784 research outputs found
Pseudospin and nonlinear conical diffraction in Lieb lattices
We study linear and nonlinear wave dynamics in the Lieb lattice, in the vicinity of an intersection point between two conical bands and a flat band. We define a pseudospin operator and derive a nonlinear equation for spin-1 waves, analogous to the spin-1/2 nonlinear Dirac equation. We then study the dynamics of wave packets that are associated with different pseudospin states, and find that they are distinguished by their linear and nonlinear conical diffraction patterns
Hiding the Higgs at the LHC
We study a simple extension of the standard model where scalar singlets that
mix with the Higgs doublet are added. This modification to the standard model
could have a significant impact on Higgs searches at the LHC. The Higgs doublet
is not a mass eigenstate and therefore the expected nice peak of the standard
model Higgs disappears. We analyze this scenario finding the required
properties of the singlets in order to make the Higgs "invisible" at the LHC.
In some part of the parameter space even one singlet could make the discovery
of the SM Higgs problematic. In other parts, the Higgs can be discovered even
in the presence of many singlets.Comment: 9 pages, 1 figure. V2- References added. V3- Several examples and one
fig. adde
Flat band states: disorder and nonlinearity
We study the critical behavior of Anderson localized modes near intersecting flat and dispersive bands in the quasi-one-dimensional diamond ladder with weak diagonal disorder W. The localization length ξ of the flat band states scales with disorder as ξ∼W-γ, with γ≈1.3, in contrast to the dispersive bands with γ=2. A small fraction of dispersive modes mixed with the flat band states is responsible for the unusual scaling. Anderson localization is therefore controlled by two different length scales. Nonlinearity can produce qualitatively different wave spreading regimes, from enhanced expansion to resonant tunneling and self-trapping
Nonverbal Communication of Similarity via the Torso: It’s in the Bag
The human body plays a central role in nonverbal communication, conveying attitudes, personality, and values during social interactions. Three experiments in a large, open classroom setting investigated whether the visibility of torso-located cues affects nonverbal communication of similarity. In Expts. 1 and 2, half the participants wore a black plastic bag over their torso. Participants interacted with an unacquainted same-sex individual selected from a large class who was also wearing (or also not wearing) a bag. Expt. 3 added a clear bag condition, in which visual torso cues were not obscured. Across experiments, black bag-wearing participants selected partners who were less similar to them on attitudes, behaviors, and personality compared to the bag-less—and clear bag—participants. Nonverbal cues in the torso communicate information about similarity of attitudes, behavior, and personality; the center of the body plays a surprisingly central role in early-stage person perception and attraction
Accurate Vertical Ionization Energy of Water and Retrieval of True Ultraviolet Photoelectron Spectra of Aqueous Solutions
Ultraviolet (UV) photoelectron spectroscopy provides a direct way of measuring valence electronic structure; however, its application to aqueous solutions has been hampered by a lack of quantitative understanding of how inelastic scattering of low-energy (<5 eV) electrons in liquid water distorts the measured electron kinetic energy distributions. Here, we present an efficient and widely applicable method for retrieving true UV photoelectron spectra of aqueous solutions. Our method combines Monte Carlo simulations of electron scattering and spectral inversion, with molecular dynamics simulations of depth profiles of organic solutes in aqueous solution. Its application is demonstrated for both liquid water, and aqueous solutions of phenol and phenolate, which are ubiquitous biologically relevant structural motifs
The outer limiting membrane (OLM) revisited: clinical implications
PURPOSE: The outer limiting membrane (OLM) is considered to play a role in maintaining the structure of the retina through mechanical strength. However, the observation of junction proteins located at the OLM and its barrier permeability properties may suggest that the OLM may be part of the retinal barrier.
MATERIAL AND METHODS: Normal and diabetic rat, monkey, and human retinas were used to analyze junction proteins at the OLM. Proteome analyses were performed using immunohistochemistry on sections and flat-mounted retinas and western blotting on protein extracts obtained from laser microdissection of the photoreceptor layers. Semi-thin and ultrastructure analyses were also reported.
RESULTS: In the rat retina, in the subapical region zonula occludens-1 (ZO-1), junction adhesion molecule (JAM), an atypical protein kinase C, is present and the OLM shows dense labeling of occludin, JAM, and ZO-1. The presence of occludin has been confirmed using western blot analysis of the microdissected OLM region. In diabetic rats, occludin expression is decreased and glial cells junctions are dissociated. In the monkey retina, occludin, JAM, and ZO-1 are also found in the OLM. Junction proteins have a specific distribution around cone photoreceptors and Müller glia. Ultrastructural analyses suggest that structures like tight junctions may exist between retinal glial Müller cells and photoreceptors.
CONCLUSIONS: In the OLM, heterotypic junctions contain proteins from both adherent and tight junctions. Their structure suggests that tight junctions may exist in the OLM. Occludin is present in the OLM of the rat and monkey retina and it is decreased in diabetes. The OLM should be considered as part of the retinal barrier that can be disrupted in pathological conditions contributing to fluid accumulation in the macula
Anomalous Scaling in a Model of Passive Scalar Advection: Exact Results
Kraichnan's model of passive scalar advection in which the driving velocity
field has fast temporal decorrelation is studied as a case model for
understanding the appearance of anomalous scaling in turbulent systems. We
demonstrate how the techniques of renormalized perturbation theory lead (after
exact resummations) to equations for the statistical quantities that reveal
also non perturbative effects. It is shown that ultraviolet divergences in the
diagrammatic expansion translate into anomalous scaling with the inner length
acting as the renormalization scale. In this paper we compute analytically the
infinite set of anomalous exponents that stem from the ultraviolet divergences.
Notwithstanding, non-perturbative effects furnish a possibility of anomalous
scaling based on the outer renormalization scale. The mechanism for this
intricate behavior is examined and explained in detail. We show that in the
language of L'vov, Procaccia and Fairhall [Phys. Rev. E {\bf 50}, 4684 (1994)]
the problem is ``critical" i.e. the anomalous exponent of the scalar primary
field . This is precisely the condition that allows for
anomalous scaling in the structure functions as well, and we prove that this
anomaly must be based on the outer renormalization scale. Finally, we derive
the scaling laws that were proposed by Kraichnan for this problem, and show
that his scaling exponents are consistent with our theory.Comment: 43 pages, revtex
Magnetic properties and interlayer coupling in Co/V multilayers
The magnetic properties of evaporated Co/V multilayer films have been studied by superconducting quantum interference device magnetometer and ferromagnetic-resonance (FMR). FMR has been used to study the interlayer exchange coupling and the FMR linewidth in Co/V multilayers at room temperature. Spin-waves resonance modes were observed in some Co/V multilayers and the relation of resonant field Hres with the mode number n obeys the so-called n2 law. The interlayer coupling constant was determined. The FMR linewidth, in parallel geometry, of the uniform mode was found to increase with decreasing Co thickness (10Å £ tCo £ 45Å) indicating that it corresponds to an interfacial effect
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