bluuebunny/crossref_metadata_2025 huggingface dataset:
Human cytomegalovirus terminase as a target for antiviral chemotherapy
Authors: Bogner Elke
Published: August 2002

Herpesviral DNA packaging is a complex process involving binding and cleavage of DNA containing the specific DNA‐packaging motifs, pac1 and pac2, and packaging of the resulting unit‒length genomes into preformed procapsids. This process is believed to be mediated by two packaging proteins, the terminase subunits. In the case of human cytomegalovirus the terminase consists of the proteins pUL56 and pUL89. While pUL56 (i) mediates the specific binding to pac sequences on the concatamers, (ii) provides energy for the translocation of the DNA to the procapsids and (iii) associates itself with the capsid for enabling the entry of the DNA into the procapsid, pUL89 is mainly required to effect DNA cleavage. Based on the limited efficacy of the current drugs ganciclovir, cidofovir and foscarnet, new antiviral therapeutics appear to be in demand. Inhibitors targeting pUL56 and/or pUL89 may offer an attractive alternative since mammalian cell DNA replication does not involve cleavage of concatameric DNA. Drugs targeted to terminase‐like proteins should therefore be safe and highly selective. Copyright © 2002 John Wiley & Sons, Ltd.
Observer‐based adaptive robust control of a class of nonlinear systems with dynamic uncertainties
Authors: Yao Bin , Xu Li
Published: August 2002

In this paper, a discontinuous projection‐based adaptive robust control (ARC) scheme is constructed for a class of nonlinear systems in an extended semi‐strict feedback form by incorporating a nonlinear observer and a dynamic normalization signal. The form allows for parametric uncertainties, uncertain nonlinearities, and dynamic uncertainties. The unmeasured states associated with the dynamic uncertainties are assumed to enter the system equations in an affine fashion. A novel nonlinear observer is first constructed to estimate the unmeasured states for a less conservative design. Estimation errors of dynamic uncertainties, as well as other model uncertainties, are dealt with effectively via certain robust feedback control terms for a guaranteed robust performance. In contrast with existing conservative robust adaptive control schemes, the proposed ARC method makes full use of the available structural information on the unmeasured state dynamics and the prior knowledge on the bounds of parameter variations for high performance. The resulting ARC controller achieves a prescribed output tracking transient performance and final tracking accuracy in the sense that the upper bound on the absolute value of the output tracking error over entire time‐history is given and related to certain controller design parameters in aknownform. Furthermore, in the absence of uncertain nonlinearities, asymptotic output tracking is also achieved. Copyright © 2001 John Wiley & Sons, Ltd.
Oscillation elimination of tip regulation for a single‐link flexible manipulator
Authors: Cao Wen‐Jun , Xu Jian‐Xin
Published: August 2002

Many existing variable structure control schemes for flexible manipulators use a conventional sliding surface, which is linear with respect to system states. It results in a reduced‐order sliding motion, i.e. the closed‐loop dynamics during ideal sliding has reduced number of eigenvalues to be assigned, and the fixed eigenvalue at the origin functions as integrator and may degrade system robustness. In this paper, an integral‐type sliding surface is proposed which obtains a full‐order sliding motion, such that all the eigenvalues of the closed‐loop dynamics can be assigned. The integral‐type sliding surface is derived from a reference model which does not have any finite zero but all negative real poles. In order to force the system to follow the reference model in the presence of the unstructured uncertainties, a variable structure controller is adopted. When in sliding mode, the system performs as the reference model. Hence there will be no vibration and the tip position regulation can be achieved when the system approaches steady‐state. Simulation results demonstrate the effectiveness of the proposed approach. Copyright © 2001 John Wiley & Sons, Ltd.
On relay feedback and chaotic systems
Authors: Sugiki Akihiko , Hatakeyama Shoshiro , Furuta Katsuhisa
Published: August 2002

The feedback connection of a linear system with a memoryless nonlinearity is recognized as a candidate for chaos‐generating structure. This paper proposes a chaotic nonlinear feedback system with a relay connected to a biproper linear system. The proposed chaotic system is analysed using chaos criteria proposed by Genesio and Tesi. This paper also shows an equivalence relation between the proposed system and the Brockett chaotic system through the linear input–output transformation. Copyright © 2001 John Wiley & Sons, Ltd.
Compositionality issues in discrete, continuous, and hybrid systems
Authors: van der Schaft A. J. , Schumacher J. M.
Published: August 2002

Models of complex dynamical systems are often built by connecting submodels of smaller parts. The key to this method is the operation of ‘interconnection’ or ‘composition’ which serves to define the whole in terms of its parts. In the setting of smooth differential equations the composition operation has often been regarded as trivial, but a quite different attitude is found in the discrete domain where several definitions of composition have been proposed and different semantics have been developed. The non‐triviality of composition carries over from discrete systems to hybrid systems. The paper discusses the compositionality issue in the context of discrete, continuous, and hybrid systems, mainly on the basis of a number of examples. Copyright © 2001 John Wiley & Sons, Ltd.
Hybrid control of force transients for multi‐point injection engines
Authors: Balluchi Andrea , Benvenuti Luca , Di Benedetto Maria Domenica , Sangiovanni‐Vincentelli Alberto L.
Published: August 2002

