bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermodynamisches Modell zum Fest/flüssig‐Phasenübergang von Substanzen hohen molaren Volumens
Authors: Delgado A. , Rauh C. , Benning R.
Published: July 2008

Ein thermodynamisches Modell zur Beschreibung des Gleichgewichtsverhaltens an Fest/flüssig‐Phasengrenzgrenzlinien wird in diesem Beitrag vorgestellt. Es handelt sich dabei um eine gewöhnliche, nichtlineare Differentialgleichung erster Ordnung, die sich bei Kenntnis der molaren Phasenübergangsenthalpie und ‐temperatur sowie des thermischen Ausdehnungskoeffizienten, der Kompressibilität und des molaren Volumens beider Koexistenzphasen mit geringem Aufwand integrieren lässt. Für Substanzen biologischer Herkunft mit hohem molarem Volumen – wie z. B. Öle und Fette – prognostiziert eine vereinfachte Form des Modells in guter Übereinstimmung mit dem Experiment näherungsweise lineare Phasenkoexistenzlinien. Somit liegt eine Formulierung vor, die große Vorzüge hinsichtlich Simulation und Führung der Behandlung von Biomaterie mit hochdruckinduziertem fest/flüssig‐Phasenübergang bietet.
Hochdruckhomogenisierung von Milch mit modifizierten Lochblenden im Vergleich zu konventionellen Flachventilen
Authors: Karasch S. , Kulozik U.
Published: July 2008

In der Milchwirtschaft ist die Hochdruckhomogenisierung von Milch mit Flachventilen Stand der Technik. Ein neuartiges und als sehr effizient beschriebenes, für die Milchhomogenisation allerdings kaum untersuchtes Homogenisierverfahren, stellt die Lochblendentechnik dar. Im Rahmen dieser Arbeit wurde die Lochblendentechnik auf ihre Eignung für die Homogenisierung von Milch mit unterschiedlichem Fettgehalt geprüft, mit dem Ziel der Effektivitätssteigerung weiterentwickelt und mit einem konventionellen Hochdruckhomogenisator verglichen. Die erzielten Ergebnisse zeigen die Potenziale sowie Grenzen der Lochblendentechnik auf und ermöglichen es, die dispersitätsbestimmenden Vorgänge bei der Homogenisierung besser zu verstehen.
Innovative Einsätze der Membrantrenntechnik in der Lebensmitteltechnologie
Authors: Kulozik U. , Ripperger S.
Published: July 2008

Die Lebensmittelverfahrenstechnik beschäftigt sich mit der Umwandlung von Rohstoffen zu Produkten mit neuen Eigenschaften. Mit Hilfe verschiedener Grundoperationen wie thermische Behandlung, Anreichern, Trennen oder Fraktionieren werden die inneren Eigenschaften der Rohstoffe soweit wie nötig verändert, um Anforderungen hinsichtlich Sicherheit, Haltbarkeit aber auch der sensorischen Eigenschaften gerecht zu werden. In Bezug auf die Strukturbildung, die sich in sensorisch wahrnehmbaren, rheologischen Attributen wie Gelstärke, Elastizität der Endprodukte ausdrückt, spielen funktionelle Biopolymere (Proteine, Polysaccharide) eine ausschlaggebende Rolle, oft im Zusammenspiel mit anderen Komponenten der meist komplex zusammengesetzten Rohstoffe. Insofern ist man interessiert, diese Komponenten in ihrer Konzentration, ihrem Verhältnis zueinander anzureichern oder zu isolieren und anschließend in ihren jeweils eigenständigen Eigenschaften spezifisch zu nutzen. So eröffnen sich Möglichkeiten, die Strukturbildungskapazität natürlicher Biopolymere gezielt zu beeinflussen und bei der Bildung von Gelen, Emulsionen oder Schäumen zu steuern. Membranverfahren liefern hierzu entscheidende Beiträge.
Flow rate measurement errors in vacuum tubes: Effect of gas resistance to accumulation
Authors: Chapanian R. , Shemshaki F. , Kruczek B.
Published: July 2008

Accumulative flow of gas into a vacuum tube has been studied. An analytical model, based on Fick's second law and assuming a constant diffusion coefficient, has been developed to describe the pressure response as a function of time and tube axial position for a constant gas flow rate into a closed vacuum tube. The predicted non‐linear pressure response was verified by conducting short‐term experiments involving a constant gas flow into an instrumented vacuum tube. Initially, the error in flow rate determined using the pressure rise technique was as much as ±100%. At longer time intervals, the constant diffusion coefficient assumption is invalid and the empirical model of Knudsen is used to describe the dependence of the diffusion coefficient on pressure. The governing partial differential equation was solved numerically. The numerical solution accurately predicts the pressure response at any time interval.
Direct oxidation of hydrogen sulphide to sulphur using impregnated activated carbon catalysts
Authors: Dalai Ajay K. , Cundall Michael T. , De Mahuya
Published: July 2008

Low concentrations of H2S were directly oxidized to sulphur and small quantities of SO2, over seven different activated carbons with or without impregnation. The effectiveness of virgin activated carbon was tested at 175°C, 700 kPa, and O2/H2S ratio with 5% greater than stoichiometry. The conversion of H2S was 99.9 mol% with SO2 production of 3–6%, for 360 min runtime for Fisher coconut shell activated carbon and 648 min for Envirotrol bituminous (EB) activated carbon. Then the activated carbons became deactivated due to deposition of sulphur on the surface. Under these conditions mesoporous activated carbons such as EB and Hydrodarco had the longest breakthrough time. The addition of 5.5 wt% ammonium iodide, potassium iodide and potassium carbonate individually to EB decreased the production of SO2 while having minimal effect on the overall H2S conversion. The addition of 5.5 wt% NH4I decreased the average SO2 production from 2.5% to 0.9%. The activation energy for the H2S oxidation on the 5.5 wt% NH4I on EB activated carbon was determined to be 40 kJ/mol.
Carbon dioxide mass transfer to non‐linear alkanes
Authors: Gómez‐Díaz D. , Navaza J. M.
Published: July 2008

