bluuebunny/crossref_metadata_2025_split huggingface dataset:
Semicrystalline Lysine Functionalized Precision Polyolefins
Authors: Leonard James K. , Hopkins Timothy E. , Chaffin Kim , Wagener Kenneth B. 
Published: June 2008

AbstractA family of semicrystalline polymers with the amino acid lysine regularly and atactically attached along a polyethylene backbone has been prepared via metathesis polymerization. The lysine branches are placed precisely on every 21st carbon of the polyethylene backbone giving these polymers a perfectly known architecture. Attachment of the amino acid is varied either by using a succinic acid spacer or directionally through its C‐ or N‐terminus. Changes in physical and spectral properties are discussed as a direct consequence of the nature of the amino acid connection and structure. The crystallinity of these polymers is studied by differential scanning calorimetry (DSC) and wide angle X‐ray scattering (WAXS), where it has become clear that the crystalline unit cell resembles that of the pure monomer. Long range order was absent as shown by small angle X‐ray scattering (SAXS). Complete deprotection of the amine branch of the lysine moiety of one polymer is discussed both in terms of procedure and its subsequent effect on the material's crystallinity.magnified image
High Molecular Weight Poly(ε‐caprolactone) by Initiation with Triphenyl Bismuth
Authors: Kricheldorf Hans R. , Behnken Gesa , Schwarz Gert , Brockaert Josè A. 
Published: June 2008

AbstractRing‐opening polymerizations of ε‐caprolactone (εCL) were conducted in bulk at 120 °C with triphenyl bismuth, Ph3Bi, as an initiator or catalyst. Variation of the monomer–initiator ratio (M/I) allowed for a variation of the molecular weight, but not an accurate control. With an M/I ratio of 1 000:1 and ultra‐dry εCL, a number average molecular weight (corrected $\overline M _{\rm n}$) of 285 kDa was obtained corresponding to a degree of polymerization around 2 500. Addition of tetra(ethylene glycol) resulted in incorporation of this coinitiator and allowed for a better control of the molecular weight. Time–conversion curves revealed a long induction period followed by a conspicuous acceleration upon addition of a coinitiator (tetraethylene glycol). Model experiments demonstrated that Ph3Bi is unstable at 120 °C in the presence of water, oxygen, or alcohols and slowly a precipitate is formed which mainly consists of (PhBiO)x. Ph2BiOR groups formed by side reactions seem to be the true initiators.magnified image
Contrast Inversion in TEM Studies of Poly(ferrocenylsilane)‐block‐Poly(dimethylsiloxane) Diblock Copolymers
Authors: Wang Yishan , Coombs Neil , Manners Ian , Winnik Mitchell A. 
Published: June 2008

AbstractThis paper describes an unusual contrast inversion phenomenon in TEM imaging of PFS‐b‐PDMS block copolymer bulk samples. It is clearly observed especially in samples that show a lamellar morphology that the contrast inversion is accompanied by a contraction of the PDMS domains and an expansion of the Fe‐rich domains. The location of the iron‐ and silicon‐rich domains was monitored by EDX analysis. We infer that the contrast inversion was caused by electron beam radiation‐induced damage to, and possible cross‐linking of, PDMS chains. A simple way to selectively deposit metal on electron beam patterned polymer film was demonstrated.magnified image
Iron(III)‐Mediated ATRP of Methyl Methacrylate Using Activators Generated by Electron Transfer
Authors: Zhang Lifen , Cheng Zhenping , Tang Fan , Li Qiang , Zhu Xiulin 
Published: June 2008

