bluuebunny/crossref_metadata_2025 huggingface dataset:
Melatonin and locomotor activity in the fiddler crab Uca pugilator
Authors: Tilden Andrea R. , Shanahan J. Kearney , Khilji Zahra S. , Owen Jeffrey G. , Sterio Thomas W. , Thurston Kristy T.
Published: April 2003

The influence of melatonin on locomotor activity levels was measured in the fiddler crab Uca pugilator. First, activity in untreated, laboratory‐acclimated crabs was measured over 48 hours in a 12L:12D photoperiod; this study showed a nocturnal increase in activity. In eyestalk‐ablated crabs, overall activity was significantly reduced, and no significant activity pattern occurred. Next, crabs were injected with melatonin or saline (controls) at various times during the 12L:12D photoperiod (0900h, 1200h, and twice at 2100h; each trial was separated by 3–4 days) and monitored for 3 hr post‐injection. Control crabs had low activity during early photophase, high at mid‐photophase, increasing activity during the first scotophase trial, and decreasing activity during the second scotophase trial. Melatonin had no significant influence on activity when injected during the early‐photophase activity trough or early‐scotophase activity decline, but significantly increased activity when injected during the mid‐photophase activity peak and early‐scotophase activity incline. Next, crabs were injected during an early scotophase activity trough and monitored throughout the twelve‐hour scotophase. Melatonin did not increase activity until the mid‐scotophase activity increase, approximately 6 hours later, showing that the pharmacological dosage persisted in the crabs' systems and had later effects during the incline and peak of activity but not the trough. Eyestalk‐ablated crabs were injected with melatonin or saline during early photo‐ and scotophase. Melatonin significantly increased activity in the photophase but not the scotophase trial, indicating that the responsiveness to melatonin continues following eyestalk removal, but the timing may not match that of intact crabs. Melatonin may be involved in the transmission of environmental timing information from the eyestalks to locomotor centers in U. pugilator. J. Exp. Zool. 297A:80–87, 2003. © 2003 Wiley‐Liss, Inc.
Synthesis of 14C‐labelled myosmine, [2′‐14C] ‐3‐(1‐pyrrolin‐2‐yl)pyridine
Authors: Tyroller Stefan , Zwickenpflug Wolfgang , Richter Elmar
Published: April 2003

14C‐Labelled myosmine ([2′‐14C]‐3‐(1‐pyrrolin‐2‐yl)pyridine) was synthesized for autoradiography studies starting from [carboxyl‐14C]‐nicotinic acid by initial esterification of the latter in the presence of 1,1,1‐triethoxyethane. Without any purification the ethyl nicotinate formed was directly reacted with N‐vinyl‐2‐pyrrolidinone in the presence of sodium hydride, yielding 14C‐labelled myosmine. The product was purified by silica gel column chromatography. The radiochemical yield was 15% and the specific activity 55.2 mCi/mmol. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and radiolabelling of [123I]‐4‐iodo‐N‐(4‐(4‐(2‐methoxyphenyl)‐piperazin‐1‐yl)butyl)‐benzamide, a potential dopamine D3 antagonist for SPECT studies
Authors: Staelens L. , Dumont F. , De Vos F. , Oltenfreiter R. , Vandecapelle M. , Dierckx R. A. , Slegers G.
Published: April 2003

Schizophrenia is a devastating mental disorder characterized by relapsing psychotic episodes accompanied with emotional, professional and social decline. The classical dopamine hypothesis of schizophrenia postulates that hyperactivity of dopaminergic neurotransmission is responsible for the positive symptoms of the disorder. More exactly hyperactivity of the dopamine D3 receptor system is thought to be involved in the pathology of schizophrenia. Therefore, a new 123I‐labelled compound was developed which may allow in vivo visualization of the D3 receptor by SPECT. [123I]‐4‐iodo‐N‐(4‐(4‐(2‐methoxyphenyl)‐piperazin‐1‐yl)butyl)‐benzamide was synthesized and labelled by electrophilic aromatic substitution of the tributylstannyl derrivative. The radiochemical yield was 82–85% and the specific activity was >2.96 Ci/µmol. Copyright © 2003 John Wiley & Sons, Ltd.
Syntheses of 5‐(2‐radiohaloethyl)‐ and 5‐(2‐radiohalovinyl)‐2′‐ deoxyuridines. Novel types of radiotracer for monitoring cancer gene therapy with PET
Authors: Yu Chung‐Shan , Eisenbarth Joseph , Runz Armin , Weber Klaus , Zeisler Stephan , Oberdorfer Franz
Published: April 2003

