bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis, Structure, and Properties of Biimidazole‐Chelated Arylruthenium Complexes
Authors: Panda Bikash Kumar , Sengupta Suman , Chakravorty Animesh 
Published: December 2003

AbstractBy reacting Ru(η2‐RL)(PPh3)2(CO)Cl (1) with excess 4,5‐dimethyl‐2,2′‐biimidazole (dmbi), organometallics of the type [Ru(η1‐RL)(PPh3)2(CO)(dmbi)](PF6) (2) have been isolated in excellent yield (η2‐RL is C6H2O‐2‐CHNHC6H4R(p)‐3‐Me‐5, η1‐RL is C6H2OH‐2‐CHNC6H4R(p)‐3‐Me‐5 and R is Me, OMe and Cl). In this process the dmbi ligand undergoes five‐membered chelation, the iminium‐phenolato function tautomerizes to the imine‐phenol function and the Schiff base performs a large rotation around the Ru−C bond. The crystal and molecular structure of [Ru(η1‐MeL)(PPh3)2(CO)(dmbi)](PF6)·CH2Cl2 is reported. For steric reasons the carbon monoxide ligand is located syn to the phenolic oxygen atom as opposed to anti in the precursor 1. In the hydrogen bonded imine‐phenol function the O−H, H···N, and N···O distances are 0.83(8), 1.77(8), and 2.552(6) Å, respectively, the O−H···N angle being 156(2)°. The Ru(dmbi) chelate along with the metallated carbon atom and the CO ligand define an equatorial plane from which the metallated aldimine fragment is rotated by 34.5° due to interligand repulsion. This results in two unequal [2.348(2) and 2.411(2) Å] Ru−P bonds and an apparent suppression of the trans influence of the metallated carbanionic site. The cation and anion in the complex are engaged in N−H···F and C−H···F hydrogen bonding, generating a centrosymmetric dimer in the lattice. One of the hydrogen bonds, characterized by H···F, 2.03(8) Å and N−H···F, 166(2)°, is particularly strong. Solutions of 2 absorb near 400 nm and emit near 460 nm with quantum yields and lifetimes of ca. 10−3 and ⩽ 20 ns, respectively. The emission, which probably involves the 3MLCT state incorporating a π*(dmbi) contribution, is peculiar to the coligation of η1‐RL and dmbi to bivalent ruthenium. In dichloromethane solution 2 displays a quasireversible 2+/2 couple near 0.70 V vs. SCE [2+ is the ruthenium(III) analogue of 2]. Coulometrically generated solutions of 2+ display a strong absorption near 400 nm and rhombic EPR spectra with g values near 2.55, 2.15, and 1.83. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Lanthanide Homobimetallic Triple‐Stranded Helicates: Insight into the Self‐Assembly Mechanism
Authors: Elhabiri Mourad , Hamacek Josef , Bünzli Jean‐Claude G. , Albrecht‐Gary Anne‐Marie 
Published: December 2003

AbstractThe self‐assembly mechanism leading to the exclusive formation of a triple‐stranded bimetallic helicate upon reaction of EuIII with a ditopic hexadentate ligand L bearing two carboxylate moieties has been fully elucidated in water for a wide range of [Eu]tot/[L]tot ratios. Using a fruitful combination of electrospray mass spectrometry, potentiometry, UV/Vis spectrophotometry, luminescence, and 1H NMR spectroscopy, the final product Eu2L3 and the intermediate species EuL2 and Eu2L2 have been characterised. The presence of terminal carboxylates in L significantly reduces the electrostatic repulsions of the coordination sites in Eu2L2 and Eu2L3 compared with the corresponding complexes formed with analogous neutral ligands and thus increases the stability of the L‐europium(III) complexes. Kinetic investigations carried out with an excess of L and with an excess of EuIII, show that the self‐assembly proceeds through either EuL2 or Eu2L intermediates depending on the experimental conditions and leads to a pre‐organized Eu2L2 complex by either a “braiding” or a “keystone” mechanism. In the last step, a fast and efficient wrapping of the third ligand strand leads to the target Eu2L3 helicate. The overall process is mainly governed by electrostatic interactions and proceeds via a key double stranded intermediate helicate Eu2L2. To the best of our knowledge, as a result of the fine‐tuning of the coordination properties of L, we present one of the most efficient and cooperative metal/ligand systems for the spontaneous organization of a bimetallic triple‐stranded structure. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Hg2+‐Selective Membrane Potentiometric Sensor Based on a Recently Synthesized Mercapto Compound
Authors: Bagheri Marzieh , Mashhadizadeh Mohammad Hossein , Razee Saied , Momeni Ahmad 
Published: December 2003

