bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolation of an antimicrobial compound from Impatiens balsamina L. using bioassay‐guided fractionation
Authors: Yang Xiaolong , Summerhurst D. Kristen , Koval Susan F. , Ficker Christine , Smith Myron L. , Bernards Mark A.
Published: August 2002

By using brine shrimp (Artemia salina) lethality test‐guided fractionation, a single bioactive compound (LC50=26 ppm) was isolated from the 95% ethanol extract of the dried aerial parts of Impatiens balsamina L. and subsequently identified as 2‐methoxy‐1,4‐naphthoquinone (MNQ). The structure of MNQ was confirmed by UV, FT‐IR, MS, and 1‐and 2‐D NMR spectroscopy. The antimicrobial activity of MNQ was evaluated using 12 bacterial and eight fungal strains. Five gram‐positive and two gram‐negative bacteria as well as all eight fungi (including multi‐drug resistant strains) tested were highly sensitive to MNQ. A tea prepared according to traditional methods was found to contain sufficient MNQ to account for its antimicrobial properties. Copyright © 2001 John Wiley & Sons, Ltd.
Confidence interval for the mean of non‐normal data
Authors: Wang F. K.
Published: August 2002

The problem of constructing a confidence interval for the mean of non‐normal data is considered. The Bootstrap method and the Box–Cox transformation method of constructing the confidence interval are compared with the normal theory method. Simulation studies are used to evaluate the performance of these different methods of constructing confidence intervals. The result is not surprising; the Bootstrap method is more effective and efficient than the Box–Cox transformation method and the normal theory method in this simulation study. A real example demonstrates the ability of these methods to construct a confidence interval for the mean of audit accounting data. Copyright © 2001 John Wiley & Sons, Ltd.
Investigation of structural and electronic biases in mutagenic compounds
Authors: Llorens Oriol , Perez Juan J. , Villar Hugo O.
Published: August 2002

The use of high throughput screening as the main means to discover lead compounds continues to require the design of libraries for screening. In this work some insights that may permit building chemical libraries that are biased toward compounds that are less likely to be mutagenic are shown. Toward this goal, the study of the distribution of substructural and electronic properties found in compounds that have been reported to be mutagens and nonmutagens is discussed. Mutagenic data retrieved for each of four Salmonella strains, TA‐98, TA‐100, TA‐1535, and TA‐1537, were compiled and divided depending on whether the compounds underwent metabolic activation. For each of the eight compound databases, an exhaustive enumeration of all molecular substructures within it was carried out. Comparison of the fragment distributions in sets of molecules that were Ames positive to a set of compounds found to be negative and vice versa allowed the deduction of moieties that are statistically overrepresented in active versus inactive or inactive versus active compounds for each strain and metabolic state. Our results show that compounds containing nitro functionalities are overrepresented in the Ames test in all strains whether the compounds had been metabolically activated or not. However, presence of a nitro functionality does not ensure that the compounds being Ames positive. Therefore, we computed a series of steric and electronic properties for 270 nitroaromatic compounds using semiempirical techniques. The electron affinity of the compounds offers a statistically significant discrimination between positive and negative compounds. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem 88: 107–117, 2002
The complementary roles of molecular surface electrostatic potentials and average local ionization energies with respect to electrophilic processes
Authors: Politzer Peter , Murray Jane S. , Concha Monica C.
Published: August 2002

We focus upon two properties, the electrostatic potential V(r) and the average local ionization energy \documentclass{article}\pagestyle{empty}\begin{document}$\bar{I}(\mathbf{r})$\end{document}. When evaluated on molecular surfaces, VS(r) and \documentclass{article}\pagestyle{empty}\begin{document}$\bar{I}_{S}(\mathbf{r})$\end{document} can be useful tools for analyzing and predicting reactive behavior. VS(r) is most reliable with respect to noncovalent interactions; when electrophilic attack and some degree of charge transfer are involved, then the combination of VS(r) and \documentclass{article}\pagestyle{empty}\begin{document}$\bar{I}_{S}(\mathbf{r})$\end{document} can be quite effective. They play complementary roles: VS(r) reveals the regions of the molecule to which an electrophile would initially be attracted, and \documentclass{article}\pagestyle{empty}\begin{document}$\bar{I}_{S}(\mathbf{r})$\end{document} indicates the ease of charge transfer at these and other sites. Four examples of such complementarity are discussed, involving benzene derivatives, guanine and cytosine, furan and pyrrole, and binary hydrides. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002
Chromatofocusing nonporous reversed‐phase high‐performance liquid chromatography/electrospray ionization time‐of‐flight mass spectrometry of proteins from human breast cancer whole cell lysates: a novel two‐dimensional liquid chromatography/mass spectrometry method
Authors: Chong Bathsheba E. , Yan Fang , Lubman David M. , Miller Fred R.
Published: August 2002

