bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of eddies on heat transfer in Couette flow over undulated substrates
Authors: Scholle M. , Thompson H. M. , Aksel Nuri , Gaskell P. H. 
Published: April 2008

AbstractIn Couette flows over undulated substrates eddies can be generated under creeping flow conditions. In contrast to free surface flows on undulated substrates even smooth bottom undulations allow for eddy generation due to the kinematical constraints. The subject of our paper is how these flow patterns interact with the temperature field in non–isothermal flows.Our analysis of the thermo–mechanical coupling is focused on the two dominant effects, namely convection and thermoviscosity, whereas dissipation heat, buoyancy and temperature–dependence of the remaining material parameters are neglected.We solve the problem in two steps: First, the influence of the eddies on the convective heat transfer is considered by solving the heat conduction equation with convection. For the velocity field we take the solution resulting analytically from Reynolds' lubrication approximation for the isothermal flow. The thermoviscous feedback of the resulting temperature field to the flow is considered in forthcoming papers.For the construction of the solution an analytical approach based on a nonorthogonal series representation of the fundamental fields and a variational formulation of the field equations is used. The results are visualised and the physical effects they reveal are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical method for the KdV–Kawahara and Benney–Lin equations
Authors: Sepúlveda Mauricio , Vera Octavio 
Published: April 2008

AbstractWe are concerned with the initial‐boundary‐value problem associated to the Korteweg – de Vries – Kawahara (KdVK) equation and Benney – Lin (BL) equation, which are transport equations perturbed by dispersive terms of 3rd and 5th order and a term of 4th order in the case of (BL) equation. These equations appear in several fluid dynamics problems. We obtain local smoothing effects that are uniform with respect to the size of the interval. We also propose a simple finite‐difference scheme for the problem and prove its stability. Finally, we give some numerical examples. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Controllability of perturbed nonlinear stochastic integrodifferential systems
Authors: Karthikeyan Shanmugasundaram 
Published: April 2008

AbstractThe purpose of this paper is to establish the sufficient conditions concerning the complete controllability of stochastic integrodifferential systems in finite dimensional spaces by using the Banach fixed point theorem. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Finite volume simulation of blood flow through complete bypass models
Authors: Vimmr Jan , Jonášová Alena 
Published: April 2008

AbstractThe presented study introduces the problem of steady blood flow through various idealized bypass models in dependence on several geometrical and flow parameters. The changes in hemodynamics are observed with regard to the occurrence of intimal hyperplasia at the distal anastomosis, which is known to be the main reason for late bypass failure. All numerical simulations were performed using the own developed computational software based on the finite volume method. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New rapid validated HPTLC method for the determination of galanthamine in Amaryllidaceae plant extracts
Authors: Abou‐Donia Amina H. , Toaima Soad M. , Hammoda Hala M. , Shawky Eman 
Published: April 2008

AbstractThe work reported in this paper aims at developing an accurate, specific, repeatable and robust HPTLC method for the determination of galanthamine in different Amaryllidaceae plant extracts. Copyright © 2008 John Wiley & Sons, Ltd.
Novel triterpenoid acyl esters and alkaloids from Anoectochilus roxburghii
Authors: Han Mei‐Hua , Yang Xiu‐Wei , Jin Yan‐Ping 
Published: April 2008

AbstractTwo novel sorghumol acyl esters, sorghumol 3‐O‐Z‐p‐coumarate and sorghumol 3‐O‐E‐p‐coumarate, and a novel alkaloid, anoectochine, were isolated from the whole plants of Anoectochilus roxburghii along with one known triterpenoid, sorghumol. Their structures were established by their detailed spectral studies, including two‐dimensional NMR (1H–1H COSY, HSQC and HMBC). Copyright © 2008 John Wiley & Sons, Ltd.
Crystallization and thermal behavior of multiwalled carbon nanotube/poly(butylenes terephthalate) composites
Authors: Wu Defeng , Wu Liang , Yu Guangcai , Xu Bin , Zhang Ming 
Published: April 2008