AbstractA new PVC membrane electrode for Hg(II) ion based on a recently synthesized mercapto compound of 2‐benzoylamino‐3‐(4‐chloro‐phenyl)‐thioacrylic acid S‐(2‐mercapto‐4‐methyl‐phenyl) ester is reported. The electrode exhibits a Nernstian response for Hg2+ ions over a wide concentration range (2.0×10−7–3.0×10−2 M) with a slope of 29 (±1). The limit of detection is 5.0×10−8 M. The proposed sensor revealed good selectivities over a wide variety of other cations include hard and soft metals. This electrode could be used in a pH range of 1.0–4.0. It was used as an indicator electrode in potentiometric titration of mercury(II) ions and can be used in the direct determination of Hg2+ in aqueous solutions.
Investigations into Heteropolyanions as Electrocatalysts for the Oxidation of Adrenaline
Authors: Dempsey Eithne , Kennedy Alan , Fay Nigel , McCormac Timothy 
Published: December 2003

AbstractThe electrocatalytic behavior of a group of metal substituted heteropolyanions towards the oxidation of adrenaline was investigated in solution studies using both UV/vis and electrochemical techniques. Of the metal (M′) substituted Dawson phosphotungstates ([P2W17O61M′]n−) examined, iron, copper and vanadium substituted compounds accelerated the oxidation of adrenaline to adrenochrome. Both UV and electrochemical data support this conclusion, though further studies are necessary in order to deduce the exact role the metal plays in this process. The results presented here will form the basis for more thorough investigations into heteropolyanions as catalysts for catecholamines in the immobilized phase with the ultimate development of a sensor for adrenaline.
Development of a Dual‐Band Amperometric Detector for Determination of Ascorbic Acid and Glucose
Authors: Paixão Thiago R. L. C. , Matos Renato Camargo , Bertotti Mauro 
Published: December 2003

AbstractA flow‐through system cell that allows the direct and simultaneous amperometric determination of ascorbic acid and glucose to be performed is described. The electrolytic cell in a thin layer configuration is composed of a gold and a copper‐modified electrode, polarized at −0.10 and 0.50 V, respectively. By using a 1 mol L−1NaOH solution as carrier electrolyte, amperometric data acquisition was performed simultaneously with a bipotentiostat and the results were analyzed by a multivariate calibration method. Measurements for two commercial pharmaceutical products were carried out without any pretreatment and showed a good correlation with data obtained by using recommended methods. The use of the device to the on‐line quantitative removal of interfering species at the copper electrode is also discussed.
Calculation of curved open channel flow using physical curvilinear non‐orthogonal co‐ordinates
Authors: Zhu1 Mu‐Lan , Shimizu Yasuyuki , Nishimoto Naoshi 
Published: December 2003

AbstractThere are two main difficulties in numerical simulation calculations using FD/FV method for the flows in real rivers. Firstly, the boundaries are very complex and secondly, the generated grid is usually very non‐uniform locally. Some numerical models in this field solve the first difficulty by the use of physical curvilinear orthogonal co‐ordinates. However, it is very difficult to generate an orthogonal grid for real rivers and the orthogonal restriction often forces the grid to be over concentrated where high resolution is not required. Recently, more and more models solve the first difficulty by the use of generalized curvilinear co‐ordinates (ξ,η). The governing equations are expressed in a covariant or contra‐variant form in terms of generalized curvilinearco‐ordinates (ξ,η). However, some studies in real rivers indicate that this kind of method has some undesirable mesh sensitivities. Sharp differences in adjacent mesh size may easily lead to a calculation stability problem oreven a false simulation result. Both approaches used presently have their own disadvantages in solving the two difficulties that exist in real rivers. In this paper, the authors present a method for two‐dimensional shallow water flow calculations to solve both of the main difficulties, by formulating the governing equations in a physical form in terms of physical curvilinear non‐orthogonal co‐ordinates (s,n). Derivation of the governing equations is explained, and two numerical examples are employed to demonstrate that the presented method is applicable to non‐orthogonal and significantly non‐uniform grids. Copyright © 2004 John Wiley & Sons, Ltd.
Oscillations of the siliceous imprint in the central Benguela Upwelling System from MIS 3 through to the early Holocene: the influence of the Southern Ocean
Authors: Romero O. , Mollenhauer G. , Schneider R. R. , Wefer G. 
Published: December 2003

