bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of glycopeptide structures by multistage mass spectrometry with low‐energy collision‐induced dissociation: comparison of electrospray ionization quadrupole ion trap and matrix‐assisted laser desorption/ionization quadrupole ion trap reflectron time‐of‐flight approaches
Authors: Demelbauer Uwe M. , Zehl Martin , Plematl Alexander , Allmaier Günter , Rizzi Andreas
Published: June 2004

Multistage mass spectrometry, as implemented using low‐energy collision‐induced dissociation (CID) analysis in three‐dimensional (3D) quadrupole ion traps (QITs), has become a powerful tool for the investigation of protein glycosylation. In addition to the well‐known combination of QITs with electrospray ionization (ESI), also a matrix‐assisted laser desorption/ionization—quadrupole ion trap—reflectron time‐of‐flight (MALDI‐QIT‐rTOF) mass spectrometer has recently become available. This study systematically investigates the differences between these types of instrument, as applied to characterization of glycopeptides from human antithrombin. The glycopeptides were obtained by tryptic digestion followed by lectin‐affinity purification. Some significant differences between the ESI‐QIT and MALDI‐QIT‐rTOF approaches appeared, most of them are causally related to the desorption/ionization process. The combination of a vacuum MALDI source with an ion‐trap analyzer accentuates some characteristic differences between MALDI and ESI due the longer time frame needed for the trapping process. In contrast to ESI, MALDI generated ions that exhibited considerable metastable fragmentation during trapping. The long time span of the QIT process (ms range) compared with that for conventional rTOF experiments (μs range) significantly magnified the extent of this metastable fragmentation. With the investigated glycopeptides, a complete depletion of the terminal sialic acids of the glycopeptides as well as a variety of other fragment ions was already found in the MS1 spectra from the MALDI‐QIT‐rTOF instrument. The positive ion low‐energy CID spectra (MS2) of the selected glycopeptides obtained using the two different QIT equipped instruments were found to be quite similar. In both approaches, fragmentation of the glycan and peptide structures occurred sequentially, allowing unambiguous sequence determination. In the case of ESI‐QIT‐MS, fragmentation of the glycan structure occurred at the MS2 stage and fragmentation of the peptide structure was obtained only at the MS3 stage, which indicates the necessity of multistage CID experiments for complete structure elucidation. The MALDI‐QIT‐rTOF instrument yielded both kinds of fragments at the MS2 stage but without mutual interference. Copyright © 2004 John Wiley & Sons, Ltd.
Liquid chromatographic analysis of nucleosides and their mono‐, di‐ and triphosphates using porous graphitic carbon stationary phase coupled with electrospray mass spectrometry
Authors: Xing Jinsong , Apedo Atsu , Tymiak Adrienne , Zhao Ning
Published: June 2004

Analysis of nucleosides and nucleotides is desirable in many biological studies, but the task is analytically challenging due to the high polarity of the analytes. In this study, resolution of mixtures containing nucleosides and their mono‐, di‐ and triphosphates was achieved using a porous graphitic carbon (PGC) stationary phase, Hypercarb, under conditions suitable for liquid chromatography/mass spectrometry (LC/MS). Different organic mobile phases and modifiers were evaluated and the separation of 16 nucleosides and nucleotides was optimized using gradient elution with a water/acetonitrile mobile phase containing ammonium acetate and diethylamine as modifiers. The ammonium acetate concentration proved to be critical for retention and diethylamine was found to improve the peak shapes of di‐ and triphosphates for mass spectrometric detection. A variety of silica‐based columns designed for polar compound separation were also tested using optimized LC conditions and compared with results obtained with the Hypercarb column. Only the Hypercarb column provided separations suitable for accurate quantitation of mixed nucleosides and their phosphates. Copyright © 2004 John Wiley & Sons, Ltd.
Electron capture dissociation Fourier transform ion cyclotron resonance mass spectrometry in the electron energy range 0–50 eV
Authors: Tsybin Youri O. , Witt Matthias , Baykut Gökhan , Håkansson Per
Published: June 2004

Electron capture dissociation (ECD) of polypeptide cations was obtained with pencil and hollow electron beams for both sidekick and gas‐assisted dynamic ion trapping (GADT) using Fourier transform ion cyclotron resonance mass spectrometry (FTICR‐MS) with an electrostatic ion transfer line. Increasing the number of trapped ions by multiple ICR trap loads using GADT improved the ECD sensitivity in comparison with sidekick ion trapping and ECD efficiency in comparison with single ion trap load by GADT. Furthermore, enhanced sensitivity made it possible to observe ECD in a wide range of electron energies (0–50 eV). The degree, rate and fragmentation characteristics of ECD FTICR‐MS were investigated as functions of electron energy, electron irradiation time, electron flux and ion trapping parameters for this broad energy range. The results obtained show that the rate of ECD is higher for more energetic (>1 eV) electrons. Long electron irradiation time with energetic electrons reduces average fragment ion mass and decreases efficiency of formation of c‐ and z‐type ions. The obtained dependencies suggest that the average fragment ion mass and the ECD efficiency are functions of the total fluence of the electron beam (electron energy multiplied by irradiation time). The measured electron energy distributions in low‐energy ECD and hot ECD regimes are about 1 eV at full width half maximum in employed experimental configurations. Copyright © 2004 John Wiley & Sons, Ltd.
DVB‐S2 low density parity check codes with near Shannon limit performance
Authors: Eroz Mustafa , Sun Feng‐Wen , Lee Lin‐Nan
Published: June 2004