A novel two‐dimensional two‐column liquid chromatography/mass spectrometry (LC/MS) technique is described in this work, where chromatofocusing (CF) has been coupled to nonporous reversed‐phase (NPS‐RP) HPLC to separate proteins from human breast epithelial whole cell lysates. The liquid fractions from NPS‐RP‐HPLC are readily amenable to direct on‐line analysis using electrospray ionization orthogonal acceleration time‐of‐flight mass spectrometry (ESI‐TOFMS). A key advantage of this technique is that proteins can be ‘peeled off’ in the liquid phase from the CF column according to their isoelectric points (pI) in the first chromatographic separation dimension. The NPS‐RP‐HPLC column further separates thesepI‐focused fractions based upon protein hydrophobicity as the second chromatographic dimension. The third dimension involves on‐line molecular weight determination using ESI‐TOFMS. As a result, this method has the potential to be fully automated. In addition, a 2‐D protein map ofpIversus molecular weight is generated, which is analogous to a 2‐D gel image. Thus, this technique may provide a means to study differential expression of proteins from whole cell lysates. Copyright © 2001 John Wiley & Sons, Ltd.
Referencing strategies and techniques in stable isotope ratio analysis
Authors: Werner Roland A. , Brand Willi A.
Published: August 2002

Stable isotope ratios are reported in the literature in terms of a deviation from an international standard (δ‐values). The referencing procedures, however, differ from instrument to instrument and are not consistent between measurement facilities. This paper reviews an attempt to unify the strategy for referencing isotopic measurements. In particular, emphasis is given to the importance of identical treatment of sample and reference material (‘IT principle’), which should guide all isotope ratio determinations and evaluations. The implementation of the principle in our laboratory, the monitoring of our measurement quality, the status of the international scales and reference materials and necessary correction procedures are discussed. Copyright © 2001 John Wiley & Sons, Ltd.
Determination of phenolic compounds in rose hip (Rosa canina) using liquid chromatography coupled to electrospray ionisation tandem mass spectrometry and diode‐array detection
Authors: Hvattum Erlend
Published: August 2002

Liquid chromatography coupled with negative and positive electrospray ionisation (ESI) tandem mass spectrometry (MS/MS) and diode‐array detection (DAD) was used for determination of phenols in rose hip (Rosa canina) extract. ESI mass spectra of the chromatographically separated phenols gave the molecular weight of the compounds through prominent [M − H]− ions for most of the compounds and M+ ions for the anthocyanins. Collision induced dissociation (CID) of the [M − H]− (or M+) precursor ions yielded product ions which determined the molecular weight of the aglycones. In‐source fragmentation followed by CID of the resulting deprotonated aglycone ([A − H]−) provided product ions for the identification of the unconjugated phenols. The identification was based on comparison with product ion spectra of commercial standards. UV‐diode‐array spectra were used for identity confirmation. This combined approach allowed the identification in rose hip extract of an anthocyanin, i.e. cyanidin‐3‐O‐glucoside, several glycosides of quercetin and glycosides of taxifolin and eriodictyol. Phloridzin was identified, and several conjugates of methyl gallate were also found, one of which was tentatively identified as methyl gallate‐rutinoside. Catechin and quercetin were found as the aglycones in the extract. Copyright © 2002 John Wiley & Sons, Ltd.
Forensic identification of explosive oxidizers by electrospray ionization mass spectrometry
Authors: Zhao Xiaoming , Yinon Jehuda
Published: August 2002

The mass spectrometry of a group of inorganic oxidizers was studied using the electrospray ionization technique. It was found that a series of cluster ions were predominant in both positive‐ and negative‐ion mode, allowing for the characterization of the investigated oxidizers. The identity of the recorded cluster ions was further confirmed by using some isotopically labeled compounds and tandem mass spectrometry with collision‐induced dissociation. The use of electrospray ionization mass spectrometry for positive identification of major oxidizer components in explosive formulations was demonstrated by three samples of forensic interest. Copyright © 2002 John Wiley & Sons, Ltd.
Borna disease virus
Authors: Jordan Ingo , Lipkin W. Ian
Published: August 2002

Borna disease virus (BDV) is unique amongst animal RNA viruses in its molecular biology and capacity to cause persistent, noncytolytic CNS‐infection in a wide variety of host species. Unlike other non‐segmented negative‐strand RNA animal viruses, BDV replicates in the nucleus of the host cell where splicing is employed for expression of a very compact genome. Epidemiological studies indicate a broad host range and geographical distribution, and some investigators have proposed that human infection may result in neuropsychiatric disorders. Experimental Borna disease in neonatal and adult rats provides an intriguing model for immune‐mediated disturbances of brain development and function. Copyright © 2001 John Wiley & Sons, Ltd.
Antiviral agents active against human herpesviruses HHV‐6, HHV‐7 and HHV‐8
Authors: De Clercq Erik , Naesens Lieve , De Bolle Leen , Schols Dominique , Zhang Ying , Neyts Johan
Published: August 2002

