bluuebunny/crossref_metadata_2025_split huggingface dataset:
Applicability of Statistical Theories of Network Formation
Authors: Dusˇek Karel 
Published: September 2007

AbstractSummary: The basis of the statistical method of generation of branched and crosslinked structures as a Markov process is analyzed with special emphasis on the effect of differences in reactivities of functional groups. For irreversible reactions, it is important that the transition probabilities are calculated kinetically and that bonds once formed are not allowed to be reformed. The statistical methods are often a good approximation of real situation even if not all approximations used in the model are fulfilled. Cyclization is still a serious problem in modeling; For practical application it is recommended to rescale calculated ring‐free dependences against the experimental gel point.
Monte Carlo Simulations on Nanoparticles in Elastomers. Effects of the Particles on the Dimensions of the Polymer Chains and the Mechanical Properties of the Networks
Authors: Mark James E. , Abou‐Hussein Reda , Sen Taner Z. , Kloczkowski Andrzej 
Published: September 2007

AbstractSummary: Reinforcement of elastomers is modeled using Monte Carlo simulations on rotational isomeric state chains, to characterize their spatial configurations in the vicinity of filler particles. The resulting filler‐perturbed distributions of the chain end‐to‐end distances are in agreement with experimental results gotten by neutron scattering. The use of these distributions in a standard molecular theory of rubberlike elasticity produces stress‐strain isotherms for elongation that are consistent with available experimental results.
Stress ‐ Optical Behaviour of Polymers
Authors: Ward Ian M. 
Published: September 2007

AbstractSummary: The collaborative research between Stepto and colleagues at Manchester University and Ward and colleagues at Leeds University is discussed in terms of its general significance for understanding the development of molecular orientation which occurs during the stretching of polymers. Cross‐linked polyethylene and polyethylene terephthalate are chosen as the key examples, with particular reference to their stress optical behaviour. Infra‐red spectroscopy is shown to be a valuable tool to validate the methodology developed by Stepto and his colleagues for modelling the behaviour of rubber‐like networks.
Structure Development in Flexible Polyurethane Foam‐Layered Silicate Nanocomposites
Authors: Wilkinson Arthur N. , Fithriyah Nurul H. , Stanford John L. , Suckley Daniel 
Published: September 2007

AbstractSummary: Polyurethane foam nanocomposites were formed via in‐situ copolymerisations, in which polyether polyol/water‐montmorillonite mixtures were reacted with toluene diisocyanate. The unmodified Na+‐ montmorillonite (MMT) was swollen in polyol/water using an ultrasound technique resulting in intercalated layers with increased basal spacings of 2.3 ± 0.1 nm. Measurements of quasi‐adiabatic temperature rise showed higher reaction rates as MMT loading increased from 0 to 10 wt.‐%. Forced‐adiabatic FTIR spectroscopy was used to determine the kinetics of both the copolymerisation and of the microphase separation between poly(ether‐urethane) soft segments and polyurea hard segments. The apparent microphase‐separation transition time decreased from 70 ± 3 to 42 ± 2 s upon addition of ≤10 wt.‐% MMT, but at reaction times >100 s there was significant retardation of the development of hydrogen bonding in the urea groups of the hard‐segment phase.
Comparative Study of Scattering and Osmotic Properties of Synthetic and Biopolymer Gels
Authors: Horkay Ferenc , Basser Peter J. , Hecht Anne‐Marie , Geissler Erik 
Published: September 2007

AbstractSummary: The effect of monovalent/divalent cation exchange on the structure and osmotic properties of chemically cross‐linked polyacrylate and DNA gels swollen in near physiological salt solutions has been investigated. Both systems exhibit a reversible volume phase transition in the presence of calcium ions. The small‐angle neutron scattering spectra of these gels display qualitatively similar features. At low values of q surface scattering is observed, while in the intermediate q range the signal is characteristic of scattering from rod‐like elements. At high values of q the scattering intensity is governed by the local (short‐range) geometry of the polymer chains. The competition between monovalent and divalent cations has been studied by anomalous small‐angle X‐ray scattering (ASAXS). The ASAXS results reveal that the local concentration of the divalent counter‐ions in the vicinity of the polymer chains significantly exceeds that of the monovalent counter‐ions.
Comparison of Critical Exponents Determined by Rheology and Dynamic Light Scattering on Irreversible and Reversible Gelling Systems
Authors: Richter Sven 
Published: September 2007

