Properties of Surface Plasmon Polaritons Excited by Radially Polarized Sinh Gaussian Beams

Properties of surface plasmon polaritons (SPPs) excited by radially polarized sinh Gaussian beams with high-numerical-aperture system is investigated theoretically based on vector diffraction theory. It is observed that by properly tuning the beam waist size (w ₀ ) and beam order (m) of the incident sinh Gaussian beam, one can achieve higher confinement in axial and lateral size of the generated plasmonic focal spot. We observed that sinh Gaussian beam of larger w ₀ and m results in generation of highly confined plasmonic focal spot.     

Enhancement of Emission Efficiency of Deep-Ultraviolet AlGaN Quantum Wells Through Surface Plasmon Coupling with an Al Nanograting Structure

The enhancement of the internal quantum efficiency (IQE) of deep-ultraviolet Al _x Ga_1-x N/Al _y Ga_1-y N (x < y) quantum wells (QWs) by fabricating one-dimensional Al nanogratings on a QW structure for inducing surface plasmon (SP) coupling is demonstrated. Through temperature-dependent photoluminescence (PL) measurement, the enhancements of IQE in different emission polarizations are illustrated. Due to the small difference in energy band level between the heavy/light hole and split-off valence bands, the IQEs of the transverse electric- (TE-) and transverse magnetic- (TM-) polarized emissions are about the same. When emission polarization is perpendicular to Al-grating ridges, the SP resonance mode for coupling with the QWs is dominated by localized surface plasmon (LSP). When emission polarization is parallel with Al-grating ridges, the coupled SP resonance mode may mix LSP and SP polariton. In this polarization, LSP can be excited because of the width fluctuation of a grating ridge. When the excitation laser polarization is perpendicular to Al-grating ridges, the strong LSP resonance at the excitation laser wavelength leads to stronger excitation and hence higher IQE levels.     

Better tolerance to water deficit in doubled diploid ‘Carrizo citrange’ compared to diploid seedlings is associated with more limited water consumption

Tolerance to water deficit in diploid (2x) and doubled diploid (4x) ‘Carrizo citrange’ (Citrus sinensis [L.] Osbeck × Poncirus trifoliata [L.] Raf) was investigated. Water deficit was applied for 4 weeks. Physiological parameters, including stomatal conductance (g _s), photosynthesis (A), transpiration (E), leaf and soil water potentials (Ψ _leaf; Ψ _soil), and pot water loss, were monitored throughout the stress. Moreover, ABA, H₂O₂ contents, and the expression of genes involved in ABA biosynthesis (NCED3), regulation of abscisic acid signaling (ABI1), and coding for a catalase enzyme (CAT2) known to favor H₂O₂ scavenging were monitored. During the experiment g _s, A, and E values were most of the time higher in 2x compared to 4x. During the water deficit period, pot water loss decreased faster in 2x compared to 4x, leading to a faster decrease in all physiological parameters in 2x. The higher sensitivity of 2x compared to 4x was correlated with more numerous thinner roots, higher leaf ABA and H₂O₂ contents, and with the lower leaf water potential. ABI1 and NCED3 expression was not strictly correlated with the ABA content. However, the higher CAT2 expression in 4x was correlated with the lower leaf H₂O₂ contents. Therefore, the better tolerance observed in 4x ‘Carrizo citrange’ compared to 2x was associated with more limited water consumption and better and H₂O₂ scavenging.     

Chaotic Dynamics of Neuromuscular System Parameters and the Problems of the Evolution of Complexity

The evolution rate v(t) varies among diverse biosystems, but a general theory can be formulated when the dynamics of the biosystem stater x = x(t) = (x₁, x₂, x _m ) ^T is considered in the m-dimensional space of states. A mathematical approach is proposed for evaluating such processes and describes the processes in terms of particular chaos of the statistical distribution functions f(x). In the case of complex multicomponent systems with a high dimension number m (m ?1) of the phase space of states, we propose using pairwise comparison matrices of samples x(t) when homeostasis is constant and calculating the parameters of quasiattractors. The Glensdorff–Prigogine thermodynamic approach to estimating evolution is inefficient in assessing the third-type systems, while it is applicable and the Prigogine theorem works at the level of molecular systems. Alterations in the state of the human neuromuscular system were found to lead to chaotic changes in the statistical functions f(x) in tremor recording samples, while quasiattractor parameters demonstrate a certain regularity.     