A series of antiviral compounds were examined for their activity against human herpesvirus type 6 (HHV‐6), type 7 (HHV‐7) and type 8 (HHV‐8). They were selected either because they are already approved for clinical use in the treatment of herpesvirus infections (acyclovir, valaciclovir, penciclovir, famciclovir, ganciclovir, brivudin, foscarnet and cidofovir) or have demonstrated marked activity against herpesviruses (lobucavir, H2G, A‒5021, D/L‐cyclohexenyl G and S2242). In view of their host cell specificity, different cells and assays had to be used for determining antiviral activity against these three viruses. The most potent compounds with the highest antiviral selectivity index were: (i) for HHV‐6; foscarnet, S2242, A‐5021 and cidofovir; (ii) for HHV‐7; S2242, cidofovir and foscarnet; and (iii) for HHV‐8; S2242, cidofovir and ganciclovir. As mycophenolic acid has been shown to enhance significantly the activity of acyclic guanosine analogues (such as acyclovir, penciclovir and ganciclovir) in vitro against HSV‐1, HSV‐2, VZV and HCMV, it would seem worth evaluating whether mycophenolic acid also potentiates the activity of these acyclic guanosine analogues against HHV‐6, ‐7 and ‐8. Copyright © 2001 John Wiley & Sons, Ltd.
HHV‐8 infection: a model for reactivation and transmission
Authors: Corey Lawrence , Brodie Scott , Huang Meei‐Li , Koelle David M. , Wald Anna
Published: August 2002

The rapid pace of knowledge about HHV‐8 since its discovery has been one of the most exciting aspects of medical virology in the last decade. As outlined in this review, the discovery by Drs Chang and Moore of this virus has opened up a broad field of biology with interesting contrasts between current epidemiological data for Kaposi's sarcoma and the cell biology of this gamma herpesvirus. In particular, we summarise the paucity of virological data supporting genital sites of replication and emphasise detection of HHV‐8 in the oropharynx. Hopefully continued study will address many of the critical questions that exist today regarding how this infection is transmitted and acquired. Copyright © 2001 John Wiley & Sons, Ltd.
Functional balance between haemagglutinin and neuraminidase in influenza virus infections
Authors: Wagner Ralf , Matrosovich Mikhail , Klenk Hans‐Dieter
Published: August 2002

Influenza A and B viruses carry two surface glycoproteins, the haemagglutinin (HA) and the neuraminidase (NA). Both proteins have been found to recognise the same host cell molecule, sialic acid. HA binds to sialic acid‐containing receptors on target cells to initiate virus infection, whereas NA cleaves sialic acids from cellular receptors and extracellular inhibitors to facilitate progeny virus release and to promote the spread of the infection to neighbouring cells. Numerous studies performed recently have revealed that an optimal interplay between these receptor‐binding and receptor‐destroying activities of the surface glycoproteins is required for efficient virus replication. An existing balance between the antagonistic HA and NA functions of individual viruses can be disturbed by various events, such as reassortment, virus transmission to a new host, or therapeutic inhibition of neuraminidase. The resulting decrease in the viral replicative fitness is usually overcome by restoration of the functional balance due to compensatory mutations in HA, NA or both proteins. Copyright © 2002 John Wiley & Sons, Ltd.
Practical stabilization of exponentially unstable linear systems subject to actuator saturation nonlinearity and disturbance
Authors: Hu Tingshu , Lin Zongli
Published: August 2002

This paper investigates the problem of practical stabilization for linear systems subject to actuator saturation and input additive disturbance. Attention is restricted to systems with two anti‐stable modes. For such a system, a family of linear feedback laws is constructed that achieves semi‐global practical stabilization on the asymptotically null controllable region. This is in the sense that, for any setχ0in the interior of the asymptotically null controllable region, any (arbitrarily small) setχ∞containing the origin in its interior, and any (arbitrarily large) bound on the disturbance, there is a feedback law from the family such that any trajectory of the closed‐loop system enters and remains in the setχ∞in a finite time as long as it starts from the setχ0. In proving the main results, the continuity and monotonicity of the domain of attraction for a class of second‐order systems are revealed. Copyright © 2001 John Wiley & Sons, Ltd.
Multiple model adaptive control. Part 2: switching
Authors: Hespanha João , Liberzon Daniel , Stephen Morse A. , Anderson Brian D. O. , Brinsmead Thomas S. , De Bruyne Franky
Published: August 2002

This paper addresses the problem of controlling a continuous‐time linear system with large modelling errors. We employ an adaptive control algorithm consisting of a family of linear candidate controllers supervised by a high‐level switching logic. Methods for constructing such controller families have been discussed in the recent paper by the authors. The present paper concentrates on the switching task in a multiple model context. We describe and compare two different switching logics, and in each case study the behaviour of the resulting closed‐loop hybrid system. Copyright © 2001 John Wiley & Sons, Ltd.
An algorithm for the structural analysis of state space: synthesis of nonlinear observers
Authors: López‐Moralès Virgilio , Plestan Franck , Glumineau Alain
Published: August 2002

