bluuebunny/crossref_metadata_2025 huggingface dataset:
An Independence Test for Doubly Censored Failure Time Data
Authors: Sun Jianguo , Lim Hee‐Jeong , Zhao Xingqiu
Published: October 2004

The analysis of doubly censored failure time data has recently attracted a great deal of attention and for this, a number of methods have been proposed (De Gruttola and Lagakos, 1989; Kim et al., 1993; Pan, 2001; Sun, 2004). To simplify the analysis, most of these methods make an independence assumption: the distribution of the survival time of interest is independent of the occurrence of the initial event that defines the survival time. Although it is well‐known that the assumption may not be true, there does not seem to be any existing research discussing the checking of the assumption. In this article, a Wald test is developed for testing this assumption and the method is applied to an AIDS cohort study. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Testing for Poisson Zero Inflation in Disease Mapping
Authors: Ugarte M. Dolores , Ibáńez B. , Militino A. F.
Published: October 2004

When analyzing mortality data due to rare diseases in small areas, it is common to find several health zones with no mortality cases. In these circumstances, the classical homogeneous model based on the Poisson distribution used to estimate the relative risks within each area may encounter lack of fit due to a disproportionately large frequency of zeros. To cope with these zeros, the zero inflated Poisson model can be used. In this paper, we propose a test for detecting zero inflation in the context of disease mapping which is based on bootstrap techniques. The test is illustrated using male mortality data due to brain cancer in Navarra, Spain. In addition, comparisons with other tests for Poisson zero inflation such as the score test and the likelihood ratio test are carried out in terms of empirical power and size using the brain cancer scenario. The proposed bootstrap test has good power and size and works well when detecting the excess of zeros in small area data sets. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analytical Relationship between Family History and Genetic and Environmental risks, with Application to Female Breast Cancer
Authors: Cui Jisheng S.
Published: October 2004

It is well established in genetic epidemiology that family history is an important indicator of familial aggregation of disease in a family. A strong genetic risk factor or an environmental risk factor with high familial correlation can result in a strong family history. In this paper, family history refers to the number of first‐degree relatives affected with the disease. Cui and Hopper (Journal of Epidemiology and Biostatistics 2001; 6: 331–342) proposed an analytical relationship between family history and relevant genetic parameters. In this paper we expand the relationship to both genetic and environmental risk factors. We established a closed‐form formula for family history as a function of genetic and environmental parameters which include genetic and environmental relative risks, genotype frequency, prevalence and familial correlation of the environmental risk factor. The relationship is illustrated by an example of female breast cancer in Australia. For genetic and environmental relative risks less than 10, most of the female breast cancer cases occur between the age of 40 and 60 years. A higher genetic or environmental relative risk will move the peak of the distribution to a younger age. A more common disease allele or more prevalent environmental risk factor will move the peak to an older age. For a proband with breast cancer, it is most likely (with probability ≥80%) that none of her first‐degree relatives is affected with the disease. To enable the probability of having a positive family history to reach 50%, the environmental relative risks must be extremely as high as 100, the familial correlation as high as 0.8 and the prevalence as low as 0.1. For genetic risk alone, even the relative risk is as high as 100, the probability of having a positive family history can only reach about 30%. This suggests that the environmental risk factor seems to play a more important role in determining a strong family history than the genetic risk factor. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Valid Adjustment of Randomized Comparisons for Binary Covariates
Authors: Berger Vance W.
Published: October 2004

In randomized trials, the treatment influences not only endpoints but also other variables measured after randomization which, when used as covariates to adjust for the observed imbalance, become pseudo‐covariates. There is a logical circularity in adjusting for a pseudo‐covariate because the variability in the endpoint that is attributed not to the treatment but rather to the pseudo‐covariate may actually represent an effect of the treatment modulated by the pseudo‐covariate. This potential bias is well known, but we offer new insight into how it can lead to reversals in the direction of the apparent treatment effect by way of stage migration. We then discuss a related problem that is not generally appreciated, specifically how the absence of allocation concealment can lead to this reversal of the direction of the apparent treatment effect even when adjustment is for a true covariate measured prior to randomization. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sample Size Calculations for the Mean in a Two Component Nonstandard Mixture Distribution
Authors: Chu Haitao , Ren Shiquan , Cole Stephen R.
Published: October 2004

We are concerned with calculating the sample size required for estimating the mean of the continuous distribution in the context of a two component nonstandard mixture distribution (i.e., a mixture of an identifiable point degenerate function F at a constant with probability P and a continuous distribution G with probability 1 – P). A common ad hoc procedure of escalating the naïve sample size n (calculated under the assumption of no point degenerate function F) by a factor of 1/(1 – P), has about 0.5 probability of achieving the pre‐specified statistical power. Such an ad hoc approach may seriously underestimate the necessary sample size and jeopardize inferences in scientific investigations. We argue that sample size calculations in this context should have a pre‐specified probability of power ≥1 – β set by the researcher at a level greater than 0.5. To that end, we propose an exact method and an approximate method to calculate sample size in this context so that the pre‐specified probability of achieving a desired statistical power is determined by the researcher. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Robust Tests for Candidate‐Gene Association Using Case‐Parents Trios with a Multi‐Allelic Marker
Authors: Zheng Gang , Chen Zehua
Published: October 2004

