122 research outputs found
Engineered Optical Nonlocality in Nanostructured Metamaterials
We analyze dispersion properties of metal-dielectric nanostructured
metamaterials. We demonstrate that, in a sharp contrast to the results for the
corresponding effective medium, the structure demonstrates strong optical
nonlocality due to excitation of surface plasmon polaritons that can be
engineered by changing a ratio between the thicknesses of metal and dielectric
layers. In particular, this nonlocality allows the existence of an additional
extraordinary wave that manifests itself in the splitting of the TM-polarized
beam scattered at an air-metamaterial interface
Scattering Suppression from Arbitrary Objects in Spatially-Dispersive Layered Metamaterials
Concealing objects by making them invisible to an external electromagnetic
probe is coined by the term cloaking. Cloaking devices, having numerous
potential applications, are still face challenges in realization, especially in
the visible spectral range. In particular, inherent losses and extreme
parameters of metamaterials required for the cloak implementation are the
limiting factors. Here, we numerically demonstrate nearly perfect suppression
of scattering from arbitrary shaped objects in spatially dispersive
metamaterial acting as an alignment-free concealing cover. We consider a
realization of a metamaterial as a metal-dielectric multilayer and demonstrate
suppression of scattering from an arbitrary object in forward and backward
directions with perfectly preserved wavefronts and less than 10% absolute
intensity change, despite spatial dispersion effects present in the composite
metamaterial. Beyond the usual scattering suppression applications, the
proposed configuration may serve as a simple realisation of scattering-free
detectors and sensors
Nonlocal effective parameters of multilayered metal-dielectric metamaterials
We consider multilayered metal-dielectric metamaterials composed of alternating nanolayers of two types and calculate the components of their effective dielectric permittivity tensors as functions of both frequency and wave vector. We demonstrate that such structures can be described as strongly nonlocal uniaxial effective media, and we analyze how the nonlocal permittivity tensor components are related to other manifestations of strong spatial dispersion in such structures, and how the resonance of permittivity depends on the propagation direction
Retrieval of Effective Parameters of Subwavelength Periodic Photonic Structures
We revisit the standard Nicolson–Ross–Weir method of effective permittivity and permeability restoration of photonic structures for the case of subwavelength metal-dielectric multilayers. We show that the direct application of the standard method yields a false zero-epsilon point and an associated spurious permeability resonance. We show how this artifact can be worked around by the use of the cycle shift operator to the periodic multilayer in question
Nonlocal effective medium model for multilayered metal-dielectric metamaterials
We study layered metal-dielectric structures, which can be considered as a simple example of nanostructured metamaterials. We analyze the dispersion properties of such structures and demonstrate that they show strong optical nonlocality due to excitatio
Effect of wood structure geometry during firebrand generation in laboratory scale and semi-field experiments
As the set of experiments result, statistically substantiated data were obtained on the laws of ignition of a model angular structure under conditions of a point source of heat exposure. The use of IR diagnostics made it possible to control the thermal picture in the experimental area, as well as to capture areas of the highest and lowest heating. In the Large Aerosol Chamber of IAO SB RAS, preliminary experiments were carried out on a “firebrand shower” model exposure, which is naturally occurring firebrands (flaming or glowing embers) with some types of construction materials (chipboards). The exposure of the samples to firebrands stream was provided using a firebrand generator of own original design. It was experimentally confirmed that particle size plays a significant role in the ignition of a building structure. If the characteristic particle size, which can be defined as the ratio of its volume to the surface area in contact with the wood, is less than a certain characteristic value, then the ignition mode with a sharp temperature maximum near the phase interface is not fulfilled. This can be explained by the prevailing heat removal into the external environment in comparison with the amount of heat coming from a heat gun and resulting from chemical reactions
Time- and dose dependent actions of cardiotonic steroids on transcriptome and intracellular content of Na+ and K+: a comparative analysis
Recent studies demonstrated that in addition to Na+,K+-ATPase inhibition cardiotonic steroids (CTSs) affect diverse intracellular signaling pathways. This study examines the relative impact of [Na+]i/[K+]i-mediated and -independent signaling in transcriptomic changes triggered by the endogenous CTSs ouabain and marinobufagenin (MBG) in human umbilical vein endothelial cells (HUVEC). We noted that prolongation of incubation increased the apparent affinity for ouabain estimated by the loss of [K+]i and gain of [Na+]i. Six hour exposure of HUVEC to 100 and 3,000 nM ouabain resulted in elevation of the [Na+]i/[K+]i ratio by ~15 and 80-fold and differential expression of 258 and 2185 transcripts, respectively. Neither [Na+]i/[K+]i ratio nor transcriptome were affected by 6-h incubation with 30 nM ouabain. The 96-h incubation with 3 nM ouabain or 30 nM MBG elevated the [Na+]i/[K+]i ratio by ~14 and 3-fold and led to differential expression of 880 and 484 transcripts, respectively. These parameters were not changed after 96-h incubation with 1 nM ouabain or 10 nM MBG. Thus, our results demonstrate that elevation of the [Na+]i/[K+]i ratio is an obligatory step for transcriptomic changes evoked by CTS in HUVEC. The molecular origin of upstream [Na+]i/[K+]i sensors involved in transcription regulation should be identified in forthcoming studies
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