Low density parity check (LDPC) codes are chosen for the second generation digital video broadcasting (DVB) standard. In this paper, we review LDPC codes in general, present belief propagation decoding algorithm in simple terms, describe the standardized LDPC codes and show their performance. Copyright © 2004 John Wiley & Sons, Ltd.
DVB‐S2, the second generation standard for satellite broadcasting and unicasting
Authors: Morello Alberto , Reimers Ulrich
Published: June 2004

DVB‐S2 is the second‐generation specification for satellite broadcasting developed by the DVB Project in 2003 and needs to be seen in conjunction with the world‐famous DVB‐S specification which was finalized in 1993. It benefits from more recent developments in channel coding (LDPC codes) combined with a variety of modulation formats (QPSK, 8PSK, 16APSK and 32APSK). When used for interactive point‐to‐point applications like IP‐based service navigation, it may implement adaptive coding and modulation (ACM), thus allowing the transmission parameters to be optimized for each individual user, dependent on path conditions. Backwards compatible modes are available, allowing existing DVB‐S services and Set Top Boxes (STBs) to continue working during any transitional period. Copyright © 2004 John Wiley & Sons, Ltd.
DVB‐S2 modem algorithms design and performance over typical satellite channels
Authors: Casini E. , Gaudenzi R. De , Ginesi A.
Published: June 2004

In this paper we propose a design of the main modulation and demodulation units of a modem compliant with the new DVB‐S2 standard (Int. J. Satellite Commun. 2004; 22:249–268). A typical satellite channel model consistent with the targeted applications of the aforementioned standard is assumed. In particular, non‐linear pre‐compensation as well as synchronization techniques are described in detail and their performance assessed by means of analysis and computer simulations. The proposed algorithms are shown to provide a good trade‐off between complexity and performance and they apply to both the broadcast and the unicast profiles, the latter allowing the exploitation of adaptive coding and modulation (ACM) (Proceedings of the 20th AIAA Satellite Communication Systems Conference, Montreal, AIAA‐paper 2002‐1863, May 2002). Finally, end‐to‐end system performances in term of BER versus the signal‐to‐noise ratio are shown as a result of extensive computer simulations. The whole communication chain is modelled in these simulations, including the BCH and LDPC coder, the modulator with the pre‐distortion techniques, the satellite transponder model with its typical impairments, the downlink chain inclusive of the RF‐front‐end phase noise, the demodulator with the synchronization sub‐system units and finally the LDPC and BCH decoders. Copyright © 2004 John Wiley & Sons, Ltd.
Frame synchronization and pilot structure for second generation DVB via satellites
Authors: Sun Feng‐Wen , Jiang Yimin , Lee Lin‐Nan
Published: June 2004

Due to the advanced coding schemes utilized in DVB‐S2, new receivers have to function at unprecedented low SNR. From the perspective of synchronization, the major challenges are frame synchronization and carrier recovery. The challenge for frame synchronization arises from the fact that the frames of LDPC are rather long, up to 32 400 symbols, and there is no built‐in structure in the LDPC to facilitate frame synchronization. Carrier recovery becomes a major challenge due to the requirement to retain the current outdoor equipment. This implies that the receivers have to work with the same phase noise as specified for the first generation DVB‐S, which uses only QPSK modulation. DVB‐S2 needs to support QPSK at much lower signal to noise ratios (SNR) and other higher order modulation schemes at about the same SNR of DVB‐S.

In this paper, we will describe the solutions to frame synchronization and carrier recovery. Low overhead rapid frame synchronization is achieved by utilizing the physical layer signalling code. Robust carrier recovery is aided by the aggregated pilot structure. The design considerations for the pilot structure and the implementation tradeoffs of the carrier recovery schemes are addressed. Copyright © 2004 John Wiley & Sons, Ltd.
DVB‐S2 backward‐compatible modes: a bridge between the present and the future
Authors: Chen Ernest , Koslov Joshua L. , Mignone Vittoria , Santoru Joseph
Published: June 2004

The second generation Digital Video Broadcasting (DVB) system for satellite broadcasting (DVB‐S2) has been standardized including tools to allow backward compatibility (BC) with the operating standard DVB‐S (EN 300 421, Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for 11/12 GHz satellite services. V.1.1.2, August 1997, http://www.etsi.org). Two conceptual ways of implementing BC have been defined: hierarchical modulation and layered modulation.

