Approximation of box dimension of attractors using the subdivision algorithm

In this paper we use the subdivision algorithm to approximate the box dimension of attractors of dynamical systems. Although in theory the subdivision algorithm provides a covering of the attractor with boxes of arbitrarily small diameter, in practice we have to overcome two obstructions: (1) ensure that the covering is (almost) minimal and (2) enhance the speed of convergence to the box dimension. We solve both problems and apply our results to the Hénon, Lorenz, Rössler and Chua attractors. The method suggested in this paper uses information from several subdivision steps and converges to the box dimension much faster than the expression in the definition of the box dimension which uses only one covering of the attractor with boxes of a prescribed diameter.     

Pattern matching in trees and nets

Summary Rational patterns are used to specify recognizable tree languages. It is shown that, given a rational patternp and a treet, one can decide inO(¦p¦·¦t¦) steps whether there is some match ofp int. Problems of this kind generalized to forests or nets are shown to be NP-complete.     

Outlook for the global economy

The end of the 1970s also brought to a close a growth phase of the world economy which had lasted more than 20 years and been interrupted only by relatively mild reverses. Although, after a recession of somewhat longer than 2 years, the preconditions have now improved for a return to the path of economic recovery, at least in most industrial countries, there is no cause for an excessive measure of optimism. Due to their high mountains of debt to other nations, a majority of the large newly emerging industrial countries (the so-called threshold nations) and of the developing countries will be forced to assign first priority to an improvement in their balances of payments over the next few years and will therefore largely fail to act as additional customers for foreign goods. In many industrial countries—again as a result of voluminous indebted-ness—narrow limits have been placed on an expansive economic policy course. Besides, the markets served by these nations exhibit a high degree of saturation. In such an environment, the best growth prospects are held by those industries which succeed in creating new requirements and demands on their traditional markets. This is one of the principal reasons why innovation will play an even more important part in the future than it has already played in the past. It can be fairly estimated that the consumer goods industries and the service sector will develop more favorably within the span of the next 12–18 months than the capital goods industries. From a geographic viewpoint it can be assumed on the basis of the existing evidence that during this period economic performance will be stronger in the USA and Japan than in Western Europe. Prospects for an economic comeback in Europe are best in Great Britain, the Federal Republic of Germany and in Italy.     

Rapid, cultivation-independent assessment of microbial viability in drinking water

Fast and accurate monitoring of chemical and microbiological parameters in drinking water is essential to safeguard the consumer and to improve the understanding of treatment and distribution systems. However, most water utilities and drinking water guidelines still rely solely on time-requiring heterotrophic plate counts (HPC) and plating for faecal indicator bacteria as regular microbiological control parameters. The recent development of relative simple bench-top flow cytometers has made rapid and quantitative analysis of cultivation-independent microbial parameters more feasible than ever before. Here we present a study using a combination of cultivation-independent methods including fluorescence staining (for membrane integrity, membrane potential and esterase activity) combined with flow cytometry and total adenosine tri-phosphate (ATP) measurements, to assess microbial viability in drinking water. We have applied the methods to different drinking water samples including non-chlorinated household tap water, untreated natural spring water, and commercially available bottled water. We conclude that the esterase-positive cell fraction, the total ATP values and the high nucleic acid (HNA) bacterial fraction (from SYBR((R)) Green I staining) were most representative of the active/viable population in all of the water samples. These rapid methods present an alternative way to assess the general microbial quality of drinking water as well as specific events that can occur during treatment and distribution, with equal application possibilities in research and routine analysis.     

Cinchona-modified platinum catalysts: from ligand acceleration to technical processes

This Account records work carried out in our laboratories during the last 2 decades in the field of enantioselective heterogeneous hydrogenation. Of particular interest was Orito's catalytic system, platinum catalysts modified with cinchona alkaloids for the hydrogenation of activated ketones. Described are the development of the optimal platinum catalyst and modifier and the expansion of the scope of the catalyst. Kinetic studies aimed at understanding the mode of action of the catalyst revealed that the cinchona modifier not only renders the catalyst enantioselective but strongly accelerates the hydrogenation. This was the first case of ligand acceleration with a heterogeneous catalytic system. Finally, a number of industrial processes are summarized with the enantioselective hydrogenation of various alpha-keto esters as a key step.     

Robotic manufacturing of near-net-shape components utilizing stereo imaging and reconfigurable tooling

A process is described to acquire geometrical data of the target object and to utilize it to rapidly create a near-net-shape component with flexible tooling system. The topological data acquisition of the object is made possible using a robot-assisted stereo-imaging technique. Stereo-image data is translated into CAD data, and subsequently the geometric data constitutes the basis for the path planning for the tooling process. A novel, rapidly reconfigurable tooling system and tool forming technology is employed by which a six-axis robotic arm is used to shape a discretized vacuum surface. Pre-heated thermoplastic sheets are formed over the shaped vacuum tool to generate near-net-shape parts. The parts may be trimmed and used as the final component or they may be used as molds for subsequent fabrication of composite components. We demonstrate the process first in the context of an abstract reference part. One of the many applications envisaged using this process is the manufacture of custom-made braces, masks, and guards for use in healthcare products. A patient intervention can have their features acquired using stereo imaging and have corrective measures incorporated into the product prior to manufacturing. Since the geometrical data acquisition process does not require physical contact, the method can be used for patients having epidermal or skeletal damage. Furthermore, employing the rapidly reconfigurable tooling technology will significantly reduce the process cycle time and permit complete customization, benefiting the patient with a quicker and more effective administration of medical assistance. The healthcare context of the proposed integrated process is demonstrated with the manufacture of an orthopedic component with personalized fit.     

TiCl4 and LiClO4 promoted Additions of O-Silylketene Acetals to Chiral β-Formyl Esters

Lewis acid promoted additions of O-silylketene acetals 1a and 1b to β-formyl ester 2 furnished γ-lactones 3a and 3b . Employing TiCl₄ as promotor chelate control leads to moderate or excellent trans selectivity, whereas LiClO4 as Lewis acid did not induce appreciable diastereoselectivity.     

A non-contact, thermally-driven buckling delamination test to measure interfacial fracture toughness of thin film systems

Interfacial fracture toughness measurements of thin film-substrate systems are of importance in many applications. In the microelectronics industry, the interfacial adhesion between the dielectric-barrier-metal layers on a semiconductor chip is critical for chip reliability. In this paper, we propose a thermally-driven patterned buckling delamination test that does not use a pre-existing weak interface. The test relies on causing a patterned film to debond from its substrate by inducing a compressive stress due to heating of the film on a thick silicon substrate. The compressive stress causes the film to buckle and debond from the substrate. A model for the propagation of the buckling-induced debond is then developed to estimate interfacial fracture toughness. The efficacy of the thermally-driven buckling test is demonstrated on a model Al/SU8/Si film-substrate system wherein the Al film debonds along its interface to SU8. The interfacial toughness of the Al/SU8 interface is estimated using the proposed test and is compared to the toughness for the same system obtained using an alternative test with a weakened interface to validate the developed elastic-plastic model for buckling-induced debond propagation.