We address the problem of delivering as quickly as possible a requested torque produced by a spark ignition engine equipped with a multi‐point port injection manifold and with electronic throttle. The optimal control problem, subject to the constraint that the air–fuel ratio stays within a pre‐assigned range around the stoichiometric ratio, is solved for a detailed, cycle‐accurate hybrid model with a hybrid control approach based on a two‐step process. In the first step, a continuous approximation of the hybrid problem is solved exactly. Then, the control law so obtained is adjusted to satisfy the constraints imposed by the hybrid model. The quality of the control law has been in part analytically demonstrated and in part validated with simulations. Copyright © 2001 John Wiley & Sons, Ltd.
Pointing control design for a high precision flight telescope using quantitative feedback theory
Authors: Bentley Anthony E.
Published: August 2002

A pointing control system is developed and tested for a flying gimbaled telescope. The two‐axis pointing system is capable of sub‐microradian pointing stability and high accuracy in the presence of large host vehicle jitter. The telescope also has high agility — it is capable of a 50° retarget (in both axes simultaneously) in less than 2 s. To achieve the design specifications, high‐accuracy, high‐resolution, two‐speed resolvers were used, resulting in gimbal‐angle measurements stable to 1.5 µrad. In addition, on‐axis inertial angle displacement sensors were mounted on the telescope to provide host‐vehicle jitter cancellation. The inertial angle sensors are accurate to about 100 nrad, but do not measure low‐frequency displacements below 2 Hz. The gimbal command signal includes host‐vehicle attitude information, which is band‐limited. This provides jitter data below 20 Hz, but includes a variable latency between 15 and 25 ms. One of the most challenging aspects of this design was to combine the inertial‐angle‐sensor data with the less perfect information in the command signal to achieve maximum jitter reduction. The optimum blending of these two signals, along with the feedback compensation were designed using Quantitative Feedback Theory. Copyright © 2001 John Wiley & Sons, Ltd.
Experimental testing of a discrete‐time sliding mode controller for trajectory tracking of a wheeled mobile robot in the presence of skidding effects
Authors: Corradini M. Letizia , Leo T. , Orlando G.
Published: August 2002

This article addresses the trajectory tracking problem for a wheeled mobile base, considering the presence of disturbances that violate the nonholonomic constraint, and using an approximated discrete‐time model for the vehicle. The proposed solution is based on discrete‐time sliding mode control, in order to ensure that the controller is both robust and implementable. The asymptotic boundedness of the discrete‐time tracking errors is theoretically proved, and experimental results are reported, showing the effectiveness of the proposed control law. © 2002 Wiley Periodicals, Inc.
Globally asymptotically stable tracking control for a trailer system
Authors: Kim Doh‐Hyun , Oh Jun‐Ho
Published: August 2002

This article addresses a tracking controller design for a trailer system consisting of a steering tractor and a passive trailer linked with a rigid free joint and having nonholonomic constraints. We design the tracking controller using the Lyapunov direct method, for both forward and backward driving of the trailer system. Backward driving is unstable, and thus is more difficult than forward driving. In previous research, we proposed a globally asymptotically stable (GAS) tracking control for forward driving of a trailer system with nonholonomic constraints. In this article, we implement the GAS tracking controller for forward and backward driving, and perform experiments using visual feedback and remote control systems. The experimental results represent stable responses and demonstrate the effectiveness of our method. © 2002 Wiley Periodicals, Inc.
Autonomous selection and modification of camera configurations using visibility and manipulability measures
Authors: Chu Gil W. , Chung Myung J.
Published: August 2002

In this article, we present a camera control method in which the selection of an optimal camera position and the modification of camera configurations are accomplished according to changes in the surroundings. For the autonomous selection and modification of camera configurations during tasks, we consider the camera's visibility and the manipulator's manipulability. The visibility constraint guarantees that the whole of a target object can be “viewed” with no occlusions by the surroundings, and the manipulability constraint guarantees avoidance of the singular position of the manipulator and rapid modification of the camera position. By considering visibility and manipulability constraints simultaneously, we determine the optimal camera position and modify the camera configuration such that visual information for the target object can be obtained continuously during tasks. The results of simulations and experiments show that the active camera system with an eye‐in‐hand configuration can modify its configuration autonomously according to the motion of the surroundings by applying the proposed camera control method. © 2002 Wiley Periodicals, Inc.
Vision‐based terrain characterization and traversability assessment
Authors: Howard Ayanna , Seraji Homayoun
Published: August 2002

