bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scaling potential index (SPI) for CaCO3 based on Gibbs free energies
Authors: Sheikholeslami R. 
Published: April 2005

AbstractA new index (SPI) incorporating the theoretical thermodynamic relationships relating the equilibrium and solubility constants to the Gibbs free energy of reactions is obtained for assessing the scaling potential of carbonate system. Also inclusion of activity and specific ion interactive forces extends the applicability of the SPI over a wide salinity ranges and in presence of other cations and anions that is usually encountered in brackish water and sea water reverse osmosis desalination units, in concentrate management, and in differentiating between reverse osmosis and nanofiltration modules that have different passages for mono‐valent and di‐valent ions. Some of the industrially used empirical indices for prediction CaCO3 scaling potential are reviewed and their shortcomings are discussed. The theoretically calculated results for SPI have been compared and validated with experimental values and with other commonly and industrially used indices. The results show that SPI is a better predictive approach. This method could be easily extended to take into account the pressure effects in membrane units. Furthermore, the same principle could be applied and the procedure could easily be extended to other salts. This index is a measure of the scaling potential and provides a conservative measure. Use of Gibbs free energy not only provides a theoretical means for assessing the scaling potential but also will enable future incorporation of the interactive and solvent effects in determining the solubility constants which could become readily possible with the advances in computational chemistry and incorporation of the kinetic and hydrodynamic effects in the future studies from the first principles. © 2005 American Institute of Chemical Engineers AIChE J, 2005
Preparation and recovery properties of homogeneous modified polysulfone plate affinity membrane chromatography with thiohydroxy as chelating groups. I. Synthesis and preparation of plate matrix membrane
Authors: Wang Bing , Huang Wenqiang , Yang Xinlin 
Published: April 2005

AbstractA chloromethylation polysulfone (CMPSF), having good properties of membrane formation, spinnability, and reactive groups, was synthesized with Friedel–Crafts reaction, which could be used as reactivity matrix membrane materials. The effects of ZnCl2 quantity, monochloro methyl ether quantity, reaction time, and reaction temperature on the chlorinity of CMPSF were investigated. The CMPSF plate matrix membranes were prepared with phase inversion by use of the CMPSF/additive/N,N′‐dimethylacetamide (DMAc) casting solution and CMPSF as membrane materials. The focus of this study was primarily concerned with the relationship among such factors as species and contents of additives, CMPSF content in casting solutions, and temperature of solutions, and the morphological structure of the membrane, pore size, porosity, and water flux of the membrane. It was concluded that these factors had obvious effects on the structure and the performance of the CMPSF matrix plate membrane, which could be improved within a wide range by changing the thermodynamic conditions of the casting solution. The effects of coagulation conditions on the microstructure and performance of CMPSF plate matrix membrane were also studied. It was found that the water flux of the CMPSF plate matrix membrane was at a maximum value by use of 10% DMAC solution as coagulation bath. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2117–2131, 2005
Fourier transform Raman and Fourier transform infrared spectroscopy studies of silk fibroin
Authors: Shao Jianzhong , Zheng Jinhuan , Liu Jinqiang , Carr C. M. 
Published: April 2005

AbstractThe chemical and conformational structures of Bombyx mori silk were studied with the complementary techniques of Fourier transform Raman spectroscopy and Fourier transform infrared spectroscopy. The Fourier transform Raman spectrum of silk showed strong bands for the photosensitive aromatic amino acids tyrosine, tryptophan, and phenylalanine. Intensive UV/ozone irradiation reduced the Raman intensities of the amide III band and the tyrosine signals due to peptide chain scission of the silk polymer and the photochemical changes in the tyrosine residues on the silk molecules. However, the Raman spectroscopy changes for tryptophan were less clearly defined because of peak overlapping with other amino acid signals and the low concentration of tryptophan. The Fourier transform infrared (attenuated total reflectance) technique, coupled with second‐derivative spectroscopy analysis, demonstrated a decrease in the crystallinity degree and tyrosine content of UV/ozone‐irradiated silk, as indicated by changes in the Fourier transform infrared bands of amide III doublet and tyrosine signals. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1999–2004, 2005
Supercritical CO2–assisted synthesis and characterization of a polystyrene/thermal polyurethane blend
Authors: Xu Qun , Zhao Yuan 
Published: April 2005

