bluuebunny/crossref_metadata_2025_split huggingface dataset:
Na+ and Mg2+ Ion Effect on the Stability of a Poly I · Poly A · Poly I Triple Helix
Authors: Sorokin Victor A. , Valeev Vladimir A. , Andrus Elena A. , Gladchenko Galina O. , Blagoi Yuri P. 
Published: May 2004

AbstractSummary: Differential UV spectroscopy was used to study the temperature dependence of the conformational equilibrium in aqueous poly I · poly A · poly I (A2I) solutions containing Na+ (0.1–2 M) and Mg2+ (10−5–0.005 M) ions. Over the whole range of the studied Na+ and Mg2+ concentrations, the heating‐induced destruction of the triple A2I helix is actually the A2I → A + I + I (3 → 1) transition. The rise of the transition temperature with increasing Na+ and Mg2+ contents is well described by Manning's and the “ligand” theories, which makes it possible to estimate the linear charge density on the single‐stranded poly I (ξ = 1.9 ± 0.1) and the Mg2+–A2I binding constant (K = 1 250 M−1 for the zero degree of binding). An analytical expression has been obtained, which correlates the constants of Mg2+ binding to three‐ and single‐stranded polynucleotides (K3 and K1, respectively) and the linear charge density on them. There are only minor distinctions between the K3 values for A2U and A2I because these polynucleotides have similar structures. The difference in the K1 values is also slight as single‐stranded poly U, poly I, and poly A have similar conformations.Dependence of the conformational transition temperatures of two triple helices with changing Mg2+ concentration.imageDependence of the conformational transition temperatures of two triple helices with changing Mg2+ concentration.
Synthesis and Characterization of Epoxidized Styrene‐Butadiene Block Copolymers as Templates for Nanostructured Thermosets
Authors: Serrano Elena , Larrañaga Maider , Remiro Pedro M. , Mondragon Iñaki , Carrasco Pedro M. , Pomposo Jose A. , Mecerreyes David 
Published: May 2004

AbstractSummary: A wide range of epoxidized styrene‐block‐butadiene block copolymers were synthesized using hydrogen peroxide in the presence of an in situ prepared methyltrioctylammoniumtetrakis(diperoxotungstate)phosphate as the catalyst system in a water/dichloroethane biphasic system. 1H NMR and FT‐IR spectra revealed that the epoxidation procedure led mainly to 1,4‐epoxidized butadiene units. GPC analysis showed that epoxidation changed the copolymer architecture into stars with fewer arms. The copolymers showed two glass transition temperatures in accordance with the phase separation for block copolymers and, as revealed in AFM images, the self‐assembly takes place on a nanometer scale. Moreover, epoxidized styrene‐butadiene (SB) copolymers showed improved miscibility with epoxy monomers leading to self‐assembled nanostructures in the uncured state. This allows them to be used as templates for nanostructured resins.TM‐AFM phase images for: a) 40 mol‐% epoxidized copolymer (scale bar = 300 nm); b) uncured blend containing 50 wt.‐% DGEBA in 50 mol‐% epoxidized copolymer (scale bar = 1 μm), after annealing at 80 °C in vacuum for 3 h.imageTM‐AFM phase images for: a) 40 mol‐% epoxidized copolymer (scale bar = 300 nm); b) uncured blend containing 50 wt.‐% DGEBA in 50 mol‐% epoxidized copolymer (scale bar = 1 μm), after annealing at 80 °C in vacuum for 3 h.
Immiscible Poly(L‐lactide)/Poly(ε‐caprolactone) Blends: Influence of the Addition of a Poly(L‐lactide)‐Poly(oxyethylene) Block Copolymer on Thermal Behavior and Morphology
Authors: Maglio Giovanni , Malinconico Mario , Migliozzi Anna , Groeninckx Gabriel 
Published: May 2004

AbstractSummary: A binary blend of poly (L‐lactide) (PLLA) and poly(ε‐caprolactone) (PCL) of composition 70:30 by weight was prepared using a twin screw miniextruder and investigated by differential scanning calorimetry (DSC), optical microscopy and scanning electron microscopy (SEM). Ternary 70:30:2 blends were also obtained by adding either a diblock copolymer of PLLA and poly(oxyethylene) (PEO) or a triblock PLLA‐PCL‐PLLA copolymer as a third component. Optical microscopy revealed that the domain size of dispersed PCL domains is reduced by one order of magnitude in the presence of both copolymers. SEM confirmed the strong reduction in particle size upon the addition of the copolymers, with an indication of an enhanced emulsifying effect in the case of the PLLA‐PEO copolymer. These results are analyzed on the basis of solubility parameters of the blend components.Optical micrograph of M3EG2 blend melt quenched at 125 °C.imageOptical micrograph of M3EG2 blend melt quenched at 125 °C.
Synthesis of Poly(ester‐anhydrides) Based on Different Polyester Precursors
Authors: Korhonen Harri , Helminen Antti O. , Seppälä Jukka V. 
Published: May 2004

