bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of stress‐induced crystallization in high‐cis‐1,4‐polybutadiene
Authors: De Candia F. , Romano G. , Russo R. 
Published: April 2003

AbstractStress‐induced crystallization of a crosslinked polybutadiene with a high 1,4‐cis content is investigated, at room temperature. The change in the fraction of crystallinity with deformation is evaluated by two different methods. The first is based on simultaneous measurement of birefringence and stress. The second is based on calorimetric analysis. The data on crystallinity obtained by these two methods are in good agreement in the range of low deformations, while, in the range of higher deformation (λ > 5), the degree of crystallinity obtained by calorimetry is higher than that obtained by the optical method. Qualitative information on the crystallization was also obtained by optical analysis of the hysteresis behavior. The hysteresis data show the presence of ordering phenomena at deformations at which there seems to be no crystallinity according to both quantitative methods.
Dependence of chain conformation and solution thermodynamics on composition for poly(ortho ester)s prepared from ketene acetals and mixtures of diols
Authors: Cotts D. B. 
Published: April 2003

AbstractThe solution properties of a series of random copolymers prepared from ketene acetals with mixtures of diols have been characterized by dilute solution light scattering, chromatographic, and viscometric techniques. Five solvents with refractive indices ranging from 1.4 to 1.5 were used to obtain the correct weight average molecular weight. Changes in the unperturbed radius of gyration, obtained by combined size exclusion chromatography and low‐angle light scattering techniques, parallelled that predicted by simple considerations of changes in repeat unit size. Thus the relative contributions of differing copolymer–solvent interactions and changing unperturbed radii of gyration to the hydrodynamic volume of random copolymers of different compositions were evaluated.
Studies on the morphology and structure of aromatic polyester films
Authors: Hu Shiru , Xu Mao , Li Jianchang , Qian Baogong , Wang Xiayu , Lenz Robert W. 
Published: April 2003

AbstractOriented films of an aromatic polyester containing a triad ester mesogenic group and a decamethylene flexible spacer were studied by polarized light microscopy, small‐angle light scattering, and polarized infrared spectroscopy to determine the nature of the alignment of the polymer chains, induced by shearing, which is responsible for the banded or striped morphology observed. The stripes are apparently composed of fibrils arranged in a zigzag manner containing polymer chains packed in a highly ordered, parallel alignment at an angle of ±26° to the shearing direction.
Study of temperature dependence of thermal diffusion in polystyrene/ethylbenzene by thermal field‐flow fractionation
Authors: Brimhall Steven L. , Myers Marcus N. , Caldwell Karin D. , Giddings J. Calvin 
Published: April 2003

AbstractUsing a special thermal field‐flow fractionation apparatus capable of working over a broad temperature range, we have observed that retention in the polystyrene/ethylbenzene system decreases substantially as the cold wall temperature increases from 360 to 424 K. Polymers of four different molecular weights ranging from 20,000 to 160,000 were used to verify this conclusion. Based on our earlier work showing that thermal diffusion parameters could be calculated from retention data, we have used the present measurements along with earlier values to generate a compilation of thermal diffusion data over the temperature range from 270 to 424 K. These results are used to develop empirical expressions for the thermal diffusion factor and the thermal diffusion coefficient for polystyrene in ethylbenzene as a function of temperature and molecular weight. It is shown that these results have potential usefulness both in terms of the new physicochemical data obtained and in terms of the guidelines they provide for choosing experimental conditions for thermal field‐flow fractionation experiments.
Kinetics of wetting of a glass surface by molten polyethylene: An empirical approach
Authors: Pegoraro M. , Di Landro L. , Trifilo R. , Penati A. 
Published: April 2003

