bluuebunny/crossref_metadata_2025_split huggingface dataset:
Poly(neopentylene carbonate) Hyperstars
Authors: Löwenhielm Peter , Claesson Hans , Hult Anders 
Published: July 2004

AbstractSummary: Branched aliphatic polycarbonates were synthesized by ring opening polymerization of 5,5‐dimethyl‐1,3‐dioxane‐2‐one (NPC) initiated from polyfunctional alcohols and a commercial hyperbranched polyester (BOLTORN®). Polymerizations in the presence of fumaric acid under bulk conditions allowed high conversion (80%) without gelation. The synthesis of polymers with long chain branches was confirmed by size exclusion chromatography and universal calibration. The Mark–Houwink exponent decreased, indicating an increased density, while increasing the number of arms. The star polymers with up to four arms showed thermal properties Tg (20–30 °C) and Tm (100–110 °C) similar to linear PNPC.Boltorn™ hyperbranched polymer with radial polycarbonate grafts.magnified imageBoltorn™ hyperbranched polymer with radial polycarbonate grafts.
On the Radiation‐Induced Polymerisation of 2,3‐Dihydropyran
Authors: Naumov Sergej , Janovský Igor , Knolle Wolfgang , Mehnert Reiner 
Published: July 2004

AbstractSummary: Concentrated (5 mol‐%) solutions of 2,3‐dihydropyran in CFCl2CF2Cl matrix were irradiated at 77 K and several intermediates – radical cation, dimer radical cation, dihydropyryl radical and a trapped polymer radical – were observed by low‐temperature EPR spectroscopy. The irradiated solutions yielded after melting a polymeric product, which was characterised by IR spectroscopy and GPC. The polydisperse polymer is assumed to be formed by a cationic process initiated by a dimer carbocation. The polymerization proceeds via the ring double bonds, while ring‐opening reaction occurs in a small extent. The free‐radical mechanism via the dihydropyryl radical leads to low molecular weight oligomers only. The quantum chemical calculations support the interpretation of the experimental results.
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Isobutene Polymerization and Copolymerization with Isoprene Initiated by [Cp*TiMe2]+ in the Presence of a Novel Type of Weakly Coordinating Counteranion
Authors: Tse Calvin K. W. , Kumar Kainthan Rajesh , Drewitt Mark J. , Baird Michael C. 
Published: July 2004

AbstractSummary: The highly electrophilic borane B(C6F5)3 reacts with octadecanoic acid (n‐C17H35CO2H, stearic acid) to form 1:1 and 2:1 adducts [n‐C17H35CO2H][B(C6F5)3] and [n‐C17H35CO2H][B(C6F5)3]2. These adducts exhibit enhanced acidities, and react with Cp*TiMe3 in methylene chloride and toluene to give methane and the complexes [Cp*TiMe2][n‐C17H35CO2{B(C6F5)3}1,2]; the 2:1 complex in particular is a very good initiator for the carbocationic polymerization of isobutene (IB) and copolymerization of IB with isoprene at temperatures as high as −30 °C. High conversions to high molecular weight homo‐ and copolymers are obtained, consistent with the anion [n‐C17H35CO2{B(C6F5)3}2]− being very weakly coordinating.Novel class of Brønsted acidic initiators behave as very good initiators, e.g. in homopolymerisation of isobutene.magnified imageNovel class of Brønsted acidic initiators behave as very good initiators, e.g. in homopolymerisation of isobutene.
Microstructure and Properties of Poly(amide urethane)s: Comparison of the Reactivity of α‐Hydroxy‐ω‐O‐phenyl Urethanes and α‐Hydroxy‐ω‐O‐hydroxyethyl Urethanes
Authors: Sharma Bhaskar , Ubaghs Luc , Keul Helmut , Höcker Hartwig , Loontjens Ton , van Benthem Rolf 
Published: July 2004

AbstractSummary: Poly(amide urethane)s were prepared from ε‐caprolactam, amino alcohols, and diphenyl carbonate or ethylene carbonate in three steps. Polycondensation was performed either with α‐hydroxy‐ω‐O‐phenyl urethanes or with α‐hydroxy‐ω‐O‐hydroxyethyl urethanes; it was found that the reactivity at 90 °C of the first is much higher than that of the latter. For nearly equal reactivity, the temperature for the polycondensation of α‐hydroxy‐ω‐O‐hydroxyethyl urethanes had to be increased from 90 °C to 150 °C. The microstructure of the resulting poly(amide urethane)s differs by the content of urea groups in the polymer chains, which is 5% for poly(amide urethane)s prepared from α‐hydroxy‐ω‐O‐phenyl urethanes and 15% for poly(amide urethane)s prepared from α‐hydroxy‐ω‐O‐hydroxyethyl urethanes. As a consequence, the thermal properties of the poly(amide urethane)s differ slightly.Synthesis of poly(amide urethane)s.magnified imageSynthesis of poly(amide urethane)s.
Surfactant‐Free Emulsion Polymerization of Various Methacrylates: Towards Monodisperse Colloids for Polymer Opals
Authors: Egen Marc , Zentel Rudolf 
Published: July 2004