This article presents novel techniques for real‐time terrain characterization and assessment of terrain traversability for a field mobile robot using a vision system and artificial neural networks. The key terrain traversability characteristics are identified as roughness, slope, discontinuity, and hardness. These characteristics are extracted from imagery data obtained from cameras mounted on the robot and are represented in a fuzzy logic framework using perceptual, linguistic fuzzy sets. The approach adopted is highly robust and tolerant to imprecision and uncertainty inherent in sensing and perception of natural environments. The four traversability characteristics are combined to form a single Fuzzy Traversability Index, which quantifies the ease‐of‐traversal of the terrain by the mobile robot. Experimental results are presented to demonstrate the capability of the proposed approach for classification of different terrain segments based on their traversability. © 2001 John Wiley & Sons, Inc.
Responses of consumers and food resources to a high magnitude, unpredicted flood in the upper Mississippi River basin
Authors: Delong Michael D. , Thorp James H. , Greenwood Kim S. , Miller Michael C.
Published: August 2002

The Mississippi and Missouri Rivers experienced flooding in 1993 that fell outside the annual predictable flood period of spring and early summer. Flooding began in late June, peaked in late July (25 232 m3/s on the upper Mississippi and 21 240 m3/s on the Missouri) and remained at or near flood stage into October 1993. This study was performed to determine if disturbance by an unpredicted flood event would alter trophic dynamics of river–floodplain systems by creating shifts in the composition of organic matter available to consumers. The Ohio River, which did not flood during the same period, was examined for comparison. Stable isotopic ratios of carbon and nitrogen from samples collected in 1993 and 1994 were used to characterize potential food sources and determine linkages between food sources and invertebrate and fish consumers. Pairwise contrasts, performed separately for each river, indicated there were few interannual differences in δ13C and δ15N of organic matter sources and consumers. Between sample period (flood year versus normal water year) trends in both flooded rivers were similar to between‐year trends observed for the Ohio River. Trophic structure of the Mississippi and Ohio Rivers was similar in both years, with fine and ultra‐fine transported organic matter and dissolved organic matter representing the major sources of organic matter. Overlapping isotopic signatures in the Missouri River made tracking of sources through the consumers difficult, but similarities in δ13C and δ15N between years indicated trophic structure did not change in response to the flood. The results suggest that consumers continued to rely on sources of organic matter that would be used in the absence of the unpredicted 1993 flood. It is proposed that trophic structure did not change in response to flooding in the Mississippi and Missouri Rivers because both rivers exhibited the same trends observed in the Ohio River. Copyright © 2001 John Wiley & Sons, Ltd.
Distinctness of compositions of an integer: A probabilistic analysis
Authors: Hitczenko Paweł , Louchard Guy
Published: August 2002

Compositions of integers are used as theoretical models for many applications. The degree of distinctness of a composition is a natural and important parameter. In this article, we use as measure of distinctness the number of distinct parts (or components). We investigate, from a probabilistic point of view, the first empty part, the maximum part size and the distribution of the number of distinct part sizes. We obtain asymptotically, for the classical composition of an integer, the moments and an expression for a continuous distributionF, the (discrete) distribution of the number of distinct part sizes being computable fromF. We next analyze another composition: the Carlitz one, where two successive parts are different. We use tools such as analytical depoissonization, Mellin transforms, Markov chain potential theory, limiting hitting times, singularity analysis and perturbation analysis. © 2001 John Wiley & Sons, Inc. Random Struct. Alg., 19: 407–437, 2001
The average‐case area of Heilbronn‐type triangles*
Authors: Jiang Tao , Li Ming , Vitányi Paul
Published: August 2002

From among \documentclass{article}\pagestyle{empty}\begin{document}${n \choose 3}$\end{document} triangles with vertices chosen from n points in the unit square, let T be the one with the smallest area, and let A be the area of T. Heilbronn's triangle problem asks for the maximum value assumed by A over all choices of n points. We consider the average‐case: If the n points are chosen independently and at random (with a uniform distribution), then there exist positive constants c and C such that c/n3<μn<C/n3 for all large enough values of n, where μn is the expectation of A. Moreover, c/n3<A<C/n3, with probability close to one. Our proof uses the incompressibility method based on Kolmogorov complexity; it actually determines the area of the smallest triangle for an arrangement in “general position.” © 2002 Wiley Periodicals, Inc. Random Struct. Alg. 20: 206–219, 2002
Resource management model and performance evaluation for satellite communications
Authors: Jahn Axel
Published: August 2002

