bluuebunny/crossref_metadata_2025 huggingface dataset:
Simplified analysis of gas/polymer selective solubility behavior
Authors: Koros William J.
Published: April 2003

Interactions of penetrants with gas separation membrane materials can have both desirable and undesirable consequences. Improved permselectivity resulting from specific polymer/penetrant interactions must be balanced against potentially undesirable plasticization effects resulting from such interactions. Consideration is given to the utility of gas solubility measurements in low‐molecular‐weight solvents as an aid to understanding solubility data for polymer/gas systems. The solubility coefficients of gases in low‐molecular‐weight liquids and in polymeric media of similar chemical structure tend to be quite different in magnitude. “Equation‐of‐state” and combinatorial entropy differences for the free energy of mixing of gases with low‐molecular‐weight solvents and high‐molecular‐weight polymers presumably cause this discrepancy. The above complications are minimized and useful trends identified by considering the so‐called solubility selectivity comprised of ratios of absolute gas solubilities in both low‐and high‐molecular‐weight media of similar chemical natures. For example, both acetone and methyl acetate are highly sorptive of CO2 and display a high degree of solubility selectivity for CO2 relative to CH4. These two solvents have mass densities of carbonyl groups that are similar to that in cellulose acetate and poly(methyl methacrylate). Both of these polymers are also highly sorptive of CO2 and have solubility selectivities for CO2 relative to CH4 that are similar to that of acetone and methyl acetate. Anomalous behavior is encountered in the case of Kapton poly(ether diimide), which contains a high density of carbonyl groups (four per repeat unit). On the basis of the behavior of the other carbonyl‐rich polymers, it was expected that Kapton would show high solubility selectivity for CO2 relative to CH4, but this was not observed. A hypothetical explanation for the Kapton behavior is presented. In addition, possible advantages of the Kapton‐type behavior are discussed in the context of the reported good plasticization resistance of polyimides.
A new model for the molecular conformation in polyoxymethylene crystals
Authors: Saruyama Y. , Miyaji H.
Published: April 2003

Nonintegral indices are found for the extra meridional reflections in the x‐ray diffraction of drawn polyoxymethylene. The index of one of the extra reflections is estimated at 00l: l = 2.830 ± 0.003. A new model for the molecular conformation which accounts for the nonintegral indices is proposed. The new model is a helix with defects at constant intervals along the helix axis. The defect is an unwinding of the helix by 20° around the helix axis. This defect is believed to be characteristic of crystals of helical polymers. The interval between the defects is estimated as 18 monomers. The crystal structure with these defects is consistent with precise measurements of the layer line positions.
Configurational studies on amylose. II. Moments and distribution functions
Authors: Yamaguchi Saburo , Hayashi Hisao , Hamada Fumiyuki , Nakajima Akio
Published: April 2003

Statistical mechanical averages of vectors and tensors characterizing the configuration of amylose chains have been calculated. These quantities are expressed in the reference frame affixed to the first glucose unit, the x axis being situated along the O(4)—O(1) virtual bond vector, and the Y axis in the plane of the virtual bond and the O(4)—C(4) bond. The persistence vector a as defined by the average of the end‐to‐end vector r converges slowly to the limiting persistence vector a∞ with increasing chain length. Configurational averages of the Cartesian tensors formed from the displacement vector ρ = r − a have been computed up to seventh rank according to the generator matrix method. The density distribution functions Wα (ρ) evaluated for xu = 40 by using the three‐dimensional Hermite polynomial expansion truncated at the term involving the tensor of seventh rank are approximately cylindrically symmetric about one of the principal axes of the second‐moment tensor <ρ×2. The density distribution function Wα(ρ) is slightly asymmetric even for xu = 80.
Statistical description of spherulite patterns
Authors: Piórkowska E. , Gałeski A.
Published: April 2003

A statistical description of spherulitic morphology and its formation resulting from primary nucleation and radial propagation is presented. Two‐ and three‐dimensional cases are considered. The general formulas are valid for any time‐dependent mode of primary nucleation and can be modified for a time‐dependent propagation rate. Various distance distributions of boundaries and inner points of the final pattern and at intermediate stages of its formation as well as the degree of conversion and the distance correlation of primary nuclei are derived. Detailed derivations are carried out for three model modes of primary nucleation, athermal, thermal, and mixed. It is also shown that the degree of conversion from mixed‐mode nucleation does not follow the Avrami plot. The total surface of boundaries in bulk, total length of boundaries on a plane, and numbers of multiple boundary points are also calculated for all modes of primary nucleation. The relations are confirmed by computer simulation of primary nucleation and radial propagation of spherulites on a plane and in bulk.
Depolarization field effect on the ferroelectric behavior of polymers
Authors: Ikeda Susumu , Jimbo Masashi , Kobayashi Shin'Ichi , Wada Yasaku
Published: April 2003

The effect of the depolarization field in crystallites on the ferroelectric behavior of polymers is discussed on the assumption that the crystallite is a prolate ellipsoid with its major axis directed along the electric field. The theory relates the polarization P and the electric field E in the crystallite to the overall values P and E for the polymer. The determination of the P‐E hysteresis of a crystallite from the P‐E hysteresis is given with examples for poly(vinylidene fluoride) (PVDF) and vinylidene fluoride (VDF)–trifluoroethylene (TrFE) copolymer. The ratio R = J/(Ps − P), with J the switching current density and Ps the saturation polarization of polymer, is proved to be free from the depolarization field effect and the plot of logR against logarithmic time is shown to have merit for characterization of switching behavior. Examples of the curves are given for PVDF and VDF‐TrFE copolymers. The temporal change of local electric field in the unreversed domains in the crystallite in the course of polarization reversal is predicted by the theory and this change is proved to be a significant mechanism of switching acceleration.
Sorption and diffusion of a tribasic acid dye in nylon 6 membrane in the presence of NaCl
Authors: Kawana Y. , Komiyama J. , Petropoulos J. H. , Iijima T.
Published: April 2003