Syntheses of 5‐(2‐[18F]fluoroethyl)‐ (1), 5‐(2‐[80Br]bromoethyl)‐ (2), un‐deprotected (E)‐5‐(2‐[18F]fluorovinyl)‐ (3) and (E)‐5‐(2‐[80Br]bromovinyl)‐2′‐deoxyuridines (4) as the tracers for monitoring cancer gene therapy with positron emission tomography were described. Decay corrected radiochemical yield and synthesis time including labeling and HPLC purification from end of bombardment for 1 was 9.5% and 2 hours, respectively; yield and time for 2 was 16% and 2 hours, respectively. Chemical (approximate to radiochemical) yield and time for synthesis of 3 was 7.5% and 7 minutes, respectively. Radiochemical yield and synthesis time including labeling and HPLC purification of an analytical sample of 4 was 60% and 30 minutes, respectively. Both 2 and 4 received the side reactions during HPLC purification, i.e. ring closure and cleavage of glycosidic bond, respectively. Application of 2 and 4 needed to be confirmed by in vitro or in vivo experiments. Radiochemical yield of 1 could be optimized by employing a modified protocol for preparation of its precursor. The preparation of fluorovinyl counterparts had demonstrated the potential utility of the stannane, 3‐tolyl‐3′,5′‐di‐O‐acetyl‐(E)‐5‐(2‐stannylvinyl)‐2′‐deoxyuridine 7. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis of [14C]‐l‐tryptophan and [14C]‐5′‐hydroxy‐l‐tryptophan labeled in the carboxyl group
Authors: Boroda E. , Kański R. , Kańska M.
Published: April 2003

The synthesis of selectively 14C‐labeled l‐tryptophan and its derivative 5‐hydroxy‐l‐tryptophan using chemical and multienzymatic methods is reported. The mixture containing [1‐14C[‐dl‐alanine, indole or 5‐hydroxyindole has been converted to [1‐14C]‐l‐tryptophan or 5′‐hydroxy‐[1‐14C]‐l‐tryptophan, respectively, in a one‐pot multienzymatic reaction using four enzymes: d‐amino acid oxidase, catalase, glutamic‐pyruvic transaminase and tryptophanase. Copyright © 2003 John Wiley & Sons, Ltd.
Preparation of [11C]formaldehyde using a silver‐containing ceramic catalyst
Authors: Roeda D. , Dollé F.
Published: April 2003

A ceramic material, prepared from kaolin doped with silver ions in various concentrations, was evaluated as a catalyst for the conversion of [11C] methanol into [11C]formaldehyde in a gas flow system. Employment of [11C] methanol with a minimized water content, 300 mg of catalyst (20% of silver) at 500°C and a carrier gas flow rate of 40 mL/min resulted in a radiochemical decay‐corrected [11C]formaldehyde yield of 67% relative to [11C]methanol. Wet [11C]methanol under the same conditions gave 54% of [11C] formaldehyde. Copyright © 2003 John Wiley & Sons, Ltd.
Carbon/Carbon Composite Friction Discs for Aerospace
Authors: Buchgraber W.
Published: April 2003

Carbon/carbon friction discs are produced at Newmet Composites (a division of New Metals & Chemicals Ltd.) for flap jam systems in airplanes. They offer excellent mechanical and friction properties. New carbon/carbon composite grades have been developed at Newmet Composites during the last few years. Another material that is used for this applications is bronze. Different material grades and different designs are compared in this paper. The key‐properties discussed are compression strength, flexural strength and friction behaviour. The friction tests were simulating the friction behavior during the application of such discs. Compression tests were made to define the possible application: For the application in the flap jam system the compression strength has to be 207 MPa at the minimum, for other applications this is not necessarily required. A test described briefly in this paper was developed for flexural strength. The flexural strength is not very important during the application, but important when the discs are being handled and built in. It could be shown that both production parameters and design have a significant influence on the performance of carbon/carbon friction discs. These results are needed to define further applications for these materials. Finally the material carbon/carbon is briefly compared with alternative materials.
Sol‐gel derived C‐SiC composites for re‐entry structures
Authors: Haruvy Y. , Liedtke V.
Published: April 2003

Composites of carbon fibers, fabrics, or their precursors as reinforcement, and sol‐gel‐derived silicon carbide as matrix, have been developed, aiming at high‐temperature stable ceramics that can be utilized for re‐entry structures. These composites are produced via the sol‐gel process, starting with a sol‐gel reaction of a mixture of silane precursors.

The sol‐gel‐derived resin is cast onto the reinforcement fibers/fabrics mat (carbon or its precursors) to produce a ‘green’ composite that is being cured. The ‘green’ composite is converted into a C‐SiC composite via a gradual heat‐pressure process under inert atmosphere, during which the organic substituents on the silicon atoms undergo internal oxidative pyrolysis via the schematic reaction: (SiRO3/2)n → SiC + CO2 + H2O

The composition of the resultant silicon‐oxi‐carbide is tailorable via modifying the composition of the sol‐gel reactants. The reinforcement, when made of carbon precursors, is converted into carbon during the heat‐and‐pressure processing as well.

The C‐SiC composites thus derived exhibit superior thermal stability and comparable thermal conductivity, combined with good mechanical strength features and failure resistance, which render them greatly applicable for re‐entry shielding, heat‐exchange pipes, and the like.
Investigation of the Tribological Behaviour of Si3N4 Based Ceramics
Authors: Babcsán Kiss J. , Berkes M. M.
Published: April 2003

Differently prepared Si3N4 based ceramics were examined from different aspects of the tribological behaviour: Mechanical and microstructural characteristics have been studied investigating the possible effect of a post heat‐treatment process on the wearing properties. Vacuum tribometer was used for measuring the wear resistance and friction coefficient of the ceramics. The worn volume of the samples was measured by profilometer. The possible microstructural changes induced by the post heat treatment processes were investigated by scanning electron microscopy. Micro‐hardness measurements have been executed for studying the correlation between the wear resistance and the hardness of the material. Transmission electron microscopy was used for structural examination of ion‐implanted layer of the samples. The results of the complex testing procedure provide facilities for evaluating the effect of the applied post heat‐treatment on the tribological behaviour.
Investigation of the Effect of Fe3O4 Particles on the Interface of Gf‐Pr‐Fa Magnetic Composites
Authors: Dima D. , Andrei G.
Published: April 2003

