Mathematical modeling of mixed convection in a closed rectangular area in conditions of lower boundary radiant heating

Mathematical modeling of mixed convection in a closed rectangular area in conditions of lower boundary radiant heating is passed. Fields of temperatures and stream functions for different Grashof numbers are obtained. The scale influence of Grashof number increasing on the heat transfer intensity is shown. It is founded that the process of closed areas radiant heating has significantly unsteady nature

Организация и ведение аварийно-спасательных работ при наводнении на акваториях

В данной статье представлена необходимость использования эвакуации населения, исторических и материальных средств при возникновении чрезвычайных ситуаций, как одного из основных способов защиты. Основные особенности организации эвакуации, порядок ее осуществления и принципы руководства.This article presents the need to use the evacuation of the population, historical and material assets in the event of emergencies, as one of the main ways of protection. The main features of the evacuation organization, the procedure for its implementation and the principles of leadership

Processing of auditory signals in the forebrain of the Barn Owl : neural mechanisms of across-frequency integration

Interaural time differences (ITDs) of acoustic signals represent a major cue for sound localization in most animals including humans. Due to the finite propagation velocity of sound and the different path lengths to the two ears, ITDs change with the azimuth of a sound source. Binaural comparison of phase locked spikes is performed in neurons of the auditory brainstem. On this first stage of ITD processing, neurons are sensitive to interaural phase differences (IPDs) in narrow spectral components of the signal. However, IPDs relate in an ambiguous manner to the ITD of the signal. In the barn owl’s external nucleus of the inferior colliculus (ICX), a part of the tectofugal pathway, phase ambiguities are resolved by integrating ITD information across frequency channels. This thesis focusses on ITD processing in the parallel thalamofugal pathway. I report substantial differences in ITD processing in the two pathways that may reflect an impact of behavior on sensory representations. Extracellular recordings were obtained from neurons in the auditory arcopallium (AAr), a high level auditory and sensorimotor integration center in the forebrain of the barn owl (Tyto alba). Responses were characterized with focus on ITD and frequency tuning. ITD curves to pure tones revealed the preferred interaural phase differences at specific frequencies. In neurons with a linear phase-frequency relation, across-frequency integration was described by the neuron’s characteristic delay (CD) and its characteristic phase (CP). The CD is the delay at which the neuron’s relative response strength was consistent across frequencies. The CP indicates the relative response strength at which the CD was exhibited. Besides the classical method of assessing CD and CP from ITD tone curves, I developed a new method allowing for CD and CP estimation on the basis of discrete Fourier transforms of ITD noise functions. Data were collected from 290 AAr units and compared to data sets from 76 ICX units. AAr units were responsive to broad ranges of frequencies. A variety of tuning curve shapes was observed including single peaked curves, curves displaying multiple peaks and curves that were flat over a range of frequencies. In comparison to frequency tuning in ICX units, tuning width in AAr was broader and the distribution of peak values included an important portion of frequencies lower than 3 kHz. In response to ITD noise stimuli, most AAr units featured peak responses at contralateral leading ITDs. Peak widths were broader than in ICX units. ITD tuning curves of AAr units displayed a central peak and side peaks. In a majority of AAr units the main peak was asymmetric displaying a steep slope on the side close to zero ITD and enhanced responsiveness on the side of contralateral leading ITDs. ITD tuning curves were significantly more asymmetric in AAr units than in ICX units. On the populational level, this difference was no longer apparent, when tuning curves were recorded using highpass filtered noise. Hence, low frequencies made an important contribution to the asymmetries of ITD curves in AAr units. Asymmetric tuning curves may be explained by the ITD sensitivity displayed at different spectral components. In ICX units, peak ITDs were consistent throughout the frequency range. This is equivalent to saying that neurons exhibited a CD equal to the best ITD and a CP of zero. In contrast, ITD responses in a majority of AAr neurons displayed an intermediate response level at a consistent ITD value across frequencies. CPs had a mean absolute value of 0.17 cycles, i.e. units displayed slope type integration of ITD information across frequency channels. As linear integration of spectral ITD sensitivity was a good model to explain ITD responses to noise, the observed asymmetric shape of ITD noise curves can be seen as a direct consequence of the prevailing slope type integration in AAr units. Analysis of phase-frequency relations in different frequency ranges, revealed that low frequencies contributed sensitivity to large ITDs. Neurons displaying non zero CPs are typical of the mammalian auditory brainstem, but have not been described in the owl before. While phase locked inhibition and cochlear delays cannot be ruled out as reason for non zero CPs in mammalian systems, they are an unlikely explanation in the owl. I propose that neurons in the auditory forebrain of the owl combine ITD information from lower stages in a systematic way across frequency and across ITD channels to yield non zero CPs. Since the tectofugal pathway seems to subserve sound localization, the thalamofugal pathway is likely to be involved in additional tasks such as recognition of auditory objects, decisions on importance and novelty of sounds as well as control of attention. Therefore, the observed differences in ITD processing in the thalamofugal pathway compared to the tectofugal pathway may represent adaptations to behavioral requirements

Processing of auditory signals in the forebrain of the Barn Owl : neural mechanisms of across-frequency integration

