Non-ideal cloaking based on Fabry-Perot resonances in single-layer high-index dielectric shells

Cataloged from PDF version of article.Strong reduction of the scattering cross section is obtained for subwavelength dielectric and conducting cylinders without any magnetism for both TE and TM polarizations. The suggested approach is based on the use of Fabry-Perot type radial resonances, which can appear in single-layer, high-ε, isotropic, and homogeneous shells with the properly chosen parameters. Frequencies of the minima of the scattering cross section, which are associated with the cloaking, typically depend on whether TE or TM polarization is considered. In some cases, large-positive-ε and largenegative-e objects can be cloaked. In other cases, non-ideal multifrequency cloaking can be realized. ©2009 Optical Society of America

Spatial and spatial-frequency filtering using one-dimensional graded-index lattices with defects

Cataloged from PDF version of article.The potential of one-dimensional, periodic, graded-index, isotropic dielectric lattices with defects in multiband spatial and spatial-frequency filtering is studied. It is shown that both narrow- and wide-bandpass filters can be obtained at a proper choice of the number, location, and parameters of the defects placed inside the relatively thin slabs. The peculiarities of achieving multibandness for narrow- and wide-bandpass filters are discussed. Multiband narrow-bandpass filtering is closely related to the transmission features that are associated with Fabry-Perot resonators with semitransparent planar mirrors. Correspondingly, the observed transmission can be interpreted in terms of the equivalent parameters of such resonators. In particular, it is shown that the resonators filled with an ultralow-index medium can be mimicked, so that defect-mode angle-domain spectrum can be rarefied at large angles of incidence. The obtained results are also expected to be applicable for prediction of the angle-domain behavior of transmission in case of piecewise-homogeneous multilayers. (C) 2009 Elsevier B.V. All rights reserved

Cytoskeleton Structure in Mouse Sperm and Testes After 30 Days of Hindlimb Unloading and 12 Hours of Recovery

Background/Aims: Changes in the external mechanical field result in cytoskeleton reorganization and the formation of adaptive patterns in different types of cells, including somatic cells and sex cells. The aim of this research was to study the protein and mRNA content of cytoskeletal and sperm-specific genes in the sperm and testis cells of mice. Methods: Mice were subjected to 30 days of antiorthostatic suspension to simulate weightlessness, followed by 12 h of recovery, while receiving essential phospholipids at a dosage of 500 mg/kg/day (30HSE and 30HSE+12h groups) or a similar dosage of a placebo (30HS and 30HS+12h groups). Accordingly, reference groups (CE group and C group) were formed. The total number and the percentage of motile spermatozoa were calculated using a Makler chamber. To analyze the number of viable spermatozoa and the permeability of their membranes, eosin staining was used as well as Diff-Quick for a morphological evaluation. Relative protein and mRNA content was estimated in a western blot and quantitative PCR assay, respectively. Results: The relative protein expression levels of actin (beta and gamma) and two alpha-actinin isoforms (1 and 4) remained constant in the sperm of all study groups, except for the 30HS+12h group, where the alpha-actinin-4 level was 13% higher than in the reference group (p < 0.1). In the testis cells, the relative actin isoform content was equivalent to that in the spermatozoa. However, in the testis cells, the ACTN1 mRNA content was 17% higher in the 30HS group than in the C group (p < 0.05), and decreased after 12 h of recovery. In contrast, the ACTN4 mRNA content was 20% lower in the 30HS group than in the reference group (p < 0.05) and increased after the 12-h recovery period. At the same time, in the group administered the essential phospholipids, the relative ACTN1 and ACTN4 mRNA content did not differ from those of the reference group. The relative beta-tubulin content was similar in the reference C group and the reference CE group, which was administered the essential phospholipids. In the 30HS and 30HS+12h groups, the beta-tubulin content decreased by 19% and 22% (p < 0.05), respectively, and they also decreased in the groups administered the essential phospholipids (30HSE and 30HSE+12h groups, by 27% and 33%, respectively, p < 0.05). In the testis tissue, the relative tubulin content did not change in any of the experimental groups. At the same time, the relative mRNA content of the genes encoding the studied cytoskeletal proteins increased, which may indicate the protein content was regulated mainly at the translational level. Conclusion: The spermogram parameters and the content of the sperm-specific proteins and the associated mRNAs revealed a decrease in the number of mature spermatozoa in mice suspended under conditions of weightlessness. Moreover, the decrease was prevented by the administration of essential phospholipids

