Adsorption characteristics of phenolic compounds onto coal-reject-derived adsorbents

Carbonaceous adsorbents were prepared by heat treatment of coal reject at 600 degrees C, after chemical treatment in HNO3, H2SO4, and NaOH at 25 and 75 degrees C. Pore structure characterization and the phenol adsorption capacities of the adsorbents showed that nitric acid pretreatment significantly enhanced the surface properties, consequently the adsorption capacities of the adsorbents. A number of samples were subsequently prepared by carbonizing coal reject at 600 degrees C, after pretreatment in HNO3 under various conditions. The acid concentration, residence time, and reaction temperature were varied to obtain adsorbents with various pore structures. The adsorption capacities of the derived adsorbents for phenol, p-nitrophenol, and benzene were measured to gain further insights into the pore structure evolution. Adsorption isotherms of phenol, p-nitrophenol, and p-chlorophenol on the best adsorbent prepared were determined and correlated with theoretical isotherm equations, such as the Langmuir, Freundlich, and Redlich-Peterson equations.

The crack tip strain field of AISI 4340 - Part III - Hydrogen influence

This paper studied the influence of hydrogen and water vapour environments on the plastic behaviour in the vicinity of the crack tip for AISI 4340. Hydrogen and water vapour (at a pressure of 15 Torr) significantly increased the crack tip opening displacement. The crack tip strain distribution in 15 Torr hydrogen was significantly different to that measured in vacuum. In the presence of sufficient hydrogen, the plastic zone was larger, was elongated in the direction of crack propagation and moreover there was significant creep. These observations support the hydrogen enhanced localised plasticity model for hydrogen embrittlement in this steel. The strain distribution in the presence of water vapour also suggests that SCC in AISI 4340 occurs via the hydrogen enhanced localised plasticity mechanism. (C) 1999 Kluwer Academic Publishers.

Electrochemistry of macrocyclic cobalt(III/II) hexaamines: Electrocatalytic hydrogen evolution in aqueous solution

The macrocyclic cobalt hexaamines [Co(trans-diammac)](3+) and [Co(cis-diammac)](3+) (diammac = 6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine) are capable of reducing the overpotential for hydrogen evolution on a mercury cathode in aqueous solution. Protons are reduced in a catalytic process involving reoxidation of the Co-II species to its parent Co-III complex. The cycle is robust at neutral pH with no decomposition of catalyst. The stability of the [Co(trans-diammac)](2+) and [Co(cis-diammac)](2+) complexes depends on the pH of the solution and the coordinating properties of the supporting electrolyte. Electrochemical studies indicate that the adsorbed Co-II complex on the surface of mercury is the active catalyst for the reduction of protons to dihydrogen.

Bonding effects and the crystal structures of (NH4)(2)[Cu(H2O)(6)](SO4)(2) and its (H2O)-O-18 substituted form at 9.5 K

The crystal structures of the Tutton salts (NH4)(2)[Cu(H2O)(6)](SO4)(2), diammonium hexaaquacopper disulfate, formed with normal water and isotopically substituted (H2O)-O-18, have been determined by X-ray diffraction at 9.5 K and are very similar, with Cu-O(7) the longest of the Cu-O bonds of the Jahn-Teller distorted octahedral [Cu(H2O)(6)](2+) complex. It is known that structural differences accompany deuteration of (NH4)(2)[Cu(H2O)(6)](SO4)(2), the most dramatic of which is a switch to Cu-O(8) as the longest such bond. The present result suggests that the structural differences are associated with hydrogen-bonding effects rather than with increased mass of the water ligands affecting the Jahn-Teller coupling. The Jahn-Teller distortions and hydrogen-bonding contacts in the compounds are compared with those reported for other Tutton salts at ambient and high pressure.

