bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of liquid characteristics on the wetting, capillary migration, and retention properties of fibrous polymer networks
Authors: Unsal E. , Dane J. H. , Schwartz P. 
Published: April 2005

AbstractFluid penetration through porous networks consists of two different phenomena: (1) pore fluid displacement and (2) fluid flow through the pores. The first phenomenon depends on the pore size, the fluid–fluid interfacial tension, and the contact angle. The second phenomenon is pore‐size‐ and viscosity‐dependent. We adapted an experimental methodology often used for measurements of liquid permeability and hydraulic conductivity of soils and applied it to polymeric medical textiles. The methodology made use of a pressure/flow cell in which a sample was mounted. The flow rates were measured during sequences of increasing and decreasing pressures applied to the displacing nonwetting fluid (aqueous solution). The effects of the liquid parameters on penetration were investigated. Surface tension effects were studied with water and two solutions with surface tensions lower than that of pure water; the liquids with lower surface tensions had lower displacement pressures. To study viscosity effects, we used water and two solutions with viscosities higher than that of pure water. Increasing the viscosity not only caused the flow rate to decrease but also caused deformation, that is, enlargement, of the pores. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 282–292, 2005
Evaluation of the tensile properties and thermal stability of ultrahigh‐molecular‐weight polyethylene fibers
Authors: Liu Xiaoyan , Yu Weidong 
Published: April 2005

AbstractThe thermal stability of ultrahigh‐molecular‐weight polyethylene (UHMWPE) should be paid attention in its applications, although the fiber has excellent flexible tensile properties. The measurements for two kinds of UHMWPE fibers, Dyneema SK65 (The Netherlands) and ZHF (Beijing, China), were carried out at different annealing temperatures and for different aging times. Experimental and regression analysis results showed that the aging behavior of the fibers followed an exponential attenuation with the annealing temperature and aging time. The critical temperature for the safe use of the fibers was equal to or lower than 70°C and depended on the glass‐transition temperature; this was validated by tensile tests. The difference between the two fibers in the thermal properties resulted from the intrinsic supermolecular structures of the two fibers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 310–315, 2005
Solution properties of ionic hydrophobically associating polyacrylamide with an arylalkyl group
Authors: Ma Jun‐Tao , Huang Rong‐Hua , Zhao Lin , Zhang Xi 
Published: April 2005

AbstractCopolymers of acrylamide, 2‐acrylamide‐2‐methylpropanesulfate (AMPS), and hydrophobic monomer N‐arylalkylacrylamide (BAAM) were synthesized by free‐radical micellar copolymerization. The effects of the copolymer, BAAM, AMPS, and NaCl concentrations and the pH value on the apparent viscosity of the copolymers were studied. The solution viscosities increased sharply when the copolymer concentration was higher than the critical associating concentration. The apparent viscosities of aqueous solutions of poly(N‐arylalkylacrylamide‐co‐acrylamide‐co‐2‐acrylamide‐2‐methylpropanesulfate) (PBAMS) increased with increasing BAAM and AMPS concentrations. PBAMS exhibited good salt resistance. With increasing pH, the apparent viscosities first increased and then decreased. Dilute PBAMS solutions exhibited Newtonian behavior, whereas semidilute aqueous and salt solutions exhibited shear‐thickening behavior at a lower shear rate and pseudoplastic behavior at a higher rate. Upon the removal of shear, the aqueous solution viscosities recovered and became even greater than the original viscosity, but the salt solution viscosities could not recover instantaneously. The elastic properties of PBAMS solutions were more dominant than the viscous properties, and this suggested a significant buildup of a network structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 316–321, 2005
Photoinitiating free‐radical polymerization electron‐transfer pairs applying amino acids and sulfur‐containing amino acids as electron donors
Authors: ścigalski Franciszek , Pączkowski Jerzy 
Published: April 2005

