bluuebunny/crossref_metadata_2025 huggingface dataset:
An enhanced branch‐and‐bound algorithm for a partitioning problem
Authors: Brusco Michael J.
Published: May 2003

This paper focuses on the problem of developing a partition of n objects based on the information in a symmetric, non‐negative dissimilarity matrix. The goal is to partition the objects into a set of non‐overlapping subsets with the objective of minimizing the sum of the within‐subset dissimilarities. Optimal solutions to this problem can be obtained using dynamic programming, branch‐and‐bound and other mathematical programming methods. An improved branch‐and‐bound algorithm is shown to be particularly efficient. The improvements include better upper bounds that are obtained via a fast exchange algorithm and, more importantly, sharper lower bounds obtained through sequential solution of submatrices. A modified version of the branch‐and‐bound algorithm for minimizing the diameter of a partition is also presented. Computational results for both synthetic and empirical dissimilarity matrices reveal the effectiveness of the branch‐and‐bound methodology.
Bootstrap approach to inference and power analysis based on three test statistics for covariance structure models
Authors: Yuan Ke‐Hai , Hayashi Kentaro
Published: May 2003

We study several aspects of bootstrap inference for covariance structure models based on three test statistics, including Type I error, power and sample‐size determination. Specifically, we discuss conditions for a test statistic to achieve a more accurate level of Type I error, both in theory and in practice. Details on power analysis and sample‐size determination are given. For data sets with heavy tails, we propose applying a bootstrap methodology to a transformed sample by a downweighting procedure. One of the key conditions for safe bootstrap inference is generally satisfied by the transformed sample but may not be satisfied by the original sample with heavy tails. Several data sets illustrate that, by combining downweighting and bootstrapping, a researcher may find a nearly optimal procedure for evaluating various aspects of covariance structure models. A rule for handling non‐convergence problems in bootstrap replications is proposed.
An asymptotic partial correlation test for the Goodman‐Kruskal λ
Authors: Suich Ronald C. , Turek Richard J.
Published: May 2003

Goodman and Kruskal introduced a measure of predictive association when predicting the category of a variable A from a category of a variable B. This measure, denoted λ, is the asymmetric proportional reduction in error measure in predicting an individual's A category that can be eliminated by using knowledge of the B classification. It takes values on the unit interval, with a zero value meaning no predictive gain, while a value of unity indicates a perfect predictive association between A and B. A test of H0: λ = 0 versus H1: λ > 0 is analogous to a test for the significance of the correlation coefficient. A test of the partial λ coefficient, which is analogous to a test of the partial correlation coefficient, answers the question of whether knowledge of an additional third (or higher) classification or categorical variable results in a significant increase in predicting the variable A. Suich and Turek developed an exact test for the partial λ coefficient, but only for the situation where the predicted categorical variable A is dichotomous. The present paper completes the previous work by developing an asymptotic test where the predicted category A is any polytomous variable.
A fast method for choosing the numbers of components in Tucker3 analysis
Authors: Kiers Henk A. L. , der Kinderen Albert
Published: May 2003

Recently, Timmerman and Kiers proposed an effective procedure for choosing the numbers of components in Tucker3 analysis, a kind of component analysis of three‐way data. The procedure, however, is rather time‐consuming, relying on very many complete Tucker3 analyses. Here, an alternative procedure is proposed, which basically relies on a single, quick analysis of the three‐way data set. In a simulation study it was found that the new procedure is comparable in its effect to the original procedure.
Evaluation of global testing procedures for item fit to the Rasch model
Authors: Suárez‐Falcón Juan C. , Glas Cees A. W.
Published: May 2003

Two types of global testing procedures for item fit to the Rasch model were evaluated using simulation studies. The first type incorporates three tests based on first‐order statistics: van den Wollenberg's Q1 test, Glas's R1 test, and Andersen's LR test. The second type incorporates three tests based on second‐order statistics: van den Wollenberg's Q2 test, Glas's R2 test, and a non‐parametric test proposed by Ponocny. The Type I error rates and the power against the violation of parallel item response curves, unidimensionality and local independence were analysed in relation to sample size and test length. In general, the outcomes indicate a satisfactory performance of all tests, except the Q2 test which exhibits an inflated Type I error rate. Further, it was found that both types of tests have power against all three types of model violation. A possible explanation is the interdependencies among the assumptions underlying the model.
Bayesian model selection for mixtures of structural equation models with an unknown number of components
Authors: Lee Sik‐Yum , Song Xin‐Yuan
Published: May 2003

This paper considers mixtures of structural equation models with an unknown number of components. A Bayesian model selection approach is developed based on the Bayes factor. A procedure for computing the Bayes factor is developed via path sampling, which has a number of nice features. The key idea is to construct a continuous path linking the competing models; then the Bayes factor can be estimated efficiently via grids in [0, 1] and simulated observations that are generated by the Gibbs sampler from the posterior distribution. Bayesian estimates of the structural parameters, latent variables, as well as other statistics can be produced as by‐products. The properties and merits of the proposed procedure are discussed and illustrated by means of a simulation study and a real example.
Pairwise multiple comparisons: A model comparison approach versus stepwise procedures
Authors: Cribbie Robert A. , Keselman H. J.
Published: May 2003

