bluuebunny/crossref_metadata_2025 huggingface dataset:
High‐density polyethylene/ultrahigh‐molecular‐weight polyethylene blend. I. The processing, thermal, and mechanical properties
Authors: Lim K. L. K. , Ishak Z. A. Mohd , Ishiaku U. S. , Fuad A. M. Y. , Yusof A. H. , Czigany T. , Pukanszky B. , Ogunniyi D. S.
Published: April 2005

Various blend ratios of high‐density polyethylene (HDPE) and ultrahigh‐molecular‐weight polyethylene (UHMWPE) were prepared with the objective of determining their suitability as biomaterials. Although the presence of HDPE in the blends enabled melt processing, the presence of UHMWPE helped to improve the toughness of the resulting blends. The processability of the blends was investigated with the Brabender torque, which was used as an indication of the optimum blend conditions. The blends were characterized with differential scanning calorimetry. The mechanical tests performed on the blends included tensile, flexural, and impact tests. A 50:50 (w/w) blend yielded optimum properties in terms of the processability and mechanical properties. The tensile property of the 50:50 blend was intermediate between those of HDPE and UHMWPE, but the strain at break increased 200% in comparison with that of both neat resins. The energy at break of the 50:50 blend revealed an improvement in the toughness. The fracture mechanism was also investigated with scanning electron microscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 413–425, 2005
A study of localized curing of glass‐filled composites using microhardness measurements
Authors: Abedian B. , Garcia‐Godoy F. , Garcia‐Godoy F.
Published: April 2005

Extent of cure of hybrid composite systems is examined by conducting hardness measurements at different stages of the photopolymerization reaction and obtaining kinetic parameters that matched the experimental data. The materials are commercial dental composites based on bis[4‐(2‐hydroxy‐3‐methacryloyloxypropoxy)phenyl]propane resins with different photoinitiator concentrations as well as filler particle sizes and combinations. Samples (five per group) were made using nylon molds (2.5 × 5 mm) of the tested composites. The samples were light cured with a constant‐power light source for durations up to 20 s. After curing, all samples underwent Vicker's hardness testing of top and bottom surfaces. While there are significant differences in the polymerization behavior between the top and bottom locations for the tested composites, the corresponding growth exponent n, a kinetic parameter in the kinetic theory, is very close in all cases. For the tested materials the coefficient factor k is much lower for the bottom surfaces compared with the top surfaces. This reduction in the value of k is more severe for the material with a higher concentration of the photoinitiator as well as a higher percentage of glass filler particles in the wavelength range affecting the photopolymerization. It is argued that a relationship between k and the irradiation intensity can be used to quantify the decay of irradiated light with its penetration into the composites. The comparisons can be used to draw preliminary conclusions on the parameters controlling the effective depth of cure in a hybrid composite. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 426–431, 2005
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

Fluid 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

The 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

Copolymers 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

A 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

Fire 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

5.0–50.0 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

The 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

The 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

This 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

We 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

We 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

Photoinduced 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

Low‐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

Herein, 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

On 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

Molecular 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

Single‐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

Fluorescence 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.
Voltammetric Assay of Naproxen in Pharmaceutical Formulations Using Boron‐Doped Diamond Electrode
Authors: Suryanarayanan V. , Zhang Y. , Yoshihara S. , Shirakashi T.
Published: April 2005

The electrooxidation of naproxen was studied, for the first time, using boron‐doped diamond (BDD) electrode by cyclic and differential pulse voltammetry (CV and DPV) in nonaqueous solvent supporting electrolyte system. The results were also compared with glassy carbon electrode (GC) under the same conditions. Naproxen undergoes one electron transfer resulting in the formation of cation radical for the first electrooxidation step, which follows other chemical and electrochemical steps such as deprotonation, removal of another electron and the attack of nucleophile (ECEC mechanism). BDD electrode provided higher signal to background ratio, well resolved and highly reproducible cyclic voltammograms than the GC electrode. With a scan rate of 50 mV s−1 and pulse height of 50 ms, respectively, the DPV technique was able to determine the naproxen concentrations in the range of 0.5 to 50 μM with a detection limit of 30 nM. The influence of interference compounds namely 2‐acetyl‐6‐methoxy naphthalene (AMN) on naproxen oxidation can also be followed successfully. Moreover, the percentage of AMN present in the standard chemical form of a mixture containing naproxen can be found accurately. Rapidity, precise and good selectivity were also found for the determination of naproxen in pharmaceutical formulations.
Temporal resolving power of spin echo and gradient echo fMRI at 3T with apparent diffusion coefficient compartmentalization
Authors: Hulvershorn Justin , Bloy Luke , Gualtieri Eugene E. , Redmann Christopher P. , Leigh John S. , Elliott Mark A.
Published: April 2005