Interaural time differences (ITDs) of acoustic signals represent a major cue for sound localization in most animals including humans. Due to the finite propagation velocity of sound and the different path lengths to the two ears, ITDs change with the azimuth of a sound source. Binaural comparison of phase locked spikes is performed in neurons of the auditory brainstem. On this first stage of ITD processing, neurons are sensitive to interaural phase differences (IPDs) in narrow spectral components of the signal. However, IPDs relate in an ambiguous manner to the ITD of the signal. In the barn owl’s external nucleus of the inferior colliculus (ICX), a part of the tectofugal pathway, phase ambiguities are resolved by integrating ITD information across frequency channels. This thesis focusses on ITD processing in the parallel thalamofugal pathway. I report substantial differences in ITD processing in the two pathways that may reflect an impact of behavior on sensory representations. Extracellular recordings were obtained from neurons in the auditory arcopallium (AAr), a high level auditory and sensorimotor integration center in the forebrain of the barn owl (Tyto alba). Responses were characterized with focus on ITD and frequency tuning. ITD curves to pure tones revealed the preferred interaural phase differences at specific frequencies. In neurons with a linear phase-frequency relation, across-frequency integration was described by the neuron’s characteristic delay (CD) and its characteristic phase (CP). The CD is the delay at which the neuron’s relative response strength was consistent across frequencies. The CP indicates the relative response strength at which the CD was exhibited. Besides the classical method of assessing CD and CP from ITD tone curves, I developed a new method allowing for CD and CP estimation on the basis of discrete Fourier transforms of ITD noise functions. Data were collected from 290 AAr units and compared to data sets from 76 ICX units. AAr units were responsive to broad ranges of frequencies. A variety of tuning curve shapes was observed including single peaked curves, curves displaying multiple peaks and curves that were flat over a range of frequencies. In comparison to frequency tuning in ICX units, tuning width in AAr was broader and the distribution of peak values included an important portion of frequencies lower than 3 kHz. In response to ITD noise stimuli, most AAr units featured peak responses at contralateral leading ITDs. Peak widths were broader than in ICX units. ITD tuning curves of AAr units displayed a central peak and side peaks. In a majority of AAr units the main peak was asymmetric displaying a steep slope on the side close to zero ITD and enhanced responsiveness on the side of contralateral leading ITDs. ITD tuning curves were significantly more asymmetric in AAr units than in ICX units. On the populational level, this difference was no longer apparent, when tuning curves were recorded using highpass filtered noise. Hence, low frequencies made an important contribution to the asymmetries of ITD curves in AAr units. Asymmetric tuning curves may be explained by the ITD sensitivity displayed at different spectral components. In ICX units, peak ITDs were consistent throughout the frequency range. This is equivalent to saying that neurons exhibited a CD equal to the best ITD and a CP of zero. In contrast, ITD responses in a majority of AAr neurons displayed an intermediate response level at a consistent ITD value across frequencies. CPs had a mean absolute value of 0.17 cycles, i.e. units displayed slope type integration of ITD information across frequency channels. As linear integration of spectral ITD sensitivity was a good model to explain ITD responses to noise, the observed asymmetric shape of ITD noise curves can be seen as a direct consequence of the prevailing slope type integration in AAr units. Analysis of phase-frequency relations in different frequency ranges, revealed that low frequencies contributed sensitivity to large ITDs. Neurons displaying non zero CPs are typical of the mammalian auditory brainstem, but have not been described in the owl before. While phase locked inhibition and cochlear delays cannot be ruled out as reason for non zero CPs in mammalian systems, they are an unlikely explanation in the owl. I propose that neurons in the auditory forebrain of the owl combine ITD information from lower stages in a systematic way across frequency and across ITD channels to yield non zero CPs. Since the tectofugal pathway seems to subserve sound localization, the thalamofugal pathway is likely to be involved in additional tasks such as recognition of auditory objects, decisions on importance and novelty of sounds as well as control of attention. Therefore, the observed differences in ITD processing in the thalamofugal pathway compared to the tectofugal pathway may represent adaptations to behavioral requirements

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Abstract Weakly electric fi shes have been an important model system in behavioral neuroscience for more than 40 years. These fi shes use a specialized electric organ to produce an electric fi eld that is typically below 1 volt/cm and serves in many behaviors including social communication and prey detection. Electrical behaviors are easy to study because inexpensive and widely available tools enable continuous monitoring of the electric fi eld of individual or groups of interacting fi sh. Weakly electric fi sh have been routinely used in tightly controlled neurophysiological experiments in which the animal is immobilized using neuromuscular blockers (e.g., curare). Although experiments that involve immobilization are generally discouraged because it eliminates movement-based behavioral signs of pain and distress, many observable electrosensory behaviors in fi sh persist when the animal is immobilized. Weakly electric fi sh thus offer a unique opportunity to assess the effects of immobilization on behaviors including those that may refl ect pain and distress. We investigated the effects of both immobilization and restraint on a variety of electrosensory behaviors in four species of weakly electric fi shes and observed minor effects that were not consistent between the species tested or between particular behaviors. In general, we observed small increases and decreases in response magnitude to particular electrosensory stimuli. Stressful events such as asphyxiation and handling, however, resulted in signifi cant changes in the fi shes' electrosensory behaviors. Signs of pain and distress include marked reductions in responses to electrosensory stimuli, inconsistent responses, and reductions in or complete cessation of the autogenous electric fi eld