Researchers in the behavioural sciences have been presented with a host of pairwise multiple comparison procedures that attempt to obtain an optimal combination of Type I error control, power, and ease of application. However, these procedures share one important limitation: intransitive decisions. Moreover, they can be characterized as a piecemeal approach to the problem rather than a holistic approach. Dayton has recently proposed a new approach to pairwise multiple comparisons testing that eliminates intransitivity through a model selection procedure. The present study compared the model selection approach (and a protected version) with three powerful and easy‐to‐use stepwise multiple comparison procedures in terms of the proportion of times that the procedure identified the true pattern of differences among a set of means across several one‐way layouts. The protected version of the model selection approach selected the true model a significantly greater proportion of times than the stepwise procedures and, in most cases, was not affected by variance heterogeneity and non‐normality.
Lateral facial soft‐tissue prediction model: Analysis using Fourier shape descriptors and traditional cephalometric methods
Authors: Rose Adam D. , Woods Michael G. , Clement John G. , Thomas C. David L.
Published: May 2003

This study was designed to investigate the relationship between traditional skeletal cephalometric measurement and Fourier analysis of the lateral soft‐tissue profile. A random sample of 121 untreated subjects of European descent, with wide ranges of malocclusions and underlying facial patterns, was selected in the Orthodontic Unit at the University of Melbourne. Lateral cephalograms were available for all subjects. Both traditional lateral cephalometric analysis and Fourier soft‐tissue profile analysis were carried out. Multivariate statistical analysis among 11 hard‐tissue cephalometric measurements and the first 50 Fourier harmonics was then performed. This analysis formed the basis for a subsequently proposed soft‐tissue prediction model. From this model, 50 predicted x‐ and y‐harmonics were generated for each subject in the total sample. Calculation of Pearson's correlation coefficients between the actual and predicted harmonics revealed strong relationships for many of the lower‐order harmonics. To further test the model, the prediction‐coefficients derived from all 121 subjects were then used to make predictions for the first 50 x‐ and y‐harmonics for a subgroup of 10 independent test subjects. Once again, Pearson's correlations between the actual and predicted harmonics of the test model in the lower‐order harmonics revealed strong associations. Superimposition of the actual and predicted soft‐tissue outlines, however, revealed that much actual detail in the region between the nose and the chin was still lost using the predicted Fourier harmonics. This suggests that soft‐tissue prediction based on this Fourier test model, while already useful in Forensic facial reconstruction, may not yet be appropriate for useful diagnosis and planning in clinical disciplines. Am J Phys Anthropol 121:000–000, 2003. © 2003 Wiley‐Liss, Inc.
Hopi Indians, “cultural” selection, and albinism
Authors: Hedrick Philip W.
Published: May 2003

The incidence of albinism in Hopi Indians has been estimated as approximately 1 in 200 individuals. It has been suggested that “cultural” selection as the result of a mating advantage of males with albinism has been important in the maintenance of this high incidence. To examine this hypothesis quantitatively, a model that includes male‐mating advantage, mutation, and viability selection is analyzed. In order to play an important role in the maintenance of the high incidence of albinism, the necessary mating advantage of males with albinism appears unrealistically high. However, if the extent of viability selection against individuals with albinism is not as large as previously assumed, the necessary amount of mating advantage is not as high. Other related aspects are also discussed here, such as the type of albinism in Hopi Indians and its impact, the conditions for a polymorphism with male‐mating advantage and viability selection, and the time necessary to change the incidence of albinism either by the relaxation or institution of male‐mating advantage. Am J Phys Anthropol 121:000–000, 2003. © 2003 Wiley‐Liss, Inc.
Genetic structure of Mediterranean populations revealed by Y‐chromosome haplotype analysis
Authors: Quintana‐Murci Lluís , Veitia Reiner , Fellous Marc , Semino Ornella , Poloni Estella S.
Published: May 2003

The allelic variability at six Y‐chromosome‐specific polymorphisms (YAP, DYS19, DYS389‐I, DYS390, DYS391, and DYS392) was used to generate male‐specific haplotypes in 333 males representing 12 population samples from the region around the Mediterranean sea. Extreme interindividual variation was observed, as more than 160 distinct Y‐chromosome variants could be defined as six‐locus haplotypes. Concomitant with this high variability, low levels of population genetic structure were observed. In particular, a “core” of populations directly facing the north and the east of the Mediterranean basin, from the Middle East to the Italian Peninsula, was found to be genetically undifferentiated. This observation, supported by a reanalysis of Y‐specific binary polymorphisms in the same populations, suggests that at least part of the male‐specific gene pools of these populations has either a very recent common origin (that could be related with the Neolithic demic diffusion hypothesis), and/or that gene flow has played a significant role in shaping the patterns of genetic variability in this region. In agreement with both hypotheses, we found that the spatial distribution of DYS392 alleles revealed a marked differentiation between the East and the West of the Mediterranean area. Through the analysis of microsatellite variation, the time to the most recent common ancestor (TMRCA) of the YAP+ sublineage 4 has been estimated. The estimations, based on two different data sets, turn out to be quite recent (7,000–11,000 YBP), suggesting that this lineage may have been first introduced into Southern Europe through Neolithic migrations from the Middle East. Am J Phys Anthropol 121:000–000, 2003. © 2003 Wiley‐Liss, Inc.
Pre‐Columbian treponemal disease from 14th century AD Safed, Israel, and implications for the medieval eastern Mediterranean
Authors: Mitchell Piers D.
Published: May 2003