The paper describes the standardized backward‐compatible modes and presents the results of analytical investigations and simulations of the system in various configurations, as carried out by DIRECTV, Rai‐CRIT and Thomson. Copyright © 2004 John Wiley & Sons, Ltd.
Evaluation of a compiler with user‐selectable execution strategies for parallel recursion
Authors: Mizutani Yasuharu , Nakajima Daisuke , Fujimoto Noriyuki , Hagihara Kenichi
Published: June 2004

The strategy of evenly distributing processors to each recursive call and the strategy of performing dynamic load‐balancing exist as strategies for executing parallel recursions. There are cases in which an execution strategy efficient for a certain parallel recursive algorithm is not efficient for another parallel recursive algorithm depending on the operation of the parallel recursion algorithm. In addition, there are cases in which the execution efficiency decreases due to overparallelization of recursive calls due to factors such as the communication efficiency of a parallel computing environment. On the one hand, it is not easy for a compiler to analyze these factors mechanically from source programs of a parallel recursive algorithm, select an optimal execution strategy, and suppress overparallelization. In general, in many cases, a programmer understands parallel recursive algorithms and can predict which execution strategy is suitable for the algorithm. Thus, if a programmer can specify a parallel recursive execution strategy or specify a decision to suppress overparallelization, parallel recursive algorithms can be executed efficiently. This paper proposes a strategy for a programmer to clearly designate information useful for efficiently executing parallel recursion. In addition, it shows differences in the performance of various execution strategies of parallel recursive algorithms and shows the usefulness of a programmer having the capability to select an execution strategy. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(9): 92–103, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10009
A new environment for improving legacy software on embedded systems
Authors: Sakai Makoto , Kubota Masunori , Okita Masaya , Matsumoto Ken‐ichi , Torii Koji
Published: June 2004

In this paper, the authors propose a method of evaluating the module structure of programs for embedded software in which maintainability has deteriorated due to repeated revisions and also describe a software improvement support tool that was developed based on the proposed method. The proposed evaluation method supports the improvement of a module structure that includes the exchange of data according to external variables, which is often used in embedded software, by applying the concepts of intermodule coupling and module cohesion from structured analysis. The support tool also has the following special features: (1) by displaying the exchange of data according to external variables as an interface with a higher‐level function, it can display the “data flow between hierarchically related modules,” which could not be displayed by conventional tools, (2) by using open source tools, it can be implemented with relatively few man‐hours, and (3) it provides design guides and checklists that enable the software improvement method to be learned in a short period without regard to user expertise. From the results obtained when this tool was introduced in actual projects, it was apparent that the tool was effective in discovering and improving program structures that caused a deterioration of maintainability. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(9): 81–91, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10023
Robust object detection and segmentation by peripheral increment sign correlation image
Authors: Satoh Yutaka , Kaneko Shun'ichi , Igarashi Satoru
Published: June 2004

This paper proposes the peripheral increment sign correlation image, which can be used to evaluate sign changes of the neighborhood brightness. Based on the technique, a robust method is presented for detection and separation of the object emerging from the image time sequence, with the following features. (1) The result is not affected by the brightness distribution of the emerging object. (2) The result is not affected by brightness change of the background. The peripheral increment sign correlation image is constructed from only the trend of the brightness changes in the neighborhood of the pixel under consideration. Consequently, the image is highly robust to brightness changes over the sequence, and the similarity of the original texture pattern can be detected even if there is a brightness change. Furthermore, it does not require complex preprocessing or parameter setting, and a high‐density difference image can be directly derived. Through experiments using real images with various conditions, it is verified that difference extraction which is robust to brightness change can be realized, indicating the effectiveness of the approach. An application experiment is performed to extract the emerging object area in a scene, and it is verified that segmentation can be performed while retaining good contours and continuity by adding a relatively simple filter sequence as postprocessing. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(9): 70–80, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10241
Monte Carlo analysis of near‐infrared light propagation in a neonatal head model
Authors: Eda Shuhei , Okada Eiji
Published: June 2004

In brain function measurement using near‐infrared light, it is very important to make a theoretical analysis of light propagation in the head tissue, since it is impossible to measure the effect of optical fiber arrangement on the region of measurement or its sensitivity. The Monte Carlo method is widely used in the analysis of near‐infrared light propagation in biological tissue, since it allows light propagation analysis of heterogeneous tissue by a relatively simple algorithm. In this study, a model simulating the cross‐sectional structure of the neonatal head is constructed by using square elements, and the light propagation is analyzed. First, the variance‐reduction (VR) method and the delta‐scattering (DS) method, which are typical algorithms of the Monte Carlo method, are applied to the model composed of square elements, and the results of the analysis and the computation time for light propagation are compared and discussed. It is shown that the DS method is useful for a model composed of small square elements, since the computation time depends little on the size of the elements. As a result of analysis of light propagation in the neonatal head model using the DS method, we see that light propagation is greatly affected by the heterogeneity of the head tissue. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(9): 60–69, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10246
Optical flow detection using segmentation and MDL criterion
Authors: Tsuchiya Hideaki , Uemura Noburu , Itoh Shuichi
Published: June 2004