Multifrequency spatial filtering: A general property of two-dimensional photonic crystals

Spatial filtering, an analog of frequency-domain filtering that can be obtained in the incidence angle domain at a fixed frequency is studied in the transmission mode for slabs of two-dimensional rod-type photonic crystals. In the present paper, the emphasis is put on the demonstration of the possibility to obtain various regimes of spatial filtering, i.e., band-stop, band-pass, and low-pass filtering in different frequency ranges in one simple configuration. The operation is based on the use of several Floquet-Bloch modes with appropriate dispersion properties, so that such one or two co-existing mode(s) contribute to the forming of a proper filter characteristic within each specific frequency range. It is shown that high-efficiency transmission and steep switching between pass and stop bands can be obtained in the angle domain for wide ranges of variation of the problem parameters. In particular, by varying the rod-diameter-to-lattice-constant ratio, one attains lots of freedom in the engineering of spatial filters with desired transmission characteristics. © 2016 Elsevier B.V. All rights reserved

Search for Doubly-Charged Higgs Boson Production at HERA

A search for the single production of doubly-charged Higgs bosons H^{\pm \pm} in ep collisions is presented. The signal is searched for via the Higgs decays into a high mass pair of same charge leptons, one of them being an electron. The analysis uses up to 118 pb^{-1} of ep data collected by the H1 experiment at HERA. No evidence for doubly-charged Higgs production is observed and mass dependent upper limits are derived on the Yukawa couplings h_{el} of the Higgs boson to an electron-lepton pair. Assuming that the doubly-charged Higgs only decays into an electron and a muon via a coupling of electromagnetic strength h_{e \mu} = \sqrt{4 \pi \alpha_{em}} = 0.3, a lower limit of 141 GeV on the H^{\pm\pm} mass is obtained at the 95% confidence level. For a doubly-charged Higgs decaying only into an electron and a tau and a coupling h_{e\tau} = 0.3, masses below 112 GeV are ruled out.Comment: 15 pages, 3 figures, 1 tabl

Forward pi^0 Production and Associated Transverse Energy Flow in Deep-Inelastic Scattering at HERA

Deep-inelastic positron-proton interactions at low values of Bjorken-x down to x \approx 4.10^-5 which give rise to high transverse momentum pi^0 mesons are studied with the H1 experiment at HERA. The inclusive cross section for pi^0 mesons produced at small angles with respect to the proton remnant (the forward region) is presented as a function of the transverse momentum and energy of the pi^0 and of the four-momentum transfer Q^2 and Bjorken-x. Measurements are also presented of the transverse energy flow in events containing a forward pi^0 meson. Hadronic final state calculations based on QCD models implementing different parton evolution schemes are confronted with the data.Comment: 27 pages, 8 figures and 3 table

Searches at HERA for Squarks in R-Parity Violating Supersymmetry

A search for squarks in R-parity violating supersymmetry is performed in e^+p collisions at HERA at a centre of mass energy of 300 GeV, using H1 data corresponding to an integrated luminosity of 37 pb^(-1). The direct production of single squarks of any generation in positron-quark fusion via a Yukawa coupling lambda' is considered, taking into account R-parity violating and conserving decays of the squarks. No significant deviation from the Standard Model expectation is found. The results are interpreted in terms of constraints within the Minimal Supersymmetric Standard Model (MSSM), the constrained MSSM and the minimal Supergravity model, and their sensitivity to the model parameters is studied in detail. For a Yukawa coupling of electromagnetic strength, squark masses below 260 GeV are excluded at 95% confidence level in a large part of the parameter space. For a 100 times smaller coupling strength masses up to 182 GeV are excluded.Comment: 32 pages, 14 figures, 3 table