bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural Basis for Recognition of Guanosine by a Synthetic Tricyclic Cytosine Analogue: Guanidinium G‐Clamp
Authors: Wilds Christopher J. , Maier Martin A. , Manoharan Muthiah , Egli Martin 
Published: April 2003

AbstractAn oligonucleotide analogue containing a novel heterocyclic analogue, the guanidinium G‐clamp, was designed to allow formation of five H‐bonds to guanosine. The guanidinium group was introduced postsynthetically by treatment of the deprotected oligonucleotide containing a free amino group with a solution of 1H‐pyrazole‐1‐carboxamidine and purified by a combination of size‐exclusion chromatography and reversed‐phase HPLC. A single incorporation of this modification into an oligodeoxynucleotide sequence was found to increase duplex stability by 13° and 16° per modification to RNA and DNA, respectively. Crystals of a self‐complementary decamer sequence containing this modification were grown and diffracted to 1‐Å resolution. The structure was solved by molecular replacement and revealed that the modification forms additional H‐bonds to O(6) and N(7) of guanosine through the amino and imino N‐atoms, respectively. The origins of enhanced duplex stability are also attributed to increased stacking interactions mediated by the phenoxazine moiety of the G‐clamp and formation of H‐bond networks between the positively charged guanidinium group, H2O molecules, and negatively charged O‐atoms from phosphates on the adjacent strand.
Predicting disturbed parental awareness in mothers with a newborn infant: test of a theoretical model
Authors: Grietens Hans , Hellinckx Walter 
Published: April 2003

AbstractParental awareness refers to parents' perceptions and making sense out of children's responses and behaviours. This study examined a theoretical model on the determinants of disturbed parental awareness, with a central place given to Belsky's buffer hypothesis. Maternal characteristics were hypothesized to have direct effects on parental awareness, whereas effects of negative childhood experiences and low levels of social support were regarded as being mediated by maternal characteristics. The model was examined in a community sample of 101 mothers from different socioeconomic backgrounds with a zero‐to‐three infant. Social nurses providing home visits reported on parental awareness, childhood experiences, social support, and maternal characteristics. Results supported a modified model that added a direct pathway between childhood experiences and parental awareness, supporting the intergenerational transmission hypothesis. Copyright © 2002 John Wiley & Sons, Ltd.
Maternal speech style with prelinguistic twin infants
Authors: Butler Sue , McMahon Catherine , Ungerer Judy A. 
Published: April 2003

AbstractThe mother–infant communicative speech of a group of mothers of 4‐month‐old first‐born twin infants was compared to the speech of a group of mothers of first‐born singleton infants. Maternal groups were matched on age, education level, mother–infant attachment status and infant gender, and maternal depression was assessed as a control variable. Maternal speech was coded for focus, content, complexity and syntax of mothers' utterances. The findings of earlier studies with toddler age twins, that maternal speech style was more directive and less infant‐focused, were replicated in this prelinguistic period of infancy. Compared to mothers of singletons, mothers of twins used less infant‐focused speech, were less responsive to their infants' cues, and attributed less agency to their infants. Mothers of twins also used fewer questions and requests but did not differ from mothers of singletons in their use of negatives and imperatives. These early differences in the language learning environments of twin and singleton infants may be due to the reduced opportunities that mothers of twins have to establish dyadic communicative routines with their infants and to familiarize themselves with their infants as interactive partners, and may have implications for the early language development of twins. Copyright © 2002 John Wiley & Sons, Ltd.
Chemoenzymatic Synthesis of Fucose‐ or Rhamnose‐Branched Polymer
Authors: Raku Takao , Tokiwa Yutaka 
Published: April 2003

Abstract6‐Deoxy sugars having only secondary alcohols, namely, D‐fucose, L‐fucose, and L‐rhamnose, were regioselectively esterified with divinyl adipate by enzymes. The compounds 2‐O‐vinyl adipolyl D‐fucose and 2‐O‐vinyl adipolyl L‐fucose were effectively produced in dimethylformamide by protease from Bacillus subtilis and Streptomyces griseus. Furthermore, 4‐O‐vinyl adipolyl L‐rhamnose was effectively produced in pyridine by lipase from Pseudomonas sp. Each polymerizable sugar ester was polymerized by 1,1′‐azoisobutyronitrile to give polymers having a number average molecular weight of 5 000–14 000.
Part of the chemoenzymatic synthesis of poly(6‐deoxy sugars).magnified imagePart of the chemoenzymatic synthesis of poly(6‐deoxy sugars).
Complexation reaction of poly(L‐glutamic acid) with Cu ions and the effect of helix‐coil transition of the polymer chain
Authors: Koide Mikio , Tsuchida Eishun , Kurimura Yoshimi 
Published: April 2003