In the present article, it has been studied the gas–liquid mass transfer process corresponding to carbon dioxide/2,2,4‐trimethylpentane (isooctane) and carbon dioxide/cyclohexane systems, and it has been characterized in relation to the effect caused by the operation variables, such as stirring rate and gas flow‐rate. The non‐linear nature of the alkanes used in this article has been analyzed using the comparison with the behaviour previously observed behaviour in the carbon dioxide/linear alkanes absorption process. Different models have been used to correlate the experimental mass transfer coefficient and to compare the fitting results.
Fault diagnosis and fault tolerant control using reduced order models
Authors: Manuja Seema , Narasimhan Shankar , Patwardhan Sachin
Published: July 2008

In this work, we have developed a reduced order model relevant for fault diagnosis and control. This model is combined with a generalized likelihood ratio (GLR) method and integrated with fault tolerant control schemes developed earlier. Simulation studies of an ideal binary distillation column show that the use of reduced order model improves the diagnostic performance thereby leading to improved fault tolerance. Furthermore, the proposed strategy is also computational more efficient. In inferential control, such as the use of temperature measurements to infer product compositions, the proposed fault tolerant control scheme performs better than the conventional control scheme when various soft faults occur.
A genetic‐algorithm‐based optimal scheduling system for full‐filled tanks in the processing of starting materials for alumina production
Authors: Yang Chunhua , Gui Weihua , Kong Lingshuang , Wang Xiaoli
Published: July 2008

Due to the instability of mine sources and the uncertainty of the composition of returned lye and waste liquid, there exists a significant fluctuation of raw slurry quality in the blending process of starting materials for sintering. The expected slurry was obtained through the mixing of starting materials in full‐filled tanks. In this article, an optimal scheduling model of full‐filled tanks is developed based on material balance principle and expert experiences subject to technological requirements. To solve such optimization problem, an improved genetic algorithm (IGA) is proposed, in which the intervention strategy is introduced into the random process of population initialization to obtain the well‐proportioned initial population and the probabilities of crossover and mutation are changed according to the difference between the fitness value of the best solution and the average fitness value of the better solutions as well as the difference between the fitness value of the best solution and the average fitness value of the current population to prevent premature convergence. The IGA‐based optimization system was applied to the processing of raw slurry for alumina production and the actual running results show that the composition fluctuation in mixed raw slurry decreased significantly, effectively improving the eligibility rate of the mixed raw slurry and contributing to the stabilization of the subsequent process of alumina production.
Pressure drop and mixing behaviour of non‐Newtonian fluids in a static mixing unit
Authors: Kumar Gunjan , Upadhyay S. N.
Published: July 2008

Static or motionless mixers have received wide application in chemical and allied industries due to their low cost and high efficiency. The pressure drop and mixing behaviour of such mixers have been widely studied. However, the available information for non‐Newtonian fluids is scanty. The results of pressure drop and mixing studies conducted with a locally made motionless mixer (MALAVIYA mixer) and four non‐Newtonian fluids—aq. CMC, PVA, and PEG solutions are reported in this article. The new mixer causes less pressure drop compared to some of the commercial mixers. Mixing behaviour of the unit is more closer to plug flow and a two‐parameter model correlates the dispersion data.
Horizontal air–water flow in a square cross‐section channel: Pseudo‐slug flow regime
Authors: Ribeiro A. M. , Ferreira V. , Mayor T. S. , Campos J. B. L. M.
Published: July 2008

New experimental data for air–water flow in a horizontal square cross‐section channel (H = 24.25 mm) is presented, including data on liquid hold‐up, gas and liquid velocities, and wave velocities and frequencies. For the majority of gas and liquid flow rates studied, the regime observed was pseudo‐slug. Using visualization studies it was possible to identify wavy‐stratified and pseudo‐slug flows. For the pseudo‐slug regime new correlations were obtained for liquid hold‐up, for gas and liquid velocities as a function of the ratio between gas and liquid mass flow rates, and for the frequency of roll‐waves as a function of gas and liquid mass flow rates.
Laminar, transitional and turbulent flow of Herschel–Bulkley fluids in concentric annulus
Authors: Founargiotakis K. , Kelessidis V. C. , Maglione R.
Published: July 2008

An integrated approach is presented for the flow of Herschel–Bulkley fluids in a concentric annulus, modelled as a slot, covering the full range of flow types, laminar, transitional, and turbulent flows. Prior analytical solutions for laminar flow are utilized. Turbulent flow solutions are developed using the Metzner–Reed Reynolds number after determining the local power law parameters as functions of flow geometry and the Herschel–Bulkley rheological parameters. The friction factor is estimated by modifying the pipe flow equation. Transitional flow is solved introducing transitional Reynolds numbers which are functions of the local power law index. Thus, an integrated, complete and consistent set, combining analytical, semi‐analytical and empirical equations, is provided which describe fully the flow of Herschel–Bulkley fluids in concentric annuli, modelled as a slot. The comparison with experimental and simulator data from various sources shows very good agreement over the entire range of flow types.
Experimental and numerical study of heat transfer in horizontal concentric annulus containing phase change material
Authors: Dutta Ritabrata , Atta Arnab , Dutta Tapas Kumar
Published: July 2008

In the present research work, solid–liquid phase change heat transfer was studied experimentally as well as numerically for paraffin wax encapsulated in the annulus of two coaxial circular cylinders with variable heat flux. Two‐dimensional mathematical model (Navier–Stokes equation) in terms of primitive variables has been formulated to study the melting characteristics of the phase change material (PCM). The finite volume method (FVM) and semi‐implicit, that is, SIMPLE scheme are applied to discretise the governing equations and track the solid–liquid moving front. From the comparison of experimental data and numerical simulation, it is evident that the convective heat transfer is dominant in melting phase. From the computational results it is also observed that both eccentricity and the variation in the angle of inclination of the eccentricity plays an important role for the net circulation of the molten phase as well as the thermal flux at the inner surface of the annulus.
On the drift‐flux analysis of flotation and foam fractionation processes
Authors: Stevenson Paul , Fennell Paul S. , Galvin Kevin P.
Published: July 2008

