Role of hydroxyl group on the mesomorphism of alkyl glycosides:synthesis and thermal behavior of alkyl 6-deoxy-beta-D-glucopyranosides

A homologous series of alkyl 6-deoxy-beta-D-glucopyranoside amphiphiles was prepared,in an effort to identify the role of hydroxyl group in the mesomorphic behavior of alkyl glycosides. Synthesis was performed by a chlorination of the sugar moiety in alkyl-beta-D-glucopyranosides with methylsulfonyl chloride in DMF, followed by a metal mediated dehalogenation to secure alkyl 6-deoxy-beta-D-glucopyranosides, wherein the alkyl chain length varied from C-9 to C-16. The mesomorphic behavior of these 6-deoxy alkyl glycosides was assessed using polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction method. Whereas the lower homologues exhibited a monotropic SmA phase till sub-ambient temperatures, the higher homologues formed a plastic phase. A partial interdigitized bilaye structure of SmA phase is inferred from experimental d-spacing and computationally derived lengths of the molecules. The results were compared with those of normal alkyl glucopyranosides, retained with hydroxyl groups at C-2-C-6 carbons, and alkyl 2-deoxy-glucopyranosides, devoid of a hydroxyl group at C-2 and the comparison showed important differences in the mesomorphic behavior.(C)2010 Elsevier Ireland Ltd. All rights reserved.

Quantitation of serological cross-reactivity between two geographical isolates of Oryctes baculovirus by a modified ELISA

An assay was developed for quantitation of the antigenic relationship between viruses, by modification of the indirect ELISA. The principle of this method is to estimate the epitopes not shared between the related viruses, after titration of the antibodies specific to the common epitopes as in a blocking ELISA. In practice, varying concentrations of purified virus are preincubated with a fixed dilution of heterologous or homologous antiserum and the unbound antibodies present in the mixture are back titrated with virus particles bound to microtitre plates. The antigenic relationship is described in terms of differentiation index (DI) and total antigenic reactivity (TAR). This method has been used to quantitate cross-reactivity between two geographically different isolates of Oryctes baculovirus.

Combined free and forced convection along a rotating vertical cylinder

The steady incompressible laminar mixed convection boundary layer flow along a rotating slender vertical cylinder with an isothermal wall has been studied. The transformed coupled nonlinear partial differential equations have been solved numerically using the Keller box method. In general, the rotation of the cylinder, the buoyancy forces and the curvature parameter are found to significantly affect the skin friction, heat transfer, velocity and temperature profiles as well as the pressure distribution. The buoyancy forces cause an overshoot in the axial velocity profile but the rotation and curvature parameters reduce it.

Formation and crystallization of hydrogen-induced amorphous SmFe2H3.6 alloy

On hydrogenation of the Laves phase SmFe2, an amorphous SmFe2H3.6 (a-SmFe2H3.6) alloy was formed between 400 K and 500 K. The amorphous nature of the alloy was confirmed by X-ray diffraction, transmission electron microscopy and thermal analysis. However, SmFe2 absorbed hydrogen in the crystal state below 350 K and decomposed into SmH2 and α-Fe above 550 K. The crystallization behaviour of a-SmFe2H3.6 was investigated by differential scanning calorimetry in combination with electron microscopy. Even after considerable hydrogen desorption (Image ) by an endothermic reaction on heating, the amorphous state was retained. Crystallization of a-SmFe2H3.6 took place in two stages. The first stage involved the precipitation of α-Fe in the amorphous matrix. The second stage involved the decomposition of the remaining amorphous phase into the equilibrium phases SmH2 and SmFe2.

Effect of network connectivity on thermal properties of As30Te70-xTlx glasses

Alternating differential scanning calorimetry (ADSC) studies were undertaken to investigate the effect of Tl addition on the thermal properties of As30Te70-xTlx ( 6 <= x <= 22 at%) glasses. These include parameters such as glass-transition temperature (T-g), changes in specific heat capacity (Delta C-p) and relaxation enthalpy (Delta H-NR) at the glass transition. It was found that T-g of the glasses decreased with the addition of Tl, which is in contrast to the dependence of T-g in As - Te glasses on the addition of Al and In. The change in heat capacity Delta C-p through the glass transition was also found to decrease with increasing Tl content. The addition of Tl to the As - Te matrix may lead to a breaking of As - Te chains and the formation of Tl+Te- AsTe2/2 dipoles. There was no significant dependence of the change of relaxation enthalpy, through the glass transition, with composition.