AbstractThe complexation reaction of poly(L‐glutamic acid) (1), with Cu ions in aqueous solution was studied by pH titration, spectroscopy, circular dichroism measurements and solution viscosity. The adsorption of Cu ions depended on the secondary structure of 1; 1 adsorbed Cu ions when its degree of neutralization was higher than 0,6. Thus, this phenomenon was attributed to the helix‐coil transition of 1. It was cleared that the helical structure was retained because of chelating between Cu ions and carboxyl groups of the side chain of 1. The formation of the Cu/1 complex was compared with that of the Cu/poly(acrylic acid) complex (2).
13C NMR study on the mechanism of stereoselective polymerization of methyloxirane catalyzed by a model compound for enantiomorphic catalysts
Authors: Hagiwara Tokio , Ishimori Michihiro , Tsuruta Teiji 
Published: April 2003

AbstractThe reaction of [Zn(OCH3)2·(C2H5ZnOCH3)6] (1) with methyloxirane was investigated by 13C NMR spectroscopy. Complex 1 was assumed to be a model compound for enantiomorphic catalyst sites in the stereoselective polymerization of methyloxirane by organozinc catalyst. Complex 1 was found to retain its structural feature, determined by X‐ray diffraction, even after the propagation reaction had proceeded. Based on 13C NMR studies of the polymerization reaction in terms of spin‐lattice relaxation and signal intensity analysis, the mechanism of the stereoselective polymerization of methyloxirane by the chiral catalyst sites was discussed at molecular level in reference to the enantiomorphic structure of complex 1.
Mechanischer Scherabbau von Polymeren in Lösung mittels turbulenter Strömung, 2. Die Abhängigkeit der Abbaugeschwindigkeit von der Polymergesamtkonzentration in guten Lösungsmitteln
Authors: Müller Hans Georg , Klein Joachim , Rottloff Adelheid 
Published: April 2003

AbstractMechanical shear degradation of poly(decyl methacrylate), (viscosity average molecular weight in tetrahydrofuran M̄η = 1,3·106, M̄w/M̄n = 5) in the thermodynamically good solvent tetrahydrofuran has been studied in turbulent flow through a capillary as a function of polymer concentration in the range from 0,22 to 8,9 g/100 cm3. Due to turbulent flow conditions the shear stress, shear rate and shear energy proved to be the same for all concentrations and remained constant during degradation, giving a general insight into mechanism of degradation. The rate of degradation has been followed using molecular weight distribution curves obtained by gel permeation chromatography. The reaction was found to be of first order. Rate constants determined for molecular weights from 3,2–9,5·106 decreased with increasing concentration following a law of the type ki = (K + b·c)−1, K and b being constants for each molecular weight. Hydrodynamic volumes of polymer molecules have been calculated according to models of Rudin as function of molecular weight and concentration. It can be shown that rate constants of degradation and calculated hydrodynamic volumes are proportional for the whole range of molecular weight and concentrations up to 3,6 g/100 cm3. There is also a rather good proportionality between these rate constants and the volumes of polymer coils predicted by de Gennes. This result is an additional confirmation of the concept that hydrodynamic volume governs shear degradation of polymer solutions. Additional experiments show that this type of concentration dependence is also to be found for other polymers in other solvents.
Investigations on the Film‐Formation Process of Latex Dispersions by Solid‐State NMR Spectroscopy
Authors: Rottstegge Jörg , Traub Bernd , Wilhelm Manfred , Landfester Katharina , Heldmann Carsten , Spiess Hans Wolfgang 
Published: April 2003