AbstractA series of free‐radical polymerization initiation systems, based on xanthene dyes as the absorbing chromophores [Rose bengal derivative, 3‐(3‐methylbutoxy)‐5,7‐diiodo‐6‐fluorone and 3‐acetoxy‐2,4,5,7‐tetraiodo‐6‐fluorone] and sulfur‐containing amino acids as the electron donors, were investigated. The photoredox pair xanthene dye/sulfur‐containing amino acid was effectively used for photoinitiation of free‐radical polymerization of the mixture composed of poly(ethylene glycol)diacrylate–1% NH4OH (3 : 1). The highest initiating efficiencies were observed for the system composed of methionine derivatives as the electron donor. The mechanism of photoinduced electron transfer between sulfur‐containing amino acids and triplet state of xanthene dye was investigated using laser‐flash and steady‐state photolysis techniques. Based on photochemistry of xanthene dyes, photochemistry of sulfur‐containing amino acids, and obtained results, the mechanism describing the major processes occurring during the photoinitiated polymerization by a photoinduced intermolecular electron‐transfer process was postulated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 358–365, 2005
A brief review on fire retardants for polymeric foams
Authors: Wang J. Q. , Chow W. K. 
Published: April 2005

AbstractFire retardants are briefly reviewed with reference to commonly available polymeric foams. Both physical and chemical aspects of intumescent fire retardants are summarized. New products based on nanocomposites are introduced as well. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 366–376, 2005
Expansion space and thermal stability of microencapsulated n‐octadecane
Authors: Zhang X. X. , Tao X. M. , Yick K. L. , Fan Y. F. 
Published: April 2005

Abstract5.0–50.0 vt% of cyclohexane was mixed with 95.0–50.0 vt% of n‐octadecane as the oil‐phase during the emulsion process in the in situ polymerization of melamine‐formaldehyde. By heat‐treating the microcapsules in an oven at 100°C, the cyclohexane was removed and expansion space was formed inside the microcapsules. The microcapsules were characterized by using FTIR, SEM, DSC, TGA, and gas chromatography. When the microcapsules are heat‐treated at temperatures higher than 180°C, Tm, ΔHm, Tc, and ΔHc of the microcapsules decrease. The attenuation of enthalpy of the microcapsules containing expansion space is obviously lower than that of the control sample, however. The permeability of the microcapsule shell decreases with the increase of cyclohexane content. There is a maximum between the thermal stabilities of the microcapsules and the cyclohexane contents. The microcapsules synthesized with 30.0–40.0 vt% of cyclohexane have the highest thermal stabilities, with 230°C and 289°C in air and nitrogen atmosphere, respectively. The thermal stable temperatures are approximately 67°C and 102°C higher than that of the control sample, respectively. The expansion space inside the microcapsules allows the n‐octadecane to expand in the temperature rising process and exert lower pressure to the shell, therefore keeping the shell intact and increasing the thermal stabilities of the microcapsules. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 390–396, 2005
Synthesis and characterization of polyethylene‐octene elastomer/clay/biodegradable starch nanocomposites
Authors: Liao Hsin‐Tzu , Wu Chin‐San 
Published: April 2005

AbstractThe aim of this work is the production of new nanocomposites from metallocene polyethylene‐octene elastomer (POE), montmorillonite and biodegradable starch by means of a melt blending method. Characterizations of clay, modified clay, POE, POE‐g‐AA, and the hybrids produced from polymer, clay, and/or starch were performed by X‐ray diffraction (XRD) spectroscopy, Fourier transform infrared (FTIR) spectrophotometer, differential scanning calorimetry (DSC), thermogravimetry analyzer (TGA), scanning electron microscope (SEM), and Instron mechanical tester. As to the results, organophilic clay can be well dispersed into acrylic acid grafted polyethylene‐octene elastomer (POE‐g‐AA) in nanoscale sizes since cetyl pyridium chloride is partially compatible with POE‐g‐AA and allows POE‐g‐AA chains to intercalate into clay layers. Based on consideration of thermal and mechanical properties, it is also found that 12 wt % of clay content is optimal for preparation of POE‐g‐AA/clay nanocomposites. The new partly biodegradable POE‐g‐AA/clay/starch hybrid could obviously improve the elongation and the tensile strength at break of the POE‐g‐AA/starch hybrid since the former can give the smaller starch phase size and nanoscale dispersion of silicate layers in the polymer matrix. The nanocomposites produced from our laboratory can provide a stable tensile strength at break when the starch content is up to 40 wt %. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 397–404, 2005
Thermodynamic study of a pressure‐temperature phase diagram for poly(N‐isopropylacrylamide) gels
Authors: Kato Eiji 
Published: April 2005

