bluuebunny/crossref_metadata_2025_split huggingface dataset:
Composite Particles: Design of Hybrid Materials on the Nano‐Scale
Authors: Hain Jessica , Pich Andrij , P. Adler Hans‐Jürgen 
Published: August 2007

AbstractSummary: In the last decade there has been a steady increased interest in the techniques providing design of nano‐structured materials. It has been demonstrated that colloidal polymeric particles can be successfully used for the deposition of different functional nano‐materials. Due to their numerous attractive properties polymeric particles have been used as templates for the synthesis, storage and transportation of nanostructured materials. This contribution demonstrates the synthetic ways for the preparation of hybrid particles by effective control over the size, morphology and distribution of the non‐miscible phases. Developed methods allow design of the composite particles on the nanometer scale and opens new possibilities for the preparation of the materials with advanced properties. The synthesis, characterization and applications of hybrid particles are discussed in detail.
In‐Situ Formation of BHET/Titanium Compound Nanocomposite and its Catalysis for Polyester
Authors: Xin Guoying , Sun Bin , Wang Wei , Zhu Liping , Wu Wenhua , Zhu Meifang , Chen Yanmo , Adler Hans‐Jurgen P. 
Published: August 2007

AbstractSummary: The tetrabutylorthotitanate (TBOT) was hydrolyzed by H2O produced during the esterification of pure terephthalic acid (PTA) and ethylene glycol (EG), and the bis(2‐hydroxyethyl) terephthalate (BHET)/titanium compound nanocomposite was in‐situ formed. The effect of TBOT on the esterification and its product property has been investigated. The results show that the butyl alcohol from the hydrolysis of TBOT is almost distilled out with H2O and there has no effect on the chemical structure of BHET caused by the introducing of TBOT. A kind of novel titanium compound is manufactured during the esterification under the existence of TBOT, which shows slice‐like morphology from SEM micrographs and special XRD pattern with new diffraction peaks between 2‐Θ = 6.9° and 10.2°. It is found that the BHET/titanium compound nanocomposite can act as the catalyst of polymerization of poly(ethylene terephthalate) (PET). The PET resins synthesized by in‐situ formed catalyst have almost the same physicochemical properties with the commerced resins and have good spinnability.
Preparation and Enantiospecific Binding of Chiral Polyelectrolyte Multilayers: AnIn‐SituATR‐FTIR Study
Authors: Ouyang Wuye , Appelhans Dietmar , Voit Brigitte , Muller Martin 
Published: August 2007

AbstractSummary:Two chiral polyelectrolyte multilayers (PEM) composed of poly(L‐lysine) (PLL) and poly(vinylsulfate) (PVS) as well as poly(ethyleneimine‐maltose) (PEI‐m) and poly(vinylsulfate) and a nonchiral PEM composed of poly(ethyleneimine) (PEI) and poly(vinylsulfate) were deposited on a silica surface using the layer by layer method. For both PEM enantiospecific interaction towards one enantiomer of either L‐/D‐ glutamic acid (L‐/D‐GLU) or L‐/D‐ascorbic acid (L‐/D‐ASC), respectively, was checked under variation of the concentration. Both deposition and enantiospecific interaction were studied by attenuated total reflection Fourier transform (ATR‐FTIR) spectroscopy. Preliminary results show a significant enantiospecific preference of D‐ GLU over L‐GLU at PEM of PLL/PVS and of D‐ASC over L‐ASC at PEM of PEI‐m/PVS and no such preference for nonchiral PEM of PEI/PVS. PEM of PLL/PVS shows higher enantiospecifity with increasing L‐/D‐GLU concentration.
Early Stages of Interchange Reactions in Polymer Blends
Authors: Kudryavtsev Yaroslav V. , Chertovich Alexander V. , Guseva Darja V. , Litmanovich Arkady D. 
Published: August 2007

AbstractSummary: Simple models are studied for better understanding of the early stages of interchange reactions in polymer blends. For a homogeneous blend of homopolymers A and B, parameters of copolymer AB formed at the reaction beginning are explicitly calculated. It is shown that the analysis of the copolymer composition can help to establish the prevailing interchange mechanism. For a bilayer blend of immiscible homopolymers A and B, the reactive compatibilization through interchange is studied by continual Monte Carlo modeling. The analysis of the local distribution in block length shows that the interdiffusion of blend components may start only after the formation of rather short copolymer blocks in the course of interchange.
Synthesis and Photopatterning of Fluorene Based Reactive Mesogens
Authors: Scheler Esther , Bauer Irene , Strohrigl Peter 
Published: August 2007