The problem addressed is the linearization of multi‐input multi‐output (MIMO) nonlinear systems by a generalized state coordinates transformation and generalized input–output injection, in order to design an observer. This observer will have linear error dynamics. The goal is to bring together two observers design approaches: a structural one and a numerical one. Necessary and sufficient conditions for the existence of a linearizing generalized state transformation are obtained by an algebraic way and without computing the input–output differential equations. The main result tests integrability conditions of differential one‐forms derived from the state space representation and is applicable to a large subclass of nonlinear systems. Copyright © 2001 John Wiley & Sons, Ltd.
Some conditions which make the constantly scaledH∞control synthesis problems convex
Authors: Asai Toru , Hara Shinji
Published: August 2002

In this paper, we present some computationally tractable conditions which make the constantly scaledH∞control synthesis problem convex. If one of the conditions proposed in this paper holds, the constantly scaledH∞control synthesis problem can be solved efficiently as an LMI problem. The results presented here include the existing results such as the state feedback and the full information problems as special cases. In addition, the results are generalized to the case that some of state variables are exactly available. Owing to this generalization, a larger class of problems can be reduced to convex problems, while reduced order controllers can be obtained. Copyright © 2001 John Wiley & Sons, Ltd.
A subspace approach to balanced truncation for model reduction of nonlinear control systems
Authors: Lall Sanjay , Marsden Jerrold E. , Glavaški Sonja
Published: August 2002

In this paper, we introduce a new method of model reduction for nonlinear control systems. Our approach is to construct an approximately balanced realization. The method requires only standard matrix computations, and we show that when it is applied to linear systems it results in the usual balanced truncation. For nonlinear systems, the method makes use of data from either simulation or experiment to identify the dynamics relevant to the input–output map of the system. An important feature of this approach is that the resulting reduced‐order model is nonlinear, and has inputs and outputs suitable for control. We perform an example reduction for a nonlinear mechanical system. Copyright © 2002 John Wiley & Sons, Ltd.
Robust reinforcement learning control with static and dynamic stability
Authors: Kretchmar R. Matthew , Young Peter M. , Anderson Charles W. , Hittle Douglas C. , Anderson Michael L. , Delnero Christopher C.
Published: August 2002

Robust control theory is used to design stable controllers in the presence of uncertainties. This provides powerful closed‐loop robustness guarantees, but can result in controllers that are conservative with regard to performance. Here we present an approach to learning a better controller through observing actual controlled behaviour. A neural network is placed in parallel with the robust controller and is trained through reinforcement learning to optimize performance over time. By analysing nonlinear and time‐varying aspects of a neural network via uncertainty models, a robust reinforcement learning procedure results that is guaranteed to remain stable even as the neural network is being trained. The behaviour of this procedure is demonstrated and analysed on two control tasks. Results show that at intermediate stages the system without robust constraints goes through a period of unstable behaviour that is avoided when the robust constraints are included. Copyright © 2001 John Wiley & Sons, Ltd.
A position/force control for a robot finger with soft tip and uncertain kinematics
Authors: Doulgeri Zoe , Arimoto Suguru
Published: August 2002

We consider the position and force regulation problem for a soft tip robot finger in contact with a rigid surface under kinematic and dynamic parametric uncertainties. The reproducing force is assumed to be related to the displacement through a nonlinear function whose characteristics are unknown, but both the actual displacement and force can be directly measured. Kinematic uncertainties concern the rigid surface orientation and the contact point location. Kinematic parameters involved in the contact point location concern the length from the last joint to the contact point and the rest of the link lengths in the general case. An adaptive controller with a composite update parameter law is proposed, and the asymptotic stability of the force and estimated position errors under dynamic and kinematic uncertainties is shown for the planar case. Simulation results for a three‐degrees‐of‐freedom planar robotic finger are presented. © 2002 Wiley Periodicals, Inc.
Controller design for natural and robotic systems with transmission delays
Authors: Kataria Abhay , Özbay Hitay , Hemami Hooshang
Published: August 2002

Robust stability and two‐dimensional trajectory following problems are considered forn‐link robotic systems with transmission delays. Such problems appear in telerobotics, where the controller is physically far from the robot, and in neural control of musculo‐skeletal (biological) systems, where muscle actuation and neural sensing are subject to time delays. A typical second‐order nonlinear dynamical model is taken with input and output time delays. In a prior work by the authors, a control strategy was developed for stable movement of the planar linkage system, using the standardQ‐parameterization and solving anH∞control problem to determine the free parameter. In this article, a new control scheme is proposed to eliminate the steady‐state errors seen in the tracking performance of the controller derived in the earlier work. Simulation examples are shown to demonstrate the effectiveness of the proposed control methodology. © 2002 Wiley Periodicals, Inc.
Neural network‐based state prediction for strategy planning of an air hockey robot
Authors: Park Jung Il , Partridge Chad B. , Spong Mark W.
Published: August 2002

