Ionization Phenomena in a Gas-Particle Plasma

Particles in a plasma can appreciably change the electron density from the value it would assume if the particles were not present. The case of pure particle ionization, in which there is only thermionic emission from the particles and no gas ionization, is first considered. It is established that the potential and the charge distributions can be divided into a strong shielding regime, in which most of the free electrons are packed close to the particle surfaces in regions of high potential, and its direct opposite, a weak shielding regime. In both regimes, the free-electron content of the plasma is most readily altered by variations in the particle size, rather than in the work function or particle temperature. The suppression of one form of ionization by the other when both particle and gas contribution to the electron density are comparable is next investigated. In the case of gaseous ionization enhancement it is shown that, if the thermionically emitting particles are hotter than the gas, the electron temperature will also be higher than that of the gas and the gaseous ionization thereby enhanced. Lastly, it is shown that in some transient situations, the particles are able to control the time rate of change of the electron density

Numerical and experimental evaluation of preheated premixed flames at lean and rich conditions

Preheating a combustible mixture enhances the laminar burning flux characteristic mad with high reaction firing rates. As a result, the flammable zone as defined by inlet conditions of equivalence ratio and temperature is expanded beyond that available at standard ambient conditions; however, fundamental questions in these combustion regimes have not been addressed. In this thesis, preheated lean and rich combustion of methane/air mixtures is studied numerically and experimentally to catalog and confirm expected trends in these regimes. Numerical simulations were completed using both GRI-Mech 3.0 and San Diego mechanisms in the combustion code Cantera. An adiabatic simulation data set is obtained over a vast range of equivalence ratios (φ = 0.15-3.5) and inlet temperatures Tin = 200-1000 K), while further study is completed at lean (φ \u3c 0.89) and rich conditions (φ \u3e 1.3). Detailed analyses of flame structure and reaction pathway analysis, sensitivity, and heat release are completed at a total of ten reference cases, five lean and five rich, selected along contours of constant equivalence ratio φ = 0.7, 1.6 and mass flux mad = 0.2190 kg/m2-s. A regression analysis of each regime links adiabatic flame propagation to a characteristic temperature T★, shown to be primarily a function of m, while φ and Tin are shown to play a subordinate role. Analyses together reveal causal kinetic phenomena contributing to differences in lean and rich combustion. Experiments connect the adiabatic findings to the simplest non-adiabatic application, where stand-off distances of a flat flame burner are used as a metric for flame behavior. Viable flames are established at ultra-lean and rich conditions, but results show mechanism uncertainty at preheated conditions in addition to unmodeled heat transfer phenomena. Further study of flat flame behavior is performed in the computational fluid dynamics code Fluent 12.0, where a two dimensional axisymmetric flame is stabilized for three mass fluxes at a reference case of φ = 0.7, Tin = 300 K. The model does not attempt to replicate the exact conditions seen experimentally, rather it seeks to evaluate boundary effects and other two dimensional flame structures resulting from exceeding the laminar burning flux

Tryptophan supplementation and serotonin function: genetic variations in behavioural effects

The neurotransmitter serotonin has a role in affective disorders such as depression and anxiety, as well as sleep, cognitive function and appetite. This review examines the evidence that serotonin-related genotypes may moderate the behavioural effects of supplementation with the serotonin precursor amino acidl-tryptophan (TRP), on which synthesis of serotonin (or 5-hydroxytryptamine; 5-HT) depends. However, 95 % of serotonin is synthesised and used in the periphery, and TRP is also metabolised via non-5-HT routes such as the kynurenine pathway. Moreover, understanding of genotypes involved in regulation of serotonin raises questions over the generalisability of TRP effects on behaviour across individuals with varied serotonergic genotypes. To date, only differences between variants of the 5-HT transporter-linked promoter region (5-HTTLPR) have been investigated in relation to behavioural effects of TRP supplementation. Effects of 5-HTTLPR genotypes are usually compared between the alleles that are either high (L/L′) or low (S/S′) expressing of mRNA for the 5-HT transporter receptor. Yet, another key genetic variable is sex: in women, the S/S′ genotype predicts sensitivity to improved mood and reduced cortisol by TRP supplementation, during stressful challenges, whereas the L/L′ genotype protects against stress-induced mood deterioration. In men, the L/L′ genotype may confer risk of stress-induced increases in negative affect; there are insufficient data to assess effects on male S/S′ genotypes. However, better-powered studies to detect sex by genotype by stress by TRP interactions, as well as consideration of more genotypes, are needed before strong conclusions and recommendations for behavioural effects of TRP treatment can be reached.</jats:p

Measuring Linguistic Complexity Independent of Plausibility

in a sentence, including the lexical frequency of the word, the syntactic context, the discourse context, the intonation of the sentence, and the plausibility of the situation described by the sentence thus far (see Gibson &amp; Pearlmutter 1998 and Tanenhaus &amp; Trueswell 1995 for summaries of relevant factors and evidence). In order to investigat