bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diblock Copolymers with Azobenzene Side‐Groups and Polystyrene Matrix: Synthesis, Characterization and Photoaddressing
Authors: Frenz Carsten , Fuchs Andreas , Schmidt Hans‐Werner , Theissen Ulrich , Haarer Dietrich 
Published: June 2004

AbstractSummary: Diblock copolymers with a photoaddressable dispersed phase containing p‐methoxy substituted azobenzene side groups and a polystyrene matrix were synthesized and characterized. The block copolymers were prepared by a sequential living anionic polymerization of butadiene and styrene. The poly(1,2‐butadiene) segment was hydroborated and the hydroxy‐functions converted by a polymeranalogous reaction with the azo chromophore as side groups. The block copolymers were synthesized with different compositions by varying the length of the polystyrene segment and the length of the functionalized segment in order to obtain different morphologies. In this paper, for the first time a comparison of the cis‐trans photo‐isomerization behavior and photoaddressing with respect to different morphologies of the block copolymers is presented. To complete the comparison, the corresponding homopolymer and a statistical copolymer were also synthesized and investigated. A different photoaddressing behavior between homopolymer, statistical copolymer and the block copolymers was observed. One principal difference and advantage for photo addressable block copolymers is the lack of a formation of surface gratings which occurs in homopolymers and statistical copolymers.TEM of a poly(1,2‐butadiene)‐block‐polystyrene copolymer containing azobenzene side‐groups.magnified imageTEM of a poly(1,2‐butadiene)‐block‐polystyrene copolymer containing azobenzene side‐groups.
New Regular, Amphiphilic Poly(ampholyte)s: Synthesis and Characterization
Authors: Rullens François , Devillers Michel , Laschewsky André 
Published: May 2004

AbstractSummary:Hydrophobically substituted diallylamines bearing a hexyl, dodecyl, or octadecyl chain were synthesized and homopolymerized as hydrochlorides. Copolymerization of the diallylamines with maleic acid produces alternating copolymers. The copolymers behave as amphiphilic polyampholytes and dissolve best in the acidic or in the basic form. Only the copolymer with the hexyl chain could be dissolved in aqueous solvents and shows hydrophobic association. The copolymers with the longer alkyl chains require polar protic organic solvents. All polymers are amorphous, but show a superstructure in bulk due to their amphiphilicity.magnified image
Novel Photosensitive Fluorinated Poly(arylene ether) Having Zero Birefringence
Authors: Li Xiang‐Dan , Zhong Zhen‐Xin , Kim Jang J. , Lee Myong‐Hoon 
Published: May 2004

AbstractSummary: A novel photosensitive fluorinated poly(arylene ether) containing chalcone units was synthesized from decafluorinated chalcone and fluorinated bisphenol at low temperature. Upon UV irradiation, the refractive indices of the polymer film were decreased because of the reduction of electronic polarizability in the chalocone moiety. The decrease was more significant in the in‐plane direction than in the out‐of‐plane direction, and consequently, zero birefringence (at 632.8 nm) was obtained after 90 s of exposure.The changes in the refractive indices and the birefringence of chalcone‐containing fluorinated poly(arylene ether) films synthesized and measured at 632.8 nm with respect to UV irradiation time.imageThe changes in the refractive indices and the birefringence of chalcone‐containing fluorinated poly(arylene ether) films synthesized and measured at 632.8 nm with respect to UV irradiation time.
Nano‐Structural Observation of in situ Silica in Natural Rubber Matrix by Three Dimensional Transmission Electron Microscopy
Authors: Ikeda Yuko , Katoh Atsushi , Shimanuki Junichi , Kohjiya Shinzo 
Published: June 2004

AbstractSummary: Three dimensional (3D) nanostructures of particulate silicas in natural rubber (NR) were observed for the first time by use of 3D transmission electron microscopy (3D‐TEM) combined with electron tomography. The method enabled us to visualize and evaluate structural characteristics in 3D space, such as the size and the volume of in situ silica generated in the NR matrix by the sol‐gel reaction of tetraethoxysilane, at nanometer scale resolution.The reconstructed mass density view of the silica in an in situ silica‐filled natural rubber vulcanizate, as determined by 3D‐TEM.imageThe reconstructed mass density view of the silica in an in situ silica‐filled natural rubber vulcanizate, as determined by 3D‐TEM.
In situ Reaction and Radiation Protection Properties of Gd(AA)3/NR Composites
Authors: Liu Li , He Lei , Yang Cheng , Zhang Wan , Jin Ri‐Guang , Zhang Li‐Qun 
Published: June 2004

