Low-dimensional dynamics embedded in a plane Poiseuille flow turbulence : Traveling-wave solution is a saddle point ?

The instability of a streak and its nonlinear evolution are investigated by direct numerical simulation (DNS) for plane Poiseuille flow at Re=3000. It is suggested that there exists a traveling-wave solution (TWS). The TWS is localized around one of the two walls and notably resemble to the coherent structures observed in experiments and DNS so far. The phase space structure around this TWS is similar to a saddle point. Since the stable manifold of this TWS is extended close to the quasi two dimensional (Q2D) energy axis, the approaching process toward the TWS along the stable manifold is approximately described as the instability of the streak (Q2D flow) and the succeeding nonlinear evolution. Bursting corresponds to the escape from the TWS along the unstable manifold. These manifolds constitute part of basin boundary of the turbulent state.Comment: 5 pages, 6 figure

Statistics of velocity gradients in wall-bounded shear flow turbulence

The statistical properties of velocity gradients in a wall-bounded turbulent channel flow are discussed on the basis of three-dimensional direct numerical simulations. Our analysis is concentrated on the trend of the statistical properties of the local enstrophy ${\bm \omega}^2({\bm x},t)$ and the energy dissipation rate $\epsilon({\bm x},t)$ with increasing distance from the wall. We detect a sensitive dependence of the largest amplitudes of both fields (which correspond with the tail of the distribution) on the spectral resolution. The probability density functions of each single field as well as their joint distribution vary significantly with increasing distance from the wall. The largest fluctuations of the velocity gradients are found in the logarithmic layer. This is in agreement with recent experiments which observe a bursting of hairpin vortex packets into the logarithmic region.Comment: 13 pages, 5 figure

Amplification of asynchronous inhibition-mediated synchronization by feedback in recurrent networks

Synchronization of 30-80 Hz oscillatory activity of the principle neurons in the olfactory bulb (mitral cells) is believed to be important for odor discrimination. Previous theoretical studies of these fast rhythms in other brain areas have proposed that principle neuron synchrony can be mediated by short-latency, rapidly decaying inhibition. This phasic inhibition provides a narrow time window for the principle neurons to fire, thus promoting synchrony. However, in the olfactory bulb, the inhibitory granule cells produce long lasting, small amplitude, asynchronous and aperiodic inhibitory input and thus the narrow time window that is required to synchronize spiking does not exist. Instead, it has been suggested that correlated output of the granule cells could serve to synchronize uncoupled mitral cells through a mechanism called "stochastic synchronization", wherein the synchronization arises through correlation of inputs to two neural oscillators. Almost all work on synchrony due to correlations presumes that the correlation is imposed and fixed. Building on theory and experiments that we and others have developed, we show that increased synchrony in the mitral cells could produce an increase in granule cell activity for those granule cells that share a synchronous group of mitral cells. Common granule cell input increases the input correlation to the mitral cells and hence their synchrony by providing a positive feedback loop in correlation. Thus we demonstrate the emergence and temporal evolution of input correlation in recurrent networks with feedback. We explore several theoretical models of this idea, ranging from spiking models to an analytically tractable model. © 2010 Marella, Ermentrout

Notch1 activity in the olfactory bulb is odour-dependent and contributes to olfactory behaviour

Notch signalling plays an important role in synaptic plasticity, learning and memory functions in both Drosophila and rodents. In this paper, we report that this feature is not restricted to hippocampal networks but also involves the olfactory bulb (OB). Odour discrimination and olfactory learning in rodents are essential for survival. Notch1 expression is enriched in mitral cells of the mouse OB. These principal neurons are responsive to specific input odorants and relay the signal to the olfactory cortex. Olfactory stimulation activates a subset of mitral cells, which show an increase in Notch activity. In Notch1cKOKln mice, the loss of Notch1 in mitral cells affects the magnitude of the neuronal response to olfactory stimuli. In addition, Notch1cKOKln mice display reduced olfactory aversion to propionic acid as compared to wildtype controls. This indicates, for the first time, that Notch1 is involved in olfactory processing and may contribute to olfactory behaviour