Kanatani applied the concept of noise to optical flow calculation using the constraint equation proposed by Horn, and presented a renormalization method which estimates the flow and the noise components simultaneously. In the renormalization method, the image is segmented into blocks, and the constraint that flows of the pixels in a block remain the same is assumed. This paper applies MDL criterion to the renormalization method and proposes an optical flow estimation algorithm that segments the image self‐organizationally. It is assumed that the sender has a pair of images from time‐ordered sequence and the receiver has one of these images. In this assumption, the image segmentation is determined by using MDL criterion so that the intensity gradient vectors generated from the image pair are encoded most efficiently. Each intensity gradient vector is encoded to two components, namely, the flow vector and the error. The image segmentation and the flow vectors obtained by this procedure are defined as the estimated optical flows. As an experiment, the algorithm is applied to artificial image pairs and a real image pair and the results are presented. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(9): 51–59, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10335
A system for supporting collaborative learning with networked sensing boards
Authors: Sugimoto Masanori , Kusunoki Fusako , Inagaki Shigenori , Takatoki Kuniyoshi , Yoshikawa Atsushi
Published: June 2004

The authors have used sensing boards based on RFID technology to construct a face‐to‐face group learning support system integrating the physical world and the virtual world. The system is shown to be useful through performance in that a learner without sufficient skill in using a computer can easily participate in learning, and knowledge acquired through textbooks and the like can be tested in the physical world. On the other hand, some problems have been pointed out: the utterances depend more strongly on the leader, and learning support with a higher degree of realism is desired. Consequently, in the system proposed in this paper, multiple sensing boards are placed at different sites so that the learner groups can communicate face‐to‐face. The sensing boards are connected through a network so that the operations on the board can influence each other. The learners in the group gather around the board and try to solve the problem face‐to‐face. They also interact with the learners in another group through a chat system. The learners in a primary school classroom used the system to study city design and environmental problems, and the effectiveness of the proposed system was demonstrated. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(9): 39–50, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10502
Estimation of true Mahalanobis distance from eigenvectors of sample covariance matrix
Authors: Iwamura Masakazu , Omachi Shinichiro , Aso Hirotomo
Published: June 2004

In statistical pattern recognition, the Bayesian decision theory gives a decision that minimizes the expected probability of misclassification as long as the true distributions are given. However, in most practical situations, the true distributions are unknown, and the parameters of the distributions are usually estimated from training sample vectors. It is well known that estimated parameters contain estimation errors when the sample size is small, and the errors have a negative influence on recognition performance. Among the estimation errors of parameters, the estimation errors of eigenvectors have not been sufficiently considered. In this paper, we present a method to estimate the true Mahalanobis distance from the sample eigenvectors (the eigenvectors of sample covariance matrix) by considering the estimation errors of eigenvectors. Recognition experiments show that the true Mahalanobis distance can be estimated, and better recognition accuracy is achieved by applying the proposed method without many training samples and any hyperparameters. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(9): 30–38, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10519
Curved document imaging with eye scanner
Authors: Amano Toshiyuki , Abe Tsutomu , Nishikawa Osamu , Iyoda Tetsuo , Sato Yukio
Published: June 2004

In conventional document imaging by a copying machine, the item to be copied must be held flat at a specified position. In addition, distortion or blurring can be produced when an object with three‐dimensional undulations is imaged. Consequently, we developed a next‐generation document imaging device (Eye Scanner) which can image characters or photographs on a curved sheet from an arbitrary viewpoint, without contact and without distortion, by utilizing shape information. This paper gives an outline of the Eye Scanner device and proposes a method of eliminating texture distortion of a curved object imaged from an arbitrary viewpoint. A divided imaging and connection method by using a pan‐tilt stage is presented. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(9): 20–29, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10558
Object detection/classification by probabilistic local matching
Authors: Yamaoka Megumi , Nagao Kenji
Published: June 2004

A new method for object detection and classification based on their shapes in images is presented. In the new method, to describe objects and match them with the models, local photometric features are incorporated with global shape features in a probabilistic framework, which is an extension of conventional approaches to geometric object recognition. Results demonstrate the effectiveness of the proposed method in vehicle detection in road images with background clutter, as well as in face detection under varying lighting conditions. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(9): 10–19, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10641
Robust feature extraction method based on run‐length compensation for degraded character recognition
Authors: Mori Minoru , Sawaki Minako , Hagita Norihiro , Murase Hiroshi , Mukawa Naoki
Published: June 2004

Conventional features are robust for recognizing either deformed or degraded characters. Most conventional character recognition methods address either one or the other. This paper proposes a feature extraction method that is robust for both of them. Run‐length compensation is introduced for approximately extracting directional run‐lengths of strokes from degraded handwritten characters. This technique is applied to the conventional feature vector based on directional run‐lengths. Experiments for handwritten characters with additive or subtractive noise show that the proposed feature is superior to conventional ones over a wide range of the degree of noise. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(9): 1–9, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10643
A neural net architecture for hardware implementation of a temporal pattern discrimination model
Authors: Takahashi Sei , Sekine Yoshifumi
Published: June 2004