AbstractSummary: For the first time, a series of Gd(AA)3/NR (natural rubber) composites for X‐ray shielding were prepared by an in situ reaction method. Occurrence of the in situ polymerization of Gd(AA)3 in composites during vulcanization of NR with peroxide greatly improves the dispersion level of the shielding phase by the remarkable reduction of Gd(AA)3 particle size and the formation of small sized poly‐Gd(AA)3 from the matrix. As expected and assumed, the X‐ray shielding properties of all composites apparently increase with the increase of the degree of dispersion of Gd(AA)3 in composites.The ability of the composites to shield X‐ray radiation increases with an increase in Gd(AA)3 content and as the degree of in situ polymerization of Gd(AA)3 increases (i.e., as t tends towards t100).imageThe ability of the composites to shield X‐ray radiation increases with an increase in Gd(AA)3 content and as the degree of in situ polymerization of Gd(AA)3 increases (i.e., as t tends towards t100).
Photopatterning of Crosslinkable Hole‐Conducting Materials for Application in Organic Light‐Emitting Devices
Authors: Bacher Erwin , Jungermann Steffen , Rojahn Markus , Wiederhirn Valérie , Nuyken Oskar 
Published: June 2004

AbstractSummary: Modern multilayer organic light‐emitting devices (OLED) are fabricated easily and at low cost by spin‐coating with subsequent crosslinking of the layers. For this purpose, a low‐molecular‐weight hole‐transport material based on triphenyl amines bearing crosslinkable oxetane groups was synthesized. Crosslinking of the spin‐coated layer was initiated with UV irradiation using an iodonium‐salt photoinitiator and was observed using realtime FT‐IR spectroscopy. Standard photolithography techniques can be used for structuring the material on the micrometre scale.An AFM image of the photopatterned bis‐oxetane‐functionalized low‐molecular‐weight hole‐transport material based on triphenyl amines synthesized here.imageAn AFM image of the photopatterned bis‐oxetane‐functionalized low‐molecular‐weight hole‐transport material based on triphenyl amines synthesized here.
Processing of a Strong Biodegradable Poly[(R)‐3‐hydroxybutyrate] Fiber and a New Fiber Structure Revealed by Micro‐Beam X‐Ray Diffraction with Synchrotron Radiation
Authors: Iwata Tadahisa , Aoyagi Yoshihiro , Fujita Masahiro , Yamane Hideki , Doi Yoshiharu , Suzuki Yoshio , Takeuchi Akihisa , Uesugi Kentaro 
Published: May 2004

AbstractSummary: Biodegradable poly[(R)‐3‐hydroxybutyrate] (P(3HB)) fibers with high tensile strength of 1.32 GPa were processed from ultra‐high‐molecular‐weight P(3HB) by a method combining cold‐drawing and two‐step‐drawing procedures at room temperature. The distribution of molecular structures in a mono‐filament was analyzed by micro‐beam X‐ray diffraction with synchrotron radiation. It was revealed that the P(3HB) fiber has a new core‐sheath structure consistent with two types of molecular conformations: a 21 helix conformation in the sheath region and a planar zigzag conformation in the core region.P(3HB) fiber processed by cold‐drawing in ice water and two‐step drawing at room temperature, and subsequently annealing at 50 °C.imageP(3HB) fiber processed by cold‐drawing in ice water and two‐step drawing at room temperature, and subsequently annealing at 50 °C.
Use of Cartesian Rotation Vectors in Brownian Dynamics Algorithms: Theory and Simulation Results
Authors: Naess Stine Nalum , Elgsaeter Arnljot 
Published: May 2004

AbstractSummary: We have shown that the components of Cartesian rotation vectors can be used successfully as generalized coordinates describing angular orientation in Brownian dynamics simulations of non‐spherical nanoparticles. For this particular choice of generalized coordinates, we rigorously derived the conformation‐space diffusion equations from kinetic theory for both free nanoparticles and nanoparticles interconnected by springs or holonomic constraints into polymer chains. The equivalent stochastic differential equations were used as a foundation for the Brownian dynamics algorithms. These new algorithms contain singularities only for points in the conformation‐space where both the probability density and its first coordinate derivative equal zero (weak singularities). In addition, the coordinate values after a single Brownian dynamics time step are throughout the conformation‐space equal to the old coordinate values plus the respective increments. For some parts of the conformation‐space these features represent a major improvement compared to the situation when Eulerian angles describe rotational dynamics. The presented simulation results of the equilibrium probability density for free nanoparticles are in perfect agreement with the results from kinetic theory.Simulation of p(eq)(Φ) for free nanoparticles.imageSimulation of p(eq)(Φ) for free nanoparticles.
Electrochemical behaviour of Mo‐containing austenitic stainless steels in buffer solution
Authors: El‐Taib Heakal F. , Ameer M.A. , El‐Aziz A.M. , Fekry A.M. 
Published: June 2004