AbstractSummary:The sol‐gel transition of a radical chain cross‐linking copoly‐merization system [N‐vinylcaprolactam/2‐hydroxylethyl methacrylate/allyl‐methacrylate] and various thermoreversible gelling systems (mixtures made of xanthan gum and locust bean gum as well as gelatin) have been studied using in‐situ time‐resolved dynamic light scattering (DLS) and in‐situ rheology. A critical dynamical behavior was observed near the sol‐gel transition, which is characterized by the presence of a power‐law spectra in the time‐intensity correlation functiong2(t)−1 ∝ t−µand in the low‐amplitude oscillatory shear experimentG′(ω) ∝ G″(ω) ∝ ωn. A comparison of the obtained critical dynamical exponentsµandnwere made according to the theory by Doi and Onuki. This theory predicts a relation between these exponents, but up to now no detailed experimental comparison was done in the past. It was found that for all investigated systemsn > µ.
Autonomous Volume Transitions of a Polybase Triblock Copolymer Gel in a Chemically Driven pH‐Oscillator
Authors: Topham Paul D. , Howse Jonathan R. , Crook Colin J. , Gleeson Anthony J. , Bras Wim , Armes Steven P. , Jones Richard A. L. , Ryan Anthony J. 
Published: September 2007

AbstractSummary:A pH‐responsive ABA triblock copolymer, comprising poly(methyl methacrylate)‐block‐poly(2‐(diethylamino)ethyl methacrylate)‐block‐poly(methyl methacrylate) [PMMA‐b‐PDEA‐b‐PMMA], has been cast into thin films with a well‐defined microstructure. Small Angle X‐ray Scattering (SAXS) and Atomic Force Microscopy (AFM) studies confirm that this copolymer forms a hydrogel consisting of PMMA spheres embedded within a polybase PDEA matrix, with the PMMA domains acting as physical cross‐links. The hydrogel has a pH‐reversible coil‐globule transition at around pH 4.5. This responsive physical property was exploited by immersing a sample of copolymer hydrogel in an aqueous solution containing a cyclic pH‐oscillating reaction, whereby the pH was continuously oscillated above and below the transition pH so as to induce autonomous volume transitions. The changes in microscopic and macroscopic length scales correlate closely during (de)swelling cycles, with affine behaviour occurring over five orders of magnitude.
Elastic Properties of Semi‐Flexible Chains and Networks
Authors: Cifra Peter , Bleha Tomáš 
Published: September 2007

AbstractSummary: Elastic properties of noncharged polymers of stiffness ranging from flexible to rigid chains are determined from Monte Carlo simulations. The discrete wormlike chain (WLC) model with self‐interacting units is applied to chains of intermediate lengths. Elastic free energy and the force‐extension profiles of chains of variable stiffness are computed in an isometric ensemble. Occurrence of a plateau on the force‐extension curves at intermediate chain stiffness is noted. Qualitative differences are found between force profiles from simulations and from the standard (ideal) WLC model. The single‐chain data on influence of bending stiffness were employed in the three‐chain model of networks. Stress‐strain relations for networks show a highly nonlinear behavior with the marked strain‐stiffening effect.
Hyperbranched Aromatic Polyesters
Authors: Walczak Małgorzata , Lechowicz Jaromir B. , Galina Henryk 
Published: September 2007

AbstractSummary: Having developed a theoretical model of hyperbranched polymerization involving AB2 and B2 monomers we present preliminary results of a test of its validity for the system consisting of 4,4‐bis(4‐hydroxyphenyl)pentanoic acid (AB2 monomer) and bisphenol A (B2 monomer). The monomers reacted at room temperature to yield the title hyperbranched polyesters. Diisopropylcarbodiimide (condensation water remover) along with an effective catalyst were used for that purpose. The total of AB2 monomer was introduced at once to a reactor containing B2 core monomer or it was divided into 3 or 5 equal portions and each of them introduced after the monomers previously present have reacted to a predetermined conversion. GPC measurements of the resulting molecular mass distribution gave inconclusive results because of poor reproducibility of polymer isolation/purification procedure and/or insufficient accuracy of GPC technique.
Deformation Studies on Polymer‐Clay Nanocomposite Gels
Authors: Shibayama Mitsuhiro , Miyazaki Sho , Endo Hitoshi , Karino Takeshi , Haraguchi Kazutoshi 
Published: September 2007