AbstractSummary: In this paper we report the synthesis, characterisation and photopatterning of polydisperse fluorene oligomers. The oligomers were synthesised using the Yamamoto coupling. The molecular weights of the oligomers and as a consequence the nematic‐isotropic transition temperatures were tailored by an endcapping reaction. With the endcapping species we introduced reactive acrylate functionalities. Subsequent photocrosslinking through a test mask led to the formation of fluorescent microstructures with a resolution of 1 µm.
Influence of Reactive Compatibilization on the Melt Flow Properties and Morphology of Polyamide 6/Styrene‐Acrylonitrile Blends
Authors: Sailer Christian , Handge Ulrich Alexander 
Published: August 2007

AbstractSummary: In this study, we investigate the influence of reactive compatibilization on the rheological properties of polyamide 6/styrene‐acrylonitrile (PA 6/SAN) blends in the melt. Linear viscoelastic shear oscillations, simple elongation to a large stretch ratio and subsequent recovery experiments were performed. The morphology of the blends was examined by atomic force microscopy. We prepared three PA 6/SAN blends with different composition ratios of PA 6 and SAN (70/30, 50/50, 30/70) and a constant concentration of the reactive agent. Our experiments revealed that reactive compatibilization significantly increases the complex modulus of PA 6/SAN blends at low frequencies. In particular, the data of the PA 6/SAN 50/50 blend and the PA 6/SAN 30/70 blend indicated that an elastic network between neighbouring PA 6 domains was formed. In simple elongation, the transient elongational viscosity of the blends exceeded the values of the single components. In recovery, the recovered stretch of all blends was larger than the recovered stretch of the pure components. The differences of the blend morphology and of the linear viscoelastic behaviour were qualitatively explained by the asymmetric properties of the reactively compatibilized interface.
Two Routes for Immobilization of a Hyperbranched OH‐Terminated Polyester on a Silicon Surface
Authors: Reichelt Senta , Jakisch Lothar , Simon Frank , Grundke Karina , Eichhorn Klaus‐Jochen , Voit Brigitte 
Published: August 2007

AbstractSummary: Stable thin films of a hyperbranched aromatic‐aliphatic OH‐terminated polyester (POH) were prepared on silicon substrates. We report on grafting‐to processes using macromolecular (PGMA) and bifunctional low‐molecular weight coupling agents (BOX). An appropriate annealing procedure was developed for the covalent immobilization. The HBP films were characterized with spectroscopic ellipsometry, drop shape analysis (DSA), atomic force microscopy (AFM), X‐ray photoelectron spectroscopy (XPS) and electrokinetic measurements. The immobilized films have an uniform surface morphology and are slightly hydrophilic (θa = 79°). The grafting process did not influence the chemical composition and the surface properties, which is important for the further application as functional layers in aqueous media.
Infrared Spectra of Alkylphosphonic Acid Bound to Aluminium Surfaces
Authors: Luschtinetz Regina , Seifert Gotthard , Jaehne Evelin , Adler Hans‐Jurgen P. 
Published: August 2007

AbstractSummary: The infrared absorption (IR) spectrum of alkyl phosphonic acid adsorbed on the α‐Al2O3 (0001) surface has been calculated by means of a density‐functional based tight‐binding method. Thereby mono‐dentate, bi‐dentate and tri‐dentate bonding of the acid to the surface have been considered. In addition, experimentally obtained Fourier Transform Infrared Spectra (FTIR) of octadecylphosphonic acid (ODPA) on the natural surface of aluminium have been included. The absence of the PO band in the experimental surface spectrum and in the calculated spectrum of the tridentate adsorption complexes showed that adsorption of (alkyl)phosphonic acids on aluminium favours tridentate bonding, where the acid is bound to the surface via three symmetric POAl bonds.
Pre‐Irradiation Grafting of Styrene into Modified Fluoropolymers
Authors: Lappan Uwe , Geißler Uwe , Uhlmann Steffi 
Published: August 2007