Drift‐flux analyses are a common way of estimating the phase fractions and fluxes in vertical multiphase flows. However their use has had scant impact on the flotation and foam fractionation communities despite the publication of a number of such analyses over the past two decades. By recognizing that the physics that underpin the hydrodynamics of the froth are dissimilar to those that pertain to the bubbly liquid beneath, we present a drift‐flux analysis with two characteristic curves. A method for obtaining the characteristic curve for the froth from experimental data for the drainage of stationary foams is presented.
Mechanisms of solids drawdown in stirred tanks
Authors: Khazam Oscar , Kresta Suzanne M.
Published: July 2008

Agitated tanks are used in several industrial processes to achieve complete drawdown of floating solids in liquids. The design requirements for this process are not completely defined, and are currently limited to heuristics regarding the use of a surface vortex and the effect of wettability on the difficulty of mixing, along with several initial studies in the literature. In this study, the effect of the type of impeller, particle size and shape, solids concentration, impeller submergence, and baffle configuration on the minimum drawdown speed (Njd) are investigated. It was found that the formation of a large surface vortex acts to hold particles close to the surface. Suppression of the surface vortex is recommended. In baffled tanks where the formation of a large surface vortex is suppressed, the intensity of turbulence and mean circulation velocity of the liquid are responsible for solids drawdown and distribution in the tank. The submergence of the impeller relative to the liquid surface and the pumping mode of the pitched blade turbine (PBT) were found to be the controlling parameters. CFD simulations were carried out to obtain a better understanding and interpretation of the flow patterns and drawdown mechanisms for the different baffle configurations.
The reaction of NiO/NiAl2O4 particles with alternating methane and oxygen
Authors: Mattisson Tobias , Johansson Marcus , Jerndal Erik , Lyngfelt Anders
Published: July 2008

The reduction and oxidation behaviour of oxygen carrier particles of NiO and NiAl2O4 has been investigated in a fluidized bed reactor as well as a thermogravimetric analyzer (TGA). The particles showed high reactivity and gas yield to CO2 with methane in the temperature interval 750–950°C. In the fluidized bed the yield to CO2 was between 90 and 99% using bed masses corresponding to 16–57 kg/MWfuel. Complementary experiments in a TGA at 750 and 950°C showed a clear reaction of the NiAl2O4 with CH4 at the higher temperature. There was methane released from the reactor at high degrees of solid oxidation, which is likely associated with the lack of Ni‐sites on the particles which can reform the methane. There was some carbon formation during the reduction, although the amount was minor when the gas yield to carbon dioxide and degree of oxidation of the solid was high. A simple reactor model using kinetic data from a previous study predicted the gas yield during the reduction in the fluidized bed experiments with reasonable accuracy. The oxygen carrier system investigated in this work shows high promise for use in a real CLC system, provided that the particle manufacturing process can be scaled up with reasonable cost.
Binary coalescence of air bubbles in viscous liquids in presence of non‐ionic surfactant
Authors: Giribabu K. , Ghosh Pallab
Published: July 2008

Coalescence of air bubbles is important in gas–liquid reactors and food processing operations. Bubbles can be stabilized by using non‐ionic surfactants. Binary coalescence of air bubbles in ethylene glycol and aqueous glycerol solutions were studied in this work in presence of Span 80. A novel set‐up was developed to study long coalescence times. Coalescence time was observed to follow broad stochastic distributions in all systems. The distributions were fitted with a stochastic model developed earlier. The surface tension of ethylene glycol and glycerol solutions was measured at various concentrations of Span 80. These data were fitted using a surface equation of state derived from the Langmuir isotherm. The effect of surfactant concentration on coalescence time was explained in terms of the surface excess of the surfactant and the repulsive force generated at the air–liquid interface. The results from this work illustrate the stochastic nature of bubble coalescence in viscous liquids. This work also demonstrates how non‐ionic surfactants can stabilize bubbles in such liquids.
Modelling spatial distributions of moisture and quality during drying of granular baker's yeast
Authors: Yüzgeç Uğur , Türker Mustafa , Becerikli Yasar
Published: July 2008

A distributed parameter model was developed to predict the drying behaviour of granular baker's yeast by setting up material and heat balances at the particle level. Temperature and moisture gradients were calculated for cylindrical and spherical granules. The performance of the model with two granule sizes was compared with experimental measurements. The model was initially used for non‐shrinking granules but later modified to take shrinkage into account. The reduction in granule size during the course of drying was estimated and good correspondence with experimental measurements was obtained. In addition to temperature and moisture gradients, the product quality was predicted during drying and compared to experimental results. The accuracy of the model was better than the lumped parameter model.
An Efficient Synthesis of 1,5‐Benzodiazepine Derivatives by Lanthanide Trichloride‐catalyzed Condensation of o‐Phenylenediamine with α,β‐Unsaturated Ketone under Mild Conditions
Authors: FENG Shan‐E , XU Fan , SHEN Qi
Published: July 2008

The condensation of o‐phenylenediamine with various α,β‐unsaturated ketones was efficiently catalyzed by lanthanide trichloride and a variety of 1,5‐benzodiazepines were synthesized in moderate to high yields under mild conditions. The reactions catalyzed by ytterbium trichloride were investigated emphatically.
Electrochemical Reduction of 2‐Nitroanisole in Ionic Liquid BMIm‐BF4: Synthesis of 2‐Anisidine
Authors: LIU Ying‐Zi , LIN Mei‐Yu , XIAO Li‐Ping , ZHANG Kai , LU Jia‐Xing
Published: July 2008