Efficient resource management is mandatory to achieve maximum system capacity for next generation communications systems. Resource management deals with the available spectral band, time, power, and space for a transmission signal. It includes (i) the frequency planning, (ii) the selection of transmit power, and (iii) the assignment of the channels and access nodes to the users. The paper presents a generalized notation as well as graph algorithms for resource management problems. Impairment graphs can be used for frequency planning, whereas flow graphs are suitable for channel access problems. To evaluate the performance of the resource management, service criteria (such as blocking or the carrier to interference ratioC/I) or efficiency criteria (bandwidth requirements) can be derived from the graphs. The resource management techniques are applied to satellite networks with non‐geostationary orbits yielding time‐variant network topologies. As a simple example, the channel assignment and capacity optimization of the EuroSky Way system are shown. Furthermore, a comparison of fixed, dynamic and hybrid channel allocation schemes (FCA, DCA, HCA) for a typical MEO satellite scenario is given. Satellite diversity and its impact on bandwidth requirement and transmission quality is also examined. Finally, it is shown how spread spectrum systems can be investigated with the presented tools. Copyright © 2001 John Wiley & Sons, Ltd.
Supporting node mobility using mobile IPv6 in a LEO‐satellite network
Authors: Sarikaya Behcet , Tasaki Masaru
Published: August 2002

This paper investigates supporting IPv6, the next generation IP in a Teledesic‐like low earth orbit (LEO) satellite backbone. The network architecture consists of LEO satellites with intersatellite links, gateway stations, standard terminals and mobile terminals. This network offers mobile data services like earth cellular networks. Due to its enlarged addressing space, IPv6 is selected as the network layer. For routing IPv6 datagrams in this network, a tunnelling approach is taken in which IPv6 datagrams from/to the Internet are fragmented/reassembled into ATM‐cell‐like packets. To route these packets inside the LEO‐constellation, we design a unicast link‐state routing algorithm in which the responsibilities for routing are shared between the satellites and gateway stations. For user mobility, Mobile IPv6 extended for paging the users in standby mode is used. The paper concludes with a presentation of simulation results. Copyright © 2001 John Wiley & Sons, Ltd.
Science, culture, and the emergence of language
Authors: Roth Wolff‐Michael , Lawless Daniel
Published: August 2002

A major achievement in the sociology and philosophy of science over the past two decades has been the recognition that science is a form of culture with its own creeds, language, material practices, perceptions, theories, and beliefs. Learning science then amounts to participation (from more peripheral to central ways) in the particular practices of this culture. We argue here that there are some fundamental, heretofore neglected, ways in which newcomers come to perceive and talk about natural phenomena. Beginning with “muddled” talk and supported by deictic and iconic gestures, learners isolate salient objects and events which are, in increasing ways, represented in linguistic forms. More abstract forms of communication (writing, abstract symbols) are competently used only later in the emerging communicative patterns. As such, there lies tremendous potential in science activities that focus on observational and theoretical language in the presence of the relevant phenomena. © 2002 Wiley Periodicals, Inc.Sci Ed86:368–385, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/sce.10008
On the substance of a sophisticated epistemology
Authors: Elby Andrew , Hammer David
Published: August 2002

Among researchers who study students' epistemologies, a consensus has emerged about what constitutes a sophisticated stance toward scientific knowledge. According to this community consensus, students should understand scientific knowledge as tentative and evolving, rather than certain and unchanging; subjectively tied to scientists' perspectives, rather than objectively inherent in nature; and individually or socially constructed, rather than discovered. Surveys, interview protocols, and other methods used to probe students' beliefs about scientific knowledge broadly reflect this outlook. This article questions the community consensus about epistemological sophistication. We do not suggest that scientific knowledge is objective and fixed; if forced to choose whether knowledge is certain or tentative, with no opportunity to elaborate, we would choose “tentative.” Instead, our critique consists of two lines of argument. First, the literature fails to distinguish between the correctness and productivity of an epistemological belief. For instance, elementary school students who believe that science is about discovering objective truths to questions, such as whether the earth is round or flat, or whether an asteroid led to the extinction of the dinosaurs, may be more likely to succeed in science than students who believe science is about telling stories that vary with one's perspective. Naïve realism, although incorrect (according to a broad consensus of philosophers and social scientists), may nonetheless be productive for helping those students learn. Second, according to the consensus view as reflected in commonly used surveys, epistemological sophistication consists of believing certain blanket generalizations about the nature of knowledge and learning, generalizations that do not attend to context. These generalizations are neither correct nor productive. For example, it would be unsophisticated for students to view as tentative the idea that the earth is round rather than flat. By contrast, they should take a more tentative stance toward theories of mass extinction. Nonetheless, many surveys and interview protocols tally students as sophisticated not for attending to these contextual nuances, but for subscribing broadly to the view that knowledge is tentative. © 2001 John Wiley & Sons, Inc. Sci Ed 85:554–567, 2001.
Toward inclusive science education: University scientists' views of students,instructional practices, and the nature of science
Authors: Bianchini Julie A. , Whitney David J. , Breton Therese D. , Hilton‐Brown Bryan A.
Published: August 2002

