Photophysics and Photocatalytic Properties of Cd(OH)(2)-Coated Q-CdS Clusters in the Presence of Guanine and Related Compounds

The photophysics of Cd(OH)(2)-coated Q-CdS in the presence of guanine and related compounds has been examined. Guanine and adenine quench the bandgap emission and reduce the emission lifetime of these particles. Approximately 50% of the bandgap fluorescence is quenched by a low [guanine] (2x10(-5) mol dm(-3)). Quenching takes place with a bimolecular rate constant of 2x10(12) dm(3) mol(-1) s(-1). The presence of these additives did not affect the red emission appreciably. The nature of the interaction between Cd(OH)(2) layer of Q-CdS and the additive has been analyzed by fluorescence and absorption spectroscopy. Interception of the hole by guanine and adenine occurs through their adsorption and hydrogen-bonding interaction between the -OH of Cd(OH)(2) and certain functional groups of the additive. Cd(OH)(2)-coated Q-CdS sensitizes the photodecomposition of guanine efficiently in the presence of oxygen under visible light irradiation. Shallowly trapped and direct holes are suggested to participate in the oxidation. The reactivity of the hole is governed by the redox potential of the solute. Copyright 2001 Academic Press.     

Carbon-13 NMR of 1,2-polybutadienes: Configurational sequencing

Carbon-13 Fourier-transform spectra (67.88 MHz) of 1,2-polybutadienes (PBDs) (I–IV) were obtained. The triad and pentad intensities were calculated for the olefinic methylene carbon (C-1). Bernoullian and first-order Markov-chain propagation statistics were tested to fit the experimental data. The pentad placements for the olefinic methine carbon (C-2) were also assigned using the data calculated for the C-1 carbon. Fine-structure splitting due to placements higher than pentads was observed for both C-1 and C-2 carbons in PBD samples III and IV.     

High-temperature resins based on aromatic amine-terminated bisaspartimides

Various 4,4′-bis{N²-[4-(4-aminophenoxy)phenyl]aspartimido}diphenylmethane (APADM)-type precursors were synthesized by Michael-type reaction of an aromatic bismaleimide (1mol) with an aromatic diamine (2 mol) in an aprotic solvent. The structures of these materials were characterized by using Fourier-transform infrared (FT-IR), ¹H nuclear magnetic resonance (NMR) and ¹³C-NMR; their curing behaviors and thermal stabilities were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The thermal polymerization of APADM by heating it above its melting temperature produced a tough polymer. From these preimidized precursors, graphite-fiber laminates were prepared and their mechanical properties evaluated. To elucidate the thermal curing mechanism and the structure of the polymer, a model compound, N-[4-(4′-aminobenzyl) phenyl] aspartimidobenzene was synthesized. The gas-chromatographic mass spectra of these compounds has suggested a mechanism for their decomposition. The structure of the polymer also was studied by using FT-IR and ¹H-NMR.     

Nano-assembly of manganese peroxidase and lignin peroxidase from P. chrysosporium for biocatalysis in aqueous and non-aqueous media

Development, characterization, and activity studies of nano-assemblies of lignin peroxidase (LiP), and manganese peroxidase (MnP) from Phanerochaete chrysosporium on flat surfaces as well as colloidal particles have been investigated. These assemblies of LiP and MnP were fabricated with polyelectrolytes-poly(ethylenimine) (PEI), poly(dimethyldiallylammonium chloride) (PDDA), and poly(allylamine) (PAH)-using a layer-by-layer self-assembly technique (LbL). Characterization of these assemblies on flat surfaces was monitored using quartz crystal microbalance (QCM), while assemblies on microparticles such as melamine formaldehyde (MF) were carried out with zeta potential analyzer (ZPA). A unique dynamic adsorption-desorption of the enzyme layers is observed during the assembly. All the nano-assemblies of LiP and MnP can effectively oxidize veratryl alcohol (VA) to its aldehyde for an extended period of time. The effect of different polyions and the number of polyion layers on the activities of LiP and MnP nano-assembly was also examined. It is observed that drying of enzyme layer during the assembly and the use of non-aqueous media, such as acetone can significantly reduce the activity of the enzymes. Enzyme activity reaches a minimum when the concentration of acetone is increased to 30%; however, the activity can be restored to its original value by increasing the concentration of aqueous media. Preliminary studies using assemblies of LiP and MnP on MF microparticles further demonstrate the feasibility of developing potential systems for degradation of environmental pollutants.     

Geometric mesh FDM for self-adjoint singular perturbation boundary value problems

A numerical method based on finite difference method with variable mesh is given for second order singularly perturbed self-adjoint two point boundary value problems. The original problem is reduced to its normal form and the reduced problem is solved by FDM taking variable mesh(geometric mesh). The maximum absolute errors max_i|y(x_i)-y_i|, for different values of parameter , number of points N, and the mesh ratio r, for three examples have been given in tables to support the efficiency of the method.     

Convergent synthesis of Carpatamide-A: Cytotoxic arylamine derivative from marine derived Streptomyces sp.