AbstractA novel procedure, atom‐transfer radical polymerization using activators generated by electron transfer (AGET ATRP) mediated by iron catalyst, was developed, using an oxidatively stable FeCl3/triphenylphosphine as a catalyst complex, ascorbic acid as a reducing agent, and methyl methacrylate as a monomer. The polymerization can be conducted successfully in the presence of a limited amount of air and shows the features of “living”/controlled free‐radical polymerizations such as number‐average molecular weights increasing linearly with monomer conversion and narrow molecular weight distributions. The living feature of the obtained polymer was further verified by a chain extension experiment.magnified image
PBA–PMMA 3‐Arm Star Block Copolymer Thermoplastic Elastomers
Authors: Dufour Bruno , Koynov Kaloian , Pakula Tadeusz , Matyjaszewski Krzysztof 
Published: June 2008

AbstractA series of well‐defined poly(methyl methacrylate)‐block‐poly(butyl acrylate) 3‐arm star block copolymers have been synthesized by ATRP. The incorporation of polar hard segment of PMMA was made possible with the aid of halogen exchange technique. Phase‐separated morphology of cylindrical PMMA domains hexagonally arranged in the pBA matrix was observed by small angle X‐ray scattering in all studied materials. The mechanical and thermal properties of the PBA–PMMA 3‐arm star block copolymers have been thoroughly characterized and their thermoplastic elastomer behavior was studied. It was found that the tensile properties of these materials are comparable with those of their linear ABA type block copolymer counterparts with similar compositions.magnified image
Phase Transition Behavior and Molecular Orientation of Oligo(9,9′‐dioctylfluorene‐alt‐bithiophene)
Authors: Li Na , Zhang Xiaojie , Geng Yanhou , Su Zhaohui 
Published: June 2008

AbstractA novel conjugated oligomer, oligo(9,9′‐dioctylfluorene‐alt‐bithiophene) (OF8T2), was found to exhibit a unique phase transition between crystalline and liquid‐crystalline states, and a liquid‐crystalline glass was easily generated, offering better TFT device performance. In thin films, upon annealing the OF8T2 molecules oriented preferentially with their planes of conjugation being normal to the substrate, and both film thickness and annealing temperature were critical to the film morphology and the molecular orientation. When the OF8T2 film was deposited on a rubbed polyimide surface and annealed, the molecules aligned their long axes along the rubbing direction.magnified image
Polymer Foams Stabilized by Particles Adsorbed at the Air/Polymer Interface
Authors: Thareja Prachi , Ising Brian P. , Kingston Samuel J. , Velankar Sachin S. 
Published: June 2008

AbstractIn aqueous systems, partially hydrophobic particles are known to stabilize foams even in the absence of any added surfactant. This paper shows that the same principle can be applied to polymeric systems: particles that are partially wetted by a polymer melt can stabilize a foam of that polymer. The foam stability is attributable to the adsorption of the particles at the air/polymer interface. Remarkably, stable foams are realized even from polymers that are liquid at room temperature, and hence are otherwise unfoamable. The implications of this result to practical foaming operations are discussed.magnified image
The modified FitzHugh–Nagumo system as an oscillator
Authors: Rabinovitch A. , Friedman M. 
Published: June 2008

AbstractThe use of the modified FitzHugh–Nagumo system is extended to the limit cycle regime. Ranges of parameters for which such oscillatory behavior prevails are calculated and properties of phase space and individual pulses are obtained. Copyright © 2008 John Wiley & Sons, Ltd.
Regularization of the non‐stationary Schrödinger operator
Authors: Cerejeiras Paula , Vieira Nelson 
Published: June 2008

AbstractIn this paper we prove a Lp‐decomposition where one of the components is the kernel of a first‐order differential operator that factorizes the non‐stationary Schrödinger operator −Δ−i∂t. Copyright © 2008 John Wiley & Sons, Ltd.
Global nonexistence of solutions with positive initial energy for a class of wave equations
Authors: Liu Wenjun , Wang Mingxin 
Published: June 2008