AbstractA blend of polystyrene and thermal polyurethane (PS/TPU) was prepared using supercritical (SC) CO2 as a substrate‐swelling agent and monomer/initiator carrier. The SC CO2/styrene/TPU ternary system was studied. Virgin TPU and synthesized blends were characterized through differential scanning calorimetry, infrared spectroscopy, rheometric measurements, and SEM. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2016–2020, 2005
Main‐chain liquid‐crystalline ionomers bearing potassium sulfonate groups
Authors: Meng Fan‐Bao , Zhang Bao‐Yan , Xu Ye , Liu Jing‐Yan 
Published: April 2005

AbstractA series of thermotropic main‐chain liquid‐crystalline (LC) ionomers were prepared, which contained potassium sulfonate groups pendent to the chains. The polymers were prepared in an esterifying reaction with potassium ion contents ranging between 0 and 3.9 wt %. The content of potassium ion was characterized by spectrophotometric analysis with sodium tetraphenylboron as the titrant. Chemical structures were determined by various experimental techniques including Fourier transform IR spectroscopy and 1H‐NMR. LC properties were characterized by differential scanning calorimetry, polarizing optical microscopy, and X‐rays. All of the polymers displayed nematic or smectic mesophases. With increasing potassium sulfonate ionic concentration in the polymers, the melting temperatures and isotropic transition temperatures changed little, whereas the temperature of the smectic A–nematic phase transition increased. The ionic aggregation was tangled with the rigid mesogenic groups of LC segments to form multiple block domains, leading the soft main chains to fold and form a lamellar structure due to their electrostatic interactions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2021–2026, 2005
Characterization of a thermoset by thermal analysis techniques: Criterion to assign the value of the α‐transition temperature by dielectric analysis
Authors: Núñez‐Regueira Lisardo , Gracia‐Fernández C. A. , Gómez‐Barreiro S. 
Published: April 2005

AbstractA cured thermoset composed of diglycidyl ether of bisphenol A and m‐xylylene diamine as the cure agent was studied with different thermal analysis techniques, including differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and dielectric analysis (DEA). DSC was used to measure the glass‐transition temperature and to check the absence of the heat of reaction. DMA and DEA were used to show the existence of two transitions in the temperature range of −100 to 240°C. The transition at a low temperature corresponded to the β transition. The second one, at a higher temperature, was associated with an α transition. The β transition followed Arrhenius behavior, whereas the α transition followed Vogel behavior. For an analysis of the α transition, different equations, such as the Havriliak–Negami, Vogel, and Williams–Landel–Ferry equations, were used. Important differences related to the fitting parameters were found that depended on the type of equation and the operation mode used. For this reason, a new method for calculating the α‐transition temperature was examined. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2027–2037, 2005
Crystallization and dynamic mechanical properties of polypropylene/polystyrene blends modified with maleic anhydride and styrene
Authors: Zhang Yu , Huang Yongping , Mai Kancheng 
Published: April 2005

AbstractPolypropylene (PP)/polystyrene (PS) blends modified with reactive monomers, such as maleic anhydride (MAH) and styrene (St), and in situ formed PP/PS blends were prepared by melting extrusion. The crystallization and melting behavior and the dynamic mechanical properties of the PP/PS blends, including the structure of the grafted copolymer, were investigated with differential scanning calorimetry, dynamic mechanical analysis, and Fourier transform infrared. The results indicated that the addition of MAH hardly influenced the crystallization temperature of PP in the blends, but the addition of MAH and St increased the crystallization temperature of PP in its blends. The blends showed no remarkable variety for the melting temperature, but the shapes of the melting peaks were influenced by the addition of the reactive monomers. In addition, a significant increase in the storage and loss moduli of all the modified PP/PS blends was observed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2038–2045, 2005
Synthesis and characterization of quaternized poly(4‐vinylpyridine‐co‐styrene) membranes
Authors: Huang Aibin , Xiao Chaobo , Zhuang Lin 
Published: April 2005

AbstractCopolymers of 4‐vinylpyridine and styrene [P(4VP–St)s] with varied molar ratios were synthesized by means of radical mass polymerization with 2,2′‐azobisisobutyronitrile as an initiator. The insoluble (linear) pyridinium‐type polymers in the octyl‐pyridinium bromide form, which possess various macromolecular chain compositions, were prepared by the reaction of each P(4VP–St) with 1‐bromooctane. A series of membranes were prepared for use in electrochemistry. These membranes, prepared with quaternized poly(styrene‐co‐4‐vinylpyridine), were characterized by IRspectroscopy, X‐ray diffraction, differential scanning calorimetry, thermogravimetory, tensile strength measurements, scanning electron microscopy, and an electrochemistry workstation. Our emphasis was to select a membrane with appropriate properties for use in the electrochemistry field. A promising membrane was selected to use in the field of electrochemistry by these characterizations. This study could be the preparation for a study on the electrochemical properties of pyridinium‐type polymers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2146–2153, 2005
Pore structure and water‐swelling behavior of porous resins based on methyl acrylate and different divinylbenzene isomers
Authors: Wei Jia , Tang Xiaoshan , Wang Xunhua , Yan Jun 
Published: April 2005

