Shielding of ionic interactions by sulfur dioxide in an ionic liquid

The effect of adding SO(2) on the structure and dynamics of 1-butyl-3-methylimidazolium bromide (BMIBr) was investigated by low-frequency Raman spectroscopy and molecular dynamics (MD) simulations. The MD simulations indicate that the long-range structure of neat BMIBr is disrupted resulting in a liquid with relatively low viscosity and high conductivity, but strong correlation of ionic motion persists in the BMIBr-SO(2) mixture due to ionic pairing. Raman spectra within the 5 < omega < 200 cm(-1) range at low temperature reveal the short-time dynamics, which is consistent with the vibrational density of states calculated by MD simulations. Several time correlation functions calculated by MD simulations give further insights on the structural relaxation of BMIBr-SO(2).

Evaluation of intramolecular energy transfer process in the lanthanide(III) bis- and tris-(TTA) complexes: Photoluminescent and triboluminescent behavior

This work reports the energy transfer mechanism process of [Eu(TTA)(2)(NO(3))(TPPO)(2)] (bis-TTA complex) and [Eu(TTA)(3)(TPPO)(2)] (tris-TTA complex) based on experimental and theoretical spectroscopic properties, where TTA = 2-thienoyltrifluoroacetone and TPPO = triphenylphosphine oxide. These complexes were synthesized and characterized by elemental analyses, infrared spectroscopy and thermogavimetric analysis. The theoretical complexes geometry data by using Sparkle model for the calculation of lanthanide complexes (SMLC) is in agreement with the crystalline structure determined by single-crystal X-ray diffraction analysis. The emission spectra for [Gd(TTA)(3)(TPPO)(2)] and [Gd(TTA)(2) (NO(3))(TPPO)(2)] complexes are associated to T -> S(0) transitions centered on coordinated TTA ligands. Experimental luminescent properties of the bis-TTA complex have been quantified through emission intensity parameters Omega(lambda)(lambda = 2 and 4), spontaneous emission rates (A(rad)), luminescence lifetime (tau), emission quantum efficiency (eta) and emission quantum yield (q), which were compared with those for tris-TTA complex. The experimental data showed that the intensity parameter value for bis-TTA complex is twice smaller than the one for tris-TTA complex, indicating the less polarizable chemical environment in the system containing nitrate ion. A good agreement between the theoretical and experimental quantum yields for both Eu(Ill) complexes was obtained. The triboluminescence (TL) of the [Eu(TTA)(2)(NO(3))(TPPO)(2)] complexes are discussed in terms of ligand-to-metal energy transfer. (c) 2007 Elsevier B.V. All fights reserved.

Electrodeposition and characterization of thin selenium films modified with lead ad-atoms

The deposition and characterization of Se films doped with Pb underpotentially deposited (UPD) ad-atoms was studied in this work. The employed experimental techniques were cyclic voltammetry, chronoamperometry, electrochemical impedance spectroscopy, UV-vis spectroscopy and atomic force microscopy. The initial deposition of Se film by chronoamperometry yielded a thin film composed of approximately 700 layers. The Pb UPD on Se was achieved by chronoamperometry in a potential value previously determined in voltammetric experiments. This deposition yielded a deposition charge of approximately 7.5% of the total one. The film resistance altered from 320 Omega cm(2) for Se to 65 Omega cm(2) for the Se/Pb one. Flat band potential values and number of acceptors and donors were also calculated for both films and the values obtained were + 0.95 and -0.51 V for Se and Se/Pb, respectively. The Se coating presented 1.2 x 10(17) cm(3) acceptors while the Se/Pb one presented 3.2 x 10(17) cm(3) donors. The band gap values for both films were 2.4 eV and 1.9 eV, correspondingly. (C) 2008 Elsevier B.V. All rights reserved.

Electrocatalytic behavior of glassy carbon electrodes modified with multiwalled carbon nanotubes and cobalt phthalocyanine for selective analysis of dopamine in presence of ascorbic acid

This work describes the development, electrochemical characterization and utilization of a cobalt phthalocyanine modified carbon nanotube electrode for the quantitative determination of dopamine in 0.2 mol L-1 phosphate buffer contaminated with high concentration of ascorbic acid. The electrode surface was analyzed by cyclic voltammetry and electrochemical impedance spectroscopy which showed a modified surface presenting a charge transfer resistance of 500 Omega, against the 16.46 k Omega value found for the bare glassy carbon surface. A pseudo rate constant value of 5.4 x 10(-4) cm s(-1) for dopamine oxidation was calculated. Voltammetric experiments showed a shift of the peak potential of DA oxidation to less positive value at 390 mV as compared with that of a bare GC electrode at 570 mV. The electrochemical determination of dopamine, in presence of ascorbic acid in concentrations up to 0.1 mol L-1 by differential pulse voltarnmetry, yielded a detection limit as low as 2.56 x 10(-7) mol L-1.

