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Pyrrole and 3-alkylpyrroles were grafted via chemical oxidative polymerisation with FeCl 3 to copolymers of methyl methacrylate and ω-(N-pyrrolyl)alkyl methacrylates incorporating varying amounts of ω-(N-pyrrolyl)alkyl methacrylates with varying alkyl chain lengths. The electrical conductivity of the resultant graft copolymers attained 10 –4 -10 –3 S cm – , with the length of the alkyl spacers in ω-(N-pyrrolyl)alkyl methacrylates having little influence on the conductivity. A longer alkyl spacer, however, resulted in a lower glass transition temperature for the resulting graft copolymers. The graft copolymers from pyrrole were insoluble whilst those arising from 3-alkylpyrroles were completely soluble in common organic solvents even in their doped states.

The oxidative polymerisation of o- and m-aminobenzenesulfonic acid has been achieved for the first time at high pressures to yield fully sulfonated polyaniline (SPANI) which is self-doping, water soluble and electrically conducting.

A series of polymers containing alternating phenylene and symmetrically substituted bithiophene repeat units have been synthesized and characterized using UV-Vis absorption spectroscopy, fluorescence emission spectroscopy, conductivity measurement and thermal analyses. The results reveal that the polymers have a bandgap energy of 2.5 eV and a fluorescence quantum yield of up to 26% with respect to quinine sulfate. The polymers show a maximum conductivity of 0.2 S cm −1 upon doping with I 2 and display good thermal stability in both neutral and doped states. The influence of alkyl chain size on conductivity, spectral behavior and thermal stability is discussed.

A series of poly[3,3′-dialkyl-2,2′-(ethyne-1,2-diyl)bis(thiophene)]s, comprising a rigid carbon-carbon triple bond between two bithiophene repeating units, were synthesized. The improved rigidity of the polymer backbone led to an increased fluorescent quantum yield in comparison to poly(3-alkylthiophene)s. A generic trend depicting decreasing Stokes shift in the fluorescence spectra with increasing pendant alkyl chain length was observed. The incorporation of the acetylenic spacer also resulted in a significant red shift in the absorption spectra in comparison to poly(3-alkylthiophene)s, corresponding to an increase in effective conjugation over the entire series of polymers. These polymers, upon doping with iodine or ferric chloride, gave electrical conductivity in the range of 10 0 to 10 –4 S cm –1 . Thermochromism studies showed a blue shift in absorption peak as the temperature changes from 25 to 180°C. The influence of alkyl chain length and the acetylenic spacer on the conductivity and UV-VIS absorption is also discussed. In situ electrochemical doping studies were monitored using UV-VIS-near infrared absorption spectroscopy and showed the evolution of polaron bands at around 1.4 eV.

In-situ polymerization of aniline in poly(vinylphosphonic acid) (PVPA) resulted in conductive polyaniline/PVPA blends with conductivities in the order of 10−2 S/cm. The blends were characterized by FTIR and UV-vis spectroscopy. Thermogravimetric analysis showed that the blends have good thermal stability.

Homopolymer of the symmetrical 3,3′-dibutylsulfanyl-2,2′-bithiophene (DBSBT) and copolymer of DBSBT with thiophene or bithiophene were prepared by nickel-catalyzed Grignard cross-coupling polymerization. These new solvent-processible regioregular copolymers have UV absorption maxima at about 500 nm in deposited film with a bandgap of 1.7–1.8 eV. They were readily doped by iodine and FeCl 3 to an electrical conductivity of 10 −3 –10 −2 S cm −1 . The polymers were characterized by FT-IR, NMR, X-ray photoelectron spectroscopy (XPS) spectra and cyclic voltammetry.

HCl-doped poly(o-anisidine ) (PANIS-HCl) and undoped poly(o-anisidine) (PANIS-base) were blended with poly(2-methyl-2-oxazoline) ( PMOx) or poly(2-ethyl-2-oxazoline) (PEOx) by solution casting from dimethyl sulfoxide. Blends containing 50 wt % or less of PANIS-HCI or PANIS-base were flexible and homogeneous. The glass transition temperature of the blend continuously shifted away from that of PMOx or PEOx with increasing PANIS-HCI or PANIS-base content, indicating miscibility. The shift in the T g value was larger for the PMOx blend than for the corresponding PEOx blend, suggesting a stronger interpolymer interaction in the former blend. Fourier transform infrared spectroscopic studies indicated the presence of specific interactions in the blends as evidenced by the changes of C=O and NH bands. Blends containing 50 wt % of PANIS-HCI showed conductivity of about 10 -4 S/cm.