AbstractPorous resins based on divinylbenzene (DVB) and methyl acrylate (MA) were prepared with m‐DVB (98.3%) or p‐DVB (99.1%) in the presence of toluene as a porogen. The MA/DVB resins thus obtained with a wide range of pore structures were hydrophobic in nature and were swellable by direct contact with water. The behavior of m‐DVB and p‐DVB as a crosslinker in the MA/DVB monomer system was different from that in the styrene (ST)/DVB system and was influenced by the amount of MA in the MA/DVB monomer system. As a result, a larger specific surface area and pore volume were observed for MA/DVB resins derived from p‐DVB than for those derived from m‐DVB, which was opposite to that observed for resins based on DVB and ST. The different behaviors of m‐DVB and p‐DVB in the MA/DVB monomer system also resulted in different swelling abilities of the resins in water. Compared with the MA/DVB resins derived from m‐DVB, the p‐DVB derived resins swelled faster in water and were water‐swellable when the resins had a higher DVB content and, therefore, a stronger hydrophobicity and a larger specific surface area. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2071–2078, 2005
Thermal and microwave‐assisted oxidative degradation of poly(ethylene oxide)
Authors: Vijayalakshmi S. P. , Chakraborty J. , Madras Giridhar 
Published: April 2005

AbstractThe kinetics of the thermal and microwave‐assisted oxidative degradation of poly(ethylene oxide) were determined with potassium persulfate as the oxidizing agent. Gel permeation chromatography was used to determine the variation of the molecular weight with time. The degradation was studied as a function of the temperature and persulfate concentration, and it was found that the degradation rate increased with the temperature and concentration of persulfate. Continuous distribution kinetics were used to determine the rate coefficients for the degradation process, and the activation energies were obtained. The results indicated that the microwave‐assisted process had a lower activation energy of 10.3 kcal/mol, whereas that of the thermal degradation was 25.2 kcal/mol. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2090–2096, 2005
Modeling the large‐strain constitutive behavior of polycarbonate under isothermal and anisothermal conditions
Authors: Sweeney J. , Caton‐Rose P. , Coates P. D. 
Published: April 2005

AbstractThe tensile behavior of polycarbonate was studied at large strains below the glass‐transition temperature. Experiments were carried out at a series of constant temperatures and also under conditions of falling temperatures. The specimens necked with a natural draw ratio of approximately 2, and the study was mainly focused on the necked material. Isothermal experiments revealed an elastic mechanism that initiated beyond the natural draw ratio. A model consisting of an Eyring process and two Gaussian elastic mechanisms was found to be applicable to both the isothermal and anisothermal stress‐relaxation and stress–strain results. The same model also produced reasonable estimates of the stresses generated during the necking process. In addition, a simple relationship between the isothermal and anisothermal stress relaxation was demonstrated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2105–2116, 2005
Structural characterization of human elastin derived peptides containing the GXXP sequence
Authors: Moroy Gautier , Alix Alain J. P. , Héry‐Huynh Stéphanie 
Published: April 2005

AbstractThe degradation of elastin, the insoluble biopolymer of tropoelastin, can lead to the production of small peptides. These elastin‐derived peptides (EDPs) are playing a key role in cellular behavior within the extracellular matrix, showing a great variety of biological effects such as chemotaxis, stimulation of cell proliferation, ion flux modifications, vasorelaxation, and inflammatory enzymes secretion. It has also been demonstrated recently that EDPs containing the GXXPG motif could induce pro‐MMP1 and pro‐MMP3 upregulation. Elastolysis could then cause collagen degradation and play an important role in the aging process. Many experimental studies have been devoted to EDPs, but their structure/activity relationships are not well elucidated yet. However, the assumption that their active conformation is a type VIII β‐turn on GXXP was highly suggested on the basis of predictive statistical calculations.Investigation of the EDPs three‐dimensional (3D) structure would provide useful information for drug‐design strategies to propose specific inhibitors. The work presented here reports theoretical results obtained from molecular dynamics simulations performed over 128 human EDPs containing the GXXP motif. We show that all the peptides, for which the central residues are not glycines, adopt a canonical (or very close to) type VIII β‐turn structure on the GXXP sequence. Amino acids surrounding this motif are also important for the structural behavior. Any residue located before the GXXP motif (XGXXP) increases the β‐turn stabilization, whereas the residue located after GXXP (GXXPX) has no significant structural effect. Moreover, we show their biological activity can be correlated with their ability to exhibit a type VIII β‐turn conformation. © 2005 Wiley Periodicals, Inc. Biopoly 78: 206–220, 2005
Functional Analysis of the Aureothin Iterative Type I Polyketide Synthase
Authors: He Jing , Hertweck Christian 
Published: April 2005

