A UNIQUE SUPRAMOLECULAR STRUCTURE OF POLY [μ-OXO -BIS(1,1,2,3,4,5-HEXAHYDRO-1-NITRATOTELLUROPHENE)] [(C4H8TENO3)2O]N WITH—0-TE-0-TE-0—CROSS LINKED CHAINS

Abstract

Poly [μ-oxo bis(1,1,2,3,4.5-hexahydro- 1-nitratotellurophene)] 1, is prepared by the room temperature reaction of 1,1,2,3,4,5-hexahydro- 1.1 -diiodotellurophene with silver nitrate in deionised water. Crystals of 1 are monoclinic. space group CUc with a=13.930(2) Å, b =11.665(2) Å, c=10.0682(11) Å, β=116.264(8)^O and Z=A. The monomeric unit of the title compound is centrosymmetric, with an angular TeOTe skeleton containing bridging O atom at the centre of symmetry. These monomeric units are linked together through —O-Te-O-Te-O—cross linked chains and the nitrate groups are asymmetrically bidentate with a primary Te-ONO₂ and a secondary Te—O semibonding interaction. Each nitrate group further participates in another Te–O semibonding interaction forming another asymmetric Te(NO₃)₂Te bridge. The structural characteristics of 1 are compared with related complexes.     

A facile,catalyst-free synthesis of new polycyclic pyrrolo[1,2-b]pyrazolone derivatives

A convenient and efficient procedure has been developed for the synthesis of a new ring system, pyrrolo[1,2-b]pyrazolone, via two-component coupling reaction followed by base mediated intramolecular cyclization. Single-pot synthesis replacing the two step process has also been successfully carried out. A series of polycyclic pyrrolo[1,2-b]pyrazolone derivatives have been obtained by employing the procedure along with some fused pyrrol-1-ylamine system. The products were formed very rapidly in catalyst free condition in a good yield (up to 75%) and also it had tolerance to a wide scope of substrates.     

Radiofrequency pulse sequences which compensate their own imperfections. 1980

Radiofrequency pulse sequences are described which have the same overall effect as a single 90° or 180° pulse but which compensate the undesirable effects of resonance offset and spatial inhomogeneity of the radiofrequency field H₁. These “composite” pulses are built up from a small number of conventional pulses which rotate the nuclear magnetization vectors about different axes in the rotating frame, while in the intervals between pulses a limited amount of free precession may be allowed to occur. Insight into the way in which pulse imperfections are compensated is obtained by computer simulation of trajectories of families of nuclear spin “isochromats” representing a distribution of H₁ intensity or resonance offset. Composite 90° pulses are suggested as a method of reducing systematic errors in spin-lattice relaxation times derived from progressive saturation or saturation-recovery experiments, and as the preparation pulse of a spin-locking experiment. A test of the effectiveness of the composite 180° pulse sequence has been made by using it for population inversion in a spin-lattice relaxation measurement, where T₁ is derived from the null point in the recovery curve, a technique known to be very sensitive to pulse imperfections.     

State feedback stabilization of uncertain linear time‐delay systems: A nonlinear matrix inequality approach

A nonlinear matrix inequality is derived as a stabilizability condition of linear uncertain time‐delay systems. This inequality is seen as a less conservative one as well as efficient for numerical computation than the existing results as seen when solving by cone‐complementary algorithm. Copyright © 2010 John Wiley & Sons, Ltd.     

Stability criteria with less LMI variables for linear system with additive time-delays

In this technical note, equivalent stability criterion with minimal number of variables for three recently reported stability criteria is proposed for a class of linear systems with additive time-varying delays. The existing delay-dependent stability criteria for additive time-delay systems have more number of matrix variables in the LMI; and hence, they require more computational cost. The proposed equivalent criteria, unlike the original ones, encompass only the matrix variables that are associated in the Lyapunov-Krasovskii functional, making the criteria mathematically less complex and computationally more attractive. The complexity involved in the existing stability criteria is attributed to the fact the cross-terms that emanate from the time-derivative of the Lyapunov-Krasovskii functional are dealt with free-weighting matrices. Hence, apart from the matrix variables that are associated in the corresponding Lyapunov-Krasovskii functional, the existing criteria also have additional matrix variables in them. In this paper, we have devised techniques to eliminate the free-weighting matrices in the existing stability criteria without sacrificing the conservatism. The resulting equivalent stability criteria, therefore, have least possible number of variables in the LMI; and hence, have minimum computational burden. The effectiveness of the proposed equivalent criteria is validated on a numerical example.     

Dark Energy Models with Variable Equation of State Parameter

The dark energy models with variable equation of state parameter ω are investigated by using law of variation of Hubble’s parameter that yields the constant value of deceleration parameter. Here the equation of state parameter ω is found to be time dependent and its existing range for this model is consistent with the recent observations of SN Ia data, SN Ia data (with CMBR anisotropy) and galaxy clustering statistics. The physical significance of the dark energy models have also been discussed.     