What the meta-illocutionary lexicon can tell us about speech act taxonomies

Being firmly situated within speech act theory and language philosophy, research on speech act taxonomies (Searle, 1975) takes a second-order approach to distinguishing superordinate function types of utterances, thus largely ignoring first-order perspectives. First-order pragmatics, on the other hand, is dominated by studies on ordinary language users’ conceptualizations of speech acts in isolation (Schneider, 2022; [Author, 2022]). The present study seeks to extend the scope of first-order pragmatics by exploring ordinary usage patterns of the meta-illocutionary lexicon regarding three directive illocutions (requesting, commanding, begging) and three expressive illocutions (thanking, apologizing, congratulating). While these usage patterns directly reflect first-order conceptualizations of (the felicity of) the respective illocutions, they are further argued to collectively constitute indirect evidence for first-order conceptualizations of the relevant speech act classes. Based on blogging data from the GloWbE corpus, results include that while references to directive illocutions tend to favor the descriptive use type of the meta-illocutionary lexicon, references to expressive illocutions are generally dominated by the performative use type. These and other findings are discussed against the background of speech act taxonomies, conventionalization, and the situatedness of speech acts in discourse, among other things

Simple, Fast and Accurate Implementation of the Diffusion Approximation Algorithm for Stochastic Ion Channels with Multiple States

The phenomena that emerge from the interaction of the stochastic opening and closing of ion channels (channel noise) with the non-linear neural dynamics are essential to our understanding of the operation of the nervous system. The effects that channel noise can have on neural dynamics are generally studied using numerical simulations of stochastic models. Algorithms based on discrete Markov Chains (MC) seem to be the most reliable and trustworthy, but even optimized algorithms come with a non-negligible computational cost. Diffusion Approximation (DA) methods use Stochastic Differential Equations (SDE) to approximate the behavior of a number of MCs, considerably speeding up simulation times. However, model comparisons have suggested that DA methods did not lead to the same results as in MC modeling in terms of channel noise statistics and effects on excitability. Recently, it was shown that the difference arose because MCs were modeled with coupled activation subunits, while the DA was modeled using uncoupled activation subunits. Implementations of DA with coupled subunits, in the context of a specific kinetic scheme, yielded similar results to MC. However, it remained unclear how to generalize these implementations to different kinetic schemes, or whether they were faster than MC algorithms. Additionally, a steady state approximation was used for the stochastic terms, which, as we show here, can introduce significant inaccuracies. We derived the SDE explicitly for any given ion channel kinetic scheme. The resulting generic equations were surprisingly simple and interpretable - allowing an easy and efficient DA implementation. The algorithm was tested in a voltage clamp simulation and in two different current clamp simulations, yielding the same results as MC modeling. Also, the simulation efficiency of this DA method demonstrated considerable superiority over MC methods.Comment: 32 text pages, 10 figures, 1 supplementary text + figur

Dendrodendritic synapses in the mouse olfactory bulb external plexiform layer

Odor information relayed by olfactory bulb projection neurons, mitral and tufted cells (M/T), is modulated by pairs of reciprocal dendrodendritic synaptic circuits in the external plexiform layer (EPL). Interneurons, which are accounted for largely by granule cells, receive depolarizing input from M/T dendrites and in turn inhibit current spread in M/T dendrites via hyperpolarizing reciprocal dendrodendritic synapses. Because the location of dendrodendritic synapses may significantly affect the cascade of odor information, we assessed synaptic properties and density within sublaminae of the EPL and along the length of M/T secondary dendrites. In electron micrographs the M/T to granule cell synapse appeared to predominate and was equivalent in both the outer and inner EPL. However, the dendrodendritic synapses from granule cell spines onto M/T dendrites were more prevalent in the outer EPL. In contrast, individual gephyrin-immunoreactive (IR) puncta, a postsynaptic scaffolding protein at inhibitory synapses used here as a proxy for the granule to M/T dendritic synapse was equally distributed throughout the EPL. Of significance to the organization of intrabulbar circuits, gephyrin-IR synapses are not uniformly distributed along M/T secondary dendrites. Synaptic density, expressed as a function of surface area, increases distal to the cell body. Furthermore, the distributions of gephyrin-IR puncta are heterogeneous and appear as clusters along the length of the M/T dendrites. Consistent with computational models, our data suggest that temporal coding in M/T cells is achieved by precisely located inhibitory input and that distance from the soma is compensated for by an increase in synaptic density.Fil: Bartel, Dianna L.. University Of Yale. School Of Medicine; Estados UnidosFil: Rela, Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Fisiología y Biofísica Bernardo Houssay; Argentina. Universidad de Buenos Aires. Facultad de Medicina; ArgentinaFil: Hsieh, Lawrence. University Of Yale. School Of Medicine; Estados UnidosFil: Greer, Charles A. . University Of Yale. School Of Medicine; Estados Unido

