Graphing the death of Escherichia coli

The graphical presentation of measurements of the progress over time of bacterial death or inactivation is discussed. Specifically, the Weibull distribution may be a useful generalisation of the exponential distribution. Data from experiments on the non-thermal death of Escherichia coli reported by Shadbolt et al. [Int. J. Food Microbiol. 49 (1999) 129] are reexamined to support this claim.     

Views of hospital staff on the management of hypertension

A questionnaire concerning the detection and management of hypertension was presented to 265 hospital doctors, 114 medical students and 59 student nurses. Of these 75% were completed. Although only 76% thought that routine measurement was necessary in outpatients, 92% of respondents thought that blood pressure (BP) should be measured routinely in all in-patients. A total of 17% of all doctors and 11% of physicians indicated that they would not use drug treatment until the diastolic BP exceeded 105 mmHg. Thirty-four per cent of respondents still use diastolic phase IV and 84% felt that BP should be measured 2-4 times before deciding on treatment but the posture of the patient (lying, sitting or standing) during recording was inconsistent. Seventy-seven per cent of respondents indicated that they recorded BP to the nearest 5 mmHg and 4% to the nearest 10 mmHg. Despite the literature on the subject, there are still widely differing opinions amongst medical staff on how to record BP and at what level it should be treated.     

Crazing and fracture of polystyrene

The effects of the concentration of internal lubricants on the deformation and fracture of commercial polystyrenes produced by bulk and suspension polymerization routes are described. The addition of internal lubricant in the range 0 to 6% was shown to cause a decrease in the extent of craze-yielding and in the incidence of secondary fracture features, and over-all the changes in behaviour were similar to those observed when the test temperature is increased.     

Non-conventional injection molding of poly(lactide) and poly(ε-caprolactone) intended for orthopedic applications

Biodegradable polymers such as poly(lactide) (PLA) and poly(epsilon-caprolactone) (PCL) are increasingly used in biomedical applications as temporary implants. However, melt processing of these materials in particular of PLA is difficult due to the temperature sensitivity. Within this study, PLA and PCL were injection molded conventionally and by using the process shear controled orientation in injection molding (SCORIM) in order to investigate the effect of processing parameters on the physical properties of the moldings. Therefore, flexural testing, differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), molecular weight (MW) and orientation measurements were performed. PLA showed high sensitivity to melt temperature. In the case of amorphous poly(DL-lactide), the molecular weight and subsequently the ductility is substantially reduced by processing at higher melt temperatures. In the case of crystallizable poly(L-lactide), higher melt temperatures and shear induced by the SCORIM process resulted in enhanced crystallinity, which compromised the mechanical properties. Generally, SCORIM processing improved the mechanical properties, in particular the ductility, by orientating the molecular structure. PCL was shown to be less sensitive to shear and temperature than PLA. Stress at yield and stiffness are more improved by SCORIM processing. However, the processing temperature in combination with the grade used proved to be influential for the mechanical properties of resulting moldings.     

The microstructure and deformation of model ABS compounds

Model ABS compounds have been used to investigate the effect of graft frequency and rubber particle size on microstructure and mechanical properties. Graft frequency was found to have a marked effect on the microstructure of ABS polymers and increasing the graft frequency resulted in an improvement in the dispersion of the rubber phase.     

Application of Balanced Detection to Absorption Measurements of Trace Gases with Room-Temperature, Quasi-cw Quantum-Cascade Lasers

Distributed-feedback quantum-cascade (QC) lasers are expected to form the heart of the next-generation mid-IR laser absorption spectrometers, especially as they are applied to measurements of trace gases in a variety of environments. The incorporation of room-temperature-operable, single-mode QC lasers should result in highly compact and rugged sensors for real-world applications. We report preliminary results on the performance of a laser absorption spectrometer that uses a QC laser operating at room temperature in a quasi-cw mode in conjunction with balanced ratiometric detection. We have demonstrated sensitivities for N(2)O [10 parts in 10(6) volume-mixing ratio for a 1-m path (ppmv-m)] and NO [520 parts in 10(9) volume-mixing ratio for a 1-m path (ppbv-m)] at 5.4 mum. System improvements are described that are expected to result in a 2 orders of magnitude increase in sensitivity.     

Cavity ringdown spectroscopic detection of nitric oxide with a continuous-wave quantum-cascade laser

A spectroscopic gas sensor for nitric oxide (NO) detection based on a cavity ringdown technique was designed and evaluated. A cw quantum-cascade distributed-feedback laser operating at 5.2 mum was used as a tunable single-frequency light source. Both laser-frequency tuning and abrupt interruptions of the laser radiation were performed through manipulation of the laser current. A single ringdown event sensitivity to absorption of 2.2 x 10(-8) cm(-1) was achieved. Measurements of parts per billion (ppb) NO concentrations in N(2) with a 0.7-ppb standard error for a data collection time of 8 s have been performed. Future improvements are discussed that would allow quantification of NO in human breath.     

A cost and performance comparison of LRTM and VI for the manufacture of large scale wind turbine blades

Light resin transfer moulding (LRTM) has been developed as an alternative to vacuum infusion (VI) but a direct comparison between the two processes is needed to quantify any advantages. This paper uses a technical cost model and an empirical study to show the potential financial and performance benefits of LRTM for manufacture of a generic 40 m wind turbine blade shell. The use of LRTM when compared to VI demonstrated a possible 3% cost saving, improved dimensional stability (5.5%), and reductions in resin wastage (3%) and infusion time (25%). A decrease in internal void formation (0.9%) resulted in an increase in mechanical performance (<4%) for LRTM moulded parts.     

CIB organizations

G.L. Hutchinson, Reader in Civil Engineering, University of Melbourne and John L. Wilson, formerly State Electricity Commission of Victoria, Melbourne, now of Ove Arup &; Partners, London, examine the design of typical medium‐rise steel‐framed industrial buildings. Such buildings usually possess a non‐uniform distribution of mass and stiffness and consequently respond in more than one mode under earthquake excitation, thus making the application of Article 16 of the Chinese Earthquake Code appropriate