In case‐parents trios design, the association between a multi‐allelic candidate‐gene and a disease can be detected by using maximum of score tests (max‐score) when the mode of inheritance is known. We apply the maximum of the max‐score statistics and the maximum of likelihood ratio statistics when the genetic model is unknown and examine their robust properties compared to max‐score statistics. The simulation results demonstrate that the two maximum robust tests are more efficacious and robust across all genetic models compared with the three max‐score tests. Moreover, in most situations, the maximum of the max‐score tests seems to be more powerful than the maximum of the likelihood ratio tests. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Using Adaptive Methods to Select Variables in Case‐Control Studies
Authors: O'Gorman Thomas W.
Published: October 2004

A variables selection method for case‐control studies is proposed that uses an adaptive weighting scheme along with a permutation method to determine if a variable is useful in differentiating the cases from the controls. This adaptive method is used to select exposure variables for the analysis of data from a bladder cancer case‐control study. An extensive simulation study shows that the adaptive method is nearly as effective at finding those variables that are related to case‐control status when normally distributed variables are used. The simulation also shows that the proposed variable selection procedure is much more effective than the stepwise discriminant analysis method when the variables are not normally distributed. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bayesian Predictive Probability Functions for Count Data that are Subject to Misclassification
Authors: Stamey James D. , Young Dean M. , Bratcher Tom L.
Published: October 2004

We develop three Bayesian predictive probability functions based on data in the form of a double sample. One Bayesian predictive probability function is for predicting the true unobservable count of interest in a future sample for a Poisson model with data subject to misclassification and two Bayesian predictive probability functions for predicting the number of misclassified counts in a current observable fallible count for an event of interest. We formulate a Gibbs sampler to calculate prediction intervals for these three unobservable random variables and apply our new predictive models to calculate prediction intervals for a real‐data example. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Aromatic interactions in peptides: Impact on structure and function
Authors: Waters Marcey L.
Published: October 2004

Aromatic interactions, including π–π, cation–π, aryl–sulfur, and carbohydrate–π interactions, have been shown to be prevalent in proteins through protein structure analysis, suggesting that they are important contributors to protein structure. However, the magnitude and significance of aromatic interactions is not defined by such studies. Investigation of aromatic interactions in the context of structured peptides has complemented studies of protein structure and has provided a wealth of information regarding the role of aromatic interactions in protein structure and function. Recent advances in this area are reviewed. © 2004 Wiley Periodicals, Inc. Biopolymers (Pept Sci), 2004
Cyclization of pyrrhocoricin retains structural elements crucial for the antimicrobial activity of the native peptide
Authors: Rosengren K. Johan , Göransson Ulf , Otvos Laszlo , Craik David J.
Published: October 2004

Pyrrhocoricin is a naturally occurring antimicrobial peptide from the European fire bug Pyrrhocoris apterus. It has submicromolar activity against a range of Gram‐negative bacterial strains and has created recent interest as a lead for the development of novel antibiotic compounds. In this study, we have used NMR spectroscopy to determine the solution structures of pyrrhocoricin and a synthetic macrocyclic derivative that has improved in vivo pharmaceutical properties. Native pyrrhocoricin is largely disordered in solution, but there is evidence of a subpopulation with ordered turn regions over residues 2–5, 4–7, and 16–19. The macrocyclic derivative incorporates a nine amino acid linker joining the N‐ and C‐termini, which does not adversely affect the antimicrobial potency but leads to a broader spectrum of activity. The NMR data suggest that the turn conformations in the cyclic derivative are similar to those in the native form, thus implicating them in the biological function. © 2004 Wiley Periodicals, Inc. Biopolymers (Pept Sci), 2004
Enantioselective Catalysis of the Hetero‐Diels–Alder Reaction between Brassard's Diene and Aldehydes by Hydrogen‐Bonding Activation: A One‐Step Synthesis of (S)‐(+)‐Dihydrokawain
Authors: Du Haifeng , Zhao Dongbo , Ding Kuiling
Published: October 2004

The first catalytic enantioselective hetero‐Diels–Alder reaction between Brassard's diene and aldehydes has been achieved through hydrogen‐bonding activation using TADDOL derivatives as catalysts to afford the corresponding δ‐lactone derivatives in moderate‐to‐good yields and with high enantioselectivities (up to 91 % ee). The reactions can be carried out either under solvent‐free conditions or in toluene. On the basis of the absolute configurations of the products and the hydrogen‐bonding interaction pattern between TADDOL (α,α,α′,α′‐tetraaryl‐1,3‐dioxolan‐4,5‐dimethanol) and the carbonyl group disclosed by X‐ray diffraction analysis, a possible mechanism for the catalytic reaction has been proposed. To demonstrate the usefulness of the methodology, a natural product, (S)‐(+)‐dihydrokawain, has also been prepared in 50 % isolated yield and with 69 % enantioselectivity in one step starting from 3‐phenylpropionaldehyde by using this methodology. Therefore, this catalytic system is one of the most direct approaches to the construction of δ‐lactone units, which will make the methodology very attractive for the synthesis of a variety of biologically important compounds and natural products.
Novel Hypervalent Complexes of Main‐Group Metals by Intramolecular Ligand→Metal Electron Transfer*
Authors: Driess Matthias , Dona Nicoleta , Merz Klaus
Published: October 2004

