Immobilization of poly(fluorene) within clay nanocomposite: an easy way to control keto defect

Blue light emitting cationic polyfluorene polymer(PF)/montmorillonite (MMT) nanocomposites were prepared by solution intercalation and exfoliation method to evaluate the effect of MMT on the nanocomposite structures, properties and morphologies. The properties of PF-MMT composites, containing 1-50 mass% MMT, were characterized unambiguously with the help of multiple analytical techniques, with focus on the keto defect and photostability of PF in the nanocomposites. XRD and HRTEM studies reveal both exfoliation of MMT galleries at lower content of MMT in composites and intercalation of PF chains into the MMT galleries at higher MMT content. The nanocomposites show higher thermal stability than pristine PF as anchorage of nanoclay in PF matrix occur through the electrostatic interaction between nanoclay and polymer. The decrease in Si-O-Si stretching frequency during exfoliation is much higher than in intercalation, as Si-O-Si experience lesser hindrance to vibrate in exfoliated MMT galleries. The gradual redshift of π-π(*) transition peak of PF with increasing MMT content in composites confirms the uncoiling of PF in clay galleries. The photoluminescence characteristics reveal interruption of interchain interaction in this intercalated and exfoliated organic/inorganic hybrid system, which reduces the low-energy emission that results from keto defect. Due to very high aspect ratio of MMT, it can act as an efficient exciton blocking layer and a barrier to oxygen diffusion, which may lead to a device with high color purity and enhanced photostability. Again current-voltage characteristics of nanocomposite films confirm the retention of LED properties after nanocomposite formation.     

Deficiently extremal Cohen-Macaulay algebras

The aim of this paper is to study homological properties of deficiently extremal Cohen-Macaulay algebras. Eagon-Reiner showed that the Stanley-Reisner ring of a simplicial complex has a linear resolution if and only if the Alexander dual of the simplicial complex is Cohen-Macaulay. An extension of a special case of Eagon-Reiner theorem is obtained for deficiently extremal Cohen-Macaulay Stanley-Reisner rings.     

Drastic increase of selectivity for H2O2 formation in direct oxidation of H2 to H2O2 over supported Pd catalysts due to their bromination

Incorporation of bromide anions (1.0 wt%) in supported Pd catalysts (viz. Pd supported on Al2O3, ZrO2, SiO2, H-beta or Ga2O3) leads to a drastic increase in their selectivity for H2O2 formation in the direct oxidation of H2 to H2O2 by O2(at room temperature) in an aqueous acidic (0.03 M H3PO4) reaction medium; the selectivity increase is accompanied by a large decrease in the H2O2 decomposition activity of the catalysts.     

Molecular-beam experiments for photodissociation of propenal at 157 nm and quantum-chemical calculations for migration and elimination of hydrogen atoms in systems C3H4O and C3H3O

We investigated the dynamics of photodissociation of propenal (acrolein, CH(2)CHCHO) at 157 nm in a molecular beam and of migration and elimination of hydrogen atoms in systems C(3)H(4)O and C(3)H(3)O using quantum-chemical calculations. Compared with the previous results of photodissociation of propenal at 193 nm, the major difference is that the C(3)H(3)O fragment present at the 193-nm photolysis disappears at the 157-nm photolysis whereas the C(3)H(2)O fragment absent at 193 nm appears at 157 nm. Optimized structures and harmonic vibrational frequencies of molecular species with gross formula C(3)H(2-4)O were computed at the level of B3LYP/6-311G(d,p) and total energies of those molecules at optimized structures were computed at the level of CCSD(T)/6-311+G(3df,2p). Based on the calculated potential-energy surfaces, we deduce that the C(3)H(3)O fragment observed in the photolysis of propenal at 193 nm is probably CHCCHOH ((2)A") and/or CH(2)CCOH ((2)A") produced from an intermediate hydroxyl propadiene (CH(2)CCHOH) following isomerization. Adiabatic and vertical ionization potentials of eight isomers of C(3)H(3)O and two isomers of C(3)H(2)O were calculated; CHCCHOH ((2)A") and CH(2)CCOH ((2)A") have ionization potentials in good agreement with the experimental value of ～7.4 eV. We also deduce that all the nascent C(3)H(3)O fragments from the photolysis of propenal at 157 nm spontaneously decompose mainly to C(2)H(3) + CO and C(3)H(2)O + H because of the large excitation energy. This work provides profound insight into the dynamics of migration and elimination of hydrogen atoms of propenal optically excited in the vacuum-ultraviolet region.     

Model-based seafloor characterization employing multi-beam angular backscatter data--a comparative study with dual-frequency single beam

Sediment geoacoustic inversion results are estimated employing a multi-beam (MB) echo-sounding system operable at 95 kHz. To characterize the western continental shelf of India (off Goa) seafloor, MB backscatter signals were acquired along with grab sediment samples. The substrate type and roughness of the site were estimated using the composite roughness scattering model with the measured backscatter values. The seafloor parameters, namely mean grain size (M(φ)); roughness spectrum strength (w(2)) and exponent (γ(2)); and sediment volume parameter (σ(2)), for coarse and fine grain sediments are estimated by employing the MB system. These parameters have also been estimated at two other frequencies (33 and 210 kHz) and are compared to the ground truth data to provide sufficient support in validating the model results and increasing the understanding of the shelf seafloor processes. Distinct interclass separations between the sediment provinces are evident from the estimated mean grain size M(φ) and water-sediment interface roughness w(2). The seafloor parameters for coarse and fine grain sediments derived from the 95 kHz MB data are consistent with the sediment sample data as well as with the inversion results obtained using backscatter data at 33 and 210 kHz from the same locations.     

Linear Systems and Quotients of Projective Space

A complete characterization of the categorical quotients of(P¹)ⁿ by the diagonal action of SL(2, C) with respect to anypolarization is given by M. Polito, in ‘SL(2, C)-quotientsde (P¹)ⁿ’, C. R. Acad. Sci. Paris Sér. I 321 (1995)1577–1582. In this paper, these categorical quotientsare obtained by certain linear systems on P^n–3, dependingon the given polarization. 2000 Mathematics Subject Classification14L24, 14L30     

Process development for isolation of dietary eugenol from leaves of basil (Ocimum sanctum) in combination of optimization of process variables and modeling by artificial neural network

Dietary eugenol helps prevent free radical-induced and lifestyle-related chronic illnesses such as cancer, autoimmune disorders, cardiovascular disease, and aging. A technique for extracting eugenol from green basil (Ocimum sanctum) leaves is created using a combination of extraction variable optimization and the organization of an artificial neural network (ANN) model. For thermally degradable bioactive eugenol, solvent extraction is the recommended separation method. With the following optimum variables: polarity of the solvent of 0.009, the solid-solvent ratio of 1.0 ?g/20 ?mL, stirring speed of 200 ?rpm, extraction temperature of 40 ?°C, and extraction duration of 40 ?min, a yield of 5.39 × ?10^?3 ?kg eugenol per kilogram dried leaves of basil was found. At 10 ?min of batch extraction, the highest throughput of eugenol was found to be 5.4 ?× ?10^?3 ?kg ?m^?3 ?s^?1. Additionally, experimental data are used to construct the yield prediction model. The statistical parameters that are obtained in model evaluation encourage the use of the predicted model for the commercialization of eugenol isolation.