Effects of starch gelatinization and oxidation on the rheological behavior of chitosan/starch blends

Chitosan/starchblends represent an interesting alternative for the preparation of biocompatible drug delivery systems, packing materials and edible films. This paper reports on the effects of starch gelatinization and oxidation on the rheological behavior of chitosan/starch blends. The results show that the modifications in the starch structure cause changes in G` (storage modulus) and G `` (lossmodulus) as a function of frequency. For chitosan/starch, G `` is higher than G`, showing a viscous behavior. However, for chitosan/gelatinized starch and chitosan/oxidized starch, an increase in the angular frequency promotes a modulus crossover at omega = 0.02 and 0.04 rad s(-1), respectively. The viscosity curves as a function of shear rate show that both modifications cause an increase in viscosity, and all blends show a non-Newtonian behavior. (C) 2011 Society of Chemical Industry

A quantum chemical study on a set of non-imidazole H(3) antihistamine molecules

Molecular orbital calculations were carried out on a set of 28 non-imidazole H(3) antihistamine compounds using the Hartree-Fock method in order to investigate the possible relationships between electronic structural properties and binding affinity for H3 receptors (pK(i)). It was observed that the frontier effective-for-reaction molecular orbital (FERMO) energies were better correlated with pK(i) values than highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy values. Exploratory data analysis through hierarchical cluster (HCA) and principal component analysis (PCA) showed a separation of the compounds in two sets, one grouping the molecules with high pK(i) values, the other gathering low pK(i) value compounds. This separation was obtained with the use of the following descriptors: FERMO energies (epsilon(FERMO)), charges derived from the electrostatic potential on the nitrogen atom (N(1)), electronic density indexes for FERMO on the N(1) atom (Sigma((FERMO))c(i)(2)). and electrophilicity (omega`). These electronic descriptors were used to construct a quantitative structure-activity relationship (QSAR) model through the partial least-squares (PLS) method with three principal components. This model generated Q(2) = 0.88 and R(2) = 0.927 values obtained from a training set and external validation of 23 and 5 molecules, respectively. After the analysis of the PLS regression equation and the values for the selected electronic descriptors, it is suggested that high values of FERMO energies and of Sigma((FERMO))c(i)(2), together with low values of electrophilicity and pronounced negative charges on N(1) appear as desirable properties for the conception of new molecules which might have high binding affinity. 2010 Elsevier Inc. All rights reserved.

Quantum control of electromagnetically induced transparency dispersion via atomic tunneling in a double-well Bose-Einstein condensate

Electromagnetically induced transparency (EIT) is an important tool for controlling light propagation and nonlinear wave mixing in atomic gases with potential applications ranging from quantum computing to table top tests of general relativity. Here we consider EIT in an atomic Bose-Einstein condensate (BEC) trapped in a double-well potential. A weak probe laser propagates through one of the wells and interacts with atoms in a three-level Lambda configuration. The well through which the probe propagates is dressed by a strong control laser with Rabi frequency Omega(mu), as in standard EIT systems. Tunneling between the wells at the frequency g provides a coherent coupling between identical electronic states in the two wells, which leads to the formation of interwell dressed states. The macroscopic interwell coherence of the BEC wave function results in the formation of two ultranarrow absorption resonances for the probe field that are inside of the ordinary EIT transparency window. We show that these new resonances can be interpreted in terms of the interwell dressed states and the formation of a type of dark state involving the control laser and the interwell tunneling. To either side of these ultranarrow resonances there is normal dispersion with very large slope controlled by g. We discuss prospects for observing these ultranarrow resonances and the corresponding regions of high dispersion experimentally.

α,ω-Bis(trichlorostannyl)alkanes: unravelling the hydrolysis pathway to organotin-oxo oligomers

New α,&omega;-bis(trichlorostannyl)alkanes, Cl₃Sn(CH₂)_nSnCl₃ [n = 3-5, 8], have been synthesized via tin-phenyl bond cleavage reactions on α,&omega;-bis(triphenylstannyl)alkanes, Ph₃Sn(CH₂)_nSnPh₃ [n = 3-5, 8], using either SnCl₄ or concentrated hydrochloric acid. Some key missing links, (H₂O)Cl₃Sn(CH₂)₃SnCl₃(H₂O) (1a) and (H₂O)₂Cl₃Sn(CH₂)₃SnCl₃(H₂O)₂ (6), in the hydrolysis pathway of organotin trichlorides were identified. Crystal structures of the nonassociated di-tin compounds (H₂O)Cl₃Sn(CH₂)₃SnCl₃(H₂O) (1a) and (H₂O)₂Cl₃Sn(CH₂)₃SnCl₃(H₂O)₂ (6, isolated as the 18-crown-6 cocrystal acetonitrile solvate) as well as the polymeric hydrolysis product [H₂O(OH)Cl₂Sn(CH₂)₃SnCl₂(OH)H₂O·₂H2O]_n (7·2H₂O) are reported.

