Electrophoretic field gradient focusing: an investigation of the experimental parameters

Electrophoretic field gradient focusing has been used to separate the two oxidation states of myoglobin (Mb), and to separate Mb from bromophenol blue (BPB). Polyacrylamide and Sephadex were shown to be suitable packing materials whilst silica led to band broadening with Mb. BPB and Mb could be simultaneously focused apart using either a fixed 21-electrode setup or a dynamic 6-electrode setup. Using a dynamic three-electrode setup either analyte could be focused but not both simultaneously. It was shown that a higher ionic strength buffer in the separation channel compared to the coolant channel enhanced focusing between electrodes due to a conductivity gradient. Different running buffers were investigated and it was found that using a pH 8.6 buffer containing N,N,N-tris(hydroxymethyl)aminomethane (Tris) and phosphate ions the oxidation states of Mb could be separated but the separation of Mb from BPB was not as good as would be hoped for. Using a pH 8.6 buffer containing Tris, N-2-hydroxyethylpiperazine-N'-3-propanesulphonate and chloride ions as running buffer, BPB and Mb could be well separated but the two oxidation states of Mb merged.     

Withdrawal strength of fasteners in rice straw fibre-thermoplastic composites under dry and wet conditions

The withdrawal strength of nail and screw fasteners has been studied in rice straw fibre-thermoplastic composites. Two types of thermoplastic, virgin polyethylene (PE) and polypropylene (PP), were selected as separate composite matrices. Three levels of dry rice straw fibre, 45%, 60% and 75%, based on the composition by weight and passed through a 40-mesh size screen was mixed with the polymeric matrices without and with 2% (based on weight) maleic anhydride grafted polypropylene (MAPP) as coupling agent. A dry-blending method was used for compounding the materials. The 12 formulations for the polymer composites were used to prepare samples with dimensions 25 cm by 15 cm by 1 cm. The final composites were made by pressing the prepared mats between the hot plates of a compression press by employing combinations of temperature and pressure in three stages. After keeping the composites at room temperature for 15 days, the withdrawal strengths of nails and screws were measured according to BS Standard (CEN/TS 15534–1:2007) for dry composites. Withdrawal strengths were also measured after immersion of the composites for 24 h in distilled water (wet condition). The results showed that the withdrawal strength of screws is more than that of nails. Also, irrespective of the type of polymer, the percentage of rice straw fibre may significantly influence the withdrawal strength of fasteners, especially at the higher fibre to polymer ratios. Furthermore, it was found that in the wet condition the withdrawal strengths of the nail fasteners are reduced more (73.66%) than for the screws (28.9%).     

Predicting default of a small business using different definitions of financial distress

The paper introduces a number of risk-rating models for UK small businesses applying an accounting-based approach, which uses financial ratios to predict corporate bankruptcy. An enhancement to these models is considered through features typical to retail credit risk modelling. A common problem of default prediction consists in the relatively small number of bankruptcies or real defaults available for model-building. In order to expand the ‘default’ group beyond bankrupt companies, the paper considers adopting four different definitions of ‘a failing business’ by investigating combinations of financial distress levels. The impact of each default definition on the choice of predictor variables and on the model's predictive accuracy is explored. In addition, the paper examines the value of categorizing financial ratios used as predictor variables.     

Cyclo[(6-amino-6-deoxy-d-galactonic acid)4]: a new class of carbopeptoid-cyclodextrin

The formation of the 28-membered ring cyclo[(6-amino-6-deoxy-d-galactonic acid)₄] by cyclisation of a protected open chain fully hydroxylated nylon 6 linear tetramer in modest yield provides the first example of a new class of carbopeptoid-cyclodextrin.     

Measuring retail company performance using credit scoring techniques

This paper discusses models for evaluating credit risk in relation to the retailing industry. Hunt’s [Hunt, S.D., 2000. A General Theory of Competition. Sage Publications Inc., California] Resource–Advantage Theory of Competition is used as a basis for variable selection, given the theory’s relevancy to retail competition. The study focuses on the US retail market. Four standard credit scoring methodologies: Naïve Bayes, Logistic Regression, Recursive Partitioning and Artificial Neural Network, are compared with Sequential Minimal Optimization (SMO), using a sample of 195 healthy companies and 51 distressed firms over five time periods from 1994 to 2002.     

