On magnetic leaf-wise intersections

In this article we introduce the notion of a magnetic leaf-wise intersection point which is a generalization of the leaf-wise intersection point with magnetic effects. We also prove the existence of magnetic leaf-wise intersection points under certain topological assumptions.Comment: 43 page

The Conley Conjecture and Beyond

This is (mainly) a survey of recent results on the problem of the existence of infinitely many periodic orbits for Hamiltonian diffeomorphisms and Reeb flows. We focus on the Conley conjecture, proved for a broad class of closed symplectic manifolds, asserting that under some natural conditions on the manifold every Hamiltonian diffeomorphism has infinitely many (simple) periodic orbits. We discuss in detail the established cases of the conjecture and related results including an analog of the conjecture for Reeb flows, the cases where the conjecture is known to fail, the question of the generic existence of infinitely many periodic orbits, and local geometrical conditions that force the existence of infinitely many periodic orbits. We also show how a recently established variant of the Conley conjecture for Reeb flows can be applied to prove the existence of infinitely many periodic orbits of a low-energy charge in a non-vanishing magnetic field on a surface other than a sphere.Comment: 34 pages, 1 figur

Self-Organized Criticality in Developing Neuronal Networks

Recently evidence has accumulated that many neural networks exhibit self-organized criticality. In this state, activity is similar across temporal scales and this is beneficial with respect to information flow. If subcritical, activity can die out, if supercritical epileptiform patterns may occur. Little is known about how developing networks will reach and stabilize criticality. Here we monitor the development between 13 and 95 days in vitro (DIV) of cortical cell cultures (n = 20) and find four different phases, related to their morphological maturation: An initial low-activity state (≈19 DIV) is followed by a supercritical (≈20 DIV) and then a subcritical one (≈36 DIV) until the network finally reaches stable criticality (≈58 DIV). Using network modeling and mathematical analysis we describe the dynamics of the emergent connectivity in such developing systems. Based on physiological observations, the synaptic development in the model is determined by the drive of the neurons to adjust their connectivity for reaching on average firing rate homeostasis. We predict a specific time course for the maturation of inhibition, with strong onset and delayed pruning, and that total synaptic connectivity should be strongly linked to the relative levels of excitation and inhibition. These results demonstrate that the interplay between activity and connectivity guides developing networks into criticality suggesting that this may be a generic and stable state of many networks in vivo and in vitro

Secondary crystalline phases identification in Cu2ZnSnSe4 thin films: contributions from Raman scattering and photoluminescence

In this work, we present the Raman peak positions of the quaternary pure selenide compound Cu2ZnSnSe4 (CZTSe) and related secondary phases that were grown and studied under the same conditions. A vast discussion about the position of the X-ray diffraction (XRD) reflections of these compounds is presented. It is known that by using XRD only, CZTSe can be identified but nothing can be said about the presence of some secondary phases. Thin films of CZTSe, Cu2SnSe3, ZnSe, SnSe, SnSe2, MoSe2 and a-Se were grown, which allowed their investigation by Raman spectroscopy (RS). Here we present all the Raman spectra of these phases and discuss the similarities with the spectra of CZTSe. The effective analysis depth for the common back-scattering geometry commonly used in RS measurements, as well as the laser penetration depth for photoluminescence (PL) were estimated for different wavelength values. The observed asymmetric PL band on a CZTSe film is compatible with the presence of CZTSe single-phase and is discussed in the scope of the fluctuating potentials’ model. The estimated bandgap energy is close to the values obtained from absorption measurements. In general, the phase identification of CZTSe benefits from the contributions of RS and PL along with the XRD discussion.info:eu-repo/semantics/publishedVersio

Serotonergic chemosensory neurons modify the <i>C. elegans</i> immune response by regulating G-protein signaling in epithelial cells

The nervous and immune systems influence each other, allowing animals to rapidly protect themselves from changes in their internal and external environment. However, the complex nature of these systems in mammals makes it difficult to determine how neuronal signaling influences the immune response. Here we show that serotonin, synthesized in Caenorhabditis elegans chemosensory neurons, modulates the immune response. Serotonin released from these cells acts, directly or indirectly, to regulate G-protein signaling in epithelial cells. Signaling in these cells is required for the immune response to infection by the natural pathogen Microbacterium nematophilum. Here we show that serotonin signaling suppresses the innate immune response and limits the rate of pathogen clearance. We show that C. elegans uses classical neurotransmitters to alter the immune response. Serotonin released from sensory neurons may function to modify the immune system in response to changes in the animal's external environment such as the availability, or quality, of food