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Selected AbstractsResponse of a double-wedge base-isolation deviceEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 13 2004J. Enrique Luco Abstract A novel base-isolation device is described and its performance is compared with that of a friction pendulum bearing. In its simplest form, the device consists of two wedges sliding on a horizontal plane in opposite directions and constrained from retreating by ratchets or bilinear dampers. The superstructure rests at the intersection of the two wedges. For a sufficiently large horizontal acceleration of the base, the structure starts to move up the inclined plane of one of the wedges, which remains fixed while the second wedge is slaved to follow the structure. As the direction of the base acceleration reverses, the process is reversed and the structure starts to climb on the second inclined plane while the first wedge follows. The overall result is that the horizontal acceleration of the structure is reduced with respect to that of the base and that kinetic energy associated with horizontal velocities is systematically transformed into potential energy. In the case of motion in a vertical plane, the device has the following advantages over a friction pendulum: (i) the sliding surface is linear instead of curved, (ii) kinetic energy is systematically transformed into potential energy during the strong ground motion, and (iii) the device is slowly self-centering. Copyright © 2004 John Wiley & Sons, Ltd. [source] WITHIN-HOST POPULATION DYNAMICS AND THE EVOLUTION OF MICROPARASITES IN A HETEROGENEOUS HOST POPULATIONEVOLUTION, Issue 2 2002Vitaly V. Ganusov Abstract Why do parasites harm their hosts? The general understanding is that if the transmission rate and virulence of a parasite are linked, then the parasite must harm its host to maximize its transmission. The exact nature of such trade-offs remains largely unclear, but for vertebrate hosts it probably involves interactions between a microparasite and the host immune system. Previous results have suggested that in a homogeneous host population in the absence of super- or coinfection, within-host dynamics lead to selection of the parasite with an intermediate growth rate that is just being controlled by the immune system before it kills the host (Antia et al. 1994). In this paper, we examine how this result changes when heterogeneity is introduced to the host population. We incorporate the simplest form of heterogeneity,random heterogeneity in the parameters describing the size of the initial parasite inoculum, the immune response of the host, and the lethal density at which the parasite kills the host. We find that the general conclusion of the previous model holds: parasites evolve some intermediate growth rate. However, in contrast with the generally accepted view, we find that virulence (measured by the case mortality or the rate of parasite-induced host mortality) increases with heterogeneity. Finally, we link the within-host and between-host dynamics of parasites. We show how the parameters for epidemiological spread of the disease can be estimated from the within-host dynamics, and in doing so examine the way in which trade-offs between these epidemiological parameters arise as a consequence of the interaction of the parasite and the immune response of the host. [source] Multiple model adaptive control with safe switchingINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 5 2001Brian D. O. Anderson Abstract The purpose of this paper is to marry the two concepts of multiple model adaptive control and safe adaptive control. In its simplest form, multiple model adaptive control involves a supervisor switching among one of a finite number of controllers as more is learnt about the plant, until one of the controllers is finally selected and remains unchanged. Safe adaptive control is concerned with ensuring that when the controller is changed in an adaptive control algorithm, the frozen plant,controller combination is never (closed-loop) unstable. This is a non-trivial task since by definition of an adaptive control problem, the plant is not fully known. The proposed solution method involves a frequency-dependent performance measure and employs the Vinnicombe metric. The resulting safe switching guarantees depend on the extent to which a closed-loop transfer function can be accurately identified. Copyright © 2001 John Wiley & Sons, Ltd. [source] Kinetics of separating multicomponent mixtures by nondispersive solvent extraction: Ni and CdAICHE JOURNAL, Issue 4 2001Inmaculada Ortiz A model for nonsteady metals separation using nondispersive solvent extraction presented explicitly accounts for selective separation of multicomponent solutions and concentration of separated components in a back-extraction phase. The separation process comprises extraction and back-extraction steps carried out