A new electrochemical synthesis of 2‐anisidine from 2‐nitroanisole has been developed in room‐temperature ionic liquid (RTIL), which was carried out under mild and safe conditions, where the volatile, toxic solvents, catalysts, as well as any additional supporting electrolyte were avoided. The maximal yield of 2‐anisidine reached 51.3% on Cu‐graphite couple electrodes under potentiostatic electrolysis at −1.0 V (vs. SCE) until 6 F·mol−1 of charge was passed at 50 °C, which offers a new and clean route to synthesis of 2‐anisidine. The reduction behavior of 2‐nitroanisole was studied in RTIL by cycle voltammertry. The RTIL could be recycled.
n‐Butane Monomolecular Cracking on Acidic Zeolites: A Density Functional Study
Authors: DING Bing‐Jing , HUANG Shi‐Ping , WANG Wen‐Chuan
Published: July 2008

Density functional theory was used to study monomolecular cracking reaction of n‐butane on acidic zeolite. Geometry optimizations of the local structures of the species reacting with the zeolite were carried out by using the 5T cluster model at the B3LYP/6‐311+G(3df,2p)//B3LYP/6‐31G(d) level. In this work, the deprotonation modes of two different order C atoms in n‐butane cracking on H‐ZSM‐5 were explored in detail by the density functional theory. The calculated activation barriers at the B3LYP/6‐311+G(3df,2p)//B3LYP/6‐31G(d) level are 238 kJ/mol for the primary CC cracking, 217 kJ/mol for the secondary CC cracking, 296 kJ/mol for the primary dehydrogenation, and 242 kJ/mol for the secondary dehydrogenation, respectively. The difference of the activation barrier is 54 kJ/mol for the deprotonation reactions of two different order C atoms in n‐butane. For the dehydrogenation reaction, the results indicate that the reaction is expected to be preferred at the secondary C atom. Additionally, the relation between the acidity and structure of the cluster shows that the acidity effect of the zeolite can be simulated by modifying the peripheral bonds of the cluster for the 5T cluster. Finally, the zeolite acidity effects on the reaction barriers were investigated by changing the cluster terminal SiH bond length.
Calculation of Heat of Formation for Tensile Cyclic Molecules in Condensed Phase Using Electrostatic Potential and QSPR Schemes
Authors: SHI Liang‐Wei , ZHOU Jun‐Hong , ZHANG Tao , KANG Qiang , CHEN Min‐Bo
Published: July 2008

PDDG/PM3 method was evaluated as a suitable semiempirical calculation for heat of formation of tensile cyclic organic molecules in gas phase and used in subsequent researches. In order to compute the heat of formation of these compounds in condensed phase, electrostatic potential scheme was performed to obtain the area of the Bader surface at B3LYP/6‐311G∗︁∗︁ level. The root mean square (rms) of the calculated condensed phase heat of formation for 58 molecules from corresponding experimental values is 4.81 kcal/mol. Six QSPR schemes for predicting solid phase heat of formation of 38 model molecules with physically meaningful descriptors from genetic algorithm selection were established. These selected descriptors were recalculated by DFT B3LYP/6‐311G∗︁∗︁ and MP2/6‐311G∗︁∗︁ methods, which could then give similar and better results. The QSPR schemes adopted back‐propagation neutral network (BPNN) and support vector machine (SVM) as analysis tools. It was suggested that selection of descriptors with strong physical significance in QSPR calculation should be important.
Theoretical Study on the Photochemical Ring Opening Process of 2H‐pyran
Authors: LÜ Ling‐Ling , YAN Er‐Di , WANG Xiao‐Fang , WANG Yong‐Cheng , DAI Guo‐Liang
Published: July 2008

A theoretical study of the reaction path for the photo‐ring‐open mechanism for a model system 2H‐pyran has been carried out using a CASSCF method. To monitor the electronic rearrangements along the minimum energy pathway (MEP), the electronic structures were analyzed using valence bond (VB) theory and natural bond orbital (NBO) analysis. Calculated results show that the S0‐Min, the absorption of the initial excitation, promotes the system to the S1 excited state with a (π‐π∗︁) character. From the S1‐Min, a low‐barrier path leads to an S1/S0 conical intersection. The energy of the S1/S0 crossing is located 0.63 eV below the S1‐Min. Thus, the initial movement of the nuclei will lead the system through the S1/S0 crossing to the ground state of the S0‐Prod in a very efficient nonadiabatic path along the MEP.
Topological Research on Standard Absolute Entropies, S⊖298, for Binary Inorganic Compounds
Authors: MU Lai‐Long , HE Hong‐Mei , FENG Chang‐Jun
Published: July 2008

For predicting the standard entropy of a binary inorganic compound, two novel connectivity indexes mQ, mG and their converse indexes mQ', mG' based on adjacency matrix of molecular graphs and ionic parameters gi, qi were proposed. The qi and gi are defined as qi=(1.1+Zi1.1)/(1.7+ni), gi=(1.4+Zi)/(0.9+ri+ri−1), where Zi, ni, ri are the charge numbers, the outer electronic shell primary quantum numbers, and the radii of ionic i respectively. The good Quantitative Structure‐Property Relationship (QSPR) models for the standard entropies of binary inorganic compound can be constructed from 0Q, 0Q', 1G, and 1G', by using a multivariate linear regression (MLR) method and an artificial neural network (NN) method. The correlation coefficient r, the standard error s, and the average absolute deviation of the MLR model and the NN model are 0.9905, 8.29 J·K−1·mol−1 and 6.48 J·K−1·mol−1, and 0.9960, 5.37 J·K−1·mol−1 and 3.90 J·K−1·mol−1, respectively, for 371 binary inorganic compounds (training set). The cross‐validation by using the leave‐one‐out method demonstrates that the MLR model is highly reliable from the point of view of statistics. The correlation coefficients, standard deviations and average absolute deviations of predicted values of the standard entropies of other 185 binary inorganic compounds (test set) are 0.9897, 8.64 J·K−1· mol−1 and 6.84 J·K−1·mol−1, and 0.9957, 5.63 J·K−1·mol−1 and 4.18 J·K−1·mol−1 for the MLR model and the NN model, respectively. The results show that the current method is more effective than literature methods for estimating the standard entropy of a binary inorganic compound. Both MLR and NN methods can provide acceptable models for the prediction of the standard entropies of binary inorganic compounds. The NN model for the standard entropies appears to be more reliable than the MLR model.
Synthesis, Characteristics and Standard Molar Enthalpies of Formation of MZn2HPO4PO4 (M=Na+, K+)
Authors: YUAN Ai‐Qun , WU Jian , HUANG Zai‐Yin , WU Kun , SONG Bao‐Ling , LIAO Sen , TONG Zhang‐Fa
Published: July 2008