AbstractSummary: The polymer‐clay nanocomposite gels (NC gels), developed by Haraguchi et al. (Adv. Mater., 2001), exhibit extraordinarily high mechanical properties, such as high elongations and high ultimate strengths. In order to understand the origin of these properties, contrast‐matched small‐angle neutron scattering (SANS) studies were carried out for stretched NC gels. It was found that (1) the scattering function for NC gels is simply given by a Lorentz function, a function for semidilute polymer solutions, without a characteristic cross‐link inhomogeneity term for polymer gels, and (2) the unique mechanical properties are ascribed to its network structure, i.e., long polymer chains connected by “plane” cross‐links.
2‐Dimensional Network Formation from a Graft Copolymer at the Air‐Water Interface
Authors: de Samaniego M. Simon Saenz , Miller A.F. 
Published: September 2007

AbstractSummary: The UV induced cross‐linking of a well defined graft copolymer polynorbornene‐g‐poly(ethylene oxide) at the air‐water interface has been investigated. Network formation has been monitored qualitatively by observing changes in surface pressure with UV exposure time working under constant area conditions. Surface film concentration has been used as the design parameter to manipulate initial film organization, and consequently position of the functional groups. Exposure of the copolymer film to UV light at different surface concentrations in the liquid condensed region shows the closer the molecules pack together the faster the cross‐linking reaction, while no cross‐linking occurs when the molecules are far apart in the liquid expanded state.
Characterization of Composite Networks Made of Type I Collagen, Hyaluronic Acid and Decorin
Authors: Lélu Sylvie , Pluen Alain 
Published: September 2007

AbstractSummary: To ultimately assess the ability of macromolecular medicines e.g. liposomes, non viral gene delivery systems, to penetrate one of the least studied physiological barriers, the extracellular matrix (ECM), composite networks made of different ECM components i.e. type I collagen, hyaluronic acid and a proteoglycan, decorin, were prepared. These composite networks were characterized by rheology, Confocal Reflection Microscopy, Fluorescence Recovery After Photobleaching and Transmission Electron Microscopy. While being at the low end of its physiological concentration, collagen appears to be the backbone of the composite networks as it provides the elastic modulus. On the other hand, 15 kDa and 1.1 MDa hyaluronic acid, when present at physiological levels interpenetrate the collagen network. When approaching their overlap concentration, hyaluronic acid chains lead to an increase of the population of collagen fibrils. Finally, while decorin increased the population of fibrils in pure collagen networks, its role in presence of hyaluronic acid remains unclear as it does not alter the diameter of fibrils nor their population.
One‐ and Two‐Component Bottle‐Brush Polymers: Simulations Compared to Theoretical Predictions
Authors: Hsu Hsiao‐Ping , Paul Wolfgang , Binder Kurt 
Published: September 2007

AbstractScaling predictions for bottle‐brush polymers with a rigid backbone and flexible side chains under good solvent conditions are discussed and their validity is assessed by a comparison with Monte Carlo simulations of a simple lattice model. It is shown that typically only a rather weak stretching of the side chains is realized, and then the scaling predictions are not applicable. Also two‐component bottle brush polymers are considered, where two types (A,B) of side chains are grafted, assuming that monomers of different kind repel each other. In this case, variable solvent quality is allowed. Theories predict “Janus cylinder”‐type phase separation along the backbone in this case. The Monte Carlo simulations, using the pruned‐enriched Rosenbluth method (PERM) give evidence that the phase separation between an A‐rich part of the cylindrical molecule and a B‐rich part can only occur locally. The correlation length of this microphase separation can be controlled by the solvent quality. This lack of a phase transition is interpreted by an analogy with models for ferromagnets in one space dimension.magnified image
An inherited disorder characterized by repeated episodes of bilateral ballism: A case report
Authors: Kakinuma Hiroaki , Hori Ariyuki , Itoh Masatsune , Nakamura Tsuneyuki , Takahashi Hiroaki 
Published: September 2007

AbstractThis case report describes two siblings with a dyskinetic form of cerebral palsy who had repeated episodes of fever‐induced bilateral ballistic movements. The boy and his sister experienced the first episodes during early childhood. The movements developed over several hours and required rapid intervention. Electroencephalograms during the attacks showed no paroxysms, and brain magnetic resonance imaging scans revealed no lesions. The brother died of acute renal failure at age 5 due to rhabdomyolysis after his fifth episode of prolonged bilateral ballistic movements. This is the first report of an inherited disorder characterized by repeated episodes of violent movements. © 2007 Movement Disorder Society
Compartmental loss of striatal medium spiny neurons in multiple system atrophy of parkinsonian type
Authors: Sato Kenta , Kaji Ryuji , Matsumoto Sadayuki , Nagahiro Shinji , Goto Satoshi 
Published: September 2007

