bluuebunny/crossref_metadata_2025_split huggingface dataset:
The OH• + CH3SH reaction: Support for an addition‐elimination mechanism from ab initio calculations
Authors: Muiño Pedro L. 
Published: February 2005

AbstractSeveral intermediates for the CH3SH + OH• → CH3S• + H2O reaction were identified using MP2(full) 6‐311+g(2df,p) ab initio calculations. An adduct, CH3S(H)OH•, I, with electronic energy 13.63 kJ mol−1 lower than the reactants, and a transition state, II‡, located 5.14 kJ mol−1 above I, are identified as the entrance channel for an addition‐elimination reaction mechanism. After adding zero‐point and thermal energies, ΔH(reactants → I) = −4.85 kJ mol−1 and ΔH(I → II‡) = +0.10 kJ mol−1, which indicates that the potential energy surface is broad and flat near the transition state. The calculated imaginary vibrational frequency of the transition state, 62i cm−1, is also consistent with an addition–elimination mechanism. These calculations are consistent with experimental observations of the OH• + CH3SH reaction that favored an addition–elimination mechanism rather than direct hydrogen atom abstraction. An alternative reaction, CH3SH + OH• → CH3SOH + H•, with ΔH = +56.94 kJ mol−1 was also studied, leading to a determination of ΔH(CH3SOH) = −149.8 kJ mol−1. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 612–618, 2005
Three‐phase airlift internal loop reactor: correlations for predicting the main fluid dynamic parameters
Authors: Trilleros JA , Díaz R , Redondo P 
Published: February 2005

AbstractThree‐phase airlift loop reactors have many industrial applications. Examples include applications in the chemical, metallurgical, biochemical and minerals‐processing industries; fluid dynamics in such systems is a critical factor affecting efficiency. The experimental work was carried out at a pilot‐plant scale in a tank with a cylindrical shape and conical bottom (height 1.25 m; diameter 0.42 m), water and air were used as liquid and gas phases, and for different solid phases, different loads of glass spheres (diameters: 0.25 and 1 mm; density 2.6 g cm−3), and polystyrene cylinders (diameter and length 3 mm; density 1.0 g cm−3) were introduced. Air was injected through the bottom of the tank by means of 12 nozzles (diameter 1 mm each). An internal draft tube riser was tested on different configurations as its diameter was varied (44, 82, 125 and 240 mm) as was its height (1050 and 630 mm). Corresponding liquid velocities in the adjacent annular downcomer were determined by a thermal tracer technique, solid holdups were determined by conductivity methods, riser overall gas holdups were deduced from the liquid level, and riser gas holdup from manometer readings. Several adjusted correlations were considered in a method to predict the main fluid dynamic parameters (solids and gas holdups, and superficial liquid velocities). Copyright © 2005 Society of Chemical Industry
Qualitative and quantitative analysis of active flavonoids in Flos Lonicerae by capillary zone electrophoresis coupled with solid‐phase extraction
Authors: Chen Jun , Li Song‐Lin , Li Ping , Song Yue , Chai Xing‐Yun , Ma Ding‐Yuan 
Published: February 2005

AbstractFlavonoids are an important bioactive group in the commonly used herbal medicine Flos Lonicerae. A new method of capillary zone electrophoresis (CZE) coupled with solid‐phase extraction (SPE) was developed for simultaneous assay of flavonoid aglycones and glycosides in Flos Lonicerae. Optimum CZE separation was achieved with a background electrolyte (BGE) solution consisting of 80 mM boric acid and 20 mM phosphate acid, adjusted to pH 8.1, with 15% acetonitrile (v/v) added, and applying a separation voltage of 28 kV. The SPE method was used for pretreating the complex matrix of botanical materials and good reproducibility was obtained when avicularin was used as internal standard. Linearity of the method was excellent with correlation coefficients (r 2) in the range of 0.9995–0.9999 and detection limits were lower than 0.6 μg/mL for the four flavonoids. The obtained recoveries varied between 93 to 104% while the relative standard deviations (RSDs) were below 4.4% (n = 3). The developed CZE method was successfully used for the separation of eight flavonoids and the quantification of the four flavonoids in five species of Flos Lonicerae.
Optimization of microwave‐assisted extraction for alizarin and purpurin in Rubiaceae plants and its comparison with conventional extraction methods
Authors: Dabiri Minoo , Salimi Shabnam , Ghassempour Alireza , Rassouli Ali , Talebi Mohammad 
Published: February 2005