MZn2HPO4PO4 (M=Na+, K+) double salts were synthesized by a solid‐state reaction at low temperature and a hydrothermal method, respectively, and characterized by XRD, FT‐IR, TG and SEM. Thermochemical study was performed by an isoperibol solution calorimeter. According to Hess's law, a new thermochemical cycle was designed. The results show that the obtained products are layered compounds with an isostructure of triclinic system. The decomposition temperatures are 415 and 430 °C by TG, respectively. With the dissolution enthalpies and other standard chemical data, the standard molar formation enthalpies of the MZn2HPO4PO4 (M=Na+, K+) were worked out as follows: =fH⊖m[NaZn2HPO4PO4, s] =(−3042.38±0.31) kJ·mol−1 and =fH⊖m[KZn2HPO4PO4, s] =(−3093.46±0.27) kJ·mol−1.
Thermodynamic Studies of Electrostatic Self‐assembly of Poly Diallyldimethylammonium Chloride on Proton Exchange Membrane
Authors: LIU Peng , LI Xi , PAN Mu
Published: July 2008

The electrostatic self‐assembly of polymer on proton exchange membrane was studied by calorimetric technique. The titration of poly diallyldimethylammonium chloride (PDDA) into Nafion membrane was designed and performed to determine the thermodynamic parameters. The enthalpy change ΔrH⊖mand binding constantKin the process of self‐assembly were obtained from data analysis with the help of Origin. According to the calculated thermodynamic parameters, the electrostatic self‐assembly of PDDA on the proton exchange membrane is an "enthalpy‐driven" reaction. The released heat indicates decrease of energy, which is helpful for the occurrence of the self‐assembly process, and the degree of disorder is reduced, which went against the adsorption process. As to every ion bond, the value of ΔrH⊖mof DDA is beyond PDDA because a small molecule can bind itself to the membrane without steric hindrance.
Characterization, Crystal Structure and Initial DNA Binding Mechanism Research of Multi‐nuclear Homometallic Complexes of 4,5‐Diazafluoren‐9‐one with Copper(II) and Cobalt(II)
Authors: ZHANG Rong‐Lan , ZHAO Jian‐She , XI Xiao‐Li , YANG Pin , SHI Qi‐Zhen
Published: July 2008

Two new multi‐nuclear homometallic complexes, [Cu2(OAc)4(H2O)2]·2dafo (1) and [(µ2‐O)2‐Co3(dafo)6]‐(ClO3)2·H2O (2) (dafo=4,5‐diazafluoren‐9‐one), were synthesized. The two complexes have been fully characterized by elemental analysis, IR, absorption spectra, emission spectra, and single‐crystal X‐ray diffraction analysis. The initial DNA binding mechanisms of the two complexes have been investigated by absorption spectra, emission spectra and cyclic voltammograms. Both complexes show similar perturbations on addition of calf thymus DNA in the UV region, their luminescence intensities in aqueous buffer are all enhanced in the presence of increasing amounts of DNA, and their electrochemical behavior is both completely different in the absence and presence of DNA. The results of the three methods indicate that the spectral characters and the electrochemical behavior of the two complexes are very similar to those of the known metallointercalators. So it can be concluded that the action mode of the two complexes with DNA is mainly intercalative.
From 1D Polymeric Chain to Two‐fold Parallel Interpenetration of (4,4) Net: Synthesis and Characterization of Two New Copper(II) Complexes Derived from Highly Polydentate Aminopolycarboxylate Ligand
Authors: WU Ya‐Pan , WANG Yao‐Yu , WANG Cui‐Juan , LI Dong‐Sheng , GUO Chun‐Yan , WEN Gui‐Lin , SHI Qi‐Zhen
Published: July 2008

Two new copper(II) polymers, {[Cu2(egta)(bpe)(H2O)2]·H2O}n (1) and {[Cu2(egta)(bipy)(H2O)2]·5H2O}n(2), [H4egta=3,12‐bis(carboxymethyl)‐6,9‐dioxa‐3,12‐diazatetradecanedioic acid, bpe=1,2‐bis(4‐pyridyl)ethane, bipy4,4′‐bipyridyl] have been synthesized and structurally characterized by single‐crystal X‐ray diffraction, elemental analysis, IR spectra and TG analysis. The structure determination reveals that both 1 and 2 crystallize in a monoclinic system, space group P21/c. Complex 1 exhibits a two‐fold parallel interpenetration of (4,4) net framework consisting of 1D zigzag chains interlocked together through hydrogen bonding interaction. However, the meso‐helix chains of 2 are packed to form 2D supramolecular structures. Interestingly, in 2, the host frameworks encapsulate a unique pentamer water cluster and are further connected into 1D tapes by water‐water hydrogen bonding interaction. Magnetic measurements reveal that there is a weak ferromagnetic interaction between the adjacent Cu(II) ions in 1.
Synthesis, Crystal Structure and Characterization of Two Rare Earth Substituted Keggin‐Type Germanotungstates
Authors: WANG Jing‐Ping , YAN Qing‐Xia , DU Xiao‐Di , NIU Jing‐Yang
Published: July 2008