Measurements of sorption and diffusion of a tribasic acid dye in nylon 6 membranes in the presence of NaCl are reported and critically analyzed by the dual‐mode sorption and diffusion models consisting of either simple partition plus ion exchange, or simple partition plus “Langmuir” modes. It is shown that the former treatment, which is the physically more realistic one, also provides a generally better fit to the data.
Far‐infrared studies of microphase separation in sulfonated ionomers
Authors: Peiffer D. G. , Hager B. L. , Weiss R. A. , Agarwal P. K. , Lundberg R. D.
Published: April 2003

Far‐infrared spectra of a series of un‐neutralized and neutralized lightly sulfonated polystyrenes with varying sulfonation levels have been investigated to seek spectroscopic evidence for microphase separation known to control the physical properties of these polymers. Broad, strong absorbance bands, not found in the spectrum of unmodified polystyrene, are observed in the spectra of the sulfonated analogs. The effects on the far‐infrared spectra both of sulfonation level and of the mass and charge of the neutralizing cation are discussed in terms of cation motion and the formation of ion‐rich domains.
Small‐angle scattering analysis of hard‐microdomain structure and microphase mixing in polyurethane elastomers
Authors: Leung Louis M. , Koberstein Jeffrey T.
Published: April 2003

The microdomain structure of a series of segmented polyurethane block copolymers is characterized by small‐angle x‐ray and neutron scattering analyses. The materials contain hard segments formed from 4,4′‐ diphenylmethane diisocyanate (MDI) and butanediol (BD), and range in hard‐segment content from 20 to 80% by weight. The results provide evidence for a transition from discrete to continuous hard‐microdomain morphology as the hard‐segment content is increased above ca. 50%. The measured concentration dependences of the interdomain spacing, specific interfacial area, diffuse microphase boundary thickness, and scattering invariants are used to examine the validity of present models for hard‐microdomain structure. The observed behavior corresponds well with the general predictions of a lamellar model wherein partially coiled hard‐segment sequence configurations are allowed. The thickness of the hard microdomains extracted from the model corresponds to approximately four hard‐segment repeat units. Scattering invariant calculations are used together with determinations of the soft‐microphase glass transition temperatures to examine possible models for microdomain mixing. These calculations suggest that both the hard and soft microphases are phase mixed.
Extraction and sorption studies using linear polymer chains and model networks
Authors: Garrido L. , Mark J. E.
Published: April 2003

Model networks have been prepared by tetrafunctionally endlinking linear polydimethylsiloxane (PDMS) chains having molecular weights Mn in the range 2000–15,000 g mole−1. The first series of networks were prepared from mixtures containing known amounts of unreactive linear PDMS chains with molecular weights Md between 1000 and 16,000 g mole−1. Rates of extraction were used to estimate diffusion coefficients; as expected, they were found to increase with increase in molecular weight Mc = Mn between crosslinks, but to decrease with increase in Md. The ease with which all of such a diluent could be removed showed the same dependence on Mc and Md. A second series of networks was prepared from the same reactive PDMS chains without diluents. Sorption and extraction studies using the same diluents were then carried out. The diffusion coefficients for sorption were found to be in the range (1.7–15.0) × 10−12 m2 s−1 and depended on both Mc and Md. The amount of diluent absorbed at equilibrium was between 10 and 70%, which is in good agreement with predictions from the Flory equation for dilation in networks, with account of constraints on crosslink fluctuations.
Phase separation phenomena in solutions of poly(2,6‐dimethyl‐1,4‐phenyleneoxide) in mixtures of trichloroethylene, 1‐octanol, and methanol: Relationship to membrane formation
Authors: Wijmans J. G. , Rutten H. J. J. , Smolders C. A.
Published: April 2003

The phase boundaries in the quaternary system consisting of the polymer poly(2,6‐dimethyl‐1,4‐phenyleneoxide) (PPO

PPO is a registered trademark of the General Electric Company.

), the solvent trichloroethylene (TCE), and the nonsolvents 1‐octanol (OcOH) and methanol (MeOH) are determined. The kinetics of crystallization are investigated by pulse‐induced critical scattering. The formation and properties of PPO membranes are discussed in relation to the phase separation phenomena.
Evidence for sorption–desorption phenomena during thermal cycling in highly hydrated perfluorinated membranes
Authors: Pineri M. , Volino F. , Escoubes M.
Published: April 2003

Perfluorinated ionomer membranes can absorb large amounts of water. DSC experiments show the existence of exothermic or endothermic peaks for water contents larger than 8 wt % at room temperature in Nafion 1200 EW in the acid form. Changes in the number of mobile protons versus temperature have been measured by NMR spectroscopy. A desorption process with an activation energy of 6 kcal/mol is proposed during the sample cooling. Such an explanation quantitatively explains both the DSC and NMR results and is also consistent with the other results obtained from mechanical experiments, low‐temperature sorption isotherms, and ESR spectroscopy.
Determination of the geometric structure of three substituted polyacetylenes: Polymethylacetylene, polypentylacetylene, and poly(tbutylacetylene)
Authors: Leclerc Mario , Prud'homme Robert E. , Soum Alain , Fontanille Michel
Published: April 2003