AbstractA simple and rapid microwave‐assisted extraction (MAE) procedure was developed and optimized for two common color pigments, alizarin and purpurin, in various samples of Rubiaceae plants. Several variables that can potentially affect the extraction efficiency, namely temperature, methanol concentration in the extractant mixture, time, and solvent volume were optimized by means of a central composite design approach. The results suggest that temperature and methanol concentration in the solvent mixture are statistically the most significant factors. The separation and quantitative determination of the pigments was carried out in less than 6 min by a developed high‐performance liquid chromatographic method with UV detection at 250 nm. Under optimum operating conditions, MAE showed significantly higher recoveries than those obtained by the conventional extraction methods (ultrasonic and reflux extraction), ranging from 84 to 94%. In addition, a drastic reduction of the extraction time (20 min versus 6 h) and solvent consumption (20 versus 100 mL) was achieved with a reproducibility (RSDs < 10%) comparable with that provided by the reflux extraction as a reference method.
Statistical‐overlap theory for elliptical zones of high aspect ratio in comprehensive two‐dimensional separations
Authors: Davis Joe M. 
Published: February 2005

AbstractThe low prediction by statistical‐overlap theory of the numbers of singlets and peaks in two‐dimensional separations containing zones represented by either circles of small number or eccentric ellipses of any number is shown to result from use of probability expressions for unbound spaces of infinite extent. An exact theory is derived for the probability of singlet formation in a reduced two‐dimensional space of unit length, width, and area. The probability is a weighted sum of the probabilities of singlet formation in the interior, edge, and corner regions of the space, which depend only on saturation. The weighting factors are the fractions of area associated with each region and depend on the number of zones, the aspect ratio, the saturation, and the ellipse's spatial orientation. The average numbers of doublets, triplets, and peaks in the space are approximated by combining these results with Roach's equations describing the clustering of circles in an unbound two‐dimensional space. Simulations show that theory predicts the number of singlets, doublets, triplets, and peaks, when the number of zones is 25 or more, the aspect ratio is 100 or less, and the saturation is 2 or less. The relationship is derived between the aspect ratios of ellipses in the reduced space and actual separation space. Calculations are presented for comprehensive two‐dimensional gas chromatography.
Determination of organic acids in aerosol particles from a coniferous forest by liquid chromatography–mass spectrometry
Authors: Anttila Piia , Hyötyläinen Tuulia , Heikkilä Anu , Jussila Matti , Finell Johan , Kulmala Markku , Riekkola Marja‐Liisa 
Published: February 2005

AbstractLC–MS methods with use of ion‐trap and time‐of‐flight mass spectrometers were developed for the determination of organic acids in aerosol samples collected by a high‐volume sampler in a Finnish coniferous forest. Comparison was made of the composition of samples collected during atmospheric formation of new aerosol particles and on days when this formation did not occur. A dynamic sonication‐assisted solvent extraction system was developed for fast and quantitative extraction of the filter samples. Several organic acids, including pinonic acid, pinic acid, and homologuous series of n‐alkanoic acids, n‐alkenoic acids, and aliphatic dicarboxylic acids, were identified. In samples collected between 08:00 and 16:00 hours the concentration of pinonic acid ranged from 0.5 ng m–3 to 3.7 ng m–3 and that of pinic acid from 0.2 ng m–3 to 1.5 ng m–3. For most of the compounds identified, the trends in concentration could be explained by the differences in temperature during collection. However, concentrations of short‐chain n‐alkanoic acids were clearly higher on the days when new aerosol particle formation occurred.
Size fractionation of marine sediments by pinched inlet gravitational split‐flow thin fractionation and the study of size dependent PCDD/Fs concentrations from different bay areas
Authors: Moon Myeong Hee , Kim Hyun‐Joo , Jung Young‐Ok , Lee Se‐Jin , Chang Yoon‐Seok 
Published: February 2005