The aim of this study is to characterize and to assess the quality and performances of a new class of soft magnetic composites, with ferrite additive, used for aircraft‐type instruments as well as in electronic and chemical industries. The ferrite additive introduced in the structure of the composite induces desired magnetic properties and thus improve the quality of the interface. A major structural defect of the organic matrix composite is recognized by the presence of void space, which must be reduced. It was found that the paramagnetic behaviour of the molecules of oxygen could control the scattering of the air bubbles in the mass of the organic matrix. Thus, the ferrite particles introduced in the material mixture play the role of a “vacuum cleaner” which “aspirates” the voids raised on the interface. Moreover, if when producing the composite, an external vibrating magnetic field is active, it could be possible to obtain the scattering of this void space in the mass of the organic matrix. Therefore, it is expected an enhancement of the interface fitness.
Thermal cycling under vacuum and CME evaluation of carbon/epoxy laminates
Authors: Rouquié S. , Lafarie‐Frenot M. C. , Pönninger A. , Costin W.
Published: April 2003

Dealing with the « French Supersonic Aircraft Research Program», thermal cycling tests in four environments, neutral (vacuum, nitrogen) and oxidative (air, oxygen), were performed on carbon/epoxy cross ply laminates [03/903]S. This experimental study was conducted following a local approach through optical and scanning electron microscopy observations and X radiographs and showed a significant effect of the oxygen level on the damage development. Moreover, coefficient of moisture expansion (CME) tests were performed on the same material to characterize the influence of moisture on the sample expansion.
Outgassing Kinetics Testing of Spacecraft Materials
Authors: Rampini R. , Grizzaffi L. , Lobascio C.
Published: April 2003

Solid materials contain impurities from manufacturing/cleaning processes which diffuse (out‐gas) to the exterior during exposure to vacuum, especially at elevated temperature levels. Materials like plastics and resins tend to disintegrate under space conditions. In addition to the above mentioned diffusion process, contaminants adsorbed and absorbed from the environment encountered previously, e.g. during manufacturing, cleaning, integration, test and launch phases, might be desorbed from the surfaces. The released products represent a permanent source of potential contamination.

This paper provides an overview of a research program carried out at the Austrian Research Centers Seibersdorf (ARCS), Aerospace Materials Technology Testhouse (AMTT), by means of the AMTT Sublimation Test Facility to acquire in‐depth knowledge of the outgassing kinetics characteristics of a set of non‐metallic materials, selected by Alenia on the basis of their usage on the International Space Station (ISS) and Scientific Satellites.
Room and high temperature tensile tests on the AA6061/10vol.%Al2O3p and AA7005/20vol.%Al2O3p composites
Authors: Ceschini L. , Morri A. , Cocomazzi R. , Troiani E.
Published: April 2003

Aluminium alloy based Metal Matrix Composites (MMCs), reinforced with ceramic particles such as Al2O3 or SiC, have a number of advantages over conventional aluminium alloys, primarily enhanced stiffness and increased wear resistance. In order to improve the fields of application, fundamental understanding of the relationship between microstructural features and mechanical properties is however required. In this work, the tensile behaviour of two composites based on 6061 and 7005 aluminium alloys, reinforced with Al2O3 particles, at room temperature, at 100°C and at 150°C was studied. The ductility of the composites was found to be much lower than that of the unreinforced alloys, while a significative increase of the elastic modulus and tensile strength was found. Both materials showed a slight decrease of the tensile strength with temperature, while elongation increased. Large particles and clusters of the reinforcement were found to be locations prone to failure in the composite, due to the high stress concentrations, mainly at room temperature. With increasing temperature, the fracture surfaces showed a dimpled appearance with a large amount of plastic deformation of the matrix, indicating that void nucleation, growth and coalescence is the main fracture mechanism.
Non‐destructive Investigation of AlSi7Mg/SiC70p MMCs by means of Acoustic Scanning Microscopy, X‐Ray and Neutron Diffraction
Authors: Göbel U. , Lefranc G. , Degischer H.‐P.
Published: April 2003

Particulate silicon carbide reinforced aluminium matrix composites (Al‐SiC) have a high potential for advanced engineering materials beeing developed for use in traction, automotive, aviation and space applications. Especially high volume composites with up to 70 vol.% reinforcement of silicon carbide particles in a cast AlSi metal matrix (AlSi7Mg/SiC70p) show most interesting characteristics for application in high power electronics (IGBTs). To characterize such MMCs respectively reasons for failure, different non‐destructive material investigations were carried out among them Acoustic Scanning Microscopy, X‐Ray and Neutron Diffraction. Acoustic Scanning Microscopy delivers information about lateral density differences respectively material inhomogeneities integrated over sample thickness. Diffraction methods are used for a non‐destructive evaluation of absolute and phase specific residual stresses, whereas X‐Ray Diffraction provides near surface information (several tens of micrometers). High Energy Synchrotron and Neutron Diffraction on the contrary provide bulk information of several millimeters up to several centimeters. Important for the understanding of the deformation behaviour and dimensional stability is the understanding of the residual stress state and inhomogeneities in the composite and its change under operating conditions respectively under dynamic thermal load.
Spray‐Deposited Al‐Si (Osprey CE) Alloys and their Properties
Authors: Jacobson D. M. , Ogilvy A. J. W.
Published: April 2003

