Microstructure-property relationships in silicate-matrix composites

Electron microscopy and associated analytical spectroscopic techniques have been used to characterize interfaces in SiC-fibre/silicate-matrix composites. Interface structure, formed via reaction during hot-press fabrication, is a function of time, temperature, matrix composition and fibre type. Interfaces with Nicalon or Tyranno fibres vary from amorphous carbon in fine precipitated form to continuous graphitic layers. Interface behaviour in a stressed composite, and hence the matrix microcracking stress, is a sensitive function of microstructure. Interface debond and shear properties have been assessed using indent-based ‘push-down’ and ‘push-through’ tests using a specially developed instrument within a scanning electron microscope. This uses piezoload measurement and translation, and is capable of dynamic image recording of the indentation sequence. Interface micromechanical (indent) measurements have been correlated with structure and macromechanical response in bend testing for a range of fibre/matrix types, processing and post-processing thermal treatments. An example is also given of interfaces prepared by fibre precoating.     

A simple and efficient alternative to implementing systematic random sampling in stereological designs without a motorized microscope stage

When properly applied, stereology is a very robust and efficient method to quantify a variety of parameters from biological material. A common sampling strategy in stereology is systematic random sampling, which involves choosing a random sampling relevant objects start point outside the structure of interest, and sampling at sites that are placed at pre‐determined, equidistant intervals. This has proven to be a very efficient sampling strategy, and is used widely in stereological designs. At the microscopic level, this is most often achieved through the use of a motorized stage that facilitates the systematic random stepping across the structure of interest. Here, we report a simple, precise and cost‐effective software‐based alternative to accomplishing systematic random sampling under the microscope. We believe that this approach will facilitate the use of stereological designs that employ systematic random sampling in laboratories that lack the resources to acquire costly, fully automated systems.     

Effect of water hardness on cooking characteristics of cowpea (Vigna unguiculata L. Walp) seeds

Cowpeas were cooked in water made hard (or soft) by the separate addition of similar concentrations of certain salts (CaCl₂, MgCl₂, or NaHCO₃). The beans were also cooked in hard tap water and in double distilled water before and after soaking in water. Hard water caused a significant decrease in softness, led to reduced water absorption, and also decreased solids loss in the cooked product, but it increased the cooking time and discolouration of the beans. Hard water also gave rise to a significant ( P <0.05) increase in mineral content, but it had less effect on the proximate composition of the cooked products.     

SIGNIFICANCE OF STAPHYLOCOAGULASE IN FOOD MICROBIOLOGY: A REVIEW

Staphylocoagulase is an important enzyme for the identification of Staphylococcus aureus. It is also commonly related to pathogenicity of the organism. This review discusses the history of staphylocoagulase, its importance in the identification of staphylococci, its relationship with other important enzymes of staphylococci, and its role in food microbiology and food safety. Chemical properties, synthesis, mechanism of enzymatic activities, factors influencing detection, methods of detection, possible occurrence of the enzyme in foods, and its heat stability are also reviewed.     

Behaviour of power-factor meters under non-sinusoidal current and voltage

Different types of analogue and digital power-factor meters used for low frequencies are studied. Their errors are calculated when the current or voltage waveform is distorted. It is shown that large errors appear under these working conditions. A new measuring instrument is proposed. It has very small errors, even under highly distorted waveforms, having low-pass filters at the inputs to prevent errors generated by high frequency harmonics.     

PROBLEMS WITH CHAOTIC CRYPTOSYSTEMS

Matthews [1] has proposed a function based on chaos theory for generating sequences of random numbers to be used like a one-time pad. When implemented on digital computer systems, these functions must produce repeating cycles of values. The cycle length turns out to be unpredictable and often short. The function is not suitable for cryptographic use in the manner proposed by Matthews.     

CONCENTRATION OF ONION JUICE VOLATILES BY REVERSE OSMOSIS AND ITS EFFECTS ON SUPERCRITICAL CO2 EXTRACTION

Supercritical carbon dioxide extraction of onion oil at moderate temperatures produces aproduct which is characteristic of the fresh flavor of onions. It was attempted to improve extraction efficiency by concentrating the onion juice by reverse osmosis prior to supercritical CO₂ extraction. Reverse osmosis was carried out for all combinations of 600, 700, and 800 psi feed pressure and 25 and 35C. The juice was concentrated to 18 ^oBtix and then subjected to supercritical CO₂ extraction. The effect of concentration on the extraction process was evaluated by comparing the yields of extracts from concentrated juice with that of single strength juice. Concentration of onion juice by reverse osmosis improved the efficiency of supercritical CO₂ extraction of onion oil and did not alter its characteristic fresh aroma.     

Growth of Lactobacillus plantarum in Cucumber Extract Containing Various Chloride Salts

Systems similar to the environment of pure-culture inoculation and the natural process of cucumber fermentation were used to study the capabilities of some salt substitutes including potassium chloride, calcium chloride, and magnesium chloride to provide a selective environment for the growth of Lactobacillus plantarum, a desirable species in cucumber fermentation. The salt that gave the highest percentage of Lactobacillus in the total microbial population was considered to provide the most selective environment for the desirable organisms in cucumber fermentation. Salts that provided the most selective environment were NaCl and KCl in the filtered, raw cucumber extract and KCl in the heated and filtered extract. Calcium chloride was more selective than MgCl₂ in either medium.     

STORAGE QUALITY OF MINIMALLY PROCESSED CABBAGE PACKAGED IN PLASTIC FILMS

The effects of packaging and storage at 3C in a refrigerated case on quality changes of minimally processed cabbage were studied. Shredded cabbage samples were packaged in three forms: bags of monooriented polypropylene film (OPP bags) and polyethylene trays overwrapped with a multilayer polyolefin (RD106-PE tray) or with a plasticized PVC film (PVC-PE tray). All types of package effectively controlled the weight loss. The modified atmosphere in PVC-and RD106- PE trays did not change more than 3% as compared with normal atmosphere levels. However, in OPP bags, O₂ reached 2% and CO₂ increased to approximately 13% after 3 days. The microbiological quality during the storage period for all types of packaging was satisfactory. OPP samples were significantly better (p <0.05) in general appearance, wilting and browning but developed an off-odor. No off-odor was detected in samples packaged in PVC and RD106-PE trays. Shelf life for the three packaging forms was estimated.