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Quadrupole-Quadrupole Interactions to Control Plasmon-Induced Transparency
No full textRadiative dipolar resonance with Lorentzian line-shape induces the otherwise dark quadrupolar resonances resulting in electromagnetically induced transparency (EIT). The two interfering excitation pathways of the dipole are earlier shown to result in a Fano line shape with a high figure of merit suitable for sensing. In metamaterials made of metal nanorods or antennas, the plasmonic EIT (PIT) efficiency depends on the overlap of the dark and bright mode spectra as well as the asymmetry resulting from the separation between the monomer (dipole) and dimer (quadrupole) that governs the coupling strength. Increasing asymmetry in these structures leads to the reduction of the figure of merit due to a broadening of the Fano resonance. We demonstrate a PIT system in which the simultaneous excitation of two dipoles result in double PIT. The corresponding two quadrupoles interact and control the quality factor (Q) of the PIT resonance. We show an antiresonancelike symmetric line shape with nonzero asymmetry factors. The PIT resonance vanishes due to quadrupole-quadrupole coupling. A Q factor of more than 100 at 0.977 THz is observed, which is limited by the experimental resolution of 6 GHz. From polarization-dependent studies we show that the broadening of the Lorentzian resonance is due to scattering-induced excitation of orthogonally oriented dipoles in the monomer and dimer bars in the terahertz regime. The high Q factors in the terahertz frequency region demonstrated here are interesting for sensing application
Embelin-Mediated Green Synthesis of Quasi-Spherical and Star-Shaped Plasmonic Nanostructures for Antibacterial Activity, Photothermal Therapy, and Computed Tomographic Imaging
No full textPlasmonic nanostructures of silver and gold synthesized by conventional toxic and cumbersome methodologies raise huge concern for their clinical application, which necessitates the use of a greener approach. Herein, embelin, a benzoquinone derivative extracted from the fruits of Embelia tsjeriam-cottam, with immense medicinal value, is used as a reducing and stabilizing agent for the synthesis of quasi spherical gold and silver nanoparticles as well as gold nanostars. A sunlight-assisted synthesis resulted in embelin-stabilized silver nanoparticles of bimodal size distribution (similar to 3 and 15 nm) with potent antibacterial activity against Staphylococcus aureus and Escherichia coli. Similarly, embelin was also used for the synthesis of polyhedral gold nano particles of 12-15 nm in size and absorbance at 540 nm. These highly faceted and multitwinned gold nanoparticles facilitated the formation of 120 nm sized embelin-stabilized gold nanostars absorbing at NIR wavelength (800 nm). The embelin-stabilized nanoparticles demonstrated excellent compatibility toward cells and human blood. Additionally, the gold nanostars exhibited superior computed tomographic (CT) contrast characteristics and marked photothermal cytotoxicity toward oral epithelial carcinoma cells. This study thus proposes, for the first time, the synthesis of biocompatible plasmonic nanostructures using embelin and their potential use as antibacterial, CT imaging, and photothermal agents
RANK OF A CO-DOUBLY COMMUTING SUBMODULE IS 2
No full textWe prove that the rank of a non-trivial co-doubly commuting sub-module is 2. More precisely, let phi,psi is an element of H-infinity(D) be two inner functions. If Q(phi) = H-2(D)/phi H-2(D) and Q(psi) = H-2(D)/psi H-2(D), then rank (Q(phi) circle times Q(psi))(perpendicular to) = 2. An immediate consequence is the following: Let S be a co-doubly commuting submodule of H-2(D-2). Then rank S = 1 if and only if S = Phi H-2(D-2) for some one variable inner function Phi is an element of H-infinity(D-2). This answers a question posed by R. G. Douglas and R. Yang [ Integral Equations Operator Theory 38(2000), pp207-221
High- and Intermediate-Temperature Performance of Asphalt Binder Containing Carbon Nanotube Using Different Rheological Approaches