in two different hollow-fiber modules, connected through the organic phase, together with three homogenization tanks. The model is based on a set of coupled differential equations describing mass balances of metallic solutes in the fluid phases. To be applied in its simplest form, it requires the knowledge of three characteristic parameters, two parameters related to the chemical reactions, and one mass-transport parameter. The latter describes the mass-transport rate through pores of the hollow-fiber membrane filled with the organic phase. The mathematical model was checked against the kinetic results of the separation of Cd/Ni mixtures working with high-concentration solutions and obtaining the characteristic parameters of this system. [source] The use of micro-Raman spectroscopy in architectural paint analysisJOURNAL OF RAMAN SPECTROSCOPY, Issue 8-9 2004E. Kendix Abstract Architectural paint analysis is an important technique for establishing the palette of historical paint colours, and reconstructing how a room or a facade might have looked at an earlier time. In its simplest form, it has often been achieved by using paint scrapes, which involves revealing a stepped sequence of layers of paint using a blade or solvents. Cross-sections are used as an alternative to, or in combination with, scrapes. Mounted cross-sections can be examined by optical microscopy. Accumulated layers of paint, wallpaper or other applied decorative finishes can be defined from their textures and colours. Knowledge of the identity of the components in paint layers can be used to reconstruct a certain paint and also to date the paint layers. It is demonstrated that micro-Raman spectroscopy combined with optical microscopy and low-vacuum scanning electron microscopy,energy-dispersive spectrometry are versatile tools for the characterization of pigments and fillers in cross-sections from architectural decorations. The paper gives an example of the examination of an interior decoration from a historical building. Copyright © 2004 John Wiley & Sons, Ltd. [source] A new definition of lifeCHIRALITY, Issue 3 2009James D. Carroll Abstract Chirality is often glossed over in theoretical or experimental discussions concerning the origin of life, but the ubiquity of homochiral building blocks in known biological systems demands explanation. Information theory can provide a quantitative framework for understanding the role of chirality in biology. Here I show how conclusions derived from information theory, in particular the concept of equivocation, can explain not only why chiral building blocks are necessary in living systems but also why a homochiral set of building blocks is necessary. These results lead to a new definition of life, and to the conclusion that the simplest form of life exists in the form of self-amplifying, autocatalytic reactions such as the Soai reaction. Chirality, 2009. © 2008 Wiley-Liss, Inc. [source] Catalyzing "Hot" Reactions: Enzymes from Hyperthermophilic ArchaeaTHE CHEMICAL RECORD, Issue 3 2002Tadayuki Imanaka Abstract We reflect on some of our studies on the hyperthermophilic archaeon, Thermococcus kodakaraensis KOD1 and its enzymes. The strain can grow at temperatures up to the boiling point and also represents one of the simplest forms of life. As expected, all enzymes displayed remarkable thermostability, and we have determined some of the basic principles that govern this feature. To our delight, many of the enzymes exhibited unique biochemical properties and novel structures not found in mesophilic proteins. Here, we focus on a few enzymes that are useful in application, and whose three-dimensional structures are characteristic of thermostable enzymes. © 2002 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 2: 149,163, 2002: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.10023 [source] Theory & Methods: Data Sharpening for Hazard Rate EstimationAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 3 2002Gerda Claeskens Data sharpening is a general tool for enhancing the performance of statistical estimators, by altering the data before substituting them into conventional methods. In one of the simplest forms of data sharpening, available for curve estimation, an explicit empirical transformation is used to alter the data. The attraction of this approach is diminished, however, if the formula has to be altered for each different application. For example, one could expect the formula for use in hazard rate estimation to differ from that for straight density estimation, since a hazard rate is a ratio,type functional of a density. This paper shows that, in fact, identical data transformations can be used in each case, regardless of whether the data involve censoring. This dramatically simplifies the application of data sharpening to problems involving hazard rate estimation, and makes data sharpening attractive. [source] | |||||||||||||