AbstractThe effect of pH on the electrochemical behavior of austenitic stainless steels in naturally aerated and nitrogen‐deaerated buffer solutions has been studied.Potentiodynamic and ac impedance techniques were used. The results indicate that corrosion current (Icorr) decreases with pH. By examining the impedance data for the seven tested steels under various conditions, it seems that the total resistance (RT) value is a suitable indication parameter for explaining the role of molybdenum and the other supplementary alloying additions (Ni, N, Cu and Mn) on the passive film behaviors as a function of pH of the forming solutions. As a general trend, the RT values for all steels tended to be lower in the basic buffer than in the acidic solutions.
Expression profile of eukaryotic translation factors in human cancer tissues and cell lines
Authors: Joseph Pius , O'Kernick Christina M. , Othumpangat Sreekumar , Lei Yi‐Xiong , Yuan Bao‐Zhu , Ong Tong‐Man 
Published: May 2004

AbstractSeveral studies have demonstrated the overexpression of certain eukaryotic translation factors in human cancer cell lines and in malignant tissues. In this study, with human cancer cell lines derived from lungs, breast, prostate, and skin, we have examined the expression profile of 36 translation factors consisting of 27 initiation factors, 8 elongation factors, and 1 termination factor. Translation initiation factors 2C2 and 4E1 and translation elongation factors 1A2 and 1δ were found overexpressed (2‐ to 2000‐fold) in many of the cancer cell lines compared to their corresponding normal cell lines. Among the translation factors analyzed, translation elongation factor 1A2 exhibited the most significant alteration in expression: 10‐ to 2000‐fold overexpression was noticed in nine out of ten cancer cell lines analyzed. Whether the overexpression of translation elongation factor 1A2 can be used as a potential tumor marker was tested with the cancer profiling array (BD Biosciences, Palo Alto, CA) consisting of 241 paired cDNA samples generated from 13 different cancer/noncancer tissue types. Overexpression of translation elongation factor 1A2 was noticed in several tumor tissue samples, most notably in the human colon cancer samples which exhibited at least a twofold overexpression among 35% of the samples analyzed. Besides colon, tumor samples derived from lungs, kidney, rectum, and ovary also exhibited more than a twofold overexpression of translation elongation factor 1A2 in at least 20% of the samples analyzed. These results indicate that human carcinogenesis is often associated with alterations in the expression of various translation factors especially the overexpression of eukaryotic translation elongation factor 1A2. © 2004 Wiley‐Liss, Inc.
Nkx2.1 transcription factor in lung cells and a transforming growth factor‐β1 heterozygous mouse model of lung carcinogenesis
Authors: Kang Yang , Hebron Haroun , Ozbun Laurent , Mariano Jennifer , Minoo Parviz , Jakowlew Sonia B. 
Published: May 2004

AbstractThe Nkx2.1 homeobox gene and transforming growth factor‐β1 (TGF‐β1) are essential for organogenesis and differentiation of the mouse lung. NKX2.1 is a marker of human lung carcinomas, but it is not known whether this gene participates in early tumorigenesis. Addition of TGF‐β1 to TGF‐β1‐responsive nontumorigenic mouse lung cells cotransfected with a NKX2.1Luc luciferase reporter and either a Sp1 or Sp3 plasmid showed a significant increase or decrease, respectively, in NKX2.1Luc transcription. Cotransfection of Sp3 and dominant‐negative TGF‐β type II receptor plasmids negated the effect of Sp1. Cotransfected Sp1 plasmid with either dominant‐negative Smad2 or Smad3 or Smad4 plasmids significantly decreased NKX2.1Luc transcription. Electrophoretic mobility shift assays revealed binding of Sp1 and Smad4 to the NKX2.1 promoter. With a TGF‐β1 heterozygous mouse model, Nkx2.1 mRNA and protein in lungs of TGF‐β1 heterozygous mice were significantly lower compared to wildtype (WT) littermates. Competitive reverse transcription (RT)‐polymerase chain reaction (PCR) and immunostaining showed that Nkx2.1 mRNA and protein decreased significantly in adenomas and adenocarcinomas compared to normal lung tissue. Our in vitro data showed that regulation of Nkx2.1 by TGF‐β1 occurs through TGF‐β type II receptor and Smad signaling, with Sp1 and Sp3 in lung cells. Our in vivo data showed reduced Nkx2.1 in lungs of TGF‐β1 heterozygous mice compared to WT mice, that is detectable in adenomas, and that is further reduced in carcinogenesis, and that correlates with reduction of Sp1, Sp3, and Smads in lung adenocarcinomas. Our findings suggest that reduced Nkx2.1 and TGF‐β1 signaling components may contribute to tumorigenesis in the lungs of TGF‐β1 heterozygous mice. Published 2004 Wiley‐Liss, Inc.
Cannabis‐induced propriospinal myoclonus
Authors: Lozsadi Dora A. , Forster Alan , Fletcher Nicholas A. 
Published: June 2004