AbstractThe volume change, ΔVh,, accompanying the hydrophobic hydration associated with the volume phase transition in Poly(N‐isopropylacrylamide) gels was measured by a simple method. The hydration accompanies a negative ΔVh′−2.5 cm3/mol. The P‐T phase diagram, the coexistence curve, for the gels was determined from the swelling ratio‐pressure curves up to 350 MPa for various constant temperatures. The contour of the coexistence curve is shaped like an ellipsoid on the P‐T plain, which is a feature peculiar to the reversible pressure‐temperature denaturation of a protein. The thermodynamic analysis of the Clausius–Clapeyron relation for the measured ΔVh elucidates that the obtained coexistence curve represents the phase boundary between thermodynamic different phases like the two phases, native and denatured, of a protein and gives the transition enthalpy, ΔH, 5.2kJ/mol by estimate, which well coincides with the transition heat measured by a calorimetric method. Considering the volume‐dependent free energy, Δvmi · P, for the mixing free energy of the gel, we can fit the calculated curve to the measured swelling ratio‐pressure curve of PNIPA gels. The value of Δvmi changes the sign from negative to positive above around 100MPa. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 405–412, 2005
Multislice CT to evaluate coronary stent patency: A case report
Authors: Soon Kean H. , Bell Kevin W. , Lim Yean L. 
Published: April 2005

AbstractThis is a case report on the ability of 16‐slice computed tomography in assessing the patency of coronary stent and diagnosing an asymptomatic stenotic lesion with soft plaque morphology. These findings were confirmed with a selective coronary angiography. Identification of lesion morphology facilitated our decision on prophylactic and direct stenting to the lesion. © 2005 Wiley‐Liss, Inc.
Effect of Bin Time on the Photon Counting Histogram for One‐Photon Excitation
Authors: Perroud Thomas D. , Huang Bo , Zare Richard N. 
Published: April 2005

AbstractWe have demonstrated that our photon counting histogram (PCH) model with the correction for one‐photon excitation is valid at multiple bin times. The fitted apparent brightness and concentration follow the three‐dimensional diffusion model. More importantly, the semi‐empirical parameter, F, introduced in the PCH model for one‐photon excitation to correct for the non‐Gaussian shape of the observation volume, shows small variations with different bin times. These variations are consistent with the physical interpretation of F, and they do not affect the resolving power of the PCH model for one‐photon excitation. Based on these findings, we extend the time‐independent PCH analysis to time‐dependent photon counting multiple histograms (PCMH). This model considers the effect of bin time on the PCH parameters in a way that is similar to fluorescence intensity multiple distribution analysis (FIMDA). From the same set of data, PCMH extracts time‐dependent parameters (diffusion time and triplet‐state relaxation time) as well as time‐independent parameters (true specific brightness and true average number of molecules). Given a three‐ to fourfold experimental difference in molecular brightness, we find that PCMH can resolve each species in a two‐species sample and extract their respective diffusion times even when fluorescence correlation spectroscopy cannot.
Photophysical Properties of a Tetraphenoxy‐Substituted Perylene Bisimide Derivative Characterized by Single‐Molecule Spectroscopy
Authors: Lang Erwin , Würthner Frank , Köhler Jürgen 
Published: April 2005

AbstractWe present a detailed study of the photophysical properties of a tetraphenoxy‐substituted perylene bisimide derivative. The probe molecules were immobilized in a Shpol'skii matrix of hexadecane and investigated by single‐molecule spectroscopy at cryogenic temperatures. By using single‐molecule spectroscopic techniques we reveal the triplet substate kinetics and the fluorescence quantum yield, and we provide an estimate for the S1–S0 transition dipole moment.
Electron Transfer at the Single‐Molecule Level in a Triphenylamine–Perylene Imide Molecule
Authors: Bell Toby D. M. , Stefan Alina , Masuo Sadahiro , Vosch Tom , Lor Marc , Cotlet Mircea , Hofkens Johan , Bernhardt Stefan , Müllen Klaus , van der Auweraer Mark , Verhoeven Jan W. , De Schryver Frans C. 
Published: April 2005