The temporal resolving power of blood oxygenation level‐dependent (BOLD) functional magnetic resonance imaging (fMRI) at 3T was investigated in the visual and auditory cortices of the human brain. By using controlled temporal delays and selective visual hemifield stimulation, regions with similar (left vs. right occipital cortex) and different (occipital cortex vs. auditory cortex) vascular architectures were compared. Estimates of the time‐to‐peak (TTP) of the BOLD hemodynamic response function (hrf) were obtained using a spin echo (SE) sequence and compared to those acquired using a traditional gradient echo (GE) sequence. The hrf TTP in the visual cortex was found to be 4.73 s and 4.21 s for GE and SE, respectively. The auditory cortex response was significantly delayed, with TTPs of 4.95 s and 4.51 s for GE and SE, respectively. The GE response was able to resolve visual stimuli separated by 250 ms, whereas SE could resolve stimuli 500 ms apart. Apparent‐diffusion‐coefficient (ADC) compartmentalization of the BOLD signal was applied to restrict the vascular sensitivity of the SE and GE sequences. Limiting the response to voxels with ADCs < 0.8 × 10−3 mm2/s improved the temporal resolving power of GE and SE BOLD to 125 ms and 250 ms, respectively. Hum Brain Mapp 25:247–258, 2005. © 2005 Wiley‐Liss, Inc.
Loss of heterozygosity of 1p in uveal melanomas with monosomy 3
Authors: Häusler Thomas , Stang Andreas , Anastassiou Gerasimos , Jöckel Karl‐Heinz , Mrzyk Stefanie , Horsthemke Bernhard , Lohmann Dietmar R. , Zeschnigk Michael
Published: April 2005

Gains and losses of chromosomes 1, 3, 6 and 8 are nonrandom chromosomal aberrations in uveal melanoma. Monosomy 3 is the most frequent abnormality and is associated with poor prognosis. To identify regions of allelic loss on the short arm of chromosome 1 and to investigate if these alterations contribute to uveal melanoma progression, we performed microsatellite analysis of 10 loci in 70 uveal melanomas. A total of 51 tumors were obtained from patients with clinical follow‐up data, 19 tumors were from recent patients without follow‐up. Loss of heterozygosity (LOH) of at least 1 marker was more frequent in tumors with monosomy 3 (40%) than in tumors with disomy 3 (10%). In particular, loss of the entire short arm of chromosome 1 was only observed in tumors with monosomy 3 (p = 0.0001). By comparing the extent of 1p LOH in all tumors with monosomy 3, we were able to define a smallest region of overlap (SRO) of approximately 55 Mb, which is flanked by markers D1S507 and D1S198. On the basis of our data and published cytogenetic data, we propose that 1p31 harbors genes involved in the progression of uveal melanoma with monosomy 3. © 2005 Wiley‐Liss, Inc.
Growth‐cycle features of East Asian countries: are they similar?
Authors: Girardin Eric
Published: April 2005

This paper uses regime‐switching techniques to examine the similarities of GDP growth‐cycle features of 10 East Asian countries. A third regime of rapid growth is relevant for most countries. In Japan, South Korea and Taiwan, there was no secular slowdown in growth since the rapid‐growth regime re‐emerged at some stage. Japan is special since it shares each of its features with different countries, while China shares almost all its features with most countries. Finally, the same countries that were correlated with Japan in the 1980s have been linked with China since the 1990s. Copyright © 2005 John Wiley & Sons, Ltd.
Bond market development and integration in ASEAN
Authors: Plummer Michael G. , Click Reid W.
Published: April 2005

The Association of Southeast Asian Nations (ASEAN) has focused increasingly on financial integration as part of its economic‐deepening agenda. This paper considers the challenges and opportunities associated with the creation of an ASEAN bond market. In addition to surveying the status quo of fixed‐income markets in the context of capital market development and integration in the region, the paper gauges the benefits that might be generated through, inter alia, financial market diversification and interest rate convergence. It also addresses approaches to the inevitable liquidity problem, such as via the creation of an ASEAN currency basket. Copyright © 2005 John Wiley & Sons, Ltd.
Response of the antioxidant defense system to tert‐butyl hydroperoxide and hydrogen peroxide in a human hepatoma cell line (HepG2)
Authors: Alía Mario , Ramos Sonia , Mateos Raquel , Bravo Laura , Goya Luis
Published: April 2005