AbstractIn this study, we consider a class of wave equations with strong damping and source terms associated with initial and Dirichlet boundary conditions. We establish a blow up result for certain solutions with nonpositive initial energy as well as positive initial energy. This further improves the results by Yang (Math. Meth. Appl. Sci. 2002; 25:825–833) and Messaudi and Houari (Math. Meth. Appl. Sci. 2004; 27: 1687–1696). Copyright © 2008 John Wiley & Sons, Ltd.
Generalized Hermitean Clifford–Hermite polynomials and the associated wavelet transform
Authors: Brackx Fred , De Schepper Hennie , De Schepper Nele , Sommen Frank 
Published: June 2008

AbstractClifford analysis is a higher‐dimensional function theory offering a refinement of classical harmonic analysis, which has proven to be an appropriate framework for developing higher‐dimensional continuous wavelet transforms, the construction of the wavelets being based on generalizations to a higher dimension of classical orthogonal polynomials on the real line. More recently, Hermitean Clifford analysis has emerged as a new branch of Clifford analysis, offering yet a refinement of the standard Euclidean case; it focusses on so‐called Hermitean monogenic functions, i.e. simultaneous null solutions of two Hermitean Dirac operators. In this Hermitean setting, Clifford–Hermite polynomials and their associated families of wavelet kernels have been constructed starting from a Rodrigues formula involving both Hermitean Dirac operators mentioned. Unfortunately, the property of the so‐called vanishing moments of the corresponding mother wavelets, ensuring that polynomial behaviour in the analyzed signal is filtered out, is only partially satisfied and has to be interpreted with care, the underlying mathematical reason being the fact that the Hermitean Clifford–Hermite polynomials show a too restrictive structure. In this paper, we will remediate this drawback by considering generalized Hermitean Clifford–Hermite polynomials, involving in their definition homogeneous Hermitean monogenic polynomials. The ultimate goal being the construction of new continuous wavelet transforms by means of these polynomials, we first deeply investigate their properties, amongst which are their connection with the traditional Laguerre polynomials, their structure and recurrence relations. Copyright © 2008 John Wiley & Sons, Ltd.
A non‐linear coupled finite element–boundary element model for the prediction of vibrations due to vibratory and impact pile driving
Authors: Masoumi Hamid Reza , François Stijn , Degrande Geert 
Published: June 2008

AbstractThis paper presents a non‐linear coupled finite element–boundary element approach for the prediction of free field vibrations due to vibratory and impact pile driving. Both the non‐linear constitutive behavior of the soil in the vicinity of the pile and the dynamic interaction between the pile and the soil are accounted for.A subdomain approach is used, defining a generalized structure consisting of the pile and a bounded region of soil around the pile, and an unbounded exterior linear soil domain. The soil around the pile may exhibit non‐linear constitutive behavior and is modelled with a time‐domain finite element method. The dynamic stiffness matrix of the exterior unbounded soil domain is calculated using a boundary element formulation in the frequency domain based on a limited number of modes defined on the interface between the generalized structure and the unbounded soil. The soil–structure interaction forces are evaluated as a convolution of the displacement history and the soil flexibility matrices, which are obtained by an inverse Fourier transformation from the frequency to the time domain. This results in a hybrid frequency–time domain formulation of the non‐linear dynamic soil–structure interaction problem, which is solved in the time domain using Newmark's time integration method; the interaction force time history is evaluated using the θ‐scheme in order to obtain stable solutions.The proposed hybrid formulation is validated for linear problems of vibratory and impact pile driving, showing very good agreement with the results obtained with a frequency‐domain solution. Linear predictions, however, overestimate the free field peak particle velocities as observed in reported field experiments during vibratory and impact pile driving at comparable levels of the transferred energy. This is mainly due to energy dissipation related to plastic deformations in the soil around the pile. Ground vibrations due to vibratory and impact pile driving are, therefore, also computed with a non‐linear model where the soil is modelled as an isotropic elastic, perfectly plastic solid, which yields according to the Drucker–Prager failure criterion. This results in lower predicted free field vibrations with respect to linear predictions, which are also in much better agreement with experimental results recorded during vibratory and impact pile driving. Copyright © 2008 John Wiley & Sons, Ltd.
Bending of fluid‐saturated linear poroelastic beams with compressible constituents
Authors: Wang Zhi‐Hua , Prévost Jean H. , Coussy Olivier 
Published: June 2008