AbstractMultiwalled carbon nanotube/poly(butylene terephthalate) composites (PCTs) were prepared by melt mixing. The nonisothermal crystallization and thermal behavior of PCTs were respectively investigated by X‐ray diffractometer, polarized optical microscope, differential scanning calorimeter, dynamic mechanical thermal analyzer, and thermogravimetric analyzer. The presence of nanotubes has two disparate effects on the crystallization of PBT: the nucleation effect promotes kinetics, while the impeding effect reduces the chain mobility and retards crystallization. The kinetics was then analyzed using Ozawa, Mo, Kissinger, Lauritzen‐Hoffman, and Ziabicki model, and the results reveal that the nucleation effect is always the dominant role on the crystallization of PBT matrix. Thus the crystallizability increases with increase of nanotube loadings. In addition, the presence of nanotubes nearly has no remarkable contribution to thermal stability because nanotubes also play two disparate roles on the degradation of PBT matrix: the Lewis acid sites to facilitate decomposition and the physical hindrance to retard decomposition. Hence the nanotubes act merely as inert‐like filler to thermal stability. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Tocopherol‐targeted membrane adsorbents prepared by hybrid molecular imprinting
Authors: Faizal Che Ku M. , Kobayashi Takaomi 
Published: April 2008

AbstractA hybrid molecular imprinting technique for a tocopherol target enabled the preparation of novel membrane adsorbents. α‐Tocopherol methacrylate was used as a functional monomer, and molecular imprinted polymer (MIP) was prepared by copolymerization with divinylbenzene. After the copolymer was granulated, several hybrid molecular imprinted membranes (HMIP) containing the polymer powders were prepared by using polymer scaffolds such as polysulfone (PSf), cellulose acetate (CA), and nylon (Ny). All HMIP membranes prepared by the phase inversion technique showed selective binding of α‐tocopherol (α‐Toc) over its derivative, δ‐tocopherol (δ‐Toc). The imprint efficiencies were 0.49 for the MIP powder and 0.60, 0.64, and 0.53 for the PSf, Ny, and CA‐HMIP systems, respectively. These HMIP membranes retained their binding capacity without losing significant selectivity relative to the MIP powder. Our results demonstrated that the α‐Toc‐imprinted sites were responsible for the selective binding of the target molecules by the HMIP membranes. The membranes' binding behavior was analyzed using Scatchard plots; a heterogeneous distribution of binding sites was observed in both the MIP polymer and HMIP membranes. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Influence of dispersed organophilic montmorillonite at nanometer‐scale on crystallization of poly(L‐lactide)
Authors: Fujimori Atsuhiro , Ninomiya Naoya , Masuko Toru 
Published: April 2008

AbstractWe investigated the effects of surface‐treated organophilic clay on the crystallization of poly(L‐lactide) (PLLA) in their hybrids. The natural nano‐clay in PLLA/clay hybrids acts as a heterogeneous nucleating agent to facilitate crystallization. On the contrary, extensive distributions of induction periods for nucleation are observed in the individual spherulites of neat PLLA and PLLA/organophilic clay hybrids. Therefore, it is suggested that nucleation type of neat PLLA and PLLA/organophilic clay hybrids implies nearly growth geometry as a homogeneous one. Further, under the presence of nano‐clay in their composites, PLLA matrix form the orthorhombic lattice structure corresponded to the α‐form crystal. Since this experimental fact implies little effect of the clay particles on polymorphism of PLLA crystal, the nucleating effect of the organophilic clay seems weaker than the natural clay itself. However, an increase in clay content enhances the growth rates of spherulite for hybrids. Consequently, most of hybrids exhibit an increase in overall crystallization rates at any crystallization temperature in spite of relatively lower nucleation rate of PLLA crystallites itself. In addition, the Avrami exponents (n) obtained by relatively low crystallization temperature ranged from 4 to 6, implying that the growth geometry was dominated sheaf‐like structure in early stage of isothermal crystallization. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Alternating fluorene copolymers containing isothianaphthene derivatives: A study of their aggregation properties and small band gap
Authors: Jung Young Kwan , Kim Hyoseok , Park Jong‐Hwa , Lee Jaemin , Lee Sang Kyu , Lee Yoon Sup , Shim Hong‐Ku 
Published: April 2008