The architectural edifice and the phantoms of history

Starting with the literal and physical role of the "ground," this article attempts to bring this "ground" into a discursive arena. In particular, the author is thinking about the period at the end of a war, the period in between destruction and reconstruction, exemplified in some classic postwar films in which the architecture of the city is in a state of ruin—deformed, eroded, and dark—but there is no further destruction. The article calls this period "a gap of history" and its investigation is set against a claim that architecture is a reconstructive practice, that it is enlightening and aspiring. History, on the other hand, is captured by scenes of the battlefield and dominated by a narrative of war and destruction. The article makes reference to the real and fantasy desire for destruction (war and history) and reconstruction (architecture), and how through the connecting plane of the ground architecture is entangled in war and history of destruction as it figures in reconstruction. Architecture is contingent on history as discursive—history that is not unified, fixed, or evolutionary but rather contested and rewritten within a conflictual battlefield.

Nitric oxide control of the dorsal aorta and the intestinal vein of the Australian short-finned eel Anguilla australis

This study investigated the mechanisms by which nitric oxide (NO) regulates the dorsal aorta and the intestinal vein of the Australian short-finned eel Anguilla australis. NADPH diaphorase histochemistry and immunohistochemistry using a mammalian endothelial nitric oxide synthase (NOS) antibody could not demonstrate NOS in the endothelium of either blood vessel; however, NOS could be readily demonstrated in the endothelium of the rat aorta that was used as a control. Both blood vessels contained NADPH diaphorase positive nerve fibres and nerve bundles, and immunohistochemistry using a neural NOS antibody showed a similar distribution of neural NOS immunoreactivity in the perivascular nerves. In vitro organ bath physiology showed that a NO/soluble guanylyl cyclase (GC) system is present in the dorsal aorta and the intestinal vein, since the soluble GC inhibitor oxadiazole quinoxalin^-1 (ODQ; 10^–5 mol l^–1) completely abolished the vasodilatory effect of the NO donor, sodium nitroprusside (SNP; 10^–4 mol l^–1). In addition, nicotine (3x10^–4 mol l^–1) mediated a vasodilation that was not affected by removal of the endothelium. The nicotine-mediated dilation was blocked by the NOS inhibitor, N&omega;-nitro-arginine (L-NNA; 10^–4 mol l^–1), and ODQ (10^–5 mol l^–1). More specifically, the neural NOS inhibitor, N&omega;-propyl-L-arginine (10^–5 mol l^–1), significantly decreased the dilation induced by nicotine (3x10^–4 mol l^–1). Furthermore, indomethacin (10^–5 mol l^–1) did not affect the nicotine-mediated dilation, suggesting that prostaglandins are not involved in the response. Finally, the calcium ionophore A23187 (3x10^–6 mol l^–1) caused an endothelium-dependent dilation that was abolished in the presence of indomethacin. We propose the absence of an endothelial NO system in eel vasculature and suggest that neurally derived NO contributes to the maintenance of vascular tone in this species. In addition, we suggest that prostaglandins may act as endothelially derived relaxing factors in A. australis.

Synthesis and structure of new oligomethylene-bridged double ladders. How far can the layers be separated?

The synthesis of the α,&omega;-bis[dichloro(trimethylsilylmethyl)stannyl]alkanes, (Me₃SiCH₂)C1₂Sn(CH₂)_nSnCl₂(CH₂SiMe₃) (13, n=5; 14, n=6; 15, n=7; 16, n=8; 17, n=10; 18, n=12) and the corresponding oligomethylene-bridged diorganotin oxides [(Me₃SiCH₂)(O)Sn(CH₂)_nSn(O)(CH₂SiMe₃)]_m (19, n=5; 20, n=6; 21, n=7; 22, n=8; 23, n=10; 24; n=12) is reported. The reaction of the diorganodichlorostannanes 13–18 with the corresponding diorganotin oxides 19–24 provided the spacer-bridged tetraorganodistannoxanes {[(Me₃SiCH₂)ClSn(CH₂)_nSnCl(CH₂SiMe₃)]O}₄ (25, n=5; 26, n=6; 27, n=7; 28, n=8; 29, n=10; 30, n=12). Compounds 13–30 have been identified by elemental analyses and multinuclear NMR spectroscopy. Compounds 25, 27, 29 and 30 have also been characterised by single crystal X-ray diffraction analysis and electrospray mass spectrometry. For the latter the essential double ladder motif is maintained for all n in the solid state, but subtle changes in alignment of the ladder planes occur. Separation between the two layers of the double ladder ranges from approx. 8.7  Å (for 25, n=5) to approx. 15 Å (for 30, n=12). In solution there is some dissociation of the double ladders into the corresponding dimers. The degree of dissociation is favoured by increasing oligomethylene chain length n.