This study examined the perceptions and self‐reported practices of 18 scientists participating in a yearlong seminar series designed to explore issues of gender and ethnicity in science. Scientists and seminar were part of the Promoting Women and Scientific Literacy project, a curriculum transformation and professional development initiative undertaken by science, science education, and women's studies faculty at their university. Researchers treated participating scientists as critical friends able to bring clarity to and raise questions about conceptions of inclusion in science education. Through questionnaires and semistructured interviews, we explored their (a) rationales for differential student success in undergraduate science education; (b) self‐reports of ways they structure, teach, and assess courses to promote inclusion; and (c) views of androcentric and ethnocentric bias in science. Statistical analysis of questionnaires yielded few differences in scientists' views and reported practices by sex or across time. Qualitative analysis of interviews offered insight into how scientists can help address the problem of women and ethnic minorities in science education; constraints encountered in attempts to implement pedagogical and curricular innovations; and areas of consensus and debate across scientists and science studies scholars' descriptions of science. From our findings, we provided recommendations for other professional developers working with scientists to promote excellence and equity in undergraduate science education. © 2001 John Wiley & Sons, Inc.Sci Ed86:42–78, 2001.
Tagged communication and synchronization memory for multiprocessor‐on‐a‐chip
Authors: Iwane Masahiko , Yamawaki Akira , Tanaka Makoto
Published: August 2002

Multiprocessor‐on‐a‐chip is becoming possible due to progress in semiconductor technologies. In the multiprocessor, the threaded parallel processing requires decreasing the overhead of interthread communication and synchronization. We propose the tagged communication and synchronization memory with the access counter using CAM (TCSM) which supports a high‐speed mechanism for the mutual exclusion, the condition synchronization, the barrier synchronization, and the multicasting between the threads. TCSM allocates its entries dynamically and ensures the producer–consumer synchronization by valid/invalid state in the access count. The execution environment of the threads is protected because the tag of TCSM is used for identifying both the task which threads belong to and the storage used by threads. The MTA/TCSM multichip multiprocessor system has been developed to evaluate the multiprocessor‐on‐a‐chip including TCSM. As a result of the evaluation on MTA/TCSM, the overhead of interthread synchronization and communication using TCSM is lower than using the conventional shared memory. © 2001 Scripta Technica, Syst Comp Jpn, 32(4): 1–13, 2001
Endoscope system for high‐speed 3D measurement
Authors: Hasegawa Kazuhide , Sato Yukio
Published: August 2002

In this paper, we will describe a technique for realizing high‐speed 3D measurement through an endoscope by combination of the space encoding method with laser scanning and the 3D endoscope. In this technique, the striped pattern of light based on the space encoding method is guided to the endoscope tip and made to illuminate the object by using one of the two image guide shafts embedded in the 3D endoscope. The pattern light image after irradiation is acquired from a color CCD camera installed at the other image guide shaft. This is repeated with the required number of frames of the space encoded patterns, and the calculation of the distance value is performed based on the principle of triangulation. In the proposed technique, the range image (512 × 242 pixels) can be acquired in 0.6 second. Moreover, since a color CCD camera is used, acquisition of the color information of the object surface can also be realized. Experiments show that the measurement error depends on the distance from the tip of the endoscope and is about 1% of the measuring distance in the range of 20 to 40 mm from the tip region. The practical possibility of the proposed technique is confirmed by performing shape reconstruction from the measurement results. © 2001 Scripta Technica, Syst Comp Jpn, 32(8): 30–39, 2001
The role of financial institutions in the sustainable development of Lebanon
Authors: Mezher Toufic , Jamali Dima , Zreik Carine
Published: August 2002

After years of war, Lebanon is witnessing an era of reconstruction and development. Worldwide experience has proven, however, that development cannot and should not be accomplished at the expense of the environment and natural resources. Thus, guiding Lebanon towards a sustainable development path is a must. Lebanese financial institutions, which are a major player in the market, have the potential to accelerate the sustainable development of the country. This paper investigates the actual role played by Lebanese financial institutions in the quest for sustainable development and offers practical recommendations that should help this sector improve its performance regarding sustainability issues. Copyright © 2002 John Wiley & Sons, Ltd. and ERP Environment.
Cycles in the sky: understanding and managing business cycles in the airline market
Authors: Liehr Martin , Größler Andreas , Klein Martin , Milling Peter M.
Published: August 2002

The airline market is a highly cyclical business with relatively poor returns on invested capital. The fluctuations in the market put the carriers under severe economic pressure, and most of them lack strategies for cycle oriented behavior. The focus of the research conducted at Lufthansa German Airlines is the analysis of fundamental, cycle‐generating structures in the airline market and the identification of alternative strategies for effective “cycle‐management”. The system dynamics approach is combined with a statistical forecasting model—a combination that proved to be valuable for the analysis and management of airline business cycles. The article describes a successful system dynamics study in a complex and fast changing environment. Insights generated during the project work are now going to influence order policies for new commercial aircraft for the carrier. Copyright © 2001 John Wiley & Sons, Ltd.
Ellipsometric approach to the monitoring of tip–surface proximity in NFO
Authors: Bortchagovsky Eugene G.
Published: August 2002

