HOLE OF THE JFTOT IN AVIATION FUEL STABILITY RESEARCH

The Jet Fuel Thermal Oxidation Tester (JFTOT), normally operated under standard conditions required by fuel specifications for qualification purposes, can also be used under a wider range of operating conditions to provide research data on thermal stability of aviation fuels. Examples of some typical research investigations are given in the paper, covering the effects of olefins, nitrogen, sulphur, cracked stocks and metallic copper on high temperature stability properties of various fuels. The work described was carried out in the UK research laboratories of BP, Esso and Shell oil companies, under partial funding of the Ministry of Defence.

When used in the research mode, several shortcomings of the JFTOT become evident, particularly in the areas of tube deposit assessment, tube surface metallurgy, and effectiveness in simulating aircraft fuel system operating conditions. Improvements are proposed to overcome these shortcomings - namely measuring tube deposit weight quantitatively by carbon burnoff; utilising stainless steel instead of aluminium heater tubes at high test temperatures; and developing a capillary tube heater section to generate turbulent fuel flow conditions.     

Right ventricular radiofrequency ablation of ventricular tachycardia after myocardial infarction

Radiofrequency transcatheter ablation of ventricular tachycardia in the setting of a prior myocardial infarction is typically performed with application of energy to the left ventricular endocardium. In this article, two cases are described in which successful radiofrequency transcatheter ablation of ventricular tachycardia occurred with energy delivery to the right ventricular septum after failed ablation attempts from the left ventricle. Both patients had tachycardias with a left bundle branch block morphology and markedly presystolic activity recorded from the right ventricular septum. Right ventricular septal activation mapping during ventricular tachycardia should be performed in patients with left bundle branch block tachycardia morphology and coronary artery disease to maximize efficacy of the catheter ablation procedure.     

Alternative techniques for the clinical assessment of foot pronation

It has been known for decades that MHC genes play a critical role in the cellular immune response, but only recent research has provided a better understanding of how these molecules might affect mate choice. Original studies in inbred mouse strains revealed that mate choice was influenced by MHC dissimilarity. Detection of MHC differences between individuals in these experiments was related to olfactory cues, primarily in urine. Recent studies in humans have shown an analogous picture of MHC-based mating. Taken together, these findings could support either the hypothesis of MHC-based inbreeding avoidance or the hypothesis of MHC-related avoidance of reproductive failure, since studies in mice, humans and pigtailed macaques have shown that parental sharing of certain MHC alleles correlates with frequent spontaneous abortion or prolonged intergestational intervals. Data from many mammalian species clearly demonstrate that reproductive failure occurs as a result of inbreeding. Therefore, MHC similarity might serve as an indicator of genome-wide relatedness. In contrast, increased fitness due to the presence of individual MHC alleles in a pathogenic environment could explain MHC-based selection of currently good genes. Specifically, the physical condition of long-living animals depends on the ability to respond to immunological challenge and an individual's MHC alleles determine the response, since, unlike the T cell receptors, MHC alleles are not somatically recombined. Therefore, sexual selection of condition-dependent traits during mate choice could be used to select successful MHC alleles, thereby providing offspring with a higher relative immunity in their pathogenic environment.     

The LIGA technique and its potential for microsystems-a survey

The LIGA technique, which is being developed at the Research Center Karlsruhe, offers the possibility to manufacture microstructures with arbitrary lateral geometry, lateral dimensions down to below 1 μm and aspect ratios up to 500 from a variety of materials (metals, plastics, and ceramics). The basic steps of X-ray lithography, electroplating, and plastic molding, are briefly described. Examples of applications of the LIGA technique are: optical components (high performance microspectrometer), mechanical components (acceleration sensor with integrated temperature compensation), and fluidic components (micropumps) which are presented and discussed. Microcomponents will be of limited interest in the future if it will not be possible to integrate them into microsystems. Microsystems must be more powerful than the sum total of their components. This is discussed in the final chapter of this article     

Microwave Cavity Perturbation as a Tool for Laboratory In Situ Measurement of the Oxidation State of Three Way Catalysts

Three-way catalyst-based automotive exhaust gas aftertreatment is of high importance to meet today’s emission standards. To determine in situ the oxygen loading state of three-way catalysts, a microwave cavity perturbation method is used. In this study, it is investigated whether this measurement setup that had originally been described for full-sized catalysts can be transferred to a lab test bench using cores of 1″ diameter. The initial tests were successful and a high correlation between the oxygen loading degree dependent resonance frequency and the conversion was found. As an application example of the new in situ characterization technique, the steady state degree of oxidation of a three way catalyst was measured as a function of the exhaust stoichiometry. The experimental results are compared with the prediction of a recently published improved kinetic model that takes into account the oxidation of reduced ceria by H₂O and CO₂. It is shown that the experimental observations agree very well with this improved model. This result provides evidence that under typical operating conditions, the degree of oxidation of the three way catalyst is controlled by equilibrium effects.     