Mesoionic pyridopyrimidinylium and pyridooxazinylium olates and non-mesoionic pyridopyrimidinones. Structures in the solid state, solution, and matrices

X-Ray crystal structures, C-13 NMR spectra and theoretical calculations (B3LYP/6-31G*) are reported for the mesoionic (zwitterionic) pyridopyrimidinylium- and pyridooxazinyliumolates 2a, 3a and 5a,b as well as the enol ether 11b and the enamine 11c. The 1-NH compounds like 1a, 2a and 3a exist in the mesoionic form in the crystal and in solution, but the OH tautomers such as 1b and 2b dominate in the gas phase as revealed by the Ar matrix IR spectra in conjunction with DFT calculations. All data indicate that the mesoionic compounds can be regarded as intramolecular pyridine-ketene zwitterions (cf. 16 --> 17) with a high degree of positive charge on the pyridinium nitrogen, a long pyridinium N-CO bond (ca. 1.44-1.49 Angstrom), and normal C=O double bonds (ca. 1.22 Angstrom). All mesoionic compounds exhibit a pronounced tilting of the olate C=O groups (the C=O groups formally derived from a ketene) towards the pyridinium nitrogen, giving NCO angles of 110-118 degrees. Calculations reveal a hydrogen bond with 6-CH, analogous to what is found in ketene-pyridine zwitterions and the C3O2-pyridine complex. The 2-OH tautomers of type 1b, 2b, and 11 also show a high degree of zwitterionic character as indicated by the canonical structures 11 12.

Oxidation of oxa and thia fatty acids and related compounds catalysed by 5-and 15-lipoxygenase

The modified fatty acids, (Z,Z,Z)-(octadeca-6,9,12-trienyloxy)acetic acid, (Z,Z,Z)-(octadeca-9,12,15-trienyloxy)acetic acid, (all-Z)-(eicosa-5,8,11,14-tetraenyloxy)acetic acid, (all-Z)-(eicosa-5,8,11,14-tetraenylthio)acetic acid, 3-[(all-Z)-(eicosa-5,8,11,14-tetraenylthio)]propionic acid, (all-Z)-(eicosa-5,8,11,14-tetraenylthio)succinic acid, N-[(all-Z)-(eicosa-5,8,11,14-tetraenoyl)]glycine and N-[(all-Z)-(eicosa-5,8,11,14-tetraenoyl)]aspartic acid, all react with soybean 15-lipoxygenase. The products were treated with triphenylphosphine to give alcohols, which were isolated using HPLC. Analysis of the alcohols using negative ion tandem electrospray mass spectrometry, and by comparison with compounds obtained by autoxidation of arachidonic acid, shows that each enzyme catalysed oxidation occurs at the omega -6 position of the substrate. In a similar fashion, it has been found that (Z,Z,Z)-(octadeca-6,9,12-trienyloxy)acetic acid, (Z,Z,Z)-(octadeca-9,12,15-trienyloxy)acetic acid, (all-Z)-(eicosa-5,8,11,14-tetraenylthio)acetic acid and N-[(all-Z)-(eicosa-5,8, 11.14-tetraenylthio)]propionic acid each undergoes regioselective oxidation at the carboxyl end of the polyene moiety on treatment with potato 5-lipoxygenase. Neither (all-Z)-(eicosa-5,8,11,14-tetraenylthio)succinic acid nor N-[(all-Z)-(eicosa-5,8,11,14-tetraenoyl)]aspartic acid reacts in the presence of this enzyme, while N-[(all-Z)-(eicosa-5,8,11,14-tetraenoyl)]glycine affords the C11' oxidation product. The alcohol derived from (Z,Z,Z)-(octadeca-6,9, 12-trienyloxy)acetic acid using the 15-lipoxygenase reacts at the C6' position with the 5-lipoxygenase. (C) 2001 Elsevier Science Ltd. All rights reserved.

A dual catalyst bed system for the elimination of hydrogen from CO2 feed gas in urea synthesis

A dual catalyst bed system (Au/Fe2O3 + Pt-Pd/Al2O3) for eliminating hydrogen from the CO2 feed gas in urea synthesis is found to be far superior to commercially available and patented catalysts in catalytic activity. At relatively low temperatures, hydrogen is eliminated and coexistent CO is also oxidized completely to useful CO2. This can avoid effectively the accidental explosion of hydrogen-oxygen-ammonia mixed gases, thus ensuring the safety of urea synthesis.

