Relative value of selective group A streptococcal agar incubated under different atmospheres

A commercially available selective group A streptococcal agar (ssA) was evaluated for the recovery of group A streptococci (GAS) in comparison with recovery from simultaneous cultures on conventional sheep blood agar (SBA). Both sets of plates were incubated in air, 5% CO2, and anaerobically for 48 h, with a first reading taken at 24 h. A total of 402 (67.0%) GAS were isolated from the 600 specimens that were submitted. Recovery of GAS was significantly greater after 48 h of incubation than after 24 h of incubation for each medium-atmosphere combination. After 48 h of incubation, the sensitivities of GAS detection obtained by each culture technique were as follows: ssA-anaerobic atmosphere, 98.5%; SBA-anaerobic atmosphere, 89.5%; ssA-CO2 atmosphere, 88.0%; SBA-air, 86.5%; SBA-CO2 atmosphere, 82.0%; and ssA-air, 74.6%. There were no cultures positive in air or CO2 which were not positive anaerobically on either medium. The increased sensitivity of detecting positive GAS cultures when incubation was done in an ssA-anaerobic atmosphere for 48 h uncovered patients truly infected with the organisms.     

Experience with the antibiotic resistance analysis and DNA fingerprinting in tracking faecal pollution at two lake beaches.

Posting or closing of swimming beaches because of faecal contamination is a widespread problem reported in many locations. In a risk-based approach to this problem, the risk to swimmers' health is assessed by field monitoring of indicator bacteria and the associated risks are managed by source controls and other remedial measures. In risk assessment, great advances have been made in recent years with the introduction of microbial source tracking (MST) techniques. Two such techniques, antibiotic resistance analysis and DNA fingerprinting, were applied in a study of causes of faecal contamination at two lake beaches in Toronto, Ontario. Both methods identified bird faeces as the dominant sources of E. coli. Coping with this type of pollution presents a major environmental challenge.     

Study of the technological properties of Karelian rocks as raw material for production of mineral wool

A technological study of basic and ultrabasic Karelian rocks as mineral wool raw material was conducted. It was found that ultrabasic rocks with a ratio of CaO: MgO ≥ 0.5 are the optimum raw material for production of mineral wool by the cupola method. Promising sections of these types of rocks for development are identified.     

A strain hardening failure assessment diagram derived from carbon-manganese steel compact tension specimens

A failure assessment diagram is derived from carbon-manganese steel compact tension specimens. The diagram has been determined from an elastic-plastic finite element analysis of a compact tension specimen geometry. The diagram has been validated by using experimental fracture toughness data obtained on the same steel and specimen geometry modelled in the finite element analysis. The plastic collapse load has been determined empirically for this geometry.It is shown that a non-work-hardening failure assessment diagram is not a good representation of the experimental data and that the computed failure assessment diagram is more appropriate for describing the behaviour of the carbon-manganese steel specimens.     

Simplified method for the prediction of water activity in binary aqueous solutions

This work describes the application of a simplified method to predict the water activity ( a _w) of binary aqueous solutions in a range of concentrations relevant to intermediate moisture foods. The water activity as a function of molality for several solutes (electrolytes and non-electrolytes) is described by the equation, a _w, = 1 − K m , where K is a constant and m is the molality. Values of K are reported for fifteen non-electrolytes and eight electrolytes. The accuracy of water activity prediction by this method satisfies the actual needs in food research.