Synthesis, growth and characterization of novel second harmonic nonlinear chalcone crystal

Nonlinear optical (NLO) materials are useful in many of the industrial applications. New NLO chalcone derivative (2E)-3-[4-(methylsulfanyl)phenyl]-1-(4-nitrophenyl)prop-2-en-1-one (4N4MSP) crystals have been grown by slow evaporation technique at ambient temperature. The grown crystals were subjected to single crystal X-ray diffraction study. The crystal has noncentrosymmetric structure in the orthorhombic system with space group Aba2 and unit cell parameters a=14.0647(15) Å, b=33.738(4) Å and c=6.0039(6) Å. To confirm the presence of various functional groups in the compound, FT-IR spectrum was recorded. The crystal was subjected to TGA/DTA analysis to find its thermal stability. The grown crystals were characterized for their optical transmission and mechanical hardness. The second harmonic generation (SHG) efficiency of the crystal is obtained by classical powdered technique using Nd:YAG laser and its value is 28.57 times that of urea. The laser damage threshold for 4N4MSP crystal was determined using Q-switched Nd:YAG laser. The refractive index values for green and red wavelengths were measured by Brewster angle technique. The dielectric and electrical measurements were carried out to study the different polarization mechanism and conductivity of the crystal. Good thermal, mechanical, transmission and SHG response make it desirable for the NLO applications.     

Search for the rare decays K(L)→π0π0μ+μ- and K(L)→π0π0X0→π0π0μ+μ-

The KTeV E799 experiment has conducted a search for the rare decays, K(L)→π(0)π(0)μ(+)μ(-) and K(L)→π(0)π(0)X(0)→π(0)π(0)μ(+)μ(-), where the X(0) is a possible new neutral boson that was reported by the HyperCP experiment with a mass of (214.3 ± 0.5) MeV/c(2). We find no evidence for either decay. We obtain upper limits of Br(K(L)→π(0)π(0)X(0)→π(0)π(0)μ(+)μ(-)) < 1.0 × 10(-10) and Br(K(L)→π(0)π(0)μ(+)μ(-)) < 9.2 × 10(-11) at the 90% confidence level. This result rules out the pseudoscalar X(0) as an explanation of the HyperCP result under the scenario that the dsX(0) coupling is completely real.     

Effective in-device r33 of 735 pm/V on electro-optic polymer infiltrated silicon photonic crystal slot waveguides

We design and fabricate a 320?nm slot for an electro-optic (E-O) polymer infiltrated silicon photonic crystal waveguide. Because of the large slot width, the poling efficiency of the infiltrated E-O polymer (AJCKL1/amorphous polycarbonate) is significantly improved. When coupled with the slow light effect from the silicon photonic crystal waveguide, an effective in-device r(33) of 735?pm/V, which to our knowledge is a record high, is demonstrated, which is ten times higher than the E-O coefficient achieved in thin film material. Because of this ultrahigh E-O efficiency, the V(π)L of the device is only 0.44?V?mm, which is to our knowledge the best result of all E-O polymer modulators.     

Equilibrium,kinetic, and thermodynamic studies of lead ion adsorption from mine wastewater onto MoS2-clinoptilolite composite

This work explored the potential of clinoptilolite, molybdenum sulphide (MoS₂), and MoS₂-clinoptilolite composite in lead (Pb) removal from aqueous medium and industrial mining wastewater. MoS₂-clinoptilolite composite was successfully prepared by a hydrothermal method. The surface properties, structure, and composition of the synthesized composite and the parent compounds were analyzed by scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. The removal efficiency of lead from aqueous solution was studied in batch-mode experiments. The MoS₂-clinoptilolite was used for the removal of Pb ions (50 mg/L) from an aqueous solution: ~100% of the Pb was removed with a MoS₂-clinoptilolite dose of 0.075 g, pH 6 at 328K within 90 min. The adsorption capacities of Pb onto MoS₂-clinoptilolite were found to be higher than those onto clinoptilolite. Metal ion adsorption behavior was well explained by the Freundlich model, that is, multilayer adsorption of Pb molecules occurred on the heterogeneous surface of adsorbents in case of clinoptilolite, while in the case of MoS₂-clinoptilolite, the Langmuir model was suitable, that is, the adsorption occurred on a monolayer surface. The rate of Pb adsorption was explained by pseudo-second-order model suggesting that the adsorption process is presumably chemisorption. Thermodynamic parameters such as ΔH°, ΔS°, and ΔG° were calculated, which indicated that the adsorption was spontaneous and exothermic in nature. The selectivity of each adsorbent for Pb was also tested by adding the adsorbents to real gold mine water which contains competitive metal ions.