Acid phosphatase in the tubers of Dioscorea species and its purification from the white yam (D. rotundata poir)

Acid phosphatase activity was determined in 15 cultivars from four species of yam. A 12-fold purification of the enzyme from Dioscorea rotundata (cv. chikakwondo) gave a homogeneous preparation as demonstrated by polyacrylamide gel electrophoresis. This enzyme preparation has an apparent molecular weight of 115 000 ±2000 and an optimum activity at a pH of 5·20 and a temperature of 50°C. The K_m of the enzyme is 3·81 mM with disodium p-nitrophenylphosphate (p-NNP) as a substrate. The energy of activation, heat of activation, energy of inactivation and heat of inactivation are 7·0, 6·4, 4·41 and 4·34 kcal M^?1, respectively. Although it has very little activity with most organic phosphoric acid esters, it is significantly inhibited by Ca²⁺, Hg²⁺ and EDTA and activated by Mg²⁺. The enzyme has a half-life of 50,17 or 13 days, respectively, when stored at 6-8°C, 0°C or room temperature (29±2°C).     

Electromagnetic Torque Estimation of a Three-Phase Induction Motor for Setting the Feedrate of a Milling Machine

In this paper, it presents a project of a fuzzy controller and a neural estimator to control a coordinate table powered by three-phase induction motor, aiming to implement an intelligent milling system. The position/speed control is performed using vector techniques of three-phase induction machines. The estimation of the motor electromagnetic torque is used for setting the feedrate of the table. The speed control is developed using TS （Takagi-Sugeno） fuzzy logic model and electromagnetic torque estimation using neural network type LMS （least mean square） algorithm. The induction motor is powered by a frequency inverter driven by a DSP （digital signal processor）. Control strategies are implemented in DSP. Simulation results are presented for evaluating the performance of the system.     

Influence of recovery conditions on apparent heat resistance of Bacillus stearothermophilus spores

The effects of post-treatment environmental factors on the heat resistance of Bacillus stearothermophilus spores (ATCC 12980, 7953, 15951 and 15952) were investigated. Nutrient Agar (NA), Antibiotic Assay Medium (AAM), Dextrose Tryptone Agar (DTA) and Tryptic Soy Agar (TSA) with Ca^{2+ added to a final concentration of 100 p.p.m. were used as recovery media. No significant differences were seen between D-values obtained except in the case of strain 12980 when comparing TSA with the other media and for strain 7953 comparing AAM and DTA. The optimum incubation temperature was slightly lower for heated than for unheated spores of} each strain, although, in general, 50 °C was adequate. Higher D-values were obtained at 50–55 °C. The effects of the pH of the medium in the range 5.0–7.0 and the addition of starch and phosphate on heat resistance have also been investigated. Maximum colony counts of heated spores were obtained at pH 7.0 and decreased as pH fell. D-values were significantly lower at pH ≤ 5.5. Increasing the concentration of phosphate in the recovery medium from 0 to 0.2% resulted in a progressive decrease in spore recovery and D-values. The addition of starch improved recoverability. The z-values obtained for the four strains studied under the different recovery conditions were similar with a mean value of 7.58 °C ± 0.28.     

Functionality Enhancement of Composite Cassava Flour in the Production of Maize Tuwo (A Non-fermented Maize-Based Food Dumpling)

The study was focused on the evaluation of textural and sensory quality enhancing functionality of cassava flour in the production of maize tuwo (a non-fermented maize-based food dumpling). The cassava flour was added to maize flour at the level of 5%, 10%, 15%, 20%, 25% and 30% (w/w), respectively. The bulk density and water holding capacity of maize/cassava flour mixes ranged from 0.77–0.83 g/cm³ and 1.91–2.05 g/g, respectively, while those of 100% maize flour were 0.84 g/cm³ and 2.09 g/g, respectively. There were variations in the pasting properties of maize/cassava flour mixes including the pasting temperature (75.4–78.8°C), peak viscosity (112.1–170.0 RVU), breakdown viscosity (38.4–53.7 RVU) and final viscosity (132.1–142.2 RVU), while those of 100% maize flour were 74.6°C, 108.1 RVU, 38.1 RVU and 148.3 RVU, respectively. The colour characteristics of tuwo prepared from maize/cassava flour mixes showed an increase in the colour lightness, L*-value (68.6–71.8) and chroma, C-value (9.4–11.4) while tuwo from 100% maize flour gave 67.7 and 9.1, respectively. The cohesiveness indexes (15.4–24.2%) of tuwo from maize/cassava flour mixes increased with an increase in the quantity of cassava flour in the mix while that from 100% maize flour was 15.2%. The softness indexes (17.5–18.4°mm) of tuwo from the mixes were also higher than that from 100% maize flour (17.4°mm). The sensory quality rating of tuwo from maize/cassava flour mixes showed that tuwo from 25% cassava flour inclusion was the highest in terms of texture (hand-mouldability), taste and overall acceptability while that from 30% cassava flour inclusion was the highest in terms of colour.     