New fascinating electronic features of the simple diketoamine chelate ligand HN[CH2C(tBu)O]2 (1) are described. Unexpectedly, the corresponding trianionic amido‐dienolate form of 1 is capable of reducing main‐group metal atoms M after initial coordination and intramolecular L→M two‐electron transfer and of stabilizing main‐group elements in unusual low oxidation states. This is impressively shown by the synthesis and structural characterization of the novel Ge and Sn complexes 4–6 by redox reactions of lithiated 1 with the corresponding metal halides GeCl4 and MCl2 (M=Ge, Sn). Surprisingly, conversion of tris‐lithiated 1 with GeCl4 readily consumes two molar equivalents of GeCl4 and results in the formation of the neutral GeCl3 complex 4 and GeCl2. The former represents the second example of a structurally characterized neutral octahedrally coordinated germanium compound. Reaction of dilithiated 1 with GeCl2 does not lead to the expected ClGe(+2) complex but affords the novel dimeric germylene 5, whereas similar reaction using SnCl2 furnishes the monomeric stannylene (ClSn(+2) complex) 2 and elemental tin due to the higher oxidation potential of Sn(+2). Unexpectedly, a similar redox reaction of dilithiated 1 with PbCl2 furnishes the first air‐ and water‐stable lithium 1,2‐diketoimine–enolate 7 and elemental lead. Compound 7 is tetrameric in the solid state and consists of a strongly distorted Li4O4 cubic core with trigonal‐bipyramidal coordinated Li+ ions.
A multicenter study of supportive‐expressive group therapy for women with BRCA1/BRCA2 mutations
Authors: Esplen Mary Jane , Hunter Jon , Leszcz Molyn , Warner Ellen , Narod Steven , Metcalfe Kelly , Glendon Gord , Butler Kate , Liede Alexander , Young Mary Anne , Kieffer Stephanie , DiProspero Lisa , Irwin Ellen , Wong Jiahui
Published: October 2004

BACKGROUND

Women with a BRCA1/BRCA2 mutation experience significant challenges. These include decision‐making regarding surgical options and notification to offspring and family, along with a sense of isolation, which may lead to psychological and emotional distress. The current study developed, standardized, and conducted preliminary testing of a supportive‐expressive group therapy intervention designed to address these challenges.

METHODS

Seventy women with a BRCA1/BRCA2 mutation recruited from familial cancer risk clinics participated in 12 sessions of supportive‐expressive group therapy that lasted 6 months. Before and after measures of psychosocial functioning, knowledge, and surveillance/surgery activities were completed.

RESULTS

Sixty‐seven women completed the intervention. Significant improvements were observed in psychosocial functioning: cancer worries (P = 0.005), anxiety (P = 0.033), and depression (P = 0.015). Knowledge level and surveillance levels were high at baseline and there were no significant changes postintervention. A significant number of women made decisions concerning prophylactic surgery (oophorectomy/mastectomy) during and after the intervention.

CONCLUSIONS

The feasibility of a supportive‐expressive group for BRCA1/BRCA2 mutation carriers was demonstrated. Findings from the study are consistent with an effective intervention. However, further research is required using a randomized controlled study design. Cancer 2004. © 2004 American Cancer Society.
Are chroma tolerances dependent on hue‐angle?
Authors: Melgosa M. , Huertas R. , Yebra A. , Pérez M. M.
Published: October 2004

Relationships between suprathreshold chroma tolerances and CIELAB hue‐angles have been analyzed through the results of a new pair‐comparison experiment and the experimental combined data set employed by CIE TC 1–47 for the development of the latest CIE color‐difference formula, CIEDE2000. Chroma tolerances have been measured by 12 normal observers at 21 CRT‐generated color centers L*10 = 40, C*ab,10 = 20 and 40, and hab,10 at 30° regular steps). The results of this experiment lead to a chroma‐difference weighting function with hue‐angle dependence WCH, which is in good agreement with the one proposed by the LCD color‐difference formula [Color Res Appl 2001;26:369–375]. This WCH function is also consistent with the experimental results provided by the combined data set employed by CIE TC 1–47. For the whole CIE TC 1–47 data set, as well as for each one of its four independent subsets, the PF/3 performance factor [Color Res Appl 1999;24:331–343] was improved by adding to CIEDE2000 the WCH function proposed by LCD, or the one derived by us using the results of our current experiment together with the combined data set employed by CIE TC 1–47. Nevertheless, unfortunately, from the current data, this PF/3 improvement is small (and statistically nonsignificant): 0.3 for the 3657 pairs provided by CIE TC 1–47 combined data set and 1.6 for a subset of 590 chromatic pairs (C*ab,10>5.0) with color differences lower than 5.0 CIELAB units and due mainly to chroma. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 420–427, 2004; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/col.20057
Predicting changes in the color of powders: Does Melamed's model fit to real industrial powders?
Authors: Garay Hélène , Eterradossi Olivier , Benhassaine Ali
Published: October 2004