The aim of this work was to investigate the response of the antioxidant defense system to two oxidative stressors, hydrogen peroxide and tert‐butyl hydroperoxide, in HepG2 cells in culture. The parameters evaluated included enzyme activity and gene expression of superoxide dismutase, catalase, glutathione peroxidase, and activity of glutathione reductase. Besides, markers of the cell damage and oxidative stress evoked by the stressors such as cell viability, intracellular reactive oxygen species generation, malondialdehyde levels, and reduced glutathione concentration were evaluated. Both stressors, hydrogen peroxide and tert‐butyl hydroperoxide, enhanced cell damage and reactive oxygen species generation at doses above 50 μM. The concentration of reduced glutathione decreased, and levels of malondialdehyde and activity of the antioxidant enzymes consistently increased only when HepG2 cells were treated with tert‐butyl hydroperoxide but not when hydrogen peroxide was used. A slight increase in the gene expression of Cu/Zn superoxide dismutase and catalase with 500 μM tert‐butyl hydroperoxide and of catalase with 200 μ hydrogen peroxide was observed. The response of the components of the antioxidant defense system evaluated in this study indicates that tert‐butyl hydroperoxide evokes a consistent cellular stress in HepG2. © 2005 Wiley Periodicals, Inc. J Biochem Mol Toxicol 19:119–128, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20061
Low levels of arsenite activates nuclear factor‐κB and activator protein‐1 in immortalized mesencephalic cells
Authors: Felix Kumar , Manna Sunil K. , Wise Kimberly , Barr Johnny , Ramesh Govindarajan T.
Published: April 2005

Degeneration of dopaminergic neurons is one of the major features of Parkinson's disease. Many redox‐active metals such as iron and manganese have been implicated in neuronal degeneration characterized by symptoms resembling Parkinson's disease. Even though, arsenic, which is another redox‐active metal, has been shown to affect the central monoaminergic systems, but its potential in causing dopaminergic cell degeneration has not been fully known. Hence, the present study was designed to investigate arsenic signaling especially that is mediated by reactive oxygen species and its effect on early transcription factors in dopamine producing mesencephalic cell line 1RB3AN27. These mesencephalic cells were treated with low concentrations of sodium arsenite (0.1, 0.5, 1, 5, and 10 μM) and incubated for different periods of time (0–4 h). Arsenite was cytotoxic at 5 and 10 μM concentrations only after 72‐h incubation period. Arsenite, in a dose‐dependent manner, induced generation of reactive oxygen species (ROS) and activation of early transcription factors such as nuclear factor‐κ B (NF‐κB) and activator protein‐1 (AP‐1) as shown by electro mobility shift assay. Incubation of antioxidants, either N‐acetyl‐L‐cysteine (50 μM) or α‐tocopherol (50 μM) with 1 μM arsenite, suppressed ROS generation. Arsenite at 1 μM concentration was sufficient for maximal activation of NF‐κB and AP‐1 activation. Time kinetics studies showed maximal activation of NF‐κB by 1 μM concentration of arsenite was seen at 120 min and correlated with complete degradation of Iκ Bα at 60 min. Similarly, maximal activation of AP‐1 by 1 μM concentration of arsenite occurred at 120 min. N‐acetyl‐L‐cysteine at 50 μM concentration inhibited arsenite‐induced NF‐κ B and AP‐1. In addition, arsenite was shown to induce phosphorylation of extracellular signal regulated kinase (ERK) 1/2 at concentrations of 1 μM and above. These results suggest that arsenite, at low and subcytoxic concentrations, appears to induce oxidative stress leading to activation of early transcription factors whereas addition of antioxidant inhibited the activation of these factors. © 2005 Wiley Periodicals, Inc. J Biochem Mol Toxical 19:67–77, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20062
In vivo and in vitro oxidative regulation of rat aryl sulfotransferase IV (AST IV)
Authors: Maiti Smarajit , Dutta Sangita Maiti , Baker Sharon M. , Zhang Jimei , Narasaraju Telugu , Liu Lin , Chen Guangping
Published: April 2005

