Waveguide Cross Section and Background Magnetic Field Tapers for Broadbanding a Gyro-TWT

The gyro-TWT in a cylindrical waveguide of linearly-tapered cross section was analyzed for the gain-frequency response, using the Pierce-type gain equation. The taper in the waveguide cross section was adjusted for wide device bandwidths, either by changing the taper angle, while keeping the interaction length to be constant, or by changing the interaction length, while keeping the initial and final radii of the waveguide constant. Tapering led to the prediction of wide bandwidths, though at the cost of gain, as compared to a non-tapered device. The range of the DC background magnetic flux density relative to its grazing-point value was identified as a crucial parameter for large gains, with appreciable bandwidths, and minimum mode mixing in a tapered device, the latter in general facing more mode competition than a non-tapered device.     

Perturbation of higher-order solitons by fourth-order dispersion in optical fibers

We study analytically and numerically how the radiation emitted by fundamental solitons in the form of dispersive waves is affected by the third and fourth-order dispersions when a higher-order soliton undergoes the fission process inside an optical fiber. Our results show that two dispersive wave sidebands appear in the output spectrum on opposite sides of the input spectrum. The frequencies of these sidebands are set by the relative magnitudes of the third- and fourth-order dispersion parameters, but are not affected much by the Raman process. A well defined phase-matching condition accurately predicts these conjugate frequencies of dispersive wave. The relative amplitudes of these two sidebands are not equal because of the asymmetry induced by the third-order dispersion and higher-order nonlinearities. It is found that with increasing fourth-order dispersion the amplitude of both spectral components eventually saturate and the relative power level associated with one of the components can exceed 10% of the launched power under suitable conditions. This component is the one that will form even in the absence of fourth-order dispersion and its wavelength may lie on the red or the blue side of the launched wavelength depending on the sign of the dispersion slope at this wavelength. It is also observed that soliton order itself significantly influence the peak amplitude of the radiation and play a minor role in determining radiation frequencies. We believe, these results should be of relevance for applications requiring an ultrabroadband optical source and understanding the interesting facts of supercontinuum generation.     

Portable electro-optic device for performing serviceability check on IR guided missiles

Electro-optically guided weapons are the most potent and widely used munitions on land-based, aerial and ship-borne platforms because of their proven precision strike capability. Two such guided weapon categories include the IR guided surface-to-air and air-to-air missiles and laser guided bombs and missiles. The efficacy of the mission is critically dependent on the successful deployment of the weapon. This not only necessitates that periodic functionality check be carried out on these weapons, it should also be possible to perform functionality check also known as serviceability check even after they are strapped on to the launch platform. Serviceability check in the strap-on condition ensures a much higher hit probability. This paper presents the design and development of a portable electro-optic device that generates IR signatures in 3–5-μm band having the desired amplitude and spectral shape to match the IR signatures of target aircraft. A prototype was built using the proposed concept. The prototype was characterized in terms of its output amplitude and wavelength spectrum. The prototype was used to perform serviceability check on IR seekers of foreign origin. Test results are presented in the paper.     

Coverage-dependent chemisorption of Cl on Si(1 1 4)

The dissociative chemisorption of Cl₂ on Si(1 1 4) was studied at room temperature using scanning tunneling microscopy. Filled and empty state imaging revealed a multitude of possible adsorption configurations with adsorption preferring rebonded atom and dimer sites over tetramer sites. The dissociation and subsequent adsorption processes were sufficiently exothermic that Cl could interrogate the potential energy landscape and find local energy minima. Annealing revealed configurations that preserved the strongest π-bonds of the (1 1 4) reconstruction.     

Heteropogon contortus BL‐1 (Pilli Grass) and Elevated UV‐B Radiation: The Role of Growth,Physiological, and Biochemical Traits in Determining Forage Productivity and Quality

Exposure to elevated UV‐B (eUV‐B) is well known for its phytotoxicity, although studies made with UV‐B exposure and its impact on grasses are limited especially from tropical countries including India. In this study, responses of a valuable grass species, Heteropogon contortus BL‐1, were assessed under eUV‐B (over ambient UV‐B) at different growth stages. Damage caused by eUV‐B was observed in the form of membrane damage and loss of pigments at early stages of growth, whereas tannin, phenol, and protein contents showed their increments at all the growth stages, to overcome the imposed stress. Reducing sugar showed its decline at all the growth stages, whereas starch and sucrose contents were higher mostly at later ages of plant growth. eUV‐B caused a marked variations in anatomical structures with increase of mesophyll and spongy parenchymatous cells in leaves to reduce severity of irradiation, to maintain the growth and productivity. The study also highlights the significant negative influence of eUV‐B on the growth of H. contortus BL‐1 and its adaptive strategy to minimize the negative impacts. With the progression of age, plants although adopted to UV‐B stress with maintenance of productivity, but palatability of forage was affected due to increment of tannin content.     