In 1963, Melamed proposed a model that expressed reflectance of a powder described as a population of spherical particles of unique diameter as a function of size, shape, and optical characteristics of the powder. This article shows how this model has been adapted to fit to industrial powders. An example of use for industrial quartz is given. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 413–419, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20058
Visually matching daylight fluorescent lamplight with two primary sets
Authors: Houser Kevin W. , Hu Xin
Published: October 2004

Thornton reported discrepancies in chromaticity and power content in Maxwell‐method visual matches when using different primary sets. He found particularly large chromaticity differences when a broadband white light was matched with what he refers to as an antiprime (AP) primary set [blue‐green, yellow, deep red, as, for example 497–579‐653 nm, mean full‐width half‐maximum (FWHM) = 15.6 nm] and comparatively smaller chromaticity differences with a prime‐color (PC) primary set (blue‐violet, green, orange‐red, as, for example, 452–533‐607 nm, mean FWHM = 15.6 nm). In related work, Ábrahámet al.found similar chromaticity discrepancies when subjects reported a visual match, partially attributing the errors to age‐related changes in the specular transmittance of the lens. This present study was carried out to explore these findings and to investigate individual differences in color matching. Thirty‐nine subjects made two matches in a horizontally bisected 10° field. The bottom field was illuminated with daylight fluorescent lamplight and the top field was illuminated with one of two primary sets that were selected to be similar to those used by Thornton and Ábrahámet al.: (1) PC = 453–533‐619 nm with a mean FWHM of 18.3 nm and (2) AP = 493–581‐657 nm with a mean FWHM of 23.7 nm. Statistical data screening revealed two outliers that were removed from further analysis. The PC primary set required 5% less radiant power per unit area to match the daylight fluorescent reference and the AP set required 117% more. Thirty‐six of the 37 matches with the PC primary set were within a 10‐step MacAdam ellipse that was centered at the daylight fluorescent reference. In contrast, just 2 of the matches with the AP set were within a 10‐step ellipse, and 24 of the matches were outside of a 20‐step ellipse. These trends are similar to those reported by Thornton and later by Ábrahámet al.The primary set and the interaction between primary set and age were statistically significant factors. Gender and subject knowledge were not significant. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 428–437, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20059
Accurate estimation of the nonlinearity of input/output response for color cameras
Authors: Cheung Vien , Westland Stephen , Thomson Mitch
Published: October 2004

This study investigates techniques for accounting for the nonlinearity of the input/output response of a camera system. A simple power‐law form of the nonlinearity was assumed and estimates of the value for the exponent for each of the color channels were made using three different methods. The responses from an Agfa StudioCam camera were linearized and then device characterization was attempted. Characterization errors were up to 10% better using the spectral‐sensitivities‐based method for estimating the nature of the nonlinearity than using the other two methods. We therefore suggest that the spectral‐sensitivities‐based method should be preferred for characterization or any other computational process that requires linearization of the camera responses. We expect greater benefits using this method for “low‐end” camera systems and/or for cameras where the spectral sensitivities are known or more precisely estimated. We also expect the smoothness of the illumination to influence the error in the estimates of the nonlinearity using the luminance‐ and mean‐reflectance‐based methods. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 406–412, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20061
Cross‐regional comparison of colour emotions Part I: Quantitative analysis
Authors: Xin J. H. , Cheng K. M. , Taylor G. , Sato T. , Hansuebsai A.
Published: October 2004

Colour emotion is a feeling or emotion induced in our brains when we look at a colour. In this article, the colour emotional responses obtained by conducting visual experiments in different regions, namely Hong Kong, Japan and Thailand, using a set of 218 colour samples are compared using a quantitative approach in an attempt to study the influence of different cultural and geographical locations. Twelve pairs of colour emotions described in opponent words were used. These word pairs are warm–cool, light–dark, deep–pale, heavy–light, vivid–sombre, gaudy–plain, striking–subdued, dynamic–passive, distinct–vague, transparent–turbid, soft–hard, and strong–weak. These word pairs represent the fundamental emotional response of human beings toward colour. The influences of lightness and chroma were found to be much more important than that of the hue on the colour emotions studied. Good correlations of colour emotions among these three regions in East Asia were found, with the best ones for colour emotion pairs being light–dark and heavy–light. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 451–457, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20062
Cross‐regional comparison of colour emotions Part II: Qualitative analysis
Authors: Xin J. H. , Cheng K. M. , Taylor G. , Sato T. , Hansuebsai A.
Published: October 2004

