Use of bioanalyzer electropherograms for quality control and target evaluation in microarray expression profiling studies of ocular tissues

Expression profiling with DNA microarrays has been used to examine the transcriptome of a wide spectrum of vertebrate cells and tissues. The sensitivity and accuracy of the data generated is dependent on the quality and composition of the input RNA. In this report, we examine the quality and array performance of over 200 total RNA samples extracted from ocular tissues and cells that have been processed in a microarray core laboratory over a 7-year period. Total RNA integrity and cRNA target size distribution were assessed using the 2100 Bioanalyzer. We present Affymetrix GeneChip array performance metrics for different ocular samples processed according to a standard microarray assay workflow including several quality control checkpoints. Our review of ocular sample performance in the microarray assay demonstrates the value of considering tissue-specific characteristics in evaluating array data. Specifically, we show that Bioanalyzer electropherograms reveal highly abundant mRNAs in lacrimal gland targets that are correlated with variation in array assay performance. Our results provide useful benchmarks for other gene expression studies of ocular systems

An effectiveness-NTU technique for characterising tube-in-tank phase change thermal energy storage systems

Thermal storage systems with phase change materials are predominantly designed, analysed and optimised through numerical modelling. An alternative simplified method is being proposed for the characterisation of these phase change thermal storage systems. The method is based on the effectiveness-number of transfer units (ε-NTUs) technique. A simplified mathematical representation has been analytically developed using the ε-NTU technique for a cylindrical tank filled with phase change material (PCM), with heat transfer fluid flowing through tubes inside the tank. Experiments have been carried out on a cylindrical tank filled with PCM and with one, two and four coils of tubes to validate the technique. Experimental results for the systems with a high heat transfer area compare well with those calculated from the model. The results show that this technique can readily be used as a design tool for sizing and optimising a thermal storage unit with phase change materials. From this study, it may be concluded that the model based on the ε-NTU technique can accurately predict the average heat exchange effectiveness of the thermal storage system with a high heat transfer surface area during charging and discharging.

Investigation of the thermal resistance of timber attic spaces with reflective foil and bulk insulation, heat flow up

An experimental investigation was undertaken in which the thermal resistance for the heat flow through a typical timber framed pitched roofing system was measured under outdoor conditions for heat flow up. The measured thermal resistance of low resistance systems such as an uninsulated attic space and a reflective attic space compared well with published data. However, with higher thermal resistance systems containing bulk insulation within the timber frame, the measured result for a typical installation was as low as 50% of the thermal resistance determined considering two dimensional thermal bridging using the parallel path method. This result was attributed to three dimensional heat flow and insulation installation defects, resulting from the design and construction method used. Translating these results to a typical house with a 200 m2 floor area, the overall thermal resistance of the roof was at least 23% lower than the overall calculated thermal resistance including two dimensional thermal bridging. When a continuous layer of bulk insulation was applied to the roofing system, the measured values were in agreement with calculated resistances representing a more reliable solution.Heat transfer Buildings Thermal resistance Timber roof Bulk insulation Reflective foil