AbstractSummary: A systematic investigation of the surfactant‐free emulsion polymerization (SFEP) on three different methacrylates (MMA, tert‐butyl methacrylate and 2,2,2‐trifluoro ethyl methacrylate) is described to obtain monodisperse colloids for the preparation of artificial “polymer opals”. The experimental results are in agreement with a model, in which seed particles are formed very early during the polymerization process. The particles grow afterwards into the colloids until all monomer is consumed. This gives rise to a linear relationship between the volume of the colloids and the ratio of monomer to water in the reaction batch. The concentration of the seed particles depends thereby on the hydrophobicity of the monomers and can be varied by the addition of salt. The relationship between the composition of the reaction batch and the size of the colloids differs from monomer to monomer. It can, however, be described for all systems by the introduction of an empirical system dependent parameter pM (master curve). It is thus possible to predict the colloidal size for new monomer (or salt) systems from a single measurement point. Colloids with a diameter of more than 500 nm can be prepared by a two stage seeded polymerization. The colloids prepared with this method are so monodispersed (well below 5%) that they can easily be crystallized into artificial polymer opals of a high optical quality.Dried opaline films (second‐order reflection).magnified imageDried opaline films (second‐order reflection).
UNFOLD‐SENSE: A parallel MRI method with self‐calibration and artifact suppression
Authors: Madore Bruno 
Published: July 2004

AbstractThis work aims at improving the performance of parallel imaging by using it with our “unaliasing by Fourier‐encoding the overlaps in the temporal dimension” (UNFOLD) temporal strategy. A self‐calibration method called “self, hybrid referencing with UNFOLD and GRAPPA” (SHRUG) is presented. SHRUG combines the UNFOLD‐based sensitivity mapping strategy introduced in the TSENSE method by Kellman et al. (5), with the strategy introduced in the GRAPPA method by Griswold et al. (10). SHRUG merges the two approaches to alleviate their respective limitations, and provides fast self‐calibration at any given acceleration factor. UNFOLD‐SENSE further includes an UNFOLD artifact suppression scheme to significantly suppress artifacts and amplified noise produced by parallel imaging. This suppression scheme, which was published previously (4), is related to another method that was presented independently as part of TSENSE. While the two are equivalent at accelerations ≤ 2.0, the present approach is shown here to be significantly superior at accelerations > 2.0, with up to double the artifact suppression at high accelerations. Furthermore, a slight modification of Cartesian SENSE is introduced, which allows departures from purely Cartesian sampling grids. This technique, termed variable‐density SENSE (vdSENSE), allows the variable‐density data required by SHRUG to be reconstructed with the simplicity and fast processing of Cartesian SENSE. UNFOLD‐SENSE is given by the combination of SHRUG for sensitivity mapping, vdSENSE for reconstruction, and UNFOLD for artifact/amplified noise suppression. The method was implemented, with online reconstruction, on both an SSFP and a myocardium‐perfusion sequence. The results from six patients scanned with UNFOLD‐SENSE are presented. Magn Reson Med 52:310–320, 2004. © 2004 Wiley‐Liss, Inc.
Tubule and neurofilament immunoreactivity in human hairy skin: Markers for intraepidermal nerve fibers
Authors: Lauria Giuseppe , Borgna Monica , Morbin Michela , Lombardi Raffaella , Mazzoleni Giulia , Sghirlanzoni Angelo , Pareyson Davide 
Published: July 2004