AbstractBased on a high‐resolution analysis of the diatom signal and biogenic bulk components at site GeoB3606‐1 (25°S, off Namibia), we describe rapid palaeoceanographic changes in the Benguela Upwelling System (BUS) from early MIS 3 through to the early Holocene (55 000 to 7 000 14C yr BP). Coastal upwelling strongly varied at 25°S from MIS 3 through to MIS 2. The abrupt decrease in the accumulation rate of biogenic silica and diatoms from MIS 3 into MIS 2 records rapid oceanographic changes in the BUS off Namibia. During MIS 3, leakage of excess H4SiO4 acid from the Southern Ocean into low‐latitude surface waters, as indicated by the occurrence of Antarctic diatoms, enhanced the production of spores of Chaetoceros at the expense of calcareous phytoplankton. Furthermore, shallower Antarctic Intermediate Water (AAIW) would have enriched the thermocline off Namibia with silicate transported from the Southern Ocean. The strong decrease of the siliceous signal throughout MIS 2 represents a decrease in the nutrient input to the BUS, even though the diatom assemblage is still dominated by spores of the upwelling‐associated diatom genus Chaetoceros. Depletion of silicate in the thermocline from the onset of MIS 2 through to the early Holocene reflects the shutdown of AAIW injection from the Southern Ocean into the BUS, causing upwelled waters to become reduced in silicate, hence less favourable for diatom production. The deglaciation and early Holocene are characterised by the replacement of the upwelling‐associated flora by a non‐upwelling‐related diatom community, reflecting weakened upwelling, retraction of the seaward extension of the chlorophyll filament off Lüderitz, and dominance of warmer waters. Copyright © 2003 John Wiley & Sons, Ltd.
Anomalous behavior of the second and third harmonics generated by femtosecond Cr:forsterite laser pulses in SiC–polymer nanocomposite materials as functions of the SiC nanopowder content
Authors: Konorov S. O. , Akimov D. A. , Ivanov A. A. , Alfimov M. V. , Zabotnov S. V. , Sidorov‐Biryukov D. A. , Fedotov A. B. , Podshivalov A. A. , Fornarini L. , Carpanese M. , Avella M. , Errico M. E. , Fantoni R. , Zheltikov A. M. 
Published: December 2003

AbstractFemtosecond pulses of 1.25 µm Cr:forsterite laser radiation were used to study second‐ and third‐harmonic generation in silicon carbide nanopowders embedded in a poly(methyl methacrylate) (PMMA) film. Harmonic generation processes extend the analytical and sensing abilities of light‐scattering techniques, including Raman spectroscopy, offering a convenient and efficient approach to the analysis of nanocomposite materials where nanoparticles tend to agglomerate, masking informative features in Raman spectra. The second‐ and third‐harmonic yields are shown to display an anomalous, counterintuitive behavior as functions of the SiC nanopowder content in a polymer film. Whereas harmonic generation in polymer films with a high content of SiC nanocrystals is quenched by the absorption of agglomerating nanoparticles, the influence of absorption is less detrimental in nanocomposite films with a lower SiC content, leading to the growth of the second‐ and third‐harmonic yields. Nanocomposite films with a lower SiC content are also characterized by a higher breakdown threshold, allowing pump pulses with higher fluences to be applied for more efficient harmonic generation. Copyright © 2003 John Wiley & Sons, Ltd.
Time domain fingerprints of a ‘perpendicular’ rotational Raman band: formic acid studied by femtosecond degenerate four‐wave mixing
Authors: Riehn Christoph , Matylitsky Victor V. , Gelin Maxim F. 
Published: December 2003

AbstractFormic acid (HCOOH) vapor was studied by femtosecond degenerate four‐wave mixing (fs DFWM) and rotational recurrences of J‐, C‐ and K‐type were observed with this time‐resolved rotational spectroscopy. The occurrence of ΔK≠0 transitions can be rationalized with the different anisotropy (oblate vs prolate) of the polarizability and moments‐of‐inertia tensor. Based on comprehensive computer simulations with a general non‐rigid asymmetric rotor model, the experimental spectrum was reproduced very well. From the fitting to the data, rotational and centrifugal distortion constants and also information on the anisotropy of the polarizability tensor were obtained in good agreement with reference values. Copyright © 2003 John Wiley & Sons, Ltd.
Extended wavenumber domain collision‐induced Raman scattering by gaseous neon
Authors: Rachet F. , Chrysos M. , Lothon G. , Moszynski R. , Milet A. 
Published: December 2003

