Oscillation criteria for nonlinear delay differential equations of second order

We prove oscillation theorems for the nonlinear delay differential equation $\left( \left\vert y^{\prime }(t)\right\vert ^{\alpha -2}y^{\prime}(t)\right) ^{\prime }+q(t)\left\vert y(\tau (t))\right\vert ^{\beta-2}y(\tau (t))=0, t\geq t_{\ast }>0,$ where $\beta >1,$ $\alpha >1,$ $q(t)\geq 0$ and locally integrable on $[t_{\ast },\infty ),$ $\tau (t)$ is a continuous function satisfiying $0<\tau (t)\leq t$ and lim$_{t\rightarrow \infty }\tau (t)=\infty .$ The results obtained essentially improve the known results in the literature and can be applied to linear and half-linear delay type differential equations

Concentration and localization of zinc during seed development and germination in wheat

In a field experiment, the effect of foliar Zn applications on the concentration of Zn in seeds of a bread wheat cultivar (Triticum aestivum L. cv. Balatilla) was studied during different stages of seed development. In addition, a staining method using dithizone (DTZ: diphenyl thiocarbazone) was applied to (1) study the localization of Zn in seeds, (2) follow the remobilization of Zn during germination, and (3) develop a rapid visual Zn screening method for seed and flour samples. In all seed development stages, foliar Zn treatments were effective in increasing seed Zn concentration. The highest Zn concentration in the seeds was found in the first stage of seed development (around the early milk stage); after this, seed Zn concentration gradually decreased until maturity. When reacting with Zn, DTZ forms a redcolored complex. The DTZ staining of seed samples revealed that Zn is predominantly located in the embryo and aleurone parts of the seeds. After 36 h of germination, the coleoptile and roots that emerged from seeds showed very intensive red color formation and had Zn concentrations up to 200 mg kg1, indicating a substantial remobilization of Zn from seed pools into the developing roots (radicle) and coleoptile. The DTZ staining method seems to be useful in ranking flour samples for their Zn concentrations. There was a close relationship between the seed Zn concentrations and spectral absorbance of the methanol extracts of the flour samples stained with DTZ. The results suggest that (1) accumulation of Zn in seeds is particularly high during early seed development, (2) Zn is concentrated in the embryo and aleurone parts, and (3) the DTZ staining method can be used as a rapid, semiquantitative method to estimate Zn concentrations of flour and seed samples and to screen genotypes for their Zn concentrations in seeds

Proof of principle for a molecular 1:2 demultiplexer to function as an autonomously switching theranostic device

Cataloged from PDF version of article.Guided by the digital design concepts, we synthesized a two-module molecular demultiplexer (DEMUX) where the output is switched between emission at near IR, and cytotoxic singlet oxygen, with light at 625 nm as the input (I), and acid as the control (c). In the neutral form, the compound fluoresces brightly under excitation at 625 nm, however, acid addition moves the absorption bands of the two modules in opposite directions, resulting in an effective reversal of excitation energy transfer direction, with a concomitant upsurge of singlet oxygen generation and decrease in emission intensity

Nitrogen and sulfur deprivation differentiate lipid accumulation targets of Chlamydomonas reinhardtii

Cataloged from PDF version of article.Nitrogen (N) and sulfur (S) have inter-related and distinct impacts on microalgal metabolism; with N starvation having previously been reported to induce elevated levels of the biodiesel feedstock material triacylglycerol (TAG), while S deprivation is extensively studied for its effects on biohydrogen production in microalgae.1,2 We have previously demonstrated that N- and S-starved cells of Chlamydomonas reinhardtii display different metabolic trends, suggesting that different response mechanisms exist to compensate for the absence of those two elements.3 We used C. reinhardtii CC-124 mt(-) and CC-125 mt(+) strains to test possible metabolic changes related to TAG accumulation in response to N and S deprivation, considering that gamete differentiation in this organism is mainly regulated by N.4 Our findings contribute to the understanding of microalgal response to element deprivation and potential use of element deprivation for biodiesel feedstock production using microalgae, but much remains to be elucidated on the precise contribution of both N and S starvation on microalgal metabolism. © 2012 Landes Bioscience

Multichannel optical diode with unidirectional diffraction relevant total transmission