Two germanotungstates based on the dysprosium cations and monovacant Keggin anions [GeW11O39]8−, [(CH3)4N]1.5H3.5[Dy(H2O)2(GeW11O39)]·1.5H2O (1) and [Cu(Hen)(en)]2[Cu(H2O)3]0.5{[Cu(H2en)(Hen)]‐[Cu(H2O)3]0.5[Dy(GeW11O39)2]}·1.25H2O (2), have been synthesized and characterized by elemental analysis, inductively coupled plasma (ICP) analysis, IR spectroscopy, thermal analysis, and single‐crystal X‐ray diffraction. Crystal data for 1: monoclinic, space group C2/c with cell dimensions of a=2.8201(5) nm, b=2.2885(3) nm, c=2.4033(4) nm, β=123.875(2)°, V=12.878(4) nm3, Z=8, µ=21.239 mm−1; and for 2: monoclinic, space group P21/n with cell dimensions of a=2.12808(5) nm, b=1.63834(4) nm, c=3.18074(4) nm, β=93.760(2)°, V=11.0658(5) nm3, Z=4, µ=24.803 mm−1. The Dy3+/[GeW11O39]8− ratio of compound 1 is 1:1, and it displays an interesting one dimensional chainlike arrangement. And the Dy3+/[GeW11O39]8− ratio of compound 2 is 1:2 , and it shows a typical dimeric structure.
A Green Approach to the Synthesis of Biologically Important Indeno[2,1‐e]pyrazolo[5,4‐b]pyridines via Microwave‐assisted Multi‐component Reactions in Water
Authors: SHI Feng , ZHANG Yan , TU Shu‐Jiang , ZHOU Dian‐Xiang , LI Chun‐Mei , SHAO Qing‐Qing , CAO Long‐Ji
Published: July 2008

A green approach to the synthesis of biologically important indeno[2,1‐e]pyrazolo[5,4‐b]pyridines was successfully realized via multi‐component reactions of aldehyde, 3‐methyl‐1‐phenyl‐1H‐pyrazol‐5‐amine and 1,3‐indanedione in water under microwave irradiation without catalyst. This protocol has the prominent advantages of environmental‐friendliness, short reaction time, excellent yields, low cost, easy operation as well as broad scope of applicability.
Studies on the Thermodenaturation Behavior of Bacillus subtilisα‐Amylase on Chromatographic Media
Authors: BIAN Liu‐Jiao , WANG Xiao‐Hua , YANG Xiao‐Yan , LIU Li
Published: July 2008

The thermodenaturation behavior of Bacillus subtilis α‐amylase on some chromatographic media was studied by determining their adsorption parameters with frontal analysis. The experimental results show that on a RP‐C18 reversed‐phase medium, a Chelating Sepharose Fast‐Flow chelated by Zn2+ affinity medium and a WCX‐1 cation‐exchange medium, a stable conformation of α‐amylase molecule separately exists below or over 30 °C; while on a PEG‐400 hydrophobic medium and a modified PEG‐400 medium, a stable conformation of α‐amylase molecule separately exists below 40 and 30 °C, and when the experimental temperatures are separately over 40 and 30 °C, a drastically conformational change of α‐amylase molecules can continuously take place. And by combining the intrinsic fluorescence emission spectrum and thermal inactivation profile of α‐amylase in free solution and on the PEG‐400 and modified PEG‐400 hydrophobic media, it can be concluded that in liquid chromatographic procedure, chromatographic media can induce the conformational change of α‐amylase molecules and promote their thermodenaturation; and in hydrophobic interaction chromatography, the higher the hydrophobicity of chromatographic medium, the lower the conformational change temperature of α‐amylase molecules on the chromatographic medium.
Detection and Sequence Identification of Dinucleotides Produced from N‐Phosphoryl Alanine and Four Nucleosides by HPLC‐ESI‐MS/MS
Authors: GUO Yan‐Chun , CAO Shu‐Xia , LIAO Xin‐Cheng , ZHAO Yu‐Fen
Published: July 2008

The products of the model reaction between N‐(O,O‐diisopropyl phosphoryl) alanine (DIPP‐Ala) and four nucleosides (adenosine, uridine, cytidine and guanosine) were studied by HPLC‐ESI‐MS/MS. The results showed that different mononucleotides and dinucleotides were produced. The sequences of dinucleotides formed from the DIPP‐Ala and four nucleosides were identified. The results revealed that the c‐ions from backbone fragmentation of the dinucleotides could be considered as the sequence‐diagnostic ions. It was firstly testified that the diagnostic c‐ions in positive and negative modes could be applied to identify the sequence of dinucleotide products formed in the reaction system.
Catalytic Synthesis Methods for Triazolopyrimidine Derivatives
Authors: CHENG Chun‐Sheng , GAI Yong‐Ming , WANG Xin‐Lei , PENG Jun
Published: July 2008

A new method for catalyzed synthesis of triazolopyrimidine derivatives is reported. Alkylamine reaction with dialkyl cyanodithioiminocarbonate was catalyzed by quaternary ammonium salts at room temperature to yield 3‐alkylamine‐5‐amino‐1,2,4‐triazole in good quality and high yields. After imidization and reaction with an α,β‐unsaturated acid derivative, the reaction intermediate was hydrolyzed in the presence of a Lewis acid to obtain the target product. This novel catalytic method for triazolopyrimidine derivatives can be carried out under inexpensive and mild conditions, and is safe and environmentally friendly. 1H NMR results for all intermediates are reported.
Synthesis of β‐Amino Acids via Catalyst‐ and Solvent‐Free Aza‐Michael Reaction
Authors: ZOU Bo , JIANG Huan‐Feng
Published: July 2008

A safe, environmentally friendly and cost‐effective method for the synthesis of β‐amino acid derivatives has been developed. Treatment of α,β‐unsaturated compounds with aliphatic amines furnishes β‐amino acid derivatives in good to excellent yields via a catalyst‐ and solvent‐free aza‐Michael addition.
Silica Nanotubes Prepared under Dilute Gelator Concentrations
Authors: CHEN Yuan‐Li , PEI Xian‐Feng , JIANG Yun , ZHOU Lei , ZHANG Juan , BI Li‐Feng , LI Hai‐Tao , YANG Yong‐Gang
Published: July 2008