Six kinds of materials, i.e. three self-assembled monolayers with terminal functional groups, a polymer incorporating acid groups, and two supramolecules of calixarene derivatives were applied as QCM sensor coatings for selective detection of organic amines in liquid phases. The specific interactions such as acid-base interaction, complexation interaction between the coating materials and analytes make the coated QCMs sensitive to organic amines in aqueous phase. The characteristics of the coated QCM sensors varied with the detection media because of the changes of the physico-chemical properties of the coating surfaces. Reversible changes in resonance frequency of the coated QCMs were found in neutral water solution for acid-base interaction and hydrogen bonding; quasi-irreversible frequency changes were found for salt-complex forming reaction in buffer solution. The relative selectivity of the analytes decreased with the increase of the hydrophobic part of the solute molecules in aqueous phases when acid-base interaction between the coating materials and analytes were employed. Shape-discrimination of analytes were achieved by the usage of supramolecules as sensor coatings owing to the cavity inclusion of the supramolecules.

Alkanethiols incorporating two different ω-functional groups (HS(CH2)6X; X=–OH(I), –OCH2Ph(II)) were coated onto the gold electrodes of quartz crystal microbalance (QCM) via the molecular self-assembly process to afford stable monolayers. The adsorption behaviour and interaction mechanism of organic vapours on QCM sensors coated with these self-assembled monolayers (SAM) were investigated. The hydrogen bonding and dipole-induced/dipole interaction between the vapour molecules and the coating layer enable excellent response of the sensors to organic vapours which bear strong electron attracting groups, such as acetic acid and alcohols. The response is rapid and the sensors exhibit good reversibility owing to the thin monolayer coating film. This work describes a convenient and simple method of preparing QCM vapour sensors.

The resonant frequency of piezoelectric quartz crystal microbalances (QCMs), coated with a polysiloxane film containing acidic functional groups was studied when the pH of aqueous solutions in contact with coatings was changed. The Δf vs. pH curves for the polymer coating indicated that the pKa values were about 7~8 (Ka is the ionization constant) and the transition region was around 3~4 pH units. The sorption characteristics of the crystal coated with polymer film were reported. These coated crystals were shown to behave as selective detectors for a range of organic amines in dilute aqueous solutions. The lower limits for reliable measurement using 10 MHz crystals coated with 15 kHz loading of OV-225 acid polymer were estimated to be at the ppm levels for primary amines and triethylamine in a pH 7.14 buffer solution and a water-ethanol ( v v = 96 4 ) solution. Linear responses were obtained in the concentration ranges of 10–270 ppm and 10–250 ppm for the pH 7.14 buffer and the water-ethanol solution, respectively.

Chemical sensors based on Langmuir—Blodgett (LB) films of poly( o -anisidine) (POA) have been investigated. POA, synthesized by chemical oxidation and mixed with stearic acid, was successfully transferred onto quartz crystal microbalance (QCM) sensors using the LB film technique and used as the active sensing material. The resulting QCM sensor can selectively detect and distinguish among fatty acid vapours such as formic acid, acetic acid, propionic acid and butyric acid. The results suggest that the response of QCM sensors to fatty acids is dependent on both molecular weight and steric hindrance factors. Moreover, the sensitivity of the QCM sensors to different types of organic vapours increases linearly with the number of LB monolayers coated, with a concurrent loss of selectivity.

A series of poly[3-(ω-hydroxyalkyl)thiophenes] was synthesized by chemical oxidative polymerization using FeCl 3 and characterized by FT-IR, thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). Upon doping with iodine the polymers attained electrical conductivities of between 0.5 and 38 S cm −1 . Electrical conductivities of doped samples were found to increase with alkyl chain lengths, being optimum for the octyl pendant moiety. Thereafter, the conductivity decreased, as the doping and dedoping for the polymers became more difficult. Increasing the hydrocarbon chain length of the pendant substituent also resulted in decreased thermal stability of the polymers. XPS results showed that some C–OH groups in the polymers were oxidized to CO in the polymerization process.

The miscibility of polyaniline (PANI) salts, doped with p-phenol sulfonic acid (PSA) or 5-sulfosalicylic acid (SSA), with poly(2-ethyl-2-oxazoline) (PEOx) was studied by differential scanning calorimetry (d.s.c.) and Fourier-transform infra-red spectroscopy (FTi.r.). D.s.c. measurements show a single glass transition temperature (Tg) for each of the blends containing 5–60 wt% of PANI. The Tg value shifts away from that of PEOx with increasing PANI content. FTi.r. studies show the presence of specific interactions between the polymers. The interaction in the PEOx/PANI SSA system is stronger than that in the PEOx/PANI-PSA system. Electrical conductivities of the blends, determined by four-point probe, range from 10−5 to 10−3 S cm−1.