AbstractPinched inlet gravitational split‐flow thin fractionation (PI‐GSF) has been applied to the continuous size fractionation of marine sediments in order to study the difference in sediment size distribution and the concentration of PCDD/Fs contained in different particle sizes. A PI‐GSF channel, known to improve the separation efficiency by reducing the sample inlet thickness, was utilized to fractionate sediments collected from three different bay areas (Geoje, Ulsan, and Pohang) in Korea into 5 different sub‐populations (< 2.0, 2.0–5.0, 5.0–10, 10–20, 20–63 μm in diameter). The sorted sediment fractions from PI‐GSF were examined using electron microscopy to obtain size distribution and the results showed a variation in particle size distribution between bay areas. When the collected particle fractions were examined for size dependent levels of PCDD/Fs, the concentrations of total PCDD/Fs were shown to be much greater for samples collected close to heavy industry complexes than sediments from bay areas without major industry.
Atom Transfer Radical Copolymerization of α‐Olefins with Methyl Acrylate: Determination of Activation Rate Parameters
Authors: Venkatesh Rajan , Vergouwen Frank , Klumperman Bert 
Published: February 2005

AbstractSummary: The activation rate parameters of three model compounds for an acrylate/α‐olefin atom transfer radical copolymerization were investigated. It appeared that the activation of the model compound for the dormant acrylate chain (methyl‐2‐bromopropionate) was quite fast (kact = 0.018 (±0.001) L · mol−1 · s−1 at 0 °C). The activation of the model compound for the dormant α‐olefin chain end (2‐bromobutane) did not take place at any appreciable rate (0 and 35 °C). The introduction of a penultimate acrylate unit in the model compound for the dormant α‐olefin chain end (H‐MA‐hexene‐Br) did not result in any activation at 0 and 35 °C. Only at 70 °C some activation was visible after 18 h reaction time. By inference, these results confirm our earlier conclusion that the ATR copolymerization of acrylates and α‐olefins is possible due to the fast crosspropagation of an α‐olefin chain end radical with an acrylate.1H NMR spectra for the MBrP/Cu(I)Br/PMDETA/hydroxy TEMPO (1/10/10/10) mixture.magnified image1H NMR spectra for the MBrP/Cu(I)Br/PMDETA/hydroxy TEMPO (1/10/10/10) mixture.
Cover Picture: Macromol. Rapid Commun. 5/2005
Authors: Wong Wai‐Yeung , Wong Chun‐Kin , Poon Suk‐Yue , Lee Albert W.‐M. , Mo Tian , Wei Xin 
Published: February 2005

Cover: The cover picture shows the molecular architecture and the absorption and emission spectra of a novel rod‐like polyyne polymer comprised of an electron‐rich platinum framework and an electron‐accepting silole unit that features an alternating donor‐π‐acceptor (D‐π‐A) type structural motif. This polymer exhibits a very low band gap and interesting optoelectronic properties.Further details can be found in the Communication by W.‐Y. Wong,* C.‐K. Wong, S.‐Y. Poon, A. W.‐M. Lee, T. Mo, and X. Wei on page 376.
PA‐6 and EVA alloy/clay nanocomposites as char forming agents in poly(propylene) intumescent formulations
Authors: Tang Yong , Hu Yuan , Xiao Junfeng , Wang Jun , Song Lei , Fan Weicheng 
Published: February 2005

AbstractThis study investigates the influence of nylon‐6 (PA‐6) and ethylene‐vinyl acetate copolymer (EVA) alloy/clay nanocomposites on the properties of the flame‐retardant (FR) poly(propylene). Cone calorimetry and scanning electron microscopy (SEM) techniques were used to investigate the effect of PA‐6 and EVA alloy nanocomposites on the fire properties and dispersion of intumescent flame‐retardants (IFRs). The experimental results show that PA‐6 and EVA alloy nanocomposites improve the fire and mechanical properties of the FR poly(propylene). It is also shown that the improvement of the properties mainly depends on the weight ratio of PA‐6 and EVA in the alloys. The probable mechanisms are discussed in this paper. Copyright © 2005 John Wiley & Sons, Ltd.
Holographic polymer‐dispersed liquid crystal fabrication under electric field
Authors: Shin Eui Young , Jung Ju Ai , Hee Kim Eun , Kim Byung Kyu 
Published: February 2005