Carbon nanotube reinforced supramolecular gels with electrically conducting, viscoelastic and near-infrared sensitive properties

Pristine and long-chain functionalized single-walled carbon nanotubes (SWNTs) were incorporated successfully in supramolecular organogels formed by an all-trans tri(p-phenylenevinylene) bis-aldoxime to give rise to new nanocomposites with interesting mechanical, thermal and electrical properties. Variable-temperature UV-vis and fluorescence spectra reveal both pristine and functionalized SWNTs promote aggregation of the gelator molecules and result in quenching of the UV-vis and fluorescence intensity. Electron microscopy and confocal microscopy show the existence of a densely packed and directionally aligned fibrous network in the resulting nanocomposites. Differential scanning calorimetry (DSC) of the composites shows that incorporation of SWNTs increases the gel formation temperature. The DSC of the xerogels of 1-SWNT composites indicates formation of different thermotropic mesophases which is also evident from polarized optical microscopy. The reinforced aggregation of the gelators on SWNT doping was reflected in the mechanical properties of the composites. Rheology of the composites demonstrates the formation of a rigid and viscoelastic solid-like assembly on SWNT incorporation. The composites from gel-SWNTs were found to be semiconducting in nature and showed enhanced electrical conductivity compared to that of the native organogel. Upon irradiation with a near IR laser at 1064 nm for 5 min it was possible to selectively induce a gel-to-sol phase transition of the nanocomposites, while irradiation for even 30 min of the native organogel under identical conditions did not cause any gel-to-sol conversion.

Ferrocene-Promoted Photoactivated DNA Cleavage and Anticancer Activity of Terpyridyl Copper(II) Phenanthroline Complexes

Ferrocene-appended copper(II) complexes [Cu( Fc-tpy)(B)](ClO4)(2) (1-3) and [Cu(Ph-tpy)(dppz)](ClO4)(2) (4) as control, where Fc-tpy is 4'-ferroceny1-2,2':6',2 ''-terpyridine, Ph-tpy is 4'-pheny1-2,2':6',2 ''-terpyridine, and B is a phenanthroline base, viz., 1,10-phenanthroline (phen, 1), dipyridoquinoxaline (dpq, 2), and dipyridophenazine (dppz, 3), were prepared and structurally characterized, and their DNA binding, photoactivated DNA cleavage activity, and cytotoxic properties were studied [Fe = (eta(5)-C5H4)Fe-11(eta(5)-C5H5)]. Complexes 1 and 3 as hexafluorophosphate salts were structurally characterized by X-ray crystallography. Molecular structures of [Cu(Fc-tpy)(phen)](PF6)(2) (1a) and [Cu(Fc-tpy)(dppz)](PF6)(2)center dot MeCN (3a center dot MeCN) show a distorted square-pyramidal geometry at copper(II), with the Fc-tpy ligand and the phenanthroline base showing respective tridentate and bidentate binding modes. The phenanthroline base exhibits axial-equatorial bonding, while the Fc-tpy ligand binds at the basal plane. The complexes showed quasi-reversible cyclic voltammetric responses near 0.45 and -0.3 V vs SCE in aqueous DMF-0.1 M KCl assignable to the Fc(+)-Fc and Cu(II) Cu(1) redox couples, respectively. The complexes bind to DNA, giving K-b values of 1.4 x 10(4) to 5.6 x 10(5) M-1 in the order 4 similar to 3 > 2 > 1. Thermal denaturation and viscometric titration data suggest groove and/or partial intercalative mode of DNA binding of the complexes. The complexes showed chemical nuclease activity in the presence of 3-mercaptopropionic acid (0.5 mM) or H2O2 (0.25 mM). Complexes 2-4 showed plasmid DNA cleavage activity in visible light, forming (OH)-O-center dot radicals. The Fc-tpy complex 3 showed better DNA photocleavage activity than its Ph-tpy analogue. The ferrocene moiety in the dppz complex 3 makes it more photocytotoxic than the Ph-tpy analogue 4 in HeLa cells.