AbstractSummary: The grafting of styrene into commercially available fluoropolymer films by the pre‐irradiation method has been investigated. Poly(tetrafluoroethylene) (PTFE), poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP), poly(tetrafluoroethylene‐co‐perfluoropropylvinyl ether) (PFA) and poly(tetrafluorethylene‐co‐ethylene) (ETFE) were chosen as the base polymer material. The influence of the base material, the pre‐irradiation dose, and the storage time between the irradiation and the grafting step on the yield of grafting was examined. The base materials were pre‐treated by irradiation in the molten state under oxygen‐free conditions in order to create branches and cross‐links. The effect of pre‐treatment on the yield of grafting was studied.
Structure – Directing Effect of Renewable Resource Based Amphiphilic Dopants on the Formation of Conducting Polyaniline‐Clay Nanocomposite
Authors: Sudha Janardhanannair D. , Reena Viswan L. 
Published: August 2007

AbstractSummary: The structure‐directing effect of two amphiphilic dopants on the nucleation and growth mechanism during the formation of micro/ nanostructured polyaniline (PANI) and polyaniline‐clay nanocomposites (PANICNs) is described. PANIs and PANICNs were prepared by in‐situ intercalative emulsion polymerization of aniline using the amphiphilic dopants, 3‐pentadecyl phenyl phosphoric acid (3‐PDPPA) and 3‐pentadecyl phenol–4‐sulphonic acid (3‐PDPSA), derived from cashew nut shell liquid, a renewable resource. These molecules act as intercalating agents, dopants and also as structure‐directing agents. X‐ ray diffraction (XRD) and scanning electron microscopic (SEM) studies revealed the formation of lamellar/fibrillar – network in PANI‐ PDPPA and cylinder/rod morphology in PANI‐PDPSA. Experimental data reveal that fibrillar morphology arises from the heterogeneous nucleation followed by an indefinite growth mechanism. On the other hand rod‐like structures are formed from the self‐assembled rod‐like micelle guided polymerization through homonucleation followed by an anisotropic growth mechanism. Electrical conductivity measurement revealed lower conductivities for PANICNs than that of PANIs.
Conductive UV Curable Adhesives for Printed RFID Antenna Structures
Authors: Kowalik T. , Worch S. , Hartwig A. , Joachimi H. 
Published: August 2007

AbstractSummary: For the use as RFID antennas conductive adhesives were developed and investigated which are UV curable and could be applied with printing methods like offset printing or flexography. Further investigated aspects of the materials have been the range of the distance between emitter and receiver. The resulting formulations which are based on acrylates filled with silver pigments for the conductivity allow to cure layers with a thickness of up to 50 µm with a maximal volume resistance of 1.6 × 10−5 Ω/cm.
On the Modeling of Polyelectrolyte Gels
Authors: Wallmersperger Thomas , Ballhause Dirk , Kröplin Bernd 
Published: August 2007

AbstractSummary: Ionic polymer gels are very attractive actuation materials with a great similarity to biological contractile tissues. They consist of a polymer network with bound charged groups and a liquid phase with mobile ions. Absorption and delivery of solvent lead to a considerably large change of volume. This swelling mechanism results from the equilibrium of different forces such as osmotic pressure forces, electrostatic forces and viscoelastic restoring forces and can be triggered by chemical (change of salt concentration or pH in the solution), thermal or electrical stimulation. In the present work, chemically and electrically stimulated electrolyte polymer gels in a solution bath are investigated. To describe the different phenomena occurring in these gels adequately, the modeling can be conducted on different scales. If only the global macroscopic behavior is of interest, the statistical theory which is capable to describe the global swelling ratio, is sufficient. By refining the scale, the mesoscopic coupled multi‐field theory can be applied. Here, the chemical field is described by a convection‐diffusion equation for the different mobile species. The electric field is directly obtained by solving the Poisson equation in the gel and solution domain. The mechanical field is formulated by the momentum equation. By further refining the scale, the whole structure can be investigated on the microscale by the discrete element (DE) method. In this model, the material is represented by distributed particles comprising a certain amount of mass; the particles interact with each other mechanically by a truss or beam network of massless elements. The mechanical behavior, i.e. the dynamics of the system, is followed by solving the Newton's equations of motion while the chemical field, i.e. the ion movement inside the gel and from the gel to the solution, is described by diffusion equations for the different mobile particles. All three formulations can give chemical, (electrical) and mechanical unknowns and all rely on the assumption that the concentration differences between the different regions of the gel and between gel and solution form the osmotic pressure difference, which is a main cause for the mechanical deformation of the polyelectrolyte gel film.
Novel Hydrogels for Rhythmic Pulsatile Drug Delivery
Authors: Mujumdar Siddharthya K. , Bhalla Amardeep S. , Siegel Ronald. A 
Published: August 2007