Sulfotransferase catalyzed sulfation is important in the regulation of different hormones and the metabolism of hydroxyl containing xenobiotics. In the present investigation, we examined the effects of hyperoxia on aryl sulfotransferase IV in rat lungs in vivo. The enzyme activity of aryl sulfotransferase IV increased 3‐ to 8‐fold in >95% O2 treated rat lungs. However, hyperoxic exposure did not change the mRNA and protein levels of aryl sulfotransferase IV in lungs as revealed by Western blot and RT‐PCR. This suggests that oxidative regulation occurs at the level of protein modification. The increase of nonprotein soluble thiol and reduced glutathione (GSH)/oxidized glutathione (GSSG) ratios in treated lung cytosols correlated well with the aryl sulfotransferase IV activity increase. In vitro, rat liver cytosol 2‐naphthol sulfation activity was activated by GSH and inactivated by GSSG. Our results suggest that Cys residue chemical modification is responsible for the in vivo and in vitro oxidative regulation. The molecular modeling structure of aryl sulfotransferase IV supports this conclusion. Our gel filtration chromatography results demonstrated that neither GSH nor GSSG treatment changed the existing aryl sulfotransferase IV dimer status in cytosol, suggesting that oxidative regulation of aryl sulfotransferase IV is not caused by dimer–monomer status change. © 2005 Wiley Periodicals, Inc. J Biochem Mol Toxicol 19:109–118, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20064
Receptor activator of NF‐κB ligand protein expression in UMR‐106 cells is differentially regulated by parathyroid hormone and calcitriol
Authors: Dossing Debra A. , Stern Paula H.
Published: April 2005

Expression of the cytokine, receptor activator of NF‐κB ligand (RANKL), is stimulated by both parathyroid hormone (PTH) and calcitriol in osteoblasts. Most studies have examined the effects on RANKL mRNA, and less information is available on the protein products. We have determined the effects of PTH, the adenylate cyclase stimulator forskolin, and calcitriol, alone and in combination, on endogenous RANKL protein expression in UMR‐106 rat osteoblastic osteosarcoma cells by Western blotting and enzyme immunoassay (EIA). PTH and forskolin dose dependently increased a ∼52 kDa band in whole cell lysates that was detected by both C‐ and N‐terminal directed RANKL antibodies. Calcitriol treatment produced little or no expression of this ∼52 kDa band, but markedly increased the expression of a ∼32 kDa band that was only detected with an antibody directed to the N‐terminus of RANKL. An EIA based on RANKL binding to OPG detected a large increase in RANKL expression following calcitriol treatment, and much smaller increases with PTH or forskolin. The combination of PTH and calcitriol or forskolin and calcitriol elicited effects similar to those of PTH and forskolin alone, as detected by both Western blotting and EIA. In contrast to the effects on protein, all agents increased RANKL mRNA expression, with the greatest effects seen with the co‐treatments. The results indicate that PTH, likely through effects on cyclic AMP, has a different effect on RANKL processing than calcitriol. The ∼52 and ∼32 kDa RANKL products appear to interact differently with OPG, which could affect responses to the agents in target cells. © 2005 Wiley‐Liss, Inc.
Surface chemistry of wood‐based phosphoric acid‐activated carbons and its effects on adsorptivity
Authors: Baker FS , Daley RA , Bradley RH
Published: April 2005

The surface oxygen content of selected wood‐based phosphoric acid‐activated carbons was quantified using X‐ray photoelectron spectroscopy (XPS) and correlated with the residual bulk phosphate levels of the carbons and their adsorptivity in solution. The adsorption of Al3+, Cu2+, and para‐chlorophenol, respectively, from water decreased as a function of increasing surface oxygen content of the carbons. When the carbon of lowest surface oxygen content was oxidized with ozone to impart a surface oxygen content comparable to that of a carbon with a much higher phosphate level, adsorption of Al3+, Cu2+, and para‐chlorophenol from water decreased proportionally. The increase in polarity of the carbon surface was accompanied by a decrease in pH and appeared to be the dominant factor with respect to the adsorption of the target species from water. Copyright © 2005 Society of Chemical Industry
Bioremediation of polycyclic aromatic hydrocarbons: current knowledge and future directions
Authors: Bamforth Selina M , Singleton Ian
Published: April 2005

Polycyclic aromatic hydrocarbons (PAHs) are a class of organic compounds that have accumulated in the natural environment mainly as a result of anthropogenic activities such as the combustion of fossil fuels. Interest has surrounded the occurrence and distribution of PAHs for many decades due to their potentially harmful effects to human health. This concern has prompted researchers to address ways to detoxify/remove these organic compounds from the natural environment. Bioremediation is one approach that has been used to remediate contaminated land and waters, and promotes the natural attenuation of the contaminants using the in situ microbial community of the site. This review discusses the variety of fungi and bacteria that are capable of these transformations, describes the major aerobic and anaerobic breakdown pathways, and highlights some of the bioremediation technologies that are currently available. Copyright © 2005 Society of Chemical Industry
Assessment of the dyeing properties of pigments from Monascus purpureus
Authors: De Santis Diana , Moresi Mauro , Gallo Anna Maria , Petruccioli Maurizio
Published: April 2005