AbstractThe modular‐type polyketide synthase (PKS) that is involved in aureothin (aur) biosynthesis represents one of the first examples in which a single PKS module (AurA) is used in an iterative fashion. Here we report on the heterologous expression of an engineered AurAB fusion protein that unequivocally proves the iterative nature of AurA. In addition, point mutations reveal that aur PKS module 4 participates in polyketide biosynthesis despite its aberrant acyltransferase domain.
Triplet–Triplet Energy Transfer Controlled by the Donor–Acceptor Distance in Rigidly Held Palladium‐Containing Cofacial Bisporphyrins
Authors: Faure Sébastien , Stern Christine , Espinosa Enrique , Douville Jasmin , Guilard Roger , Harvey Pierre D. 
Published: April 2005

AbstractEleven new complexes, including mono‐, heterobi‐, and homobimetallic cofacial bisporphyrins, (Pd)H2DPS, (M)H2DPX, (M)H2DPB, (PdZn)DPS, (PdZn)DPX, (Pt)2DPX, (M)2DPB (M=Pd, Pt), and (Pt)P (DPS4−=4,6‐bis[5‐(2,8,13,17‐tetraethyl‐3,7,12,18‐tetramethylporphyrinyl)]dibenzothiophene tetraanion, DPX4−=4,5‐bis[5‐(2,8,13,17‐tetraethyl‐3,7,12,18‐tetramethylporphyrinyl)]‐9,9‐dimethylxanthene tetraanion, DPB4−=1,8‐bis[5‐(2,8,13,17‐tetraethyl‐3,7,12,18‐tetramethylporphyrinyl)]biphenylene tetraanion, P2−=5‐phenyl‐2,8,13,17‐tetraethyl‐3,7,12,18‐tetramethylporphyrin dianion) have been synthesized and characterized. The photophysical properties of the donor (M)P (M=Pd or Pt, P=porphyrin chromophore) and the acceptor (free base H2P or (Zn)P) depend on the Cmeso–Cmeso distance and the presence of a heavy atom such as PdII or PtII. The data were compared with those for the known compounds (Pd)2DPS, (Pd)2DPX, H4DPS, H4DPX, H4DPB, (Pd)P, (Zn)P, and H2P. The rate constants for triplet–triplet energy transfer (kET) were measured for the heterobimetallic (PdZn) and monometallic [(M)H2] derivatives (M=Pd, Pt). The fluorescence lifetimes (ΔτF) of the acceptors decrease as a result of the heavy‐atom effect, and vary as follows: (Pd)H2DPS≪(Pd)H2DPX∼(Pd)H2DPB. The kET values calculated according to the equation kET=(1/τemi−1/τemi0), where τemi0 is the emission lifetime of the homobimetallic bisporphyrins (no ET occurs), are equal to 0, 247±57 and 133±52 s−1 for DPS, DPX, and DPB, respectively, in the (Pd)H2 series. These measurements allowed the range of distance over which the Dexter mechanism for T1–T1 energy transfer ceases to operate to be determined. This distance is somewhere between 4.3 and 6.3 Å, in agreement with our recent findings on singlet–singlet energy transfer. During the course of this study, the X‐ray crystal structure for (Pd)H2DPX was obtained; triclinic (P$\bar 1$), a=11.1016(1), b=14.9868(2), c=20.6786(3) Å, α=102.091(1), β=100.587(1), γ=101.817(1)°, V=3199.19(7) Å3, Z=2.
Dichlororuthenium(IV) Complex of meso‐Tetrakis(2,6‐dichlorophenyl)porphyrin: Active and Robust Catalyst for Highly Selective Oxidation of Arenes, Unsaturated Steroids, and Electron‐Deficient Alkenes by Using 2,6‐Dichloropyridine N‐Oxide
Authors: Zhang Jun‐Long , Che Chi‐Ming 
Published: April 2005