This paper proposes a neural net architecture for hardware implementation of a temporal pattern discrimination model. The elements constituting the hardware have the characteristics of delays, thresholds, and refractoriness that are useful for implementing a model in hardware. First, it shows that a temporal pattern short‐term memory structure, similar to TDNN, can be implemented by connecting the hardware elements only serially. Next, it constructs a neocognitron‐type temporal data recognition model (Neo‐TDRM) using this short‐term memory structure by using a neocognitron that is robust with respect to pattern positional lags or shape changes as a discrimination model. Results of computer simulation of single‐channel mouse brain wave discrimination experiments show that the system can correctly discriminate even waveforms that are extended or contracted temporally or spatially. In addition, the proposed model is shown to be suitable for hardware implementation compared with the neocognitron constructed for similar discrimination experiments from the point of view of the number of cells or the number of wires required, since the number of cells of the Neo‐TDRM can be reduced to about 1/4 and the number of wires to about 1/18. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(9): 104–112, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.20075
A new approach for interval estimation and hypothesis testing of a certain intraclass correlation coefficient: the generalized variable method
Authors: Tian Lili , Cappelleri Joseph C.
Published: June 2004

We consider the problems of interval estimation and hypothesis testing for the intraclass correlation coefficient in an interrater reliability study when both raters and subjects are assumed to be randomly selected from populations of raters and subjects, respectively. We propose a novel approach for the confidence interval estimation and hypothesis testing using the concepts of generalized confidence interval (GCI) and generalizedP‐values. A simulation study is conducted to investigate the coverage probabilities of the GCI approach relative to the modified large sample (MLS) approach. Both methods tend to provide somewhat conservative coverage. Relative to the MLS approach, the GCI approach is closer to the correct (nominal) coverage for a two‐sided interval, but farther to the correct coverage for a one‐sided lower interval. Unlike the MLS approach, the GCI approach can also easily provideP‐values. The fact that the GCI approach is suitable for confidence interval estimation and obtainingP‐values makes the GCI approach a suitable candidate for making inference about interrater reliability. Copyright© 2004 John Wiley & Sons, Ltd.
Adjusting SIDS rates by seasonality in births in Minnesota
Authors: Wall Melanie M.
Published: June 2004

This paper is concerned with the formation of sudden infant death syndrome (SIDS) rates over time. Because of differential numbers of births throughout the year, a new SIDS rate is developed that takes into account the changing number of infants at risk and in particular the changing age distribution throughout the year. Differences between this newly adjusted rate and the commonly used unadjusted rates will be presented. Data from Minnesota linked birth–death records from 1990–1998 will be used for analysis. Copyright 2004 John Wiley & Sons, Ltd.
Consequences of event rate heterogeneity across non‐randomized study sub‐groups
Authors: Eberly Lynn E.
Published: June 2004

Analyses to compare non‐randomized groups are more and more common in bothpost hocanalyses of randomized clinical trials data and in analyses of long‐term observational data. In such cases, it is quite likely that there are unknown or uncollected sources of heterogeneity in event rates. Research has shown that an underlying source of heterogeneity in event rates which is not included in proportional hazards regression models leads to biased estimates for included covariate effect estimates and lower power to test them whether the source of heterogeneity is assumed to be fixed or random.

We demonstrate here using severalpost hocanalyses of clinical trials data that a potentially common problem may be that the non‐randomized groups which are to be compared have differential variability in their event rates. We then show through simulation that such underlying heterogeneity which varies across the groups, when ignored in the modelling, can lead to an attenuated regression effect estimate for comparing the two groups to each other, lower rejection rates for the effect, and Wald‐based confidence intervals with potentially much lower coverage than nominal. When the groups are not significantly different, but heterogeneity differs between them, an analysis ignoring the heterogeneity can even result in a significant negative comparison. Copyright © 2004 John Wiley & Sons, Ltd.
13C‐urea breath test for Helicobacter pylori in young children: cut‐off point determination by finite mixture model
Authors: X. Du Joanna , Watkins Terry , Bravo Luis E. , Fontham Elizabeth T. H. , Camargo M. Constanza , Correa Pelayo , Mera Robertino
Published: June 2004

The 13C‐urea breath test (UBT) is currently regarded as one of the most important noninvasive diagnostic methods for detecting Helicobacter pylori (H. pylori) infection in adults and children. However, for infants and young children, the standard for UBT interpretation has not been validated, and its reliability has not been established for diagnosing H. pylori infection in this group. The primary outcome data from UBT consist of mixture data, which come from subjects whose H. pylori infection classifications are unconfirmed. In this paper, we propose the finite mixture distribution method to identify a reliable UBT cut‐off value in a large baseline sample in which gastric biopsy is not available to confirm the H. pylori infection in younger children. Maximum likelihood estimators of the parameters in the mixture model were obtained using an expectation maximization (EM) algorithm. The standard deviation of the cut‐off point was estimated by bootstrap methods. We applied the same analytical methods to the UBT results yielded from the follow up, as well as the overall UBT results in the longitudinal cohort data. The cut‐off points from those UBT data sets are similar. The advantage of the finite mixture model is that it may be used to calculate sensitivity and specificity in the absence of other diagnostic tests. Copyright © 2004 John Wiley & Sons, Ltd.
Estimating episode lengths when some observations are probably censored
Authors: Goodman Allen C. , Peng Yingwei , Hankin Janet R. , Kalist David E. , Spurr Stephen J.
Published: June 2004