Highly Sensitive Biochemical Sensor Based on Two-Layer Dielectric Loaded Plasmonic Microring Resonator

In this paper, we propose and design a highly sensitive optical biochemical sensor based on two-layer dielectric loaded surface plasmon polariton waveguide (TDLSPPW)-based microring resonator (MRR). By optimizing the structure parameters, the propagation length of the proposed waveguide is ~126 μm, which is about 3 times of that of the polymer dielectric loaded surface plasmon polariton waveguide (DLSPPW) reported. It is demonstrated that the TDLSPPW-based MRR is operated at the under-coupling state, along with the quality factor (Q) of 541.2 and extinction ratio (ER) of 12.2 dB. Moreover, the Q and ER are much more sensitive to the structure parameters of the waveguide, including the waveguide width w, total thickness t, and coupling gap W _gap, compared to the low refractive index (RI) layer thickness t ₂. The simulation results on the biochemical RI sensing show that the sensitivities of 408.7 and 276.4 nm/RIU for glucose concentration in urine and chemical gases can be achieved, respectively. It is believed that the proposed sensor has potential applications in photonic-integrated biochemical sensing.     

Coupling Efficiency of Surface Plasmon Polaritons for 1D Plasmonic Gratings: Role of Under- and Over-Milling

This paper reports the successful excitation of surface plasmon polaritons (SPPs) through 1D metallic grating on higher refractive index GaP substrate. Coupling efficiency (η) of a free-space transverse-magnetic (TM) plane-wave mode into a SPP mode is crucial for many plasmonic devices. This η predominantly depends on the fabrication (milling) parameters and the factors (under- and over-milling) affecting the η is investigated experimentally and numerically. First of all, η is estimated by measuring the transmission spectra obtained through the plasmonic grating structures by varying the slit width (a) for a fixed period (Λ) and the thickness (t) of the gold (Au) film in which the grating is formed. The wave vector of the incident light is tuned to match the wave vector of the SPP, to get maximum η. For an optimum Au film thickness, a slit width of half of the periodicity of 770 nm in the grating device yields a maximum η. Such grating devices support only a fundamental plasmonic mode because the profile/shape of the slit in the grating device is more like a sinusoidal nature. Furthermore, such grating offers intermediate scattering to the incident light and the SPP as well which in-truns couple more incident energy to the SPPs. Moreover, over-milling results in decreased η where the crystalline plane of the substrate is disturbed. Finite element method (FEM) in COMSOL modeling is used to understand the underlying physics. This study is very useful for the development of the device application in real word.     

A Study of Metal@Graphene Core–Shell Spherical Nano-Geometry to Enhance the SPR Tunability: Influence of Graphene Monolayer Shell Thickness

Graphene, new generation advance material of two dimensional hexagonal lattice having extraordinary optical signatures, is used as coating material to enhance the surface plasmon resonance (SPR) effect of core@shell metal nanospheres. In a core@shell nanosphere, we have chosen metal as a core and graphene monolayer (GML) as a shell. We have analysed optical signature of coated and non-coated nanospheres in terms of extinction efficiency (Q _ext) and tunabilty of surface plasmon resonances using electrostatic model, where particle size is much smaller than the wavelength of incident light. We analysed this model over different metals (silver, gold and aluminium) core, coated with different thickness of GML (d?=?0.1 to 0.5 nm). These core@shell nanospheres are embedded in refractive index media of air (n _em?=?1), SiO₂ (n _em?=?1.47) and TiO₂ (n _em?=?2.79). The Q _ext has been calculated by varying both the core radii as well as the GML shell thickness. Graphene-coated metal nanosphere exhibits SPRs that have wide range tunability from 300 to 1500 nm. In the presenting work, we also analysed that extinction efficiency for metal@GML is higher in TiO₂ than others. The optimum value of GML shell thickness is 0.4 nm for TiO₂, the magnitude of extinction efficiency is maximum for the optimum thickness. The tunability of these plasmonic resonances is highly dependent on the core@shell material, thickness of Graphene shell and surrounding environment while non-coated metal nano-spheres do not show appropriate SPR tunability.     