AbstractPhotoinduced electron transfer (ET) processes in a donor–acceptor system based on triphenylamine and perylene imide have been studied at the single‐molecule (SM) and ensemble levels. The system exists as two isomers, one of which undergoes forward and reverse ET in toluene with decay constants of 3.0 and 2.2×109 s−1, respectively, resulting in the dual emission of quenched and delayed fluorescence while the other isomer remains ET‐inactive. The fluorescence of both isomers is heavily quenched in the more polar solvent, diethyl ether, by ET. A broad range of ET dynamics is seen at the SM level in polystryene with the two isomers nonresolvable indicating that the local nanoenvironment of the SMs varies considerably throughout the polymer matrix. Both the electronic coupling and the driving force for ET are shown to influence the ET dynamics. Many fluorescence trajectories of SMs show long periods (tens of milliseconds to seconds) where the count rate is attenuated either partly (a “dim” state) or to the background level (an “off‐time”). During these periods, the reduction or interruption of emission is attributed to cycles of rapid charge separation followed by charge recombination to the ground state reducing the fluorescence quantum yield of the SM.
Single Chromophore Spectroscopy of MEH‐PPV: Homing‐In on the Elementary Emissive Species in Conjugated Polymers
Authors: Schindler Florian , Lupton John M. 
Published: April 2005

AbstractLow‐temperature, single‐molecule spectroscopy can provide unparalleled access to the primary emissive species of conjugated polymers. We demonstrate this with the example of one of the most commonly studied polymers, poly(2‐methoxy‐5‐(2′‐ethylhexoxy)‐1,4‐phenylenevinylene), MEH‐PPV, which is shown to exhibit sharp fluorescence signatures over one hundred times narrower than the ensemble. These unprecedented narrow emission features can be assigned to single chromophores on the polymer chain, which are selectively addressed by the narrow band excitation. As with organic dye systems, the emission from single chromophores is not static with time, but shows a substantial spectral fluctuation. We find that, for single chromophores, this spectral fluctuation always follows a universal Gaussian statistical distribution. High‐resolution spectroscopy provides unique insight into low‐energy vibrational modes in the polymer emission, which are generally inaccessible with conventional spectroscopic methods such as site‐selective fluorescence or Raman spectroscopy. Interchromophoric coupling can also occur owing to the flexible nature of the polymer backbone. This leads to substantial spectral broadening and a loss of resolution in the vibronic progression. We observe reversible switching within one single molecule between narrow and broad emission, which directly correlates with a discrete switching in emission intensity. We conclude that one and the same single molecule can support aggregated and nonaggregated emission, that is, emission from isolated and aggregated chromophores in one single molecule, rather than the tendency for aggregate emission being intrinsic to the molecule.
Vibronic Excitation of Single Molecules: A New Technique for Studing Low‐Temperature Dynamics
Authors: Kiraz Alper , Ehrl Moritz , Hellriegel Christian , Bräuchle Christoph , Zumbusch Andreas 
Published: April 2005

AbstractHerein, we present vibronic excitation and detection of purely electronic zero‐phonon lines (ZPL) of single molecules as a new tool for investigating dynamics at cryogenic temperatures. Applications of this technique to study crystalline and amorphous matrix materials are presented. In the crystalline environment, spectrally stable ZPLs are observed at moderate excitation powers. By contrast, investigations at higher excitation intensities reveal the opening of local degrees of freedom and spectral jumps, which we interpret as the observation of elementary steps in the melting of a crystal. We compare these results to spectral single‐molecule trajectories recorded in a polymer. The way in which much more complicated spectral features can be analysed is shown. Surprisingly, pronounced spectral shifts on a previously not accessible large energy scale are observed, which are hard to reconcile with the standard two‐level model system used to describe low‐temperature dynamics in disordered systems.
Electrochemical and Spectroscopic Investigations of Immobilized De Novo Designed Heme Proteins on Metal Electrodes
Authors: Albrecht Tim , Li Wenwu , Ulstrup Jens , Haehnel Wolfgang , Hildebrandt Peter 
Published: April 2005