This paper analyses a case in censored failure time data problems where some observations are potentially censored. The traditional models for failure time data implicitly assume that the censoring status for each observation is deterministic. Therefore, they cannot be applied directly to the potentially censored data. We propose an estimator that uses resampling techniques to approximate censoring probabilities for individual observations. A Monte Carlo simulation study shows that the proposed estimator properly corrects biases that would otherwise be present had it been assumed that either all potentially censored observations are censored or that no censoring has occurred. Finally, we apply the estimator to a health insurance claims database. Copyright © 2004 John Wiley & Sons, Ltd.
Concomitant‐based rank set sampling proportion estimates
Authors: Terpstra Jeff T. , Liudahl Lindsey A.
Published: June 2004

This paper discusses the rank set sampling (RSS) protocol as it pertains to the estimation of a population proportion. The ranking process is based on a concomitant variable. The concomitant‐based RSS estimate is asymptotically normal so standard inference procedures can still be implemented. This is illustrated using a real data set from the medical literature. The performance of the estimator is studied in terms of relative efficiency. Generally speaking, the concomitant‐based RSS estimator is more efficient than the proportion of successes in a simple random sample. The greatest gains in efficiency are obtained when the correlation between the Bernoulli and concomitant variable is large in absolute value. Copyright 2004 John Wiley & Sons, Ltd.
A test for informative censoring in clustered survival data
Authors: Huang Xuelin , Wolfe Robert A. , Hu Chengcheng
Published: June 2004

Frailty models are frequently used to analyse clustered survival data. The assumption of non‐informative censoring is commonly used by these models, even though it may not be true in many situations. This article proposes a test for this assumption. It uses the estimated correlation between two types of martingale residuals, one from a model for failure and the other from a model for censoring. It distinguishes two types of censoring, namely withdrawal and the end of the study. Simulation studies show that the proposed test works well under various scenarios. For illustration, the test is applied to a data set for kidney disease patients from multiple dialysis centres. Copyright © 2004 John Wiley & Sons, Ltd.
Overall C as a measure of discrimination in survival analysis: model specific population value and confidence interval estimation
Authors: Pencina Michael J. , D'Agostino Ralph B.
Published: June 2004

The assessment of the discrimination ability of a survival analysis model is a problem of considerable theoretical interest and important practical applications. This issue is, however, more complex than evaluating the performance of a linear or logistic regression. Several different measures have been proposed in the biostatistical literature. In this paper we investigate the properties of the overall C index introduced by Harrell as a natural extension of the ROC curve area to survival analysis. We develop the overall C index as a parameter describing the performance of a given model applied to the population under consideration and discuss the statistic used as its sample estimate. We discover a relationship between the overall C and the modified Kendall's τand construct a confidence interval for our measure based on the asymptotic normality of its estimate. Then we investigate via simulations the length and coverage probability of this interval. Finally, we present a real life example evaluating the performance of a Framingham Heart Study model. Copyright © 2004 John Wiley & Sons, Ltd.
Adaptive urn designs for estimating several percentiles of a dose–response curve
Authors: Mugno Raymond , Zhus Wei , Rosenberger William F.
Published: June 2004

Dose–response experiments are crucial in biomedical studies. There are usually multiple objectives in such experiments and among the goals is the estimation of several percentiles on the dose–response curve. Here we present the first non‐parametric adaptive design approach to estimate several percentiles simultaneously via generalized Pólya urns. Theoretical properties of these designs are investigated and their performance is gaged by the locally compound optimal designs. As an example, we re‐investigated a psychophysical experiment where one of the goals was to estimate the three quartiles. We show that these multiple‐objective adaptive designs are more efficient than the original single‐objective adaptive design targeting the median only. We also show that urn designs which target the optimal designs are slightly more efficient than those which target the desired percentiles directly. Guidelines are given as to when to use which type of design. Overall we are pleased with the efficiency results and hope compound adaptive designs proposed in this work or their variants may prove to be a viable non‐parametric alternative in multiple‐objective dose–response studies. Copyright © 2004 John Wiley & Sons, Ltd.
Adjusting for differential proportions of second‐line treatment in cancer clinical trials. Part I: Structural nested models and marginal structural models to test and estimate treatment arm effects
Authors: Yamaguchi Takuhiro , Ohashi Yasuo
Published: June 2004

In randomized trials, post‐randomization variables such as compliance, prescription of alternative treatments and so on are usually ignored to compare treatment arms. Intent‐to‐treat (ITT) analysis is a standard approach but it does not adjust for those variables. However, we may need to evaluate treatment arm effects that have the desired causal interpretation. Previously proposed methods such as time‐dependent Cox model may not properly adjust for post‐randomization variables and may produce biased results. Alternatively, we propose to use two causal models, structural nested models and marginal structural models. The two models appropriately adjust for such variables. We apply these models to adjust for differential proportions of post‐randomization second‐line treatment in cancer clinical trials. With sufficient care to several assumptions, these methods, especially structural nested failure time models with randomized analyses, are useful to take the influence of second‐line treatment into account and to test and estimate the direct treatment arm effect. Copyright © 2004 John Wiley & Sons, Ltd.
Adjusting for differential proportions of second‐line treatment in cancer clinical trials. Part II: An application in a clinical trial of unresectable non‐small‐cell lung cancer
Authors: Yamaguchi Takuhiro , Ohashi Yasuo
Published: June 2004