The neutral hydrogen content of Fornax cluster galaxies

We present a new set of deep H I observations of member galaxies of the Fornax cluster. We detected 35 cluster galaxies in H I. The resulting sample, the most comprehensive to date, is used to investigate the distribution of neutral hydrogen in the cluster galaxies. We compare the H I content of the detected cluster galaxies with that of field galaxies by measuring H I mass-to-light ratios and the H I deficiency parameter of Solanes et al. (1996). The mean H I mass-to-light ratio of the cluster galaxies is 0.68 +/- 0.15, significantly lower than for a sample of H I-selected field galaxies (1.15 +/- 0.10), although not as low as in the Virgo cluster (0.45 +/- 0.03). In addition, the H I content of two cluster galaxies (NGC1316C and NGC1326B) appears to have been affected by interactions. The mean H I deficiency for the cluster is 0.38 +/- 0.09 (for galaxy types T = 1-6), significantly greater than for the field sample (0.05 +/- 0.03). Both these tests show that Fornax cluster galaxies are H I-deficient compared to field galaxies. The kinematics of the cluster galaxies suggests that the H I deficiency may be caused by ram-pressure stripping of galaxies on orbits that pass close to the cluster core. We also derive the most complete B-band Tully-Fisher relation of inclined spiral galaxies in Fornax. A subcluster in the South-West of the main cluster contributes considerably to the scatter. The scatter for galaxies in the main cluster alone is 0.50 mag, which is slightly larger than the intrinsic scatter of 0.4 mag. We use the Tully-Fisher relation to derive a distance modulus of Fornax relative to the Virgo cluster of -0.38 +/- 0.14 mag. The galaxies in the subcluster are (1.0 +/- 0.5) mag brighter than the galaxies of the main cluster, indicating that they are situated in the foreground. With their mean velocity 95 km s(-1) higher than that of the main cluster we conclude that the subcluster is falling into the main Fornax cluster.

Copper/MCM-41 as catalyst for photochemically enhanced oxidation of phenol by hydrogen peroxide

Heterogeneous copper catalyst was developed using the mesoporous molecular sieve MCM-41 as the catalyst support. Copper was impregnated onto the support. Catalysts with different copper loadings were obtained. The performance of the developed catalysts was evaluated in photochemically enhanced oxidation of phenol using hydrogen peroxide as the oxidant. The catalyst was found to significantly increase the oxidation rate and enhance the removal level of phenol with UV light present. The effects of copper loading on the catalyst, photo (UV), H2O2 concentration, and catalyst dosage on the photo-oxidation of phenol were studied. (C) 2001 Elsevier Science B.V. All rights reserved.

The large-scale distribution of neutral hydrogen in the Fornax region

Using data from the H I Parkes All Sky Survey (HIPASS), we have searched for neutral hydrogen in galaxies in a region similar to25x25 deg(2) centred on NGC 1399, the nominal centre of the Fornax cluster. Within a velocity search range of 300-3700 km s(-1) and to a 3sigma lower flux limit of similar to40 mJy, 110 galaxies with H I emission were detected, one of which is previously uncatalogued. None of the detections has early-type morphology. Previously unknown velocities for 14 galaxies have been determined, with a further four velocity measurements being significantly dissimilar to published values. Identification of an optical counterpart is relatively unambiguous for more than similar to90 per cent of our H I galaxies. The galaxies appear to be embedded in a sheet at the cluster velocity which extends for more than 30degrees across the search area. At the nominal cluster distance of similar to20 Mpc, this corresponds to an elongated structure more than 10 Mpc in extent. A velocity gradient across the structure is detected, with radial velocities increasing by similar to500 km s(-1) from south-east to north-west. The clustering of galaxies evident in optical surveys is only weakly suggested in the spatial distribution of our H I detections. Of 62 H I detections within a 10degrees projected radius of the cluster centre, only two are within the core region (projected radius

Identification of trail pheromone compounds from the labial glands of the stingless bee Geotrigona mombuca

