Experimental and Theoretical Insights into the Optical Properties and Intermolecular Interactions in Push-Pull Bromide Salts

Experimental and theoretical insights into the nature of intermolecular interactions and their effect on optical properties of 1-allyl-4-(1-cyano-2-(4-dialkylaminophenyl)vinyl)pyridin-1-ium bromide salts ( I and II ) are reported. A comparison of optical properties in solution and in the solid-state of the salts ( I and II ) with their precursors ( Ia and IIa ) is made. The experimental absorption maxima (λ_max) in CHCl₃ is at 528 nm for I and at 542 nm for II , and a strong bathochromic shift of ∼110 nm is observed for salts I and II compared with their precursors. The absorption bands in solid-state at ∼627 nm for I and at ∼615 nm for II that are assigned to charge transfer (CT) effect. The optical properties and single crystal structural features of I and II are explored by experimental and computational tools. The calculated λ_max and the CT are in good agreement with the experimental results. The intermolecular interactions existing in the crystal structures and their energies are quantified for various dimers by PIXEL, QTAIM and DFT approaches. Three types of interactions, (i) the cation⋅⋅⋅cation interactions, (ii) cation⋅⋅⋅anion interactions and (iii) anion⋅⋅⋅anion interactions are observed. The cationic moiety is mainly destabilized by C−H⋅⋅⋅N/π and π⋅⋅⋅π interactions whereas the cation and anion moiety is predominantly stabilized by strong C−H⋅⋅⋅Br⁻ interactions in both structures. The existence of charge transfer between cation and anion moieties in these structures is established through NBO analysis.     

Thin films of semiconducting lithium ferrite produced by pulsed laser deposition

Thin films of lithium ferrite (Li_0.5Fe_2.5O₄) have been deposited on (0 0 1) Al₂O₃ by pulsed laser deposition, with substrate deposition temperatures ranging between 500 and 800 °C, and oxygen pressures between 1 × 10⁻¹ and 4 × 10⁻⁷ mbar. X-ray diffraction shows that films grow with a (1 1 1) orientation. Conversion electron Mössbauer spectra for the high-pressure films show a single sextet with a hyperfine field of 49 T, while the low-pressure films show two sextets with hyperfine fields of 47 and 49 T. The spectra also reveal paramagnetic ferric iron in both types of films. Magnetization measurements of the films show a saturation magnetization of between 1.7 and 3.1μ_B per formula unit and a coercivity of between 10 and 44 mT. The films prepared under the lower oxygen pressures are semiconducting with resistivities of 2 × 10⁻² to 8 × 10⁻² Ω cm. They exhibit an anomalous Hall effect with p-type conduction at 175 K.     

Modulation of the PGE2-Mediated Pathway in the Eclosion Blocking Effect of Flumethrin and Terpenoid Subfraction Isolated from Artemesia nilagirica in Rhipicephalus annulatus

Prostaglandins are a group of important cell-signaling molecules involved in the regulation of ovarian maturation, oocyte development, egg laying and associated behaviors in invertebrates. However, the presence of prostaglandin E₂ (PGE₂), the key enzymes for PGE₂ biosynthesis and its interference by drugs were not investigated previously in the ovary of ticks. The present study was undertaken to assess the modulation of the PGE₂-mediated pathway in the eclosion blocking effect of flumethrin and terpenoid subfraction isolated from Artemisia nilagirica in Rhipicephalus annulatus ticks. The acaricidal activities and chemical profiling of the terpenoid subfraction were performed. The localization of the cyclooxygenase1 (COX1) and prostaglandin E synthase (PGES) enzymes and the quantification of PGE₂ in the ovaries of the ticks treated with methanol (control), flumethrin and terpenoid subfraction were also undertaken. In addition, the vitellogenin concentration in hemolymph was also assayed. Both flumethrin and the terpenoid subfraction of A. nilagirica elicited a concentration-dependent inhibition of fecundity and blocking of hatching of the eggs. The COX1 could not be detected in the ovaries of treated and control ticks, while there was no significant difference observed in the concentration of vitellogenin (Vg) in them. The presence of PGES in the oocytes of control ticks was confirmed while the immunoreactivities against PGES were absent in the vitellogenic oocytes of ticks treated with flumethrin and terpenoid subfraction. The levels of PGE₂ were below the detection limit in the ovaries of the flumethrin-treated ticks, while it was significantly lower in the ovaries of the terpenoid subfraction-treated ticks. Hence, the prostaglandin E synthase and PGE₂ were identified as very important mediators for the signaling pathway for ovarian maturation and oviposition in ticks. In addition, the key enzyme for prostaglandin biosynthesis, PGES and the receptors for PGE₂ can be exploited as potential drug targets for tick control. The detection of PGES by immunohistochemistry and quantification of PGE₂ by LC-MSMS can be employed as valuable tools for screening newer compounds for their eclosion blocking acaricidal effects.     

Generalized statistics framework for rate distortion theory

Variational principles for the rate distortion (RD) theory in lossy compression are formulated within the ambit of the generalized nonextensive statistics of Tsallis, for values of the nonextensivity parameter satisfying 0<q<1 and q>1. Alternating minimization numerical schemes to evaluate the nonextensive RD function, are derived. Numerical simulations demonstrate the efficacy of generalized statistics RD models.     