The geometric structure of polymethylacetylene (PMA), polypentylacetylene (PPA), and poly(t‐butylacetylene) (PTA) was investigated by 1H NMR, 13C NMR, and IR spectroscopies. It was shown that both NMR techniques can be used to determine the trans isomer content of PPA and PTA, whereas the 1H NMR and IR methods can be used for PMA. A calibration curve was constructed by using the 965‐ and 720‐cm−1 bands of the IR spectrum of PPA, and could be used in future work for the same purpose if the samples had molecular weights similar to that of the one used in this study. The isomerization kinetics of PTA was investigated and cis→ trans activation energies of 88 and 121 kJ/mol were calculated in solution and in the solid state, respectively. Heat treatment of the PMA and PPA samples always leads to a cis→ trans isomerization with a 100% trans content under extreme conditions. Moreover, a cis→ trans isomerization of PTA was induced in CCl4, CDCl3, toluene, and benzene, but a trans→ cis isomerization was induced in decalin. The reversible isomerization of PTA covered a trans isomer concentration ranging form 25 to 60%.
Spectroscopic study of α‐ and β‐phase isotactic polypropylene and of atactic polypropylene in solution
Authors: Merajver Sofia D. , Wunder Stephanie L. , Wallace William
Published: April 2003

Raman spectroscopy is used to investigate the conformation and packing of isotactic crystalline α‐phase polypropylene compared with lower‐order β‐phase isotactic polypropylene and to study the solution behavior of atactic polypropylene. The high‐frequency region of the spectrum is analyzed in light of a normal‐mode calculation that takes into account the methyl‐group vibrations. This region is sensitive to both chain conformation and packing, and because of the high intensity of the methyl and methylene high‐frequency stretching modes, it can be used to probe small changes in intermolecular or intramolecular order. Differences in the thermal behavior between the two solid isotactic polypropylene samples are explained interms of packing defects which exist in the β‐phase form. In the solution study, we demonstrate that, for molecules in which bands sensitive to intermolecular interactions exist, as is the case of the methyl and methylene vibrations of polypropylene, spectroscopic techniques can be used to estimate the minimum overlap concentration.
The effect of spherulitic truncation on small‐angle light scattering
Authors: Tabar R. J. , Stein R. S. , Rose D. E.
Published: April 2003

The effects of spherulitic truncation on the Hv small‐angle light‐scattering (SALS) patterns are determined by computer simulation of spherulite nucleation and growth. The simulation is carried out for simultaneous and sporadic nucleation of two‐dimensional spherulites and simultaneous nucleation of three‐dimensional spherulites. The scattered intensity differences between truncated spherulites and round spherulites are determined as functions of the type of growth and the volume (or area) fraction of spherulites. Methods for the determination of certain geometrical characteristics of spherulites systems by SALS are developed. These characteristics include the volume (or area). fraction of spherulites, the average spherulite radius, and the average spherulite volume (or area). The results of this study are essential in the quantitative analysis of Hv SALS from spherulitic systems. The simulation process is readily extendable to the examination of other morphological phenomena by SALS.
Melting of water/poly(ethylene oxide) systems
Authors: Bogdanov B. , Mihailov M.
Published: April 2003

The transition temperatures of poly(ethylene oxide) (PEO)/water systems were studied over the temperature range from −90 to 110°C by differential scanning calorimetry. The composition of the systems and the average molecular weight of the PEO were varied over a wide range. The systems under study tend to supercool and become partially or completely glassy depending on the cooling rate, composition, and PEO molecular weight. The glassy phases crystallize on being heated above their glass transition temperature. Systems containing about 60 wt % of PEO are most readily super cooled without crystallization. The dependence of melting temperatures and enthalpies on composition was studied and their isobar phase diagrams were drawn. They show that at a definite polymer content (about 50 wt %), which is molecular weight dependent, the systems behave as binary eutectic mixtures. The results confirm the idea that PEO forms quite stable molecular complexes with water.
Glass and subglass transitions in a series of poly(itaconate ester)s with methyl‐terminated poly(ethylene oxide) side chains
Authors: Cowie John M. G. , Ferguson Roderick
Published: April 2003

A series of poly(itaconate ester)s containing methyl‐terminated poly(ethylene oxide) side chains with lengths ranging from 1 to 5 ethylene oxide units has been synthesized. Both heat capacity Cp and dynamic mechanical measurements have been carried out on these polymers using differential scanning calorimetry (DSC) and torsional braid analysis (TBA), respectively. The resulting data for this polymer series are discussed, and comparisons are made with work previously published for the corresponding di‐n‐alkyl itaconate ester polymers where appropriate.
Electron‐beam‐induced fracture of polymers
Authors: Dickinson J. T. , Klakken M. L. , Miles M. H. , Jensen L. C.
Published: April 2003

When a notched polymeric material is stressed, the notch opens into a wide crack tip, exposing a region of high stress concentration. The consequences of electron bombardment of the tip of such a stressed material under vacuum are explored here for the first time. Evidence is presented for electron‐induced crack growth at stress far below that needed for crack growth due to stress alone. The electron current densities used in these experiments are sufficiently small that thermal heating of the zone near the crack tip is minimal. To provide information on the phenomena involved, we present simultaneous measurements of electron current, gas pressure, and sample load in response to periodic bombardment of the sample. Experiments involving the bombardment of un‐notched polymers under stress are also described. Fractography of the unique structures obtained by fracture due to the combination of electron bombardment and stress are presented and interpreted in terms of a crosslinking mechanism.
The application of gas barrier and thermal expansion techniques to study structural changes on annealing
Authors: Holden P. S. , Orchard G. A. J. , Ward I. M.
Published: April 2003

