Sulphidation of electrodeposited cuprous oxide thin films for photovoltaic applications

Electrodeposited cuprous oxide thin films on indium-doped tin oxide (ITO) substrates were sulphided by exposing them to a spray of aqueous solution of sodium sulphide or to a mixture of hydrogen sulphide and nitrogen gases. Both methods produced light darker and darker films having different photovoltaic characteristics in a solar cell structure. The photovoltages produced by the light darker films under AM 1.5 illumination was negative as compared to the positive photovoltages produced by the darker films. Spectral response measurements revealed that most of the light darker films produced positive photovoltages in the shorter wavelengths and negative photovoltages in the longer wavelengths. However, some of the light darker films produced only the negative photovoltage for the entire spectral range and their photovoltaic properties were comparatively better. Darker films resulted in only the positive photovoltages in the entire spectral range. As a result of the sulphidation, the bulk crystal structure of the cuprous oxide thin films was not changed, however, the interfacial characteristics of the solar cell structure were modified.     

Copolymerization of methyl methacrylate and allyl acetate Part I. Rate of reaction

Free radical bulk copolymerization of methyl methacrylate (MMA) and allyl acetate (AAc) has been investigated using electron spin resonance (ESR) and FT–near infrared (FTNIR) spectroscopy. Data are used to evaluate the rate constants. The mole fraction of AAc plays an important role in the copolymerization of these two monomers. AAc not only delays the Trommsdorff effect but also increases the onset of percentage total conversion at which the Trommsdorff region begins. With AAc fraction 0.5 and higher, no Trommsdorff effect was observed. Inclusion of AAc into copolymer structure mainly occurs in the Trommsdorf region or when the AAc fraction in the comonomer feed is dominant. This is associated with a drop in the concentration of propagating radicals. However, ESR spectra indicate that the MMA propagating radical is predominant during the reaction. In the comonomer mixtures where a Trommsdorff region can be observed, the addition of AAc does not produce any significant change in k_p and k_t in the steady state region. Major changes in k_p and k_t are observed after the gel point and glassy state, respectively. © 2001 Society of Chemical Industry     

Numerical simulation of gas flow through porous sandstone and its experimental validation

Due to post-lithogenetic fracturing or weathering, sandstone can contain complex dual porosity structure, which makes it difficult to identify the fluid flow behaviour through it. The main objective of this study is to develop a three dimensional numerical model to simulate the flow of gas through porous sandstone under triaxial test condition. For the purpose of the modelling study, laboratory data which have been obtained from triaxial experiments conducted on porous sandstone samples [1] were used. In this study, a commercial reservoir simulator, COMET 3 was used to model the gas flow in the test samples. The COMET 3 model closely predicts the gas flow through the porous sandstone sample for the range of confining and gas injection pressures studied in the laboratory and for low gas flow rates (laminar flow). However the model fails at high flow rates (turbulent flows), due to the fact that the COMET 3 simulator uses Darcy’s law for flow simulations. Therefore, caution is required when interpreting the model results if the assumption of laminar flow does not apply to the flow conditions. An empirical relationship has been developed in this study which can be used to obtain an estimation of the flowrate when the flow has become non-Darcian. It is however important to be able to identify the transition point from Darcy to non-Darcy flow when the assumption of Darcian flow in COMET 3 no longer applies. Experiments conducted by Yi et al. [1] show very clearly the transition points, which are dependent on the injection and confining pressures. The model developed using COMET 3 appeared to give better prediction of the gas flow rate in sandstone sample, under triaxial test condition, than the COMSOL Multiphysics model given in the study in Yi et al. [1].     

DNA binding site characterization by means of Rényi entropy measures on nucleotide transitions.

In this work, parametric information-theory measures for the characterization of binding sites in DNA are extended with the use of transitional probabilities on the sequence. We propose the use of parametric uncertainty measures such as Rényi entropies obtained from the transition probabilities for the study of the binding sites, in addition to nucleotide frequency-based Rényi measures. Results are reported in this work comparing transition frequencies (i.e., dinucleotides) and base frequencies for Shannon and parametric Rényi entropies for a number of binding sites found in E. Coli, lambda and T7 organisms. We observe that the information provided by both approaches is not redundant. Furthermore, under the presence of noise in the binding site matrix we observe overall improved robustness of nucleotide transition-based algorithms when compared with nucleotide frequency-based method.     

Application of FT-IR and Raman spectroscopy for the study of biopolymers in breads fortified with fibre and polyphenols

Adding dietary fibres (DFs) and polyphenols (PPs) to bread is a convenient way to deliver the health benefits of DFs and PPs to consumers. In this study, we investigate the interactions among added pectin polysaccharides, PPs and bread components such as wheat proteins in different bread formulations. Two sets of breads with a 20% difference in the water content were prepared in the absence (Control), or presence of pectin and/or fruit PP extracts (Treated). Results show that adding pectin and PPs caused changes in the molecular conformations and polymer structure of wheat gluten and starch in the finished breads, especially in the secondary protein conformation (Amides I and II, as revealed by FTIR Spectroscopy). An increase of water content during dough formulation also affected secondary protein conformation. The Treated breads gained β-sheets in the protein's secondary conformation at the expense of β-turns, and contained more un-ordered conformations especially in the presence of berry PPs. These results were confirmed by complementary Raman spectroscopic measurements. Both hydrophobic and H bonding interactions occurred among bread components and the added PPs and pectin, which affected PP stability during breadmaking and the total extractable PP content of finished breads. Schematic Loop and Train models for breads enhanced with PPs and pectin are proposed that illustrate the possible conformational changes in wheat protein structure due to the presence of added PPs and pectin.     