AbstractVarious latex dispersions based on poly(vinyl acetate) stabilised by different surfactants and polyelectrolytes were investigated by NMR methods to elucidate the macroscopic and molecular film‐formation process of these latex dispersions. Macroscopically, theinhomogeneousdrying in the film‐formation process was investigated by NMR‐imaging techniques. Here the influence of different amounts of surfactant on the homogeneity of the drying process was monitored. The molecular film‐formation process was investigated by1H,2H, and13C solid‐state NMR spectroscopy. For these bulk measurements, films of latex dispersions werehomogeneouslydried to different defined solid contents. Spectroscopic analysis allows the investigation of the drying process of the water at different solid contents with a pronounced influence on the polymer/water interface and the latex particle core. The film‐formation process is correlated to the drying mechanism of different types of water within the film. External water, water at ionic and non‐ionic groups at surfactants in the polymer/water interface, and water in the swollen and mobilised polymer, could be distinguished during the drying process.Latex domains as selected by solid‐state NMR spectroscopy as a function of temperature.magnified imageLatex domains as selected by solid‐state NMR spectroscopy as a function of temperature.
Viscoelastic Properties of Polystyrene Nanocomposites Based on Layered Silicates
Authors: Meincke Olaf , Hoffmann Botho , Dietrich Christoph , Friedrich Christian 
Published: April 2003

AbstractNanocomposites based on polystyrene (PS) and organophilic layered silicates (organoclays) were prepared and characterised with respect to their morphological and rheological properties. The organoclays were obtained by means of ion exchange of clay with protonated, amine‐terminated PS. Two different exchange agents – a high (Mw = 5 800 g/mol) molecular mass amine functionalised PS, and 2‐phenylethylamine – were used to study the influence of their molecular weight on morphological and rheological properties of corresponding composites. Wide‐angle X‐ray scattering measurements show a significant increase in the interlayer spacing upon the ion exchange. Composites of organoclay prepared from the high molecular mass amine‐terminated PS and PS‐matrix polymer reveal a fine and stable dispersion of exfoliated silicate layers in the PS matrix if the compounding time in a conical twin screw extruder exceeds 180 s at a temperature of 200 °C. This composite, i.e. nanocomposite, shows unique elastic properties which can be understood quantitatively if one assumes that above a characteristic concentration of about 1 vol.‐% percolating strands of platelets are present in the material. Composites of PS and organoclay prepared from 2‐phenylethylamine did not exfoliate and consequently exhibited the rheological behaviour of a conventional composite. Qualitatively all morphological and rheological features of the PS nanocomposite can be entirely understood if one considers this material as a mixture of hairy platelets dispersed in an entangled PS matrix.
“Hairy platelets” model for exfoliation of layered silicates.magnified image“Hairy platelets” model for exfoliation of layered silicates.
Clathrate Phases of Styrene/p‐Methylstyrene co‐Syndiotactic Copolymers
Authors: Loffredo Fausta , Pranzo Annamaria , Venditto Vincenzo , Longo Pasquale , Guerra Gaetano 
Published: April 2003

AbstractThe possible formation of clathrate phases with several different guest molecules for co‐syndiotactic random copolymers of styrene and p‐methylstyrene has been investigated. In the presence of suitable guests, like carbon disulfide and tetrahydrofuran, clathrate phases are stable for the entire copolymer composition range. However, discontinuous changes between clathrates structurally similar to those observed for syndiotactic polystyrene and syndiotactic poly(p‐methylstyrene) have been observed by wide‐angle X‐ray diffraction and differential scanning calorimetry. Wide copolymer composition ranges of stability have been observed for carbon disulfide/syndiotactic polystyrene and for tetrahydrofuran/syndiotactic poly(p‐methylstyrene) clathrates. A phase diagram including clathrate and crystalline forms of this copolymer system has been presented.
Schematic presentation of along the chain (c axis) projection of packing of the clathrate form of syndiotactic polystyrene including carbon disulfide.magnified imageSchematic presentation of along the chain (c axis) projection of packing of the clathrate form of syndiotactic polystyrene including carbon disulfide.
A method of estimating the parameters in the Mark‐Houwink equation from molecular weight and second virial coefficient
Authors: Kawai Tōro , Kamide Kenji 
Published: April 2003