During the colour perception process, an associated feeling or emotion is induced in our brains, and this kind of emotion is known as colour emotion. In Part I of this study, a quantitative analysis of the cross‐regional differences and similarities of colour emotions as well as the influence of hue, lightness, and chroma on the colour emotions of the subjects from Hong Kong, Japan, and Thailand, was carried out. In Part II, colour emotions of the subjects in any two regions were compared directly using colour planners showing the effect of the lightness and the chroma of colours. The colour planners can help the designers to understand the taste and feelings of the target customers and facilitate them to select suitable colours for the products that are intended to be supplied in different regions. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 458–466, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20063
The properties of multiple CMF determinations using alternative primary sets Part II: A data unification methodology
Authors: Oulton D. P.
Published: October 2004

The spectral power values representing Thornton's “alternative primary” PC, NP, and AP colour matching functions (CMF) are compared with the power values representing the 49‐observer Stiles–Burch average definition. The Thornton measurements are first converted by matrix transformation into a data set expressed in terms of spectral power at the Stiles–Burch primary wavelengths. Graphs and power ratios are used to compare the definitions for two alternative matches to the same visual stimulus. A triplet of n:n spectral‐power ratios (one in each dimension, R, G, and B) is used to quantify the differences between the alternative matches. The relationship between the Thornton PC and Stiles–Burch match‐definitions is then found to deviate from the expected power‐ratio of 1:1 after matrix transformation. The revealed relationship is an internally consistent and smooth function of matched wavelength, which has a different nonlinear characteristic in each R, G, and B dimension relative to the Stiles–Burch reference model. The “Thornton bow‐tie” phenomenon is also demonstrated between a pair of maximum saturation CMF definitions made with alternative primaries. The implicit differences in neutral axis definition represented by the bow‐tie diagram are linked to differences in trichromatic unit (T‐unit) definition. In this case, the conventional CMF normalization process is postulated to be inaccurate at the wavelengths concerned, resulting in incompatibility between the T‐unit definitions of the two primary sets being compared. The conventional N→3 T‐unit definition of visual neutrality equating Illuminant SE to a single R:G:B power ratio is extended, by adding an extra N→N mapping to the definition. The resulting N→N→3 mapping is in principle a fully determined redefinition of three‐dimensional T‐unit equivalence, in which many R:G:B ratios for a comprehensive set of visually neutral metamers can be mapped by N→N transformation onto the conventional single ratio. The effect of N→N mapping is to transform spectral power distributions (SPDs) into spectral effect distributions (SEDs) expressed in T‐units. The SPD/SED transform, thus defined, is proposed as a method for unifying CMF determinations made with alternative primaries. The expected outcome is that after transforming SPDs by N→N mapping into SEDs the definitions for all visually matching metamers will be demonstrably interconvertible by matrix product. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 438–450, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20069
A performance study of job management systems
Authors: El‐Ghazawi Tarek , Gaj Kris , Alexandridis Nikitas , Vroman Frederic , Nguyen Nguyen , Radzikowski Jacek R. , Samipagdi Preeyapong , Suboh Suboh A.
Published: October 2004

Job Management Systems (JMSs) efficiently schedule and monitor jobs in parallel and distributed computing environments. Therefore, they are critical for improving the utilization of expensive resources in high‐performance computing systems and centers, and an important component of Grid software infrastructure. With many JMSs available commercially and in the public domain, it is difficult to choose an optimum JMS for a given computing environment. In this paper, we present the results of the first empirical study of JMSs reported in the literature. Four commonly used systems, LSF, PBS Pro, Sun Grid Engine/CODINE, and Condor were considered. The study has revealed important strengths and weaknesses of these JMSs under different operational conditions. For example, LSF was shown to exhibit excellent throughput for a wide range of job types and submission rates. Alternatively, CODINE appeared to outperform other systems in terms of the average turn‐around time for small jobs, and PBS appeared to excel in terms of turn‐around time for relatively larger jobs. Copyright © 2004 John Wiley & Sons, Ltd.
Supporting Bulk Synchronous Parallelism with a high‐bandwidth optical interconnect
Authors: Gourlay I. , Dew P. M. , Djemame K. , Snowdon J. F. , Russell G.
Published: October 2004

The list of applications requiring high‐performance computing resources is constantly growing. The cost of inter‐processor communication is critical in determining the performance of massively parallel computing systems for many of these applications. This paper considers the feasibility of a commodity processor‐based system which uses a free‐space optical interconnect. A novel architecture, based on this technology, is presented. Analytical and simulation results based on an implementation of BSP (Bulk Synchronous Parallelism) are presented, indicating that a significant performance enhancement, over architectures using conventional interconnect technology, is possible. Copyright © 2004 John Wiley & Sons, Ltd.
Towards a more realistic comparative analysis of multicomputer networks
Authors: Sarbazi‐Azad H. , Ould‐Khaoua M. , Mackenzie L. M.
Published: October 2004