This work continues the development of the proposed early ellipsometric approach to near‐field microscopy. It is devoted now to the demonstration of the possibility of monitoring the tip–surface distance at the tip's approach to a surface by analysis of the polarization state of scattered light. It is shown that such analysis distinguishes between different interferometric periods recorded at the approaching tip, so that it is possible to control the distance without restriction in one period. Such a method may be realized using a standard modern ellipsometer with a rotating analyser. Copyright © 2002 John Wiley & Sons, Ltd.
Combined STM, HREELS and ab initio study of the adsorption of uracil on Si(100)‐2 × 1
Authors: Lopez Alberto , Chen Qiao , Richardson Neville V.
Published: August 2002

Adsorption of the nucleic acid base uracil on Si(100)‐2 × 1 has been studied using scanning tunnelling microscopy (STM), high‐resolution electron energy‐loss spectroscopy (HREELS) and ab initio calculations. The STM images show that uracil is able to form ordered structures on the surface on which the molecules adsorb preferentially along dimer rows. The HREEL spectra show a stronger intensity of the in‐plane modes compared with the out‐of‐plane vibrations. This indicates that the orientation of the molecular plane is more upright. The observation of a distinctive Si–H band in the vibrational spectra of Si(100)‐2 × 1 exposed to uracil indicates that adsorption of the molecule occurs through cleavage of an O–H/N–H bond. The vibrational spectra show that only the enol tautomer interacts with the surface, mainly through cleavage of the OH bond and the formation of an Si–O linkage. Copyright © 2002 John Wiley & Sons, Ltd.
Spatio‐temporal modelling of rates for the construction of disease maps
Authors: MacNab Ying C. , Dean C. B.
Published: August 2002

There have been significant developments in disease mapping in the past few decades. The continual development of statistical methodology in this area is responsible for the growing popularity of disease mapping because of its potential usefulness in regional health planning, disease surveillance and intervention, and allocating health funding. Here we review the area of disease mapping where relative risks pertain to an event such as incidence or mortality over space and time. In particular we briefly discuss the use of generalized additive mixed models, an additive extension of generalized linear mixed models, for spatio‐temporal analysis of disease rates. To illustrate the procedures, we present an in‐depth analysis of infant mortality data in the province of British Columbia, Canada. The goals of the analysis are to produce more reliable small‐area estimates of mortality rates, assess spatial patterns over time, and examine risk trends at both global (provincial) and local (local health area) levels. Copyright © 2002 John Wiley & Sons, Ltd.
A review of multilevel theory for ecologic analyses
Authors: Greenland Sander
Published: August 2002

This paper reviews multilevel and conventional models for the analysis of ecologic (group, aggregate) data. It emphasizes the non‐separability of contextual (group‐level) effects and individual‐level effects that arises from the multilevel structure of the underlying effects. Contrary to common misperceptions, this problem afflicts ecologic studies in which the sole objective is to estimate contextual effects, as well as studies in which the objective is to estimate individual effects. Multilevel effects also severely complicate causal interpretations of model coefficients. Copyright © 2002 John Wiley & Sons, Ltd.
A comparison of handsearching versus MEDLINE searching to identify reports of randomized controlled trials
Authors: Hopewell S. , Clarke M. , Lusher A. , Lefebvre C. , Westby M.
Published: August 2002

This study aims to compare handsearching to a basic MEDLINE search for the identification of reports of randomized trials in specialized health care journals. Twenty‐two specialized health care journals, published in the U.K., were handsearched for all reports of controlled trials (as defined by the Cochrane Collaboration). The reports of trials, which were judged to be definitely randomized, were identified from a random sample of three years per journal and form one element of this study. A MEDLINE search using the publication type terms ‘randomized controlled trial’ and ‘controlled clinical trial’ was also performed for the same journal years. The reports of trials retrieved by handsearching were then compared against those retrieved from the MEDLINE search, to identify differences in retrieval between the two techniques. Reports of randomized trials identified by the MEDLINE search but not found by handsearching were individually assessed to see if they met the Cochrane eligibility criteria for a report of a randomized trial. A total of 714 reports of randomized trials were found by using a combination of both handsearching and MEDLINE searching. Of these, 369 (52 per cent) were identified only by handsearching and 32 (4 per cent) were identified only by MEDLINE searching. Of the reports identified only by handsearching, 252 had no MEDLINE record, of which 232 (92 per cent) were meeting abstracts or published in supplements; 117 (25 per cent) of the 462 reports of randomized trials which had a MEDLINE record were missed by the electronic search because they did not have either of the publication type terms ‘randomized controlled trial’ or ‘controlled clinical trial’. This proportion varied depending on when the reports of randomized trials were published (that is, before or after the introduction of the MEDLINE publication type terms above). The highest additional yield from handsearching compared to MEDLINE searching was for reports of randomized trials published prior to 1991 and from handsearching the non‐MEDLINE indexed parts of a journal. The results of this study suggest that a combination of MEDLINE and handsearching is required to identify adequately reports of randomized trials. © Crown copyright 2002. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.
Projecting the standard error of the Kaplan–Meier estimator
Authors: Cantor Alan B.
Published: August 2002

