Ignition of Deflagration and Detonation Ahead of the Flame due to Radiative Preheating of Suspended Micro Particles

We study a flame propagating in the gaseous combustible mixture with suspended inert particles. The gas is assumed to be transparent for the radiation emitted by the combustion products, while particles absorb and re-emit the radiation. Thermal radiation heats the particles, which in turn transfer the heat to the surrounding gaseous mixture by means of heat conduction, so that the gas temperature lags that of the particles. We consider different scenarios depending on the spatial distribution of the particles, their size and the number density. In the case of uniform distribution of the particles the radiation causes a modest increase of the temperature ahead of the flame and the corresponding increase of the flame velocity. The effects of radiation preheating is stronger for a flame with smaller normal velocity. In the case of non-uniform distribution of the particles, such that the particles number density is smaller just ahead of the flame and increases in the distant region ahead of the flame, the preheating caused by the thermal radiation may trigger additional independent source of ignition. This scenario requires the formation of a temperature gradient with the maximum temperature sufficient for ignition in the region of denser particles cloud ahead of the advancing flame. Depending on the steepness of the temperature gradient formed in the unburned mixture, either deflagration or detonation can be initiated via the Zeldovich's gradient mechanism. The ignition and the resulting combustion regimes depend on the temperature profile which is formed in effect of radiation absorption and gas-dynamic expansion. In the case of coal dust flames propagating through a layered dust cloud the effect of radiation heat transfer can result in the propagation of combustion wave with velocity up to 1000m/s and can be a plausible explanation of the origin of dust explosion in coal mines.Comment: 45 pages, 14 figures. Accepted for publication Combustion and Flame 29 June 201

Opposing gradients of ribbon size and AMPA receptor expression underlie sensitivity differences among cochlear-nerve/hair-cell synapses

The auditory system transduces sound-evoked vibrations over a range of input sound pressure levels spanning six orders of magnitude. An important component of the system mediating this impressive dynamic range is established in the cochlear sensory epithelium, where functional subtypes of cochlear nerve fibers differ in threshold sensitivity, and spontaneous discharge rate (SR), by more than a factor of 1000 (Liberman, 1978), even though, regardless of type, each fiber contacts only a single hair cell via a single ribbon synapse. To study the mechanisms underlying this remarkable heterogeneity in threshold sensitivity among the 5–30 primary sensory fibers innervating a single inner hair cell, we quantified the sizes of presynaptic ribbons and postsynaptic AMPA receptor patches in >1200 synapses, using high-power confocal imaging of mouse cochleas immunostained for CtBP2 (C-terminal binding protein 2, a major ribbon protein) and GluR2/3 (glutamate receptors 2 and 3). We document complementary gradients, most striking in mid-cochlear regions, whereby synapses from the modiolar face and/or basal pole of the inner hair cell have larger ribbons and smaller receptor patches than synapses located in opposite regions of the cell. The AMPA receptor expression gradient likely contributes to the differences in cochlear nerve threshold and SR seen on the two sides of the hair cell in vivo (Liberman, 1982a); the differences in ribbon size may contribute to the heterogeneity of EPSC waveforms seen in vitro (Grant et al., 2010).National Institute on Deafness and Other Communication Disorders (U.S.) (Grants RO1 DC0188)National Institute on Deafness and Other Communication Disorders (U.S.) (P30 DC5029

Syntax-induced pattern deafness

Perceptual systems often force systematically biased interpretations upon sensory input. These interpretations are obligatory, inaccessible to conscious control, and prevent observers from perceiving alternative percepts. Here we report a similarly impenetrable phenomenon in the domain of language, where the syntactic system prevents listeners from detecting a simple perceptual pattern. Healthy human adults listened to three-word sequences conforming to patterns readily learned even by honeybees, rats, and sleeping human neonates. Specifically, sequences either started or ended with two words from the same syntactic category (e.g., noun–noun–verb or verb–verb–noun). Although participants readily processed the categories and learned repetition patterns over nonsyntactic categories (e.g., animal–animal–clothes), they failed to learn the repetition pattern over syntactic categories, even when explicitly instructed to look for it. Further experiments revealed that participants successfully learned the repetition patterns only when they were consistent with syntactically possible structures, irrespective of whether these structures were attested in English or in other languages unknown to the participants. When the repetition patterns did not match such syntactically possible structures, participants failed to learn them. Our results suggest that when human adults hear a string of nouns and verbs, their syntactic system obligatorily attempts an interpretation (e.g., in terms of subjects, objects, and predicates). As a result, subjects fail to perceive the simpler pattern of repetitions—a form of syntax-induced pattern deafness that is reminiscent of how other perceptual systems force specific interpretations upon sensory input

On The Discriminative Control Of Concurrent Responses: The Relations Among Response Frequency, Latency, And Topography In Auditory Generalization 1

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96671/1/jeab.1962.5-487.pd