AbstractSummary: Poly(ester‐anhydrides) were synthesised from poly(L‐lactide), poly(D,L‐lactide), and poly(ε‐caprolactone) prepolymers prepared by ring‐opening polymerisation of cyclic esters in the presence of 1,4‐butanediol or ricinoleic acid as co‐initiator. The hydroxyl group end functionality of the prepolymers was converted to carboxylic acid functionality by reaction with succinic anhydride, and the polyester precursors were coupled by melt polycondensation to give poly(ester‐anhydrides). 1,4‐Butanediol was used as co‐initiator to study the properties of poly(ester‐anhydrides) prepared from different monomers, whereas ricinoleic acid was used as co‐initiator to introduce a hydrophobic fatty acid moiety to the polyester precursor. In hydrolysis tests, the poly(ester‐anhydrides) showed a two‐stage degradation comprising a rapid hydrolysis of anhydride linkages within three days, followed by the slower hydrolysis of the remaining polyester oligomer. Weight loss of the poly(ester‐anhydrides) depended most importantly on molecular weight and thermal properties of the polyester precursors; thus, poly(ester‐anhydrides) prepared from low molecular weight prepolymers having thermal transitions below 37 °C showed very fast weight loss.image
Mechanical Behavior and Fracture Toughness of Poly(L‐lactic acid)‐Natural Fiber Composites Modified with Hyperbranched Polymers
Authors: Wong Susan , Shanks Robert A. , Hodzic Alma 
Published: May 2004

AbstractSummary: The use of hyperbranched polymers (HBP) with hydroxy functionality as modifiers for poly(L‐lactic acid) (PLLA)‐flax fiber composites is presented. HBP concentrations were varied from 0 to 50% v/v and the static and dynamic tensile properties were investigated along with interlaminar fracture toughness. Upon addition of HBP, the tensile modulus and dynamic storage modulus (E′) both diminished, although a greater decline was noticed in the static modulus. The elongation of the composites with HBP showed a pronounced increase as large as 314% at 50% v/v HBP. The loss factor (tan δ) indicated a lowering of the glass transition temperature (Tg) due to a change in crystal morphology from large, mixed perfection spherulites to finer, smaller spherulites. The change in Tg could have also resulted from some of the HBP being miscible in the amorphous phase, which caused a plasticizing effect of the PLLA. The interlaminar fracture toughness measured as the critical strain energy release rate (GIC) was significantly influenced by HBP. At 10% v/v HBP, GIC was at least double that of the unmodified composite and a rise as great as 250% was achieved with 50% v/v. The main factor contributing to high fracture toughness in this study was better wetting of the fibers by the matrix when the HBP was present. With improved ductility of the matrix, it caused ductile tearing along the fiber‐matrix interface during crack propagation.ESEM photograph of propagation region of the interlaminar fracture toughness specimens with 30% v/v of HBP.imageESEM photograph of propagation region of the interlaminar fracture toughness specimens with 30% v/v of HBP.
Phenolic Hyperbranched Polymers as Additives in Cationic Photopolymerization of Epoxy Systems
Authors: Sangermano Marco , Priola Aldo , Malucelli Giulio , Bongiovanni Roberta , Quaglia Andrea , Voit Brigitte , Ziemer Antje 
Published: May 2004

AbstractSummary: A phenolic group containing hyperbranched polyester (HBP) was synthesized and employed as chain transfer agent in cationic photopolymerization of a biscycloaliphatic epoxy monomer (CE). The epoxy group conversion increases by increasing the amount of HBP in the photocurable resin, due to a chain transfer reaction involving the phenolic‐OH groups. HBP acts as a plasticizer inducing decrease of the Tg values together with an increase of the toughness properties. Meanwhile gel content increases together with the E′ values. By increasing the amount of HBP in the photocurable resin an increase of the density is evident indicating a decrease of free volume. Therefore an improvement of the gas barrier properties might be expected; at the same time an increase of the thermal stability is evident.image
Physical and Mechanical Interfacial Properties of Epoxy Copolymers Initiated by Latent Thermal Catalysts
Authors: Park Soo‐Jin , Kang Jun‐Gil , Kwon Soo‐Han 
Published: May 2004