Changes occur in the structure of drawn polyethylene when it is annealed at temperatures close to that of the drawing process. Measurements have been made of the oxygen barrier properties and of the thermal expansion coefficient in the draw direction on samples over a wide draw ratio range both before and after annealing at various temperatures. The results are augmented by density, creep modulus, and shrinkage observations. All samples show a drop in the barrier properties and an increase in the thermal expansion after annealing. However, whereas high‐draw‐ratio samples show relatively small effects, the changes observed at low draw ratios are very large, with some barrier properties even lower than those of the isotropic feedstock. The effects are larger at the higher annealing temperatures. The diffusion and expansion measurements are greatly influenced by the amorphous regions in the polymer; these results are interpreted as a relaxation of internal stresses giving rise to greater accessibility of the intercrystalline regions. Further experimental work is required to exploit these techniques.
Spectroscopic analysis of poly(p‐phenylene benzobisthiazole) films
Authors: Chang Chih , Hsu S. L.
Published: April 2003

Infrared spectroscopy has been used to determine the relative amount, location, and orientation of residual water and acid molecules in poly(p‐phenylene benzobisthiazole) films. By analyzing the relative absorbance of reflected polarized infrared radiation from highly oriented films, the indices of refraction parallel and perpendicular to the chain axis were also obtained.
Polydimethylsiloxane–polyurethane elastomers: Synthesis and properties of segmented copolymers and related zwitterionomers
Authors: Xue‐Hai Yu , Nagarajan M. R. , Grasel T. G. , Gibson P. E. , Cooper S. L.
Published: April 2003

A series of polyurethane block polymers based on hydroxybutyl‐terminated polydimethyl‐siloxane soft segments of molecular weight 2000 were synthesized. The hard segments consisted of 4,4′‐methylenediphenylene diisocyanate (MDI) which was chain extended with either 1,4‐butanediol (BD) or N‐methyldiethanolamine (MDEA). The MDEA‐extended materials were ionized by using 1,3‐propane sultone. The weight fraction of hard segments was in the range 0.13–0.39. The morphology and properties of these polyurethane elastomers were studied by a variety of techniques. All of these short‐segment block copolymers showed nearly complete phase separation. The zwitterionomer materials exhibited ionic aggregation within the hard domains. Hard‐segment crystallinity or ionic aggregation did not affect the morphology. Hard‐domain cohesion was found to be a more important factor than hard‐domain volume fraction in determining the tensile and viscoelastic properties of these elastomers.
Polyethylene fiber formation in tubular flow. I. Observations of growth pattern and fiber properties
Authors: Rietveld J. , Mchugh A. J.
Published: April 2003

The process of seeded growth of fibrillar polyethylene crystals has been studied in a tubular flow geometry for 0.01‐wt % solutions of a high‐molecular‐weight polyethylene in xylene. The transformation sequence has been followed visually by using polarized‐light illumination in conjunction with a video camera. Data are presented to show that transformation is initiated by the formation of a concentrated, unoriented, amorphous precursor fiber within which oriented birefringent crystals subsequently grow in consequence of the stresses transmitted by the flowing solution. Time constants for the precursor formation, birefringence initiation, and completion of birefringence were measured as functions of temperature and flow rate over a range of growth conditions. Wide‐angle x‐ray diffraction, overall birefringence, and optical hot‐stage melting data were also obtained on the grown fibers. The net result of these observations is to conclude that fibrillar crystal growth during flow is always preceded by the formation of a liquidlike phase transformation which produces the concentrated, unoriented precursor. Subsequent orientation is in consequence of stress‐induced crystallization with overall fiber orientation showing an increase with solution flow rate at a fixed temperature and a decrease with temperature at a fixed flow rate. At higher temperatures and lower flow rates, birefringence develops in an oscillatory fashion, indicating a remelting process possibly due to slippage of trapped chain entanglements formed by flow. A discussion is given of the implications of these observations for the understanding of flow‐induced structure development, phase transformation, and oriented crystallization; this is expanded upon in a companion paper, Part II.
Estimation of the equilibrium modulus of rubber networks by nonlinear regression analysis
Authors: Scholtens Boudewijn J. R. , Hillegers L. Tom
Published: April 2003

A nonlinear regression analysis is presented to estimate the equilibrium modulus of relaxing rubber networks from G'(ω) or G(t) data. Various semiempirical curve‐fitting equations are tested with two‐function minimization algorithms.
Small‐angle light scattering from a distribution of spherulite sizes
Authors: Wissler G. E. , Crist B.
Published: April 2003

Depolarized small‐angle light scattering from spherulites in semicrystalline polymers gives rise to a characteristic cloverleaf pattern. For scattering from a single spherulite, the position of the maximum in scattered intensity is readily related to the spherulite radius. For a distribution of spherulites, the maximum should be related to some characteristic measure of the distribution. It is shown for a wide variety of distributions that this characteristic radius is a ratio of high moments of the size distribution, specifically R* ≈ 〈R7〉/〈R6〉. The shape of the light‐scattering profile should in principal be related to the nature of the spherulite distribution. Calculations of scattering profiles from a variety of distributions fail to demonstrate this, owing to the strong dependence of scattering power on spherulite size. Exceptions are noted for the case of certain bimodal distributions.
Temperature dependence of the crystal structures of nylon 11
Authors: Kim K. G. , Newman B. A. , Scheinbeim J. I.
Published: April 2003