A Polarization Filter Based on a Novel Photonic Crystal Fiber with a Gold-Coated Air Hole by Using Surface Plasmon Resonance

A novel design of a polarization filter based on photonic crystal fiber (PCF) is proposed in this paper. With the introduction of a gold-coated air hole, the resonance strength is much stronger in y-polarized direction than in x-polarized direction at some particular wavelengths, which is due to the metal surface plasmon effects. At the wavelength of 1.31 μm, the loss of y-polarized mode is 2138.34 dB/cm while the loss is very low in x polarization. Furthermore, the loss peak can be flexibly adjusted from the wavelength of 1.26 to 1.56 μm by changing the thickness of a gold layer, and the loss in y polarization can be kept above 1200 dB/cm. The significant loss in y polarization makes this PCF a good candidate for developing a polarization filter with high performance.     

Theoretical Studies of Tunable Localized Surface Plasmon Resonance of Gold-Dielectric Multilayered Nanoshells

Tunable properties of localized surface plasmon resonances (LSPR) of gold-dielectric multilayered nanoshells are studied by quasi-static theory and plasmon hybridization theory. Multilayered nanoshells with the gold core and nanoshell separated by a spacer layer exhibit strong coupling between the core and nanoshell plasmon resonance modes. It is found that the absorption spectra characteristics of LSPR are sensitive to multiple parameters including the surrounding medium refractive index, the dielectric constant of spacer layer, the radius of inner core gold sphere, outer shell layer thickness, and their coupling strength. The results show that LSPR is mainly influenced by the ratio of spacer layer dielectric constant ε ₂ to surrounding medium dielectric constant ε ₄. Absorption spectrum of \(\left |\omega _{-}^{+}\right \rangle \) mode is red-shifted with increasing core radius when ε ₂ > ε ₄. It is surprising to find that LSPR is blue-shifted with increasing core radius when ε ₂ < ε ₄, and no shift when ε ₂ = ε ₄. These interesting contrary shifts of \(\left |\omega _{-}^{+}\right \rangle \) mode with different ratios ε ₂/ε ₄ are well analysed with plasmon hybridization theory and the distributions of induced charges interaction between the inner core and outer shell. In addition, for the sake of clarity, the distributions of electric filed intensity at their plasmon resonance wavelengths are also calculated. This work may provide an alternative approach to analyse property of the core-shell nanoshell particles based on plasmon hybridization theory and the induced charge interaction.     

Sodium Conductance Activation without Inactivation in Pronase-perfused Axons

A controversy of long standing in membrane electrophysio-logy is whether the sodium ion current (I_Na) and potassium ion current (I_K) pass through the membrane in separate channels, or through a single set of channels which conduct first I_Na and then I_K. In support of the latter hypothesis it has been noted that the sodium conductance (g_Na) decline, called inactivation, proceeds with about the same time course as the potassium conductance (g_K) increase. This could mean that Na⁺ selective channels are being converted into K⁺ selective channels. The hypothesis is especially interesting because of the possibility that the carrier postulated in active transport is convertible from Na⁺ to K⁺ selectivity¹. An explicit statement of the single channel hypothesis and the means for disproving it were given by Mullins². Because a single channel could not simultaneously conduct I_Na and I_K, disproof requires that membrane conductance (g_m) be made somehow to exceed the maximum value of g_Na or g_K. We report here that inactivation of g_Na can be destroyed fairly selectively by the action from inside the axon of the unspecific proteolytic enzymes of pronase. In many cases g_m after pronase treatment is greater than maximum g_K before treatment, making untenable the single channel hypothesis.     