Influence of phosphate ligands in abolishing the conformational difference between ribonuclease A and its acid-denatured derivative

The initial structural alteration of RNAase A due to acid denaturation (0.5 N HCl, 30 degrees C) that accompanies deamidation (without altering enzymic activity) has been dectected by spectrophotometric titration, fluorescence and ORD/CD measurements. It is shown that acid treated RNAase A has an altered conformation at neutral pH, 25 degrees C. This is characterized by the increased accessibility of buried tyrosine residue(s) towards the solvent. The most altered conformation of RNAase A is found in the 10 h acid-treated derivative. This has about 1.5 additional exposed tyrosine residues and a lesser amount of secondary structure than RNAase A. All three methods (titration, fluorescence and CD) established that the structural transition of RNAase A is biphasic. The first phase occurs within 1 h and the resulting subtle conformational change is constant up to 7 h. Following this, after the release of 0.55 mol of ammonia, the major conformational change begins. The altered conformation of the acid-denatured RNAase A could be reversed completely to the native state through a conformational change induced by substrate analogs like 2'- or 3'-CMP. Thus the monodeamidated derivative isolated from the acid-denatured RNAase A by phosphate is very similar to RNAase A in over-all conformation. The results suggest the possibility of flexibility in the RNAase A molecule that does not affect its catalytic activity, as probed through the tyrosine residues.

Vapor phase oxidation of p-xylene

The kinetics of the vapor phase oxidation of p-xylene over ferric molybdate catalyst were studied in an isothermal, differential, tubular flow reactor in the temperature range of 360 to 420° C. The major product obtained was p-tolualdehyde with small amounts of maleic anhydride and p-toluic acid. No terephthalic acid or CO2 were observed. The reaction rate data collected fit the redox model given by Equation 1. The values of activation energies Ex, Eo and frequency factors Ax, Ao obtained are 72, 63 kJ/mol and 0.64, 2.89 m3/kg catalyst s respectively. The reaction mechanism was established by studying the oxidation of p-tolualdehyde, toluic and terephthalic acids. It is concluded that the reaction follows a parallel-consecutive scheme. On a étudié la cinétique de l'oxydation, en phase gazeuse, du para-xylène sur un catalyseur consistant en molybdate ferrique; cette oxydation s'est faite dans un réacteur à écoulement tubulaire, isothermique et différentiel, dans une échelle de températures comprises entre 360°C et 420°C. Le produit principal obtenu a été le para-tolualdéhyde; on a aussi trouvé de faibles quantités d'anhydride maléique et d'acide para-toluique, mais on n'a pas noté la présence d'acide téréphtalique ni d'anhydride carbonique (CO2). Les résultats obtenus en ce qui a trait à la vitesse de réaction concordent bien avec les données du modèle redox indiquées par l'équation 1. Les valeurs des énergies d'activation Ex et Eo ainsi que des facteurs de fréquence Ax et Ao obtenus sont respectivement 72 et 63 kilojoules/mol. et 0.64 × 103 et 2.89 m3/kg de catalyseur. On a établi le mécanisme de la réaction en étudiant l'oxydation du para-tolualdéhyde et des acides toluique et téréphtalique. On conclut que la réaction se fait d'une manière parallèle et consécutive.

Kinetics and mechanism of thermal decomposition of tetramethylammonium nitrate

The mechanism of thermal decomposition of tetramethylammonium nitrate has been investigated by thermogravimetry and mass spectrometry. The activation energy for the decomposition has been determined by isothermal decomposition technique using thermogravimetry and by monitoring mass spectrometrically the formation of trimethylamine. The activation energies determined in both the cases compare well, suggesting that the decomposition proceeds via dissociation of tetramethylammonium nitrate into trimethylamine and methylnitrate.

Effect of Storage Temperatures on the Mechanical Properties of the Composite Solid Propellants

Accelerated ageing studies for three composite propellant formulations, namely polystyrene (PS)/ ammonium perchlorate (AP), polymethylmethacrylate (PMMA)/AP and poly phenol formaldehyde (PPF)/AP have been carried out in the temperature range of 55-125°C. Measurements of the ultimate compression strength (Uc) and isothermal decomposition rate (TD rate) were monitored as a function of storage time and temperature. The change in Uc was found to be linearly dependent on the change in TD rate irrespective of the propellant systems. Analysis of the results further revealed that the cause of ageing for both Uc and burning rate (r) is the thermal decomposition of the propellant. The safe-life for the change in mechanical properties was found to be higher compared to the change in r for PS and PMMA based propellants.