Foragers of several species of stingless bees deposit pheromone spots in the vegetation to guide recruited nestmates to a rich food source. Recent studies have shown that Trigona and Scaptotrigona workers secrete these pheromones from their labial glands. An earlier report stated that species within the genus Geotrigona use citral from their mandibular glands for scent marking. Since convincing experimental proof for this conjecture is lacking, we studied the glandular origin of the trail pheromone of Geotrigona mombuca. In field bioassays, newly recruited bees were diverted by artificial scent trails that branched off from the natural scent trail deposited by their nestmates only when they were baited with extracts from the foragers` labial glands. Compounds extracted from the mandibular glands, however, did not release trail following behavior. This demonstrates that the trail pheromone of G. mombuca is produced in the labial glands, as in Trigona and Scaptotrigona. Furthermore, in chemical analyses citral was identified exclusively in the foragers` mandibular glands, which disproves its supposed role as a trail pheromone. The labial glands contained a series of terpene- and wax type esters, with farnesyl butanoate as major constituent. We, therefore, postulate that the trail pheromone of G. mombuca is composed of a blend of esters.

An insight into the thermostability of a pair of xylanases: the role of hydrogen bonds

Xylanases are enzymes that are very tolerant to temperature. Their potential use in several biotechnological applications, such as animal food manufacture and pulp bleaching, is due to their intrinsic thermostability. The present report deals with two xylanases, the mesophilic xylanase from Bacillus circulans, BCX, and the thermophilic xylanase from Thermomyces lanuginosus,TLX. These enzymes belong to family 11, and they are the most structurally similar mesophilic-thermophilic pair. Molecular dynamics simulations were employed to investigate the factors responsible for the different thermostabilities exhibited by these structurally similar enzymes. Their active site is their most rigid region, and it is equally rigid at all temperatures. Inter and intramolecular interactions, hydrogen bonds in particular, are the key to the main differences between BCX and TLX. The intramolecular hydrogen bonds and salt bridges are important for maintenance of the backbone rigidity even at high temperature, and the highly solvated surface is a clear optimization in TLX compared with BCX. The main differences between these two enzymes can be found on the fingers domain, which indicates that this domain must be the target for the site-directed mutagenesis responsible for improving the temperature tolerance of this family of enzymes.

Synthesis and spectral investigation of Al(III) catechin/beta-cyclodextrin and Al(III) quercetin/beta-cyclodextrin inclusion compounds

Al-catechin/beta-cyclodextrin and Al-quercetin/beta-cyclodextrin (beta-CD) inclusion compounds were synthesized and characterized by IR, UV-vis, H-1 and C-13 NMR and TG and DTA analyses. Because quercetin is sparingly soluble in water, the stability constants of the Al-quercetin/beta-CD and Al-catechin/beta-CD compounds were determined by phase solubility studies. The A(L)-type diagrams indicated the formation of 1:1 inclusion compounds and allowed calculation of the stability constants. The thermodynamic parameters were obtained from the dependence of the stability constants on temperature and results indicated that the formation of the inclusion compounds is an enthalpically driven process. The thermal decomposition of the solid Al-quercetin/beta-CD and Al-catcchin/beta-CD inclusion compounds took place at different stages, compared with the respective precursors, proving that an inclusion complexation process really occurred. (C) 2007 Published by Elsevier B.V.

Fermentative production of hydrogen from cassava processing wastewater by Clostridium acetobutylicum

This work reports on the effect of initial substrate concentration on COD consumption, pH, and H(2) production during cassava processing wastewater fermentation by Clostridium acetobutylicum ATCC 824. Five initial COD wastewater concentrations, namely 5.0, 7.5, 10.7, 15.0, and 30.0 g/L, were used. The results showed that higher substrate concentrations (30.0 and 15.0 COD/L) led to lower H(2) yield as well as less efficient substrate conversion into H(2). On the other hand, initial COD concentrations of 10.7, 7.5 and 5 g/L furnished 1.34, 1.2 and 2.41 mol H(2)/mol glucose, with efficiency of glucose conversion into H(2) of 34, 30, and 60% (mol/mol), respectively. These results demonstrate that cassava processing wastewater, a highly polluting effluent, can be successfully employed as substrate for H(2) production by C acetobutylicum at lower COD concentrations. (C) 2011 Elsevier Ltd. All rights reserved.