Hydrogen-diesel fuel co-combustion strategies in light duty and heavy duty CI engines

The co-combustion of diesel fuel with H₂ presents a promising route to reduce the adverse effects of diesel engine exhaust pollutants on the environment and human health. This paper presents the results of H₂-diesel co-combustion experiments carried out on two different research facilities, a light duty and a heavy duty diesel engine. For both engines, H₂ was supplied to the engine intake manifold and aspirated with the intake air. H₂ concentrations of up to 20% vol/vol and 8% vol/vol were tested in the light duty and heavy duty engines respectively. Exhaust gas circulation (EGR) was also utilised for some of the tests to control exhaust NO_x emissions.The results showed NO_x emissions increase with increasing H₂ in the case of the light duty engine, however, in contrast, for the heavy duty engine NO_x emissions were stable/reduced slightly with H₂, attributable to lower in-cylinder gas temperatures during diffusion-controlled combustion. CO and particulate emissions were observed to reduce as the intake H₂ was increased. For the light duty, H₂ was observed to auto-ignite intermittently before diesel fuel injection had started, when the intake H₂ concentration was 20% vol/vol. A similar effect was observed in the heavy duty engine at just over 8% H₂ concentration.     

A DNA microarray for fission yeast: minimal changes in global gene expression after temperature shift

Completion of the fission yeast genome sequence has opened up possibilities for post-genomic approaches. We have constructed a DNA microarray for genome-wide gene expression analysis in fission yeast. The microarray contains DNA fragments, PCR-amplified from a genomic DNA template, that represent > 99% of the 5000 or so annotated fission yeast genes, as well as a number of control sequences. The GenomePRIDE software used attempts to design similarly sized DNA fragments corresponding to gene regions within single exons, near the 3'-end of genes that lack homology to other fission yeast genes. To validate the design and utility of the array, we studied expression changes after a 2 h temperature shift from 25 degrees C to 36 degrees C, conditions widely used when studying temperature-sensitive mutants. Obligingly, the vast majority of genes do not change more than two-fold, supporting the widely held view that temperature-shift experiments specifically reveal phenotypes associated with temperature-sensitive mutants. However, we did identify a small group of genes that showed a reproducible change in expression. Importantly, most of these corresponded to previously characterized heat-shock genes, whose expression has been reported to change after more extreme temperature shifts than those used here. We conclude that the DNA microarray represents a useful resource for fission yeast researchers as well as the broader yeast community, since it will facilitate comparison with the distantly related budding yeast, Saccharomyces cerevisiae. To maximize the utility of this resource, the array and its component parts are fully described in On-line Supplementary Information and are also available commercially.     

Integrated Metabolomics and Proteomics Analyses in the Local Milieu of Islet Allografts in Rejection versus Tolerance

An understanding of the immune mechanisms that lead to rejection versus tolerance of allogeneic pancreatic islet grafts is of paramount importance, as it facilitates the development of innovative methods to improve the transplant outcome. Here, we used our established intraocular islet transplant model to gain novel insight into changes in the local metabolome and proteome within the islet allograft’s immediate microenvironment in association with immune-mediated rejection or tolerance. We performed integrated metabolomics and proteomics analyses in aqueous humor samples representative of the graft’s microenvironment under each transplant outcome. The results showed that several free amino acids, small primary amines, and soluble proteins related to the Warburg effect were upregulated or downregulated in association with either outcome. In general, the observed shifts in the local metabolite and protein profiles in association with rejection were consistent with established pro-inflammatory metabolic pathways and those observed in association with tolerance were immune regulatory. Taken together, the current findings further support the potential of metabolic reprogramming of immune cells towards immune regulation through targeted pharmacological and dietary interventions against specific metabolic pathways that promote the Warburg effect to prevent the rejection of transplanted islets and promote their immune tolerance.     

Long-term lake water quality predictors

Daily water temperature and dissolved oxygen profiles in 3002 Minnesota lakes have been simulated by deterministic process-based water quality models with daily meteorological conditions from 1955 to 1979 as input. From the simulated results, indicators of lake water quality and fish habitat characteristics have been extracted and correlated selectively with normal air temperature, lake mean depth, wind-related densimetric Froude number and Lake number. A seasonal maximum Lake number was found to be a good predictor for volume averaged water temperatures, maximum water temperatures near lake bottom, seasonal stratification characteristics, volume averaged dissolved oxygen concentrations, anoxia characteristics and fish good-growth habitat. Lakes with a maximum daily Lake number bigger than 1.0, are seasonally stratified, have low hypolimnetic dissolved oxygen concentration, and only a fraction of lake depth available for good-growth of fish. Lakes with maximum daily Lake number less than 1.0 are polymictic, with high dissolved oxygen concentration, and with maximum depth available for good fish growth. Empirical formulas for lake water quality and stratification indicators derived from the simulation results give good predictions of temperature and dissolved oxygen characteristics estimated from measurements in seven Minnesota lakes.     

Diffusional Mass Transfer at Sediment-Water Interface

Utilizing a miniature, Clark-type, dissolved oxygen (DO) microprobe and a laser-Doppler velocimeter (LDV), laboratory experiments were conducted to elucidate the effect of the turbulent flow field on the diffusive sublayer thickness, mass transfer coefficient, and DO flux over a smooth bed. Both an artificial and a natural sediment were tested under flow conditions ranging in Reynolds number from 0 to 7,000, for a total of 17 experiments. The vertical resolution achieved with the microprobe enabled measurement of DO concentrations within the diffusive boundary layer and provided a direct measurement of the concentration sublayer thickness. Velocity profile measurements obtained with the LDV were used to estimate the depth-averaged velocity and the shear stress velocity. Analysis of the data included formulation of dimensionless groups and the obtaining of empirical relationships that can facilitate the prediction of the diffusive sublayer thickness, mass transfer coefficient, and mass flux at the sediment-water interface. Although the experimental work focuses on DO transport, the approach undertaken represents a generalized theory of waterside-controlled mass transfer at the sediment-water interface in the presence of a moving fluid.     

Effect of hydrogen-diesel fuel co-combustion on exhaust emissions with verification using an in–cylinder gas sampling technique

The paper presents an experimental investigation of hydrogen-diesel fuel co-combustion carried out on a naturally aspirated, direct injection diesel engine. The engine was supplied with a range of hydrogen-diesel fuel mixture proportions to study the effect of hydrogen addition (aspirated with the intake air) on combustion and exhaust emissions. The tests were performed at fixed diesel injection periods, with hydrogen added to vary the engine load between 0 and 6 bar IMEP. In addition, a novel in–cylinder gas sampling technique was employed to measure species concentrations in the engine cylinder at two in–cylinder locations and at various instants during the combustion process.