Careful examination of x‐ray diffraction patterns from melt‐crystallized nylon 11 films show significant discrepancies with the proposed α‐form structure. These discrepancies do not disappear after the samples have been annealed. The temperature dependence of the d spacings of the two strongest peaks show further evidence that the melt‐crystallized and solution‐cast films (α form) possess different crystal structures. These results suggest a different crystal structure for the melt‐crystallized films; this would help explain the rather low piezoelectric response of these films and also the failure to observe a rapid decrease in polarization at the transition temperature.
The influence of morphology on the dielectric and dynamic mechanical behavior of a linear low‐density polyethylene
Authors: Jang Y. T. , Parikh D. , Phillips P. J.
Published: April 2003

The dielectric and viscoelastic relaxation behavior of linear low‐density polyethylene has been investigated. All three usual relaxation regions occur; however, the α process is more dominant than in conventional low‐density polyethylene made dielectrically active through the introduction of carbonyl groups. The observed behavior is very sensitive to orientation and morphology. There are significant differences between oriented samples (stretching or extrusion) and a single‐crystal texture specimen. Effects are caused by dipolar orientation and dipolar immobilization, the relative importance of each effect varying with specimen preparation. Active dipolar groups are not carbonyls, or any common organic species, but appear to be due to chain ends having residual dipoles caused by the catalyst used in synthesis.
Crazing as quasifracture in an oriented viscoelastic medium
Authors: Chern S. S. , Zhang Z. D. , Hsiao C. C.
Published: April 2003

Crazes of different types occur in polymeric systems. Long, sparse crazes develop in less oriented molecular systems, while fine, short, dense crazes occur in highly oriented molecular systems. Different crazing mechanisms and different models may have to be studied for a better understanding of these differences. However, in this report, using one model and one theory, an analysis has been made of the differences in the geometry of craze development. By emphasizing the mechanism of molecular orientation, it is found that the basic differences are essentially attributable to the variation of the anisotropy of the material system as a result of large deformation rather than to any fundamental differences in the crazing mechanism.
Studies on comblike polymers. X. Characterization of comblike polyesters by 13C NMR spectroscopy
Authors: Segre Anna Laura , Andruzzi Fulvio , Barone Corrado , Paci Massimo , Magagnini Pier Luigi
Published: April 2003

The 13C NMR spectra of aromatic comblike polyesters obtained from 1,2‐icosanediol and isomeric phthalic acids are reported and discussed. The analysis shows that the most informative spectral regions are those of the carbonyl and quaternary carbon resonances, whose peak multiplicities have been interpreted in terms of dyad and triad sequences. The results indicate that the extent of structural characterization possible for the polymers examined is dependent on the type of isomerism of the aromatic acid involved.
Estimating correlation by using a general linear mixed model: evaluation of the relationship between the concentration of HIV‐1 RNA in blood and semen
Authors: Chakraborty Hrishikesh , Helms Ronald W. , Sen Pranab K. , Cohen Myron S.
Published: April 2003

Estimating the correlation coefficient between two outcome variables is one of the most important aspects of epidemiological and clinical research. A simple Pearson's correlation coefficient method is usually employed when there are complete independent data points for both outcome variables. However, researchers often deal with correlated observations in a longitudinal setting with missing values where a simple Pearson's correlation coefficient method cannot be used. General linear mixed models (GLMM) techniques were used to estimate correlation coefficients in a longitudinal data set with missing values. A random regression mixed model with unstructured covariance matrix was employed to estimate correlation coefficients between concentrations of HIV‐1 RNA in blood and seminal plasma. The effects of CD4 count and antiretroviral therapy were also examined. We used data sets from three different centres (650 samples from 238 patients) where blood and seminal plasma HIV‐1 RNA concentrations were collected from patients; 137 samples from 90 different patients without antiviral therapy and 513 samples from 148 patients receiving therapy were considered for analysis. We found no significant correlation between blood and semen HIV‐1 RNA concentration in the absence of antiviral therapy. However, a moderate correlation between blood and semen HIV‐1 RNA was observed among subjects with lower CD4 counts receiving therapy. Our findings confirm and extend the idea that the concentrations of HIV‐1 in semen often differ from the HIV‐1 concentration in blood. Antiretroviral therapy administered to subjects with low CD4 counts result in sufficient concomitant reduction of HIV‐1 in blood and semen so as to improve the correlation between these compartments. These results have important implications for studies related to the sexual transmission of HIV, and development of HIV prevention strategies. Copyright © 2003 John Wiley & Sons, Ltd.
From single‐race reporting to multiple‐race reporting: using imputation methods to bridge the transition
Authors: Schenker Nathaniel , Parker Jennifer D.
Published: April 2003

In 1997, the Office of Management and Budget issued revised standards for the collection of race information within the Federal statistical system. One revision allows individuals to choose more than one race group when responding to Federal surveys and other Federal data collections. This paper explores methods that impute single‐race categories for those who have given multiple‐race responses. Such imputations would be useful when it is desired to conduct analyses involving only single‐race categories, such as when trends over time are being examined by race group so that data collected under the old and new standards are being combined. The National Health Interview Survey has allowed multiple‐race responses for several years, while also asking respondents to specify one race as their primary race. Exploratory analyses of data from the survey suggest that imputation methods that use demographic and contextual covariate information to predict primary race can have advantages with respect to lower bias and improved variance estimation compared to simpler methods discussed by the Office of Management and Budget. It also appears, however, that the relationships between primary race and covariates might be changing over time. Thus, caution should be exercised if an imputation model fitted to data from one time period is to be applied to data from another time period. Published in 2003 by John Wiley & Sons, Ltd.
Adjustments for non‐telephone bias in random‐digit‐dialling surveys
Authors: Frankel Martin R. , Srinath K.P. , Hoaglin David C. , Battaglia Michael P. , Smith Philip J. , Wright Robert A. , Khare Meena
Published: April 2003