Plasmonic Broadband Polarization Splitter Based on Dual-Core Photonic Crystal Fiber with Elliptical Metallic Nanowires

We design two kinds of plasmonic broadband polarization splitters based on dual-core photonic crystal fiber (DC-PCF) with elliptical Au or Ag nanowire in this paper. It is analyzed for the polarization independent characterestics of the designed DC-PCF by the finite element method (FEM). In order to excite the surface plasmon resonance (SPR), the metal Au and Ag are filled into elliptical central air hole. The resonance coupling between the fourth- or fifth-order surface plasmon modes (SPMs) and core-guided modes (CGMs) are founded by this numerical simulation. The device lengths of the designed splitters with Au nanowire are 2937 and 827 μm at the wavelength of 1.31 and 1.55 μm, respectively. As the extinction ratios are better than ?20 dB, its bandwidths are better than 94 and 103 nm. For the designed Ag nanowire splitter, the device lengths are 3066 or 809 μm at 1.31 or 1.55 μm, respectively. The bandwidths with the extinction ratio better than ?20 dB are 66 and 104 nm, respectively.     

Mechanism for phenanthridines synthesis by nitrogenation of 2-acetylbiphenyls in acidic solution: a DFT study

The mechanism of phenanthridines synthesis from the nitrogenation of 2-acetylbiphenyls (1) by TMSN₃ in TFA has been studied by DFT calculations. Results at the B3LYP/6-311G(d) level showed that: 1) reaction of TMSN₃/HN₃ with the protonated form of 1 (1H⁺), which generates the key intermediate C ^x+ by removal of TMSOH/H₂O, is the rate determining step, and TMSN₃ as the nitrogen source is certainly preferred over HN₃. 2) from C ^x+, the two pathways leading to 2 ^x H⁺ and 3 ^x H⁺ are both thermodynamically and kinetically feasible and competitive to each other. 3) The high barriers of the reverse reactions suggest that the ratio of the final products 2 ^x :3 ^x is determined by the branching ratio of reaction rates of C ^x+ to intermediates D ^x+ in pass_I and E ^x+ in pass_II.

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Graphical Abstract DFT results indicate that the replacement of -OH by -N₃ which generates C ^x+ controls the consumption rate of 1 ^x H⁺, and the ratio of C ^x+ transforms to D ^x+ and C ^x+ transforms to E ^x+ (k:k') determines the final ratio of products 2x:3x.

     

A <Emphasis Type="Italic">pqr2</Emphasis> mutant encodes a defective polyamine transporter and is negatively affected by ABA for paraquat resistance in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Despite the paraquat-resistant mutants that have been reported in plants, this study identified a novel A. thaliana mutant (pqr2) from an XVE inducible activation library based on its resistance to 2 μM paraquat. The pqr2 mutant exhibited a termination mutation in the exon of AT1G31830/PAR1/PQR2, encoded a polyamine uptake transporter AtPUT2/PAR1/PQR2. The PQR2 mutation could largely reduce superoxide accumulation and cell death in the pqr2 plants under paraquat treatment. Moreover, compared with wild type, the pqr2 mutant exhibited much reduced tolerance to putrescine, a classic polyamine compound, which confirmed that PQR2 encoded a defective polyamine transporter. Notably, co-treated with ABA and paraquat, both pqr2 mutant and wild type exhibited a lethal phenotype from seed germination, but the wild type like pqr2 mutant, could remain paraquat-resistance while co-treated with high dosage of Na₂WO₄, an ABA synthesis inhibitor. Gene expression analysis suggested that ABA signaling should widely regulate paraquat-responsive genes distinctively in wild type and pqr2 mutant. Hence, this study has for the first time reported about ABA negative effect on paraquat-resistance in A. thaliana, providing insight into the ABA signaling involved in the oxidative stress responses induced by paraquat in plants.     

Optimization on Plasmonic Lenses Based on Generation Efficiency of Surface Plasmon Polaritons at Metallic Nanoslit

The generation efficiency of surface plasmon polaritons at metallic nanoslit is theoretically analyzed, and a novel plasmonic lens with two semiannular nanoslits is proposed in this paper. Based on the analysis results, the focusing performance of the proposal is optimized with a maximum field intensity enhancement factor of 7.69 and the full width at half maximum is 132 nm (~0.2λ _i), far beyond theoretical diffraction limit. Meanwhile, some other classical plasmonic lenses are also optimized through improving generation efficiency of surface plasmon polaritons at nanoslit and the focusing performances are consequently greatly enhanced.     