We analyze a neural network implementation for puck state prediction in robotic air hockey. Unlike previous prediction schemes which used simple dynamic models and continuously updated an intercept state estimate, the neural network predictor uses a complex function, computed with data acquired from various puck trajectories, and makes a single, timely estimate of the final intercept state. Theoretically, the network can account for the complete dynamics of the table if all important state parameters are included as inputs, an accurate data training set of trajectories is used, and the network has an adequate number of internal nodes. To develop our neural networks, we acquired data from 1500 no‐bounce and 1500 one‐bounce puck trajectories, noting only translational state information. Analysis showed that performance of neural networks designed to predict the results of no‐bounce trajectories was better than the performance of neural networks designed for one‐bounce trajectories. Since our neural network input parameters did not include rotational puck estimates and recent work shows the importance of spin in impact analysis, we infer that adding a spin input to the neural network will increase the effectiveness of state estimates for the one‐bounce case. © 2001 John Wiley & Sons, Inc.
Position and force tracking of a two‐manipulator system manipulating a flexible beam
Authors: Sun Dong , Liu Yun‐Hui
Published: August 2002

This article discusses the issue of hybrid position and force control of a two‐manipulator system manipulating a flexible beam in trajectory tracking. Unlike our previous approach of set‐point position control in the trajectory tracking, the system coordinates are hard to be regulated to the desired states with nonzero tracking velocities under continuous feedback control. In this study, we design a hybrid position and force tracking controller while using saturation control to compensate for the effect of beam vibration dynamics on the tracking performance. All parameters and states used in the controller are readily available so that the proposed method is feasible to implement. Under the proposed controller, the tracking error asymptotically converges to a predetermined boundary. Simulation results demonstrate the validity of the proposed approach. © 2001 John Wiley & Sons, Inc.
Robust force control of a flexible arm with a nonsymmetric rigid tip body
Authors: Morita Yoshifumi , Kobayashi Yukihiro , Kando Hisashi , Matsuno Fumitoshi , Kanzawa Takao , Ukai Hiroyuki
Published: August 2002

In this article, we discuss modeling and robust control of bending and torsional vibrations and contact force of a flexible arm with a nonsymmetric rigid tip body. By using Hamilton's principle and the Lagrange multiplier method, dynamic equations of the constrained flexible arm are derived. Since the flexible arm has the nonsymmetric tip body, the bending and torsional vibrations are coupled. As the obtained boundary conditions of the distributed parameter system are nonhomogeneous, we introduce a change of variables to derive homogeneous boundary conditions. By using the eigenvalues and the correpsonding eigenfunctions related to the distributed parameter system, we derive a finite‐dimensional modal model. To compensate for the spillover instability, we construct robust controllers of an optimal controller with a low‐pass property and anH∞controller. Some experiments have been carried out to show the effectiveness of the proposed robust controllers. © 2001 John Wiley & Sons, Inc.
A real‐coded genetic optimal kinematic design of a Stewart fine tuning platform for a large radio telescope
Authors: Su Y. X. , Duan B. Y. , Peng B. , Nan R. D.
Published: August 2002

A real‐coded genetic design methodology for an optimal kinematic Stewart platform is presented in this article. The Jacobian matrix connecting the dexterity performance of the parallel platform is first deduced, and then the condition number of Jacobian matrix is employed as the objective function to implement the optimal kinematic design of Stewart fine tuning platform for a large spherical radio telescope. A niched‐penalty approach is used to transform this optimal kinematic design problem to an unconstrained one, and a niching technique and the dynamic mutation operator are applied. A kinematic accuracy comparison of the genetically designed Stewart fine tuning platform with the quasi‐Newtonian designed platform is made. The comparison results have shown that the kinematic accuracy of the genetically designed Stewart fine tuning platform has a much higher accuracy and compact structure than that of the quasi‐Newtonian designed platform, which guarantees the implementation of high accuracy requirement of trajectory tracking and reduces the disturbance of random wind for large radio telescopes. © 2001 John Wiley & Sons, Inc.
Design and analysis of some nonanthropomorphic, biologically inspired robots: An overview
Authors: Chirikjian Gregory S.
Published: August 2002

In this paper, two kinds of biologically inspired robots under investigation at Johns Hopkins University are reviewed. While these designs are reminiscent of designs in nature, they are, however, not anthropomorphic. Rather, they are zoomorphic in macroscopic structure. These two kinds of robots are snakelike “hyper‐redundant” manipulators, and amoeboid “metamorphic” robots. In addition to issues in the design of the robots, issues in the dynamics and motion planning of these devices are reviewed. © 2001 John Wiley & Sons, Inc.
Optimal robot motions for physical criteria
Authors: Bobrow J. E. , Martin B. , Sohl G. , Wang E. C. , Park F. C. , Kim Junggon
Published: August 2002

This paper presents an optimization‐based framework for emulating the low‐level capabilities of human motor coordination and learning. Our approach rests on the observation that in most biological motor learning scenarios some form of optimization with respect to a physical criterion is taking place. By appealing to techniques from the theory of Lie groups, we are able to formulate the equations of motion of complex multibody systems in such a way that the resulting optimization problems can be solved reliably and efficiently—the key lies in the ability to compute exact analytic gradients of the objective function without resorting to numerical approximations. The methodology is illustrated via a wide range of optimized, “natural” motions for robots performing various human‐like tasks—for example, power lifting, diving, and gymnastics. © 2001 John Wiley & Sons, Inc.
New and faster filters for multiple approximate string matching
Authors: Baeza‐Yates Ricardo , Navarro Gonzalo
Published: August 2002