Monascus purpureus C322 was cultivated on well‐established production media to yield prevailingly red or orange pigment‐rich ethanolic extracts. Once these extracts had been diluted by an overall factor of 50, they were used as such to dye raw wool standard specimens differently premordanted using alum or stannic chloride. Independently of the mordant used, the specimens dyed with the red pigment‐rich extracts showed a pale red colour tending to pink, whereas the specimens dyed with the orange pigment‐rich extracts exhibited a more definite orange colour. By carrying out a few colourfastness standard tests (manual washing at 40 °C, acid and basic perspiration and hot pressing), stannic chloride‐premordanted wool specimens dyed with the red pigment‐rich extracts were found to be less resistant to acid and basic perspiration than their orange counterparts. Since the production of the orange pigment‐rich ethanolic extracts appeared to be more cost‐effective than that of their red counterparts, the former might support the present demand for colorants of natural origin in the textile sector. Copyright © 2005 Society of Chemical Industry
Ventricle and outflow tract of the African lungfish Protopterus dolloi
Authors: Icardo José M. , Brunelli Elvira , Perrotta Ida , Colvee Elvira , Wong Wai P. , Ip Yuen K.
Published: April 2005

We report a morphologic study of the heart ventricle and outflow tract of the African lungfish Protopterus dolloi. The ventricle is saccular and appears attached to the anterior pericardial wall by a thick tendon. An incomplete septum divides the ventricle into two chambers. Both the free ventricular wall and the incomplete ventricular septum are entirely trabeculated. Only a thin rim of myocardium separates the trabecular system from the subepicardial space. The outflow tract consists of proximal, middle, and distal portions, separated by two flexures, proximal and distal. The proximal outflow tract portion is endowed with a layer of compact, well‐vascularized myocardium. This portion is homologous to the conus arteriosus observed in the heart of most vertebrates. The middle and distal outflow tract portions are arterial‐like, thus being homologous to the bulbus arteriosus. However, the separation between the muscular and arterial portions of the outflow tract is not complete in the lungfish. A thin layer of myocardium covers the arterial tissue, and a thin layer of elastic tissue underlies the conus myocardium. Two unequal ridges composed of loose connective tissue, the spiral and bulbar folds, run the length of the outflow tract. They form an incomplete division of the outflow tract, but fuse at the distal end. The two folds are covered by endocardium and contain collagen, elastin, and fibroblast‐like cells. They appear to be homologous to the dextro‐dorsal and sinistro‐ventral ridges observed during the development of the avian and mammalian heart. Two to three rows of vestigial arterial‐like valves appear in the dorsal and ventral aspects of the conus. These valves are unlikely to have a functional role. The possible functional significance of the “gubernaculum cordis,” the thick tendon extending between the anterior ventricular surface and the pericardium, is discussed. J. Morphol. © 2005 Wiley‐Liss, Inc.
Solvent Induced Sphere Development in Symmetric Diblock Copolymer Thin Films
Authors: Peng Juan , Wei Yuhan , Wang Hanfu , Li Binyao , Han Yanchun
Published: April 2005

Summary: We follow the time development of the microdomain structure in symmetric polystyrene‐block‐poly(methyl methacrylate) (PS‐b‐PMMA) diblock copolymer thin films during acetone vapor treatment. Besides the highly ordered nanoscopic spheres or stripes as reported previously, a novel so‐called flower‐like pattern, which comprises six PS spheres and each PS sphere belongs to three “flowers” is formed. This finding is very helpful to discuss the highly ordered nanoscopic sphere formation process.

Transition from flower‐like structure to well‐ordered arrays of spheres, in which the flower‐like pattern, the transitional morphology, and the ordered spheres are in the portion A, B, and C, respectively.

image

Transition from flower‐like structure to well‐ordered arrays of spheres, in which the flower‐like pattern, the transitional morphology, and the ordered spheres are in the portion A, B, and C, respectively.
Branched/Crosslinked Sulfonated Polyimide Membranes for Polymer Electrolyte Fuel Cells
Authors: Yin Yan , Hayashi Shunsuke , Yamada Otoo , Kita Hidetoshi , Okamoto Ken‐Ichi
Published: April 2005

Summary: Branched/crosslinked sulfonated polyimide membranes incorporating superior mechanical properties, high proton conductivity, and excellent fuel cell performance were successfully developed. The resulting polymer electrolytes displayed conductivity values of about 0.2 S · cm−1 at 120 °C and 100% relative humidity. In a single H2/O2 fuel cell system at 90 °C, they exhibited reasonably high fuel cell performances comparable to that of Nafion 112.

The structure of the branched/crosslinked sulfonated polyimide membranes studied here.

image

The structure of the branched/crosslinked sulfonated polyimide membranes studied here.