AbstractSummary: The epoxy copolymers containing sulfone groups, diglycidyl ether of bisphenol‐A – Bisphenol‐S (DGEBA‐S) were synthesized by a hot‐melt method. The thermal properties of the epoxy systems initiated by two cationic latent catalysts, i.e., N‐benzylpyrazinium hexafluoroantimonate (BPH) and N‐benzylquinoxalinium hexafluoroantimonate (BQH), were investigated by using a dynamic DSC, DMA, and TGA. The mechanical properties were measured by single‐edge‐notched (SEN) beam fracture toughness tests. As a result, the thermal stability and mechanical interfacial properties of the DGEBA‐S/catalyst system were found to be higher than those of the DGEBA/catalyst. This was probably due to the fact that the introduction of sulfone groups with a polar nature to the main chain of the epoxy resins led to an improvement of thermal stability and toughness of the cured epoxy copolymers.Conversion of the epoxy/catalyst systems as a function of curing temperature.imageConversion of the epoxy/catalyst systems as a function of curing temperature.
Large Scale Fractionation of Macromolecules
Authors: Eckelt John , Haase Tanja , Loske Stefan , Wolf Bernhard A. 
Published: May 2004

AbstractSummary: Access to sufficiently large amounts of material with adequate molecular and chemical uniformity from polydisperse natural products or synthetic materials has been a long‐standing challenge to polymer scientists. We have developed a broadly applicable preparative fractionation method consisting of a special kind of continuous extraction removing the easier soluble components from the initial product. It is rendered possible by the use of spinning nozzles through which a concentrated polymer solution is pressed into a liquid of tailored thermodynamic quality. The initially produced jets of the source phase disintegrate rapidly into minute droplets of typically 50 μm diameter. This efficient subdivision provides the large surfaces and short routs of transport required for successful fractionation. Thus the pronounced kinetic hindrances resulting from the high viscosities of reasonable concentrated polymer solutions can be overcome. We portray the principal features of continuous spin fractionation and present two examples of practical importance.Functional principle of ‘continuous spin fractionation’ (CSF).imageFunctional principle of ‘continuous spin fractionation’ (CSF).
The Estimation of the Molecular Weight of Polytetrafluoroethylene Based on the Heat of Crystallisation. A Comment on Suwa's Equation
Authors: Lappan Uwe , Geißler Uwe , Häußler Liane , Pompe Gisela , Scheler Ulrich 
Published: May 2004

AbstractSummary: The influence of number‐average molecular weight $\overline M _{\rm n}$ ranging from 1.4 · 104 to 1.2 · 106 g/mol on the thermal behaviour of polytetrafluoroethylene (PTFE) has been studied. Samples have been prepared by radiation‐induced degradation of commercial PTFE. The molecular weight $\overline M _{\rm n}$ has been calculated using end‐group concentration determined by infrared (IR) spectroscopy and 19F solid‐state nuclear magnetic resonance (NMR) spectroscopy. Melting and crystallisation heats were investigated by differential scanning calorimetry (DSC). The results have been discussed with respect to quantitative relationships between number‐average molecular weight and heat of crystallisation of PTFE described in the literature. The molecular weight calculated from Suwa's equation, which is often used in the literature, has been found to be too low.Concentration of end‐groups and the molecular weight of PTFE versus the irradiation dose.imageConcentration of end‐groups and the molecular weight of PTFE versus the irradiation dose.
A New Approach to the Evaluation of Stabilizer Efficiency Under Photo‐Ageing
Authors: Kumar Ashustosh , Commereuc Sophie , Verney Vincent , Lajoie Pierre , Lacoste Jacques 
Published: May 2004

AbstractSummary: Elastomers are very sensitive to oxidative degradation due to the combined effect of light and oxygen. Hence, we investigate the impact of stabilizers on the evolution of molecular structure of elastomers through photo‐oxidation. While a dual processes is generally reported to describe photo‐oxidation of elastomers (oxidation by‐products formation and crosslinking), the aim of the current study is to provide a complete characterization of the efficiency of additives taking into account the dual processes: chemical changes (formation of photoproducts) and molecular structure changes (crosslinking). This work gives new insights about relationships between chemical changes and physical properties evolution of the material through ageing. We conclude that the two phenomenon are correlated to the primary peroxidation reaction and a dual efficiency does not exist for any additive.Kinetic curves of carbonylated by‐products formation upon photooxidation of stabilized EPDM films comparing with a unstabilized reference.imageKinetic curves of carbonylated by‐products formation upon photooxidation of stabilized EPDM films comparing with a unstabilized reference.
Essential Work of Fracture Parameters of in‐situ Microfibrillar Poly(ethylene terephthalate)/Polyethylene Blend: Influences of Blend Composition
Authors: Li Zhong‐Ming , Yang Wei , Huang Rui , Fang Xiang‐Ping , Yang Ming‐Bo 
Published: May 2004