We present three new algorithms for on‐line multiple string matching allowing errors. These are extensions of previous algorithms that search for a single pattern. The average running time achieved is in all cases linear in the text size for moderate error level, pattern length, and number of patterns. They adapt (with higher costs) to the other cases. However, the algorithms differ in speed and thresholds of usefulness. We theoretically analyze when each algorithm should be used, and show their performance experimentally. The only previous solution for this problem allows only one error. Our algorithms are the first to allow more errors, and are faster than previous work for a moderate number of patterns (e.g. less than 50–100 on English text, depending on the pattern length). © 2002 John Wiley & Sons, Inc. Random Struct. Alg., 20, 23–49, 2002
High elevation angle satellite‐to‐earth 12 GHz propagation measurements in the tropics
Authors: Pan Qingwei , Bryant Geoff H. , McMahon John , Allnutt Jeremy E. , Haidara Fatim
Published: August 2002

A simple, low‐cost propagation terminal for measuring path attenuation and site diversity, using satellite transmissions at 12 GHz, is described. The novelty of this system is the use of a standard domestic satellite low‐noise block (LNB) front‐end connected directly to a spectrum analyser in place of an expensive beacon receiver. A description of the equipment, an analysis of relevant system parameters, and a discussion of the environmental conditions are presented. The method used to obtain a clear‐sky baseline reference and a description of the channel signal processing are given. Analysis of the rainfall rate and attenuation exceedances statistics has led to the proposal of a new model to derive the effective rain‐cell diameters and effective rain‐column heights in tropical areas for attenuation predictions in satellite communication link budget calculations. Site‐diversity statistics are also examined. Though the main site is only 6.5 km inland from the second coastal site, there are marked differences in their rain‐cell characteristics. The significance of volume saturation of rain cells on modelling, the operating margins of the measuring system, and the relevance of the site‐diversity data to enhancing the understanding of the proposed volume saturation model are discussed. Copyright © 2001 John Wiley & Sons, Ltd.
Analysis of handover characteristics in shadowed LEO satellite communication networks
Authors: Kwon Young Hoon , Sung Dan Keun
Published: August 2002

In the near future, low earth orbit (LEO) satellite communication networks will partially substitute the fixed terrestrial multimedia networks especially in sparsely populated areas. Unlike fixed terrestrial networks, ongoing calls may be dropped if satellite channels are shadowed. Therefore, in most LEO satellite communication networks more than one satellite needs to be simultaneously visible in order to hand over a call to an unshadowed satellite when the communicating satellite is shadowed. In this paper, handover characteristics for fixed terminals (FTs) in LEO satellite communication networks are analysed. The probability distribution of multiple satellite visibility is analytically obtained and the shadowing process of satelites for FTs are modelled. Using the proposed analysis model, shadowing effects on the traffic performance are evaluated in terms of the number of intersatellite and interbeam handovers during a call. Copyright © 2001 John Wiley & Sons, Ltd.
Tangled up in views: Beliefs in the nature of science and responses to socioscientific dilemmas
Authors: Zeidler Dana L. , Walker Kimberly A. , Ackett Wayne A. , Simmons Michael L.
Published: August 2002

The purpose of this study was to investigate the relationships between students' conceptions of the nature of science and their reactions to evidence that challenged their beliefs about socioscientific issues. This study involved 41 pairs of students representing “critical cases” of contrasting ethical viewpoints. These 82 students were identified from a larger sample of 248 students from 9th and 10th grade general science classes, 11th and 12th grade honors biology, honors science, and physics classes, and upper‐level college preservice science education classes. Students responded to questions aimed at revealing their epistemological views of the nature of science and their belief convictions on a selected socioscientific issue. The smaller subset of students was selected based on varying degrees of belief convictions about the socioscientific issues and the selected students were then paired to discuss their reasoning related to the issue while being exposed to anomalous data and information from each other and in response to epistemological probes of an interviewer. Taxonomic categories of students' conceptions of the nature of science were derived from the researchers' analysis of student responses to interviews and questionnaires. In some instances, students' conceptions of the nature of science were reflected in their reasoning on a moral and ethical issue. This study stimulated students to reflect on their own beliefs and defend their opinions. The findings suggest that the reactions of students to anomalous socioscientific data are varied and complex, with notable differences in the reasoning processes of high school students compared to college students. A deeper understanding of how students reason about the moral and ethical context of controversial socioscientific issues will allow science educators to incorporate teaching strategies aimed at developing students' reasoning skills in these crucial areas. © 2002 Wiley Periodicals, Inc. Sci Ed 86:343–367, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/sce.10025
Similarity and difference: Student cooperation in Taiwanese and Australian science classrooms
Authors: Wallace John , Chou Ching‐Yang
Published: August 2002