Several studies have examined the relative performance merits of the torus and hypercube taking into account the channel bandwidth constraints imposed by implementation technology. While the torus has been shown to outperform the hypercube under the constant wiring density constraint, the opposite conclusion has been reached when the constant pin‐out constraint is considered. However, these studies have assumed a pure uniform traffic pattern and deterministic routing. The ‘uniform traffic’ assumption is not always justifiable in practice as there are many real‐world parallel applications that exhibit non‐uniform traffic patterns, which can create unbalanced traffic such as hotspots in the network. This paper re‐examines the performance merits of the torus and hypercube in the presence of hotspot traffic. The comparative analysis is based on fully adaptive routing as this has been gaining popularity in recent practical multicomputers. Moreover, it uses a new cost model that takes into account the implementation cost of the network and its routers. The results reveal that for moderate and large system sizes, lower dimensionalk‐aryn‐cubes (e.g. 2D torus) always outperform their higher dimensional counterparts even under the pin‐out constraint. Copyright © 2004 John Wiley & Sons, Ltd.
RF‐MVTC: an efficient risk‐free multiversion concurrency control algorithm
Authors: Boukerche Azzedine , Tuck Terry
Published: October 2004

In this paper, we focus on the temporary return of data values that are incorrect for given transactional semantics that could have catastrophic effects similar to those in parallel and discrete event simulation systems. In many applications using online transactions processing environments, for instance, it is best to delay the response to a transaction's read request until it is either known or unlikely that a write message from an older update transaction will not make the response incorrect. Examples of such applications are those where aberrant behavior is too costly, and those in which precommitted data is visible to some reactive entity. In light of the avoidance of risk in this approach, we propose a risk‐free multiversion temporally correct concurrency‐control algorithm. We discuss the algorithm, its implementation and report on the performance results of simulation models using a cluster of workstations. Copyright © 2004 John Wiley & Sons, Ltd.
On the performance of circuit‐switched networks in the presence of correlated traffic
Authors: Min Geyong , Ould‐Khaoua Mohamed
Published: October 2004

Many studies have revealed that the traffic generated by multimedia applications exhibits a high degree of burstiness and possesses strong correlation in the number of message arrivals between adjacent time intervals, which can significantly affect network performance. This paper proposes a new analytical performance model for circuit‐switched k‐ary n‐cubes with correlated traffic pattern. Compared to the models presented in the previous studies, this model is more realistic due to its ability to capture the effects of using virtual channels at a source node by taking into account the splitting of correlated traffic. Moreover, a closed‐form expression for computing the probability of virtual channel occupancy is given. The validity of the present model is demonstrated by comparing analytical results against those obtained through simulation experiments of the actual system. Copyright © 2004 John Wiley & Sons, Ltd.
Performance evaluation of a random‐walk‐based algorithm for embedding dynamically evolving trees in hypercubic networks
Authors: Li Keqin
Published: October 2004

In many tree‐structured parallel computations, the size and structure of a tree that represents a parallel computation is unpredictable at compile‐time; the tree evolves gradually during the course of the computation. When such a computation is performed on a static network, the dynamic tree embedding problem is to distribute the tree nodes to the processors of the network such that all the processors receive roughly the same amount of load and that communicating nodes are assigned to neighboring processors. Furthermore, when a new tree node is generated, it should be immediately assigned to a processor for execution without any information on the further evolving of the tree; and load distribution is performed by all processors in a totally distributed fashion.

We study the problem of embedding dynamically evolving trees in hypercubic networks, including shuffle‐exchange, de Bruijn, cube‐connected cycles, wrapped butterfly, and hypercube networks. The performance of a random‐walk‐based randomized tree embedding algorithm is evaluated. Several random tree models are considered. We develop recurrence relations for analyzing the performance of embedding of complete‐tree‐based random trees and randomized complete trees, and linear systems of equations for reproduction trees. We present more efficient recurrence relations and linear systems of equations for symmetric networks. We also demonstrate extensive numerical data of the performance ratio and make a number of interesting observations of randomized tree embedding in the five hypercubic networks. Copyright © 2004 John Wiley & Sons, Ltd.
On the scalability of many‐to‐many reliable multicast sessions
Authors: Yoon W. Y. , Lee D. , Youn H. Y.
Published: October 2004

Even though tree‐based reliable multicast protocols are known to be most scalable for one‐to‐many sessions, there is still an open question as to whether these protocols are also scalable for many‐to‐many sessions. In this paper, we analyze and compare two promising multicast protocols—the receiver‐initiated protocol with NACK suppression and the tree‐based protocol—using a new spatial loss model. The proposed model considers the correlation of packet loss events for more realistic analysis unlike the previous work. The analysis results show that the tree‐based protocol achieves much higher throughput than the receiver‐initiated protocol for a many‐to‐many session as the number of participants in the session becomes larger. Copyright © 2004 John Wiley & Sons, Ltd.
One‐to‐all broadcasting scheme for arbitrary static interconnection networks with bursty background traffic
Authors: Kouvatsos D. D. , Mkwawa I. M. , Awan I.
Published: October 2004

