Dimensional change and elastic behavior of layered silicates and Portland cement paste

The role of water in hydrated Portland cement paste (hpc) is germane to understanding the nature of nanostructure – property relationships of the material. The irreversible dimensional changes of hpc and phase pure C–S–H that occur on wetting and drying are dissimilar to those observed for other silicate minerals of interest to cement science. This irreversibility in hpc is also observed for the modulus of elasticity parameter. Length change, mass change and modulus of elasticity isotherms (including drying–wetting cycles) were determined for specimens of hpc, Ca-montmorillonite and 1.4 nm tobermorite. Length change and modulus of elasticity versus mass loss curves were also obtained for phase pure C–S–H (C/S = 0.8, 1.0 and 1.5). All the isotherms exhibit significant irreversible behavior. Similarities and differences in the nature and character of the isotherms and the relevance of the C–S–H data are discussed. Inferences are made with respect to the nanostructural nature of hpc, its dimensional response in aqueous media and the correspondence in behavior of synthetic C–S–H and that formed in hpc. It is apparent that hpc has unique characteristics that are responsible for stability.     

Biosorption of Astrazone Blue basic dye from an aqueous solution using dried biomass of Baker's yeast

In this study dried biomass of Baker's yeast, Saccharomyces cerevisiae, is used as a sorbent for Astrazone Blue basic dye aqueous solution. Factors affecting the adsorption process: dye concentration, contact time, temperature and pH were investigated. The equilibrium concentration and the adsorption capacity at equilibrium were determined using three different sorption models namely: Langmuir, Freundlich and Temkin isotherms. It was found that increasing temperature and pH result in higher dye loadings per unit weight of the sorbent. The results gained from this study were described by Langmuir isotherm model better than Freundlich and Temkin isotherm models. The calculated heat of adsorption of the dye-yeast system indicates that the bio-sorption process is taking place by chemical adsorption and has an endothermic nature. The maximum adsorption capacity at 30 degrees C and pH 7 was calculated as 70 mg/g for dried biomass of Baker's yeast compared to 18.5mg/g for commercial granular activated carbon, indicating that dried biomass of Baker's yeast can be considered as a good sorbent material for Astrazone Blue solution.     

Optimized microvessel density analysis improves prediction of cancer stage from prostate needle biopsies

During angiogenesis in the chorioallantoic membrane (CAM) of the chick, capillary proliferation occurs primarily by intussusceptive growth. Previously, we reported that such growth in the CAM proceeded without substantial macromolecular extravasation. Neovascularization involving capillary sprout formation, on the other hand, has been associated with a concomitant loss of endothelial selectivity. Thus, the present study tested the hypothesis that endothelial selectivity during angiogenesis is dependent on the mode of microvascular growth. Capillary sprout formation occurs in peripheral regions of the CAM, in addition to the more centrally located areas of intussuceptive growth. In this study, angiogenic endothelial permselectivities were evaluated in these respective areas of CAM microvascular growth by intravital fluorescent microscopy of a graded series of FITC-dextrans. In both cases, the angiogenic endothelia restricted extravasation of macromolecules > or = 20 kDa. Furthermore, capillary sprout endothelia, like the intussusceptive CAM endothelia, remained tightly sealed at the junctional clefts. Thus, angiogenic endothelial permselectivity in the CAM is not dependent on the mode of microvascular growth. Whether distinct cellular mechanisms are operable in capillary endothelial sprouts of the CAM, relative to those of other proliferating sprout endothelia, remains to be tested.     

An FT-IR Study on Interfacial Interactions in Ethylene Copolymers/Aluminium Laminates in Relation to Adhesion Properties

The effect of three different functional groups in ethylene copolymers on the adhesion with aluminium was studied. The interface in polymer/metal laminates was analyzed by FT-IR, and the adhesion mechanism for each functional group was evaluated. Laminate samples were prepared by solution casting or by hotpressing polymeric film onto the aluminium substrate. In the latter case, the interface was exposed by solvent extraction. The interfacial structures developed by the different copolymers were correlated to the mechanical strength of hotpressed laminates, which was measured by a peel test. The polymer surfaces were further characterized by contact angle measurements.

Polar functional groups, carboxylic acid and butyl ester in hotpressed laminates were found to form Lewis acid/base interactions with the aluminium oxide. The strength of the interfacial interactions was correlated to the concentration and acidity/basicity of the group, the acid group being the most efficient. A silane functional group provided strong adhesion to the laminates at a much lower concentration than the polar groups. Silanols as well as Al-O-Si linkages were detected at the polymer/aluminium interface.     