Variation in the fatty acid composition of the blubber in Cape fur seals (Arctocephalus pusillus pusillus) and the implications for dietary interpretation

Analysis of the fatty acid (FA) composition of blubber is a valuable tool in interpreting the diet of marine mammals. This technique is based on the principle that particular FA present in prey can be incorporated largely untransformed into predator adipose tissue stores, thereby providing biochemical signatures with which to identify prey species. Several studies of phocid seals and cetaceans have documented vertical stratification in the FA composition of blubber such that inferences about diet may vary greatly depending on the layer of the blubber that is analysed. It is not known whether blubber in otariid seals (fur seals and sea lions) also displays vertical stratification in FA composition. Furthermore, it is not known whether the FA composition of blubber is uniform in these species. In the present study, the vertical and regional variation in FA composition of blubber was investigated in seven adult female Cape fur seals (Arctocephalus pusillus pusillus). The proportion of monounsaturated fatty acids (MUFA) was greater in the outer (43.6±1.3%) than inner portion (40.9±1.2%; t20=5.59, P<0.001) whereas the proportions were greater in the inner than outer portions for saturated fatty acids (23.6±0.5% and 21.9±0.6%, respectively, t20 = 5.31, P<0.001) and polyunsaturated fatty acids (PUFA, 35.5±0.7% and 34.5±0.7%, respectively, t20 = 3.81, P < 0.001). There was an inverse relationship between MUFA and PUFA in the blubber, independent of sampling location. In addition, with the exception of the inner portion from non-lactating females, blubber from the mammary area had the highest proportions of 18:1&omega;9c and total MUFA, followed by blubber from the rump and neck, suggesting that the deposition and mobilisation of blubber lipids may not be uniform around the body in otariid seals. These results support the need for blubber tissue to be sampled from the same site on animals, and to the full depth of the blubber layer, to minimise variation in FA profiles that could occur if different sites and depths were sampled. Such standardisation of sampling will further aid in interpreting diet in otariid seals using the FA Signature Analysis approach.

Polymerising pyrrole on polyester textiles and controlling the conductivity through coating thickness

The surface resistance of polypyrrole (PPy)-coated polyester fabrics was investigated and related to coating thickness, which was controlled by adjusting the reactant concentrations. The thickness of the coating initially increased rapidly followed by a steady increase when the concentration of pyrrole (Py) was larger than a concentration of approximately 0.4 mg/ml. The surface resistance decreased from 10⁶ to 10³ &Omega; with increase in pyrrole concentration within 0.2 mg/ml until the concentration reached a value of about 0.4 mg/ml, above which the rate of decrease diminished. The effect of initial treatment with monomer or oxidant prior to polymerisation reaction with regards to thickness and surface resistance was minimal. The immersion time of the textile into the monomer solution prior to polymerisation reaction did not have a significant effect on the abrasion resistance.

Conductive wool yarns by continuous vapour phase polymerization of pyrrole

Conducting polypyrrole (PPy) coated wool yarns were prepared by a continuous vapour polymerization technique, using a speed of 1 m/min with different iron(III) chloride (FeCl₃) as the oxidant at different concentrations. The resistivities, tensile properties, longitudinal and cross-sectional views of PPy-coated wool yarns were investigated. Optimum specific electrical resistances of 2.96 &Omega; g/cm² at 80 g/L FeCl₃ and 1.69 &Omega; g/cm² at 70 g/L FeCl₃ were obtained for 500 and 400 twist per meter (TPM) yarns, respectively. PPy-coated wool yarns exhibited higher elongation than uncoated yarns. Longitudinal and cross-sectional views of the yarns indicate that PPy coating penetrated deep into the yarn cross-section and a uniform coating was obtained on the surface of the yarn surface.

Synthesis and polymerisation of α,ω-bis(3-pyrrolyl)alkanes

The synthesis, characterisation and polymerisation studies of a homologous series of α,&omega;-bis(pyrrolyl)alkanes are described. These α,&omega;-bis(pyrrolyl)alkanes were produced using Friedel–Crafts acylation followed by reduction of the carbonyl group using Red-Al®. Chemical polymerisation of the resultant dimers using FeCl₃ produced poly(α,&omega;-bis(pyrrolyl)alkane) films, which were characterised by SEM, FTIR and tested for conductivity.