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Language comprises a lexicon for storing words and a grammar for generating rule-governed forms. Evidence is presented that the lexicon is part of a temporal-parietal/medial-temporal 'declarative memory' system and that grammatical rules are processed by a frontal/basal-ganglia 'procedural' system. Patients produced past tenses of regular and novel verbs (looked and plagged), which require an -ed-suffixation rule, and irregular verbs (dug), which are retrieved from memory. Word-finding difficulties in posterior aphasia, and the general declarative memory impairment in Alzheimer's disease, led to more errors with irregular than regular and novel verbs. Grammatical difficulties in anterior aphasia, and the general impairment of procedures in Parkinson's disease, led to the opposite pattern. In contrast to the Parkinson's patients, who showed suppressed motor activity and rule use, Huntington's disease patients showed excess motor activity and rule use, underscoring a role for the basal ganglia in grammatical processing., INTRODUCTION Two capacities give human language its vast expressive power. One is a 'mental lexicon' containing thousands of words, each a memorized, arbitrary sound-meaning pairing. The other is a 'mental [...]

Many investigations of detonation-based combustors have identified reactant mixture inhomogeneity as having a leading-order impact on wave dynamics and combustion efficiency. To examine this phenomenon in a simplified context, an array of two- and three-dimensional channel detonation simulations are conducted in the present work. The reactant mixture consists of stratified fuel and air, wherein the randomly distributed equivalence ratio field features a characteristic stratification length scale. Detailed chemical kinetics are implemented in an adaptive mesh refinement solution framework where the region near the shock front is resolved with O (100) cells per representative ZND induction length. The results show that in comparison to baseline cases with uniform reactant mixtures, reactant stratification has a marked impact on the detonation structure. Increasing the stratification length scale increases the size and irregularity of the detonation cells, yielding larger variations in wave speed. Triple point collisions in fuel-rich regions lead to local wave speeds above the notional mean CJ speed, but wave passage through inert regions causes the local wave speed and strength to diminish. Conditional statistics show that increasing the stratification length scale increases the variance in pressure and temperature in the primary reaction zone, as well as the variance in heat release over a range of mixture conditions. In addition to the reactant mixture, the impact of the boundary condition behind the detonation is also investigated. The results show that an inflow boundary condition acts to over-drive the wave, leading to higher peak pressures, smaller detonation cells, and increased reactant consumption. On the other hand, cases with a wall behind the wave exhibit weaker waves with lower peak pressures and heat release rates, as well as greater variance in conditional quantities. Comparisons between complementary two- and three-dimensional simulations show reasonable qualitative agreement in wave structure, speed, and conditional statistics. Novelty and significance statement: The present work considers two- and three-dimensional simulations of detonations propagating through stratified reactant mixtures using detailed chemical kinetics with O (100) cells per representative ZND induction length. To the authors' knowledge, it is the first study to analyze this type of configuration at this resolution and detail, as well as the first to compare two- and three-dimensional simulations of this configuration. The results have implications for the detonation wave behavior observed in practical propulsion and power-generating applications, such as rotating detonation engines. [ABSTRACT FROM AUTHOR]