AbstractTopographical or compartmental involvement of the putamen and caudate nucleus has not been fully elucidated in multiple system atrophy predominantly presenting with Parkinsonism (MSA‐P). We carried out immunohistochemical studies using antibodies to calbindin (CALB) and calcineurin (CaN) as neurochemical markers for striatal medium spiny neurons. We found that in the caudal and dorsolateral putamen, the area most affected in MSA‐P, the medium spiny neurons positive for CALB were severely depleted, while CaN‐positive neurons were relatively spared in a mosaic pattern. In the dorsal caudate nucleus, an area less affected in MSA, residual CALB‐positive neurons exhibited a compartmentalized distribution that corresponded with the striosomal arrangement visualized by Met‐enkephalin immunostaining. Our findings suggest that there is a compartmental difference in the susceptibility of striatal medium spiny neurons to neurodegeneration in MSA‐P. © 2007 Movement Disorder Society
Skin vasodilator response to local heating in multiple system atrophy
Authors: Yamanaka Yoshitaka , Asahina Masato , Mathias Christopher J. , Akaogi Yuichi , Koyama Yu , Hattori Takamichi 
Published: September 2007

AbstractLocal heating of nonglabrous skin increases skin blood flow (SkBF) in two phases. The initial peak (P1) is mediated by a sensory‐axon reflex and the plateau phase (P2) by local production of substances such as nitric oxide. We evaluated the SkBF response to local heating in 15 multiple system atrophy (MSA) patients with autonomic failure and 12 age‐matched healthy controls. The mean ratio of SkBF at P1 to that at baseline (SkBFP1/SkBFbase ratio) in MSA was significantly lower than that in controls (P < 0.01). The mean ratio of SkBF at P2 seemed to be slightly reduced in the MSA patients, compared with controls, although there was no significant difference. The P1 phase is thought to be mediated by a sensory‐axon reflex modulated by sympathetic nerve activity. These findings are indicative of the skin sympathetic vasomotor dysfunction in MSA. © 2007 Movement Disorder Society
Ten‐year follow‐up of Parkinson's disease patients randomized to initial therapy with ropinirole or levodopa
Authors: Hauser Robert A. , Rascol Olivier , Korczyn Amos D. , Jon Stoessl A. , Watts Ray L. , Poewe Werner , De Deyn Peter P. , Lang Anthony E. 
Published: September 2007

AbstractIn a 5‐year, double‐blind study, subjects with Parkinson's disease (PD) who were randomized to initial treatment with ropinirole had a significantly lower incidence of dyskinesia compared with subjects randomized to levodopa, although Unified Parkinson's Disease Rating Scale (UPDRS) motor scores were significantly more improved in the levodopa group. Subjects who completed the original study were eligible to participate in a long‐term extension study conducted according to an open, naturalistic design and were evaluated approximately every 6 months until they had been followed for a total of 10 years. Comparing subjects randomized to initial treatment with ropinirole (n = 42) and levodopa (n = 27), the incidence of dyskinesia was significantly lower in the ropinirole group (adjusted odds ratio [OR] = 0.3; 95% confidence interval [CI]: 0.1, 1.0; P = 0.046) and the median time to dyskinesia was significantly longer (adjusted hazard ratio = 0.4; 95% CI: 0.2, 0.8; P = 0.007). The incidence of at least moderate wearing off (“off” time ≥26% of the awake day) was also significantly lower in the ropinirole group (adjusted OR = 0.3; 95% CI: 0.09, 0.03; P = 0.03). There were no significant differences in change in UPDRS activities of daily living or motor scores, or scores for the 39‐item PD questionnaire, Clinical Global Impression, or the Epworth Sleepiness Scale. Early treatment decisions for individual patients depend largely on the anticipated risk of side effects and long‐term complications. Both ropinirole and levodopa are viable treatment options in early PD. © 2007 Movement Disorder Society
A neuropsychological longitudinal study in Parkinson's patients with and without hallucinations
Authors: Santangelo Gabriella , Trojano Luigi , Vitale Carmine , Ianniciello Marta , Amboni Marianna , Grossi Dario , Barone Paolo 
Published: September 2007