A novel one‐to‐all broadcasting scheme is proposed for arbitrary static interconnection networks with bursty background traffic having head‐of‐line priorities, complete buffer sharing and repetitive service blocking with random destination. The scheme facilitates inter‐process communication amongst parallel computers and grid computing networks as well as asynchronous transfer mode space division architectures and it is applicable to a single‐port mode of message passing communication. The scheme utilizes a queue‐by‐queue decomposition algorithm for arbitrary open queueing network models, based on the principle of maximum entropy, in conjunction with an information theoretic decomposition criterion and graph theoretic concepts. Evidence based on empirical studies indicates the suitability of the scheme for achieving an optimal one‐to‐all broadcasting cost. Copyright © 2004 John Wiley & Sons, Ltd.
Molecule‐to‐Metal Bonds: Electrografting Polymers on Conducting Surfaces
Authors: Palacin Serge , Bureau Christophe , Charlier Julienne , Deniau Guy , Mouanda Brigitte , Viel Pascal
Published: October 2004

Electrografting is a powerful and versatile technique for modifying and decorating conducting surfaces with organic matter. Mainly based on the electro‐induced polymerization of dissolved electro‐active monomers on metallic or semiconducting surfaces, it finds applications in various fields including biocompatibility, protection against corrosion, lubrication, soldering, functionalization, adhesion, and template chemistry. Starting from experimental observations, this Review highlights the mechanism of the formation of covalent metal–carbon bonds by electro‐induced processes, together with major applications such as derivatization of conducting surfaces with biomolecules that can be used in biosensing, lubrication of low‐level electrical contacts, reversible trapping of ionic waste on reactive electrografted surfaces as an alternative to ion‐exchange resins, and localized modification of conducting surfaces, a one‐step process providing submicrometer grafted areas and which is used in microelectronics.
Determination of the Heterogeneous Association Constants of Metal Ions to ω‐Mercaptoalkanoic Acids by Using Double‐Layer Capacity Measurements
Authors: Burshtain Doron , Mandler Daniel
Published: October 2004

The binding of metal ions to ligands in homogeneous solutions and that to the same ligands anchored to metallic surfaces through self‐assembled monolayers (SAMs) are expected to differ primarily due to the difference in the degree of freedom of the ligands and the surface potential. We studied the heterogeneous binding of CdII ions to ω‐mercaptoalkanoic‐acid SAMs on Au. This was accomplished by adding metal ions at a constant pH and following the changes in the double‐layer capacity. A mathematical treatment, which is based on calculating the electrochemical‐potential differences at the double layer–solution interface, has been developed. Our approach follows that proposed by White et al.1, 2 and Kakiuchi,3 who used the acid–base equilibrium at the monolayer–electrolyte interface as a means of calculating the pK of ionizable SAMs. Experimentally, SAMs of ω‐mercaptoalkanoic acids, HS(CH2)nCO2H, with different chain lengths (i.e., n=2, 5, and 10) in 0.1 M sodium perchlorate were assembled on Au surfaces and studied. The capacity was measured first in the absence of CdII at different pH values, and then at a constant pH while increasing the concentration of CdII in the solution. We found that the interfacial capacity decreased as the concentration (of either protons or CdII) increased. The results matched the model fairly well, which allowed the extraction of the thermodynamic equilibrium constant that is established at the monolayer–electrolyte interface. The suggested mathematical treatment of this model system is simple and yet very useful for estimating the heterogeneous association constants of metal ions by SAMs.
Gaseous Ion Activation Dynamics: The Role of the Bulk Gas in the Racemization of Chiral Oxonium Ions
Authors: Filippi Antonello , Speranza Maurizio
Published: October 2004

The kinetics of the inversion of configuration of a family of chiral oxonium ions, that is, O‐protonated 1‐aryl‐1‐methoxyethanes [YMe+], were investigated in two different gaseous media (in CH3X with X=F and X=Cl) at 720 torr of pressure and in the temperature range: 25–140 °C. The activation parameters of the [YMe+] inversion reaction were found to obey two different isokinetic relationships (IKR), depending on the nature and the position of the substituents in the oxonium ions and on the nature of the bulk gas employed. The observation of two IKR for the same family of reactions was related to a switchover in the resonant vibrational energy exchange between the reactants' critical mode, active in the transition state (ω), and the discrete vibrational levels ν of the bulk gas. In CH3F, this vibrational–vibrational coupling switchover concerns the out‐of‐plane CF⋅⋅⋅HO bending (the Φ family) and the H3CF stretching (the Γ family) modes in the proton‐bound [CH3F⋅YMe+] complex. In CH3Cl, the coupling switchover concerns the out‐of‐plane CCl⋅⋅⋅HO bending (the Φ family) and the H3CCl methyl group rocking (the Γ family) modes in the proton‐bound [CH3Cl⋅YMe+] complex. The [YMe+] activation dynamics also determine the inversion dynamics. The [YMe+]ret⇄[YMe+]inv isomerization for the Φ family involves the same “thermodynamically most favorable” transition state in both the CH3F and the CH3Cl media, whereas the same process for the Γ family proceeds through different, dynamically favored transition states.
Zinc oxide – analogue of GaN with new perspective possibilities
Authors: Karpina V. A. , Lazorenko V. I. , Lashkarev C. V. , Dobrowolski V. D. , Kopylova L. I. , Baturin V. A. , Pustovoytov S. A. , Karpenko A. Ju. , Eremin S. A. , Lytvyn P. M. , Ovsyannikov V. P. , Mazurenko E. A.
Published: October 2004