AbstractSummary: An in‐situ microfibrillar blend based on poly(ethylene terephthalate) (PET) and polyethylene (PE) was fabricated through slit die extrusion, hot‐stretching and quenching. The morphology of the PET in‐situ microfibers, which were observed after the matrix was etched away, appears to be dependent on the blend composition at a fixed hot stretch ratio. The well‐defined in‐situ fibers were generated at the PET concentrations ranging from 15 to 25 wt.‐%. The fracture toughness of the microfibrillar blend was evaluated using deeply double‐edge notched tension (DDENT) specimens according to the essential work of fracture procedure. Initially, the increase of PET concentration makes we rise. At 15 wt.‐% of PET concentration there exists a maximum we. Further increase of PET microfibers causes a rapid decrease of we. On the other hand, incorporation of PET microfibers at a low concentration to PE makes wp rise slightly. As it exceeds 10 wt.‐%, wp decreases substantially. It was believed that the characteristics of the PET microfibers were responsible for the fracture behaviors of the microfibrillar blend.Morphology of PET microfibers in the PET/PE microfibrillar blend in which the matrix PE was etched away by hot xylene.imageMorphology of PET microfibers in the PET/PE microfibrillar blend in which the matrix PE was etched away by hot xylene.
On the Navier‐Stokes equation with boundary conditions based on vorticity
Authors: Bellout Hamid , Neustupa Jiří , Penel Patrick 
Published: May 2004

AbstractWe treat the Stokes and the Navier‐Stokes equation with the conditions curlku · n = 0 (k = 0, 1, 2) on the boundary of the flow field. The approach is based on a spectral analysis and properties of operator curl. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exterior stationary Navier‐Stokes flows in 3D with non‐zero velocity at infinity: approximation by flows in bounded domains
Authors: Deuring Paul , Kračmar Stanislav 
Published: May 2004

AbstractWe consider stationary incompressible Navier‐Stokes flows in an exterior domain ℝ3\$ \bar \Omega $, where Ω ⊂ ℝ3 is bounded and open. Under the assumption that the velocity at infinity is non‐zero, we present a variational problem in BR\$ \bar \Omega $ such that a solution of this variational problem approximates the given exterior flow. The error associated with this approximation is estimated in terms of R, among other quantities. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Solutions of the Navier‐Stokes initial value problem in weighted Lq‐spaces
Authors: Fröhlich Andreas 
Published: May 2004

AbstractThe problem of strong solvability of the nonstationary Navier‐Stokes equations is considered in weighted Lq‐spaces Lqω(Ω), where the domain Ω ⊂ ℝn is the half space ℝn+ or a bounded domain with boundary of class C1,1 and the weight ω belongs to the Muckenhoupt class Aq. We give general conditions on the weight function ensuring the existence of a unique strong solution at least locally in time. In particular, these conditions admit weight functions ω ∈ Aq, which become singular at the boundary or, in the case Ω = ℝn+, grow for |x| →∞. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Biorthogonal wavelet bases for the boundary element method
Authors: Harbrecht Helmut , Schneiderd Reinhold 
Published: May 2004

AbstractAs shown by Dahmen, Harbrecht and Schneider [7, 23, 32], the fully discrete wavelet Galerkin scheme for boundary integral equations scales linearly with the number of unknowns without compromising the accuracy of the underlying Galerkin scheme. The supposition is a wavelet basis with a sufficiently large number of vanishing moments. In this paper we present several constructions of appropriate wavelet bases on manifolds based on the biorthogonal spline wavelets of A. Cohen, I. Daubechies and J.‐C. Feauveau [4]. By numerical experiments we demonstrate that it is worthwhile to spent effort on their construction to increase the performance of the wavelet Galerkin scheme considerably. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On a class of nonlinear cross‐correlation equations
Authors: v. Wolfersdorf Lothar , Wegert Elias 
Published: May 2004

AbstractNonlinear cross‐correlation equations in finite and semi‐infinite intervals are studied by means of Fourier transform and Cauchy integral techniques. The equations are reduced to a bilinear conjugacy problem for two analytic functions on the real axis which can be solved in explicit form.In particular, Engibaryan's equations from nonlinear factorization theory of Wiener‐Hopf integral equations are treated in more complete manner than in the previous literature. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cover Picture: Macromol. Rapid Commun. 9/2004
Authors: Kohli Neeraj , Dvornic Petar R. , Kaganove Steven N. , Worden Robert M. , Lee Ilsoon 
Published: May 2004

