116 research outputs found
Construction of a polarization insensitive lens from a quasi-isotropic metamaterial slab
We propose to employ the quasiisotropic metamaterial (QIMM) slab to construct
a polarization insensitive lens, in which both E- and H-polarized waves exhibit
the same refocusing effect. For shallow incident angles, the QIMM slab will
provide some degree of refocusing in the same manner as an isotropic negative
index material. The refocusing effect allows us to introduce the ideas of
paraxial beam focusing and phase compensation by the QIMM slab. On the basis of
angular spectrum representation, a formalism describing paraxial beams
propagating through a QIMM slab is presented. Because of the negative phase
velocity in the QIMM slab, the inverse Gouy phase shift and the negative
Rayleigh length of paraxial Gaussian beam are proposed. We find that the phase
difference caused by the Gouy phase shift in vacuum can be compensated by that
caused by the inverse Gouy phase shift in the QIMM slab. If certain matching
conditions are satisfied, the intensity and phase distributions at object plane
can be completely reconstructed at image plane. Our simulation results show
that the superlensing effect with subwavelength image resolution could be
achieved in the form of a QIMM slab.Comment: 25 pages, 8 figure
Superluminal group velocity in an anisotropic metamaterial
Based on boundary condition and dispersion relation, the superluminal group
velocity in an anisotropic metamaterial (AMM) is investigated. The superluminal
propagation is induced by the hyperbolic dispersion relation associated with
the AMM. It is shown that a modulated Gaussian beam exhibits a superluminal
group velocity which depends on the choice of incident angles and optical axis
angles. The superluminal propagation does not violate the theory of special
relativity because the group velocity is the velocity of the peak of the
localized wave packet which does not carry information. It is proposed that a
triglycine sulfate (TGS) crystal can be designed and the superluminal group
velocity can be measured experimentally.Comment: 9 pages, 3 figure
A Conjugate Gradient Algorithm under Yuan-Wei-Lu Line Search Technique for Large-Scale Minimization Optimization Models
This paper gives a modified Hestenes and Stiefel (HS) conjugate gradient algorithm under the Yuan-Wei-Lu inexact line search technique for large-scale unconstrained optimization problems, where the proposed algorithm has the following properties: (1) the new search direction possesses not only a sufficient descent property but also a trust region feature; (2) the presented algorithm has global convergence for nonconvex functions; (3) the numerical experiment showed that the new algorithm is more effective than similar algorithms
IRX3 plays an important role in the pathogenesis of metabolic-associated fatty liver disease by regulating hepatic lipid metabolism
Metabolic-associated fatty liver disease (MAFLD) affects approximately a quarter of the global population. Identification of the key genes and pathways involved in hepatic lipid metabolism is of the utmost importance for the diagnosis, treatment, and prevention of MAFLD. In this study, differentially expressed genes were identified through whole-genome transcriptional analysis of liver tissue from MAFLD patients and healthy controls, and a series of lipid metabolism-related molecules and pathways were obtained through pathway analysis. Subsequently, we focused on Iroquois homeobox protein 3 (IRX3), one of 13 transcription factors that were screened from the 331 differentially expressed genes. The transcription factor IRX3 was significantly decreased in the liver tissue of patients with MAFLD when compared with healthy controls. Pearson’s correlation analysis showed that the expression levels of IRX3 in liver tissue were negatively correlated with serum total cholesterol, triglycerides, low-density lipoprotein cholesterol, and uric acid levels. The overexpression and interference of IRX3 induced the increased and decreased lipid droplet accumulation in vitro, respectively. Moreover, interference of IRX3 expression increased mitochondrial fragmentation and reduced the activity of the mitochondrial respiratory chain complex IV. In summary, the study demonstrated that IRX3 regulated hepatic lipid metabolism of MAFLD, and also revealed the effect of IRX3 on mitochondria might be an important mechanism by which IRX3 regulated hepatic lipid metabolism of MAFLD
AI for Archives: Using Facial Recognition to Enhance Metadata
The goal of this research project was to determine the most effective facial recognition applications that could be implemented into digital archive image collections from libraries, museums, and cultural heritage institutions. Computer scientists and librarians at Florida International University collaborated to conduct qualitative assessments of both face detection and face search using photographs from FIU’s digital collections. Specifically, the facial recognition platforms OpenCV, Face++, and Amazon AWS were analyzed. This project seeks to assist LYRASIS community members who wish to incorporate facial recognition and other artificial intelligence technology into their digital collections and repositories as a method to reduce research time and enhance their collections with more complete metadata
Focusing and phase compensation of paraxial beams by a left-handed material slab
On the basis of angular spectrum representation, a formalism describing
paraxial beams propagating through an isotropic left-handed material (LHM) slab
is presented. The treatment allows us to introduce the ideas of beam focusing
and phase compensation by LHM slab. Because of the negative refractive index of
LHM slab, the inverse Gouy phase shift and the negative Rayleigh length of
paraxial Gaussian beam are proposed. It is shown that the phase difference
caused by the Gouy phase shift in right-handed material (RHM) can be
compensated by that caused by the inverse Gouy phase shift in LHM. If certain
matching conditions are satisfied, the intensity and phase distributions at
object plane can be completely reconstructed at the image plane.Comment: 12 pages, 4 figure
- …