AbstractSeveral fluorene copolymers containing isothianaphthene units (P1, P2, and P3) or similar derivatives (P4 and P5) have been synthesized by Pd‐catalyzed Suzuki polymerization. The monomers containing isothianaphthene were prepared by a ring‐closure reaction with Lawesson's reagent. Strong photoluminescence (PL) quenching in the film state was observed for P1 and P2, which was mainly due to the enhanced quinoid character formed by introducing the isothianaphthene unit. Their energy levels of the compounds were determined using cyclic voltammetry. Among the polymers tested, the polymer containing both an isothianaphthene and a selenophene unit, P2, showed the smallest band gap of 1.85 eV. The influence of structural variation on the band gap of the polymer chains was further investigated by optimizing the geometries of several model monomers. Our results based on the optical and electrochemical properties combined with theoretical calculations showed that polymers containing isothianaphthene have small band gaps, rigid conformations, and strong tendencies to aggregation. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3573–3590, 2008
Electro‐optical behavior of ferroelectric liquid crystalline polyphenylene derivatives
Authors: Suda Kiyoshi , Akagi Kazuo 
Published: April 2008

AbstractLiquid crystalline (LC) polyphenylene derivatives, such as poly(para‐phenylene) (PPP), poly(meta‐phenylene) (PMP), poly(meta‐biphenylene) (PBP), and poly (meta‐terphenylene) (PTP) derivatives, were synthesized through substitution of fluorine‐containing chiral LC groups into side chains, with an aim to develop ferroelectric LC (FLC) conjugated polymers. All the polymers, except PTP, showed enantiotropic liquid crystallinities, where several types of mesophases were observed in both heating and cooling processes. Among them, PPP and PMP derivatives showed chiral smectic C (SC*) phases responsible for ferroelectricity. In fact, they exhibited quick response to electric field, in spite of high viscosities inherent to polymers, giving rise to switching times of less than 1 s between two SC states with reversely directed alignment. Hysteresis loops between the polarization and electric field were also observed for PPP and PMP. The spontaneous polarization (PS) of PMP remained unchanged even after the electric field became zero, affording the residual polarization (PR) whose value was the same as that of PS. This indicates that PMP has a prospective memory function based on FLC nature. The present study is the first report for realizing a quick switching in macroscopic alignment using electric field and also for generating a potential memory function in π‐conjugated polymers. It is elucidated that unusual polymer main chains such as polyphenylenes can be used to prepare new ferroelectric polymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3591–3610, 2008
ROMP based photoinitiator‐coinitiator systems with improved migration stability
Authors: Sandholzer Martina , Schuster Monika , Varga Franz , Liska Robert , Slugovc Christian 
Published: April 2008

AbstractNowadays, migration stability is one of the key features for photoinitiators used in radiation curable formulations, especially when the material is in contact with food or the human body. Herein, the synthesis and characterization of statistical copolymers with covalently bound eosin and/or ethyl dimethylamino benzoate units by ring opening metathesis polymerization is presented. The prepared compounds were tested as macroinitiators for the photopolymerization of acrylates aiming at an initiator/coinitiator system which combines good polymerization activity with improved migration stability. An acrylate modified eosin derivative which is incorporated into the polymer network during the photopolymerization reaction and, therefore, less likely to leak from the polymer compound was used as reference. Photoinitiating activities of low and high molecular weight initiators and coinitiators were investigated by photo‐DSC. Moreover, leakage studies and viability tests with osteoblast‐like cells were performed to proof the suitability of this concept. The use of polymeric eosin in combination with a low molecular weight coinitiator was found to be a good compromise when aiming at a photoinitiating system with sound performance and improved migration stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3648–3661, 2008
Polyfluorenes minimally doped with 1,4‐bis(2‐thienyl‐2‐cyanovinyl)benzene chromophore: Their synthesis, characterization, and application to white‐light‐emitting materials
Authors: Hsieh Bar‐Yuan , Chen Yun 
Published: April 2008

