186 research outputs found
Light-driven liquid crystalline nonlinear oscillator under optical periodic forcing
An all-optically driven strategy to govern a liquid crystalline collective
molecular nonlinear oscillator is discussed. It does not require external
feedbacks of any kind while the oscillator and a time-depending perturbation
both are sustained by incident light. Various dynamical regimes such as
frequency -locked, quasiperiodic, forced and chaotic are observed in agreement
with a theoretical approach developed in the limit of the plane wave
approximation.Comment: 5 pages, 6 figures, submitted to Phys. Rev.
Two interacting particles in a random potential
We study the scaling of the localization length of two interacting particles
in a one-dimensional random lattice with the single particle localization
length. We obtain several regimes, among them one interesting weak Fock space
disorder regime. In this regime we derive a weak logarithmic scaling law.
Numerical data support the absence of any strong enhancement of the two
particle localization length
Effects of maternal subnutrition during early pregnancy on cow hematological profiles and offspring physiology and vitality in two beef breeds
This experiment evaluated the effects of subnutrition during early gestation on hematology in cows (Bos Taurus) and on hematological, metabolic, endocrine, and vitality parameters in their calves. Parda de Montaña and Pirenaica dams were inseminated and assigned to either a control (CONTROL, 100% requirements) or a nutrientârestricted group (SUBNUT, 65%) during the first third of gestation. Dam blood samples were collected on days 20 and 253 of gestation, and calf samples were obtained during the first days of life. Pirenaica dams presented higher red series parameters than Parda de Montaña dams, both in the first and the last months of gestation. During early pregnancy, granulocyte numbers and mean corpuscular hemoglobin were lower in PirenaicaâSUBNUT than in PirenaicaâCONTROL cows. Calves from the SUBNUT cows did not show a physiological reduction in red series values in early life, suggesting later maturation of the hematopoietic system. Poor maternal nutrition affected calf endocrine parameters. Newborns from dystocic parturitions showed lower NEFA concentrations and weaker vitality responses. In conclusion, maternal nutrition had shortâterm effects on cow hematology, Pirenaica cows showing a higher susceptibility to undernutrition; and a longâterm effect on their offspring endocrinology, SUBNUT newborns showing lower levels of IGFâ1 and higher levels of cortisol.This work was supported by the Spanish Ministry of Economy and Business and the European Union Regional Development Funds (INIA RTA 2013â00059âC02 and INIA RZP 2015â001) and the Government of Aragon under the Grant Research Group Funds (A14_17R). A. Noya received a PhD grant from INIAâGovernment of Aragon
Distinct properties of layer 3 pyramidal neurons from prefrontal and parietal areas of the monkey neocortex
In primates, working memory function depends on activity in a distributed network of cortical areas that display different patterns of delay task-related activity. These differences are correlated with, and might depend on, distinctive properties of the neurons located in each area. For example, layer 3 pyramidal neurons (L3PNs) differ significantly between primary visual and dorsolateral prefrontal (DLPFC) cortices. However, to what extent L3PNs differ between DLPFC and other association cortical areas is less clear. Hence, we compared the properties of L3PNs in monkey DLPFC versus posterior parietal cortex (PPC), a key node in the cortical working memory network. Using patch-clamp recordings and biocytin cell filling in acute brain slices, we assessed the physiology and morphology of L3PNs from monkey DLPFC and PPC. The L3PN transcriptome was studied using laser microdissection combined with DNA microarray or quantitative PCR. We found that in both DLPFC and PPC, L3PNs were divided into regular spiking (RS-L3PNs) and bursting (B-L3PNs) physiological subtypes. Whereas regional differences in single-cell excitability were modest, B-L3PNs were rare in PPC (RS-L3PN:BL3PN, 94:6), but were abundant in DLPFC (50:50), showing greater physiological diversity. Moreover, DLPFC L3PNs display larger and more complex basal dendrites with higher dendritic spine density. Additionally, we found differential expression of hundreds of genes, suggesting a transcriptional basis for the differences in L3PN phenotype between DLPFC and PPC. These data show that the previously observed differences between DLPFC and PPC neuron activity during working memory tasks are associated with diversity in the cellular/ molecular properties of L3PNs.Fil: Gonzalez Burgos, Guillermo. Univeristy of Pittsburgh. School of Medicine; Estados UnidosFil: Miyamae, Takeaki. Univeristy of Pittsburgh. School of Medicine; Estados UnidosFil: Krimer, Yosef. Univeristy of Pittsburgh. School of Medicine; Estados UnidosFil: Gulchina, Yelena. Univeristy of Pittsburgh. School of Medicine; Estados UnidosFil: Pafundo, Diego Esteban. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay. Instituto de FisiologĂa y BiofĂsica Bernardo Houssay. Universidad de Buenos Aires. Facultad de Medicina. Instituto de FisiologĂa y BiofĂsica Bernardo Houssay; ArgentinaFil: Krimer, Olga. Univeristy of Pittsburgh. School of Medicine; Estados UnidosFil: Bazmi, Holly. Univeristy of Pittsburgh. School of Medicine; Estados UnidosFil: Arion, Dominique. Univeristy of Pittsburgh. School of Medicine; Estados UnidosFil: Enwright, John F.. Univeristy of Pittsburgh. School of Medicine; Estados UnidosFil: Fish, Kenneth N.. Univeristy of Pittsburgh. School of Medicine; Estados UnidosFil: Lewis, David A.. Univeristy of Pittsburgh. School of Medicine; Estados Unido
Nonlinear Lattice Waves in Random Potentials
Localization of waves by disorder is a fundamental physical problem
encompassing a diverse spectrum of theoretical, experimental and numerical
studies in the context of metal-insulator transition, quantum Hall effect,
light propagation in photonic crystals, and dynamics of ultra-cold atoms in
optical arrays. Large intensity light can induce nonlinear response, ultracold
atomic gases can be tuned into an interacting regime, which leads again to
nonlinear wave equations on a mean field level. The interplay between disorder
and nonlinearity, their localizing and delocalizing effects is currently an
intriguing and challenging issue in the field. We will discuss recent advances
in the dynamics of nonlinear lattice waves in random potentials. In the absence
of nonlinear terms in the wave equations, Anderson localization is leading to a
halt of wave packet spreading.