In 1912, 68 medieval crania were excavated from a cave at Safed in the eastern Mediterranean and brought to the United Kingdom. It is only recently that these skulls have been studied for evidence of disease. One adult individual demonstrates multiple lesions of the cranial vault, compatible with treponematosis. Radiocarbon dating suggests the year of death to be between 1290–1420 AD. This range equates to the mamluk period, just after the crusades. This is the oldest dated case of treponematosis in the Middle East, and the first to confirm its presence there before the epidemiologically important transatlantic voyage of Christopher Columbus. The finding has significant implications for our understanding of the introduction of the disease to the Middle East and of the medieval diagnosis of ulcerating skin conditions by medical practitioners in the Mediterranean world. Am J Phys Anthropol 121:000–000, 2003. © 2003 Wiley‐Liss, Inc.
Food procurement and tooth use in two sympatric lemur species
Authors: Yamashita Nayuta
Published: May 2003

This study of two lemur species (Lemur catta and Propithecus v. verreauxi) in Madagascar combines observations of food procurement and initial food placement in the mouth with comparisons to food toughness and external properties. Food toughness was hypothesized to play a decisive role in determining food placement during ingestion. It was found that tougher foods are generally ingested on the postcanines for all foods eaten. However, when leaves and fruits are analyzed separately, food size and shape, represented here by mass and food type, are more reliable predictors of initial food placement. Larger leaves and bulkier fruits and stalks are ingested posteriorly. Leaf toughness is not related to leaf size, though the toughness and size of the most commonly eaten fruits are correlated. Furthermore, ingestive food toughness, which is the maximum toughness, and “average” food toughness may make different mechanical demands on the masticatory apparatus that have consequences for jaw morphology. Am J Phys Anthropol 121:000–000, 2003. © 2003 Wiley‐Liss, Inc.
Brief communication: Ancient DNA prospects from Sri Lankan highland dry caves support an emerging global pattern
Authors: Reed Floyd A. , Kontanis Elias J. , Kennedy Kenneth A.R. , Aquadro Charles F.
Published: May 2003

Recovery of ancient DNA has become an increasingly important tool in elucidating the origins of past populations and their relationships. Unfortunately, many human skeletal remains do not contain original DNA amplifiable by polymerase chain reaction (PCR). Amino‐acid racemization has proven to be a useful predictor of ancient DNA results. We analyzed the relative levels of amino‐acid preservation and racemization of human samples from two highland dry‐cave sites in Sri Lanka, and found that amino‐acid enantiomer ratios were inconsistent with successful authentic DNA recovery. A review of the literature reveals that these results are consistent with a global pattern of poor DNA preservation in the tropics. Am J Phys Anthropol 121:000–000, 2003. © 2003 Wiley‐Liss, Inc.
Longitudinal study of tuberculosis outcomes among immunologically naive Aché natives of Paraguay
Authors: Hurtado A. Magdalena , Hill Kim R. , Rosenblatt Wilhelm , Bender Jacquelyn , Scharmen Tom
Published: May 2003

This study documents the course of a tuberculosis epidemic in an immunologically naive group of South American Indians within fewer than 20 years after first sustained contact with outsiders. Groups of Northern Aché (ah‐CHAY) of eastern Paraguay were contacted and settled on reservations between 1971–1979. Not surprisingly, the Aché are very susceptible to tuberculosis, and the epidemiological characteristics of the disease are quite different from those of populations that have had tuberculosis for centuries. Within 6 years of the first detected case of tuberculosis among the Aché, the prevalence rate of active tuberculosis cases reached 18.2%, and of infected cases among adults, 64.6%, some of the highest rates ever reported for any human group. Remarkably, males and females are equally likely to have been diagnosed with active tuberculosis, Aché children between birth and 5 years of age are least vulnerable to tuberculosis, high nutritional and socioeconomic status do not decrease the risk of disease or infection, and children immunized with BCG are less responsive to tuberculin challenge than are other children. Moreover, similar to the Yanomamö, but unlike populations of European or African descent, a high percentage of Aché with active disease test negative on tuberculin challenge tests (purified protein derivative; PPD). These differences may be due to a high prevalence of diminished cell‐mediated immunity, and T‐helper 2 dominance. We also hypothesize that these immunological characteristics, low genetic diversity, hostile intergroup interactions, and behavioral noncompliance to treatment protocols together contribute to the high rates of active disease observed. Existing tuberculosis control programs are poorly equipped to handle the impact of these causal complexities on the course of recent tuberculosis epidemics that have quickly spread throughout native communities of Latin America during the last decade. Am J Phys Anthropol 121:000–000, 2003. © 2003 Wiley‐Liss, Inc.
Mitochondrial DNA from pre‐Columbian Ciboneys from Cuba and the prehistoric colonization of the Caribbean
Authors: Lalueza‐Fox C. , Gilbert M.T.P. , Martínez‐Fuentes A.J. , Calafell F. , Bertranpetit J.
Published: May 2003