No full textThe present research work was undertaken to evaluate the rutting performance of carbon nanotube (CNT)-modified asphalt binders. Additionally, intermediate-temperature performance, aging resistivity potential, and high-temperature storage stability were also evaluated. Reported literature on rutting performance of CNT-modified asphalt binders is mainly based on the Superpave rutting parameter (G*/sin), which does not account for the recovery aspect of binder. The paper first highlights the importance of the elastic response of CNT-modified asphalt binders for better understanding about its rutting performance. Further, different approaches such as the evaluation of zero shear viscosity (ZSV), creep test, and multiple stress creep recovery (MSCR) were utilized to reach appropriate conclusions. A recently developed approach, linear amplitude sweep (LAS), was used for evaluating intermediate-temperature performance. The CNT was varied as 0, 0.4, 0.75, 1.5, and 2.25% by the weight of control binder. The G*/sin value was found to increase until 1.5% CNT content; however, the addition of 2.25% CNT resulted in decreased G*/sin, indicating reduced rutting performance at higher CNT content. Contrary to the G*/sin trend, significant improvement in recovery value was observed for all CNT percentages. Further, based on detailed analysis carried out for different rheological parameters such as ZSV value (evaluated using the steady shear approach), deformation resistivity potential from creep test, recovery (R), and nonrecoverable creep compliance (Jnr) from the MSCR test, CNT addition to the control binder showed significant improvement in rutting resistivity potential for all CNT percentages. Although ZSV value significantly improved with the addition of CNT, the increase in CNT content showed an early transition from Newtonian to non-Newtonian behavior. Further, analysis for stress sensitivity was carried based on the R and Jnr values obtained from the MSCR test, which showed an increase in stress sensitivity with the addition of CNT to the control binder. The need for improvement in the current protocol used for evaluating stress sensitivity of asphalt binder (based on the MSCR test) has also been discussed. Improvement in intermediate-temperature performance evaluated through LAS test was also observed. Also, CNT addition to asphalt binder was found to be stable under high-temperature storage conditions. Overall, improvement in high- and intermediate-temperature performance can be expected with the addition of CNT to the control binder
Colorimetric and fluorimetric detection of Hg2+ and Cr3+ by boronic acid conjugated rhodamine derivatives: Mechanistic aspects and their bio-imaging application in bacterial cells
No full textCalorimetric and fluorimetric detection of toxic metal ions such as Hg2+ and Cr3+ has gained tremendous popularity over the conventional methods due to their operational simplicity, high selectivity, and speediness. Although numerous colorimetric and fluorescent receptors for Hg2+ or CO3+ were reported in the literature, boronic acid-based receptors for these metal ions are rather scarce in the literature. Hence, in the present study dual function boronic acid conjugated rhodamine derivatives were developed, and their toxic metal ion detection abilities were studied by absorption, emission and visual detection methods. Absorption and emission spectral studies revealed that these derivatives displayed selectivity towards Hg2+, Cr3+ and Fe3+ among the other metal ions studied by forming new absorption band. Both the derivatives exhibited colorimetric response towards Hg2+ and Cr3+ by the change in color of the solution to pink and reddish pink with Fe3+. The detailed mechanism involved in the detection of Hg2+ was deduced by H-1 NMR and ESI-MS studies. Further, these derivatives were used for fluorescence imaging of Hg2+ and Cr3+ in S. aureus bacterial cells. Thus the present manuscript demonstrated the use of boronic acid conjugated rhodamine derivatives as a dual function (colorimetric and fluorescent) probes and as imaging agents for Hg2+ and Cr3+, which are known for their toxic influence on bacterial cells. (C) 2017 Elsevier B.V. All rights reserved
Inflation with f (R, phi) in Jordan frame
No full textWe consider an f (R) action that is non-minimally coupled to a massive scalar field. The model closely resembles scalar-tensor theory and by conformal transformation can be transformed to Einstein frame. To avoid the ambiguity of the frame dependence, we obtain an exact analytical solution in Jordan frame and show that the model leads to a period of accelerated expansion with an exit. Further, we compute the scalar and tensor power spectrum for the model and compare them with observations
Enhanced infrared sensing properties of vanadium pentoxide nanofibers for bolometer application