Zinc oxide due to specific electrical, optical and acoustic properties is the important semiconductor material, which has many various applications. There is growing interest in ZnO due to its potential applicability for optoelectronic devices such as light‐emitting diodes, laser diodes and detectors for UV wavelength range. ZnO properties are very close to those of widely recognized semiconductor GaN. The band gap of ZnO (3.37 eV) is close to that of GaN (3.39 eV) but ZnO exciton binding energy (60 meV) is twice larger than that of GaN (28 meV). Optically pumped UV lasing have been demonstrated at room temperature using high textured ZnO films. The excitonic gain close to 300 cm–1 was achieved. ZnO thin films are expected to have higher quantum efficiency in UV semiconductor laser than GaN. The physical properties of ZnO are considered. PEMOCVD technology was used to deposit piezoelectric and highly transparent electroconductive ZnO films. Their properties are discussed. The experiments on polycrystalline ZnO films deposited by RF magnetron sputtering at different partial pressure of oxygen are presented. AFM images were studied in tapping mode for deposited films. The investigated films were dielectric ones and had optical transparency within 65‐85% at thickness in the interval 0.2‐0.6 μm. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lattice dynamics and related properties of AIBIII and AIIBIV compounds, I. Elastic constants
Authors: Neumann H.
Published: October 2004

The present state of knowledge of the elastic properties of the ternary chalcopyrite compounds and some related materials is reviewed. Results of experimental elastic constant determinations are critically evaluated by comparing with other experimentally available material parameters that directly depend on the elastic constants. Possible reasons for existing discrepancies and obvious inconsistencies in the experimental data are discussed. The results of theoretical calculations of the elastic constants of these compounds based on different theoretical models and approaches are compared with experimental data and are assessed concerning achievable accuracy and reliability. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystallographic nets and their quotient graphs
Authors: Klee W. E.
Published: October 2004

Crystallographic nets are defined. It is shown how these nets can be generated from finite graphs which are called the quotient graphs of the nets. The procedure yields the topology of the nets, their crystallographic point groups and their lattice types. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Diffusion induced segregation in the case of the ternary system sphalerite, chalcopyrite and cubanite
Authors: Blesgen T. , Luckhaus S. , Bente K.
Published: October 2004

A mathematical model for describing natural and experimental diffusion induced segregation (DIS) in the case of a (Zn,Fe)S single crystal with three coexisting phases is derived. As main result, a new and quite general segregation principle for ternary systems is discovered where one phase has a flat free energy density and serves as catalyst for the segregation of the other two phases. The model includes also a stochastic noise term to represent fluctuations of the copper concentration. Numerical simulations in 2‐d underline the physical significance of the model and allow to make quantitative predictions. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth kinetics of ammonium oxalate monohydrate single crystals from aqueous solutions containing Co(II) and Ni(II) impurities
Authors: Mielniczek‐Brzóska E. , Sangwal K.
Published: October 2004

The growth kinetics of different faces of ammonium oxalate monohydrate (AO) single crystals from aqueous solutions containing different concentrations of Co(II) and Ni(II) ions at a constant temperature are described and discussed. It was found that: (1) at a given supersaturation σ, both Co(II) and Ni(II) ions lead to a decrease in the growth rates R of different faces of AO crystals, (2) the growth of a particular face of the crystals occurs above a critical supersaturation σd, but there is also another supersaturation barrier σ* when the rate abruptly increases with σ, and (3) the values of σd and σ* increase with increasing concentration ci of the impurity. The experimental R(σ) data for different concentrations ci of the impurities were analysed according to the model involving complex source of cooperating screw dislocations and concepts of instantaneous and time‐dependent impurity adsorption. Analysis of the data showed that: (1) adsorption of Co(II) and Ni(II) impurities occurs on the surface terrace of AO crystals, (2) there is a simple relationship between Langmuir constant K and the impurity concentration ci* corresponding to maximum surface coverage, and (3) the ratio σd/σ* of the supersaturation barriers observed in the presence of both impurities increases with an increase in impurity concentration ci, and may be explained from the standpoint of the mechanism of adsorption of impurity particles at kinks and ledges. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synergy of organic dyes for KDP crystal growth
Authors: Maeda Kouji , Sonoda Akira , Miki Hideo , Asakuma Yusuke , Fukui Keisuke
Published: October 2004

Single potassium dihydrogen phosphate (KDP) crystals were grown in a supersaturated solution containing an organic dye (sunset yellow FCF, brilliant blue FCF, and sky blue). The growth rate, morphology, and impurity dye distribution of faces, (100) and (101) in a KDP crystal were measured as dye concentration and the supersatutation of KDP were changed. Complete expressions for the effect of dye on all aspects of the growth of KDP crystals were discussed. The growth rates of (100) and (101) faces were well correlated by the empirical equation, and resulted in good estimation of the morphology. The distribution of dye in a KDP crystal was represented by the distribution model containing the minimum growth rate for coloring. The growth rate equation and distribution equation were expressed by functions of the supersaturation and dye concentration, and they could effectively provide the operational conditions with coloring the KDP crystal. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)