AbstractThe spreading kinetics of molten polyethylene was studied on a flat type A glass surface. Empirical equations are known in the literature which fit the experimental data only at short times. We present a relationship between the surface free energy and the shape of the melt drop interpreted by the θ contact angle. Relating the experimental θ values obtained at different times with the surface free energy (F), we obtain curves F,t. Using isothermal data at 150°C, we could fit them with a linear relationship between In (F‐F∞)/(F0‐F∞) and In t/t0, where o and ∞ are related to initial and equilibrium conditions.
Kink motion in poly(vinylidene fluoride) form I
Authors: Takahashi Yasuhiro , Miyamoto Noritake 
Published: April 2003

AbstractThe diffuse‐streak x‐ray scattering intensity from poly(vinylidene fluoride) form I, which is caused by kink bands with GTnḠ (n odd) conformation contained in the crystallite, decreases with increasing temperature, while the intensity of the 001 reflection does not change. This is attributed to the disappearance of the kink bands in the crystallite, not to partial melting of crystallites containing kink bands. The disappearance of the kink bands suggests that kink motion takes place in the crystallite. Plots of the intensity of diffuse‐streak scattering, estimated from the asymmetric part of the 001 reflection, against 1/T roughly give ΔHv = −4.6 kcal/mol. This suggests that the kink band is energetically more stable than the regular structure of form I.
On the mechanical preconditioning of ultrahigh‐molecular‐weight polyethylene at small uniaxial deformations
Authors: Crissman J. M. , Zapas L. J. 
Published: April 2003

AbstractThe results of creep and recovery experiments are reported for a sample of ultrahigh‐molecular‐weight polyethylene at three different temperatures and creep times in the range from 10 s to 1.47 X 106s. In order to approximate constant‐true‐stress conditions all the experiments were carried out at the same value of applied stress (4 MPa) and the change in strain during creep was never more than about 2%. It was found that within the range of conditions used the creep and recovery data could be described quite well by a one‐dimensional constitutive equation consisting of two terms, one a single integral hereditary term and the other a plasticity term. Further, it was shown that to a very good approximation the idea of time‐temperature superposition can be applied to the description of the hereditary term Ĵ (σ, T, t). We believe that the results described here provide greater insight into what constitutes “mechanical preconditioning” of semicrystalline polymers and further provide a relatively simple method for describing the uniaxial creep and recovery behavior of such materials.
Multiple additive regression trees with application in epidemiology
Authors: Friedman Jerome H. , Meulman Jacqueline J. 
Published: April 2003

AbstractPredicting future outcomes based on knowledge obtained from past observational data is a common application in a wide variety of areas of scientific research. In the present paper, prediction will be focused on various grades of cervical preneoplasia and neoplasia. Statistical tools used for prediction should of course possess predictive accuracy, and preferably meet secondary requirements such as speed, ease of use, and interpretability of the resulting predictive model. A new automated procedure based on an extension (called ‘boosting’) of regression and classification tree (CART) models is described. The resulting tool is a fast ‘off‐the‐shelf’ procedure for classification and regression that is competitive in accuracy with more customized approaches, while being fairly automatic to use (little tuning), and highly robust especially when applied to less than clean data. Additional tools are presented for interpreting and visualizing the results of such multiple additive regression tree (MART) models. Copyright © 2003 John Wiley & Sons, Ltd.
Regression methods for assessing familial aggregation of disease
Authors: Laird Nan M. , Cuenco Karen T. 
Published: April 2003

AbstractThis paper reviews methods for assessing familial aggregation of disease based on simple logistic regression models. Studies are based on a case‐control sampling design, where the disease status of the first degree relatives of both cases and controls are obtained. Both ‘proband predictive’ and ‘family predictive’ models are discussed, and an example is given using a case‐control sample from a lung cancer study in non‐smokers. The methods are extended to characterize co‐aggregation of two disorders, that is, presence of one disorder in the proband increases the risk of a second disorder in the relative. An example involving eating disorders and depression is given. Copyright © 2003 John Wiley & Sons, Ltd.
Using lowess to remove systematic trends over time in predictor variables prior to logistic regression with quantile categories
Authors: Borkowf Craig B. , Albert Paul S. , Abnet Christian C. 
Published: April 2003