AbstractThe transmission mode of holographic polymer‐dispersed liquid crystals (HPDLCs) was developed an under electric field. It is reported that orientation of LC molecules under an electric field induces orientation of oligomer molecules giving rise to low off‐state diffraction and small grating shrinkage. Copyright © 2005 Society of Chemical Industry
Effects of injection‐molding processing parameters on acetaldehyde generation and degradation of poly(ethylene terephthalate)
Authors: Shukla Shunahshep R , Lofgren Elizabeth A , Jabarin Saleh A 
Published: February 2005

AbstractThe acetaldehyde (AA) generation behavior of poly(ethylene terephthalate) (PET) has been investigated in terms of its relationship to changes in various processing conditions. A single‐cavity injection‐molding machine was used to prepare preforms in order to relate changes in barrel temperature, screw shear rate, back pressure, cooling time and total residence time to levels of AA generated during processing. Within the temperature range 280–300 °C, a 10 °C rise in processing temperature causes AA production to double. Shear rate increases from 20 to 40 m min−1 result in 13–21 % increases in AA generation at temperatures from 300 to 280 °C. Increased back pressures from 0 to 200 bar result in AA concentration increases of about 1.2 ppm for each 50 bar pressure increase. The majority of this change is caused by increased polymer residence time. Longer cooling times also increase overall cycle times and result in higher levels of AA generation, at the rate of almost 7 ppm per additional minute at 290 °C processing conditions. Apparent activation energies of 167 kJ mol−1 were calculated for samples prepared at various shear rates. These results are in agreement with literature values obtained under conditions of static mixing and indicate that shear rate and plastication do not significantly affect reaction mechanisms for AA generation. Copyright © 2005 Society of Chemical Industry
The effect of higher order RNA processes on changing patterns of protein domain selection: A developmentally regulated transcriptome of type 1 inositol 1,4,5‐trisphosphate receptors
Authors: Regan Melissa R. , Lin Doris D.M. , Emerick Mark C. , Agnew William S. 
Published: February 2005

AbstractThe domain structure of proteins synthesized from a single gene can be remodeled during tissue development by activities at the RNA level of gene expression. The impact of higher order RNA processing on changing patterns of protein domain selection may be explored by systematically profiling single‐gene transcriptomes. itpr1 is one of three mammalian genes encoding receptors for the second messenger inositol 1,4,5‐trisphosphate (InsP3). Some phenotypic variations of InsP3 receptors have been attributed to hetero‐oligomers of subunit isoforms from itpr1, itpr2, and itpr3. However, itpr1 itself is subject to alternative RNA splicing, with 7 sites of transcript variation, 6 within the ORF. We have identified 17 itpr1 subunit species expressed in mammalian brain in ensembles that change with tissue differentiation. Statistical analyses of populations comprising >1,300 full‐length clones suggest that subunit variation arises from a variably biased stochastic splicing mechanism. Surprisingly, the protein domains of this highly allosteric receptor appear to be assembled in a partially randomized way, yielding stochastic arrays of subunit species that form tetrameric complexes in single cells. Nevertheless, functional expression studies of selected subunits confirm that splicing regulation is connected to phenotypic variation. The potential for itpr1 subunits to form hetero‐tetramers in single cells suggests the expression of a developmentally regulated continuum of molecular forms that could display diverse properties, including incremental sensitivities to agonist activation and varying patterns of Ca2+ mobilization. These studies illuminate the extent to which itpr1 molecular phenotype is induced by higher order RNA processing. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Spatial variability in the mineralisation of the phenylurea herbicide linuron within a Danish agricultural field: multivariate correlation to simple soil parameters
Authors: Rasmussen Jim , Aamand Jens , Rosenberg Per , Jacobsen Ole S , Sørensen Sebastian R 
Published: February 2005