Single‐handed helical silica nanotubes that can trap water and organic solvents were prepared by sol‐gel transcription under dilute gelator concentrations.
In(OTf)3‐mediated Facile Preparation of 2‐(3,4,5‐Trimethoxyphenyl)‐5‐[(5‐alkylthio‐1,3,4‐oxadiazol‐2‐yl)methylthio]‐1,3,4‐thiadiazole Derivatives in Aqueous Media
Authors: WU Qin , SONG Bao‐An , YANG Song , BHADURY Pinaki S. , HU De‐Yu , XUE Wei , JIN Lin‐Hong , CHEN Zhuo
Published: July 2008

Ten new 2‐(3,4,5‐trimethoxyphenyl)‐5‐[(5‐alkylthio‐1,3,4‐oxadiazol‐2‐yl)methylthio]‐1,3,4‐thiadiazole derivatives were synthesized from 2‐mercapto‐5‐(3,4,5‐trimethoxypheny1)‐1,3,4‐thiadiazole in four steps of thioetherification, hydrazidation, cyclization and thioetherification. The synthesis of the title compounds catalyzed by In(OTf)3 at 40 °C in aqueous media was easily achieved in high yields under environmentally benign conditions. Furthermore, In(OTf)3 can be recovered and reused without any notable loss of its catalytic activity.
A Novel Surfactant‐free Microemulsion System: N,N‐Dimethyl Formamide/Furaldehyde/H2O
Authors: NI Peng , HOU Wan‐Guo
Published: July 2008

Generally, a microemulsion consists of oil, water, surfactant and sometimes cosurfactant. Herein, for the first time to our knowledge, a novel surfactant‐free microemulsion (SFME), consisting of furaldehyde (oil phase), water and N,N‐dimethyl formamide (DMF) without the amphiphilic molecular structure of traditional surfactant is reported. The phase behavior of the ternary system was investigated, finding that a single‐phase microemulsion region and a two‐phase region were formed. The electrical conductivity measurement was employed to investigate the single‐phase microemulsion region. On the basis of the percolation theory, the single‐phase microemulsion region was identified to consist of three different microregions: furaldehyde‐in‐water (O/W), bicontinuous region and water‐in‐furaldehyde (W/O), which were further proved by freeze‐fracture transmission electron microscopy (FF‐TEM) observations. The diameter of the microemulsion spherical droplets is in the range of 40–70 nm.
A New Triterpenoid from the Fruits of Phellodendron chinensevar. glabriusculum Schneid
Authors: YAN Chen , WANG Ye , DU Hua , HAO Xiao‐Jiang
Published: July 2008

A new triterpenoid 21α‐methylmelianol(21R,23R)epoxy‐24‐hydroxy‐21α‐methoxyl]triucalla‐7,25‐dien‐3‐one (1), was obtained from the fruit of Phellodendron chinense var. glabriusculum Schneid and elucidated by means of spectroscopic analysis. Niloticin and melianone type tirucallane triterpenoids were major constituents in the EtOAc fraction of crude extract of the the fruit of Phellodendron chinense var. glabriusculum Schneid.
Der Ionenbegriff – historischer Spätzünder und gegenwärtiger Außenseiter
Authors: Barke Hans‐Dieter , Pieper Christian
Published: July 2008

Das Ion ist seit fast zwei Jahrhunderten ein schillernder Begriff für ein allgegenwärtiges Teilchen! Am Aufbau eines jeden Kochsalzkristalls oder Marmorkristalls sind ausschließlich Ionen beteiligt, in jedem Leitungswasser oder Mineralwasser sind bestimmte Ionenarten vorhanden: Etikette von Mineralwasserflaschen weisen es meist definitiv aus (Abb. 1).

Trotz der Allgegenwärtigkeit der Ionen als kleinsten Teilchen der Materie gibt es Probleme mit dem Verständnis des Ionenbegriffs: mehr als die Hälfte der Jugendlichen aller Klassenstufen stellen sich beispielsweise unangemessen „NaCl‐Moleküle”︁ in Kochsalz oder „CaCl2‐Moleküle”︁ in Mineralwasser vor [1]. Die Ionen scheinen an der Seite von verstehbaren Atomen und Molekülen schwer vermittelbar zu sein: Sind sie exotische Außenseiter‐Teilchen?

Der Aufsatz soll im ersten Teil ausweisen, wie schwierig die Ausschärfung des Ionenbegriffs historisch gewesen ist und dass sich diese Schwierigkeiten in der Lehre an den Universitäten widerspiegelten: lange noch lehrte man die „NaCl‐Moleküle”︁ ohne Hinweise auf das Ion – es erwies sich als historischer Spätzünder!
Chemie im Kontext in Holland
Authors: Apotheker Jan
Published: July 2008

Unzufriedenheit mit dem Curriculum, Evaluationen von Schülern, die das Fach Chemie als langweilig und wenig ansprechend empfinden, sowie rückläufige Studentenzahlen waren für das Bildungsministerium der Niederlande Anlass für eine Analyse der angeführten Probleme. Als Resultat erschien ein Bericht [1], der eine Reihe möglicher Fakten, die dabei im Chemieunterricht eine Rolle spielen, zusammenstellte. Aufgrund dieses Berichts wurde durch das Bildungsministerium ein Lenkungsausschuss gegründet, der beauftragt wurde, den Chemieunterricht in den Niederlanden neu zu gestalten. Ein Ansatz, den der Lenkungsausschuss aufgriff [2], war der des kontextbasierten Lernens, der in Deutschland unter anderemdurch Chemie im Kontext vertreten wird. Daraufhin startete an der Universität Groningen eine Gruppe von Dozenten mit der Entwicklung einer ersten exemplarischen Unterrichtseinheit zum Thema Verbrennungen, die analog zu den Strukturen und Ideen von Chemie im Kontext gestaltet wurde. Das Thema Verbrennungen wurde ausgewählt, weil es gut in das Curriculum der 3. Klasse (entsprechend der 9. Klasse in Deutschland, vgl. Abb. 1) des niederländischen Bildungssystems passt. In der 3. Klasse Chemie behandelt man die Einführung in die Chemie durch verschiedene Reaktion wie z.B. Verbrennungen.
Experimente rund um die Cola
Authors: Schunk Axel , Proske Wolfgang , Röder Johannes , Jansen Walter , Peper‐Bienzeisler Renate
Published: July 2008