A C 60 -supported Pd catalyst has been prepared by reaction between C 60 and Pd(OAc) 2 (PPh 3 ) 2 in toluene, to give the complex C 60 [Pd(OAc) 2 (PPh 3 )] 3 , followed by H 2 treatment at 523 K for 4 h. Catalytic quantities (1 mol%) promote hydrogenation of diphenylacetylene, phenylacetylene, cyclohexene and hex-1-ene to give 100% conversion to 1,2-diphenylethane, phenylethane, cyclohexane and hexane within 18, 13, 21 and 12 min, respectively. Hydrogenation of the same substrates under similar conditions using Pd on activated charcoal (10%) as catalyst gives similar yields but at a longer time (20, 18, 27 and 15 min, respectively). Both the Pd-C 60 catalyst and its precursor were characterised by thermogravimetry (TG), FTIR, mass spectrometry (MS), powder XRD, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM).

AIM: The results of the Asymptomatic Carotid Atherosclerosis Study (ACAS) study have provided the first scientific evidence that in patients with asymptomatic carotid stenosis greater than 60% carotid endarterectomy reduces the risk of stroke from 2% to 1% per year. The implications are that approximately 20 operations need to be performed in order to prevent 1 stroke in 5 years. The aims of the Asymptomatic Carotid Stenosis and Risk of Stroke (ACSRS) study are to identify a subgroup or subgroups at a risk for stroke higher than 4% and a group at a risk for stroke less than 1% per year using systemic and local risk factors (plaque characterization) in addition to the degree of stenosis. The aim of this paper is to present the protocol and the results of the quality control. METHODS: The ACSRS is a multicentre natural history study of patients with asymptomatic internal carotid diameter stenosis greater than 50% in relation to the bulb. The degree of stenosis is graded using multiple established ultrasonic duplex criteria. In addition, ultrasonic plaque characterization is performed and clinical risk factors and medications are recorded. Training is provided centrally. All carotid ultrasound examinations are recorded on video-tape which together with CT-brain scans and ECG are analysed at the coordinating centre with feedback information to partner centres. RESULTS: The video recordings and analysis of data centrally with feed back information have provided quality control with a significant improvement not only in the completion of data forms but also in the grading of internal carotid stenosis and plaque recordings using ultrasound. CONCLUSION: The high level of quality of data collected will add credibility to the results of the ACSRS study and may eventually promote the development of international standards of plaque imaging and characterization

Several bisacenaphthopyrazinoquinoxaline (BAPQ) based derivatives 1-3 were synthesized by condensation between the acenaphthenequinones and 1,2,4,5-tetraaminobenzene tetrahydrochloride. Their optical, electrochemical and self-assembling properties are tuned by different substituents. Among them, compound 3 possesses a homogeneously distributed low-lying LUMO due to the peripheral substitution with four cyano groups. The corresponding n-channel field effect transistors showed a field effect electron mobility of 5 × 10(-3) cm(2) V(-1) s(-1).

OBJECTIVE: To test the hypothesis that the size of a juxtaluminal black (hypoechoic) area (JBA) in ultrasound images of asymptomatic carotid artery plaques predicts future ipsilateral ischemic stroke. METHODS: A JBA was defined as an area of pixels with a grayscale value 10 mm(2) (P < .001). In a Cox model with ipsilateral ischemic events (amaurosis fugax, transient ischemic attack [TIA], or stroke) as the dependent variable, the JBA (8 mm(2)) was still significant after adjusting for other plaque features known to be associated with increased risk, including stenosis, grayscale median, presence of discrete white areas without acoustic shadowing indicating neovascularization, plaque area, and history of contralateral TIA or stroke. Plaque area and grayscale median were not significant. Using the significant variables (stenosis, discrete white areas without acoustic shadowing, JBA, and history of contralateral TIA or stroke), this model predicted the annual risk of stroke for each patient (range, 0.1%-10.0%). The average annual stroke risk was

This work describes how to tune the amphiphilic conformation of α-mangostin, a natural compound that contains a hydrophobic xanthone scaffold, to improve its antimicrobial activity and selectivity for Gram-positive bacteria. A series of xanthone derivatives was obtained by cationic modification of the free C3 and C6 hydroxyl groups of α-mangostin with amine groups of different pKa values. Modified structures using moieties with high pKa values, such as AM-0016 (3b), exhibited potent antimicrobial properties against Gram-positive bacteria. Compound 3b also killed bacteria rapidly without inducing drug resistance and was nontoxic when applied topically. Biophysical studies and molecular dynamics simulations revealed that 3b targets the bacterial inner membrane, forming an amphiphilic conformation at the hydrophobic-water interface. In contrast, moieties with low pKa values reduced the antimicrobial activity of the parent compound when conjugated to the xanthone scaffold. This strategy provides a new way to improve "hits" for the development of membrane-active antibiotics that target drug-resistant pathogens.