AbstractIn case‐control studies one may employ logistic regression to model the relationship between binary responses and continuous predictor variables that have been categorized by the empirical quartiles of the controls. Sometimes, however, systematic trends over time (or drifts) contaminate the laboratory measurements of predictor variables. In this paper we consider the use of locally weighted robust regression (lowess) to estimate and remove these systematic trends when the trends for the cases and controls have a common shape. One can then use the lowess adjusted data in the desired logistic regression model. We illustrate these methods with a case‐control study that was designed to assess the risk of oesophageal cancer as a function of the quartile categories of sphinganine levels in the blood serum. Upon examination of the data, it was discovered that the sphinganine laboratory measurements were contaminated by a systematic trend, the magnitude of which depended only on the day of analysis. This trend needed to be removed before performing further analyses of the data. In addition, we present simulations to examine the use of lowess methods to estimate and remove various shapes of trends from contaminated predictor data before constructing logistic regression models with quartile categories. We found that using the trend‐contaminated data tends to give attenuated parameter estimates and hence lower significance and power levels than using the uncontaminated data. Conversely, using appropriate lowess methods to adjust the data tends to give nearly unbiased parameter estimates, near nominal significance levels, and improved power. Published in 2003 by John Wiley & Sons, Ltd.
Disease classification: measuring the effect of the Tenth Revision of the International Classification of Diseases on cause‐of‐death data in the United States
Authors: Anderson Robert N. , Rosenberg Harry M. 
Published: April 2003

AbstractThe purpose of this paper is to describe the statistical impact of the Tenth Revision of the International Classification of Diseases (ICD‐10) on cause‐of‐death data for the United States. ICD‐10 was implemented in the U.S. effective with deaths occurring in 1999. The paper is based on cause‐of‐death information from a large sample of 1996 death certificates filed in the 50 States and the District of Columbia. Cause‐of‐death information in the sample includes underlying cause of death classified by both ICD‐9 and ICD‐10. Preliminary comparability ratios by cause of death presented in this paper indicate the extent of discontinuities in cause‐of‐death trends from 1998 to 1999 resulting from implementing ICD‐10. For some leading causes (for example, septicaemia, influenza and pneumonia, Alzheimer's disease, and nephritis, nephrotic syndrome and nephrosis) the discontinuity in trend is substantial. Results of this study, although preliminary, are essential to analysing trends in mortality statistics between ICD‐9 and ICD‐10. In particular, the results provide a means for interpreting changes between 1998, which is the last year in which ICD‐9 was used, and 1999, the year in which ICD‐10 was implemented for mortality in the United States. Published in 2003 by John Wiley & Sons, Ltd.
On weighting the rates in non‐response weights
Authors: Little Roderick J. , Vartivarian Sonya 
Published: April 2003

AbstractA basic estimation strategy in sample surveys is to weight units inversely proportional to the probability of selection and response. Response weights in this method are usually estimated by the inverse of the sample‐weighted response rate in an adjustment cell, that is, the ratio of the sum of the sampling weights of respondents in a cell to the sum of the sampling weights for respondents and non‐respondents in that cell. We show by simulations that weighting the response rates by the sampling weights to adjust for design variables is either incorrect or unnecessary. It is incorrect, in the sense of yielding biased estimates of population quantities, if the design variables are related to survey non‐response; it is unnecessary if the design variables are unrelated to survey non‐response. The correct approach is to model non‐response as a function of the adjustment cell and design variables, and to estimate the response weight as the inverse of the estimated response probability from this model. This approach can be implemented by creating adjustment cells that include design variables in the cross‐classification, if the number of cells created in this way is not too large. Otherwise, response propensity weighting can be applied. Copyright © 2003 John Wiley & Sons, Ltd.
A method for comparing two normal means using combined samples of correlated and uncorrelated data
Authors: Looney Stephen W. , Jones Peter W. 
Published: April 2003