AbstractAnalytical solutions are presented for fluid‐saturated linear poroelastic beams under pure bending. The stress‐free boundary condition at the lateral surfaces is satisfied in the St Venant's sense and the Beltrami–Michell compatibility conditions are resolved rigorously, rendering the flexure of the beams analytically tractable. Two sets of formulations are derived based on the coupled and uncoupled diffusion equations respectively. The analytical solutions are compared with three‐dimensional finite element simulations. Both sets of analytical formulations are capable of capturing exactly both the initial (undrained) and the steady‐state (fully drained) deflection of the beams. However, the analytical solutions are found to be deficient during the transient phase. The cause for the deficiency of the transient analytical solutions is discussed. The accuracy of the analytical solutions improves as Poisson's ratio and the compressibility of the constituents of the porous beam increase, where the St Venant's edge effect at the lateral surfaces is mitigated. Copyright © 2008 John Wiley & Sons, Ltd.
Proton imaging of siloxanes to map tissue oxygenation levels (PISTOL): a tool for quantitative tissue oximetry
Authors: Kodibagkar Vikram D. , Wang Xianghui , Pacheco‐Torres Jesús , Gulaka Praveen , Mason Ralph P. 
Published: June 2008

AbstractHexamethyldisiloxane (HMDSO) has been identified as a sensitive proton NMR indicator of tissue oxygenation (pO2) based on spectroscopic spin‐lattice relaxometry. A rapid MRI approach has now been designed, implemented, and tested. The technique, proton imaging of siloxanes to map tissue oxygenation levels (PISTOL), utilizes frequency‐selective excitation of the HMDSO resonance and chemical‐shift selective suppression of residual water signal to effectively eliminate water and fat signals and pulse‐burst saturation recovery 1H echo planar imaging to map T1 of HMDSO and hence pO2. PISTOL was used here to obtain maps of pO2 in rat thigh muscle and Dunning prostate R3327 MAT‐Lu tumor‐implanted rats. Measurements were repeated to assess baseline stability and response to breathing of hyperoxic gas. Each pO2 map was obtained in 3½ min, facilitating dynamic measurements of response to oxygen intervention. Altering the inhaled gas to oxygen produced a significant increase in mean pO2 from 55 Torr to 238 Torr in thigh muscle and a smaller, but significant, increase in mean pO2 from 17 Torr to 78 Torr in MAT‐Lu tumors. Thus, PISTOL enabled mapping of tissue pO2 at multiple locations and dynamic changes in pO2 in response to intervention. This new method offers a potentially valuable new tool to image pO2 in vivo for any healthy or diseased state by 1H MRI. Copyright © 2008 John Wiley & Sons, Ltd.
Influence of Fe‐MMT on the fire retarding behavior and mechanical property of (ethylene‐vinyl acetate copolymer/magnesium hydroxide) composite
Authors: Zhang Yi , Hu Yuan , Song Lei , Wu Jing , Fang Shoulin 
Published: June 2008

AbstractIn this work, Fe‐montmorillonite (Fe‐MMT) is synthesized and used as a synergistic agent in ethylene vinyl acetate/magnesium hydroxide (EVA/MH) flame retardant formulations. The synergistic effect of Fe‐MMT with magnesium hydroxide (MH) as the halogen‐free flame retardant for ethylene vinyl acetate (EVA) is studied by thermogravimetric analysis (TGA), limiting the oxygen index (LOI), UL‐94, and cone calorimetry test. Compared with that of Na‐MMT, it indicates that the synergistic effects of Fe‐MMT enhance the LOI value of EVA/MH polymer and improve the thermal stability and reduce the heat release rate (HRR). The structure and morphology of nanocomposites are studied by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The mechanical properties of the EVA composites have also been studied here, indicating that the use of Fe‐MMT reduces the amount of inorganic fillers. MH hence enhances the mechanical properties of the EVA composite while keeping the UL‐94 V‐0 rating. Copyright © 2008 John Wiley & Sons, Ltd.
Effects of surfactant and molecular weight of polyol on grating formation and switching of holographic PDLC
Authors: Shim S. S. , Woo J. Y. , Kim K. H. , Kim B. K. 
Published: June 2008

