicted by an isostatic model consisting of a thin elastic plate which is subject to surface and subsurface loading and overlies a fluid substratum (the asthenosphere).
Estimates of the elastic thickness vary from 17–18 km in coastal Labrador and Baffin Island to > 150 km near Lake Winnipeg, Manitoba. A broad correlation exists between lithospheric thickness and age. Exceptions to this correlation are areas of reduced plate thickness in North Atlantic coastal regions where magmatic activity associated with rifting and the formation of a passive margin may have been sufficient to reduce the plate strength but not enough to reset the thermal age of the basement rocks. Areas of greater plate thickness than that predicted by thermal cooling occur in the continental interior and may reflect lithospheric thickening due to the chemical and mechanical effects accompanying continental agglomeration. 相似文献
North American literature on the changing role of the local state these past two decades has been dominated by the view of a transition from urban managerialism to urban entrepreneurialism. Associated with the transition has been the emergence of a New Urban Politics (NUP). Within a political economy framework. the NUP has been rooted in the material redistributive effects of the transition. This paper explores the character of this NUP, as experienced by one British city, and highlights some fundamental differences with the established political economy reading. Our argument, based upon the city of Glasgow, draws attention to two distinctive features. First, the institutional structure of urban governance in Glasgow differs from that of cities in the United States. In Glasgow, it has been the Left controlled local Council which has orchestrated the transition to entrepreneurialism, rather than the North American model of a coalition between local capital and the local state. Secondly, the transition in Glasgow has been marked not by a significant transfer of local state revenue from service provision to local economic development, but by a symbolic reorientation of the local state as marked by the central importance of large place marketing hallmark events. These events represent the city in ways which differ from traditional ‘self’ identities. Consequently, the transition has evoked a political response which has focused upon the symbolic posturing of the local state rather than the material consequences of the shift. In focusing upon local identity, the politics of urban entrepreneurialism in Glasgow points to a dimension of conflict which has received inadequate treatment in accounts of the NUP to date. 相似文献
A new method is introduced for the identification of modal quantities of self-adjoint distributed-parameter systems. The method uses the temporal and spatial orthogonality properties of distributed-parameter systems to form a pseudo-Rayleigh quotient. The stationary values of the pseudo-Rayleigh quotient can be determined by the solution of an eigenvalue problem, where the eigenvalues and eigenfunctions provide the frequencies and natural modes of the distributed-parameter system. By way of formulation, the method is insensitive to zero mean measurement noise and is applicable to continuous as well as discrete systems. Numerical examples are presented in which the modal quantities of a simply-supported beam and a discrete model of a membrane are identified. The results are compared with another modal identification technique, namely, the Ibrahim time domain method. 相似文献