Testing the cost of reproduction with the rotifer <Emphasis Type="Italic">Brachionus</Emphasis><Emphasis Type="Italic">patulus</Emphasis> at different pH levels

In the present work, we tested the hypothesis that the cost of reproduction was evident under stressful conditions with the rotifer Brachionus patulus at different pH levels (5–10 at 1 unit intervals). We used sublethal pH levels (pH 5, 9, and 10) to simulate stressful conditions. We analyzed the correlations between age-specific fecundity (m ₁, m ₂, m ₃, …) versus future survival (l _x + 1, l _x + 2, l _x + 3, … for the entire lifespan) (survival costs) and future expectation of reproduction (\( V_{ 1}^{*} , \, V_{ 2}^{*} , \, V_{ 3}^{*} , \ldots \) for the entire lifespan) (reproductive costs), using the data obtained from life table demographic studies of B. patulus under stressful and favorable (pH 6, 7, and 8) pH levels. The results showed that significant negative correlations were observed between age-specific fecundity and future survival and future expectation of reproduction at all tested pH levels, indicating that costs of reproduction exist in the rotifer B. patulus under stressful and favorable pH conditions. However, the percentage of statistically significant negative correlations from total correlations of survival and reproductive costs differed greatly, depending on the tested pH conditions. The percentage of significant negative correlation of reproductive costs is significantly higher under stressful pH conditions (pH 5, 9, and 10) than favorable pH conditions (pH 6, 7, and 8). For survival costs, the same trends are also observed, suggesting that the costs of reproduction were more obvious under stressful pH than favorable pH.     

Theoretical Study of Sensitivity and Localized Surface Plasmon Resonance of Ag-Dielectric Core-Shell Multi-layered Nanosphere

Localized surface plasmon resonances (LSPRs) of Ag-dielectric-Ag multi-layered nanoshell are studied by quasi-static approximation and plasmon hybridization theory. Absorption properties of multi-layered nanoshell with the silver core and nanoshell separated by a dielectric layer exhibit strong coupling between the core and nanoshell. The result shows absorption spectrum of LSPRS is influenced by the refractive index of surrounding medium, the dielectric constant of middle dielectric layer, the thickness of inner core radius and outer shell layer. LSPR shift of the longest wavelength \(\left |\omega _{-}^{-}\right >\) is red-shifted with increasing the inner core radius. It is interesting to find that longer wavelength \(\left |\omega _{-}^{+}\right >\) mode is mainly effected by the ratio constant of the surrounding medium refractive index ε ₄ to the middle layer dielectric constant ε ₂. \(\left |\omega _{-}^{+}\right >\) mode takes place a blue-shift with increasing inner core radius when ε ₂ > ε ₄, a red-shift when ε ₂ < ε ₄, and no-shifting when ε ₂ = ε ₄. However, the influence of dielectric layer radius to \(\left |\omega _{-}^{+}\right >\) mode shows the different property as that of increasing the inner core radius. The underlying mechanisms are analyzed with the plasmon hybridization theory and the distribution of induced charge interaction between the inner core and outer shell. In addition, the influence of core radius, middle dielectric layer radius and outer shell radius to sensitivity of Ag-dielectric-Ag multi-layered nanoshell are also reported, a higher sensitivity could be gotten by adjusting geometrical parameters. Our theoretical study could give an easy way to analyze properties of the core-shell nanosphere based on plasmon hybridization theory and the induced charge interaction, and usefully broaden the applications in nano-optics.     

Mapping of novel salt tolerance QTL in an Excalibur × Kukri doubled haploid wheat population

Key message

Novel QTL for salinity tolerance traits have been detected using non-destructive and destructive phenotyping in bread wheat and were shown to be linked to improvements in yield in saline fields.