Prebiotic effects of cassava fibre as an ingredient in cracker-like products

Cassava fibre, a waste product formed in starch production, was incorporated into wheat to give composite flours at ratios of 80/20, 70/30, 60/40 and 50/50, respectively. A cracker-like biscuit was produced from the preferred ratios (60/40 and 50/50). The effects of these on diets as a prebiotic were evaluated in a rat assay. Determinations of the proximate composition and haematological parameters were made as well as microbiological analysis. The protein content of the cracker-like product based on the 50/50 and 60/40 (fibre/wheat flour) ratios were 15.0% and 10.0%, respectively. Crude fibre ranged from 14.1-17.1% while ash ranged from 3.0 and 5.0%. Low cholesterol levels of 28.75 mg dL(-1) and 18.75 mg dL(-1) were recorded for the 50/50 and 60/40 composite ratios, respectively. The result of liver function test showed that the rats that were fed the fibre-based cracker product had an average value of 44.00 IU L(-1) of aspartate amino transferase (AST), which is lower than the 67.75 IU L(-1) recorded for the control. There was a significant increase in the packed cell volume (PCV) of the rats fed a fibre-based diet, relative to those fed "Ogi" (fermented maize). Haemoglobin was significantly higher in the control sample than all others, while no significant difference was observed in the white blood cell (WBC) count, with average of 11.75 mm(3). Data obtained from the faecal analysis showed that the rats fed with the composite ratios and other diets had an increased Lactobacillus count. However, by increasing the number of days that the rats were fed the fibre-based diet, the E. coli count in the rat faeces reduced significantly. The data obtained shows that cassava fibre-based crackers have good nutraceutic effects, with reduction in the E. coli count found in the rat faeces and healthy performances in terms of weight gain.     

Web‐Forming System Design Using CFD Modelling for Complex 3D Nonwoven Shell Structures

Summary: CFD modelling has been used to study the unique problem of airflow containing fibres around 3D porous media in nonwoven web forming systems. The related gas‐solid two‐phase flows were simulated using a commercial CFD package, FLUENT. Simulation results revealed that the uniformity of air velocities and fibre concentration around the moulds, particularly for complex‐shaped moulds, could be improved significantly by means of employing vertically oriented web forming system and moulds with controlled porosity. Experimental results indicated that the distribution of the area densities of the 3D nonwovens produced using polypropylene/polyester bi‐component fibre followed the same patterns of the airflow and fibre distributions simulated using the CFD model. The CFD model is a valuable tool for optimising the web forming systems and improving the uniformity of the 3D nonwovens.

Area density distribution of the 3D products produced using the vertical system.     

Observation of current reversal in the scanning tunneling spectra of fullerene-like WS2 nanoparticles

Current-voltage characteristics measured using STM on fullerene-like WS2 nanoparticles show zero-bias current and contain segments in which the tunneling current flows opposite to the applied bias voltage. In addition, negative differential conductance peaks emerge in these reversed current segments, and the characteristics are hysteretic with respect to the change in the voltage sweep direction. Such unusual features resemble those appearing in cyclic voltammograms, but are uniquely observed here in tunneling spectra measured in vacuum, as well as in ambient and dry atmosphere conditions. This behavior is attributed to tunneling-driven electrochemical processes.     

A system approach to the environmental analysis of industrial buildings

The construction sector plays a major role in the development of society. It wields enormous influence over economic activity, employment and growth rates. However, it also has a substantial impact on the natural environment, the effects of which are evident across the world. Over recent decades, pioneering initiatives have proposed environmentally friendly buildings and sustainable construction has centred on residential and office buildings. Nevertheless, further consideration still needs to be given to sustainability in many areas of industrial construction. Accordingly, an Integrated Value Model for Sustainable Assessment (MIVES) is presented in this article that applies a set of six study scopes to define the sustainability criteria of industrial buildings. The system uses a requirements tree to quantify sustainability at various hierarchical levels, in order to assess the behaviour of industrial buildings and compliance with the criteria. Assignment of value functions to the sustainability criteria is then described in the context of a case study of a printing works, which demonstrates the effectiveness of this model at unifying both qualitative and quantitative indicators, in order to arrive at a specific “environmental sustainability index” for the industrial building.     

A study of Weibull parameters using long-term wind observations

The two parameters of a Weibull density distribution function were calculated for three different locations; a city area, an extremely exposed area in a city centre and an open sea area in Hong Kong. A long-term data source, consisting of thirty years (1968–1997) of hourly mean wind data, was adopted and analysed. Based on these data, it was found that the numerical values of the shape and scale parameters for these weather stations varied over a wide range. The shape parameter varied from 1.63 to 2.03 and the scale parameter ranged from 2.76 to 8.92. The yearly Weibull probability density function distribution for the city area indicated that the wind data could be grouped into two distinct periods, 1968–1981 and 1982–1997. Seasonal Weibull distribution for the three locations were compared and wider distributions were observed in the more open areas.     

A gas flow method for determination of in‐plane permeability of fiber preforms

Resin flow plays a crucial role in many composite manufacturing processes. The most important parameters used in modeling and designing mold filling are the permeability of the fibrous preform, which is a kind of flow conductance and a property of the reinforcement, and the viscosity of the resin. The extent reaction, or degree of cure, is also important and causes change of chemical during mold filling. To determine the permeability of fiber preform searchers have been using liquid flow analysis. In this study, a new scheme for determining permeability using gas flow is proposed. In conventional liquid flow methods, radial propagation of the polymer into a porous medium is measured and used to determine permeability, whereas in the gas flow method, the several different preform geometries is measured and used. The effectiveness of the gas flow method was verified by comparing it with conventional methods.