The CPT‐11 trial was conducted to confirm the superiority of CDDP+CPT‐11 (CPT‐P) arm to CDDP+VDS (VDS‐P) arm with regard to survival for patients with previously untreated advanced (stage IIIB/IV) non‐small‐cell lung cancer. However, the CPT‐P arm did not show the survival benefit for patients with stage IIIB. The proportion of patients with stage IIIB treated by active radiation given as second‐line treatment (second‐line radiotherapy) after initial (first‐line) treatment was 45 per cent in the CPT‐P arm while 61 per cent in the VDS‐P arm. This showed that not proving survival advantage in the CPT‐P arm might be due to the benefits of second‐line radiotherapy. We apply two causal models appeared in the companion paper to test and estimate the survival differences that would have been observed if all the patients had been received the same second‐line radiotherapy. Based on several assumptions, we inferred that the CPT‐P arm still would not have showed survival advantage if all the patients had been given identical second‐line radiotherapy. Copyright © 2004 John Wiley & Sons, Ltd.
JAC: an aspect‐based distributed dynamic framework
Authors: Pawlak Renaud , Seinturier Lionel , Duchien Laurence , Florin Gérard , Legond‐Aubry Fabrice , Martelli Laurent
Published: June 2004

In this paper, we present the Java Aspect Components (JAC) framework for building aspect‐oriented distributed applications in Java. This paper describes the aspect‐oriented programming model and the architectural details of the framework implementation. The framework enables extension of application semantics for handling well‐separated concerns. This is achieved with a software entity called an aspect component (AC). ACs provide distributed pointcuts, dynamic wrappers and metamodel annotations. Distributed pointcuts are a key feature of our framework. They enable the definition of crosscutting structures that do not need to be located on a single host. ACs are dynamic. They can be added, removed, and controlled at runtime. This enables our framework to be used in highly dynamic environments where adaptable software is needed. Copyright © 2004 John Wiley & Sons, Ltd.
The WTO and entry modes in China
Authors: Teng Bing‐Sheng
Published: June 2004

For years, multinational enterprises (MNEs) vying for the Chinese market used joint ventures (JVs) as an entry mode. However, there has been a growing frustration with the JV mode. It is reported that MNEs are increasingly opting for wholly owned subsidiaries for better control. This article examines the recent development of the business environment in China. It concludes that there are now real entry options for MNEs, including exporting, JVs, wholly owned subsidiaries, and acquisitions. China's accession into the World Trade Organization (WTO) will accelerate the change process and make non‐JV options even more viable. A few decision rules for choosing an entry mode in China are discussed. © 2004 Wiley Periodicals, Inc.
Learning from the implementation of the internet strategy at the Guayaquil stock exchange
Authors: Montealegre Ramiro
Published: June 2004

This article examines how an Ecuadorian stock exchange pioneered a strategy to use the Internet to educate its local market and reach investors worldwide. The findings suggest that in the initial phase of its strategy development the actions that contributed the most were benchmarking and training, learning from past experience/history, and developing a shadow organization. Actions that helped during the middle phase were providing focus, experimenting, and developing, co‐opting, and securing the resources. In the final phase, actions that contributed the most were gaining internal commitment, investing in infrastructure, and appealing to existing relationships. These findings should be useful for organizational and information technology researchers and practitioners in developed and less‐developed countries. © 2004 Wiley Periodicals, Inc.
Effect of hindered piperidine light stabilizer molecular structure and UV‐absorber addition on the oxidation of HDPE. Part 1: Long‐term thermal and photo‐oxidation studies
Authors: Liauw Christopher M. , Quadir Angela , Allen Norman S. , Edge Michele , Wagner Alan
Published: June 2004

This series of papers explores the effect of structural characteristics of 2,2,6,6‐tetramethylpiperidine‐based hindered amine light stabilizers (HALS) on the long‐term (40 months) thermal (110°C in air) and photo‐stabilization (Microscal unit wavelength >300 nm) performance characteristics of high‐density polyethylene formulations. Possible synergism with a triazine functional UV absorber is also explored. Under thermal degradation (measured by carbonyl index) the polymeric HALS performed best, mainly because of reduced volatilization. Additionally, >N‐methyl HALS generally showed superior performance under thermal degradation. There was no synergism between an N‐CH3 polymeric HALS and the UV1164 triazine additive. However, the equivalent N‐H polymeric HALS interacted in a complex manner with UV1164, giving synergism and antagonism, depending on HALS/UV1164 ratio. Strong synergism was evident with the monomeric HALS when the total stabilizer level was 0.2% w/w. Reduction in the overall stabilizer level to 0.05% w/w eliminated the synergism. The UV1164 alone led to rapid and intense yellowing; however, the rate and intensity of yellowing reduced dramatically upon combination with HALS, particularly when the UV1164 level was above 0.1% w/w. When the formulation was under UV attack, the molar mass and the type of N‐substitution had no influence on stabilization performance because of the relatively low temperature of testing (leading to reduced volatilization), and the similarly effective UV‐stabilization routes for N‐methyl HALS and N‐H HALS. Under UV attack, yellowing reached a maximum and then decreased to approximately the initial level, while HALS/UV1164 combinations generally showed weak antagonism. J. Vinyl Addit. Technol. 10:79–87, 2004. © 2004 Society of Plastics Engineers.
Normalizing effective conflict management through academic curriculum integration: The example of Workable Peace
Authors: Smith Stacie Nicole , Fairman David
Published: June 2004