To assess the genetic affinities of extinct Ciboneys (also called Guanajuatabeys) from Cuba, 47 pre‐Columbian skeletal samples belonging to this group were analyzed using ancient DNA techniques. At the time of European contact, the center and east of Cuba were occupied by agriculturalist Taino groups, while the west was mainly inhabited by Ciboneys, hunter‐gatherers who have traditionally been considered a relic population descending from the initial colonization of the Caribbean. The mtDNA hypervariable region I (HVR‐I) and haplogroup‐specific markers were amplified and sequenced in 15 specimens using overlapping fragments; amplification from second extractions from the same sample, independent replication in different laboratories, and cloning of some PCR products support the authenticity of the sequences. Three of the five major mtDNA Amerindian lineages (A, C, and D) are present in the sample analyzed, in frequencies of 0.07, 0.60, and 0.33, respectively. Different phylogenetic analyses seem to suggest that the Caribbean most likely was populated from South America, although the data are still inconclusive, and Central American influences cannot be discarded. Our hypothesis is that the colonization of the Caribbean mainly took place in successive migration movements that emanated from the same area in South America, around the Lower Orinoco Valley: the first wave consisted of hunter‐gatherer groups (ancestors of the Ciboneys), a subsequent wave of agriculturalists (ancestors of the Tainos), and a latter one of nomadic Carib warriors. However, further genetic studies are needed to confirm this scenario. Am J Phys Anthropol, 2003. © 2003 Wiley‐Liss, Inc.
Boiling water aging of polycarbonate and polycarbonate/acrylonitrile–butadiene–styrene resin and polycarbonate/low‐density polyester blends
Authors: Li Chaoqin , Zhang Yong , Zhang Yinxi
Published: May 2003

The effects of boiling water on the mechanical and thermal properties and morphologies of polycarbonate (PC), PC/acrylonitrile–butadiene–styrene resin (PC/ABS), and PC/low‐density polyester (PC/LDPE) blends (compositions of PC/ABS and PC/LDPE blends were 80/20) were studied. PC and the PC/ABS blend had a transition from ductile to brittle materials after boiling water aging. The PC/LDPE blend was more resistant to boiling water aging than PC and the PC/ABS blend. The thermal properties of glass‐transition temperature (Tg) and melting temperature (Tm) in PC and the blends were measured by DSC. The Tg of PC and PC in the PC/ABS and PC/LDPE blends decreased after aging. The Tg of the ABS component in the PC/ABS blend did not change after aging. The supersaturated water in PC clustered around impurities or air bubbles leading to the formation of microcracks, which was the primary reason for the ductile–brittle transition in PC, and the microcracks could not recover after PC was treated at 160°C for 6 h. The PC/ABS blend showed slightly higher resistance to boiling water than did PC. The highest resistance to boiling water of the PC/LDPE blend may be attributed to its special structural morphology. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 589–595, 2003
Preparation of metal‐containing protein fibers and their antimicrobial properties
Authors: Tsukada M. , Arai T. , Colonna G. M. , Boschi A. , Freddi G.
Published: May 2003

Bombyx mori silk, Antheraea pernyi silk, and wool fibers were chemically modified by treatment with tannic acid (TA) or by acylation with ethylenediaminetetraacetic (EDTA) dianhydride. Kinetics of TA loading or acylation with EDTA‐dianhydride varied from fiber to fiber. B. mori silk and wool displayed the highest weight gains with TA and EDTA‐dianhydride, respectively. The uptake of different metal ions (Ag+, Cu2+, Co2+) by protein fibers, either untreated or chemically modified, was studied as a function of weight gain and pH of the aqueous metal solution. Below pH 7, absorption of metal ions by untreated and TA‐treated fibers was negligible. Acylation with EDTA‐dianhydride enabled protein fibers to absorb and bind significant amounts of metal ions in the acidic and neutral pH range. The levels of metal desorption at acidic pH depended on the fiber‐metal combination. Untreated protein fibers usually displayed the lowest stability of the metal complex. Metal complexes with protein fibers exhibited prominent antimicrobial activity against the plant pathogen Cornebacterium. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 638–644, 2003
Using an electronic microbalance technique to study the stick–slip behavior of lubricated polypropylene fibers
Authors: Behary N. , Campagne C. , Caze C. , Perwuelz A.
Published: May 2003

By use of an electronic microbalance, fiber/fiber friction measurements were made on cleaned and lubricated polypropylene (PP) filaments. The filaments were coated with a 0.14‐μm‐thick layer of one of the five lubricants: two different hydroxylated oils (hydroxylated oleate and hydroxylated stearate) and three different ethoxylated surfactants [(i) ethoxylated 10 OE dioleate; (ii) ethoxylated 15 OE dioleate; and (iii) ethoxylated 20 OE trioleate]. Despite the thick layer of lubricant applied, stick–slip persisted. Theoretical considerations of experimental conditions (load, speed, and viscosity) show that the pressure is very high at the contact point, and this would induce film thinning and thus stick–slips arising from phase transitions. Statistical evaluations and atomic force microscopy images show that contacts between PP surfaces take place in presence of lubricants because surface asperity heights are larger than the lubricant film thickness. Oils or surfactants having similar surface tensions give different interfiber cohesion. Some explanations correlating the lubricant chemical structure and its spatial conformation, as well as its capacity to form intermolecular bonds and associative organization, to interfiber friction are given. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 645–654, 2003
Synthesis of a well‐defined chitosan graft poly(methoxy polyethyleneglycol methacrylate) by atom transfer radical polymerization
Authors: El Tahlawy K. , Hudson S. M.
Published: May 2003

