A processability approach to agreement morphology in Arabic L2

This thesis tests the processability theory (PT) (Pienemann 1998;2005) predictions for agreement morphology in the acquisition of Arabic L2. The thesis has demonstrated that, apart from a few cases, learners of Arabic L2 acquired the test structures according to the PT's predictions for L2 sequential development.

High-performance composite from epoxy and glass fibers : morphology, mechanical, dynamic mechanical, and thermal analysis

Diglycidyl ether of bisphenol-A type epoxy resin cured with diamino diphenyl sulfone was used as the matrix for fiber-reinforced composites to get improved mechanical and thermal properties for the resulting composites. E-glass fiber was used for fiber reinforcement. The morphology, tensile, flexural, impact, dynamic mechanical, and thermal properties of the composites were analyzed. The tensile, flexural, and impact properties showed dramatic improvement with the addition of glass fibers. Dynamic mechanical analysis was performed to obtain the Tg of the cured matrix as well as the composites. The improved thermal stability of the composites was clear from the thermogravimetric analysis. Scanning electron micrographs were taken to understand the interfacial adhesion between the fiber and the matrix. The values of mechanical properties were compared with modified epoxy resin composite system. Predictive models were applied using various equations to compare the mechanical data obtained theoretically and experimentally.

Ion transport in polymer electrolytes containing nanoparticulate TiO2 : The influence of polymer morphology

Recent studies have shown that composite polymer electrolytes, formed by dispersing nanosized ceramic particles in polyether-based electrolytes, have improved ion transport properties as compared to their unfilled analogues. In the present study polymer electrolytes with different loadings of nano-sized ceramic particles (TiO₂) and different polymer chemistry and morphology have been investigated. Of special interest are filler induced effects on polymer, solvent and cationic mobility. Partly crystalline polymer electrolytes based on poly(ethylene oxide) have been compared to fully amorphous polymer electrolytes based on a polyether urethane, as well as gel electrolytes based on PMMA. ⁷Li pfg-NMR, linewidth and spin–spin relaxation times as well as ¹H pfg-NMR and spin–spin relaxation times, were measured as a function of temperature and composition. The ¹H spin–spin relaxation measurements reveal increased average polymer mobility with the addition of filler up to a maximum at 4 and 8 wt.% TiO₂ for the fully amorphous and the partly crystalline electrolytes, respectively. The ⁷Li linewidth measurements for the fully amorphous system show a broadening of the linewidth with addition of filler. Based on variable temperature measurements this broadening is interpreted as a result of the inhomogeneity introduced by the filler particles. Pulsed field gradient (pfg) diffusion measurements were employed to determine ion and solvent self-diffusion coefficients. In the case of the PMMA-based gel electrolyte and the fully amorphous electrolytes enhanced cation self-diffusion was observed upon addition of TiO₂.

Cerium acetylacetonates—new aspects, including the lamellar clathrate [Ce(acac)4]·10H2O

Reactions of CeCl₃·7H₂O and Ce(NO₃)₃·6H₂O with Naacac or NH₄acac in aqueous solution at 21 and 45 °C yielded the trihydrate [Ce(acac)₃(H₂O)₂]·H₂O and the dihydrate [Ce(acac)₃(H₂O)₂], respectively, whereas similar treatment of (NH₄)₂[Ce(NO₃)₆] gave the trihydrate at both temperatures. Desiccation of the hydrates over silica gel left the dihydrate unchanged, whereas the trihydrate underwent decomposition rather than dehydration. Aerial oxidation of [Ce(acac)₃(H₂O)₂] in CH₂Cl₂ and toluene yielded α-[Ce(acac)₄] and β-[Ce(acac)₄], respectively, the structure of the former being re-determined with improved precision. Careful treatment of aqueous (NH₄)₄[Ce(SO₄)₄] and Hacac (initially pH 1–2) with aqueous ammonia to pH 5 precipitated hydrated [Ce(acac)₄], from which [Ce(acac)₄]·10H₂O was isolated as unstable, light-sensitive single crystals, and the structure was determined. The complex is a laminar clathrate containing layers of Ce(acac)₄ molecules sandwiched between extensive hydrogen-bonded layers of water molecules which do not interact with the metal. Electrochemical experiments confirmed the unstable nature of hydrated Ce^III(acac)₃, while the reduction of [Ce(acac)₄] yielded well-defined cyclic voltammograms in acetonitrile and acetone, corresponding to a quasi-reversible process. For the [Ce^IV(acac)₄]/[Ce^III(acac)₄]⁻redox couple, a calculated reversible potential of 0.22±0.02 V versus SHE was obtained in acetone or acetonitrile (0.1 M Bu₄NPF₆) at both gold and glassy carbon electrodes. This potential is consistent with the ease of both oxidation and reduction of cerium acetylacetonate complexes as found in the synthetic studies.