New insight into the DNA binding studies,In-Vitro anti-cancer activity and molecular modelling of dioxo complexes of Molybdenum(VI) and Tungsten(VI) hydroxamic acids

The present study embodies the detail of interaction of Complex 1, Bis(N-phenyl-o-methoxybenzohydroxamato)Molybdenum(VI): [N-PMBHA-Mo(VI)] and Complex 2, Bis(N-phenylbenzohydroxamato)Tungsten(VI): [N-PBHA-W(VI)] with ct-DNA (Calf thymus-DNA) and its consequences by UV–Visible absorption spectroscopy, fluorescence spectroscopy, three-dimensional fluorescence spectroscopy, viscosity measurements and molecular docking. The intrinsic binding constant, K_b of complexes were determined which follows the order as complex 1 > complex 2 along with variation in shift and intensity for the complexes. Fluorescence spectroscopy applied for the determination of Stern–Volmer quenching constant, binding constant and the number of binding sites which reveals groove mode of binding. Non-radiative energy transfer between donor and acceptor molecule exposed by Förster energy transference theory (FRET) studies. The increase in the relative viscosity of ct-DNA with increasing the concentration of the complex 1 and complex 2 is also revealed. FTIR analysis also revealed that both the complexes interacted positively with bases and phosphates of ct-DNA. The docking studies complemented the experimental results revealing minor groove mode of binding for both the complexes. Finally, the in-vitro cytotoxicity studies indicate that the complexes have excellent anticancer activity against the breast cancer cell line, MCF-7, which could be a constructive guideline to produce new generations of anticancer agents.     

Novel semiconducting iron–quinizarin metal–organic framework for application in supercapacitors*

We present conductivity data for a newly synthesised metal–organic framework FeQ, Fe(C₁₄H₆O₄).H₂O demonstrating significant electronic transport. The electrical conductivity of the material is expected to be through the π–π interaction of the ligand-quinizarin and is measured to be 1.73?×?10^?2?Scm^?1_. Its potential role as supercapacitor electrodes is discussed.     

Effect of PVAc dispersal into PVA-NH4SCN polymer electrolyte

The present paper deals with ion transport studies on a new proton conducting composite polymer electrolyte — (PVA_x:NH₄SCN)_y:PVAc system. Complexation and morphology of the composite electrolyte films are discussed on the basis of X-ray diffraction and differential scanning calorimetry data. Coulometry and transient ionic current measurements revealed charge transport through protons. The maximum ion conductivity was found to be 7.4·10⁻⁴ S·cm⁻¹ for the composition: x=0.15, y=0.12. The observed conductivity behaviour is correlated to the morphology of the films. The temperature dependence of the electrical conductivity exhibits Arrhenius characteristics in two different temperature ranges separated by a plateau region related to morphological changes occurring in the electrolyte.     

Ligand exchange synthesis of organometallic Rh nanoparticles and application in explosive sensing

Alkyne {phenyl acetylene (PA) and 9-ethynylphenanthrene (EPT)}-ligated Rh nanoparticles (1 and 2, respectively) with mean diameter of 1.5 ± 0.2 nm were synthesized via a facile and high-yield biphasic ligand exchange protocol using similar sized ethylene glycol (EG)-stabilized Rh nanoparticles as precursors (EG:Rh). The synthesized organometallic Rh nanoparticles were convincingly characterized using several spectroscopic and microscopic techniques, e.g., Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (¹H NMR), optical absorption spectroscopy (UV-Vis), photoluminescence spectroscopy (PL), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscope (TEM). We propose that the syntheses mechanism relies on catalytic acetylenic (≡C–H, carbon–hydrogen) bond breaking by EG:Rh followed by strong metal–carbon bond formation with a vinyldiene (>C═C═M) motif. The obtained 1 and 2 showed luminescence property, which arises from ligand structure through intraparticle conjugation. Electron-rich phenanthrene-ligated Rh nanoparticles (2) showed good sensing performance for detection of electron deficient nitro-aromatic explosive molecules (NA) in solution phase through luminescence quenching method.