AbstractA joint experimental and theoretical study of depolarized, I∥(ν), binary collision‐induced Raman scattering spectra by gaseous room‐temperature neon was made. An absolute‐unit calibration of the measured scattering cross‐sections permitted a straightforward comparison of the data with cross‐sections obtained with quantum mechanics. A broad detuning domain was explored, reaching the far spectral wing at wavenumber shifts ν almost twice as large as those probed so far. A novel ab initio symmetry adapted perturbation theory pair‐anisotropy model was employed, yielding spectra in agreement with the experiment. Copyright © 2003 John Wiley & Sons, Ltd.
Effects of 1‐methylcyclopropene and gibberellic acid on ripening of Chinese jujube (Zizyphus jujuba M) in relation to quality
Authors: Jiang Weibo , Sheng Qiang , Jiang Yueming , Zhou Xiangjuan 
Published: December 2003

AbstractOverripening of Chinese jujube (Zizyphus jujuba M) fruit at the postharvest stage usually results in a dramatic decline in quality. The role of 1‐methylcyclopropene (1‐MCP) and gibberellic acid (GA) in fruit ripening of Chinese jujube during storage in relation to quality was investigated. Fruit ripening of jujube was significantly enhanced by ethylene, whereas rates of respiration and ethylene production of the fruit were reduced by 1‐MCP. Treatment with 1‐MCP or GA delayed the decreases in firmness and vitamin C and reduced the level of ethanol. Furthermore, the effectiveness of 1‐MCP was improved by replicate treatments during storage at 20 or 2 °C. In addition, treatment with GA + 1‐MCP resulted in additive beneficial effects on ripening inhibition of the fruit. Copyright © 2003 Society of Chemical Industry
Thermodynamics of Phase Behavior in PEO/P(EO‐b‐DMS) Homopolymer and Block Co‐Oligomer Mixtures under Pressure
Authors: Jiang Shichun , An Lijia , Jiang Bingzheng , Wolf Bernhard A. 
Published: December 2003

AbstractThe cloud‐point temperatures (Tcl's) of poly(ethylene oxide) (PEO) and poly(ethylene oxide)‐block‐polydimethylsiloxane (P(EO‐b‐DMS)) homopolymer and block‐oligomer mixtures were determined by turbidity measurements over a range of temperatures (105 to 130 °C), pressures (1 to 800 bar), and compositions (10–40 wt.‐% PEO). The system phase separates upon cooling and Tcl was found to decrease with an increase in pressure for a constant composition. In the absence of special effects, this finding indicates negative excess volumes. Special attention was paid to the demixing temperatures as a function of the pressure for the different polymer mixtures and the plots in the T‐ϕ plane (where ϕ signifies volume fractions). The cloud‐point curves of the polymer mixture under pressures were observed for different compositions. The Sanchez‐Lacombe (SL) lattice fluid theory was used to calculate the spinodals, the binodals, the Flory‐Huggins (FH) interaction parameter, the enthalpy of mixing, and the volume changes of mixing. The calculated results show that modified P(EO‐b‐DMS) scaling parameters with the new combining rules can describe the thermodynamics of the PEO/P(EO‐b‐DMS) system well with the SL theory.Cloud point curves for various PEO/P(EO‐b‐DMS) polymer mixtures at various pressures on the T‐ϕPEO plane.magnified imageCloud point curves for various PEO/P(EO‐b‐DMS) polymer mixtures at various pressures on the T‐ϕPEO plane.
Interpretation of Colloidal Dyeing of Polyester Fabrics Treated with N‐Cetylpyridinium Chloride in Terms of Zeta Potential and Surface Free Energy Balance
Authors: Espinosa‐Jiménez Manuel , Ontiveros‐Ortega A. , Padilla‐Weigand R. , Ramos‐Tejada M. M. , Perea‐Carpio R. 
Published: December 2003