Telephone surveys are widely used in the U.S.A. for the study of health‐related topics. They are subject to ‘coverage bias’ because they cannot sample households that do not have telephones. Although only around 5 per cent of households do not have a telephone, rates of telephone coverage show substantial variation by geography, demographic factors and socio‐economic factors. In particular, lack of telephone service is more common among households that contain ethnic and racial minorities or that have lower socio‐economic status with fewer opportunities for access to medical care and poorer health outcomes. Thus, failure to adequately account for households without telephones in health surveys may yield estimates of health outcomes that are misleading, particularly in states with at least moderate telephone non‐coverage. The dynamic nature of the population of households without telephones offers a way of accounting for such households in telephone surveys. At any given time the population of telephone households includes households that have had a break or interruption in telephone service. Empirical results strongly suggest that these households are very similar to households that have never had telephone service. Thus, sampled households that report having had an interruption in telephone service may be used also to represent the portion of the population that has never had telephone service. This strategy can lead to a reduction in non‐coverage bias in random‐digit‐dialling surveys. This paper presents two methods of adjusting for non‐coverage of non‐telephone households. The effectiveness of these methods is examined using data from the National Health Interview Survey. The interruption‐in‐telephone‐service methods reduce non‐coverage bias and can also result in a lower mean squared error. The application of the interruption‐in‐telephone‐service methods to the National Immunization Survey is also discussed. This survey produces estimates for the 50 states and 28 urban areas. The interruption‐in‐telephone‐service estimates tend be slightly lower than estimates resulting from poststratification and from another non‐coverage adjustment method. The results suggest that the reduction in bias is greatest for variables that are highly correlated with the presence or absence of telephone service. Published in 2003 by John Wiley & Sons, Ltd.
Die Soziale-Erwünschtheits-Skala-17 (SES-17): Entwicklung und erste Befunde zu Reliabilität und Validität
Authors: Stöber Joachim
Published: April 2003

Zusammenfassung. Die “Social Desirability Scale” von Crowne und Marlowe (1960) , SDS-CM, erfreut sich nach wie vor großer Beliebtheit. Dasselbe gilt für die deutsche Fassung ( Lück & Timaeus, 1969 ). Nach 40 Jahren ist es jedoch fraglich, ob die SDS-CM noch zeitgemäß ist bzw. ob sich nicht neue Items finden lassen, die einen höheren Grad an sozialer Erwünschtheit aufweisen. Vier Studien werden beschrieben, in denen eine neue Skala im Stil der Crowne-Marlowe-Skala entwickelt und überprüft wird. Das Ergebnis ist die Soziale-Erwünschtheits-Skala-17 (SES-17). Diese umfaßt 17 Items. Reliabilität und konvergente Validität sind zufriedenstellend: Die interne Konsistenz liegt bei .72 bis .75, die Retest-Stabilität über vier Wochen bei .82 und die Korrelation mit der SDS-CM bei .67 bis .74. Damit ist die SES-17 ein der SDS-CM vergleichbares Verfahren, ist jedoch ökonomischer (17 statt 23 Items) und zeigt höhere Augenscheinvalidität: Eine Stichprobe von 49 Beurteilern schätzte die Items beider Skalen bezüglich sozialer Erwünschtheit ein. Die SES-17-Items erhielten signifikant und bedeutsam höhere Ratings als die SDS-CM-Items.
Redeängstlichkeit:Entwicklung eines mehrdimensionalen Verfahrens
Authors: Spitznagel Albert , Schlutt Stefan , Schmidt-Atzert Lothar
Published: April 2003

Zusammenfassung. Ein Fragebogen wurde entwickelt, der habituelle zeitliche Verläufe der emotionalen und kognitiven Komponente der Angst anläßlich einer Rede erfassen soll. In zwei Untersuchungen mit Studierenden (N = 294 und 159) wurden aufgrund von Faktorenanalysen für jeden der relevanten vier Zeitpunkte (Tage vor, unmittelbar vor, während und nach einer Rede) jeweils acht Items zur Emotionalität und acht zur Besorgtheit ausgewählt. Die resultierenden acht Skalen hatten eine hohe interne Konsistenz (alpha = .80 bis .92). Zwei weitere Untersuchungen (N = 164 und 56) ergaben u.a., daß die beiden globalen Skalen zur Emotionalität und Besorgtheit noch hinreichend spezifische Varianz aufweisen (r = .71). Zwischen den Subskalen zur Emotionalität wurden moderate Korrelationen (r = .52) gefunden. Die Besorgtheitskomponente erwies sich dagegen als weitgehend invariant über die Zeitpunkte hinweg (r = .76; N jeweils 164). Mit Hilfe einer Konfigurationsclusteranalyse konnten Subpopulationen mit unterschiedlichen “Verläufen” der Emotionalität identifiziert werden. Insgesamt sprechen die Ergebnisse dafür, daß mit dem Verfahren kognizierte Verläufe der emotionalen Komponente der Redeängstlichkeit sowie das globale Ausmaß an redebezogener Besorgtheit erfaßt werden können.
Entwicklung und Konstruktvalidierung eines berufsbezogenen Leistungsmotivationstests
Authors: Schuler Heinz , Prochaska Michael
Published: April 2003