Osprey Metals Ltd. has developed a new family of lightweight, low expansion aluminium‐silicon alloys to suit electronic applications, containing between 30 and 70 wt.% aluminium. They are produced using the Osprey spray deposition process, which achieves homogeneous and isotropic properties. Their advantageous physical characteristics, combining low thermal expansion, high thermal conductivity and low density are particularly suited for packaging electronic circuitry. These CE (controlled expansion) alloys are easy to machine to tight tolerances using standard machine tools and they can be electroplated with gold, silver or nickel finishes without difficulty. This paper focuses on the measurement of mechanical (flexural strength) and thermo‐mechanical properties (CTE, thermal diffusivity and specific heat) of these alloys, carried out in collaboration with AMTT. The property measurements were consistent with those measured previously elsewhere, apart from the CTE values, which deviated significantly and were at variance with values predicted from a rule of mixtures. This discrepancy was resolved in a short follow‐up series of measurements carried out under conditions corresponding more closely to temperature equilibrium.
Thermal and Electrical Conductivity Measurements on Aluminum Foams
Authors: Babcsán N. , Mészáros I. , Hegman N.
Published: April 2003

Metal foams are one of the most interesting types of materials although there is limited information concerning their thermal and electrical conductivity. Closed cell different density Alporas foams are investigated, which has one of the most homogeneous cell size distribution recently. Comparative method has been chosen to determine the thermal conductivity of the samples in the function of the temperature at 30, 100, 200, 300, 400, 500 °C. For measuring the electrical conductivity of aluminium foams a special low frequency eddy current measuring apparatus was used. The ratio of thermal and electrical conductivity was calculated and shown an increasing function by the density of the foams.
Development of High Strength Magnesium Based MMC Reinforced with SiC Particles for Satellite Structure Applications
Authors: Landkof B.
Published: April 2003

The appearance of Metal Matrix Composites has opened a new area in structural design. The possibility of tailoring mechanical properties of structural metals reinforced with particles or fibers into specific spacecraft applications is very appealing. This paper deals with such a MMC, which is based on a magnesium alloy matrix and SiC reinforcement. The technology used is a commercial semi‐solid die‐casting, which promises a cost‐effective solution. The results of the first stage of this research are discussed with a focus on the satellite structure design application. The next steps of this investigation are also presented.
Thermal conductivity of zirconia‐based ceramics for thermal barrier coating
Authors: Leclercq B. , Mévrel R. , Liedtke V. , Hohenauer W.
Published: April 2003

Lowering the thermal conductivity of thermal barrier coatings used to protect blade and vane airfoils represents an important challenge for gas turbine designers and manufacturers. Dense zirconia‐based materials have been prepared by solid state reaction methods to determine their thermal properties up to 1000 °C. Partially stabilised zirconias having a thermal conductivity 40 % lower than the thermal conductivity of the most widely used system (ZrO2‐8wt.%Y2O3) have been obtained.
Microstructure control in precious metal coatings for high temperature applications, obtained by metallorganic chemical vapour deposition
Authors: Gimeno‐Fabra L. , Nizard H. , Benien H. , Vlcek J. , Redjaimia A.
Published: April 2003

In most high temperature applications, efficiency increases with service temperature of the component. Especially in combustion chambers, higher efficiency is translated into less propellant consumption and therefore a lower weight and a reduction of operational cost. In these components, the use of high performance coatings may simultaneously increase the service temperature and decrease its price. From the many available coating processes, Metal organic Chemical Vapour Deposition (MO‐CVD) is one of the few capable of producing coatings of most precious metals in internal surfaces with intricate geometry. Nevertheless the microstructure control of the films is extremely complicated and characterised by the formation of dendrite structures. This morphology eliminates the coating efficiency, as it is not compact. EADS has had the chance to use the research infrastructure of the AMTT in Seibersdorf to characterise the coatings and determine how the transformation from the compact to the non‐compact microstructure takes place. The understanding of this phenomenon should allow us to develop a process able to produce 100 % dense coatings independently of the coating thickness in an industrial scale.
TEM Studies of High Temperature Corrosion Behaviour of TiAl Intermetallics with Surface Modifications
Authors: Du H. L. , Rose S. R. , Xiang Z. D. , Datta P. K. , Li X. Y.
Published: April 2003

The oxidation/sulphidation behaviour of a Ti‐46.7Al‐1.9W‐0.5Si alloy with a TiAl3 diffusion coating was studied in an environment of H2/H2S/H2O at 850oC. The kinetic results demonstrate that the TiAl3 coating significantly increased the high temperature corrosion resistance of Ti‐46.7Al‐1.9W‐0.5Si. The SEM, EDX, XRD and TEM analysis reveals that the formation of an Al2O3 scale on the surface of the TiAl3‐coated sample was responsible for the enhancement of the corroison resistance. The Ti‐46.7Al‐1.9W‐0.5Si alloy was also modified by Nb ion implantation. The Nb ion implanted and as received sampels were subjected to cyclic oxidation in an open air at 800oC. The Nb ion implantation not only increased the oxidation resistance but also substantially improved the adhesion of scale to the substrate.
A phase transition model with the entropy balance
Authors: Bonetti Elena , Frémond Michel
Published: April 2003