The effect of solvent uptake on the relaxation behaviour, morphology and mechanical properties of a poly(ether ether ketone)/poly(etherimide) blend

The effects of solvent uptake on the relaxation behaviour, morphology and mechanical properties of poly(ether ether ketone) (PEEK), poly(etherimide) (PEI) and a 50/50 PEEK/PEI blend have been investigated. Amorphous films were immersed in acetone at 25°C, 35°C and 45°C until equilibrium uptake was achieved. The films were then examined by wide angle X-ray scattering (WAXS), differential scanning calorimetry (d.s.c.), dynamic mechanical relaxation spectroscopy and mechanical testing. WAXS and d.s.c. revealed that the degree of solvent induced crystallinity in PEEK is constant with immersion temperature, whereas the degree of induced crystallinity in the 50/50 blend is strongly temperature dependent. The dynamic mechanical studies confirmed that a significant decrease in glass transition temperature results from the plasticizing effect of the solvent and that solvent and thermally crystallized samples have different relaxation characteristics. Mechanical property tests showed that the yield stress and tensile strength of the blend are dominated by PEEK and the degree of crystallinity, while the modulus is more sensitive to the extent of plasticization.

Conducting polymers with fibrillar morphology synthesized in a biphasic ionic liquid/water system

The synthesis of poly(pyrrole), poly(terthiophene), and poly(3,4-ethylenedioxythiophene) with unusual fibrillar morphologies has been achieved by chemical polymerization in a biphasic ionic liquid/water system. Use of aqueous gold chloride as the oxidant, with the monomers dissolved in a hydrophobic ionic liquid, allows the polymerization to occur at the ionic liquid/water interface. The resultant conducting polymer fibrils are, on average, 50−100 nm wide and can be thousands of nanometers long. The polymers produced in this ionic liquid system are compared to those synthesized in a biphasic chloroform/water system.

Enhanced thermal properties and morphology of ion-exchanged polypyrrole films

The thermal stability of electrochemically prepared polypyrrole (PPy) films with p-toluenesulfonate (pTS) or perchlorate (ClO₄⁻) counterion (PPy/pTS and PPy/ClO₄⁻) is improved by simple treatment with aqueous sulfuric acid, sodium sulfate or sodium bisulfate. The degree of stabilization achieved depends on the solution, temperature and duration of treatment. Although the mechanism for improved stability is not yet clear, it is apparent that the level of ion exchange and the original polymer microstructure are important. A model for the conductivity decay as a function of thickness has been proposed. The early stages of ion exchange are not symmetrical, and diffusion is facilitated at the electrode side of the film. Furthermore, X-ray diffraction shows no evidence of morphological change after treatment of PPy/pTS (43 μm), but in PPy/pTS (12 μm) and PPy/ClO₄⁻ (41 μm) films an additional peak is indicative of more ordered structure following treatment. The glass transition temperature, T_g, of PPy/pTS and PPy/ClO₄⁻ films obtained by modulated differential scanning calorimetry is approximately 155°C.