AbstractThe cytoplasmic protein gene product 9.5 (PGP 9.5) is considered a reliable marker for intraepidermal nerve fibers (IENFs). However, PGP 9.5 expression has never been compared with antibodies against the main components of the cytoskeleton. We compared the density of PGP 9.5–positive IENF at the leg with that obtained using a panel of antibodies specific for certain cytoskeletal components, namely, anti–unique β‐tubulin (TuJ1), anti–nonphosphorylated microtubule‐associated protein‐1B (MAP1B), anti‐70 and 200 KDa neurofilament (NF), and antiphosphorylated neurofilament (SMI 312), in 15 healthy subjects and in 10 patients with painful neuropathy. We also performed colocalization studies and investigated the relationship between IENFs and Schwann cells. In both controls and neuropathies, the density of IENF labeled by PGP 9.5, TuJ1, and MAP1B did not differ, whereas that of NF and SMI 312 was significantly lower. Double‐staining studies confirmed that antibodies against cytoskeletal markers can be used to reliably stain skin nerve fibers, suggesting that they might provide insight into specific axonal impairment in peripheral neuropathies. Muscle Nerve 30: 310–316, 2004
Reduced acetylcholine receptor density, morphological remodeling, and butyrylcholinesterase activity can sustain muscle function in acetylcholinesterase knockout mice
Authors: Adler Michael , Manley Heather A. , Purcell Angela L. , Deshpande Sharad S. , Hamilton Tracey A. , Kan Robert K. , Oyler George , Lockridge Oksana , Duysen Ellen G. , Sheridan Robert E. 
Published: July 2004

AbstractNerve‐evoked contractions were studied in vitro in phrenic nerve–hemidiaphragm preparations from strain 129X1 acetylcholinesterase knockout (AChE−/−) mice and their wild‐type littermates (AChE+/+). The AChE−/− mice fail to express AChE but have normal levels of butyrylcholinesterase (BChE) and can survive into adulthood. Twitch tensions elicited in diaphragms of AChE−/− mice by single supramaximal stimuli had larger amplitudes and slower rise and decay times than did those in wild‐type animals. In AChE−/− preparations, repetitive stimulation at frequencies of 20 and 50 Hz and at 200 and 400 Hz produced decremental muscle tensions; however, stimulation at 70 and 100 Hz resulted in little or no loss of tension during trains. Muscles from AChE+/+ mice maintained tension at all frequencies examined but exhibited tetanic fade after exposure to the selective AChE inhibitor 1,5‐bis(4‐allyldimethyl‐ammoniumphenyl)pentane‐3‐one (BW 284C51). The ability of diaphragm muscles from AChE−/− mice to maintain tension at 70 and 100 Hz suggests a partial compensation for impairment of acetylcholine (ACh) hydrolysis. Three mechanisms—including a reliance on BChE activity for termination of ACh action, downregulation of nicotinic acetylcholine receptors (nAChRs), and morphological remodeling of the endplate region—were identified. Studies of neuromuscular transmission in this model system provide an excellent opportunity to evaluate the role of AChE without complications arising from use of inhibitors. Muscle Nerve 30: 317–327, 2004
Postactivation potentiation in human muscle is not related to the type of maximal conditioning contraction
Authors: Baudry Stéphane , Duchateau Jacques 
Published: July 2004

AbstractThe mechanical performance of a muscle can be enhanced by preceding contractile activity, such as occurs with postactivation potentiation. To investigate whether the type of contraction influences the extent of potentiation, the effects of 6‐s maximal isometric (ISO), concentric (CON), and eccentric (ECC) maximal voluntary contractions (MVC) on the muscle twitch were compared in the tibialis anterior of nine subjects. The study also examined the effect of postactivation potentiation on the force evoked by the second (C2) and third (C3) responses of two‐pulse (PT2) and three‐pulse (PT3) trains that were delivered at a 10‐ms interpulse interval. The results showed that immediately after the conditioning MVC, twitch torque (Pt) and its maximal rate of torque development (+dPt/dt) and relaxation (‐dPt/dt) were significantly enhanced, without any change in contraction time (CT), half‐relaxation time (½RT), and compound muscle action potential (M wave). The extent of Pt potentiation was similar for all MVC modalities, and the mean maximal values ranged from 150% to 180%. Furthermore, postactivation potentiation was greater for the single pulse compared with PT2 and PT3 responses. All parameters returned to initial values within 7–10 min. Although Pt (or C1) was potentiated more than was C2 and C3, its decline over time was proportionally more rapid than those for C2 and C3. We conclude that postactivation potentiation was not related to the type of conditioning MVC under these experimental conditions. The observation that postactivation potentiation increased C1 more than C2 and C3 indicates that a saturation process limits the extent of potentiation during the summation of successive responses to a train of stimuli. These results have practical application in the design of functional electrical stimulation protocols. Muscle Nerve, 2004
Evaluation of patients with recurrent symptoms after ulnar nerve transposition
Authors: Matei Cristina I. , Logigian Eric L. , Shefner Jeremy M. 
Published: July 2004

