8,705 research outputs found
Giant circular dichroism of a molecule in a region of strong plasmon resonances between two neighboring gold nanocrystals
We report on giant circular dichroism (CD) of a molecule inserted into a
plasmonic hot spot. Naturally occurring molecules and biomolecules have
typically CD signals in the UV range, whereas plasmonic nanocrystals exhibit
strong plasmon resonances in the visible spectral interval. Therefore,
excitations of chiral molecules and plasmon resonances are typically
off-resonant. Nevertheless, we demonstrate theoretically that it is possible to
create strongly-enhanced molecular CD utilizing the plasmons. This task is
doubly challenging since it requires both creation and enhancement of the
molecular CD in the visible region. We demonstrate this effect within the model
which incorporates a chiral molecule and a plasmonic dimer. The associated
mechanism of plasmonic CD comes from the Coulomb interaction which is greatly
amplified in a plasmonic hot spot.Comment: Manuscript: 4+pages, 4 figures; Supplemental_Material: 10 pages, 7
figure
Cluster Mass Inference Method via Random Field Theory
Cluster extent and voxel intensity are two widely used statistics in neuroimaging inference. Cluster extent is sensitive to spatially extended signals while voxel intensity is better for intense but focal signals. In order to leverage strength from both statistics, several nonparametric permutation methods have been proposed to combine the two methods. Simulation studies have shown that of the different cluster permutation methods, the cluster mass statistic is generally the best. However, to date, there is no parametric cluster mass inference available. In this paper, we propose a cluster mass inference method based on random field theory (RFT). We develop this method for Gaussian images, extend it to Student’s t-statistic images and investigate its statistical properties via simulation studies and real data. Simulation results show that the method is valid under the null hypothesis and demonstrate that it can be more powerful than the cluster extent inference method. Further, analyses with a single-subject and a group fMRI dataset demonstrate better power than traditional cluster size inference, and good accuracy relative to a gold-standard permutation test
Diagnosis of single-subject and group fMRI data with SPMd
Except for purely nonparametric methods, statistical methods depend on assumptions about the distribution of the data studied. While these assumptions are easily checked for a single univariate dataset with diagnostic plots, in the massively univariate model used with functional MRI (fMRI) it is impractical to check with a massive number of plots. In previous work we have demonstrated how to diagnose model assumptions and lack-of-fit for single-subject fMRI models using a working assumption of independent errors; our work depended on images and time series of summary statistics that, when simultaneously viewed dynamically, identify problem scans and voxels. In this article we extend our previous work to account for temporal autocorrelation in single-subject models and show how analogous methods can be used on group models where multiple subjects are studied. We apply these methods to the single-subject Functional Image Analysis Contest (FIAC) data and find several anomalies, but none that appear to invalidate the results for that subject. With the group FIAC data we find one subject (and possibly two more) that demonstrate a different pattern of activity. None of our conclusions would be arrived at by simply looking at images of t statistics, demonstrating the importance of model assessment through exploration of the data and diagnosis of model assumptions. Hum Brain Mapp 27:442–451, 2006. © 2006 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50665/1/20253_ftp.pd
Constructions of Optimal and Near-Optimal Multiply Constant-Weight Codes
Multiply constant-weight codes (MCWCs) have been recently studied to improve
the reliability of certain physically unclonable function response. In this
paper, we give combinatorial constructions for MCWCs which yield several new
infinite families of optimal MCWCs. Furthermore, we demonstrate that the
Johnson type upper bounds of MCWCs are asymptotically tight for fixed weights
and distances. Finally, we provide bounds and constructions of two dimensional
MCWCs
Topological Excitation in Skyrme Theory
Based on the -mapping topological current theory and the decomposition
of gauge potential theory, we investigate knotted vortex lines and monopoles in
Skyrme theory and simply discuss the branch processes (splitting, merging and
intersection) during the evolution of the monopoles.Comment: 10 pages, 0 figure
Optical loss compensation in a bulk left-handed metamaterial by the gain in quantum dots
A bulk left-handed metamaterial with fishnet structure is investigated to
show the optical loss compensation via surface plasmon amplification, with the
assistance of a Gaussian gain in PbS quantum dots. The optical resonance
enhancement around 200 THz is confirmed by the retrieval method. By exploring
the dependence of propagation loss on the gain coefficient and metamaterial
thickness, we verify numerically that the left-handed response can endure a
large propagation thickness with ultralow and stable loss under a certain gain
coefficient.Comment: 6 pages with 4 figure
Quantum Non-Demolition Bell State Measurement and N-party GHZ State Preparation in Quantum Dot
By exploiting the fermionic qubit parity measurement, we present a scheme to
realize quantum non-demolition (QND) measurement of Bell-states and generate
n-party GHZ state in quantum dot. Compared with the original protocol, the
required electron transfer before and after parity measurement can be
nonadiabatic, which may speed up the operation speed and make the omitting of
spin-orbit interaction more reasonable. This may help us to construct CNOT gate
without highly precise control of coupling as the way of D. Gottesman and I. L.
Chuang.Comment: some modification to introduction and some details are adde
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