In this study, we examine the way in which students cooperate in Taiwanese and Australian science classrooms. We adopt the position that student cooperation is best understood by examining the patterns of variation within and between countries rather than trying to describe similarities and differences in essential terms. A critical analysis of large‐scale learning environment questionnaire data combined with in‐depth interview and observational data leads to several findings about the nature of student cooperation in the two countries. We conclude that students from Taiwan and Australia have a range of understandings and interpretations about what it means to cooperate in science classrooms. There are complex connections between cooperative behavior, student academic ability, sex, and nationality, which are best understood in socio‐cultural terms. © 2001 John Wiley & Sons, Inc. Sci Ed 85:694–711, 2001.
Shared scientific thinking in everyday parent‐child activity
Authors: Crowley Kevin , Callanan Maureen A. , Jipson Jennifer L. , Galco Jodi , Topping Karen , Shrager Jeff
Published: August 2002

Current accounts of the development of scientific reasoning focus on individual children's ability to coordinate the collection and evaluation of evidence with the creation of theories to explain the evidence. This observational study of parent–child interactions in a children's museum demonstrated that parents shape and support children's scientific thinking in everyday, nonobligatory activity. When children engaged an exhibit with parents, their exploration of evidence was observed to be longer, broader, and more focused on relevant comparisons than children who engaged the exhibit without their parents. Parents were observed to talk to children about how to select and encode appropriate evidence and how to make direct comparisons between the most informative kinds of evidence. Parents also sometimes assumed the role of explainer by casting children's experience in causal terms, connecting the experience to prior knowledge, or introducing abstract principles. We discuss these findings with respect to two dimensions of children's scientific thinking: developments in evidence collection and developments in theory construction. © 2001 John Wiley & Sons, Inc.Sci Ed85:712–732, 2001.
Tracking the processes of change in US undergraduate education in science, mathematics, engineering, and technology
Authors: Seymour Elaine
Published: August 2002

This paper describes some features in the changing landscape of activities intended to improve both quality and access in science, mathematics, engineering, and technology (SMET) undergraduate education. Observations are offered from the viewpoint afforded by my work—broadly over the last 10 years—both as a researcher, and as an evaluator for projects related to the improvement of undergraduate SMET education. Over that period, I have watched the landscape change—some issues, at first prominent, have diminished in importance; some are emergent; and yet others lie on the horizon. I have also observed that actions in pursuit of various reform goals reflect a variety of theories about how change can be accomplished that are not necessarily complementary. This short history of shifts in the focus of our efforts, and in our beliefs about how they may be achieved, is offered as a framework for discussion of these nationwide endeavors and as an aid in considering next steps. © 2001 John Wiley & Sons, Inc. Sci Ed 86:79–105, 2001.
Design of a high‐speed RSA encryption processor based on the residue table for redundant binary numbers
Authors: Tomabechi Nobuhiro , Ito Teruki
Published: August 2002

The RSA cryptosystem plays an important role in ensuring the security of network communications, although it has the drawback that much time is required for encryption/decryption. This paper presents a high‐speed RSA encryption processor employing highly parallel operation based as much as possible in the hardware technology as follows: (1) All of the arithmetic circuits required for encryption/decryption are implemented in the form of redundant binary numbers. (2) Residue calculation is performed by table look‐up in a hardware table built in the processor. The table look‐up is done in the form of redundant binary numbers. The operation speed of the proposed processor is found to be 60 times that of usual processors when the key lengthNis 1024 bits. Also, the order of the encryption time of the processor isO(NlogN). The chip size of the processor is estimated as (4.3 × 105λ) × (5.63 × 105λ), where λ denotes the standard size in the layout design. The chip size becomes 10.9 cm × 14.1 cm when the 0.5−µm rule, which corresponds to λ = 0.25 µm, is used, hence the processor can be integrated on an 8‐inch wafer. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(5): 1–10, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1122
Differences of speech rate, interphoneme distance and likelihood caused by speaking style, their relationship, and recognition performance
Authors: Yamamoto Kazumasa , Nakagawa Seiichi
Published: August 2002

We have been developing a speech recognition system as part of a spoken dialogue system. There is a clear limit of recognition performance for dialogue speech using acoustic models built with a read speech database, mainly because various acoustic and linguistic phenomena, which reflect the characteristics of spontaneous speech, occur in dialogue speech. We made acoustic models of syllable unit using simulated dialogue speech or read speech database. We then analyzed the acoustic properties of the dialogue speech in terms of the distance between models and the distribution of duration and compared them with read speech. We found that the speech rate of dialogue speech was faster on average and had a greater variance of speech rate than read speech. We also found that the distance between vowels of the dialogue speech tended to be smaller than that of read speech, that is, the vowels tend to be confused in dialogue speech because of closer boundaries to one another. We also compared recognition performance using acoustic models trained with each database and found that dialogue speech had a low correct syllable rate. Dialogue speech was more prone to insertion and deletion errors and the influence of distance between vowels and the variance of speech rate was shown clearly in the results. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(7): 50–60, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1141
Understanding and managing innovation processes
Authors: Milling Peter M.
Published: August 2002