AbstractCopolyfluorenes (PFR1 and PFR2), chemically doped with 0.1 and 0.025 mol % 2,5‐dihexyloxy‐1,4‐bis(2‐thienyl‐2‐cyanovinyl)benzene (MR chromophere) were synthesized by the Suzuki coupling reaction. The PFRs were used to fabricate white‐light‐emitting devices through incomplete energy transfer. Because of the low content of the MR chromophore, the optical, thermal, and electrochemical properties of the PFRs were almost identical to those of polyfluorene, except for their photoluminescent (PL) and electroluminescent (EL) properties. The copolymer films showed PL peaks at about 428 and 570 nm originating from fluorene segments and MR chromophores, respectively. Compared with the model compound (MR), the polymer chains extended the conjugation length of the MR chromophores and exhibited a 20–48 nm red‐shift in the emission band. In addition, the lower LUMO level of the MR (−3.27 eV) was expected to improve the electron injection. The EL devices [ITO/PEDOT:PSS/PFRs/Ca (50 nm)/Al (100 nm)] showed a broad emission band, covering the entire visible region, with chromaticity coordinates of (0.36, 0.35) and (0.32, 0.30) for PFR1 and PFR2 devices, respectively. The emission color of the PFR2 device was very similar to that of a pure white light (0.33, 0.33); and the maximal brightness and current efficiency were 3011 cd/m2 and 1.98 cd/A, respectively, which surpass those found for polyfluorene devices (1005 cd/m2, 0.28 cd/A). A). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3703–3713, 2008
A new donor‐acceptor type polymeric material from a thiophene derivative and its electrochromic properties
Authors: Udum Yasemin Arslan , Yildiz Ersin , Gunbas Gorkem , Toppare Levent 
Published: April 2008

AbstractA new electrochromic polymer, poly(2,3,5,8‐tetra(thiophen‐2‐yl)quinoxaline) (PTTQ), was synthesized electrochemically and its electrochromic properties were investigated. The polymer was characterized by Cyclic Voltammetry, Fourier Transform infrared spectroscopy, UV‐Vis‐NIR Spectroscopy, and colorimetry. Spectroelectrochemistry analysis demonstrated that the polymer can undergo both p‐ and true n‐type doping processes. The polymer, (PTTQ), has three accessible color states: an oxidized transmissive, a neutral light bluish‐green, and a reduced transmissive light gray. Switching ability of the polymer was evaluated by kinetic studies. The polymer revealed an excellent optical contrast of 98% in the NIR region. Outstanding optical contrast in the NIR region, high stability and fast switching times make this polymer an excellent candidate for NIR device applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3723–3731, 2008
Controlled radical polymerization of N‐vinylcaprolactam mediated by xanthate or dithiocarbamate
Authors: Wan Decheng , Zhou Qing , Pu Hongting , Yang Genjin 
Published: April 2008

AbstractControlled radical polymerization of N‐vinylcaprolactam (NVCL) via reversible addition‐fragmentation chain transfer (RAFT) polymerization or macromolecular design via the interchange of xanthate (MADIX) was described, employing 2‐diphenylthiocarbamoylsulfanyl‐2‐methyl‐propionic acid (CTA1), ((O‐ethylxanthyl)methyl)benzene (CTA2) and (1‐(O‐ethylxanthyl)ethyl)benzene (CTA3) as chain transfer agents (CTA). It was found that all the CTAs led to controlled radical polymerization of NVCL, with the molecular weight increased along with the conversion of monomer and a relatively narrow molecular weight distribution could be obtained, as determined with matrix‐assisted laser desorption and ionization time‐of‐flight (MALDI‐TOF) and gel permeation chromatography (GPC), the polydispersity indices, as determined by MALDI‐TOF, were typically on the order of 1.24, but the polymerization did not proceed in a strictly living manner. The chain transfer ability of these CTAs was in the following order: CTA1 ≈ CTA2 < CTA3. MALTI‐TOF measurement showed that the major population of polymer retained the chain‐end functional group, but minor population deactivated by radical coupling. In preparation of the block copolymer of NVCL and vinyl acetate (VAc) by sequential polymerization, the sequence of monomer addition was important. Using VAc as the first monomer could lead to a block copolymer presenting a unimodal GPC trace and a narrow PDI index, and if NVCL was used as the first monomer, the polymerization was less well controlled. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3756–3765, 2008
Slow motion in [ring‐fluoro]polycarbonate by CODEX
Authors: Weldeghiorghis Thomas K. , Stueber Dirk , Schaefer Jacob 
Published: April 2008