Abstract[RuIV(2,6‐Cl2tpp)Cl2], prepared in 90 % yield from the reaction of [RuVI(2,6‐Cl2tpp)O2] with Me3SiCl and structurally characterized by X‐ray crystallography, is markedly superior to [RuIV(tmp)Cl2], [RuIV(ttp)Cl2], and [RuII(por)(CO)] (por=2,6‐Cl2tpp, F20‐tpp, F28‐tpp) as a catalyst for alkene epoxidation with 2,6‐Cl2pyNO (2,6‐Cl2tpp=meso‐tetrakis(2,6‐dichlorophenyl)porphyrinato dianion; tmp=meso‐tetramesitylporphyrinato dianion; ttp=meso‐tetrakis(p‐tolyl)porphyrinato dianion; F20‐tpp=meso‐tetrakis(pentafluorophenyl)porphyrinato dianion; F28‐tpp=2,3,7,8,12,13,17,18‐octafluoro‐5,10,15,20‐tetrakis(pentafluorophenyl)porphyrinato dianion). The “[RuIV(2,6‐Cl2tpp)Cl2]+2,6‐Cl2pyNO” protocol oxidized, under acid‐free conditions, a wide variety of hydrocarbons including 1) cycloalkenes, conjugated enynes, electron‐deficient alkenes (to afford epoxides), 2) arenes (to afford quinones), and 3) Δ5‐unsaturated steroids, Δ4‐3‐ketosteroids, and estratetraene derivatives (to afford epoxide/ketone derivatives of steroids) in up to 99 % product yield within several hours with up to 100 % substrate conversion and excellent regio‐ or diastereoselectivity. Catalyst [RuIV(2,6‐Cl2tpp)Cl2] is remarkably active and robust toward the above oxidation reactions, and turnover numbers of up to 6.4×103, 2.0×104, and 1.6×104 were obtained for the oxidation of α,β‐unsaturated ketones, arenes, and Δ5‐unsaturated steroids, respectively.
Control of Helix Sense by Composition of Chiral–Achiral Copolymers of N‐Propargylbenzamides
Authors: Tabei Junichi , Shiotsuki Masashi , Sato Takahiro , Sanda Fumio , Masuda Toshio 
Published: April 2005

AbstractN‐Propargylbenzamides 1–7 were polymerized with (nbd)Rh+[η6‐C6H5B−(C6H5)3] to afford polymers with moderate molecular weights (Mn = 26 000–51 000) in good yields. The 1H NMR spectra demonstrated that the polymers have fairly stereoregular structures (81–88 % cis). The optically active polymers, poly(1) and poly(2), were proven by their intense CD signals and large optical rotations to adopt a stable helical conformation with an excess of one‐handed screw sense when heated in CHCl3 or toluene. The sign of Cotton effect could be controlled by varying the content in the copolymers of either chiral bulky 1 and achiral nonbulky 3, or chiral nonbulky 2 and achiral bulky 7. The smaller the pendant group in the copolymerization of achiral monomers with 1, the more easily did the preferential helical sense change with the copolymer composition. However, the copolymers of chiral nonbulky 2 and achiral nonbulky 3 did not change the helical sense, irrespective of the composition. The free energy differences between the plus and minus helical states, as well as the excess free energy of the helix reversal, of those chiral–achiral random copolymers were estimated by applying a modified Ising model.
Intervalence Charge Transfer (IVCT) in Ruthenium Dinuclear and Trinuclear Assemblies Containing the Bridging Ligand HAT {1,4,5,8,9,12‐hexaazatriphenylene}
Authors: D'Alessandro Deanna M. , Keene F. Richard 
Published: April 2005

AbstractThe IVCT characteristics of the mixed‐valence forms of the dinuclear [{Ru(bpy)2}2(μ‐hat)]n+ and the trinuclear [{Ru(bpy)2}3(μ‐hat)]n+ species {HAT=1,4,5,8,9,12‐hexaazatriphenylene; bpy=2,2′‐bipyridine} show a marked dependence on the nuclearity, and in the trinuclear case on the extent of oxidation. Small differences are also found between the diastereoisomers of the dinuclear complex {meso (ΔΛ) and rac (ΔΔ/ΛΛ)}, and between the homochiral (Δ3/Λ3) and heterochiral (Δ2Λ/Λ2Δ) diastereoisomers of the trinuclear case. The strong metal–metal interactions result in unusual spectroscopic and electrochemical properties of the singly‐oxidised (+7) and doubly‐oxidised (+8) trinuclear mixed‐valence species. A qualitative localised bonding description based on the geometrical properties of the dπ(RuII/III) orbitals is invoked to explain the IVCT behaviour in the di‐ and trinuclear systems.