High resolution simulations of the long-term evolution of jets from young stellar objects using parallel algorithms

Outflows and jets are an integral part of the formation of young stars and are found to be commonplace in all regions where star formation is known to occur. There has been much work done in the development of computational fluid dynamic methods for the simulation of these outflows in an attempt to gam a greater insight into the processes taking place in their formation. Observational data presents key characteristics of such outflows that can be used to determine the validity of any computational model. Here, we have developed a sophisticated parallehsation method for the splittingup of a jet simulation across a Beowulf type computer cluster using a message-passing method. The parallelised code allows us to run simulations for much longer and on larger domains than was possible with the original serial code. This allows us to investigate the development of some important characteristics of the computational model over large time-scales with a suitably high resolution. In particular we investigate the behaviour of the mass-velocity and mtensity-velocity relationships for molecular outflows driven by a prompt-entramment type jet model. Up to now simulations have indicated good agreement between these characteristics for this model and the observed behaviour of these relationships. However, the short time-scales used did not allow for an evolutionary study of the relationships and as a result long-term simulations are deemed necessary

Conditions for duality between fluxes and concentrations in biochemical networks

Mathematical and computational modelling of biochemical networks is often done in terms of either the concentrations of molecular species or the fluxes of biochemical reactions. When is mathematical modelling from either perspective equivalent to the other? Mathematical duality translates concepts, theorems or mathematical structures into other concepts, theorems or structures, in a one-to-one manner. We present a novel stoichiometric condition that is necessary and sufficient for duality between unidirectional fluxes and concentrations. Our numerical experiments, with computational models derived from a range of genome-scale biochemical networks, suggest that this flux-concentration duality is a pervasive property of biochemical networks. We also provide a combinatorial characterisation that is sufficient to ensure flux-concentration duality. That is, for every two disjoint sets of molecular species, there is at least one reaction complex that involves species from only one of the two sets. When unidirectional fluxes and molecular species concentrations are dual vectors, this implies that the behaviour of the corresponding biochemical network can be described entirely in terms of either concentrations or unidirectional fluxes

Impact of Time-interleaved Analog-to-Digital Converter Mismatch on Digital Receivers

This paper presents the impact that gain, offset and timing mismatch in time-interleaved analog-to-digital converter (TIADC) have on digital receiver systems. An analysis of the mismatch errors shows the dependency of the different errors from the spectrum of the input signal. A discrete-time TIADC model is derived allowing to simulate the mismatch effects of the individual ADCs. Finally, simulations results present the performance degradation that can be expected by the usage of non-ideal analog-to-digital converters (ADC) sampling alternately the inphase and quadrature signals in a direct conversion receiver architecture when random data is processed

Methodology for Mismatch Reduction in Time-Interleaved ADCs

This paper presents a methodology to minimize mismatch errors in time-interleaved analog-to-digital converters (ADC) by means of averaging multiple channels. A simple algorithm improving both spurious free dynamic range (SFDR) and signal-to-noise and distortion ratio (SINAD) is demonstrated. The presented technique provides robustness against inaccurately identified mismatch errors and does not require computationally expensive post-processing of the signal

Acrylamide formation in potato products

End of Project ReportAcrylamide, a substance classified as a potential carcinogen, occurs in heated starchy foods at concentrations many times in excess of levels permitted in drinking water. Early surveys indicated that levels of acrylamide in potato products such as French fries and potato crisps were the highest of the foodstuffs investigated. The present project addressed this issue by determining levels of acrylamide precursors (asparagine and reducing sugars) in raw potatoes and levels of acrylamide in (i) potato products from different storage regimes, (ii) spot-sampled potatoes purchased from a local supermarket, (iii) samples that received pre-treatments and were fried at different temperatures and (iv) French fries reheated in different ovens.A risk assessment of the estimated acrylamide intake from potato products for various cohorts of the Irish population was also conducted