AbstractA new method has been proposed for estimating the parameters Km and a in the Mark‐Houwink equation [η] = KmM̄va from the measurements of molecular weight and second virial coefficient for a single polymer sample. Although the treatment has been based upon existing theories, the partly draining effect has been taken into account as well as the excluded volume effect. Only one sample need be used, and thus the usual more laborious method is unnecessary. General applicability of our method has been shown by several examples cited from published data.
Urea‐induced contraction–relaxation of rat tail tendons
Authors: Elden Harry R. , Cassac Betty 
Published: April 2003

AbstractA contraction and relaxation of rat tail tensons that can be induced by aqueous urea solutions is described in this report. Studies with 2–10M urea at pH 7.0 and 37°C. showed that the length–time curves could be divided into five periods: (1) lag period, (2) contraction, (3) point of maximum contraction, (4) relaxation, and finally (5) rupture. An empirical analysis of the rate showed that (dL/dt)c, the initial velocity of contraction. (dL/dt)r, the terminal velocity of relaxation, and dL/dt, the velocity at any time (t), could be related with a specific rate constant, Kcr, by log [dL/dt − (dL/dt)r] = log [(dL/dt)c − (dL/dt)r] − Kcrt. (dL/dt)c was related linearly (positive slope) with Kcr whereas (dL/dt)r was independent of (dL/dt)c and Kcr. The rate constant Kcr obeyed the usual Arrhenius temperature equation on the basis of linearity between log Kcr and 1/T. Dilute solutions (2M) required a long period (tB) before rupture occured and no change in length ΔLmax/L0 was observed. Concentrated solutions (10M) had much shorter tB and elevated ΔLmax/L0. At a fixed concentration of urea tB and ΔLmax/L0 were dependent upon tendon size (W0 = area × density). Induction of the contraction–relaxation process appears to be due to melting of crystalline regions in the collagenmucopolysaccharides structure of the tendon.
Nuclear magnetic relaxation in polymer melts and solutions
Authors: McCall David W. , Douglass Dean C. , Anderson Ernest W. 
Published: April 2003

AbstractNuclear magnetic relaxation times have been studied in some polymer liquids and solutions. The nonexponential decay of the transverse magnetization has been ascribed to the distribution of molecular weights. The use of such measurements as a means of determining average molecular weights and distributions is discussed. A preliminary application of this use is made for polyethylene. The implications of nuclear magnetic relaxation measurements are discussed in terms of molecular motional processes of the polymer chains.
Sound velocity and young's modulus in polyethylene
Authors: Davidse P. D. , Waterman H. I. , Westerdijk J. B. 
Published: April 2003

AbstractThe sound velocity was measured in bars for a number of low‐ and high‐density polyethylene samples. The longitudinal oscillations in the bar were generated electrodynamically. It was observed that the sound velocity decreased somewhat with length. Therefore all sound velocity measurements were made in bars with the same length and diameter. After each measurement the density was determined also. It was observed that a linear relationship exists between sound velocity and density. The degree of polymerization has no direct influence on the sound velocity. Young's modulus obtained from sound velocity measurements was represented as a function of density also. Young's modulus obtained from sound velocity measurments proved to be about three times larger than values obtained from bending and tensile tests. The very small deformations involved in sound velocity measurements and the elimination of time‐dependent viscoelastic effects because of the oscillations are mentioned as the most likely reasons for this.
Functionalizing Inorganic Solids: Towards Organic–Inorganic Nanostructured Materials for Intelligent and Bioinspired Systems
Authors: Ruiz‐Hitzky Eduardo 
Published: April 2003

AbstractThe design, preparation, and properties of organic–inorganic hybrid compounds are described and discussed with respect to their potential
uses as intelligent and bioinspired materials. Several synthesis strategies based on intercalation in 2D solids, the grafting of organic groups onto
silica and silicates, and the self‐assembly of organo‐silica materials are presented, focusing on the soft procedures that are used to
modify the functionality of the inorganic substrates. The combination of both organic and inorganic moieties at the nanometer level forms the basis for
preparing multifunctional solids that are provided with specific functions in response to different types of stimuli. In some cases these resemble
materials that are found in biological systems. Examples include organic–inorganic membranes that are based on intercalated macrocyclic compounds
and bi‐layer vesicles that consist of alkyl long‐chains arranged either in the confined region of layered silicates or as
self‐organized organo‐silica micelles. The role of certain hybrid materials such as membranes provides a different approach to the
development of artificial liposomes and other mimetic systems that have an organic–inorganic composition and nanostructural organization. Their
potential uses for DDS or DNA‐dense phases are also discussed and novel alternatives to bioinspired systems development are proposed. © 2003
The Japan Chemical Journal Forum and Wiley Periodicals, Inc., Chem Rec 3: 88–100; 2003: Published online in Wiley InterScience
(www.interscience.wiley.com) DOI 10.1002/tcr.10054
Experience of the Community-Residing Individual with Self-Induced Water Intoxication and the Family/Caregiver
Authors: May Deborah L. 
Published: April 2003