AbstractSummary: We are investigating an autonomous glucose‐driven hydrogel/enzyme‐based device prototype for rhythmic, pulsed delivery of gonadotropin releasing hormone (GnRH). The device employs a pH‐sensitive hydrogel membrane in conjunction with the enzyme glucose oxidase. This system delivers GnRH in rhythmic pulses when exposed to a constant level of glucose. These pulses result from autonomous pH oscillations inside the device that are created by an unstable nonlinear feedback between hydrogel permeability to glucose and production of acid by glucose oxidase. Previous versions of this prototype utilized p(N‐isopropylacrylamide‐co‐methylacrylic acid) p(NIPA‐co‐MAA) hydrogels, with 10 mol% MAA incorporated. With this membrane, which undergoes a volume transition (VT) near pH 5, pH oscillations centered around pH 5 are observed. This range is too low to sustain oscillations in physiologically buffered media. To shift the operating pH of oscillations closer to physiologic pH, we have sought ways to increase the pH of the volume transition. In this study we show that increasing the side chain length of the α‐alkylacrylic acid (RAA) comonomer enhances the overall hydrophobicity of the copolymer, and shifts the VT pH closer to physiological pH values. We also demonstrate the ability of such membranes to affect an alkaline shift in the range of oscillations in the prototype oscillator device.
On the Development of the VIPAR Polymer Gel Dosimeter for Three‐Dimensional Dose Measurements
Authors: Kozicki Marek , Maras Piotr , Rybka Krzysztof , Biegański Tadeusz , Kadłubowski Sławomir , Petrokokkinos Loukas 
Published: August 2007

AbstractSummary: The new polymer gel dosimeter, based on the modification of the VIPAR gel composition, is described for the purpose of radiation dose distribution measurement in radiotherapy. It features increased concentration of the two VIPAR substrates: N‐vinylpyrrolidone (8%) and gelatine (7.5%) (N,N′‐methylenebisacrylamide was maintained at 4%), and the addition of copper sulphate (0.0008%) and ascorbic acid (0.007%) in order to facilitate the preparation through elimination of the need for deoxygenation of the gel. Following the exposure to ionizing radiation, polymerisation and cross‐linking of the new gel monomers occurs retaining the spatial distribution of absorbed dose and causing opacity of the gel. Quantitative parameters of the new gel dose response were studied using magnetic resonance imaging to relate polymerisation induced physicochemical changes of the gel to dose. The dose threshold is found significantly lower than that of the original VIPAR gel. The linear part of measured spin‐spin relaxation rate R2(D) ( = 1/T2(D)) reaches up to 35 Gy. Its slope and an intercept are slightly higher relative to the original VIPAR. The efficiency of the new polymer gel‐magnetic resonance imaging dosimeter was also tested for dose verification of a 3D dose distribution planned by a commercially available treatment planning software (Eclipse External Beam v.6.5) and delivered by a 6 MV medical linear accelerator. The new polymer gel is proposed to be called, VIPARnd (after VIPAR‐normoxic‐double).
Polymersome‐Embedded Nanoparticles
Authors: Sachsenhofer Robert , Binder Wolfgang H. , Farnik Dominique , Zirbs Ronald 
Published: August 2007

AbstractSummary: Polymersomes are self assembled vesicles composed of fully synthetic amphiphilic diblock copolymers. Many of their properties are similar to lipid vesicles, although with often higher thermal and mechanical stability within their curved membrane. Incorporation of nanosized objects into their hydrophilic interior or hydrophobic membrane represents an important method for functionalization of these biomimetic structures. We report on the embedding of hydrophobic gold nanoparticles (Au‐NPs) into polymersomes. Nanoparticles were prepared and incorporated into polymersomes made by standard film rehydration techniques from commercially available diblock copolymers. Characterization of the resulting structures was achieved by dynamic light scattering (DLS) and by TEM. Results on the preparation method, its influence on the polymersome stability and the application of these new membrane‐mimetics are reported.
Multiwalled Carbon Nanotubes Produced by a Continuous CVD Method and Their Use in Melt Mixed Composites with Polycarbonate
Authors: Potschke Petra , Fischer Dieter , Simon Frank , Haußler Liane , Magrez Arnaud , Forró László 
Published: August 2007