This paper reports on the integration of different modelling techniques to construct a unified conceptual model of structural evolution of the Pico del Águila anticline (External Sierras, southern Pyrenees, Spain). The structure is a well-known example of a detachment fold, which exhibits a N-S structural trend, perpendicular to the general structural trend of the southern Pyrenees (mainly E-W). Based on field observations of an unevenly distributed Triassic décollement, analogue modelling shows how to generate orogen-perpendicular structures which may result in transverse anticlines. The models show how contrasts between high and low friction patches in the basal décollement led to the formation of structures at high angle, centered over the high friction areas. Numerical models investigate the effect of a complex mechanical stratigraphy, characterized by an interlayering of competent and incompetent layers, plus syn-kinematic sedimentation in the fold growth. Based on field data and seismic interpretations, a 3D reconstruction and sequential geomechanical restoration of the Pico del Águila anticline suggests the coexistence of multiple folding mechanisms occurring simultaneously in different units and structural domains of the fold, leading to a complex strain pattern that can not be assessed by simplistic kinematic 2D approaches. By integrating the models with previous data in the region, the benefits and drawbacks of each modelling technique are discussed and an integrated model of structural evolution for the Pico del Águila anticline is presented. This enables a better comprehension of the structure as well as of the processes that drove the evolution of the N-S detachment anticlines in the External Sierras of the southern Pyrenees.

A miscible and electroactive polymer blend comprising polyaniline (PANI) as the conductive component and poly(vinyl acetate) (PVAc) as the thermoplastic component was prepared and characterized. The solution-processable conducting PANI was prepared by doping with p-phenolsulfonic acid (PSA), which also helps enhance its miscibility with PVAc through hydrogen-bonding interaction. Blends containing 50 wt% or less of PANI-PSA were miscible, as shown by glass transition temperature measurements and a low frequency shift of the carbonyl band of PVAc.

Nanoparticles of lanthanum-nickel, lanthanum-copper and barium-lead oxalates with the metal molar ratios of 1∶1, 2∶1 and 1∶1, respectively, have been successfully synthesized in inverse microemulsions. These metal oxalate particles of about 20 nm diameter were readily calcined into single-phase perovskite-type LaNiO3, La2CuO4 and BaPbO3. The calcination temperatures for these metal oxalates were generally 100–250°C lower than those for the metal oxalates prepared by the conventional aqueous solution precipitation method. The substantial reduction in the calcination temperatures is attributed to the formation of uniform, near-spherical nanoparticles of the metal oxalate precursors obtained by the unique inverse microemulsion technique.

Dynamic evolution of the submicrometer surface morphology of a copper grain undergoing electrodissolution in the “electroetching regime” has been monitored by in situ atomic force microscopy. Image...

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Based on quantum chemical calculations, we have established the relationship between the thermal stability and structural properties of ultrathin single-walled carbon nanotubes (SWCNTs). Our results on the heat of formation as a function of tube diameter predict a lower limit of 0.341 nm in diameter for experimentally observable SWCNTs. The absence of any distinctive minimum points on the heat of formation curve implies the experimental difficulties in obtaining uniform tubes. A detailed correlation between their curvature and chemical bonding properties was obtained for both the zigzag and armchair conformations.

Conducting polyaniline-coated BaSO4 composites have been synthesized in inverse microemulsions. The size of the composite particles ranged from about 10 to 20 nm in diameter. The formation and characterization of polyaniline coated on the surface of BaSO4 particles are discussed. The electrical conductivities (0.017–5 S cm−1) of the compacted powders of the doped polyaniline/BaSO4 composites increased almost linearly with the polyaniline content (5–22 wt.%) in the composites.

