6,421 research outputs found
Liquid-core low-refractive-index-contrast Bragg fiber sensor
We propose and experimentally demonstrate a low-refractive-index-contrast
hollow-core Bragg fiber sensor for liquid analyte refractive index detection.
The sensor operates using a resonant sensing principle- when the refractive
index of a liquid analyte in the fiber core changes, the resonant confinement
of the fiber guided mode will also change, leading to both the spectral shifts
and intensity changes in fiber transmission. As a demonstration, we
characterize the Bragg fiber sensor using a set of NaCl solutions with
different concentrations. Strong spectral shifts are obtained with the sensor
experimental sensitivity found to be ~1400nm/RIU (refractive index unit).
Besides, using theoretical modeling we show that low-refractive-index-contrast
Bragg fibers are more suitable for liquid-analyte sensing applications than
their high-refractive-index-contrast counterparts.Comment: 3 pages, 4 figure
Relevance of Abelian Symmetry and Stochasticity in Directed Sandpiles
We provide a comprehensive view on the role of Abelian symmetry and
stochasticity in the universality class of directed sandpile models, in context
of the underlying spatial correlations of metastable patterns and scars. It is
argued that the relevance of Abelian symmetry may depend on whether the dynamic
rule is stochastic or deterministic, by means of the interaction of metastable
patterns and avalanche flow. Based on the new scaling relations, we conjecture
critical exponents for avalanche, which is confirmed reasonably well in
large-scale numerical simulations.Comment: 4 pages, 3 figures; published versio
DNA mismatch binding and antiproliferative activity of rhodium metalloinsertors
Deficiencies in mismatch repair (MMR) are associated with carcinogenesis. Rhodium metalloinsertors bind to DNA base mismatches with high specificity and inhibit cellular proliferation preferentially in MMR-deficient cells versus MMR-proficient cells. A family of chrysenequinone diimine complexes of rhodium with varying ancillary ligands that serve as DNA metalloinsertors has been synthesized, and both DNA mismatch binding affinities and antiproliferative activities against the human colorectal carcinoma cell lines HCT116N and HCT116O, an isogenic model system for MMR deficiency, have been determined. DNA photocleavage experiments reveal that all complexes bind to the mismatch sites with high specificities; DNA binding affinities to oligonucleotides containing single base CA and CC mismatches, obtained through photocleavage titration or competition, vary from 10^4 to 10^8 M^−1 for the series of complexes. Significantly, binding affinities are found to be inversely related to ancillary ligand size and directly related to differential inhibition of the HCT116 cell lines. The observed trend in binding affinity is consistent with the metalloinsertion mode where the complex binds from the minor groove with ejection of mismatched base pairs. The correlation between binding affinity and targeting of the MMR-deficient cell line suggests that rhodium metalloinsertors exert their selective biological effects on MMR-deficient cells through mismatch binding in vivo
Length Dependent Thermal Conductivity Measurements Yield Phonon Mean Free Path Spectra in Nanostructures
Thermal conductivity measurements over variable lengths on nanostructures
such as nanowires provide important information about the mean free paths
(MFPs) of the phonons responsible for heat conduction. However, nearly all of
these measurements have been interpreted using an average MFP even though
phonons in many crystals possess a broad MFP spectrum. Here, we present a
reconstruction method to obtain MFP spectra of nanostructures from
variable-length thermal conductivity measurements. Using this method, we
investigate recently reported length-dependent thermal conductivity
measurements on SiGe alloy nanowires and suspended graphene ribbons. We find
that the recent measurements on graphene imply that 70 % of the heat in
graphene is carried by phonons with MFPs longer than 1 micron
Floquet engineering of long-range p-wave superconductivity: Beyond the high-frequency limit
It has been shown that long-range {\it p}-wave superconductivity in a Kitaev
chain can be engineered via an ac field with a high frequency [Benito et al.,
Phys. Rev. B 90, 205127 (2014)]. For its experimental realization, however,
theoretical understanding of Floquet engineering with a broader range of
driving frequencies becomes important. In this work, focusing on the ac-driven
tunneling interactions of a Kitaev chain, we investigate effects from the
leading correction to the high-frequency limit on the emergent {\it p}-wave
superconductivity. Importantly, we find new engineered long-range {\it p}-wave
pairing interactions that can significantly alter the ones in the
high-frequency limit at long interaction ranges. We also find that the leading
correction additionally generates nearest-neighbor {\it p}-wave pairing
interactions with a renormalized pairing energy, long-range tunneling
interactions, and in particular multiple pairs of Floquet Majorana edge states
that are destroyed in the high- frequency limit.Comment: 13 pages, 8 figure
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