This paper deals with a phase transition model in which the energy balance is equivalently rewritten in terms of the entropy balance. The thermodynamical consistence of the model is proved and also under physically meaningful assumptions on the data, existence of a solution is stated for the corresponding initial boundary values problem by a maximum principle. Hence, L1‐arguments yield the uniqueness of the solution and show that it evolves in accordance with thermodynamics and everyday practical properties. Copyright © 2003 John Wiley & Sons, Ltd.
Global and blow‐up solutions for non‐linear degenerate parabolic systems
Authors: Duan Zhi‐wen , Zhou Li
Published: April 2003

In this paper the degenerate parabolic system ut=u(uxx+av). vt=v(vxx+bu) with Dirichlet boundary condition is studied. For $a. b {<} \lambda_{1} (\sqrt {ab} {<} \lambda_{1} {\rm if}\, \alpha_{1} {\neq} \alpha_{2})$, the global existence and the asymptotic behaviour (α1=α2) of solution are analysed. For $a. b \,{>}\, \lambda_{1}\ (\sqrt{ab} {>} \lambda_{1} {\rm if}\, \alpha_{1} {\neq} \alpha_{2})$, the blow‐up time, blow‐up rate and blow‐up set of blow‐up solution are estimated and the asymptotic behaviour of solution near the blow‐up time is discussed by using the ‘energy’ method. Copyright © 2003 John Wiley & Sons, Ltd.
Powerful FE approaches for Pochhammer's dispersion modelling
Authors: Mazúch Tibor
Published: April 2003

Simple and very effective finite element approaches for modelling of the dispersion of torsional, longitudinal and flexural waves propagated in infinite and elastic cylindrical bars (Pochhammer's problem) and hollow cylinders are presented. The approaches allow one to model given problems without using infinite elements and their usage is demonstrated by using dispersion curves, shapes of waves and tables of phase velocities. Comparison of finite element solutions (solved in one task from small‐sized models) with exact solutions shows an excellent agreement. The maximum relative differences among the 20 lowest FEM and analytical phase velocities was less than 0.000015%. The approaches and results hold also for cylinders with finite lengths, simply supported on both ends. Copyright © 2003 John Wiley & Sons, Ltd.
A wavelet‐based method for solving discrete first‐kind Fredholm equations with piecewise constant solutions
Authors: Sánchez‐Ávila C. , Sánchez‐Reíllo R.
Published: April 2003

The inverse problem of finding piecewise constant solutions to discrete Fredholm integral equations of the first kind arises in many applied fields, e.g. in geophysics. This equation is usually an ill‐posed problem when it is considered in a Hilbert space framework, requiring regularization techniques to control arbitrary error amplifications and to get adequate solutions. In this work, we describe an iterative regularizing method for computing piecewise constant solutions to first‐kind discrete Fredholm integral equations. The algorithm involves two main steps at each iteration: (1) approximating the solution using a new signal reconstruction algorithm from its wavelet maxima which involves a previous step of detecting discontinuities by estimation of its local Hölder exponents; and (2) obtaining a regularized solution of the original equation using the a priori knowledge and the above approximation. In order to check the behaviour of the proposed technique, we have carried out a statistical study from a high number of simulations obtaining excellent results. Their comparisons with the results coming from using classical Tikhonov regularization by the multiresolution support, total variation (TV) regularization and piecewise polynomial truncated singular value decomposition (PP‐TSVD) algorithm, serve to illustrate the advantages of the new method. Copyright © 2003 John Wiley & Sons, Ltd.
Steady‐state Kalman filtering with nonstationary noise
Authors: Mäkilä P. M. , Paattilammi J.
Published: April 2003

Infinite‐horizon Kalman filtering is re‐examined for linear discrete‐time systems and generalized to include a class of non‐stationary and non‐ergodic disturbances. This revision is achieved by defining a generalized infinite‐horizon filtering problem using a flexible functional analytic signal description. It is shown that the solution to the generalized filtering problem is equivalent to the solution of the corresponding standard filtering problem with noise covariance matrices having in the generalized problem a different, more general, meaning than in the standard problem. In the generalized problem these covariance matrices are majorizing matrices that have a precise meaning even in the non‐stationary and non‐ergodic signal case. This result justifies in a nice way the wide practice of interpreting the noise covariance matrices in Kalman filtering as design variables. Copyright © 2003 John Wiley & Sons, Ltd.
Incomplete sensitivities and cost function reformulation leading to multi‐criteria investigation of inverse problems
Authors: Cabot A. , Mohammadi B.
Published: April 2003

