826 research outputs found
The effects of paroxetine on cognitive function in healthy volunteers and depressed elderly patients
Irreducible free energy expansion and overlaps locking in mean field spin glasses
We introduce a diagrammatic formulation for a cavity field expansion around
the critical temperature. This approach allows us to obtain a theory for the
overlap's fluctuations and, in particular, the linear part of the
Ghirlanda-Guerra relationships (GG) (often called Aizenman-Contucci polynomials
(AC)) in a very simple way. We show moreover how these constraints are
"superimposed" by the symmetry of the model with respect to the restriction
required by thermodynamic stability. Within this framework it is possible to
expand the free energy in terms of these irreducible overlaps fluctuations and
in a form that simply put in evidence how the complexity of the solution is
related to the complexity of the entropy.Comment: 19 page
Dark conglomerate phases of bent-core liquid crystals
Spontaneous or induced chiral symmetry breaking in achiral systems is unusual and understanding the origin of such a phenomenon has been an important area of research for several years. The optically isotropic mesophases exhibited by unconventional liquid crystals are one of the most interesting systems to investigate spontaneous chiral symmetry breaking in liquid crystal mesophases formed by achiral moieties. The dark conglomerate (DC) phases are one such optically isotropic family of phases. In this paper, a detailed account of the tendency of bent-core mesogens to form a variety of polar smectic phases, the formation of DC phases due to layers deformations and the general optical, electrical, physical properties of the DC phases are given. An example of a DC phase which exhibit distinct electro-optic properties is described with the nature of dynamics of the response and physical reasons responsible for such behaviour. The challenges and prospects of the DC phases are discussed for their potential applications in novel devices
Probing molecular chirality by coherent optical absorption spectra
We propose an approach to sensitively probe the chirality of molecules by
measuring their coherent optical absorption spectra. It is shown that quantum
dynamics of the cyclic three-level chiral molecules driven by
appropriately-designed external fields is total-phase dependent. This will
result in chirality-dependent absorption spectra for the probe field. As a
consequence, these absorption spectra can be utilized to identify molecular
chirality and determinate enantiomer excess. The feasibility of the proposal
with chiral molecules confined in hollow-core photonic crystal fiber (HC-PCF)
is also discussed.Comment: 4 pages, 4 figure
Chiral Nanoceramics
The study of different chiral inorganic nanomaterials has been experiencing rapid growth during the past decade, with its primary focus on metals and semiconductors. Ceramic materials can substantially expand the range of mechanical, optical, chemical, electrical, magnetic, and biological properties of chiral nanostructures, further stimulating theoretical, synthetic, and applied research in this area. An ever‐expanding toolbox of nanoscale engineering and self‐organization provides a chirality‐based methodology for engineering of hierarchically organized ceramic materials. However, fundamental discoveries and technological translations of chiral nanoceramics have received substantially smaller attention than counterparts from metals and semiconductors. Findings in this research area are scattered over a variety of sources and subfields. Here, the diversity of chemistries, geometries, and properties found in chiral ceramic nanostructures are summarized. They represent a compelling materials platform for realization of chirality transfer through multiple scales that can result in new forms of ceramic materials. Multiscale chiral geometries and the structural versatility of nanoceramics are complemented by their high chiroptical activity, enantioselectivity, catalytic activity, and biocompatibility. Future development in this field is likely to encompass chiral synthesis, biomedical applications, and optical/electronic devices. The implementation of computationally designed chiral nanoceramics for biomimetic catalysts and quantum information devices may also be expected.Chiral nanoceramics are emerging as a remarkably active area of chiral research. It is still in its infant stage and is thus full of challenges and opportunities. Recent advances in the diversity of chemistries, geometries, and properties of chiral ceramic nanostructures are reviewed. An outlook of synthesis, computational methods, and emerging applications of chiral nanoceramics is presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163453/2/adma201906738_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163453/1/adma201906738.pd
On the Microscopic Origin of Cholesteric Pitch
We present a microscopic analysis of the instability of the nematic phase to
chirality when molecular chirality is introduced perturbatively. We show that
previously neglected short-range biaxial correlations play a crucial role in
determining the cholesteric pitch. We propose an order parameter which
quantifies the chirality of a molecule.Comment: RevTeX 3.0, 4 pages, one included eps figure. Published versio
Chirality transfer and stereo-selectivity of imprinted cholesteric networks
Imprinting of cholesteric textures in a polymer network is a method of
preserving a macroscopically chiral phase in a system with no molecular
chirality. By modifying the elastics properties of the network, the resulting
stored helical twist can be manipulated within a wide range since the
imprinting efficiency depends on the balance between the elastics constants and
twisting power at network formation. One spectacular property of phase
chirality imprinting is the created ability of the network to adsorb
preferentially one stereo-component from a racemic mixture. In this paper we
explore this property of chirality transfer from a macroscopic to the molecular
scale. In particular, we focus on the competition between the phase chirality
and the local nematic order. We demonstrate that it is possible to control the
subsequent release of chiral solvent component from the imprinting network and
the reversibility of the stereo-selective swelling by racemic solvents
Observation of a Chiral State in a Microwave Cavity
A microwave experiment has been realized to measure the phase difference of
the oscillating electric field at two points inside the cavity. The technique
has been applied to a dissipative resonator which exhibits a singularity --
called exceptional point -- in its eigenvalue and eigenvector spectrum. At the
singularity, two modes coalesce with a phase difference of We
conclude that the state excited at the singularity has a definitiv chirality.Comment: RevTex 4, 5 figure
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