AbstractFocal entrapment of the ulnar nerve occurs most frequently in the region of the elbow, at the ulnar groove or beneath the humeroulnar aponeurosis. Surgical treatment commonly involves transposition of the nerve anterior to the medial epicondyle, in the antecubital fossa. Symptoms may recur after surgery, and, to assess their etiology, we studied 10 patients with recurrent ulnar symptoms after transposition. Conventional motor and sensory conduction studies were performed, as was mapping of nerve position using submaximal stimuli. In 9 of 10 patients, the ulnar nerve at the elbow was located adjacent to the medial epicondyle, rather than in the antecubital fossa. Focal slowing in the region of the elbow was noted in 8 patients, and an additional site of focal slowing was found in the forearm in 3 patients. We conclude that in patients with recurrent symptoms after ulnar nerve transposition postoperative position of the ulnar nerve may be medial, often near the medial epicondyle. This location may predispose the nerve to recurrent trauma or cause traction on the nerve at more distal locations within the forearm. The prevalence of this medial location of the ulnar nerve in asymptomatic postsurgical patients is unknown. Muscle Nerve 30: 493–496, 2004
Motor unit characteristics in healthy subjects and those with postpoliomyelitis syndrome: A high‐density surface EMG study
Authors: Drost Gea , Stegeman Dick F. , Schillings Maartje L. , Horemans Herwin L. D. , Janssen Henny M. H. A. , Massa Mark , Nollet Frans , Zwarts Machiel J. 
Published: July 2004

AbstractThe purpose of this study was to identify optimal ways to detect neurogenic changes with high‐density surface electromyography (HD‐sEMG). For this purpose, we searched for the variables that most clearly discriminated between postpoliomyelitis and healthy subjects. We obtained HD‐sEMG from the quadriceps muscle at different force levels in nine subjects with postpoliomyelitis syndrome and in matched healthy controls. Single motor unit action potentials (MUAPs), extracted from the HD‐sEMG signal and the raw signal itself, were analyzed. Areas under the curve of the extracted MUAP waveform, indicating motor unit size, perfectly separated both groups. Raw signal analysis showed significant differences between groups for the monopolarly recorded amplitude up to 60% of maximal force and for the level of interference at higher force levels (40–100% force). We conclude that with HD‐sEMG it is possible to detect neurogenic motor unit changes noninvasively, both by analysis of the raw signal itself and by analysis of extracted single MUAPs. The diagnostic yield of the single MUAP analysis is clearly higher. These findings point toward applications for clinical practice and invite further studies exploring the diagnostic value of HD‐sEMG. Muscle Nerve 30: 269–276, 2004
Effect of heterogeneities on the physical properties of elastomers derived from butadiene cured with dicumyl peroxide
Authors: Gonzalez L , Rodriguez A , Del Campo A , Marcos‐Fernandez A 
Published: July 2004

AbstractThe scope of this paper is to continue our earlier study of the peroxide curing of elastomers derived from butadiene. Experimental evidence indicates that abstraction of allylic hydrogen and addition to the double bonds can act as a mechanism for cross‐linking. The addition reaction may give rise to a polymerization reaction between adjacent double bonds, thus generating a heterogeneous network, with negative effects on the physical properties of the vulcanizates. Copyright © 2004 Society of Chemical Industry
Initiator‐fragment incorporation radical polymerization of ethylene glycol dimethacrylate in the presence of 1,1‐diphenylethylene: synthesis and characterization of soluble hyperbranched polymer nanoparticles
Authors: Sato Tsuneyuki , Miyagi Takashi , Hirano Tomohiro , Seno Makiko 
Published: July 2004