AbstractThe interposition of surfactants between polymer and liquid crystal (LC) droplets was theoretically predicted by the positive spreading coefficient (0 < λ31) and utilized to interpret the morphology, grating formation kinetics, diffraction efficiency, and switching of the holographic polymer dispersed liquid crystal (HPDLC), prepared from various types (octanoic acid, poly oxyethylene octyl phenyl ether, and perfluoro‐1‐butanesulfonyl fluoride) and amounts (0–9 wt%) of surfactant and molecular weights of polyol (PPG). Regardless of the surfactant type, diffraction efficiency increased with the addition and increasing amount of surfactant, a tendency consistent with increasing value of spreading coefficient, which is determined by the formulations of grating formation. In contrast, diffraction efficiency showed a maximum with the polypropylene glycol (PPG) molecular weight. Surfactant effectively reduced the anchoring energy and electrically drove the film which otherwise was not driven. Overall, surfactant with greater λ31 gave smaller droplet, greater diffraction efficiency, driving voltage, contrast ratio, and smaller response time. Copyright © 2008 John Wiley & Sons, Ltd.
5α‐Reduktase‐Inhibitoren – Benigne Prostatahyperplasie und vieles mehr. BPH, Alopezie und Co.
Authors: Holzgrabe Ulrike , Bennack Edith 
Published: June 2008

AbstractDie 5α‐Reduktase‐Inhibitoren Finasterid und Dutasterid können bei der BPH gleichwertig eingesetzt werden. Manche Leitlinien sehen allerdings α‐Blocker den 5α‐Reduktase‐Inhibitoren überlegen. In der Studie von McConnell et al. gibt es Hinweise, dass eine Kombinationstherapie aus dem α‐Blocker Doxazosin und dem 5α‐Reduktase‐Inhibitor Fina‐sterid einer Einzeltherapie überlegen ist. Allerdings scheinen die Kosten deutlich höher als der Nutzen zu sein.
Energy loss of swift H and He projectiles in Al, Si, Ni and Cu targets
Authors: Denton Cristian D. , Abril Isabel , Moreno‐Marín Juan Carlos , Heredia‐Avalos Santiago , Garcia‐Molina Rafael 
Published: June 2008

AbstractWe have calculated the stopping power of Al, Si, Ni and Cu for swift H and He ion beams. Furthermore, the energy loss straggling corresponding to Ni is also evaluated. The dielectric formalism is used combined with the MELF‐GOS method, which describes the energy loss function of the target by a linear combination of Mermin type energy loss functions for the electron outer‐shell electrons and by generalized oscillator strengths for the electron inner‐shell electrons. We take into account the corrections to the stopping power associated to capture and loss of electrons by the projectile as well as the polarization of the projectile charge density. The versatility of this method is illustrated by the good agreement between their predictions and the experimental results, which is observed for a wide range of projectile energies and targets with different electronic properties. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ab initio study of hydrogen chemical adsorption on platinum surface/carbon nanotube join system
Authors: Fedorov Alexander S. , Sorokin Pavel B. , Kuzubov Alexander A. 
Published: June 2008