Abstract

Soil salinity is a major limitation to cereal production. Breeding new salt-tolerant cultivars has the potential to improve cereal crop yields. In this study, a doubled haploid bread wheat mapping population, derived from the bi-parental cross of Excalibur?×?Kukri, was grown in a glasshouse under control and salinity treatments and evaluated using high-throughput non-destructive imaging technology. Quantitative trait locus (QTL) analysis of this population detected multiple QTL under salt and control treatments. Of these, six QTL were detected in the salt treatment including one for maintenance of shoot growth under salinity (QG_(1–5).asl-7A), one for leaf Na⁺ exclusion (QNa.asl-7A) and four for leaf K⁺ accumulation (QK.asl-2B.1, QK.asl-2B.2, QK.asl-5A and QK:Na.asl-6A). The beneficial allele for QG_(1–5).asl-7A (the maintenance of shoot growth under salinity) was present in six out of 44 mainly Australian bread and durum wheat cultivars. The effect of each QTL allele on grain yield was tested in a range of salinity concentrations at three field sites across 2 years. In six out of nine field trials with different levels of salinity stress, lines with alleles for Na⁺ exclusion and/or K⁺ maintenance at three QTL (QNa.asl-7A, QK.asl-2B.2 and QK:Na.asl-6A) excluded more Na⁺ or accumulated more K⁺ compared to lines without these alleles. Importantly, the QK.asl-2B.2 allele for higher K⁺ accumulation was found to be associated with higher grain yield at all field sites. Several alleles at other QTL were associated with higher grain yields at selected field sites.

     

Study of Surface Plasmon Resonances of Core-Shell Nanosphere: A Comparison between Numerical and Analytical Approach

An investigation of the wavelength dependent extinction spectra of coated sphere with different core@shell compositions based on discrete dipole approximation technique has been presented in this paper. We have used combinations of A g, A u, and S i O ₂ for this analysis. Specifically, we study the impact of spherical core-shell thickness on its surface plasmon resonance (SPR) peak positions and corresponding spectral widening in distinct regimes of the spectrum. We observe that SPR peak of core-shell nanoparticle(CSNP) can be tuned over the visible to near-infrared spectrum region by manipulating the core/shell ratio and composition of core and shell. Specifically, for dielectric@metal (core@shell) nanoparticle, SPR peak position shifted towards lower wavelength as we increase the shell thickness, which is opposite to the SPR behavior of metal@dielectric. The extinction spectrum shows linear relation between SPR position and thickness of the shell. Further, we observed two resonant peaks for the case of metal@metal CSNP. The SPR peak of Au@Ag (a _eff 100 nm with shell thickness 8 nm) reveals two resonant peak corresponding to Au (594 nm) in red domain, while the peak in blue domain corresponds to Ag (402 nm). We also observe that optical resonance of CSNP can be tuned across the near-infrared region by changing the surrounding medium of higher refractive index. Further, near field pattern of core@shell geometry at resonance wavelength is also shown in the present study. We have also compared the numerical and analyticalmethod for smaller size CSNP with varying thickness and the results show good agreement.     

Surface Plasmon Resonance Immunosensor for the Detection of <Emphasis Type="Italic">Burkholderia pseudomallei</Emphasis>

Environmental surveillance of the Gram-negative bacterium Burkholderia pseudomallei is important in order to define human populations at risk of acquiring the infection; hence, in this study, we developed a method for the detection of B. pseudomallei based on surface plasmon resonance (SPR) using 4-mercaptobenzoic acid (4-MBA) modified gold SPR chip by monitoring the interaction of rpGroEL antigen (rpGroEL Ag) with immobilized rabbit antibody (anti-rpGroEL rAb). Affinity constant (K _D ) and maximum binding capacity of analyte (B _max) values for the interaction of rpGroEL Ag with the immobilized anti-rpGroEL rAb were calculated by using kinetic evaluation software and found to be 14.7 7 pM and 105.40 m^o, respectively. In addition, thermodynamic parameters such as ?G (Gibb’s free energy change), ?H (change in the enthalpy), and ?S (change in the entropy) were determined for the interaction between rpGroEL Ag and immobilized anti-rpGroEL rAb, and the values revealed that the interaction is spontaneous, exothermic, and driven by entropy.