Diffusivity of sulphur dioxide in green banana as a function of temperature and concentration

Effective diffusivity of sulphur dioxide uptake in green banana was measured as a function of temperature (20‐30°C) and concentration (6,000‐10,000 ppm) of dipping solutions. The effective diffusivity varied from 2.40×10^?10 to 19.05×10^?10 m²/s. Diffusivity increased with the increase of concentration and temperature of sodium metabisulfite solution. The estimated values can be used to design a sulfiting pretreatment process of green banana before drying.     

INVOLVEMENT OF WALL COMPONENTS IN ADSORPTION OF SILICONE ANTIFOAM TO SACCHAROMYCES CEREVISIAE

The ability of Saccharomyces cerevisiae NCYC 366 to adsorb polydimethylsiloxane (PDS), dispersed in an aqueous emulsion containing stearate emulsifiers and cellulose-based thickeners, is diminished after treatment with trypsin, KOH and HF; treatment with β-glucanase initially caused an increase in binding which diminished on prolonged incubation. Trypsin and KOH removed most of the mannan, protein and phosphorus from isolated walls, while exposure to β-glucanase removed about half of the glucan, protein and phosphorus. HF treatment removed most of the phosphorus but had little effect on the contents of other wall components. Cells treated with trypsin or β-glucanase had pH-mobility curves similar to those of untreated cells. Those treated with KOH or HF had lower mobilities at all pH values. Treatment of cells with each of the reagents except β-glucanase lowered their capacity to bind fluorescein-labelled antibody. The ability of cells to bind fluorescein-labelled concanavalin A was decreased only after trypsin and KOH treatment. Treatment of PDS-containing cells with trypsin, β-glucanase or KOH caused release of bound silicone, the effect being smallest with β-glucanase treatment. It is concluded that binding of PDS-containing antifoam to yeast mainly involves ionogenic groups in the wall phosphomannan-protein.     

Comparison of Structural Deterioration Models for Stormwater Drainage Pipes

Abstract:   Structural deterioration of pipes is the continuing reduction of load bearing capacity, which can be characterized through structural defects. Structural deterioration has been a major concern for asset managers in maintaining the required performance of stormwater drainage systems in Australia. Condition assessment using closed circuit television (CCTV) inspection is often carried out to assess the deteriorating condition of individual pipes. In this study, two models were developed using ordered probit and neural networks (NNs) techniques for predicting the structural condition of individual pipes. The predictive performances were compared using CCTV data collected for a local government authority in Melbourne, Australia. The significant input factors to the outputs of both models were also identified. The results showed that the NN model was more suitable for modeling structural deterioration than the ordered probit model. The hydraulic condition, pipe size, and pipe location were found to be significant factors for this case study.     

EVALUATION OF A COMPOSITE BASED ON HIGH-DENSITY POLYETHYLENE FILLED WITH SURFACE-TREATED HYDROXYAPATITE

Summary  Composites properties are directly related to the degree of interaction between the plastic matrix and the inorganic filler. In the present work, the improvement of the composite’s properties by means of the addition of surface-treated and untreated hydroxyapatite (STHA and HA, respectively) was studied. An ethylene-acrylic acid copolymer was melt blended with high-density polyethylene and HA (HDPE/HA/EA). A surface treatment was performed using an ethylene-acrylic acid (EA) copolymer for STHA₁ and acrylic acid (AA) for STHA₂. High-density polyethylene (HDPE) was also tested. STHA₁ and STHA₂ composites exhibited Young’s modulus values (556 and 558 MPa, respectively) 22 % higher than that of HDPE/HA (455 MPa) and 8 % higher than that of HDPE/HA/EA (520 MPa). Additionally, STHA composites showed both yield stress and strain (σ_STHA1= 23 MPa; ε_STHA1= 9 %; σ_STHA2= 22 MPa; ε_STHA2= 10 %) having a remarkably different behavior from that of the HA composites, which showed no yielding at all. TEM micrographs showed better filler dispersion when surface treatment was applied to HA. Yet, the presence of EA copolymer exhibited a poorer thermal stability. The crystallinity degree as well as the crystallization and melting temperatures showed no significant variation. Regarding in vitro evaluation, composites with HA and EA copolymer proved to have better cell adhesion at early stages. The results of the STHA composites could be attributed to the electrostatic interactions taking place between the ethylene-acrylic acid copolymer and the polar groups of the HA.