No full textThe main aim of this work is to report an alternative technique of creating vanadium pentoxide (V2O5) based uncooled infrared (IR) detector, by a state-of-the-art V2O5 nanofibers, manufactured by facile and economical electrospinning process. The nanofibers were thermally and electrically characterized to determine their bolo-metric performance. The nanofibers show maximum voltage responsivity (Rv) 6987.3 V/W at 100 mA DC bias, in a normal room temperature and pressure condition. Nanofibers show very good thermal response (tau(s)) and recovery time (tau(r)) when subjected to a periodic On-Off cycle of IR lamp (150 W) illumination. Temperature dependent resistance measurement shows that nanofibers are exhibiting semiconductor to metallic phase transition at 67 degrees C with maximum temperature coefficient of resistance (TCR%) -1.6%/K at the transition. V2O5 nanofibers characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman Spectroscopy confirms their crystallinity and elemental composition. The optical band gap of the nanofibers is analyzed by UV-Visible spectroscopy. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images confirms their microstructural dimensions and surface homogeneity. The entire analysis reaffirms the suitability of V2O5 nanofibers as one of the futuristic sensing material for IR imaging applications
Heat transfer investigations on impinging flame jets of a multi-port convex burner
No full textMulti-port curved surface burners are used in industrial boilers, preheating of large diameter pipes, textile industries, preheating of cylindrical metal billets and other industrial applications. The present work reports the heat transfer characteristics of convex shaped burner with 49 inline ports arranged in an array of 7 each. The methane-air premixed flame jets are impinged on the concave surface of a curved plate placed with radial spacing of 12 mm. Two different burners with port diameters of 2 mm and 3 mm with pitch to diameter ratio of 2.33 are used. The flame jet is studied for Reynolds number (Re) ranging from 75 to 200 and equivalence ratio of 0.9-1.5. The characterisation is done by impinging the pre-characterised air jets of various flow rates on the rear surface and capturing the wall temperature. The wall temperature is analysed to get the distributions of Nusselt number and effectiveness. The variation of coefficient of variance of Nusselt number, average Nusselt number and thermal efficiency is reported in the present work. The Nusselt number and effectiveness distributions increase with the increase in mixture Reynolds number. For a fixed mixture Reynolds number, the optimum heat transfer is obtained for stoichiometric flame. The thermal efficiency and average heat transfer of 2 mm port diameter is observed to be 18-25% higher as compared with burner with port diameter of 3 mm. Correlations are developed to predict the average Nusselt number, average effectiveness, coefficient of variance (COV) of Nusselt number distribution and thermal efficiency
Cyanobacteria: Promising biocatalysts for sustainable chemical production
No full textCyanobacteria are photosynthetic prokaryotes showing great promise as biocatalysts for the direct conversion of CO2 into fuels, chemicals, and other value-added products. Introduction of just a few heterologous genes can endow cyanobacteria with the ability to transform specific central metabolites into many end products. Recent engineering efforts have centered around harnessing the potential of these microbial biofactories for sustainable production of chemicals conventionally produced from fossil fuels. Here, we present an overview of the unique chemistry that cyanobacteria have been co-opted to perform. We highlight key lessons learned from these engineering efforts and discuss advantages and disadvantages of various approaches
Plane strain cylindrical indentation of functionally graded half-plane with exponentially varying shear modulus in the presence of residual surface tension
No full textA functionally graded half-plane with shear modulus varying exponentially along the direction normal to the surface and surface effects accounted through Gurtin Murdoch model, indented by long rigid smooth cylindrical indenter is solved to understand the effect of material inhomogeneity and surface effects on indentation response. The Green's function relating surface load to surface displacement under plane strain condition is obtained semi analytically through the combination of Airy stress function approach and Fourier transforms and utilized to solve the contact problem. The solution is used to study the effect of inhomogeneity through grading parameter and surface effects through residual surface tension based intrinsic length scale on the contact pressure, contact size and in-plane normal stress on the surface responsible for cracks during indentation. (C) 2017 Elsevier Ltd. All rights reserved