AbstractSummary: In this study, two samples of multiwalled carbon nanotubes (MWNT) were synthesized by CVD of acetylene over Fe2Co catalysts supported by CaCO3 using different temperatures. The material produced at 660 °C (MWNT600) shows slightly better performance as evidenced by lower mean tube diameter and better conductivity as compared to the sample produced at 700 °C (MWNT700). In addition, it has a higher [O]:[C] ratio. Both materials were incorporated into polycarbonate using melt mixing using a small scale compounder. The results prove that these materials are very suitable for polymer composite applications as they show low electrical percolation concentration and good mechanical enhancement. The percolation threshold is as low as <0.875 wt% for MWNT660 and <1 wt% for MWNT700. MWNT700 showed slightly better dispersability as evidenced from light microscopy, SEM, and TEM. The effects in the stress‐strain curves are similar in both composites, indicating a stress increase with MWNT incorporation.
Therapeutics targeting tumor immune escape: Towards the development of new generation anticancer vaccines
Authors: Mocellin Simone , Nitti Donato 
Published: August 2007

AbstractDespite the evidence that immune effectors can play a significant role in controlling tumor growth under natural conditions or in response to therapeutic manipulation, it is clear that malignant cells evade immune surveillance in most cases. Considering that anticancer vaccination has reached a plateau of results and currently no vaccination regimen is indicated as a standard anticancer therapy, the dissection of the molecular events underlying tumor immune escape is the necessary condition to make anticancer vaccines a therapeutic weapon effective enough to be implemented in the routine clinical setting. Recent years have witnessed significant advances in our understanding of the molecular mechanisms underlying tumor immune escape. These mechanistic insights are fostering the development of rationally designed therapeutics aimed at reverting the immunosuppressive circuits that undermine an effective antitumor immune response. In this review, the best characterized mechanisms that allow cancer cells to evade immune surveillance are overviewed and the most debated controversies constellating this complex field are highlighted. In addition, the latest therapeutic strategies devised to overcome tumor immune escape are described, with special regard to those entering clinical phase investigation. © 2007 Wiley Periodicals, Inc. Med Res Rev, 28, No. 3, 413–444, 2008
On the Navier–Stokes equations with free convection in three‐dimensional unbounded triangular channels
Authors: Constales D. , Kraußhar R. S. 
Published: August 2007

AbstractThe quaternionic calculus is a powerful tool for treating the Navier–Stokes equations very elegantly and in a compact form, through the evaluation of two types of integral operators: the Teodorescu operator and the quaternionic Bergman projector. While the integral kernel of the Teodorescu transform is universal for all domains, the kernel function of the Bergman projector, called the Bergman kernel, depends on the geometry of the domain. In this paper, we use special variants of quaternionic‐holomorphic multiperiodic functions in order to obtain explicit formulas for unbounded three‐dimensional parallel plate channels, rectangular block domains and regular triangular channels. Copyright © 2007 John Wiley & Sons, Ltd.
The involvement of oxidative stress in ochratoxin A and fumonisin B1 toxicity in rats
Authors: Domijan Ana‐Marija , Peraica Maja , Vrdoljak Ana Lucić , Radić Božica , Žlender Vilim , Fuchs Radovan 
Published: August 2007

AbstractThe aim of this study was to find out whether very low doses of nephrotoxic and hepatotoxic mycotoxins ochratoxin A (OTA) and fumonisin B1 (FB1) induce oxidative stress in rat kidney and liver and whether their effect is synergistic. Rats were treated orally with OTA (5 ng/kg b.w. and 50 μg/kg b.w.) and FB1 (200 ng/kg b.w. and 50 μg/kg b.w.), or their combinations. Malondialdehyde (MDA) and protein carbonyls (PCs) concentration in kidney was affected with lower dose of OTA than in liver (p < 0.05). FB1 did not affect MDA and PCs concentrations in the liver, while in the kidney both FB1 doses increased MDA concentration (p < 0.05). The combination of the lower doses of OTA + FB1 increased the MDA and PCs concentration both in the liver and the kidney, compared to controls and animals treated with respective doses of mycotoxins (p < 0.05). The combinations of mycotoxins reduced the catalase activity only in the kidney when compared to controls (p < 0.05). In contrast to the increased kidney concentrations of MDA and PCs even with very low doses of OTA and FB1, the activity of catalase and SOD does not change. Combinations of OTA + FB1 affected almost all parameters, which indicates their potential to produce oxidative damage.