AbstractA method is proposed for comparing two normal means when the data consist of some observations that are correlated and others that are uncorrelated. Typically, such data will consist of one subsample in which the observations for treatment 1 and treatment 2 are independent of each other, and another subsample which consists of paired observations taken under both treatments. The proposed method is developed using asymptotic results and is evaluated using simulation. The simulation results indicate that the proposed method can provide substantial improvement in type I error rate and power when compared with standard methods of analysis. Copyright © 2003 John Wiley & Sons, Ltd.
A mixed‐effects multinomial logistic regression model
Authors: Hedeker Donald 
Published: April 2003

AbstractA mixed‐effects multinomial logistic regression model is described for analysis of clustered or longitudinal nominal or ordinal response data. The model is parameterized to allow flexibility in the choice of contrasts used to represent comparisons across the response categories. Estimation is achieved using a maximum marginal likelihood (MML) solution that uses quadrature to numerically integrate over the distribution of random effects. An analysis of a psychiatric data set, in which homeless adults with serious mental illness are repeatedly classified in terms of their living arrangement, is used to illustrate features of the model. Copyright © 2003 by John Wiley & Sons, Ltd.
Archiving — the full‐text solution: an innovative way to electronic archiving
Authors: Turner Alan , Steele Pippa 
Published: April 2003

ABSTRACTSomerset Computing Limited has developed a unique search engine that allows publishers and societies to produce electronic archives with full‐text searching and the ability to carry out high‐level search requests without major rekeying or tagging, making it the most cost‐effective solution for full‐text searching available. This technology has relevance to many publishing areas including legal publishers, academic publishers, STM publishers, learned societies and professional typesetters. This article describes how Somerset Computing has utilized its expertise and this innovative in‐house software to provide the British Academy with an affordable, fully searchable solution to the electronic archiving of the Proceedings of the British Academy.
E‐journals: developing country access survey
Authors: Smart Pippa 
Published: April 2003

ABSTRACTConcern over the information gap between developed and developing countries has led to a number of initiatives to promote access to information, but is there a potential of overlapping and conflicting information being given to the recipients? And what are publishers' attitudes towards the supply of their content at greatly reduced prices, or for free? During 2002 INASP was commissioned to undertake a survey to identify publishers' activities and opinions in this area. The survey found that the majority of respondents were involved in one or more access programmes and there was a willingness from both the commercial and the non‐commercial sector to provide their information in this way.
Book Reviews
Authors: Newton Rachel , Watkinson Anthony , Wood Dee 
Published: April 2003

Classification Made Simple (2nd edn) by Eric J. Hunter Ashgate Publishing Ltd 2002, Price £18.00, 160 pp., paperback, ISBN 0‐7546‐0795‐XInternet Law and Regulation (3rd edn) edited by Graham J.H. Smith Sweet & Maxwell, 2001, £145.00, 778 pp., hardback. ISBN 0‐421705906Super Searcher, Author, Scribe: Successful Writers Share their Internet Research Secrets by Loraine Page (series editor Reva Basch) CyberAge Books, 2002, $24.95, 225 pp. ISBN: 0910965587
Identification in Methicillin-Susceptible
Staphylococcus hominis
of an Active Primordial Mobile Genetic Element for the Staphylococcal Cassette Chromosome
mec
of Methicillin-Resistant
Staphylococcus aureus
Authors: Katayama Yuki , Takeuchi Fumihiko , Ito Teruyo , Ma Xiao Xue , Ui-Mizutani Yoko , Kobayashi Ichizo , Hiramatsu Keiichi 
Published: April 2003