AbstractThe polymerization of ethylene glycol dimethacrylate (EGDMA) as crosslinker was carried out at 70 and 80 °C in benzene using dimethyl 2,2′‐azobisisobutyrate (MAIB) as initiator at concentrations as high as 0.50–0.70 mol l−1 in the presence of 1,1‐diphenylethylene (DPE), where the concentrations of EGDMA and DPE were 0.50–0.70 and 0.25–0.50 mol l−1, respectively. The polymerization proceeded homogeneously, without gelation, to give soluble polymers. The yield and molecular weight of the resulting polymers increased with time. The homogeneous polymerization system involved ESR‐observable DPE‐derived radicals of considerably high concentration (3.6–5.3 × 10−5 mol l−1). The methoxycarbonylpropyl groups as MAIB‐fragments were incorporated as a main constituent (35–50 mol%) into the polymers (initiator‐fragment incorporation radical polymerization). The polymers also contained DPE units (15 mol%) and EGDMA units with double bonds (10–25 mol%) and without double bonds (20 mol%). Results from gel permeation chromatography (GPC)–multiangle laser light scattering (MALLS), transmission electron microscopy (TEM) and viscometric measurements revealed that the individual polymer molecules were formed as hyperbranched nanoparticles. Copyright © 2004 Society of Chemical Industry
Behavioral momentum in academics: Using embedded high‐p sequences to increase academic productivity
Authors: Lee David L. , Belfiore Phillip J. , Scheeler Mary Catherine , Hua Youjia , Smith Rachel 
Published: July 2004

AbstractThe use of high‐probability (high‐p) request sequences has enjoyed support in the applied behavioral literature as a method to increase compliance. Based on the theory of behavioral momentum, high‐probability sequences increase the rate of responding, and subsequent rate of reinforcement, within a response class. This increase in density of reinforcement results in increased responding for the response class as a whole. Early research in this area had focused mainly on compliance issues for individuals with developmental disabilities. However, more recently the utility of high‐p sequences has been examined within the context of academics. The purpose of these two experiments was to examine the use of high‐p sequences with two academic tasks—letter‐writing and mathematics problem completion. The results of these studies suggest that high‐p sequences can be used to increase academic productivity. Moreover, the addition of experimenter‐delivered reinforcers to existing high‐p sequences enhances overall behavioral persistence. Theoretical and applied implications of persistence and behavioral momentum are discussed. © 2004 Wiley Periodicals, Inc. Psychol Schs 41: 789–801, 2004.
Adjustment scales for preschool intervention: Extending validity and relevance across multiple perspectives
Authors: Bulotsky‐Shearer Rebecca , Fantuzzo John 
Published: July 2004

AbstractA series of studies extended psychometric research on the Adjustment Scales for Preschool Intervention (ASPI). The ASPI is a multidimensional measure of preschool emotional and behavioral adjustment for use within formal early childhood educational programs. These studies used a multiple method, multisource approach to provide additional evidence for the reliability and validity of the ASPI. Findings documented inter‐rater reliability of the ASPI across key informants within early childhood educational programs—teachers and teacher assistants. Findings supported concurrent validity of the ASPI with direct observations of preschool classroom adjustment problems and the developmentally salient constructs of temperament and emotion regulation. Implications for policy, practice, and future research are discussed. © 2004 Wiley Periodicals, Inc. Psychol Schs 41: 725–736, 2004.
Synthesis of large, high‐solid‐content latexes by miniemulsion polymerization
Authors: Do Amaral Marcelo , Asua José M. 
Published: July 2004

AbstractMultiple and diverse applications have been recently found for miniemulsions and miniemulsion polymerization. In this work, miniemulsion polymerization is presented as a suitable technique for the preparation of high‐solid‐content latices with large particle sizes. Monomer miniemulsions were prepared with a high‐pressure homogenizer, and droplet sizes of 200–700 nm were obtained. Latexes with particle sizes larger than the sizes commonly accepted for miniemulsion polymerization were obtained. With fixed operational conditions of the homogenizer, the type of stabilizer was the key parameter determining the droplet size and the droplet size distribution. The particle size of the latices obtained by miniemulsion polymerization indicated that the particles were mainly formed by droplet nucleation. Latexes obtained by this process have multiple applications, including use as seeds in the polymerization of high‐solid‐content latices. This article shows that potential new applications for miniemulsion polymerization are far from being exhausted. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4222–4227, 2004
Linear response theory: An alternative to PB and GB methods for the analysis of molecular dynamics trajectories?
Authors: Morreale Antonio , de la Cruz Xavier , Meyer Tim , Gelpí Josep Lluís , Luque F. Javier , Orozco Modesto 
Published: July 2004

AbstractWe explore the use of classical Linear Response Theory (LRT) as an alternative strategy to the use of Molecular Mechanics/Poisson‐Boltzmann strategies to compute the solvation free energy of macromolecules from molecular dynamics simulations using an explicit representation of solvent. The method reproduces well the free energy of solvation of standard amino acid side chains, small peptides, and proteins. The use of a fully discrete representation of solvent avoids the possible problems of continuum models to represent the solvation of systems containing tightly bound water molecules. Proteins 2004. © 2004 Wiley‐Liss, Inc.