The effect of seed morphology on the potential dispersal of aquatic macrophytes by the common carp (Cyprinus carpio)

1. The potential for seed dispersal by fish (ichthyochory) will vary among aquatic plants because of differences in seed size and morphology.

2. To examine how seed morphology influences the probability of dispersal by the common carp (Cyprinus carpio), we studied seed ingestion, retention time and subsequent egestion and germination of seeds of Sparganium emersum and Sagittaria sagittifolia, two aquatic plant species with similar sized but morphologically different seeds.

3. We compared dispersal probabilities between the two plant species, in which the probability of dispersal is assumed to be a function of the probabilities of seed ingestion, egestion and germination, and the dispersal distance is assumed to be a function of seed egestion rate over time.

4. We found that, although the soft seeds of S. sagittifolia had an approximately 1.5 times higher probability of being ingested by the carp than the hard seeds of S. emersum (83.15% ± 1.8% versus 56.16% ± 2.7%, respectively), the latter had an almost twofold higher probability of surviving the passage through the digestive tract (38.58% ± 2.7% versus 20.97% ± 1.5%, respectively). Patterns of seed egestion over time did not differ between the two plant species, despite the difference in seed morphology. Gut passage had a different effect on seed germination between plant species. Compared with non-ingested controls, seeds of S. emersum showed a 12.6% increase in germination and a 2.1 day acceleration in germination rate, whereas seeds of S. sagittifolia displayed a 47.3% decrease and 5.1 day delay, respectively.

5. Our results suggest that seed morphology affects the dispersal probability and postdispersal establishment, but not the dispersal distance, of aquatic plants that are dispersed by fish.

Independent and combined effects of exercise and vitamin D on muscle morphology, function and falls in the elderly

Regular exercise, particularly progressive resistance training (PRT), is recognized as one of the most effective strategies to prevent age-related muscle loss (sarcopenia), but its effects on muscle function are mixed. However, emerging data indicates that high velocity PRT (fast concentric muscle contractions) is more effective for improving functional outcomes than traditional PRT. In terms of falls prevention, high-challenging balance training programs appear to be most effective. There is also compelling evidence that supplemental vitamin D is an effective therapeutic option for falls prevention. The findings from a recent meta-analysis revealed that supplemental vitamin D at a dose of at least 700–1,000 IU/d or an achieved serum 25(OH)D level of at least 60 nmol/L was associated with reduced falls risk among older individuals. Based on these findings, it is possible that the combination of exercise and vitamin D could have a synergistic effect on muscle morphology and function, particularly since both interventions have been shown to have beneficial effects on type II “fast twitch” muscle fibers and systemic inflammation, which have both been linked to losses in muscle mass and function. Unfortunately however, the findings from the limited number of factorial 2 × 2 design RCTs indicate that additional vitamin D does not enhance the effects of exercise on measures of muscle morphology, function or falls risk. However, none of these trials were adequately powered to detect a “synergistic” effect between the two treatment strategies, but it is likely that if an exercise-by-vitamin D interaction does exist, it may be limited to situations when vitamin D deficiency/insufficiency is corrected. Further targeted research in “high risk” groups is still needed to address this question, and evaluate whether there is a threshold level of serum 25(OH)D to maximize the effects of exercise on muscle and falls risk.

Self-assembly and morphology in double crystalline diblock copolymer/homopolymer blends with competitive hydrogen bonding

Block copolymers are of particular interest due to their ability to form a rich variety of nanostructures via self-assembly [1]. The self-assembly via competitive hydrogen bonding is a novel concept which is based on the competition between different blocks of the block copolymer to form more than one kind of intermolecular interaction with the complimentary polymer in the system. Recently, Guo and co-workers have proven that careful selection of the polymers specifically the block copolymer, and the experimental conditions can lead to self-assembled structures in blends and complexes exhibiting competitive hydrogen bonding [2-5].