Zusammenfassung. Es wird die Entwicklung und Konstruktvalidierung des Leistungsmotivationsinventars (LMI; Schuler & Prochaska, 2000 ) beschrieben. Dem Verfahren liegt ein weites Verständnis von Leistungsmotivation zugrunde, demzufolge Leistungsmotivation als globale Verhaltensorientierung verstanden wird. Das Verfahren ermöglicht mit 17 Skalen die differenzierte Beschreibung der Leistungsmotivation. An N = 1985 Personen wurden ergänzende Charakteristika und Außenkriterien erhoben. Im Vergleich mit dem Fünf-Faktoren-Modell der Persönlichkeit resultieren erwartungsgemäß die engsten Beziehungen zu Neurotizismus und Gewissenhaftigkeit. Weitere Konstruktzusammenhänge konnten mit schul-, studien- und berufsbezogenen Kriterien ermittelt werden, auch mit der Übernahme von Funktionen wie Führungsaufgaben. Im Rahmen eines Potentialanalyseverfahrens wurden mäßige Korrelationen mit interaktiven Diagnoseverfahren und keine mit kognitiv betonten Verfahren ermittelt. Deutliche Beziehungen resultierten zum Interesse für berufliche Tätigkeitsfelder. Die Ergebnisse lassen erwarten, daß das LMI in der persönlichkeitspsychologischen Forschung und in der Berufseignungsdiagnostik Anwendung mit Aussicht auf inkrementelle Validität finden kann.
Organizational Citizenship Behavior: Entwicklung und erste Validierung eines Meßinstruments
Authors: Staufenbiel Thomas , Hartz Christopher
Published: April 2003

Zusammenfassung. Gegenstand ist die Konstruktion und Validierung eines deutschsprachigen Fragebogens zur Erfassung des Konstrukts Organizational Citizenship Behavior (OCB). OCB bezeichnet nach Organ (1988) Verhalten, das zur Produktivität einer Organisation beiträgt, dessen Ausführung aber, da formal nicht vorgeschrieben, im Ermessen der Mitarbeiter liegt. Ein in Anlehnung an amerikanische Erhebungsinstrumente entwickelter Fragebogen bestätigt eine Differenzierung in die OCB-Subskalen Hilfsbereitschaft, Gewissenhaftigkeit, Unkompliziertheit und Eigeninitiative. Lediglich für die Skala Rücksichtnahme findet sich keine empirische Evidenz. Im Sinne der diskriminanten Validität lassen sich die vier OCB-Faktoren empirisch von dem geforderten Arbeitsverhalten abgrenzen. Erste Anhaltspunkte zur Konstruktvalidität ergeben sich aus der Bestätigung von Zusammenhängen mit soziodemographischen Variablen sowie positiven Korrelationen mit der Arbeitszufriedenheit und dem affektiven Commitment in einer unabhängigen Studie.
Differentielle Latenzzeiteffekte bei der Bearbeitung von Reasoning-Items
Authors: Beckmann Jens F.
Published: April 2003

Zusammenfassung. Analysiert wird das Latenzzeitverhalten bei der Beantwortung von Items in nicht zeitbegrenzt dargebotenen Intelligenztests. Bisherige Befunde zeigen, daß falsche Antworten später gegeben werden als korrekte. Dieses “Falsch > Richtig-Phänomen” wird sowohl hinsichtlich seiner Generalität als auch hinsichtlich seiner Universalität an einer Stichprobe von insgesamt N = 169 Schülern (mittleres Alter 14;6 Jahre) untersucht. Die Testanden bearbeiteten einen Figurenfolgen-, einen Zahlenfolgen-Test und einen Test mit verbalen Analogien. Das “Falsch > Richtig-Phänomen” konnte repliziert werden (Generalität). Die Differenz zwischen Falsch- und Richtig-Latenz nimmt jedoch mit sinkender Testleistung ab (eingeschränkte Universalität). Der Nachweis einer transsituativen Konsistenz des Latenzzeitverhaltens und die lediglich moderaten positiven korrelativen Beziehungen der Latenzzeit zur Testleistung legt die Erwartung eines potentiell zusätzlichen diagnostisch relevanten Indikators nahe. Die Interpretation der Ergebnisse zeigt, daß kognitive Stilbesonderheiten (kognitive Impulsivität) nicht zur Erklärung der differentiellen Latenzzeitunterschiede zwischen verschiedenen Leistungsgruppen herangezogen werden können.
Entwicklung eines Fragebogens zur Vorbereitung von Senioren auf einen zukünftigen Pflegebedarf (FVP):
Authors: Pinquart Martin , Sörensen Silvia
Published: April 2003

Zusammenfassung. Ausgehend von der Annahme, daß eine Vorbereitung auf künftige Stressoren deren Bewältigung unterstützen kann, wurde ein Fragebogen zur Vorbereitung auf einen zukünftigen Hilfs- und Pflegebedarf (FVP) entwickelt. Der Fragebogen umfaßt drei Teile, a) Erwartungen über die Nützlichkeit des Vorausplanens und zum wahrgenommenen Risiko, künftig Hilfe oder Pflege zu benötigen, b) Prozesse der Vorbereitung (Gewahr werden des Pflegerisikos, Informationsvermeidung, Sammeln von Informationen über Pflegeoptionen, Präferenzen bilden, Aktivitäten zur Realisierung der Pläne, Zufriedenheit mit bisherigen Aktivitäten zur Vorbereitung) sowie c) Planinhalte (getrennt für einen vorübergehenden und langzeitigen Pflegebedarf). Befunde zur Validität der Skalen werden für 574 Senioren (65-93 Jahre) berichtet. So geht z.B. eine erhöhte Vulnerabilität, in Zukunft Hilfe oder Pflege zu brauchen, mit mehr Vorausplanen einher. Zudem bestehen Zusammenhänge zur internalen Kontrollüberzeugung und zu habituellen Entscheidungsstilen. Daten zur Stabilität der Skalen wurden an einer Teilstichprobe von 103 Senioren gewonnen.
Symptom-Checkliste SCL-90-R:
Authors: Hessel Aike , Schumacher Jörg , Geyer Michael , Brähler Elmar
Published: April 2003