This paper deals with the application of typical minimization methods based on dynamical systems to the solution of a characteristic inverse problem. The state equation is based on the Burgers equation. The control is meant to achieve a prescribed state distribution and a given shock location. We show how to use incomplete sensitivities during the minimization process. We also show through a redefinition of the cost function that a multi‐criteria problem needs to be considered in inverse problems. This example shows that a correct definition of the minimization problem is crucial and needs to be studied before a direct application of brute force minimization approaches. Copyright © 2003 John Wiley & Sons, Ltd.
Robust disturbance attenuation for discrete‐time active fault tolerant control systems with uncertainties
Authors: Shi Peng , Boukas El Kebir , Nguang Sing Kiong , Guo Xianping
Published: April 2003

The problems of stochastic stability and stochastic disturbance attenuation for a class of linear discrete‐time systems are considered in this paper. The system under study is a state space model possessing two Markovian jump parameters: one is failure process and another is failure detection and isolation scheme. A controller is designed to guarantee the stochastic stability and a disturbance attenuation level. Robustness problems for the above system with norm‐bounded parameter uncertainties are also investigated. It is shown that the uncertain system can be robustly stochastically stabilized and have a robust disturbance attenuation level for all admissible perturbations if a set of coupled Riccati inequalities has solutions. A numerical example is given to show the potential of the proposed technique. Copyright © 2003 John Wiley & Sons, Ltd.
Dynamic ‘back‐off’ analysis: use of piecewise linear approximations
Authors: Figueroa José L. , Desages Alfredo C.
Published: April 2003

The operating point of a process is usually computed by optimizing an objective function, e.g. the profit, subject to some plant characteristics. Typically, the resulting point lies on the boundary of the operating region. At this point, the presence of disturbances can easily cause constraint violations and make the process move to the unfeasible region. Then, it is necessary to move the operating point away into the feasible region by considering the effect that the expected disturbances will have on the operation of the plant. The purpose of this paper is to present an efficient algorithm to modify the operating point in order to keep feasibility (both in steady‐state and along transitory) in the process operation against the disturbances. Copyright © 2003 John Wiley & Sons, Ltd.
Non‐destructive packaging seal strength analysis and leak detection using ultrasonic imaging
Authors: Pascall M. A. , Richtsmeier J. , Riemer J. , Farahbakhsh B.
Published: April 2003

This study investigated the effectiveness of ultrasonic imaging for non‐destructive assessment of seal strength in 335 ml polymeric trays. In the first part of this study, the experimental procedures involved filling sample trays with beef enchilada, then sealing at temperatures of 170–260°C for 5 s at 3 bar. Ultrasonic measurements were conducted using an immersion technique in pulse/echo mode. The captured signal amplitudes of the reflections from the samples were digitized and analysed to construct high‐resolution C‐scan ultrasonic images of the seals. The acquired data were statistically analysed for each sample and used as a basis for comparison with the seal (peel) strength, measured as the energy at break. The energy at break was obtained from destructive peel strength analysis, performed using a tensile testing frame. In the second part of this study, ultrasonic imaging was used to predict the performance of the heat sealer used to fabricate the test trays by comparing the seal quality of each of the four quadrants of the samples trays. This study also investigated the minimum channel leak size that could be detected using this ultrasound system. The results of the peel strength analyses showed that a direct correlation exists between seal strength and sealing temperature (170–227°C). Results of the ultrasonic imaging showed that the statistical scatter in the signal amplitude decreased as the sealing temperature increased. This reduction in the scatter of the signal amplitudes indicated a trend of increasing uniformity in the fusion of the two seal faces. Between 170°C and 193°C, sharp changes in the scatter were observed; however, little change was noted for sealing temperatures greater than 193°C, indicating that 204°C could be a minimum recommended sealing temperature. To confirm this result, a drop test analysis was performed on trays filled with beef enchilada and sealed at temperatures of 170–260°C for 5 s at 3 bar. Results of this drop test confirmed that 204°C was the minimum critical sealing temperature. Based on these results, ultrasonic imaging appeared to offer a promising non‐destructive method for the prediction of seal quality in polymeric trays, sealing equipment monitoring and identification of channel leaks ⩾20 µm in diameter, and is comparable with the more established destructive peel strength analytical method. Copyright © 2003 John Wiley & Sons, Ltd.
Packaging materials for fermented milk, part 2: solute‐induced changes and effects of material polarity and thickness on food quality
Authors: Jansson S. E. A. , Gallet G. , Hefti T. , Karlsson S. , Gedde U. W. , Hedenqvist M. S.
Published: April 2003