Experimental studies and phase field modeling of microstructure evolution during solidification with electromagnetic stirring

Thixocasting requires manufacturing of billets with non-dendritic microstructure. Aluminum alloy A356 billets were produced by rheocasting in a mould placed inside a linear electromagnetic stirrer. Subsequent heat treatment was used to produce a transition from rosette to globular microstructure. The current and the duration of stirring were explored as control parameters. Simultaneous induction heating of the billet during stirring was quantified using experimentally determined thermal profiles. The effect of processing parameters on the dendrite fragmentation was discussed. Corresponding computational modeling of the process was performed using phase-field modeling of alloy solidification in order to gain insight into the process of morphological changes of a solid during this process. A non-isothermal alloy solidification model was used for simulations. The morphological evolution under such imposed thermal cycles was simulated and compared with experimentally determined one. Suitable scaling using the thermosolutal diffusion distances was used to overcome computational difficulties in quantitative comparison at system scale. The results were interpreted in the light of existing theories of microstructure refinement and globularisation.

Chiral gels derived from secondary ammonium salts of (1R, 3S)-(+)-camphoric acid

In order to have access to chiral gels, a series of salts derived from (1R, 3S)-(+)-camphoric acid and various secondary amines were prepared based on supramolecular synthon rationale. Out of seven salts prepared, two showed moderate gelation abilities. The gels were characterized by differential scanning calorimetry, table top rheology, scanning electron microscopy, single crystal and powder X-ray diffraction. Structure property correlation based on X-ray diffraction techniques remain inconclusive indicating that some of the integrated part associated with the gelation phenomena requires a better understanding.

Conformations of synthetic alamethicin fragments. Evidence for 310 helical folding from 270-MHz hydrogen-1 nuclear magnetic resonance and circular dichroism studies

IH NMR studies at 270 MHz on the synthetic alamethicin fragments Z-Aib-Pro-Aib-Ala-Aib-Ala-OMe (1-6), Boc-Gln-Aib-Val-Aib-Gly-Leu-Aib-OMe (7-1 3), Boc-Leu-Aib-Pro-Val-Aib-OMe (1 2-16), and Boc-Gly-Leu- Aib-Pro-Val-Aib-OMe (1 1-16) have been carried out in CDC13 and (CD3)2S0. The intramolecularly hydrogen bonded amide hydrogens in these peptides have been delineated by using solvent titration experiments and temperature coefficientsof NH chemical shifts in (CD3)+30. All the peptides adopt highly folded structures, characterized by intramolecular 4 - 1 hydrogen bonds. The 1-6 fragment adopts a 310 helical conformation with four hydrogen bonds, in agreement with earlier studies (Rao, Ch. P., Nagaraj, R., Rao, C. N. R., & Balaram, P. (1980) Biochemistry 19, 425-4311. The 7-13

Heating values of mature trees.

The effective heating values of the above and below ground biomass components of mature Scots pine (Pinus sylvestris), Norway spruce (Picea abies), downy birch (Betula pubescens), silver birch (Betula pendula), grey alder (Alnus incana), black alder (Alnus glutinosa) and trembling aspen (Populus tremula) were studied. Each sample tree was divided into wood, bark and foliage components. Bomb calorimetry was used to determine the calorimetric heating values. The species is a significant factor in the heating value of individual tree components. The heating value of the wood proper is highest in conifers. Broad-leaved species have a higher heating value of bark than conifers. The species factor diminishes when the weighted heating value of crown, whole stems or stump-root-system are considered. The crown material has a higher heating value per unit weight in comparison with fuelwood from small-sized stems or wholetrees. The additional advantages of coniferous crown material are that it is a non-industrial biomass resource and is readily available. The variability of both the chemical composition and the heating value is small in any given tree component of any species. However, lignin, carbohydrate and extractive content were found to vary from one part of the tree to another and to correlate with the heating value.