The elixir of life: using a maintenance, repair and replacement model based on virtual and operating age in the water industry

Processing equipment in the water industry is subject to decayand requires maintenance, repair and eventual replacement. Thechallenge of competition within the water industry and the accompanyingregulatory regime requires that actions be integrated and costeffective. This is an industry, which has considerable dataon the failure of its equipment, but until recently very fewmodels of the maintenance process have been built. This paper describes the context of this problem for cleanwater processing where the equipment is that required to purifywater. It proposes a model based on the virtual and operatingage of the components. The operating age reflects the true ageof the equipment while the virtual age allows for the cumulativeeffect of maintenance actions performed on the equipment. Themodel also allows for different types of equipment by describingdegradation by Cox's proportional hazards model. Thus the specialfeatures of the equipment and environment in which the equipmentoperates are described by a set of characteristics, which modifythe hazard rate of the failure time of the equipment. This approachusing Cox's model with virtual and operating age can be appliedto other processing industries including the gas industry andthe ‘dirty water’ side of the water industry. The model is formulated as a stochastic dynamic programmingor Markov decision process and the form of the optimal policyis determined. This shows that repair and replacement shouldonly be performed when the equipment has failed and describesgeneral conditions when replacement is appropriate. The optimalpolicy is calculated numerically using the value iteration algorithmfor a specific example based on data on failure.     

X-ray photoelectron spectroscopic studies of electrode surfaces using a new controlled transfer technique: Part II. Results for a molybdenum electrode and the curve fitting procedure

The surface of molybdenum metal was examined by XPS after exposure to gaseous and liquid systems and after electrochemical treatment. The latter being conducted in a specially designed electrochemical cell situated in a vacuum chamber attached to the main spectrometer chamber. The results show that a clean molybdenum metal surface is unaffected by oxygen gas and deoxygenated sulphuric acid. It was slightly oxidized by deoxygenated water and appreciably oxidized by oxygenated water. The Mo(VI) oxide is not observed after cathodic polarisation.     

Surface partitioning studies of N-methylcarbamate-treated post-harvest crops using SFE-HPLC-postcolumn reaction-fluorescence

The partitioning characteristics of selected carbamate insecticides (carbaryl, aldicarb, bendiocarb and pirimicarb) on five fruit and vegetable types were investigated. Post-harvest samples were surface-saturated with a methanolic-aqueous mixed carbamate spiking solution for a number of time periods. Samples were taken at 3, 7, 10 and 14 d, and extracted using supercritical CO2 at pressure = 300 atm modified with 10% dimethyl sulfoxide. Extracts were analysed by HPLC-postcolumn reaction-fluorescence detection at lambda ex = 330 nm and lambda em = 450 nm for N-methylcarbamates and at lambda ex = 315 nm and lambda em = 380 nm for pirimicarb. The relative partitioning of each insecticide between sample skin and flesh was investigated. This included the determination of both half-life and normalised matrix metabolic rate studies with respect to each carbamate. Multilinear regression (MLR) was applied to a number of insecticide and matrix-based variables to develop regression models for carbamate partitioning for each matrix type studied. Experimentally derived carbamate half-lives ranged from 3.6 d (carbaryl in pear flesh) to 8.0 d (bendiocarb in banana skin). Determinations of normalised metabolic rates were based on calculating the time period from the point of sampling through to the point where carbamate concentration was reduced to 5% of its initial value. These values ranged from 16.2 d (bendiocarb in potato skin) to 34.7 d (bendiocarb in banana skin). Although no practicable MLR partitioning models were obtained, it was found that the models created indicated that carbamate solubility in water (and hence log P) and the number of days in contact with the spiking solution were the most important parameters in model construction.