Zur Untersuchung von Cola‐Getränken sind bereits vielfach Experimente und Unterrichtseinheiten beschrieben worden. Dennoch hat die CHEMKON‐Redaktion sich entschlossen, dieses Thema noch einmal unter der Rubrik DAS EXPERIMENT aufzugreifen. Wir möchten diese Rubrik damit nicht nur zur Vorstellung neuer Experimente nutzen, sondern ebenso zur Optimierung und Ergänzung bereits vorhandener. In dem nachfolgenden Beitrag finden Sie daher unter (1) die (auffrischende) Darstellung eines wirksamen Einstiegsexperiments von Axel Schunk, unter (2) Auszüge aus einer sorgfältigen Prüfung und Optimierung von Versuchsvorschriften zur Untersuchung von Cola von Wolfgang Proske und Johannes Röder sowie unter (3) einen ergänzenden Versuch zur Betrachtung der Dichte im Anfangsunterricht von Walter Jansen und Renate Peper‐Bienzeisler. Weitere Informationen zu den genannten und weiteren Experimenten können von den Autoren oder der CHEMKON‐Redaktion bezogen werden!
Anticardiolipin Antibodies Associated with Alcoholic Cardiomyopathy
Authors: de Godoy José Maria Pereira , de Godoy Moacir Fernandes , Braile Domingo Marcolino
Published: July 2008

Anticardiolipin antibodies are associated with arterial and venous thrombosis, and repetitive miscarriages.The involvement of the heart has been described frequently and can evolve into cardiomyopathy. It has been known for some decades that chronic alcoholism can lead to alcoholic cardiomyopathy (ACM). The objective of this study was to evaluate whether anticardiolipin antibodies represent a worse prognosis for patients with ACM. The authors present a case of a chronic alcoholic patient (30 y of alcoholism) who died at 44 y of age, and who was considered positive for anticardiolipin antibodies. The patient developed deep vein thrombosis, and peripheral arterial and pulmonary embolism. The presence of another risk factor seems to represent a worse prognosis for patients with ACM. Copyright © 2008 Wiley Periodicals, Inc.
Amelioration of Carbon Removal Prediction for an Activated Sludge Process using an Artificial Neural Network (ANN)
Authors: Güçlü Dünyamin , Dursun Sükrü
Published: July 2008

A dynamic simulation model of the Ankara central wastewater treatment plant (ACWTP) was evaluated for the prediction of effluent COD concentrations. Firstly, a mechanistic model of the municipal wastewater treatment process was developed based on Activated Sludge Model No. 1 (ASM1) by using a GPS‐X computer program. Then, the mechanistic model was combined with a feed‐forward back‐propagation neural network in parallel configuration. The appropriate architecture of the neural network models was determined through several iterative steps of training and testing of the models. Both models were run with the data obtained from the plant operation and laboratory analysis to predict the dynamic behavior of the process. Using these two models, effluent COD concentrations were predicted and the results were compared for the purpose of evaluation of treatment performance. It was observed that the ASM1 ANN model approach gave better results and better described the operational conditions of the plant than ASM1.
An Overview of the Biochemical and Molecular Aspects of Microbial Oxidation of Inorganic Sulfur Compounds
Authors: Mohapatra Bidyut R. , Gould W. Douglas , Dinardo Orlando , Koren David W.
Published: July 2008

Inorganic sulfur compounds are oxidized mostly to sulfate by microorganisms belonging to the bacteria and archaea domains. These microorganisms produce different types of enzymes, e. g., oxidoreductases and hydrolases for the metabolism of inorganic sulfur compounds. These versatile biocatalysts have potential biotechnological applications in different fields including biohydrometallurgical processes for recovering precious heavy metals and also for bioremediation of sulfides in industrial waste effluents. Appropriate knowledge on the enzymatic pathways of inorganic sulfur compounds oxidation will help to tailor the catalytic properties of these microorganisms so that they are optimal not only for a given reaction but also in the context of harsh industrial processes. This review describes the distribution of inorganic sulfur compound‐oxidizing microorganisms, various enzymatic systems associated with sulfur metabolism, and identification of the gene(s) responsible for catalysis of different enzymatic reactions.
Cognitive effects of hormone therapy in men with prostate cancer
Authors: Nelson Christian J. , Lee Jennifer S. , Gamboa Maria C. , Roth Andrew J.
Published: July 2008

BACKGROUND.

Men who receive androgen‐deprivation therapy (ADT) for prostate cancer experience several side effects from this treatment. A few recent studies have examined the cognitive implications of ADT and how they impact a patient's treatment decision‐making, occupational pursuits, and quality of life. For this report, the authors explored possible mechanisms for this association, reviewed research in animal studies and aging men, and examined the growing literature focused on the relation between ADT and cognitive functioning in patients with prostate cancer.

METHODS.

A systematic literature search was conducted using the PubMed and Information Sciences Institute Web of Knowledge‐Web of Science databases to identify relevant studies that investigated the relation between ADT in men with prostate cancer and its cognitive effects.

RESULTS.

Testosterone and its derivatives may have an impact on cognition through several mechanisms in the brain, as supported by studies of animals and in aging men. Studies that researched the impact of ADT on cognition in patients with prostate cancer patients were designed relatively well but suffered from small sample sizes. Between 47% and 69% of men on ADT declined in at least 1 cognitive area, most commonly in visuospatial abilities and executive functioning. Some studies reported contradictory results with increased functioning in verbal memory.

CONCLUSIONS.

There is a strong argument that androgen‐ablation therapy is linked to subtle but significant cognitive declines in men with prostate cancer. The authors believe that clinicians should become aware of this correlation as the use of ADT increases and should inform and monitor patients for this possible side effect of treatment. Cancer 2008. ©2008 American Cancer Society.