Cataloged from PDF version of article.We will show that broadband unidirectional optical transmission with a total transmission maximum inside the band can be obtained for linearly polarized incident waves in the nonsymmetric photonic crystal gratings made of isotropic linear materials at a fixed nonzero or zero angle of incidence. Being based on the merging of diffraction and dispersion effects, the basic physical mechanism studied exploits the transmission channels associated with higher orders, for which asymmetry in the coupling conditions at the two grating interfaces appears when spatial inversion symmetry is broken. Total transmission in one direction and zero transmission in the opposite direction can be obtained due to hybridization of Fabry-Perot type resonances with a diffraction anomaly that yields a diode-like operation regime. Single-beam deflection and two-beam splitting can be obtained, for which transmission can be (nearly) total, if the corrugated side is illuminated. In contrast to the previous studies, it is also shown that unidirectional transmission can appear only at a fixed frequency and only due to diffractions, when total transmission occurs at the noncorrugated-side illumination, being in agreement with the Lorentz Lemma. (c) 2012 Optical Society of America

Near-field light localization using subwavelength apertures incorporated with metamaterials

Cataloged from PDF version of article.We report strong near-field electromagnetic localization by using subwavelength apertures and metamaterials that operate at microwave frequencies. We designed split ring resonators with distinct configurations in order to obtain extraordinary transmission results. Furthermore, we analyzed the field localization and focusing characteristics of the transmitted evanescent waves. The employed metamaterial configurations yielded an improvement on the transmission efficiency on the order of 27 dB and 50 dB for the deep subwavelength apertures. The metamaterial loaded apertures are considered as a total system that offered spot size conversion ratios as high as 7.12 and 9.11 for the corresponding metamaterial configurations. The proposed system is shown to intensify the electric fields of the source located in the near-field. It also narrows down the electromagnetic waves such that a full width at half maximum value of λ/29 is obtained. © 2012 Elsevier B.V. All rights reserved

Simultaneously opening transmission channels with negative and positive phase velocities for the stacked subwavelength apertures in fishnet metamaterials with hybrid unit lattices

Cataloged from PDF version of article.Hybridization of the unit lattice along the propagation direction was demonstrated to produce a negative-phase-velocity transmission band in the absence of the contributions from the higher diffraction orders for a stacked metallic fishnet grid with subwavelength apertures. This extraordinary transmission band is governed by the stacked resonators. The hybridized unit lattice configurations are not just slight modifications of the configurations with homogenous unit lattices. The volumetric proportions of different dielectric media are a key factor in the partitioned unit lattice for the estimation of the stacking and coupling effects between the resonators. The contribution of the coupling mechanisms enhances the transmission results almost by the same factor for the investigated lattice separations along the propagation direction in hybrid unit cells while the densely stacked resonators yield much higher transmission results, both around the regarding extraordinary transmission band that is associated with the negative phase velocity. A positive-phase-velocity transmission band was also exhibited by the hybridized unit lattice configuration when combined with a cavity resonator. Experimental transmission results of the hybrid configuration supported the theoretical predictions. The hybrid configurations are scalable to the near-infrared regime. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.JNP.6.061608

Spatial filtering using dielectric photonic crystals at beam-type excitation

Cataloged from PDF version of article.Spatial filtering is demonstrated at beam-type excitations by utilizing finite thickness slabs of two-dimensional dielectric photonic crystals (PCs) showing exotic Fabry-Perot resonances that are preserved over a wide range of variation of the incidence angle. Bandstop and dual-bandpass filtering effects are illustrated theoretically and the corresponding filters are validated in the microwave experiments by using square-lattice PCs. It is shown that the basic transmission features that were observed earlier for a plane-wave illumination are also recognizable at beam-type excitations. The proposed spatial filtering mechanism exhibits directional beaming. The desired widths and the locations of the passbands and stopbands are attainable in the angle domain with a proper choice of the operating frequency for the given excitation characteristics. c 2010 American Institute of Physics. [doi:10.1063/1.3498810

Validation of electromagnetic field enhancement in near-infrared through Sierpinski fractal nanoantennas

Cataloged from PDF version of article.We introduced fractal geometry to the conventional bowtie antennas. We experimentally and numerically showed that the resonance of the bowtie antennas goes to longer wavelengths, after each fractalization step, which is considered a tool to miniaturize the main bowtie structure. We also showed that the fractal geometry provides multiple hot spots on the surface, and it can be used as an efficient SERS substrate. (C)2014 Optical Society of America