6a,6b,12a,12b‐Tetra­hydro­cyclo­octa­[3,4]­cyclo­buta­[1,2][8]­annulene

The cis,syn,cis‐tricyclic [2+2]‐dimer of cyclo­octatetraene, C₁₆H₁₆, crystallizes in space group Pca2₁ with two mol­ecules in the asymmetric unit. An extensive network of weak C—H⋯π(Czdbnd;C) interactions between the two independent mol­ecules, A and B, as well as A⋯A and B⋯B interactions, are observed in the supramolecular assembly. The C—H groups point more towards one C atom than to the centre of the Czdbnd;C bond. Notable among the interactions are bifurcated (cyclo­butane)C—H⋯Czdbnd;C contacts that span transannularly the eight‐membered ring.     

Fungal based synthesis of silver nanoparticles—An effect of temperature on the size of particles

A simple and effective approach to aqueous based biosynthesis of silver nanoparticles was demonstrated and the effect of temperature on controlling size of silver nanoparticles was studied. The morphology and uniformity of silver nanoparticles were investigated by UV–Vis spectroscopy, X-ray diffraction and HrTEM. The functional group of protein molecule was identified using FTIR. Increase in reaction temperature leads to decrease in size of silver nanoparticles and increase in monodispersity.     

Simple synthesis and spectroscopic studies on cobalt added ZnO nanocrystals

Cobalt doped zinc oxide nanoparticles were prepared through simple wet chemical method. X-ray diffraction studies confirm the prepared particles are in wurtzite structure. Scanning Electron Microscopy studies show the shape and morphology of the particles. To identify the presence of cobalt in ZnO, Energy Dispersive X-ray analysis was done. Optical absorption measurements show the presence of exciton peak at 375 nm. Photoluminescence studies were done with the excitation wavelength of 330 nm, which shows the emission because of exciton recombination and oxygen vacancy.     

Synthesis and structural characterization of symmetrical closo-4,7-I2-1,2-C2B10H10 and [(CH3)3NH][nido-2,4-I2-7,8-C2B9H10

The boron-atom insertion reaction of nido-9,11-I(2)-7,8-C(2)B(9)H(9)(2-), with the HBCl(2):SMe(2) complex yields closo-4,7-I(2)-1,2-C(2)B(10)H(10), 1, in excellent yield. Although the two boron atoms (B3 and B6) nearest to the carbon atoms in 1 are equally available for attack by nucleophiles, the boron-degradation reaction of 1 with alkoxide ion occurs only at the B6 vertex, yielding regioselectively [(CH(3))(3)NH][nido-2,4-I(2)-7,8-C(2)B(9)H(10)], 2. The molecular structures of 1 and 2 have been determined by X-ray diffraction studies. Crystallographic data are as follows. For 1, monoclinic, space group P2(1)/n, a = 6.9199(19) Angstroms, b = 23.9560(7) Angstroms, c = 7.2870(2) Angstroms, beta = 94.081(4) degrees, V = 1204.9(6) Angstroms(3), Z = 4, rho(calcd) = 2.18 g cm(-3), R = 0.020, R(w) = 0.0610; for 2, orthorhombic, space group Pca2(1), a = 14.1141(7) Angstroms, b = 7.0276(4) Angstroms, c = 16.4602(9) Angstroms, V = 1632.7(15) Angstroms(3), Z = 4, rho(calcd) = 1.81 gcm(-3), R = 0.022, R(w) = 0.0623.     

Cyanate ester tethered POSS/BACY nanocomposites for low‐k dielectrics

Low‐k dielectrics have been developed as an interlayer insulating material in the large scale integrated circuitry devices by the copolymerization of various weight percentages (10, 20, 30, and 40 wt%) of cyanate ester tethered POSS (POSS‐OCN) and bisphenol‐A cyanate ester (BACY) to obtain BACY/POSS‐OCN nanocomposites. The reinforcement of POSS‐OCN significantly contributes to the reduction in the value of dielectric constant and dielectric loss as well, which might be due to the presence of porous structured POSS‐OCN. The 30 wt% POSS‐OCN/BACY nanocomposite possesses the lowest value of dielectric constant of 1.81 at 1 MHz. Copyright © 2016 John Wiley & Sons, Ltd.     

Performance of a Binary PPM Ultra-Wideband Communication System with Direct Sequence Spreading for Multiple Access

In this paper, we present an analysis of the BER performance of an ultra-wideband (UWB) system with pulse position modulation (PPM) for data modulation and direct sequence (DS) spreading for multiple access over indoor lognormal fading channels. A rake receiver is used to combine a subset of the resolvable multipath components using the maximal ratio combining technique. Inter-path and multiple-access interferences are modeled and incorporated into the bit-error-rate expressions. The analytical and simulation results allow one to quantify many critical aspects of a DS-PPM UWB system such as the gain of the optimally spaced signaling scheme over the orthogonal signaling scheme, the potential error floor given a specific channel multipath delay spread and the number of interfering users, tolerance of the system to timing jitter, and impact of user codes.