Energy recovery in municipal swimming pools

After a discussion of heat losses and energy costs in municipal heated swimming pools, an analysis in presented of the performance of all of such pools in Northern Ireland. It is demonstrated that performance is generally well below that expected by the designers and reasons are identified as to why this should be so. The causes for poor performance are found to arise variously through poor design, inappropriate equipment selection and installation and bad control and operating practice. Part of the value of this study lies in the fact that as all pools in the region were included, with no pre-selection, the findings can be expected to be fairly representative of such installations throughout the United Kingdom.     

Pressure-enthalpy charts for mixtures of oil and refrigerant R 12

Pressure-enthalpy charts are presented for refrigerant R 12-oil mixtures, for a range of oil concentrations. The effect that the existence of this mixture has on evaporator performance and COP of a refrigeration/heat pump system is discussed and some results are compared with the pure refrigerant cycle normally considered.     

Problems associated with mechanical refrigeration based heat recovery systems in municipal swimming pools

The design of refrigeration-based heat recovery systems for municipal swimming pools is discussed and the performance of all such pools in Northern Ireland is analysed. It is found that most systems are incorrectly designed and specified, that the operating conditions are usually sub-optimal and that the control systems are normally either inappropriate or non-existent. It is clear that heat-pump based swimming pool heat recovery systems are not understood by either the designers, the equipment suppliers, the installers or the operators.     

Electron imaging with Medipix2 hybrid pixel detector

The electron imaging performance of Medipix2 is described. Medipix2 is a hybrid pixel detector composed of two layers. It has a sensor layer and a layer of readout electronics, in which each 55 microm x 55 microm pixel has upper and lower energy discrimination and MHz rate counting. The sensor layer consists of a 300 microm slab of pixellated monolithic silicon and this is bonded to the readout chip. Experimental measurement of the detective quantum efficiency, DQE(0) at 120 keV shows that it can reach approximately 85% independent of electron exposure, since the detector has zero noise, and the DQE(Nyquist) can reach approximately 35% of that expected for a perfect detector (4/pi(2)). Experimental measurement of the modulation transfer function (MTF) at Nyquist resolution for 120 keV electrons using a 60 keV lower energy threshold, yields a value that is 50% of that expected for a perfect detector (2/pi). Finally, Monte Carlo simulations of electron tracks and energy deposited in adjacent pixels have been performed and used to calculate expected values for the MTF and DQE as a function of the threshold energy. The good agreement between theory and experiment allows suggestions for further improvements to be made with confidence. The present detector is already very useful for experiments that require a high DQE at very low doses.     

Peptoid Efficacy against Polymicrobial Biofilms Determined by Using Propidium Monoazide‐Modified Quantitative PCR

Biofilms containing Candida albicans are responsible for a wide variety of clinical infections. The protective effects of the biofilm matrix, the low metabolic activity of microorganisms within a biofilm and their high mutation rate, significantly enhance the resistance of biofilms to conventional antimicrobial treatments. Peptoids are peptide‐mimics that share many features of host defence antimicrobial peptides but have increased resistance to proteases and therefore have better stability in vivo. The activity of a library of peptoids was tested against monospecies and polymicrobial bacterial/fungal biofilms. Selected peptoids showed significant bactericidal and fungicidal activity against the polymicrobial biofilms. This coupled with low cytotoxicity suggests that peptoids could offer a new option for the treatment of clinically relevant polymicrobial infections.     

Sustainable energy development and greenhouse gas emissions in an island power system

The objective of this paper was to investigate the options for the sustainable development of the Northern Ireland energy supply system, reducing greenhouse gas emissions. Particular factors which must be considered centre around the isolation of the system, the prospect of a new gaspipeline and electrical interconnector to the rest of the U.K., and the re‐establishment of an electrical interconnector to the Republic of Ireland. The study has relevance for all similar isolated or island systems, which have particular problems because they tend to be relatively small in size, and their isolation means that inter‐connection with their neighbours is either weak or non‐existent. Because of this, they have to carry greater spare capacity than would normally be the case, with consequent efficiency and cost penalties. Copyright © 2000 John Wiley & Sons, Ltd.     

Secondary electron detection in the scanning transmission electron microscope

In a dedicated scanning transmission electron microscope (STEM) secondary electron images with high spatial resolution and good contrast can be obtained. Two types of detector are described. These take into account the secondary electrons which depend on the post-specimen field strength of the objective lens. Due to the thinness of the samples and the collection geometry the images differ from those obtained in a convectional scanning microscope. Examples are given where secondary electron images augment the information obtained by the more commonly used imaging modes.