AbstractThe aim of this work was to determine the progression of cognitive impairment in Parkinson's disease (PD) patients with or without hallucinations. Two years after the first assessment, 36 PD patients were re‐evaluated on standardized neuropsychological tests, including the Frontal Assessment Battery (FAB), and on rating scales for overall cognitive functioning, functional autonomy, behavioral disorders. Nine patients had hallucinations at baseline and endpoint assessments; 12 patients developed hallucinations during the follow‐up; and 15 patients were hallucination‐free throughout the study. Cognitive performance significantly declined in all three groups, but at endpoint assessment PD hallucinators scored significantly lower than nonhallucinators on phonological and semantic fluency tasks, immediate free recall and the go/no‐go FAB subtest; moreover, they showed more severe apathy than nonhallucinators. Reduced phonological fluency at baseline (odds ratio [OR], 13.5; 95% CI: 1.34–135.98, P = 0.027) was the only independent predictor of onset of hallucinations after 2 years, whereas hallucinations (OR, 10.1; 95% CI: 1.94–51.54, P = 0.006) and poor phonological fluency (OR, 6.1; 95% CI: 1.04–35.03, P = 0.045) independently predicted development of diffuse cognitive impairment. We concluded that reduced verbal fluency scores may predict the onset of hallucinations, while hallucinations and poor phonological fluency may predict development of dementia in PD patients. © 2007 Movement Disorder Society
Bonnet monkey (Macaca radiata) ovaries, like human oocytes, express four zona pellucida glycoproteins
Authors: Ganguly Anasua , Sharma R.K. , Gupta Satish Kumar 
Published: September 2007

AbstractRecent studies document that the zona pellucida matrix of human oocytes is composed of four glycoproteins designated as ZP1, ZP2, ZP3, and ZP4 instead of three as proposed in mouse model. In the present study, investigations were carried out to find the presence of the fourth ZP glycoprotein in the ovaries of non‐human primates namely bonnet monkey (Macaca radiata). Employing total RNA isolated from bonnet monkey ovaries, the complementary deoxyribonucleic acid (cDNA) encoding bonnet monkey ZP1 (up to furin cleavage site) was successfully amplified by reverse transcribed polymerase chain reaction (RT‐PCR). The deduced amino acid (aa) sequence of bonnet monkey ZP1 revealed 96.0% identity with human ZP1. The 21 cysteine residues present in bonnet monkey ZP1 were conserved in human, mouse, rat, quail, and chicken. Simultaneously, polyclonal antibodies were generated in mice against synthetic peptides corresponding to human ZP1 (P1, 137–150 aa; P2, 223–235 aa; P3, 237–251 aa; P4, 413–432 aa; and P5, 433–451 aa). Employing anti‐peptide antibodies that were devoid of cross‐reactivity as determined by ELISA with human/bonnet monkey recombinant ZP2, ZP3, and ZP4, the presence of ZP1 in the ovaries of bonnet monkey and human oocytes was demonstrated by indirect immunofluorescence. The antibodies against peptides P3 and P4 reacted only with the ZP of bonnet monkey ovaries and not other ovarian associated cells. The data presented in this manuscript provide evidence, for the first time, that the bonnet monkey ZP matrix is composed of four glycoproteins. Mol. Reprod. Dev. 75: 156–166, 2008. © 2007 Wiley‐Liss, Inc.
Both type 1 and type 2a muscle fibers can respond to enzyme therapy in Pompe disease
Authors: Drost Maarten R. , Schaart Gert , van Dijk Paul , van Capelle Carine I. , van Der Vusse Ger J. , Delhaas Tammo , van Der Ploeg Ans T. , Reuser Arnold J. J. 
Published: September 2007

AbstractMuscle weakness is the main symptom of Pompe disease, a lysosomal storage disorder for which major clinical benefits of enzyme replacement therapy (ERT) have been documented recently. Restoration of skeletal muscle function is a challenging goal. Type 2 muscle fibers of mice with Pompe disease have proven resistant to therapy. To investigate the response in humans, we studied muscle biopsies of a severely affected infant before and after 17 months of therapy. Type 1 and 2a fibers were marked with antibodies, and lysosome‐associated membrane protein‐1 (Lamp1) was used as the lysosomal membrane marker. Quantitative measurements showed a 2.5–3‐fold increase of fiber cross‐sectional area of both fiber types during therapy and normalization of the Lamp1 signal in ∼95% of type 1 and ∼75% of type 2a fibers. The response of both type 1 and 2a muscle fibers in the patient studied herein corroborates the beneficial effects of enzyme therapy seen in patients with Pompe disease. Muscle Nerve, 2007