An innovative program being implemented in U.S. school systems teaches youth to integrate the skills of conflict management beyond academics to their social and civic lives.
After the fall: A conflict management program to foster open society
Authors: Shapiro Daniel L.
Published: June 2004

A conflict management program developed to support the transition from a closed to open society in postcommunist eastern and central Europe focuses on the future leaders of this region: adolescents.
Youth Intervention for Peace Project: Burundi case study
Authors: Bigirindavyi Jean‐Paul
Published: June 2004

Youth in war‐ridden Burundi embrace the skills of conflict management in their process to become positive participants in their country's political process.
Challenging intolerance
Authors: Smith Alan , Maoláin Ciarán Ó
Published: June 2004

Social identity is multilayered and complex. Schools, communities, and nations can implement structures and approaches that help youth to understand one another and respect differences.
Überschreitungen der konventionellen Zahl von Clusterelektronen in Metallhalogeniden des M6X12‐Typs: W6Cl18, (Me4N)2[W6Cl18] und Cs2[W6Cl18]
Authors: Dill Simone , Glaser Jochen , Ströbele Markus , Tragl Sonja , Meyer H.‐Jürgen
Published: June 2004

Schwarze oktaedrische Einkristalle von W6Cl18 wurden bei der Reduktion von WCl4 mit Graphit in einer Kieselglasampulle bei 600 °C erhalten. Die Einkristall‐Strukturanalyse ergab (Raumgruppe R 3¯, Z = 3, a = b = 1498, 9(1) pm, c = 845, 47(5) pm) die schon früher aus Pulverdaten ermittelte Kristallstruktur von W6Cl18.

(Me4N)2[W6Cl18] und Cs2[W6Cl18] entstanden aus Lösungen von W6Cl18 und Me4NCl bzw. CsCl in Methanol. Die Struktur von (Me4N)2[W6Cl18] wurde röntgenographisch an einem Einkristall bestimmt (Raumgruppe P 3¯m1, Z = 1, a = b = 1079, 3(1) pm, c = 857, 81(7) pm). Die Struktur von Cs2[W6Cl18] wurde aus Röntgen‐Pulverdaten gelöst und verfeinert (Raumgruppe P 3¯, Z = 1, a = b = 932, 10(7) pm, c = 853, 02(6) pm).

In der Kristallstruktur von W6Cl18 sind die molekularen W6Cl18‐Einheiten wie in einer kubisch dichtesten Kugelpackung angeordnet. Die Strukturen von (Me4N)2[W6Cl18] bzw. Cs2[W6Cl18] können als Substitutionsvarianten der Kristallstruktur von W6Cl18 aufgefasst werden, in der 2/3 der W6Cl18‐Einheiten durch Me4N+‐Ionen bzw. Cs+‐Ionen ersetzt sind.

Mit 18 Elektronen in den Metall—Metall‐Zuständen von W6Cl18 und 20 Elektronen in jenen von (Me4N)2[W6Cl18] und Cs2[W6Cl18] wird die konventionelle Anzahl von 16 Elektronen/Cluster überschritten. Cs2[W6Cl18] zeigt temperaturunabhängiges paramagnetisches Verhalten.
Zintl‐Verbindungen mit Gold und Germanium: M3AuGe4 mit M = K, Rb und Cs
Authors: Zachwieja Uwe , Wlodarski Jörg
Published: June 2004

Schwarz‐glänzende, spröde Einkristalle von M3AuGe4 mit M = K, Rb, Cs wurden durch Umsetzung von Alkalimetallaziden MN3 mit Goldschwamm und Germaniumpulver bei T = 1120 K synthetisiert. Die Strukturen der Verbindungen (Raumgruppe Pmmn, Z = 2, K3AuGe4: a = 6, 655(1)Å, b = 11, 911(2)Å, c = 6, 081(1)Å; Rb3AuGe4: a = 6, 894(1)Å, b = 12, 421(1)Å, c = 6, 107(1)Å; Cs3AuGe4: a = 7, 179(1)Å, b = 12, 993(2)Å, c = 6, 112(2)Å) wurden aus Röntgen‐Einkristall‐Diffraktometerdaten bestimmt. Die elektrisch halbleitenden Verbindungen enthalten [AuGe4]‐Ketten, in denen P4‐analoge Ge4‐Tetraeder über μ2‐verbrückende Goldatome mit verzerrt tetraedrischer Koordination am Germaniumatom verknüpft werden.