AbstractWe report on a case of a 25‐year‐old woman with clusters of myoclonus induced by a single exposure to inhaled cannabis. Investigations excluded a structural abnormality of the spine. Multi‐channel surface EMG with parallel frontal EEG recording confirmed the diagnosis of propriospinal myoclonus. © 2004 Movement Disorder Society
Bionanotechnology based on silica nanoparticles
Authors: Tan Weihong , Wang Kemin , He Xiaoxiao , Zhao Xiaojun Julia , Drake Timothy , Wang Lin , Bagwe Rahul P. 
Published: May 2004

AbstractWe have developed uniform core/shell nanoparticles, consisting of a silica layer coating and pigments or magnetite core, using a water‐in‐oil microemulsion method. The nanoparticles are highly luminescent and photostable with the size ranging from 5 nm to 400 nm. Bioconjugation of these silica nanoparticles adds unique biofunctions with various molecules such as enzymes, antibodies, and DNA molecules. Significant advantages have been shown in using bioconjugated nanoparticles for biosensing and bioimaging, such as cell staining, DNA detection and separation, rapid single bacterium detection, and biotechnological application in DNA protection. © 2004 Wiley Periodicals, Inc. Med Res Rev, 24, No. 5, 621–638, 2004
AMPA receptor ligands: Synthetic and pharmacological studies of polyamines and polyamine toxins
Authors: Strømgaard Kristian , Mellor Ian 
Published: May 2004

Abstractα‐Amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionic acid (AMPA) receptors (AMPAR), subtype of the ionotropic glutamate receptors (IGRs), mediate fast synaptic transmission in the central nervous system (CNS), and are involved in many neurological disorders, as well as being a key player in the formation of memory. Hence, ligands affecting AMPARs are highly important for the study of the structure and function of this receptor, and in this regard polyamine‐based ligands, particularly polyamine toxins, are unique as they selectively block Ca2+‐permeable AMPARs. Indeed, endogenous intracellular polyamines are known to modulate the function of these receptors in vivo. In this study, recent developments in the medicinal chemistry of polyamine‐based ligands are given, particularly focusing on the use of solid‐phase synthesis (SPS) as a tool for the facile generation of libraries of polyamine toxin analogues. Moreover, the recent development of highly potent and very selective AMPAR ligands is described. Additionally, we provide a detailed account on the mechanism and site of action of AMPAR blockade by polyamine‐based ligands, including examples of how these ligands are used as tools to study AMPAR, and a comparison with their action on other ionotropic receptors. © 2004 Wiley Periodicals, Inc. Med Res Rev, 24, No. 5, 589–620, 2004
2‐Octylcynanoacrylate‐assisted microvascular anastomosis in a rat model: Long‐term biomechanical properties and histological changes
Authors: Ong Yee Siang , Yap Karen , Ang Erik S.W. , Tan Kok Chai , Ng Robert T.H. , Song Irene C. 
Published: June 2004

AbstractThe aim of this study was to establish the long‐term biomechanical and histological properties of 2‐octylcyanoacrylate‐assisted microvascular anastomosis over conventional suture‐only anastomosis in the laboratory rat model. The biomechanical and histological properties of three groups of vessels were compared: 1) vessels with 2‐octylcyanoacrylate‐assisted anastomoses (study group); 2) vessels with suture‐only anastomoses (control group); and 3) normal unoperated vessels (sham group). In total, 144 adult rats were used, and these were studied at 1 week, 1 month, 3 months, and 6 months postanastomosis. At 6 months, the tensile strength of study vessels was significantly higher than control vessels. The stiffness of study and control vessels was similar at all time intervals. Histologically, there was no evidence that 2‐ octylcyanoacrylate caused toxicity to vessel walls, and there was less perivasacular foreign‐body giant‐cell reaction in the study group compared to the control group. Long‐term follow‐up showed that microvascular anastomosis with 2‐octylcyanoacrylate in rat femoral arteries had superior tensile strength and similar stiffness to vessels anastomosed with sutures only, without adverse effects to surrounding tissues. © 2004 Wiley‐Liss, Inc.
Block copolymerizations of higher 1‐olefins with traditional polar monomers using metallocene‐type single component lanthanide initiators
Authors: Yasuda Hajime , Desurmont Guillaume 
Published: May 2004