First total synthesis of carpatamide-A 7a, cytotoxic arylamine derivative isolated from marine derived Streptomyces sp., was achieved in twelve steps with overall yield of 24% with seven longest linear steps. In the penultimate step, dienoic acid 13 and an amino-phenylpropionic acid methyl ester core 21 were coupled to synthesize methylated derivativative of carpatamide-A 22 followed by demethylation of the intermediate with BBr₃ to accomplish carpatamide-A 7a. Both precursors 13 and 21 were synthesized from readily available starting materials i.e. isovaleraldehyde 8 and 2, 4-dihydroxy benzaldehyde 14.     

Processes developed for the separation of europium (Eu) from various resources

Europium (Eu), one of the most significant rare earth (RE) elements, has wide applications as functional material in phosphor production, majorly used in fluorescent lamps, computer monitors, televisions etc. Eu is one of the three divalent lanthanides (along with Yb and Sm) having a reduction potential higher than ?2 V. This possibility of Eu reduction is attributed to a relatively stable half-filled 4f⁷ electronic configuration, thus providing a high stabilization energy and selective recovery. But the Eu recuperation from natural minerals is either accompanied with other REs or Eu is recovered as a group of light REs. Selective recovery of Eu has sparked the progress for its reutilization through recycling of secondary resources. The perspectives of reclaiming Eu as a value added product from various sources using different pyro-hydro or hybrid techniques are discussed. The systematic research and salient findings on methods, viz., reduction, leaching, solvent extraction, as well as combined methods scaled-up to commercial scale to recover Eu, are also reported with recommendations. Thus, this comparative as well as summarized review hopes to help researchers to develop feasible processes for Eu recovery.     

Observation of the Low‐Frequency Spectrum of the Water Dimer as a Sensitive Test of the Water Dimer Potential and Dipole Moment Surfaces

Using the helium nanodroplet isolation setup at the ultrabright free‐electron laser source FELIX in Nijmegen (BoHeNDI@FELIX), the intermolecular modes of water dimer in the frequency region from 70 to 550 cm^?1 were recorded. Observed bands were assigned to donor torsion, acceptor wag, acceptor twist, intermolecular stretch, donor torsion overtone, and in‐plane and out‐of‐plane librational modes. This experimental data set provides a sensitive test for state‐of‐the‐art water potentials and dipole moment surfaces. Theoretical calculations of the IR spectrum are presented using high‐level quantum and approximate quasiclassical molecular dynamics approaches. These calculations use the full‐dimensional ab initio WHHB potential and dipole moment surfaces. Based on the experimental data, a considerable increase of the acceptor switch and a bifurcation tunneling splitting in the librational mode is deduced, which is a consequence of the effective decrease in the tunneling barrier.     

Generalized relationships for estimating soil thermal resistivity

Thermal properties of soils are of great importance in view of the subsurface transmission of either heated fluids or high power currents. For these situations, it is essential to estimate the resistance offered by the soil mass in dissipating the heat generated through it. Thermal resistivity of soils is a complex phenomenon that depends upon various parameters, viz., type of the soil, particle size distribution, its compaction characteristics, etc. A laboratory probe has been developed based upon the principle of transient method to measure thermal resistivity of different soils for a state of compaction. Based on these results, generalised relationships have been developed, for predicting soil thermal resistivity, and their efficiency has been established by comparing the obtained results with those available in literature.     

Modified INOvent for delivery of inhaled nitric oxide during cardiac MRI

Background

The aim of this study was to assess the feasibility of delivering NO through a modified system to allow clearance of the magnetic field and thus compatibility with cardiac magnetic resonance (CMR). Nitric oxide (NO) is an inhalational, selective pulmonary vasodilator with a wide range of applications in a variety of disease states, including diseases that affect the right ventricle. Accurate assessment of dynamic changes in right ventricular function necessitates CMR; however, delivery of NO is only possible using equipment that is not magnetic resonance imaging (MRI) compatible (INOvent delivery system, Ohmeda, Inc., Madison, WI, USA).

Methods

The INOvent delivery system was modified by using 35 ft. of standard oxygen tubing to allow NO delivery through an electrical conduit and into the MRI suite. The concentrations of oxygen (O₂), nitrogen dioxide (a harmful byproduct, NO₂) and NO were measured in triplicate using the built-in electrochemical analyzer on the INOvent. After confirmation of safety, the system was used to administer drug to a patient x, and dynamic MRI measurements were performed.

Results

When the standard INOvent was set to administer 40 ppm of NO, the mean/standard deviation of gas delivered was as follows: NO: 42/0 ppm; NO₂: 0.3/0.1 ppm; and O₂: 93/0 ppm. In comparison, the gas delivery of the modified INOvent was follows: NO: 41/0 ppm; NO₂: 0.5/0 ppm; and O₂: 93.7/0.6 ppm. During administration to an index patient with severe pulmonic insufficiency (PI), a measurable reduction in PI was observed by CMR.

Conclusions

Nitric oxide can be administered through 35 ft. of standard oxygen tubing without significantly affecting dose delivery. This technique has potential application in patients with right-sided structural heart disease for determination of dynamic physiological changes.