Konsequenzen wald- und forstgeschichtlicher Entwicklungen für die aktuelle genetische Zusammensetzung von Waldbaumpopulationen in Mitteleuropa

Im Hinblick auf die Erhaltung und nachhaltige Nutzung der biologischen Vielfalt in Wäl- dern und die Einschätzung der gegenwärtigen Angepaßtheit und Anpassungsfähigkeit von Waldbaumpopulationen erfolgt eine neuartige, interdisziplinäre Bearbeitung ihrer anpassungsrelevanten Vorgeschichte durch die Bildung systemanalytischen AnsprÜ- chen genügender Hypothesen über Auswirkungen wald- bzw. forstgeschichtlicher Ent- wicklungen auf den gegenwärtigen genetischen Zustand von Waldbaumpopulationen in Deutschland. Auf der Grundlage von Erfordernissen für erfolgreiche Anpassungs- prozesse sowie genetischer Voraussetzungen für den nachhaltigen Umgang mit Wald- ökosystem-Ressourcen belegt die Analyse eine erhebliche Einschränkung von Ange- paßtheit und Anpassungsfähigkeit gegenwärtiger Waldbaumpopulationen durch diver- se historische Beeinträchtigungen der adaptiven Selbstregulationsmechanismen sowie ihrer genetischen Grundlagen. Die Anwendung eines geographischen Informationssys- tems (Darstellung der räumlichen Verbreitung genetischer Parameter) sowie phyloge- netischer bzw. phylogeographischer Methoden (Rekonstruktion der Abstammungsver- hältnisse von Populationen) am Beispiel der Baumart Buche (Fagus sylvatica L.) er- mÖglicht u. a. Einblicke in die nacheiszeitlichen Rückwanderungswege sowie forsthis- torisch bedingte Störungen der Autochthonie rezenter Waldbaumpopulationen. Für den in Anbetracht zu erwartender Klimaänderungen erforderlichen, nachhaltigen Umgang mit Waldökosystem-Ressourcen werden konkrete Handlungsanweisungen für die Forstpraxis gegeben. Im Hinblick auf die weitere Bearbeitung von Fragen der nachhal- tigen Waldnutzung werden wichtige Grundlagen u.a. für die Modeliierung historischer Einflüsse auf die Verteilung genetischer Variation in Zeit und Raum sowie erste Ansät- ze zur Lösung des Problems der Identifikation von Autochthonie von Pflanzenpopulati- onen aufgezeigt. Die Ergebnisse verdeutlichen, daß im Rahmen prospektiver Umwelt- forschung die Berücksichtigung interdisziplinärer, retrospektiver Forschung unerläßlich ist

Out-of-home delivery in last-mile logistics: a review

In light of labor shortages, rising fuel costs, and thin profit margins, providers of last-mile delivery services face a mounting pressure to innovate. One avenue to more efficient last-mile operations is the incorporation of out-of-home delivery (OOHD) services. OOHD, i.e., the delivery to parcel shops and parcel lockers, instead of customers’ homes, offers manifold advantages, including the consolidation of customers into a single delivery location and a reduction in the number of failed delivery attempts. In the past five years, the number of scientific publications dealing with optimization problems in the context of OOHD has increased rapidly. In this survey, we assess the various opportunities for optimization in OOHD-based concepts for last mile logistics. Categorizing their manifold aspects, we provide a classification of problem components and point out key challenges. We then present comprehensive overviews of the literature for all three major decision types (facility location, vehicle routing, location routing). Finally, we extensively discuss gaps in the current literature and indicate directions for future research