AbstractBlock copolymerizations of 1‐pentene or 1‐hexene with methyl methacrylate or ε‐caprolactone were explored using [Me2Si(2‐SiMe3‐4‐t‐BuMe2SiC5H2)2YH]2 (1) or [Me2Si(2‐SiMe3‐4‐t‐BuC5H2)2SmH]2 (2) as an initiator in toluene or in neat mixtures by the successive additions of monomers in this order. Random copolymerizations of 1‐pentene with 1‐hexene, and random copolymerization of ethylene with 1‐hexene were also performed using 1 as an initiator. Copyright © 2004 Society of Chemical Industry
Orientation effects on the deformation and fracture properties of high‐density polyethylene/ethylene vinyl acetate (HDPE/EVA) blends
Authors: Na Bing , Zhang Qin , Wang Yong , Fu Qiang 
Published: May 2004

AbstractIn this paper, the tensile deformation and fracture toughness of high‐density polyethylene (HDPE)/ethylene vinyl acetate (EVA) blends, obtained by dynamic packing injection moulding, have been comprehensively investigated in different directions of rectangle samples, including longitudinal, latitudinal and oblique directions relative to the flow direction. Two kinds of EVA were used with VA content 16 wt% (16EVA) and 33 wt% (33EVA) to control the interfacial interactions. The results indicate that molecular orientation and interfacial interaction play very important roles to determine the tensile behaviour and fracture toughness. Biaxial‐reinforcement of tensile strength was seen for HDPE/16EVA blends but only uniaxial‐reinforcement was observed for HDPE/33EVA blends. The difference is caused by the different interfacial interactions as highlighted by the peel test, scanning electron microscopy (SEM) observation as well as theoretical evaluation. Very high impact strength, decreasing with increasing EVA content, was observed when the fracture propagation is perpendicular to the shear flow direction, while a low impact strength, increasing slightly increasing with EVA content, was seen when the fracture propagation is parallel to the shear flow. The fracture of oblique samples is always along the flow direction instead of along the impact direction or tensile direction. The tensile behaviour and fracture toughness are discussed on the basis of the formation of transcrystalline zones, orientation of EVA particles and matrix toughness of HDPE in different directions. Copyright © 2004 Society of Chemical Industry
Crystallization and melting behaviour of polypropylene ‘catalloys’
Authors: Zheng Qiang , Lin Zhonghua , Peng Mao 
Published: May 2004

AbstractThe crystallization and melting behaviour of polypropylene ‘catalloys’ (PP‐cats) as well as pure polypropylene (PP) were investigated using differential scanning calorimetry. The results showed that, for PP‐cats and PP, a single melting peak of PP appeared under slow cooling rate. When the cooling rate is fast enough in the non‐isothermal case, or the crystallization temperature is relatively high in the isothermal case, a shoulder peak appears in front of the melting peak with increasing ethylene content in PP‐cats. It is believed that this shoulder is induced by recrystallization of crystals initially formed during non‐isothermal or isothermal crystallization. When the ethylene component in PP‐cats reached a certain level, there existed a melting peak of polyethylene (PE) crystallized during the cooling process. Polarized optical microscopy (POM) showed that the spherulites formed by PP‐cats were much smaller and had less perfect morphology compared with that formed by pure PP at the same cooling rate. And with the increase of the cooling rate, the spherulites could not be clearly observed. Copyright © 2004 Society of Chemical Industry
An investigation into the degree and rate of polymerization of poly(methyl methacrylate) in the ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate
Authors: Benton Michael G , Brazel Christopher S 
Published: May 2004

AbstractRoom‐temperature ionic liquids (ILs), including 1‐butyl‐3‐methylimidazolium hexafluorophosphate, [bmim+][PF6−], were investigated as replacements for volatile organic compounds in the free‐radical solution polymerization of poly(methyl methacrylate) (PMMA). The latter was synthesized in benzene and [bmim+][PF6−] at 70 °C via a free‐radical process and the degree and rate of polymerization were compared based on the solvent used. The degree of polymerization was found to be five times higher in [bmim+][PF6−] than in benzene, while the rate of reaction was approximately four times faster in [bmim+][PF6−]. The results indicate the potential for using ILs to produce high‐molecular‐weight polymers and block structures based on the increased free‐radical stability in ILs. Copyright © 2004 Society of Chemical Industry