Graft copolymerization of vinyl monomers onto chitosan and other natural polymers using atom transfer radical polymerization has only recently attracted interest. This technique could potentially provide new ways to utilize this abundant natural polymer. It would enable a wide variety of molecular designs to afford novel types of tailored hybrid materials composed of natural polysaccharides and synthetic polymers. In this work, a chitosan macroinitiator was prepared by the reaction of chitosan with 2‐bromo‐isobutyryl bromide, after the chitosan amino group had been protected as the imine. The aqueous grafting of methoxy capped (PEG 350) methacrylate onto chitosan is described. The kinetic study revealed a first order polymerization reaction. Polydispersities of about 1.25 were obtained. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 901–912, 2003
Oxygen barrier properties of PET copolymers containing bis(2‐hydroxyethyl)hydroquinones
Authors: Andrade Genara S. , Collard David M. , Schiraldi David A. , Hu Yushan , Baer Eric , Hiltner Anne
Published: May 2003

A series of poly[ethylene‐co‐bis(2‐ethoxy)hydroquinone terephthalate], PET‐co‐BEHQ copolymers were prepared by polymerization of various substituted bis(2‐hydroxyethyl)hydroquinones (BEHQs), dimethyl terephthalate (DMT), and ethylene glycol (EG). In addition to copolymers containing 6–16.5 mol % BEHQ, the homopolymer of BEHQ with dimethyl terephthalate, p(BEHQ‐T), was also prepared. The thermal and barrier properties of amorphous materials were studied. As the amount of comonomer was increased, the Tg and Tm of the materials decreased relative to those of PET. Oxygen permeability also decreased with increasing comonomer content. This improvement in barrier‐to‐oxygen permeability was primarily due to a decrease in solubility of oxygen in the polymer. All of the copolymers tested displayed similar oxygen diffusion coefficients. The decrease in solubility correlates with the decrease in Tg. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 934–942, 2003
Thermal behaviors of flame‐retardant polycarbonates containing diphenyl sulfonate and poly(sulfonyl phenylene phosphonate)
Authors: Wang Yu‐Zhong , Yi Bing , Wu Bo , Yang Bing , Liu Ya
Published: May 2003

Potassium diphenyl sulfonate (SSK), poly(sulfonyl phenylene phosphonate) (PSPPP), and their mixtures are proved to be effective flame‐retardants for polycarbonates (PCs) by measuring the limited oxygen index values and UL‐94 of blends. The flame‐retardant systems are characterized by thermogravimetric analysis under dynamic conditions. The resulting data, together with the analysis of the activation energies, demonstrates that the additives accelerate thermodegradation, especially in the early stage, and different additives cause a different process in the final stage. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 882–889, 2003
Miscibility behavior and coil overlap in ionic blends of phenylated polytriphenylene oxide and poly(methyl methacrylate)
Authors: Rajagopalan M. , Natansohn A. , Eisenberg A. , Tannenbaum R.
Published: May 2003

Blends of sulfonated phenylated polytriphenylene oxide and poly(methyl methacrylate‐co‐4‐vinyl pyridine) were examined by dynamic mechanical, Fourier transform infrared, and NMR techniques. A high degree of miscibility was evident from a single drop in a plot of the storage modulus versus the temperature. The presence of ionic moieties due to proton transfer from sulfonic acid to 4‐vinyl pyridine was confirmed by both NMR and IR spectroscopy studies. The coils were found to be close to one another in dimethyl sulfoxide‐d6 because the aromatic shielding effect of the phenyl rings of the phenylated polytriphenylene oxide units was observed from the upfield shift of most of the protons of poly(methyl methacrylate) in the NMR spectrum. However, the absence of cross peaks in the nuclear Overhauser and exchange spectroscopy experiments suggested that the intermolecular distance between the chains had to be larger than 4 Å. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 728–733, 2003
Structural insights into a novel molecular‐scale composite of soluble poly(vinyl pyrrolidone) supporting uniformly dispersed nanoscale poly(vinyl pyrrolidone) particles
Authors: Hood David K. , Senak Laurence , Kopolow Steven L. , Tallon Michael A. , Kwak Yoon Tae , Patel Drupesh , McKittrick John
Published: May 2003

Structural insights into a novel, molecular‐composite poly(vinyl pyrrolidone) consisting of a soluble, film‐forming poly(vinyl pyrrolidone) (PVP) polymer and in situ formed, minute, crosslinked, nanoscale, insoluble poly [poly(vinyl pyrrolidone)] (PPVP) polymer particles are reported. A technique for determining the PVP molecular weight and PPVP weight fraction by gel permeation chromatography/multi‐angle light scattering (MALS) is described. Particle size studies by quasi‐elastic light scattering and field flow fractionation/MALS demonstrate that the nanoscale, insoluble polymer particles are nominally 370 and 325 nm in diameter, respectively. Rheological experiments on this dispersed system yield a complex macroscopic behavior. Atomic force microscopy images confirm a substantial heterogeneous nature for a film cast from this molecular‐composite material. Finally, this polymeric molecular composite in film form exhibits, among many other interesting properties, a dramatic enhancement in water resistance, as demonstrated by a simple image water resistance test for an ink‐jet printing application. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 734–741, 2003
Mechanochemical improvement of the flame‐retardant and mechanical properties of zinc borate and zinc borate–aluminum trihydrate‐filled poly(vinyl chloride)
Authors: Pi Hong , Guo Shaoyun , Ning Yong
Published: May 2003

