•Fish hydrolysate contains n-3 LC-PUFAs and low molecular weight peptides.•Fish hydrolysate prevents age-related short-term memory deficits.•Fish hydrolysate affects navigation strategies during ...spatial learning.•Fish hydrolysate possesses immunomodulatory and anxiolytic properties.•Fish hydrolysate is promising for the prevention of age-related cognitive decline.
Brain aging is characterized by a decline in cognitive functions, which can lead to the development of neurodegenerative pathologies. Age-related spatial learning and memory deficits are associated with a chronic low-grade inflammation. Anxiety disorders and stress response alterations, occurring for a part of the elderly, have also been linked to an increased neuroinflammation and thus, an accelerated cognitive decline. Nutrition is an innovative strategy to prevent age-related cognitive impairments. Among the nutrients, n-3 long chain polyunsaturated fatty acids (LC-PUFAs) and low molecular weight peptides from proteins, especially those from marine resources, are good candidates for their immunomodulatory, anxiolytic and neuroprotective properties. The aim of this study is to determine the combined effect of n-3 LC-PUFAs and low molecular weight peptides on cognitive functions, and their mechanism of action. We are the first to show that a dietary supplementation with a fish hydrolysate containing n-3 LC-PUFAs and low molecular weight peptides prevented the age-related spatial short-term memory deficits and modulated navigation strategies adopted during spatial learning. In addition, the fish hydrolysate displayed anxiolytic activities with the reduction of anxiety-like behaviour in aged mice, restored the plasmatic corticosterone levels similar to adult animals following an acute stress and modulated the hypothalamic stress response. These effects on behaviour can be explained by the immunomodulatory and neuroprotective properties of the fish hydrolysate that limited microgliosis in vivo, decreased LPS-induced expression of pro-inflammatory cytokines and increased the expression of growth factors such as BDNF and NGF in vitro. Thus, n-3 LC-PUFAs and low molecular weight peptides contained in the fish hydrolysate can play an important role in the limitation of neuroinflammation and stress response alterations during aging and represent a potential strategy for the prevention of age-related cognitive decline.
We consider two bidimensional random models characterised by the following features: (a) their Hamiltonians are separable in polar coordinates and (b) the random part of the potential depends either ...on the angular coordinate or on the radial one, but not on both. The disorder correspondingly localises the angular or the radial part of the eigenfunctions. We analyse the analogies and the differences which exist between the selected 2D models and their 1D counterparts. We show how the analogies allow one to use correlated disorder to design a localisation length with pre-defined energy dependence and to produce directional localisation of the wavefunctions in models with angular disorder. We also discuss the importance of finite-size and resonance effects in shaping the eigenfunctions of the model with angular disorder; for the model with disorder associated to the radial variable we show under what conditions the localisation length coincides with the expression valid in the 1D case.
A novel approach to investigate the electron transport of cis- and trans-polyacetylene chains in the single-electron approximation is presented by using microwave emulation measurements and ...tight-binding calculations. In the emulation we take into account the different electronic couplings due to the double bonds leading to coupled dimer chains. The relative coupling constants are adjusted by DFT calculations. For sufficiently long chains a transport band gap is observed if the double bonds are present, whereas for identical couplings no band gap opens. The band gap can be observed also in relatively short chains, if additional edge atoms are absent, which cause strong resonance peaks within the band gap. The experimental results are in agreement with our tight-binding calculations using the nonequilibrium Green's function method. The tight-binding calculations show that it is crucial to include third nearest neighbor couplings to obtain the gap in the cis-polyacetylene.
•Electronic transport in individual polyacetylene chains is studied.•Microwave emulation experiments and tight-binding calculations agree well.•In long chains a band-gap opens due the dimerization of the chain.•In short chains edge atoms cause strong resonance peaks in the center of the band-gap.
Current vortices in aromatic carbon molecules Stegmann, Thomas; Franco-Villafañe, John A.; Ortiz, Yenni P. ...
Physical review. B,
08/2020, Letnik:
102, Številka:
7
Journal Article
Recenzirano
Odprti dostop
The local current flow through three small aromatic carbon molecules, namely, benzene, naphthalene, and anthracene, is studied. Applying density functional theory and the nonequilibrium Green's ...function method for transport, we demonstrate that pronounced current vortices exist at certain electron energies for these molecules. The intensity of these circular currents, which appear not only at the antiresonances of the transmission but also in the vicinity of its maxima, can exceed the total current flowing through the molecular junction and generate considerable magnetic fields. The π electron system of the molecular junctions is emulated experimentally by a network of macroscopic microwave resonators. The local current flows in these experiments confirm the existence of current vortices as a robust property of ring structures. The circular currents can be understood in terms of a simple nearest-neighbor tight-binding Hückel model. Current vortices are caused by the interplay of the complex eigenstates of the open system which have energies close to the considered electron energy. Degeneracies, as observed in benzene and anthracene, can thus generate strong circular currents, but also nondegenerate systems like naphthalene exhibit current vortices. Small imperfections and perturbations can couple otherwise uncoupled states and induce circular currents.
Phase singularities appear ubiquitously in wavefields, regardless of the wave equation. Such topological defects can lead to wavefront dislocations, as observed in a humongous number of classical ...wave experiments. Phase singularities of wave functions are also at the heart of the topological classification of the gapped phases of matter. Despite identical singular features, topological insulators and topological defects in waves remain two distinct fields. Realising 1D microwave insulators, we experimentally observe a wavefront dislocation - a 2D phase singularity - in the local density of states when the systems undergo a topological phase transition. We show theoretically that the change in the number of interference fringes at the transition reveals the topological index that characterises the band topology in the insulator.
We report noninvasive measurements of the complex field of elastic quasimodes of a silicon wafer with chaotic shape. The amplitude and phase spatial distribution of the flexural modes are directly ...obtained by Fourier transform of time measurements. We investigate the crossover from real mode to complex-valued quasimode, when absorption is progressively increased on one edge of the wafer. The complexness parameter, which characterizes the degree to which a resonance state is complex valued, is measured for nonoverlapping resonances, and is found to be proportional to the nonhomogeneous contribution to the line broadening of the resonance. A simple two-level model based on the effective Hamiltonian formalism supports our experimental results.
Wave billiards which are chaotic in the geometrical limit are known to support nongeneric spatially localized modes called scar modes. The interaction of the scar modes with gain has been recently ...investigated in optics in microcavity lasers and vertical-cavity surface-emitting lasers. Exploiting the localization properties of scar modes in their wave-analogous phase-space representation, we report experimental results of scar mode selection by gain in a doped D-shaped optical fiber.
We present an experimental study of the influence of the inner cladding geometry on pump power absorption in double clad fibres. The experimental results are analyzed by taking into consideration the ...spatial intensity distribution of the modes in the inner cladding. Six different geometries and core dopant are investigated. By comparing the pump power absorption evolution along each fibre, we show that using a chaotic inner cladding geometry, a constant absorption coefficient is achieved independently of the launching light condition.
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