ABSTRACT

We previously reported that the methicillin resistance gene
mecA
is carried by a novel type of mobile genetic element, SCC
mec
(staphylococcal cassette chromosome
mec
), in the chromosome of methicillin-resistant
Staphylococcus aureus
(MRSA). These elements are precisely excised from the chromosome and integrated into a specific site on the recipient chromosome by a pair of recombinase proteins encoded by the cassette chromosome recombinase genes
ccrA
and
ccrB.
In the present work, we detected homologues of the
ccr
genes in
Staphylococcus hominis
type strain GIFU12263 (equivalent to ATCC 27844), which is susceptible to methicillin. Sequence determination revealed that the
ccr
homologues in
S. hominis
were type 1
ccr
genes (
ccrA1
and
ccrB1
) that were localized on a genetic element structurally very similar to SCC
mec
except for the absence of the methicillin-resistance gene,
mecA.
This genetic element had mosaic-like patterns of homology with extant SCC
mec
elements, and we designated it SCC
12263
and considered it a type I staphylococcal cassette chromosome (SCC). The
ccrB1
gene identified in the
S. hominis
strain is the first type 1
ccrB
gene discovered to retain its function through the excision process as judged by two criteria: (i) SCC
12263
was spontaneously excised during cultivation of the strain and (ii) introduction of the
S. hominis ccrB1
into an MRSA strain carrying a type I SCC
mec
whose
ccrB1
gene is inactive generated SCC
mec
excisants at a high frequency. The existence of an SCC without a
mec
determinant is indicative of a staphylococcal site-specific mobile genetic element that serves as a vehicle of transfer for various genetic markers between staphylococcal species.
Structure-Function Studies of
Escherichia coli
RpoH (σ
32
) by In Vitro Linker Insertion Mutagenesis
Authors: Narberhaus Franz , Balsiger Sylvia 
Published: April 2003

ABSTRACT

The sigma factor RpoH (σ
32
) is the key regulator of the heat shock response in
Escherichia coli
. Many structural and functional properties of the sigma factor are poorly understood. To gain further insight into RpoH regions that are either important or dispensable for its cellular activity, we generated a collection of tetrapeptide insertion variants by a recently established in vitro linker insertion mutagenesis technique. Thirty-one distinct insertions were obtained, and their sigma factor activity was analyzed by using a
groE
-
lacZ
reporter fusion in an
rpoH
-negative background. Our study provides a map of permissive sites which tolerate linker insertions and of functionally important regions at which a linker insertion impairs sigma factor activity. Selected linker insertion mutants will be discussed in the light of known sigma factor properties and in relation to a modeled structure of an RpoH fragment containing region 2.
Type II Protein Secretion in
Pseudomonas aeruginosa
: the Pseudopilus Is a Multifibrillar and Adhesive Structure
Authors: Durand Éric , Bernadac Alain , Ball Geneviève , Lazdunski Andrée , Sturgis James N. , Filloux Alain 
Published: April 2003

ABSTRACT

The type II secretion pathway of
Pseudomonas aeruginosa
is involved in the extracellular release of various toxins and hydrolytic enzymes such as exotoxin A and elastase. This pathway requires the function of a macromolecular complex called the Xcp secreton. The Xcp secreton shares many features with the machinery involved in type IV pilus assembly. More specifically, it involves the function of five pilin-like proteins, the XcpT-X pseudopilins. We show that, upon overexpression, the XcpT pseudopilin can be assembled in a pilus, which we call a type II pseudopilus. Image analysis and filtering of electron micrographs indicated that these appendages are composed of individual fibrils assembled together in a bundle structure. Our observations thus revealed that XcpT has properties similar to those of type IV pilin subunits. Interestingly, the assembly of the type II pseudopilus is not exclusively dependent on the Xcp machinery but can be supported by other similar machineries, such as the Pil (type IV pilus) and Hxc (type II secretion) systems of
P. aeruginosa
. In addition, heterologous pseudopilins can be assembled by
P. aeruginosa
into a type II pseudopilus. Finally, we showed that assembly of the type II pseudopilus confers increased bacterial adhesive capabilities. These observations confirmed the ability of pseudopilins to form a pilus structure and raise questions with respect to their function in terms of secretion and adhesion, two crucial biological processes in the course of bacterial infections.