Cover: The picture shows multiple levels of structural order within micropatterned arrays of cross‐linkable, amphiphilic, dendrimer multilayers. The microcontact printing method allowed the film thickness of the nanostructured dendrimer arrays to be controlled.Further details can be found in the Communication by N. Kohli, P. R. Dvornic, S. N. Kaganove, R. M. Worden, and I. Lee* on page 935.
Application of Fourier transform ion cyclotron resonance mass spectrometry to oligosaccharides
Authors: Park Youmie , Lebrilla Carlito B. 
Published: May 2004

AbstractThe application of Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) to the structural elucidation of oligosaccharides is described. This review covers the analyses of oligosaccharides in the context of the unique features of FTICR MS and the improvements in instrumentation that make it possible to study this class of compounds. It consists of work performed initially to understand the fundamental aspects of oligosaccharide ionization and unimolecular fragmentation. More recent investigation includes the application of the technique to samples of direct biological origin. Chemical and enzymatic degradation methods in conjunction with mass spectrometry (MS) and the use front‐end methods with FTICR MS are also discussed. The current applications including the characterization of bacterial lipooligosaccharides and phosporylated carbohydrates are described. © 2004 Wiley Periodicals, Inc., Mass Spec Rev 24:232–264, 2005
Non‐subtype‐selective opioid receptor antagonism in treatment of levodopa‐induced motor complications in Parkinson's disease
Authors: Fox Susan , Silverdale Montague , Kellett Mark , Davies Rhys , Steiger Malcolm , Fletcher Nicholas , Crossman Alan , Brotchie Jonathan 
Published: May 2004

AbstractOpioid peptide transmission is enhanced in the striatum of animal models and Parkinson's disease (PD) patients with levodopa‐induced motor complications. Opioid receptor antagonists reduce levodopa‐induced dyskinesia in primate models of PD; however, clinical trials to date have been inconclusive. A double‐blind, placebo controlled, crossover design study in 14 patients with PD experiencing motor fluctuations was carried out, using the non‐subtype‐selective opioid receptor antagonist naloxone. Naloxone did not reduce levodopa‐induced dyskinesia. The duration of action of levodopa was increased significantly by 17.5%. Non‐subtype‐selective opioid receptor antagonism may prove useful in the treatment of levodopa‐related wearing‐off in PD but not in dyskinesia. © 2003 Movement Disorder Society
Mitochondrial complex I and IV activities in leukocytes from patients with parkin mutations
Authors: Müftüoglu Meltem , Elibol Bülent , Dalmızrak Özlem , Ercan Ayse , Kulaksız Gülnihal , Ögüs Hamdi , Dalkara Turgay , Özer Nazmi 
Published: May 2004

AbstractThe parkin protein functions as a RING‐type ubiquitin protein ligase. Considering the possibility that impaired ubiquitin‐proteosomal system activity may impair antioxidant defenses and enhance oxidative stress, we have investigated the activity of mitochondrial respiratory enzymes in patients with parkin gene mutations. A significant decrease in the leukocyte complex I activity was found both in patients with parkin mutations (62.5%) and idiopathic PD (64.5%) compared with age‐matched controls (P < 0.001). Complex IV activity was also decreased significantly in idiopathic PD patients (60%), but no difference was detected between controls and patients with parkin mutations. © 2003 Movement Disorder Society
Computed tomographically‐controlled injection of botulinum toxin into the longus colli muscle in severe anterocollis
Authors: Herting Birgit , Wunderlich Silke , Glöckler Theresa , Bendszus Martin , Mucha Dirk , Reichmann Heinz , Naumann Markus 
Published: May 2004

AbstractWe report on a 44‐year‐old man who suffered from severe anterocollis. Repeated computed tomographically controlled injections of botulinum toxin into the right longus colli muscle allowed a precise location of the needle and injection of the toxin, leading to clear improvement of symptoms. © 2003 Movement Disorder Society
Unilateral deep brain stimulation of the internal globus pallidus alleviates tardive dyskinesia
Authors: Schrader Christoph , Peschel Thomas , Petermeyer Michael , Dengler Reinhard , Hellwig Dieter 
Published: May 2004

AbstractWe describe a patient with fluspirilene‐induced tardive dyskinesia of the choreiform oro‐facial‐laryngeal type resistant to various conservative approaches for 7 years who underwent deep brain stimulation of the internal pallidal globe. We found immediate and marked suppression of her perioral involuntary movements with unilateral stimulation at 60 Hz. © 2003 Movement Disorder Society