BACKGROUND: With long-term psychiatric hospitals closing, the severely mentally ill with self-induced water intoxication (SIWI) are residing in the community. Knowledge about the experience of the community-residing individuals with SIWI and their family/caregiver is needed to develop community programs of care. OBJECTIVES: The purpose of this multi-site study was to understand the experience of the community-residing individual with SIWI and of the family. STUDY DESIGN: Thirty community-residing individuals with SIWI and at least one of their family members/caregivers were interviewed. Semi-structured open-ended questions were used. Urine specific gravity testing was conducted to assure that the individual met the criteria of SIWI. RESULTS: Individuals reported that they felt better when they drank excess fluids, experienced anger when they drank, and believed that staying busy through work helped them control excess drinking. Individuals with SIWI and their families experienced negative feelings including fear of harm and helplessness and distanced themselves from the individual. Families agreed that distress triggered excess fluid drinking. Families also identified boredom as a trigger and felt helpless in being able to help the individual decrease fluid drinking. CONCLUSIONS: Excess fluid drinking is viewed as beneficial by individuals with SIWI, is triggered by distress and boredom, and creates fear and distancing when the family feels threatened by the intoxicated individual. Distress and boredom reduction need to be addressed in programs of care before the community-residing individual with SIWI will be motivated to participate in fluid management.
Colored pain drawings: preliminary observations in a neurosurgical practice
Authors: Masferrer Roberto , Prendergast Virginia , Hagell Peter 
Published: April 2003

AbstractBackground: Black and white pain drawings were introduced as a proposed means to identify patients, presenting with low back pain, who demonstrated functional overlay upon neurological testing. The use of color may enhance the usefulness of such pain drawings, but has not been described for adult patients.Aims: To retrospectively explore the use of colored pain drawings in patients with neck, low back, or radicular pain.Methods: Patients with neck, low back, or radicular pain referred to a community‐based neurosurgical practice for evaluation during 1 year (n=359) depicted their pain on anatomical drawings using colored pencils representing different pain characteristics. Patients with abnormal (n=55) and normal (n=54) pain drawings were selected for this study. Use of medications, findings on physical examination, radiographic findings, activity levels, Waddell signs, and pending litigation were recorded and compared between patients with normal and abnormal pain drawings, as assessed according to the Ransford penalty point system.Results: Patients whose colored pain drawings were abnormal, demonstrated a greater use of medications, more non‐focal clinical findings, Waddell signs, impaired activity levels, involvement in pending litigation, and significantly fewer pathological radiographic findings than patients with normal pain drawings.Conclusions: Our findings agree with previous observations using black and white pain drawings, indicating that colored pain drawings are no less useful than the black and white approach. Further research is necessary to examine the psychometric properties and clinical usefulness of colored pain drawings to predict outcomes and/or determine treatment.
Robust cluster analysis of microarray gene expression data
with the number of clusters determined biologically
Authors: Bickel David R. 
Published: April 2003

Abstract
Motivation: The success of each method of cluster analysis depends on how well its underlying model describes the patterns of expression. Outlier-resistant and distribution-insensitive clustering of genes are robust against violations of model assumptions.
Results: A measure of dissimilarity that combines advantages of the Euclidean distance and the correlation coefficient is introduced. The measure can be made robust using a rank order correlation coefficient. A robust graphical method of summarizing the results of cluster analysis and a biological method of determining the number of clusters are also presented. These methods are applied to a public data set, showing that rank-based methods perform better than log-based methods.
Availability: Software is available from http://www.davidbickel.com.
Contact: dbickel@mail.mcg.edu
Supplementary Information: http://www.davidbickel.com will have updates and related articles
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