Zusammenfassung.Die Symptom-Checkliste SCL-90-R ist ein weltweit sehr häufig eingesetztes Selbstbeurteilungsinstrument zur Erfassung der psychischen Symptombelastung. In der vorliegenden Arbeit wird über die testtheoretische Überprüfung des Verfahrens und die bisher noch fehlende Normierung an einer für die deutsche Bevölkerung repräsentativen Stichprobe von 2179 Personen im Altersbereich von 16 bis 96 Jahren berichtet. Es konnte gezeigt werden, dass die SCL-90-R als Gesamtskala ein reliables Instrument zur Messung der globalen psychischen Symptombelastung darstellt. Die von den Autoren des Verfahrens postulierte dimensionale Struktur mit neun Skalen zur Erfassung unterschiedlicher Symptombereiche lässt sich faktorenanalytisch jedoch nicht bestätigen. Sowohl die hohen Interkorrelationen der Skalen als auch der Eigenwerteverlauf der Faktorenanalyse legt die Existenz eines varianzstarken Generalfaktors (global distress factor) nahe, der die allgemeine Symptombelastung einer Person abbildet. Eine valide Erfassung voneinander abgrenzbarer Symptombereiche mittels verschiedener Subskalen ist mit der SCL-90-R somit nicht möglich. Die mitgeteilten Normwerte beziehen sich deshalb lediglich auf die globalen Skalenkennwerte.
Screening psychischer Belastungen in der stationären Krankenpflege (Belastungsscreening TAA-KH-S)
Authors: Büssing André , Glaser Jürgen , Höge Thomas
Published: April 2003

Zusammenfassung. Der Beitrag dokumentiert die Entwicklung und empirische Erprobung des Screenings psychischer Belastungen in der stationären Krankenpflege (Belastungsscreening TAA-KH-S). Es handelt sich um ein bedingungsbezogenes Selbstbeobachtungsverfahren zur Arbeitsanalyse im stationären Pflegedienst. Die Reliabilität des Instruments wird zum einen anhand der internen Konsistenz der Skalen, zum anderen im Hinblick auf die Beurteilerübereinstimmung mittels Intraklassenkorrelation überprüft. Zur Prüfung der Konstruktvalidität werden Zusammenhänge zwischen den Ergebnissen des Belastungsscreenings und konvergenten Kriterien der Arbeits(un)zufriedenheit und der psychophysischen Beanspruchung ermittelt. Darüber hinaus wird ein exemplarischer Vergleich von Ergebnissen des Belastungsscreenings mit Resultaten aus Fremdbeobachtungen vorgenommen, die im Rahmen von Ganzschichtbeobachtungen ermittelt wurden. Die Ergebnisse einer Untersuchung mit 160 Krankenpflegekräften aus zwei Krankenhäusern der Maximalversorgung und der Regelversorgung belegen die Reliabilität und Validität des Verfahrens.
Testgüte und psychometrische Äquivalenz der deutschen Version des Big Five Inventory (BFI) bei jungen, mittelalten und alten Erwachsenen
Authors: Lang Frieder R. , Lüdtke Oliver , Asendorpf Jens B.
Published: April 2003

Zusammenfassung. In einer Studie mit 480 jungen, mittelalten und alten Erwachsenen wurde eine deutsche Version des “Big Five Inventory (BFI)“ eingesetzt. Es wurde die Äquivalenz der faktoriellen Struktur in den Altersgruppen sowie die Kriteriumsvalidität in Bezug auf 6 Außenkriterien überprüft (Intelligenz, positiver und negativer Affekt, Kontrollerleben, soziale Zufriedenheit und Netzwerkgröße). Die Stichprobe beruht auf einer nach Alter und Geschlecht geschichteten Wahrscheinlichkeitsauswahl aus dem Berliner Melderegister. Die Befunde weisen auf eine Invarianz der Faktorenstruktur in den Altersgruppen hin. Es zeigten sich erwartungskonforme und altersinvariante Korrelationen der 5 Persönlichkeitskonstrukte Extraversion, Verträglichkeit, Gewissenhaftigkeit, Neurotizismus und Offenheit für Erfahrung mit den Außenkriterien. In einer Studie mit 45 sehr alten Erwachsenen zeigten sich moderate bis hohe Retest-Stabilitäten über einen Zeitraum von 5 Monaten. Insgesamt erweist sich der BFI als leicht einsetzbares Instrument zur reliablen Erfassung des Fünf-Faktoren-Modells.
Editorial
Authors: Leutner Detlev
Published: April 2003

Zusammenfassung. Die Diagnostica bedient auch weiterhin die gesamte fachliche Breite der Psychologie und wird somit auch weiterhin ihrem Anspruch gerecht, Organ für diagnostische Fragen in allen Bereichen der Psychologie zu sein. Mit einer Ablehnungsquote von 68% und einem aktuellen Impact-Faktor von 2.07 kann sich die Diagnostica auch weiterhin als führende deutschsprachige Zeitschrift des Feldes gut sehen lassen. Der vor einer ganzen Reihe von Jahren angetretene Herausgeberkreis unterliegt jedoch einigen Veränderungen.