Matching large color differences with achromatic and chromatic surrounds

A color-difference-matching experiment was carried out using a computer-interfaced video-display system. Two reference color stimuli (i) and (j), and one test stimulus (i,j) surrounded by a large achromatic or chromatic stimulus were presented on the video screen. An observer was asked to adjust the test stimulus until he perceived it to have a color precisely “half way” between the colors of the given reference stimuli. A satisfactory half-way color was the one that produced perceptually equal color differences between (i) and (i,j) and (j) and (i,j) and simultaneously made these color differences as small as possible. Although the given color difference between the test stimuli (i) and (j) was generally quite large (100–200 just-perceptible color-difference steps) with the achromatic surround condition, the color-difference matching required to obtain the desired half-way color did not present any serious difficulties to the observer. The uncertainty of the chromaticity point of the half-way color was established by an ellipse of small to moderate size surrounding the mean chromaticity setting. The orientation and shape of the uncertainty ellipse was comparable with the orientation and shape of uncertainty ellipses obtained by other investigators studying color-difference matching involving much smaller color differences. The unexpected and noteworthy result of the present study lies in the location of the chromaticity point of (i,j) relative to those of (i) and (j) as a function of surround color. The location of (i,j) depends on the saturation of the surround stimulus but not its hue. Some speculative explanations of the observed results are offered.     

Compositional message sequence charts

A message sequence chart (MSC) is a standard notation for describing the interaction between communicating objects. It is popular among the designers of communication protocols. MSCs enjoy both a visual and a textual representation. High-level MSCs (HMSCs) allow specifying infinite scenarios and different choices. Specifically, an HMSC consists of a graph, where each node is a finite MSC with matched send and receive events, and vice versa. In this paper we demonstrate a weakness of HMSCs, which disallows one to model certain interactions. We will show, by means of an example, that some simple finite state communication protocol cannot be represented using HMSCs. We then propose an extension to the MSC standard which allows HMSC nodes to include unmatched messages. The corresponding graph notation will be called HCMSC, which stands for high-level Compositional message sequence charts. With the extended framework, we provide an algorithm for automatically constructing an MSC representation for finite state asynchronous message passing protocols.     

Global extensional assertions and local integrity constraints in federated schemata

Integrated access to multiple data sources requires a homogeneous interface provided by a federated schema. Such a federated schema should correctly reflect the semantics of the component schemata of which it is composed. Since the semantics of a database schema is also determined by a set of semantic integrity constraints, a correct schema integration has to deal with integrity constraints existing in the different component schemata. Traditionally, most schema integration approaches solely concentrate on the structural integration of given database schemata. Local integrity constraints are often simply neglected. Their relationship to global extensional assertions, which form the basic integration constraints, are even ignored completely. In this paper, we discuss the impact of global extensional assertions and local integrity constraints on federated schemata. In particular, we point out the correspondence between local integrity constraints and global extensional assertions. The knowledge about the correspondences between the given integrity constraints and extensional assertions can then be utilized for an augmented schema integration process.     

Formation of Mullite from Filled Siloxanes

Monolithic mullite with low sintering shrinkage was synthesized from polymer/filler blendsMthat is, siloxane/alumina (siloxane/Al₂O₃) (and siloxane/aluminum (siloxane/Al)) mixtures. The synthesis was based on a reaction-bonding process of amorphous silica, which formed when the siloxane was oxidized, with Al₂O₃ (or oxidized aluminum filler) at temperatures >1250°C. Thermodynamic calculations were used to calculate the phase composition at equilibrium. Thermoanalytical, infrared-spectroscopic, and microscopic techniques were applied to reveal the microstructural evolution. The corresponding volume changes were used to evaluate the linear shrinkage, based on the quantitative phase assemblage.