In this study, the effect of the high‐energy mechanical milling of a mixture of poly(vinyl chloride) (PVC) with zinc borate (ZB) or ZB–aluminum trihydrate (ATH), a mixture of ZB and ATH, on the flame‐retardant and mechanical properties of ZB and ZB–ATH filled PVC was examined. The high‐energy mechanical milling of PVC/ZB and the PVC/ZB–ATH mixture produced chemical bonding between PVC and ZB or ZB–ATH, increasing the interfacial interaction of PVC/ZB and PVC/ZB–ATH blends, which resulted in a great increase in the limiting oxygen index, the impact and yield strengths, and the elongation at break of PVC/ZB and PVC/ZB–ATH blends. The results from ultraviolet spectroscopy and gas chromatography–mass spectroscopy show that mechanochemical modification of ZB and ZB–ATH much more effectively suppressed the release of aromatic compounds in PVC/ZB and PVC/ZB–ATH blends during burning. Mechanochemical modification provided an excellent route for the improvement of the flame‐retardant and mechanical properties of flame‐retardant‐additive‐filled PVC. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 753–762, 2003
Production of polystyrene/poly(ethylene glycol dimethacrylate) composite particles encapsulating hinokitiol
Authors: Okubo M. , Minami H. , Jing Y.
Published: May 2003

Polystyrene (PS)/poly(ethylene glycol dimethacrylate) composite polymer particles containing hinokitiol (HT) were produced by suspension polymerization for ethylene glycol dimethacrylate droplets by the dissolution of HT and PS in poly(vinyl alcohol) aqueous solution. The composite particle had a hollow structure in which HT was included. The evaporation rate of HT from the composite particles became slower than that of pure HT. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 706–710, 2003
Modifying tubule distribution in tubule‐filled composites by using polyurethane–polydimethylsiloxane interpenetrating polymer networks
Authors: Chiou Bor‐Sen , Lankford Andrew R. , Schoen Paul E.
Published: May 2003

Microtubules that were made from a phospholipid and coated with copper to become electrically conductive were incorporated into a polyurethane–polydimethylsiloxane (PU‐PDMS) interpenetrating polymer network. The tubule concentration ranged from 8 to 16 vol %, whereas the PDMS concentration ranged from 0 to 75 wt %. The composites' dielectric properties and morphology were characterized by using a vector network analyzer and an optical microscope. In the composites the tubules became segregated into the polyurethane phase and were excluded from the PDMS phase. This forced the tubules closer together and resulted in the sample being closer to percolation. Consequently, for a specific tubule concentration, the real part of the permittivity increased for higher PDMS concentrations. In addition, adding tubules changed the morphology of the matrix. The dispersed PDMS globules were smaller in the composites than in the neat interpenetrating polymer network. The reason was that the tubules increased the viscosity of the system, which prevented the smaller PDMS globules from coalescing to form larger globules. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1032–1038, 2003
Isothermal crystallization of poly(vinyl alcohol–co–ethylene)
Authors: Alvarez Vera A. , Kenny José M. , Vázquez Analía
Published: May 2003

Isothermal melt crystallization of poly(vinyl alcohol–co–ethylene) with different ethylene contents was studied in the temperature range of 140°C–160°C. A differential scanning calorimeter was used to follow the energy of the crystallization process. The results were analyzed by Avrami and Hoffman–Laurizten methods. The Avrami exponent was close to 2, indicating two‐dimensional growth with a linear growth rate and crystals nucleating athermally. The equilibrium melting temperature was determined by the Hoffman–Weeks method. The rate of crystallization depended on ethylene content and temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1071–1077, 2003
A novel wood‐binding domain of a wood–plastic coupling agent: Development and characterization
Authors: Zhang C. , Li K. , Simonsen J.
Published: May 2003

Poly(N‐acryloyl dopamine) (PAD) was successfully synthesized through free‐radical homopolymerization of N‐acryloyl‐O,O′‐diphenylmethyldopamine and subsequent deprotection. The adhesive ability of PAD to wood was studied in detail. PAD underwent substantial oxidation and crosslinking reactions at about 80°C. Therefore, maple veneer samples bonded with PAD powder at a press temperature of 120°C had high shear strength and high water resistance. In contrast to conventional wood adhesives such as phenol‐formaldehyde and urea‐formaldehyde resins, PAD resulted in an increase, rather than a decrease, in the shear strengths of two‐ply laminated maple veneer test specimens that had undergone a water soaking and drying treatment. A mixture of PAD and polyethylenimine (PEI) resulted in much higher shear strength than PAD alone. To achieve high shear strength and high water resistance, the maple specimens bonded with PAD–PEI mixtures had to be cured above 150°C because reactions between PAD and PEI occurred at about 150°C. The water resistance of the maple specimens bonded with the PAD–PEI mixtures was dependent on the PAD:PEI weight ratio and the curing temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1078–1084, 2003
Toughening of polyethylene terephthalate/amorphous copolyester blends with a maleated thermoplastic elastomer
Authors: Yu Zhong‐Zhen , Lei Ming , Ou Yuchun , Yang Guisheng
Published: May 2003

