Experiences of expressing and storing colostrum antenatally: A qualitative study of mothers in regional Western Australia

This qualitative study explored the experiences and breastfeeding outcomes of a group of mothers who expressed colostrum in the antenatal period. In-depth interviews were conducted over the telephone with 12 women who had attended a unique antenatal lactation clinic appointment at 37 weeks’ gestation. Seven main response themes were identified. Most women reflected positively upon their attendance and reported that the experience of expressing colostrum allowed them to become familiar with their breasts and gave them a sense of security by having a supply of colostrum stored for possible use after birth. The main negative emotions reported were a sense of embarrassment at expressing the colostrum, particularly in front of another person, the difficulties with expressing colostrum and in one instance, the physical pain associated with the process. Antenatal expression of colostrum may improve maternal breastfeeding confidence. Further research using long-term records will determine whether this practice improves breastfeeding outcomes

High-speed diode-laser-absorption measurements of gas dynamics for diesel engines

A diode laser based sensor system, utilizing absorption spectroscopy, has been developed and applied to perform simultaneous measurements of gas temperature, gas pressure, and H2O concentration with 5 kHz measurement bandwidth. A 1387.2 nm tunable distributed feedback diode laser was used to scan across multiple H2O absorption transitions and the direct absorption signal was recorded with the help of a high-speed data acquisition system. H2O was chosen because the target molecule as it is a major product of combustion and absorbs strongly in the 1 – 1.5 &mgr;m region, enabling the use of low-cost telecommunications band diode lasers and optics. Compact optical connectors were designed to conduct measurements in the intake manifold, the EGR cooler exit, and the turbocharger inlet of a 6-cylinder Cummins 6.7L diesel engine featuring a unique cam-less variable valve actuation (VVA) system. These custom optical connectors survived gas temperatures as high as 800 K without the need for any active water or oil cooling. A spectral fitting code employing a Levenberg-Marquardt based least square fitting routine was developed to calculate the gas properties from the recorded absorption data. Diode laser measurements performed during steady state engine operation were within 5% of the thermocouple and pressure sensor measurements, and within 10% of the H2O concentration values derived from the CO2 gas analyzer measurements. Measurements were also performed in the engine during transient events such as step changes in the EGR and exhaust valve openings. In one such transient event, where the EGR valve was rapidly closed to decrease the EGR fraction from 40% to 0%, the diode laser sensor measurements in the intake manifold were able to accurately capture the 300 millisecond change; the thermocouple, on the other hand, required 60 seconds to accurately reflect the change in gas conditions, while the gas analyzer required nearly 2 seconds. This highlights the superior transient response of the diode laser sensor over thermocouples and the gas analyzer

Strategies for high efficiency and stability in biogas-fuelled small engines

This work assesses the performance of small biogas-fuelled engines and explores high-efficiency strategies for power generation in the very low power range of less than 1000 W. Experiments were performed on a small 95-cc, single-cylinder, four-stroke spark-ignition engine operating on biogas. The engine was operated in two modes, i.e., `premixed' and `fuel injection' modes, using both single and dual spark plug configurations. Measurements of in-cylinder pressure, crank angle, brake power, air and fuel flow rates, and exhaust emissions were conducted. Cycle-to-cycle variations in engine in-cylinder pressure and power were also studied and assessed quantitatively for various loading conditions. Results suggest that biogas combustion can be fairly sensitive to the ignition strategies thereby affecting the power output and efficiency. Further, results indicate that continuous fuel injection shows superior performance compared to the premixed case especially at low loads owing to possible charge stratification in the engine cylinder. Overall, this study has demonstrated for the first time that a combination of technologies such as lean burn, fuel injection, and dual spark plug ignition can provide highly efficient and stable operation in a biogas-fuelled small S.I. engine, especially in the low power range of 450-1000W. (C) 2014 Elsevier Inc. All rights reserved