Clinical studies in which a major objective is to produce Kaplan–Meier estimates of survival probabilities should be designed to produce those estimates with a desired prespecified precision as measured by their standard errors. By considering the Peto and Greenwood formulae for the estimated standard error of the Kaplan–Meier estimate and replacing their constituents with expected values based on the study's design parameters, formulae for projected standard errors can be produced. These formulae are shown, through simulations, to be quite accurate. Copyright © 2001 John Wiley & Sons, Ltd.
Item response models for joint analysis of quality of life and survival
Authors: Wang Chen , Douglas Jeffrey , Anderson Susan
Published: August 2002

A complication when assessing quality of life data longitudinally is that in many trials a substantial percentage of patients die before completing all of the assessments. Furthermore, a patient's risk of dying might be predicted by his current quality of life. This suggests jointly modelling quality of life and survival, and using this combined information to summarize the outcome. The aim of this paper is to address the complicated issues, such as death, present in analysing multiple‐item ordinal quality of life data in clinical trials while recognizing the psychometric properties of the quality of life instrument being used. This is done by combining an item response model and Cox's proportional hazard model, where a latent variable process for quality of life determines the probability of selecting various options on quality of life items, and also serves as a time‐dependent covariate in the survival model. We accomplish this by using Markov chain Monte Carlo methods to obtain parameter estimates. Then we compute a summary measure, area‐under‐QOL curve, to compare the efficacy of the treatments. The methods are illustrated with analysis of data from the Vesnarinone trial of patients with severe heart failure, in which quality of life was assessed with the Minnesota Living with Heart Failure Questionnaire. Copyright © 2002 John Wiley & Sons, Ltd.
My world is ok, but yours is not: television news, the optimism gap, and stress
Authors: McNaughton‐Cassill Mary E. , Smith Tom
Published: August 2002

Public opinion polls reliably find a disparity between people's views of the state of their own communities and of the nation in general. This discrepancy, frequently called the Optimism Gap, is often attributed to the fact that people have personal knowledge of things around them, but derive their larger world‐view from media sources such as television, which tend to over emphasize the negative, risky aspects of life. This study explores this premise, as well as the possibility that emotional factors such as depression, anxiety, and anger also play a role. Data from 171 participants were analysed. Overall, people rated problems in the nation in general as more severe than those in their own communities. Television exposure was predictive of ratings of problems nationwide, but not of problems in respondents' own communities, while attention paid to the television news was related to ratings of national and community problems. Depression, irrational beliefs, and anger arousal were all related to ratings of problems in the nation in general, while anger arousal and optimism were predictive of ratings of problems in respondents' own communities. These findings suggest that the links between television news exposure and mental health should be explored further. Copyright © 2002 John Wiley & Sons, Ltd.
Mental health problems and British workers: a survey of mental health problems in employees who receive counselling from Employee Assistance Programmes
Authors: Arthur Andrew R.
Published: August 2002

This study assesses levels of psychological disturbance in employees who attend counselling schemes provided by their employer through Employee Assistance Programmes (EAPs). Over two‐thirds (33) of the organizations covered by a major United Kingdom EAP provider allowed their employees to be surveyed. A standardized and well‐respected screening test aimed at detecting psychiatric disorders in the community (General Health Questionnaire) was given to employees when they visited counsellors. Steps were taken to ensure confidentiality and anonymity. One hundred and eleven of 466 (24 per cent) employees receiving counselling returned questionnaires and the results show 86.6 per cent of these experienced significantly high levels of psychiatric problems. Findings suggest that a significant proportion of employees who experience stress in the workplace and consequently attend their employer's EAP may have serious mental health symptoms, and that employers are providing a service for those in genuine psychological need. The study also raises the possibility that when some employees complain of ‘stress’ in the workplace, they may in fact be experiencing significant mental health problems, particularly anxiety and depression, requiring professional assistance. Copyright © 2002 John Wiley & Sons, Ltd.
Market position, resource profile, and governance: linking Porter and Williamson in the context of international courier and small package services in Japan
Authors: Nickerson Jack A. , Hamilton Barton H. , Wada Tetsuo
Published: August 2002