Poly(4-aminobiphenyl) synthesized both chemically and electrochemically were examined and compared by UV, FT-IR, X-ray photoelectron spectroscopy, thermogravimetry and differential scanning calorimetry. Results indicate that, in chemically synthesized samples, protonation of the nitrogen atoms occurs with chloride as the major counter ion, whilst, in the electropolymerized sample, concurrent oxidation of the biphenyl backbone was also observed. Conductivities of the electropolymerized and chemically synthesized polymers doped with FeCl 3 are 0.02 and 10 −6 S cm −1 , respectively. In addition, the chemically synthesized polymer in its base form is found to be dopable with iodine to a conductivity of 2 × 10 −4 S cm −1 . Scanning electron microscopy indicates a fibrous structure for the electropolymerized sample in contrast to the chemically synthesized form which has a granular to globular morphology, with the granules themselves made up of a fine network of fibrils.

Polyaniline morphology evolution in toluene has been observed for the first time. Various structures, including one-dimensional open-ended microtubes, three-dimensional solid microspheres and two-dimensional novel solid microplates were controllably synthesized in the same reaction system. The structures obtained were sensitive to oxidant concentration and molar ratio of monomer to oxidant. Solid microplates were mainly formed on the glass beaker wall and bottom, while tubes and spheres were produced in solution by employing reverse micelles as soft templates. Studies on the effect of reaction temperature, mechanical stirring and the addition of more acid were also carried out. FTIR and UV-Vis results showed that the PANI products were in the emeraldine form. The PANI film prepared from spheres exhibited hydrophobic property due to its rough surface covered with nanoscale dots and the large distribution of sphere diameters.

A glucose sensor was fabricated by the use of a microemulsion. The oil-in-water microemulsion was a simple three-component system consisting of a non-ionic surfactant, monomeric thiophene and aqueous buffer, without the use of an organic solvent. Enzyme was entrapped by the deposition of a thin layer of non-conducting polythiophene. This enzyme layer could be restored readily by the same microemulsion polymerization procedure when the enzyme was depleted. Application of this glucose sensor system in a flow-cell electrode was performed successfully. A linear range of over three orders of magnitude of glucose concentrations and a detection limit at the nanomole level were readily achieved. The capability of this sensor was demonstrated in connection with high-performance liquid chromatography for the direct sensing of glucose in fresh orange.

Human prostaglandin G/H synthase 1 and 2 were expressed in the baculovims expression system and purified to high levels. Both enzymes were glycosylated. PGHS-1 appeared to be homogeneous by SDS-PAGE analysis but two closely migrating bands were detected in PGHS-2 preparation which were evidently due to heterogeneity in glycosylation. The amino-acid sequence of the N-termini of both isoforms indicated that the signal sequences were efficiently cleaved by the insect cells. The recombinant human PGHS-1 and PGHS-2 possessed both cyclooxygenase and peroxidase activities. Both had high affinities for arachidonate as substrate and underwent self-inactivation during catalysis. The recombinant isoforms were not pharmacologically identical, since some NSAIDs were selective inhibitors of either PGHS-1 or PGHS-2. This is the first report of high levels of expression and purification of human PGHS isoforms. The recombinant enzymes are invaluable in developing potent PGHS-2 selective inhibitors that may be efficacious anti-inflammatory drugs with no or low levels of toxicity.

Highly conducting polyanilines (PANI) with thermal stabilities superior to that of polyaniline doped with HCl (PANI-HCl) have been prepared by postsynthesis treatment of the PANI-base with three different phosphonic acids, R-PA, where R=butyl (Bu), decyl (Dc), and benzyl (Bn). XPS results indicate the occurrence of free dopant molecules in the sample matrix, partial segregation of dopant species to the polymer surface, and participation of H 3 O + as counter charges to some of the dopant anions in these samples. IR data suggest minimal perturbation of the PANI vibrational states when Cl - is replaced by RPO 2 (OH)

The inverse microemulsion technique has successfully been used to synthesize lanthanum and nickel oxalate particles, which could readily be processed to form a fine LaNiO 3 powder. Under appropriate conditions, the metal oxalate coprecipitates were microhomogeneously mixed in the form of spherical particles about 20 nm in diameter. When these coprecipitated lanthanum and nickel oxalate particles were clacined at 800 °C for 20 h, fine LaNiO 3 powder was obtained. This powder was found to have the formula LaNiO 2.82–2.90 .

Cellulose nitrates were exposed to oxygen glow-discharge plasmas, and etch rates were determined. The changes in the surface chemistries of cellulose nitrates in these plasmas were investigated by X-ray photoelectron spectroscopy (XPS). These changes are discussed in terms of reactions at the surface that result in etching and those that do not. Etching in cellulose nitrates prepared by various nitration routes was compared, and the effect of degree of substitution (DOS) of the cellulose on etch rate was investigated.