Nonlinearity couples localized eigenstates and, potentially, enables
spreading and destruction of Anderson localization due to nonintegrability,
chaos and decoherence. The spreading process is characterized by universal
subdiffusive laws due to nonlinear diffusion. We review extensive computational
studies for one- and two-dimensional systems with tunable nonlinearity power.
We also briefly discuss extensions to other cases where the linear wave
equation features localization: Aubry-Andre localization with quasiperiodic
potentials, Wannier-Stark localization with dc fields, and dynamical
localization in momentum space with kicked rotors.Comment: 45 pages, 19 figure
Reflection resonances in surface-disordered waveguides: strong higher-order effects of the disorder
We study coherent wave scattering through waveguides with a step-like surface disorder and find distinct enhancements in the reflection coefficients at well-defined resonance values. Based on detailed numerical and analytical calculations, we can unambiguously identify the origin of these reflection resonances to be higher-order correlations in the surface disorder profile which are typically neglected in similar studies of the same system. A remarkable feature of this new effect is that it relies on the longitudinal correlations in the step profile, although individual step heights are random and thus completely uncorrelated. The corresponding resonances are very pronounced and robust with respect to ensemble averaging, and lead to an enhancement of wave reflection by more than one order of magnitude.Peer Reviewe
Delocalization of wave packets in disordered nonlinear chains
We consider the spatiotemporal evolution of a wave packet in disordered
nonlinear Schr\"odinger and anharmonic oscillator chains. In the absence of
nonlinearity all eigenstates are spatially localized with an upper bound on the
localization length (Anderson localization). Nonlinear terms in the equations
of motion destroy Anderson localization due to nonintegrability and
deterministic chaos. At least a finite part of an initially localized wave
packet will subdiffusively spread without limits. We analyze the details of
this spreading process. We compare the evolution of single site, single mode
and general finite size excitations, and study the statistics of detrapping
times. We investigate the properties of mode-mode resonances, which are
responsible for the incoherent delocalization process.Comment: 14 pages, 9 figures, accepted for publication in Phys. Rev.
Electrophoretic mobility of supercoiled, catenated and knotted DNA molecules.
We systematically varied conditions of two-dimensional (2D) agarose gel electrophoresis to optimize separation of DNA topoisomers that differ either by the extent of knotting, the extent of catenation or the extent of supercoiling. To this aim we compared electrophoretic behavior of three different families of DNA topoisomers: (i) supercoiled DNA molecules, where supercoiling covered the range extending from covalently closed relaxed up to naturally supercoiled DNA molecules; (ii) postreplicative catenanes with catenation number increasing from 1 to âŒ15, where both catenated rings were nicked; (iii) knotted but nicked DNA molecules with a naturally arising spectrum of knots. For better comparison, we studied topoisomer families where each member had the same total molecular mass. For knotted and supercoiled molecules, we analyzed dimeric plasmids whereas catenanes were composed of monomeric forms of the same plasmid. We observed that catenated, knotted and supercoiled families of topoisomers showed different reactions to changes of agarose concentration and voltage during electrophoresis. These differences permitted us to optimize conditions for their separation and shed light on physical characteristics of these different types of DNA topoisomers during electrophoresis
Electrophysiological Heterogeneity of Fast-Spiking Interneurons: Chandelier versus Basket Cells
In the prefrontal cortex, parvalbumin-positive inhibitory neurons play a prominent role in the neural circuitry that subserves working memory, and alterations in these neurons contribute to the pathophysiology of schizophrenia. Two morphologically distinct classes of parvalbumin neurons that target the perisomatic region of pyramidal neurons, chandelier cells (ChCs) and basket cells (BCs), are generally thought to have the same "fast-spiking" phenotype, which is characterized by a short action potential and high frequency firing without adaptation. However, findings from studies in different species suggest that certain electrophysiological membrane properties might differ between these two cell classes. In this study, we assessed the physiological heterogeneity of fast-spiking interneurons as a function of two factors: species (macaque monkey vs. rat) and morphology (chandelier vs. basket). We showed previously that electrophysiological membrane properties of BCs differ between these two species. Here, for the first time, we report differences in ChCs membrane properties between monkey and rat. We also found that a number of membrane properties differentiate ChCs from BCs. Some of these differences were species-independent (e.g., fast and medium afterhyperpolarization, firing frequency, and depolarizing sag), whereas the differences in the first spike latency between ChCs and BCs were species-specific. Our findings indicate that different combinations of electrophysiological membrane properties distinguish ChCs from BCs in rodents and primates. Such electrophysiological differences between ChCs and BCs likely contribute to their distinctive roles in cortical circuitry in each species. © 2013 Povysheva et al
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