AbstractChain dynamics in [ring‐fluoro]polycarbonate (an A‐B alternating copolymer that has a single fluorine substituent on every fourth main chain ring) have been characterized by centerband only detection of exchange (CODEX) and rotating‐frame 13C spin‐lattice relaxation. The slow motions detected by CODEX are facilitated by a mechanically active lattice reorganization that permits a flip of the fluorinated ring about its C2 axis. Nonfluorinated rings undergo small‐amplitude reorientations and C2 flips, both of which are fast and not CODEX active. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1062–1066, 2008
A Novel Device for Single Particle Light Scattering Size Analysis and Concentration Measurement at High Pressures and Temperatures
Authors: Umhauer Heinz , Meyer Jörg , Schiel Annette 
Published: April 2008

AbstractBased on the findings of previous work, a novel instrument was developed for the size analysis and concentration measurement of particles dispersed in gases at high temperatures (600 °C) and pressures (16 bar). The main motivation for the construction of this device was a measurement requirement at the conditions of a pressurized pulverized coal combustion (PPCC) test installation in Dorsten, Germany. The development of a high efficiency (> 50 %), coal based, combined cycle process, and specifically, the development of efficient gas cleaning technology for gas combustion under demanding conditions (1400 °C and 16 bar) was the main target. A suitable measurement technique was required for the determination of particle size and concentration downstream of the gas cleaning equipment, which is able to operate close to the given conditions. The performance of the novel device was tested in several measurement series with various monodisperse aerosols at ambient conditions as well as in high pressure, high temperature situations with very satisfactory results, i.e., the lower detection limit (50 % counting efficiency at ca. 0.3 μm) and resolution of the novel device are comparable to state of the art instruments (of the same principle) intended for room temperature operation.
Generation of Monodisperse Micron‐Sized Droplets using Free Adjustable Signals
Authors: Riefler Norbert , Wriedt Thomas 
Published: April 2008

AbstractThis paper describes the generation of small water droplets in the size range down to a few microns. Commercially available inkjet printing devices are not suitable for producing such droplets since they produce satellite droplets. Furthermore, standard drop‐on‐demand devices are normally restricted to the generation of droplets with the same size as the orifice diameter. Using a new and more sophisticated computer‐based signal generation system, smaller‐sized droplets can be generated from the same orifice. A key feature of the design is the generation of freely definable pulses. This enables the generation of acoustic modes within the fluid of the droplet generator, which leads to the generation of droplets without satellites. Only very few pulse forms enable the generation of suitable acoustic modes. Therefore, it is necessary to look for the specific pulse corresponding to the chosen droplet generator. Flexible pulse form generation appears to be more suitable than simple pulse forms for the generation of such droplets.
Use of Video Enhanced Microscopy for Characterization of Solid‐Liquid‐Liquid Mixtures
Authors: Morales Carlos , Riebel Ulrich , Padrón Alida , Zuñiga Percy , Sorrentino José 
Published: April 2008

AbstractAlthough some particle sizing devices have gained a lot of popularity, none of them is able to distinguish between drops and solids and few are able to handle viscous oily samples. This paper discusses the use of the optical microscopy, enhanced by the use of digital video capabilities and image analysis software, to characterize oil production wastes. Several thousands of particles were counted and their projected areas were measured. A discussion is given about the different corrections required in order to extract the most reliable information from the image analysis, overcoming some of the drawbacks of this kind of measurements. The technique developed here offers unique features like the determination of the fraction of droplets that exist in the form of non‐coalesced agglomerates. When cross‐linked with the results obtained by standard ASTM procedures, it allows to infer the amount of disperse phase that exists in the form of submicron droplets or large free water drops that are usually not sampled for microscope slides.