This work is a continuation of the application of a developed methodology for the selection of packaging material for a specific food product, in this case the ‘demanding’ food product: fermented milk. The effects of different packaging material parameters on the quality of fermented milk were studied. Food quality after storage was determined as a function of material polarity and pouch thickness by storing the liquid in pouches of different materials. The material polarity was varied by using laminates with polyethylene, poly(ethylene‐co‐vinyl alcohol) with two different ethylene contents and an aliphatic polyketone. The effects of pouch thickness were studied using high‐density polyethylene films of different thicknesses between 25 µm and 200 µm. The interactions between the milk product and the pouch material were analysed by oxygen and water permeability, gas chromatography–mass spectrometry and tensile testing. The CO2 and O2 contents in the headspace of the pouches were determined. The food quality was determined by measuring whey syneresis and the contents of Bifidobacteria, Enterobacteriaceae, yeast and mould. A trained taste panel determined the sensory properties. The content of CO2, and consequently the sparkling taste, increased with increasing polarity and/or pouch thickness. The CO2 content was affected more easily by changes in material polarity than by changes in pouch thickness. The increase in whey syneresis and the decrease in Bifidobacteria content with time were independent of material polarity and pouch thickness. The contents of Enterobacteriaceae, yeast and mould in the liquid were always below existing limits for foodstuffs. A newly developed method was used by which the CO2 and O2 permeabilities of the pouch/packaging could be estimated, using the kinetics of the gas composition in the pouch headspace. Permeability values, as estimated by the method, revealed that the CO2 production and the O2 consumption rates of the fermented milk were dependent on the CO2 and O2 headspace concentrations. An increase in permeability, determined by conventional methods, suggested that both the non‐polar and the polar polymers were plasticized by fermented milk. The plasticization was, however, modest and undetectable when the polyethylene tensile test data were analysed. Copyright © 2003 John Wiley & Sons, Ltd.
Effects of ozone exposure on the structural, mechanical and barrier properties of select plastic packaging films
Authors: Ozen Banu F. , Mauer Lisa J. , Floros John D.
Published: April 2003

The effects of ozone (O3) gas exposure at various concentrations and treatment times on structural, mechanical and barrier properties of polyethylene and polyamide films were investigated. Changes in the structure of the films were monitored using an FT‐IR spectrometer. The results showed that O3 treatment affected polyethylene and polyamide films differently. While O3 treatment caused formation of oxygen‐containing functional groups and degradation of polymeric chains in polyethylene films, O3 treatment of polyamide films significantly increased the –C–N– stretch observed at 1125 cm−1 in the FT‐IR spectra. The changes in the mechanical properties of polyethylene films depended on the O3 treatment conditions (temperature and O3 concentration were the most significant), but an increase in tensile strength of polyamide films was observed regardless of the treatment conditions. Permeability to O2 for both types of films decreased with increasing O3 treatment time. Copyright © 2003 John Wiley & Sons, Ltd.
Prototropic tautomers of 5‐methylcytosine and enthalpy changes of their protonation, deprotonation, and deamination: Hybrid density functional B3LYP study
Authors: Tian Shan Xi , Xu Ke Zun
Published: April 2003

Molecular and thermodynamic properties such as geometric parameters, dipole moments, vibrational frequencies, the first ionization potentials, relative tautomerization energies, and tautomeric equilibrium constants of all prototropic tautomers of 5‐methylcytosine have been studied at the hybrid density functional level B3LYP/6‐31+G(d,p). The methylation on the C5 atom does not lead to significant geometric deformation of the pyrimidine structures of the corresponding tautomers of cytosine, which maintains the similar stability order. The tautomeric species 2‐oxo‐4‐amino [T(0)], 2‐hydroxy‐4‐amino [T(1‐2s) and T(1‐2t)], and trans‐2‐oxo‐4‐imino [T(3‐4t)] are predominated in the gas phase. The zwitterionic conformers of tautomerism [T(1‐4)] and protonation [P(4), P(1‐2s‐4), P(1‐2t‐4), and P(1‐3‐4)] are investigated for the first time due to their close relationship with deamination during genetic repair. Enthalpy changes (ΔrH) of protonation, deprotonation, and deamination are calculated for these tautomeric species at room temperature; it is noted that the relative enthalpies [δ(ΔH)] of the tautomers are rationalized well in terms of a second‐order polynomial of the sum of the mean ΔrH values of protonation and deprotonation processes. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Time asymmetry, nonexponential decay, and complex eigenvalues in the theory and computation of resonance states
Authors: Nicolaides Cleanthes A.
Published: April 2003

Stationary‐state quantum mechanics presents no difficulties in defining and computing discrete excited states because they obey the rules established in the properties of Hilbert space. However, when this idealization has to be abandoned to formulate a theory of excited states dissipating into a continuous spectrum, the problem acquires additional interest in many fields of physics. In this article, the theory of resonances in the continuous spectrum is formulated as a problem of decaying states, whose treatment can entail time‐dependent as well as energy‐dependent theories. The author focuses on certain formal and computational issues and discusses their application to polyelectronic atomic states. It is argued that crucial to the theory is the understanding and computation of a multiparticle localized wavepacket, Ψ0, at t = 0, having a real energy E0. Assuming this as the origin, without memory of the excitation process, the author discusses aspects of time‐dependent dynamics, for t ≈ 0 as well as for t → ∞, and the possible significance of nonexponential decay in the understanding of time asymmetry. Also discussed is the origin of the complex eigenvalue Schrödinger equation (CESE) satisfied by resonance states and the state‐specific methodology for its solution. The complex eigenvalue drives the decay exponentially, with a rate Γ, to a good approximation. It is connected to E0 via analytic continuation of the complex self‐energy function, A(z), (z is complex), into the second Riemann sheet, or, via the imposition of outgoing wave boundary conditions on the stationary state Schrödinger equation satisfied by the Fano standing wave superposition in the vicinity of E0. If the nondecay amplitude, G(t), is evaluated by inserting the unit operator I = ∫dE|E><E| G(t) = < Ψ0|e−iHt|Ψ0 >, then the resulting spectral function is real, g(E) =|<Ψ0|E>|2, and does not differentiate between positive and negative times. The introduction of time asymmetry, which is associated with irreversibility, is achieved by starting from < Ψ0|θ(t)e−iHt|Ψ0 >, where θ(t) is the step function at the discontinuity point t = 0. In this case, the spectral function is complex. Within the range of validity of exponential decay, the complex spectral function is the same as the coefficient of Ψ0 in the theory of the CESE. A calculation of G(t) using the simple pole approximation and the constraints that t > 0 and E > 0 results in a nonexponential decay (NED) correction for t ≫ 1/Γ that is different than when a real g(E) is used, representing the contribution of both “in” and “out” states. Earlier formal and computational work has shown that resonance states close to threshold are good candidates for NED to acquire nonnegligible magnitude. In this context, a pump‐probe laser experiment in atomic physics is proposed, using as a paradigm the He− 1s2p2 4P shape resonance. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Solution of periodic Poisson's equation and the Hartree–Fock approach for solids with extended electron states: Application to linear augmented plane wave method
Authors: Nikolaev A. V. , Dyachkov P. N.
Published: April 2003