AbstractOn the basis of rational design principles, template‐assisted four‐helix‐bundle proteins that include two histidines for coordinative binding of a heme were synthesized. Spectroscopic and thermodynamic characterization of the proteins in solution reveals the expected bis‐histidine coordinated heme configuration. The proteins possess different binding domains on the top surfaces of the bundles to allow for electrostatic, covalent, and hydrophobic binding to metal electrodes. Electrostatic immobilization was achieved for proteins with lysine‐rich binding domains (MOP‐P) that adsorb to electrodes covered by self‐assembled monolayers of mercaptopropionic acid, whereas cysteamine‐based monolayers were employed for covalent attachment of proteins with cysteine residues in the binding domain (MOP‐C). Immobilized proteins were studied by surface‐enhanced resonance Raman (SERR) spectroscopy and electrochemical methods. For all proteins, immobilization causes a decrease in protein stability and a loosening of the helix packing, as reflected by a partial dissociation of a histidine ligand in the ferrous state and very low redox potentials. For the covalently attached MOP‐C, the overall interfacial redox process involves the coupling of electron transfer and heme ligand dissociation, which was analyzed by time‐resolved SERR spectroscopy. Electron transfer was found to be significantly slower for the mono‐histidine‐coordinated than for the bis‐histidine‐coordinated heme. For the latter, the formal heterogeneous electron‐transfer rate constant of 13 s−1 is similar to those reported for natural heme proteins with comparable electron‐transfer distances, which indicates that covalently bound synthetic heme proteins provide efficient electronic communication with a metal electrode as a prerequisite for potential biotechnological applications.
Energy Transfer in Single‐Molecule Photonic Wires
Authors: García‐Parajó María F. , Hernando Jordi , Mosteiro Gabriel Sanchez , Hoogenboom Jacob P. , van Dijk Erik M. H. P. , van Hulst Niek. F. 
Published: April 2005

AbstractMolecular photonics is a new emerging field of research around the premise that it is possible to develop optical devices using single molecules as building blocks. Truly technological impact in the field requires focussed efforts on designing functional molecular devices as well as having access to their photonic properties on an individual basis. In this Minireview we discuss our approach towards the design and single‐molecule investigation of one‐dimensional multimolecular arrays intended to work as molecular photonic wires. Three different schemes have been explored: a) perylene‐based dimer and trimer arrays displaying coherent exciton delocalisation at room temperature; b) DNA‐based unidirectional molecular wires containing up to five different chromophores and exhibiting weak excitonic interactions between neighbouring dyes; and c) one‐dimensional multichromophoric polymers based on perylene polyisocyanides showing excimerlike emission. As a whole, our single‐molecule data show the importance of well‐defined close packing of chromophores for obtaining optimal excitonic behaviour at room temperature. Further improvement on (bio)chemical synthesis, together with the use of single‐molecule techniques, should lead in the near future to efficient and reliable photonic wires with true device functionality.
Single‐Molecule Manipulation Measurements of DNA Transport Proteins
Authors: Saleh Omar A. , Allemand Jean‐François , Croquette Vincent , Bensimon David 
Published: April 2005

AbstractSingle‐molecule measurements of the manipulation of three different DNA motor proteins are reviewed. Despite some differences in the structure and mechanisms of the proteins, there are consistent phenomenological themes that relate them. Each of the experiments described represents a significant advance in the understanding of the mechanisms of DNA transport.
Two‐Hybrid Fluorescence Cross‐Correlation Spectroscopy Detects Protein–Protein Interactions In Vivo
Authors: Baudendistel Nina , Müller Gabriele , Waldeck Waldemar , Angel Peter , Langowski Jörg 
Published: April 2005

AbstractFluorescence cross‐correlation spectroscopy (FCCS) uses the correlated motion of two distinct fluorophores to detect their interaction. Whereas FCCS has been used with chemically or genetically labeled interaction partners in vitro, FCCS has never been demonstrated in vivo between two autofluorescent proteins. At least one reaction partner was always chemically labeled. Fos and Jun, two components of the AP‐1 transcription factor, are known to exert their function as a dimer and can therefore serve as a reference for dimer formation. Expressing fusion proteins between Fos and the enhanced green fluorescent protein (EGFP), as well as Jun and the monomeric red fluorescent protein 1 (mRFP1) in HeLa cells, we show here, for the first time, in vivo FCCS detection of protein–protein interactions. The mobility of the dimerized species is slow, indicating that DNA‐binding might stabilize dimerization. The technique has rich potential applications for the rapid screening of protein–protein interactions in vivo, which are able to clarify events during the whole life of cells.