AbstractIn this work are presented results about the effect on the surface free energy and zeta potential for the adsorption process of the colloidal dye Disperse Blue 3 (DBlue3) onto polyester fabric (dacron 54, stile 777), when the fabric is pretreated with N‐cetylpyridinium chloride (NCPCl). The zeta potential of the fabric as a function of the pH of the liquid phase shows that both H+ and OH− ions are involved in determining the potential. The negative charge of the fiber is caused by the presence of the carboxyl end‐groups of the polyester, which are generated by the acidic and basic hydrolysis of the fabric in these media. The zeta potential of the DBlue3 as a function of the pH of the liquid phase shows that the negative charge of the dye particles are because of the presence of an OH− group, ionized in aqueous media, in the molecular structure of the dye. The zeta potential of the fabric treated with a 10−3 M solution of NCPCl as a function of the pH of the liquid phase is positive over the whole pH range. This behavior can be attributed to the presence of the pyridinium group in the molecular structure of the surfactant, which is positively charged. The adsorption isotherms of the dye DBlue3 onto a polyester pretreated with NCPCl at 293 K, shows that the presence of the surfactant on the surface of the fabric favors the adsorption of the dye onto the fabric. This fact shows that the pretreatment with NCPCl is a very interesting aspect in the textile industry. On the other hand, the isotherms of the adsorption of the above dye onto the polyester pretreated with a 10−4 M solution of NCPCl, at different temperatures, shows that the amount of the dye absorbed onto the pretreated fabric increases with the increase in temperature. These behaviors can be justified by the analysis of the components of the surface free energy and zeta potential.Electron microscopy photographs of the fabric pretreated with NCPCl before (top) and after (bottom) dyeing with DBlue3.magnified imageElectron microscopy photographs of the fabric pretreated with NCPCl before (top) and after (bottom) dyeing with DBlue3.
New Polylactide/Layered Silicate Nanocomposites, 6
Authors: Sinha Ray Suprakas , Okamoto Masami 
Published: December 2003

AbstractThe measurement of rheological properties of any polymeric material under molten state is crucial to gain fundamental understanding of the processability of that material. In the case of polymer/layered silicate nanocomposites, the measurements of rheological properties are not only important to understand the knowledge of the processability of these materials, but is also helpful to find out the strength of polymer‐layered silicate interactions and the structure‐property relationship in nanocomposites. This is because rheological behaviors are strongly influenced by their nanoscale structure and interfacial characteristics. In order to get this knowledge in the case of polylactide/montmorillonite nanocomposites, we have studied melt rheological properties of these materials in detail. On the basis of rheological data, we have conducted foam processing of pure polylactide and one representative nanocomposite by a newly developed pressure cell technique using carbon dioxide as a physical‐blowing agent.The time variation of the elongational viscosity of one of the intercalated polylactide/montmorillonite nanocomposites.magnified imageThe time variation of the elongational viscosity of one of the intercalated polylactide/montmorillonite nanocomposites.
Design of a Microfluidic System to Investigate the Mechanical Properties of Layer‐by‐Layer Fabricated Capsules
Authors: Prevot Michelle , Cordeiro Ana L. , Sukhorukov Gleb B. , Lvov Yuri , Besser Ronald S. , Möhwald Helmuth 
Published: December 2003

AbstractA microfluidic system was designed, fabricated and implemented to study the behavior of polyelectrolyte capsules flowing in microscale channels. The device contains microchannels that lead into constrictions intended to capture polyelectrolyte microcapsules which were fabricated with the well‐known layer‐by‐layer (LbL) assembly technique. The behavior of hollow capsules at the constrictions was visualized and the properties of the capsules were investigated before and after introduction into the device.Time series of video frames showing capsules being compressed into a constriction.magnified imageTime series of video frames showing capsules being compressed into a constriction.
Tailored Besov spaces and h‐sets
Authors: Bricchi Michele 
Published: December 2003

AbstractIn this paper we define Besov‐type spaces with generalised smoothness on a rather vast class of (isotropic) irregular sets of fractal type in the Euclidean space (h‐sets). As a special case we shall obtain the definition of Besov spaces with the usual scalar‐index of regularity. To deal with this problem we rely on the one hand on the measure‐geometric theory we have developed for h‐sets and, on the other, we rely on some known results for Besov spaces with generalised smoothness in ℝn and on some advanced techniques concerning these function spaces (local means and atoms), which have been recently developed in full generality by W. Farkas and H.‐G. Leopold. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic Temperature Distribution in Photo‐induced Alignment of Azobenzene Liquid Crystalline Polymer
Authors: Zhao Dan , Zhang Qijin , Lu Yong , Li Jian , Liu Jian , Cheng Xiaofang 
Published: December 2003

AbstractA theoretical model has been established to describe the dynamic temperature distribution during the alignment of an azobenzene liquid crystalline polymer irradiated by a linearly polarized laser beam. The dynamic heat diffusion equations are used, and the relationship between heat source item and time is introduced, based on experimental results. With the model, the contours of the temperature distribution at different time have been worked out. It can be found from the theoretical model that there is a maximum temperature rise during the photo‐induced alignment, which is coincident with the analysis of experimental observations. The existence of a minimum laser power and an offset photo‐alignment temperature Toff required to carry on photo‐induce alignment are explained based on the theoretical model.Temperature distribution after two minutes.imageTemperature distribution after two minutes.