AbstractThe process of hydrogen chemical adsorption on platinum cluster/single wall carbon nanotube (CNT) join surfaces is modelled at various temperatures and pressures. For that, the adsorption energy of hydrogen atoms on surfaces of both platinum (111) plate and CNT (5,5) or (8,8) types is calculated by density functional theory with the PBE approximation. At various temperatures the hydrogen atom hopping rate on both platinum and CNT surfaces is calculated by the transition state theory. Furthermore the hydrogen hopping rate from the platinum surface to the attached nanotube is obtained by calculation of the total energy profile. It is proved that hydrogen atoms can migrate easily at the platinum surface at all temperatures, but at the CNT surface they can migrate beginning at 400–500 K. By calculation of chemical potentials of hydrogen in gas or on CNT or platinum cluster surfaces the equilibrium density of adsorbed hydrogen was calculated at different temperatures and pressures. It is established that for all temperatures in the range 300–900 K and for all pressures less than 500 bar, the hydrogen is dissociated and chemically adsorbed on the platinum surface very effectively, but surface site occupation by hydrogen on attached CNT surface is rather small. But if CNT vacancies are present in the tube structure and the temperature is lower then 450 K, hydrogen atoms can be adsorbed effectively enough on these vacancies. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface and interface structural analysis of VOX/TiO2 (110) by X‐ray photoelectron diffraction
Authors: Miyasaka Shinya , Amano Kentaro , Nojima Masashi , Owari Masanori , Nihei Yoshimasa 
Published: June 2008

AbstractWe have studied the atomic structure of the surface and interface of VOX/TiO2 (110) by X‐ray photoelectron diffraction (XPED). The TiO2 (110) crystal surface was cleaned by cycles of Ar+ sputtering followed by annealing. The TiO2 (110) crystal surface was deoxidized by annealing. Therefore, TiO2 (110) crystal surface was annealed in oxygen atmosphere. Vanadium oxides were deposited by two processes. In process A, vanadium was first deposited on the TiO2 crystal and then oxidized in an O2 atmosphere. In process B, vanadium was deposited in an atmosphere of low‐pressure O2. We characterized the VOX ultrathin film grown on the TiO2 (110) surface by low‐energy electron diffraction (LEED), X‐ray photoelectron spectroscopy (XPS), and XPED. Finally the surface and interface structures of the VOX/TiO2 (110) were clarified by using the multiple scattering cluster model with spherical wave (MSC‐SW) method and a reliability factor R(R factor). Copyright © 2008 John Wiley & Sons, Ltd.
Thermal evolution of Co islands on Ag/Si(111)‐√3 × √3 and Ag/Ge(111)‐√3 × √3 surfaces
Authors: Tsay Sung‐Lin , Kuo Chang‐Yu , Lin Chun‐Liang , Chen Wen‐Chen , Fu Tsu‐Yi 
Published: June 2008

AbstractThermal evolution of Co islands on Ag/Ge(111)‐√3 × √3 and Ag/Si(111)‐√3 × √3 surfaces was studied by scanning tunneling microscopy (STM) and low‐energy electron diffraction (LEED). Ag‐√3 × √3 buffer layer can avoid alloy formation of Co and Si or Ge below the annealing temperature 500 °C. The growth behavior of Co on Ag/Si(111)‐√3 × √3 surfaces is very different from that on Ag/Ge(111)‐√3 × √3 surfaces, although both the √3 structures can be classified as honeycomb chain trimer (HCT) model. Submonolayer Co on Ag/Si(111)‐√3 × √3 surfaces prefer to form clusters below 500 °C. However, Co clusters nucleate and construct two‐dimensional islands (2D islands) on Ag/Ge(111)‐√3 × √3 surfaces after annealing to 300 °C. The result of different growth behavior comes from two major factors. One is antiphase boundaries (APBs) with extra electron states, which trap Co clusters on Ag/Si(111)‐√3 × √3 surfaces. The other is the strong binding force that exists between Ge and Co atoms to cause the formation of Co period islands on Ag/Ge(111)‐√3 × √3 surfaces. Copyright © 2008 John Wiley & Sons, Ltd.