We formulate a Hartree–Fock‐LAPW method for electronic band structure calculations. The method is based on the Hartree–Fock–Roothaan approach for solids with extended electron states and closed core shells where the basis functions of itinerant electrons are linear augmented plane waves. All interactions within the restricted Hartree–Fock approach are analyzed and in principle can be taken into account. In particular, we obtained the matrix elements for the exchange interactions of extended states and the crystal electric field effects. To calculate the matrix elements of exchange for extended states, we first introduce an auxiliary potential and then integrate it with an effective charge density corresponding to the electron exchange transition under consideration. The problem of finding the auxiliary potential is solved by using the strategy of the full potential LAPW approach, which is based on the general solution of periodic Poisson's equation. Here, we use an original technique for the general solution of periodic Poisson's equation and multipole expansions of electron densities. We apply the technique to obtain periodic potentials of the face‐centered cubic lattice and discuss its accuracy and convergence in comparison with other methods. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Soft systems methodology and dialectics in an information environment: a case study of the Battle of Britain
Authors: Robinson Bruce , Wilson Francis
Published: April 2003

In the Checkland and Holwell (1998) book Information, Systems and Information Systems an explanatory framework for soft systems methodology (SSM) is supported by the deployment of a case study of the Battle of Britain. In this paper the authors conduct an analysis of this historical account and identify the failure of SSM to provide an adequate explanation of these historical events. It is argued that through the use of materialist dialectics a more satisfactory understanding of the nature of the processes of abstraction and the bounding of problems and systems becomes available. Concepts from dialectics are applied to show how, and why, the differences between the two accounts reflect different methods of conceptualization of an information environment. In this light, we point to similarities and differences between the two meta‐frameworks used: SSM and materialist dialectics. Copyright © 2002 John Wiley & Sons, Ltd.
Factors that induce change in information systems
Authors: Malmsjö Anders , Övelius Erika
Published: April 2003

Change cannot effectively be dealt with unless the nature of change is understood. This attitude to handling change is a point of departure for this work. Society changes, and conditions for organizations change. This will have a critical effect on the conditions for information systems. If necessary corrections are not made to the information system due to new conditions based on new demands on the information system, the information system will eventually be a system that no one will ask for. The purpose of this work is to specify the basis for making adequate corrections on information systems due to new conditions. Change factors, which will influence the conditions for an information system, have been identified by analysing studies in the literature where change factors that induce change to organizations are dealt with. A synthesis of change factors on the level of the organization has been transformed to the level of the individual, where the actual interaction between the information system and its context takes place. Furthermore, an empirical study based on approximately 150 interviews considering users' information needs in three Swedish government authorities has been considered in a synthesis. Based on that the following change factors have been found:external factors: type of work performed, working climate, time at disposal, competition, technology, laws and regulations, economy, feedback, environmental demands and expectations, culture, conflicts;internal factors: stress, experience, habits and motivation. Copyright © 2003 John Wiley & Sons, Ltd.
All‐uses testing of shared memory parallel programs
Authors: Yang Cheer‐Sun D. , Pollock Lori L.
Published: April 2003

Parallelism has become a way of life for many scientific programmers. A significant challenge in bringing the power of parallel machines to these programmers is providing them with a suite of software tools similar to the tools that sequential programmers currently utilize. Unfortunately, writing correct parallel programs remains a challenging task.In particular, automatic or semi‐automatic testing tools for parallel programs are lacking. This paper takes a first step in developing an approach to providing all‐uses coverage for parallel programs. A testing framework and theoretical foundations for structural testing are presented, including test data adequacy criteria and hierarchy, formulation and illustration of all‐uses testing problems, classification of all‐uses test cases for parallel programs, and both theoretical and empirical results with regard to what can be achieved with all‐uses coverage for parallel programs. Copyright © 2003 John Wiley & Sons, Ltd.
Individual Blade Pitch Control for Load Reduction
Authors: Bossanyi E. A.
Published: April 2003

If a pitch‐regulated wind turbine has individual pitch actuators for each blade, the possibility arises to send different pitch angle demands to each blade. The possibility of using this as a way of reducing loads has been suggested many times over the years, but the idea has yet to gain full commercial acceptance. There are a number of reasons why this situation may be set to change, and very significant load reductions can result. Copyright © 2002 John Wiley & Sons, Ltd.