AbstractThe spatial variability in the mineralisation rate of linuron [N‐(3,4‐dichlorophenyl)‐N′‐methoxy‐N′‐methylurea] was studied within a previously treated Danish agricultural field by sampling soils from eleven different plots randomly distributed across an area of 20 × 20 m. The soils were characterised with respect to different abiotic and biotic properties including moisture content, organic matter content, pH, nutrient content, bacterial biomass, potential for mineralisation of MCPA [(4‐chloro‐2‐methylphenoxy)acetic acid] and linuron. Five soils had a potential for mineralisation of linuron, with 5–15% of the added [ring‐U‐14C]linuron metabolised to 14CO2 within 60 days at 10 °C, while no extensive mineralisation of linuron was observed in the six remaining soils within this period. A TLC analysis of the methanol‐extractable residues showed no development of 14C‐labelled metabolites from linuron in any of the samples. Multivariate analysis was conducted to elucidate relationships between the intrinsic properties of single soil samples and initial rate of linuron mineralisation. The analysis indicated that important soil parameters in determining the spatial heterogeneity included the Ctotal/Ntotal ratio, pH and the water‐extractable potassium contents, with the first of these highly negatively correlated and the last two highly positively correlated to the initial linuron mineralisation rate. This study shows that enhanced biodegradation of linuron may develop with successive field treatments, but that considerable in‐field spatial heterogeneity in the degradation rate still exists. Combined with a parallel enrichment study focused on the underlying microbial processes, the present results suggest that intrinsic soil properties affect the linuron‐metabolising bacterial population and thereby determine the spatial variability in the linuron mineralisation activity. Copyright © 2005 Society of Chemical Industry
Ionic conductivity and conductivity relaxation of potassium tellurite glasses
Authors: El‐Desoky M. M. , Ragab H. S. 
Published: February 2005

AbstractThe electrical conductivity and conductivity relaxation of xK2O–(100–x)TeO2 glasses have been investigation in the frequency range 40 Hz to 200 kHz and temperature range 300 to 473 K. From the density and molar volume, it may be noticed that with increasing K2O content the density decreases while the molar volume increases highlighting the fact that more nonbridging oxygens (NBOs) are formed in the network as the concentration of K2O is increased. The Anderson–Stuart model was employed to explain the dc activation energy. The frequency‐dependent electrical data have been analyzed in the framework of the conductivity and modulus formalisms. The decrease of the conductivity relaxation time with increasing content of K2O was explained in the framework of the structural model of tellurite glasses. The variation of the stretched exponential parameter β with composition was compared with those of lithium and sodium tellurite glasses and was explained in terms of cation–cation distance correlation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Imprinting magnetic memory cells in molecular based NiL2(C2H5OH)2 heterospin crystals
Authors: Morgunov R. , Gudoshnikov S. , Ossypian Yu. , Ovcharenko V. , Sagdeev R. , Skomarovskii V. , Tanimoto Y. 
Published: February 2005

AbstractThe distribution of local magnetic fields near the surface of plastically deformed molecular based NiL2(C2H5OH)2 heterospin single crystals was studied by a scanning SQUID microscope. It was found that local deformation by indentation causes ferromagnetic exchange interaction in NiL2(C2H5OH)2 crystals at unusually high temperatures (≥77 K) in the area ∼104 µm2 near the indentation pit. This magnetization	temperature is much higher than observed in the bulk of the undeformed crystal (∼5 K). An estimation shows that spin ordering could be concentrated around structural defects. It gives the possibility to make a premeditated imprinting having a magnetic structure and to distribute magnetic memory cells on a crystal surface. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Density functional studies on hydrogen‐bonded clusters of hydrogen halides and the interaction on halide anions
Authors: Nirmala V. , Kolandaivel P. 
Published: February 2005

AbstractDensity functional theory (DFT) calculations have been performed to study the structures and stability of X−·(HX)n=2–5clusters where X = F, Cl, Br at B3LYP/6‐311++G** level of theory. The presence of halide ions in these clusters disintegrates the hydrogen halide clusters. All the hydrogen halides are then hydrogen bonded to the centrally placed halide ions, thereby forming multiple hydrogen bonds. The interaction energies have been corrected for the basis set superposition error (BSSE) using Boy's counterpoise correction method. Evidence for the destruction of hydrogen bonds in hydrogen halide clusters due to the presence of halide ions is further obtained from topological analysis and natural bond orbital analysis. The chemical hardness and chemical potential have been calculated for all the anion clusters. The above analysis reveals that hydrogen bonding in these systems is not an essentially electrostatic interaction. The nature of the stabilization interactions operative in these multiple hydrogen‐bonded clusters has been explained in terms of many‐body contribution to interaction energies. From these studies, an attempt has been made to understand the nature of the molecular properties resulting from different electronegativities of the halogens. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005