Two economic theories that have had an immense impact on modern strategic management research are Porter's strategic positioning framework (SPF) and Williamson's transaction cost economics (TCE). While both theories have contributed to our understanding of strategic management and to the choice of strategy and structure, each theory offers managerial prescriptions that are incomplete at best. We contend that if followed in isolation, each theory can lead to inferior performance. This paper, which studies the international courier and small package (IC&SP) services in Japan, improves upon prescriptions from both theories by linking Porter's and Williamson's approaches. Our main proposition is contained in three relationships that predict a fit among three strategic choices: market position, resource profile, and organizational structure. We test our predictions with a three‐stage, reduced‐form, endogenous self‐selection model. While our empirical methodology is complicated and relies on a multilevel analysis, the methodology is necessary both for analyzing a constellation of activities in the vertical chain and for assessing strategy, structure, and performance when data can be drawn from only a limited number of firms. Our results suggest that a firm's market position, resource profile, and organizational choice are related in ways predicted by a positioning‐economizing perspective. To be sure, our study is ambitious and suffers from a number of limitations; nevertheless, it provides one of the first attempts to theoretically and empirically link Porter's SPF and Williamson's TCE. Copyright © 2001 John Wiley & Sons, Ltd.
Incumbent's advantage through exploiting complementary assets via interfirm cooperation
Authors: Rothaermel Frank T.
Published: August 2002

I examine interfirm cooperation between incumbents and new entrants as a mechanism for incumbents to adapt to radical technological change through exploitation of complementary assets. The research setting is the biopharmaceutical industry, where I analyze 889 strategic alliances between 32 large pharmaceutical firms and providers of the new biotechnology. I find that incumbents that focus their network strategy on exploiting complementary assets outperform incumbents that focus on exploring the new technology. However, there are limits to this strategy due to diminishing marginal returns to alliance intensity. I am also able to show that an incumbent's new product development is positively associated with its performance. Copyright © 2001 John Wiley & Sons, Ltd.
Characteristics of ERP software maintenance: a multiple case study
Authors: Nah Fiona Fui‐Hoon , Faja Silvana , Cata Teuta
Published: August 2002

A multiple case study approach was employed to identify maintenance activities pertaining to enterprise resource planning (ERP) implementation, classify them into maintenance categories, and assess their relative frequency at various stages of the ERP maintenance lifecycle. Five maintenance categories (corrective, adaptive, perfective, preventive, user support) were identified from a review of the literature on software maintenance. A new category pertaining to ‘communication, coordination and knowledge exchange with external parties’ and herein labeled ‘external parties’ is introduced to highlight the supporting role of external parties in ERP maintenance. This category includes reporting problems to vendors and consultants, tracking their progress towards problem resolution, and coordinating work and relations with vendors, consultants, and external user‐organizations. This study also highlights some differences between maintenance trends of ERP versus traditional systems. Copyright © 2001 John Wiley & Sons, Ltd.
Maintaining traceability links during object‐oriented software evolution
Authors: Antoniol G. , Canfora G. , Casazza G. , De Lucia A.
Published: August 2002

This paper presents a method to build and maintain traceability links and properties of a set of object‐oriented software releases. The method recovers an ‘as is’ design from C++ software releases, compares recovered designs at the class interface level, and helps the user to deal with inconsistencies by pointing out regions of code where differences are concentrated. The comparison step exploits edit distance and a maximum match algorithm. The method has been experimented with on two freely available C++ systems. Results as well as examples of applications to the visualization of the traceability information and to the estimation of the size of changes during maintenance are reported in the paper. Copyright © 2001 John Wiley & Sons, Ltd.
Design and implementation of a video browsing system for the Internet
Authors: Tavanapong Wallapak , Hua Kien A.
Published: August 2002

Recent advances in multimedia processing technologies, internet‐working technologies, and the World Wide Web phenomenon have resulted in a vast creation and use of digital videos. Due to this reason, an efficient technique to locate and retrieve a desired video from a remote video archive is needed. A trial‐and‐error approach popularly used in current Web search engines is not applicable for searching for a desired video segment since the technique incurs intolerable delays. In this paper, we present the design and implementation of a video browsing system that lets the user view a summary of a selected video and search within the video while being downloaded so that the user can determine the relevance of the video as early as possible. The system is inexpensive and scalable, making it suitable for large‐scale distributed systems such as the Internet. The browsing system consists of two major software components: a video server, and a video browser and player calledVideoCenterimplemented using Microsoft DirectShow multimedia development kit. The implementation of VideoCenter enables us to assess the ease of use of DirectShow as well as its drawbacks in developing multimedia applications. Copyright © 2001 John Wiley & Sons, Ltd.
A sociological systems theory of interorganizational network development in health and social care
Authors: van Raak Arno , Paulus Aggie
Published: August 2002

In the health and social care sectors of European countries the number of regional interorganizational networks of providers is growing. Since facilitating development of such networks for the purpose of multi‐agency working increasingly becomes an issue, theories must be drawn up to understand network development, possible absence of development included. We have taken up the challenge. Based on empirical data and elaborating on the work of authoritative authors we formulated a sociological systems theory on interorganizational network development. Here we present the theory, which is the result of a case study in the Dutch care sector. In our theory, we consider interorganizational networks as social systems. Therefore, we used knowledge from social system theory. However, we added knowledge from interactionism, especially the concept of ‘meaning’. It is argued that the combination of both perspectives into one theory allows a better understanding of network development. The concept of ‘steering’ is the junction where the perspectives meet. Copyright © 2001 John Wiley & Sons, Ltd.