Reduction of aqueous carbonate photocatalysed by treated semiconductors

Heterogeneous photocatalysed reduction of aqueous Na₂CO₃ solution (1 m) was achieved by using phthalocyanine-coated semiconductor powders (1–3% coating) as well as bare semiconductors. The suspensions were irradiated with 254 nm light from a low-pressure mercury lamp in a nitrogen atmosphere. The phthalocyanine dyes (Fe²⁺-Pc or Co²⁺-Pc) absorb > 80% of the 254 nm radiation and thus sensitize the semiconductor. The products of reduction (CH₃OH and HCHO) were determined spectrophotometrically. The CH₃OH yields obtained are much higher than the HCHO yields, due to a photocatalysed reduction of HCHO to CH₃OH. The CH₃OH yields from coated titania increased linearly with irradiation time over the period 6–18 h. However, the straight line does not pass through the origin, and it seems that a slowing-down occurs at times > 6 h. Titania coated with both dyes gave an optimum CH₃OH yield at 2% surface coating. At higher coating percentages, phthalocyanine screens the surface, thus reducing the light reaching the semiconductor. Changing the redox potential of the phthalocyanine dye by changing its central metal from Fe to Co affects the CH₃OH yields. The bare MoS₂ photocatalyst gave a much higher CH₃OH yield due to the characteristic behaviour of the semiconducting layer-type disulphide, distinguished from that of classical semiconducting materials. In the various semiconductors studied, it seems that there is no correlation between the position of the conduction band and the yield of CH₃OH. Such correlation was argued. Generally, a decrease in the yield of CH₃OH was observed as the band gap width of the semiconductor increased. The yields of the photoproduced CH₃OH generally increased with the percentage of light absorbed at 254 nm by the various semiconductors. Irradiation leads to the production of electrons in the conduction band of the semiconductor. It is likely that the photoproduced electrons reduce CO₃²- initially to HCOO- and then to HCHO and CH₃OH.     

Arabic stop consonants characterisation and classification using the normalized energy in frequency bands

In general, speech is made with sequences of consonants (fricatives, nasals and stops), vowels and glides. The classification of the stop consonants remains one of the most challenging problems in speech recognition. In this paper, we propose a new approach based on the normalized energy in frequency bands in the release and closure phases in order to characterize and classify the Arabic stop consonants (/b/, /d/, /t/, /k/ and /q/) and to recognize the CV syllable. Classification experiments were performed using decision algorithms on stop consonants C and CV syllables extracted from an Arabic corpus. The results yielded to an overall stop consonants classification of 90.27% and syllables CV recognition upper than 90% for all stops.     

Frequency identification of Hammerstein-Wiener systems with backlash input nonlinearity

International Journal of Control, Automation and Systems - The problem of system identification is addressed for Hammerstein-Wiener systems that involve memory operator of backlash type bordered by...     

An FT-IR Study on Interfacial Interactions in Ethylene Copolymers/Aluminium Laminates in Relation to Adhesion Properties

The effect of three different functional groups in ethylene copolymers on the adhesion with aluminium was studied. The interface in polymer/metal laminates was analyzed by FT-IR, and the adhesion mechanism for each functional group was evaluated. Laminate samples were prepared by solution casting or by hotpressing polymeric film onto the aluminium substrate. In the latter case, the interface was exposed by solvent extraction. The interfacial structures developed by the different copolymers were correlated to the mechanical strength of hotpressed laminates, which was measured by a peel test. The polymer surfaces were further characterized by contact angle measurements.

Polar functional groups, carboxylic acid and butyl ester in hotpressed laminates were found to form Lewis acid/base interactions with the aluminium oxide. The strength of the interfacial interactions was correlated to the concentration and acidity/basicity of the group, the acid group being the most efficient. A silane functional group provided strong adhesion to the laminates at a much lower concentration than the polar groups. Silanols as well as Al-O-Si linkages were detected at the polymer/aluminium interface.     

C–S–H (I)—A Nanostructural Model for the Removal of Water from Hydrated Cement Paste?

Helium gas is used as a nanostructural probe to investigate the structural changes in C–S–H (I) due to the removal of interlayer water. Changes in the 002 basal spacing are correlated with helium inflow characteristics. Similarities to helium inflow experiments conducted on hydrated Portland cement and C₃S pastes are discussed. Conclusions are drawn with respect to the viability of considering C–S–H (I) as a physical model for the drying of Portland cement and C₃S pastes.