The lecture was delivered at the Prize ceremony during the 19th International Conference of the System Dynamics Society in Atlanta, Georgia. It summarizes the Award winning article, published in the 1996 issue of System Dynamics Review, and discusses subsequent work. Comprehensive citations and quotations are found in the original publications. Shortened product life cycles, tight competition, and resource intensive research and development are some of the parameters that make innovation management a highly challenging endeavor. To succeed in such an environment, a solid understanding of the observed and the expected behavior is indispensable and can effectively be supported by modeling the object under investigation. The article analyzes strategies for new products, especially price strategies, and includes the processes of research and development in a comprehensive model, which then is disaggregated to explicitly take into consideration the actions of different competitors. Finally, a multi‐person gaming version is presented. The article concludes with some thoughts about complexity, its dimensions and its challenges for system dynamics. Copyright © 2002 John Wiley & Sons, Ltd.
Standardization using the harmonically weighted ratios: internal and external comparisons
Authors: Lee Wen‐Chung
Published: August 2002

Standardization of rates is a basic tool for epidemiologists. The most frequently used methods are the ‘direct standardization’ (with summary index of comparative mortality figure, CMF) and the ‘indirect standardization’ (with summary index of standardized mortality ratio, SMR). The CMF facilitates a valid comparison between populations or across time periods, yet, it suffers from the problem of instability. By contrast, the SMR is stable and can be used for external comparison. However, it cannot guarantee a valid internal comparison. In this paper, the author proposes a new standardized measure, the ‘harmonically weighted ratio’ (HWR). The HWR can be used for external as well as internal comparisons – with the assumption of rate‐ratio homogeneity, or with heterogeneity but dominance of one population over another. Simulation shows that its performance in terms of pairwise comparisons is the best among the three methods or compares favourably to that of the SMR. The author also examines the behaviours of the HWR when used for hypothesis testing (the ‘HWR test’). The HWR can be considered for standardization when the purpose of the standardization is solely for comparison and when the universe of the comparisons can be clearly defined. Copyright © 2002 John Wiley & Sons, Ltd.
A Bayesian analysis of bivariate ordinal data: Wisconsin epidemiologic study of diabetic retinopathy revisited
Authors: Biswas Atanu , Das Kalyan
Published: August 2002

In many biomedical experiments one may often encounter bivariate data which are componentwise ordinal. The data set of the ophthalmologic experiment of the Wisconsin Epidemiologic Study of Diabetic Retinopathy (WESDR) is an example of such data. Several authors considered the analysis of such data from different viewpoints. The present work reviews the existing literature based on the WESDR data and on the basis of some latent variables provide the technique for analysing such data more easily in a Bayesian framework. Computation supports the methodology to a great extent. A comparison between our approach and the likelihood based approach considered by Kim has also been made. Copyright © 2002 John Wiley & Sons, Ltd.
Tests for equivalence or non‐inferiority for paired binary data
Authors: Liu Jen‐pei , Hsueh Huey‐miin , Hsieh Eric , Chen James J.
Published: August 2002

Assessment of therapeutic equivalence or non‐inferiority between two medical diagnostic procedures often involves comparisons of the response rates between paired binary endpoints. The commonly used and accepted approach to assessing equivalence is by comparing the asymptotic confidence interval on the difference of two response rates with some clinical meaningful equivalence limits. This paper investigates two asymptotic test statistics, a Wald‐type (sample‐based) test statistic and a restricted maximum likelihood estimation (RMLE‐based) test statistic, to assess equivalence or non‐inferiority based on paired binary endpoints. The sample size and power functions of the two tests are derived. The actual type I error and power of the two tests are computed by enumerating the exact probabilities in the rejection region. The results show that the RMLE‐based test controls type I error better than the sample‐based test. To establish an equivalence between two treatments with a symmetric equivalence limit of 0.15, a minimal sample size of 120 is needed. The RMLE‐based test without the continuity correction performs well at the boundary point 0. A numerical example illustrates the proposed procedures. Copyright © 2002 John Wiley & Sons, Ltd.
Discovering subpopulation structure with latent class mixed models
Authors: McCulloch C. E. , Lin H. , Slate E. H. , Turnbull B. W.
Published: August 2002

The linear mixed model is a well‐known method for incorporating heterogeneity (for example, subject‐to‐subject variation) into a statistical analysis for continuous responses. However heterogeneity cannot always be fully captured by the usual assumptions of normally distributed random effects. Latent class mixed models offer a way of incorporating additional heterogeneity which can be used to uncover distinct subpopulations, to incorporate correlated non‐normally distributed outcomes and to classify individuals. The methodology is motivated with examples in health care studies and a detailed illustration is drawn from the Nutritional Prevention of Cancer trials. Latent class models are used with longitudinal data on prostate specific antigen (PSA) as well as incidence of prostate cancer. The models are extended to accommodate prostate cancer as a survival endpoint; this is compared to treating it as a binary endpoint. Four subpopulations are identified which differ both with regard to their PSA trajectories and their incidence rates of prostate cancer. Copyright © 2002 John Wiley & Sons, Ltd.