The toughening of polyethylene terephthalate (PET)/amorphous copolyester (PETG) blends using a maleic anhydride grafted mixture (TPEg) of polyethylene‐octene elastomer and a semicrystalline polyolefin plastic (60/40 by weight) was examined. The TPEg was more effective in toughening PETG than PET, although the dispersion qualities of the TPEg particles in PET and PETG matrices were very similar. At the fixed TPEg content of 15 wt %, replacing partial PET by PETG resulted in a sharp brittle‐ductile transition when the PETG content exceeded the PET content. Before the transition, PET/PETG blends were not toughened with the TPEg of 15 wt %, whereas after the transition, the PET/PETG blends with 15 wt % of TPEg, similar to the PETG/TPEg (85/15) binary blend, maintained a super‐tough level. The impact‐fractured surfaces of the PET/PETG/TPEg blends were also evaluated. When PETG content was lower than PET content, the ternary blend showed a brittle feature in its impact‐fractured surface, similar to the PET/TPEg (85/15) binary blend. While PETG content exceeded PET content, however, the impact‐fractured surface of the ternary blend was very similar to that of PETG/TPEg (85/15) binary blend, exhibiting intensive cavitation and massive matrix shear yielding, which were believed to be responsible for the super‐tough level of the blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 797–805, 2003
Synthesis and characterization of σ–π conjugated poly(methylphenyldiethynylenesilane‐co‐methyltetraphenylphenylsilylene)
Authors: Li Meijiang , Feng Shengyu , Xie Shijie
Published: May 2003

Diacetylenemethylphenylsilane (1) and dichloromethyltetraphenylphenylsilane (2) were synthesized by the reactions of ethynylmagnesium bromide with dichloromethylphenylsilane and dichloromethylvinylsilane with tetraphenylcyclopentadienone, respectively. The copolymers of 1 and 2 were obtained by sodium condensation reaction. They were characterized by FTIR,1H‐ and 13C‐NMR, and both UV and fluorescence spectroscopy. The molecular weights of polymers were determined by GPC relative to polystyrene standards. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 806–810, 2003
Rheological properties and compatibility of NR/EPDM and NR/brominated EPDM blends
Authors: Lewis Chonlada , Bunyung Sunsanee , Kiatkamjornwong Suda
Published: May 2003

Ethylene–propylene–diene terpolymer (EPDM) was modified by bromination reaction. Blending the resulting brominated EPDM with natural rubber (STR5L) and blending the unmodified EPDM with STR5L at various compositions were carried out. The rheological properties of the blends were investigated using a capillary extrusion. Shear flow curves of the pure rubbers and their blends illustrated the pseudoplastic property as shear thinning behavior with a power law index n < 1. True shear viscosity of all blends showed the negative deviation in relation to their additive values. Rheological behavior and two Tg's found from the DSC thermograms at all blend compositions indicated blend incompatibility for both sets of blends. The incompatibility of the vulcanized blends was also found by measuring the spin–spin relaxation time T2 by pulsed NMR. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 837–847, 2003
Effects of fillers, maleated ethylene propylene diene diene rubber, and maleated ethylene octene copolymer on phase morphology and oil resistance in natural rubber/nitrile rubber blends
Authors: Sirisinha Chakrit , Limcharoen Sauvarop , Thunyarittikorn Jarunee
Published: May 2003

The phase morphology and oil resistance of 20/80 NR/NBR blends filled with different types of fillers and copolymers were investigated. In the case of filler effect, N220, N330, and N660 carbon blacks with different particle sizes were used. Additionally, the blends filled with nonblack‐reinforcing fillers, that is, precipitated and silane‐treated silica, were investigated. To study the compatibilization effect, maleated ethylene propylene diene rubber (EPDM‐g‐MA) and maleated ethylene octene copolymer (EOR‐g‐MA) were added to the blends. The results revealed that the addition of filler, either carbon black or silica, to the blend caused a drastic decrease in NR dispersed phase size. Carbon blacks with different particle sizes did not produce any significant difference in NR dispersed phase size under the optical microscope. Silica‐filled blends showed lower resistance to oil than did the carbon black–filled blends. In addition, it was determined that neither EOR‐g‐MA nor EPDM‐g‐MA could act as a compatibilizer for the blend system studied. The oil resistance of the blends with EPDM‐g‐MA is strongly affected by the overall polarity of the blend. In the case of EOR‐g‐MA, the oil resistance of the blends is significantly governed by both overall polarity of the blend and phase morphology. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1156–1162, 2003
Functional anatomy and hemodynamic characteristics of vasa vasorum in the walls of porcine coronary arteries
Authors: Gössl Mario , Rosol Michael , Malyar Nasser M. , Fitzpatrick Lorraine A. , Beighley Patricia E. , Zamir Mair , Ritman Erik L.
Published: May 2003

In this study vasa vasorum in the walls of porcine coronary arteries were examined, using three‐dimensional (3D) micro‐CT scanning techniques. These techniques leave the 3D structure of the vasa vasorum tree intact and thus provide a much more direct view of this structure than is possible from conventional histological sections. The study demonstrates—for the first time, we believe—both the different types and the fine architecture of these vasa vasorum. Furthermore, with the use of automated tree analysis software, it was possible to obtain quantitative geometrical data on the 3D structure of vasa vasorum trees that have not previously been available. The results indicate that despite the restrictive topology of the space in which they are present, the branching architecture of the vasa vasorum trees, which we surveyed, is surprisingly similar to that of vasculature in general. The volume of vessel wall tissue perfused or drained by a vasa vasorum tree was found to correlate well with the cross‐sectional area of the root segment of the vasa vasorum tree, and the luminal surface area corresponding to this volume was found to be comparable with the surface area of an early atherosclerotic lesion. This is consistent with earlier findings that the ligation or removal of vasa vasorum leads to atherogenesis. Anat Rec Part A 272A:526–537, 2003. Published 2003 Wiley‐Liss, Inc.
Neurocan in the embryonic avian heart and vasculature
Authors: Mishima Noboru , Hoffman Stanley
Published: May 2003

The chondroitin sulfate proteoglycan (CSPG) neurocan was previously considered to be nervous‐system specific. However, we have found neurocan in the embryonic heart and vasculature. In stage 11 quail embryos, neurocan was prominently expressed in the myocardium, dorsal mesocardium, heart‐forming fields, splanchnic mesoderm, and vicinity of the extraembryonic vaculature, and at lower levels in the endocardium. A comparison of neurocan staining with QH1 staining of vascular endothelial cells demonstrates that neurocan is frequently expressed by cells adjacent to endothelial cells, rather than by endothelial cells themselves. In some cases, a dispersed subset of cells are neurocan‐positive in a field of cells that otherwise appear uniform in morphology. Later in development, neurocan expression becomes relatively limited to the nervous system. However, even in 10‐day embryos, neurocan is expressed in the chorio‐allantoic membrane in the tissue that separates closely packed, small‐diameter blood vessels. In summary, our results suggest that neurocan may function as a barrier that regulates vascular patterning during development. Anat Rec Part A 272A: 556–562, 2003. © 2003 Wiley‐Liss, Inc.
Renal corpuscle of the sturgeon kidney: An ultrastructural, chemical dissection, and lectin‐binding study
Authors: Ojeda José L. , Icardo José M. , Domezain Alberto
Published: May 2003

The sturgeon is an ancient species of fish that thrives in a wide range of ecological environments, from freshwater to seawater. Basic in this process of adaptation is the ability of the kidney to control fluid filtration and urine formation. However, the morphological basis of this process is mostly unknown. The aim of the present study was to use microdissection techniques (scanning electron microscopy (SEM), transmission electron microscopy (TEM), and lectin‐binding histochemistry) to examine the structure of the renal corpuscle of the sturgeon Acipenser nacarii in order to reveal morphologic features that could be related to function, phylogeny, and habitat. The renal corpuscles are aligned along the intrarrenal arteries. The urinary pole shows a siphon‐like neck segment (NS) in 92% of the nephrons, whose structural characteristics are different from those of other fish. The podocytes have cuboidal cellular bodies, intercellular contacts, and poorly developed cell processes. The podocyte glycocalyx contains N‐acetylglucosamine and lacks sialic acid. The structural and lectin‐binding patterns are similar to those found in the immature mammalian kidney. The glomerular basement membrane (GBM) is very thick and consists of three layers: a lamina rara externa, a lamina densa, and a thick subendothelial lamina. The latter contains tubular microfibrils, collagen fibers, and long mesangial cell processes. Frequently, the podocyte bodies attach directly to the GBM, and the area occupied by the filtration slits is very small. Furthermore, the GBM shows a glycosylation pattern different from that observed in most vertebrates. Contrary to what would be expected in sturgeons living in freshwater, the A. nacarii renal corpuscle morphology suggests a low glomerular filtration rate. Anat Rec Part A 272A: 563–573, 2003. © 2003 Wiley‐Liss, Inc.
On some measures and distances for positive random variables
Authors: Finkelstein M. S.
Published: May 2003

A number of conventional measures of risk as real‐valued functions on the space of positive random variables are considered: the expected shortfall, the mean excess over the threshold, the stop‐loss and some others. Ordering of risks, based on these measures and the distances between corresponding distribution functions, are described. The perturbed measures, describing the effect of changing environment, are discussed. These measures are defined by the accelerated life and proportional hazards models widely used in reliability and survival analysis. The case of a random environment is of a prime interest in the paper. The main result states that if, for instance, the stochastic environment is ‘neutral in expectation’ with respect to the baseline one, the distance between the corresponding distribution functions can be still sufficiently large. Copyright © 2003 John Wiley & Sons, Ltd.
Release kinetics of transforming growth factor‐β1 from fibrin clots
Authors: Giannoni Paolo , Hunziker Ernst B.
Published: May 2003

In any therapeutic model involving a tissue‐engineering approach to the repair of partial‐thickness articular cartilage defects, a chondrogenic differentiation factor is required to ensure tissue‐specific healing. Transforming growth factor‐β1 (TGF‐β1) is known to act in this capacity, but at such high concentrations as to render its direct injection into the joint cavity inadvisable. This situation calls for a delivery system that can be applied directly to the defect site and that will release the drug gradually over a period of some weeks. Liposome encapsulation represents one such system, and has been recently implemented with some success in an animal model for cartilage repair. However, the kinetics of TGF‐β1 release have not been determined, it was the purpose of the present study to characterize these. The liberation of [125I]‐labeled TGF‐β1 from fibrin matrices containing this agent in either a free or liposome‐encapsulated form was monitored by liquid scintillation counting for 25 days in vitro. During the initial 5 days, fibrin clots containing liposome‐encapsulated TGF‐β1 released this cytokine at a slower rate (2% to 4% per day) than did those containing the free molecules (10% to 20% per day); thereafter, the release rates were similar. At the end of the incubation period, only 40% of the liposome‐encapsulated TGF‐β1 had been released from the fibrin clots, as compared with 68% from those containing the free molecules. Liposome encapsulation thus represents a suitable means of establishing a slow‐delivery system in tissue‐engineering approaches to articular cartilage repair. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 121–123, 2003.