bluuebunny/crossref_metadata_2025_split huggingface dataset:
Joint neighbors approximation of macromolecular solvent accessible surface area
Authors: Rychkov Georgy , Petukhov Michael 
Published: April 2007

AbstractA new method for approximate analytical calculations of solvent accessible surface area (SASA) for arbitrary molecules and their gradients with respect to their atomic coordinates was developed. This method is based on the recursive procedure of pairwise joining of neighboring atoms. Unlike other available methods of approximate SASA calculations, the method has no empirical parameters, and therefore can be used with comparable accuracy in calculations of SASA in folded and unfolded conformations of macromolecules of any chemical nature. As shown by tests with globular proteins in folded conformations, average errors in absolute atomic surface area is around 1 Å2, while for unfolded protein conformations it varies from 1.65 to 1.87 Å2. Computational times of the method are comparable with those by GETAREA, one of the fastest exact analytical methods available today. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Scaleable purification process for gene therapy retroviral vectors
Authors: Rodrigues Teresa , Carvalho Andreia , Carmo Marlene , Carrondo Manuel J. T. , Alves Paula M. , Cruz Pedro E. 
Published: April 2007

AbstractBackgroundRetroviral vectors (RVs) constitute one of the preferred gene therapy tools against inherited and acquired diseases. Development of scaleable downstream processes allowing purification under mild conditions and yielding viral preparations with high titer, potency and purity is critical for the success of clinical trials and subsequent clinical use of this technology.MethodsA purification process for murine leukaemia virus (MLV)‐derived vector supernatants was developed based on membrane separation and anion‐exchange chromatography (AEXc). Initial clarification of the vector stocks was performed using 0.45 µm membranes followed by concentration with 500 kDa molecular weight cut‐off (MWCO) membranes; further purification was performed by AEXc using a tentacle matrix bearing DEAE functional ligands. Finally, concentration/diafiltration was performed by 500 kDa MWCO membranes. To validate final product quality the process was scaled up 16‐fold.ResultsOptimization of microfiltration membrane pore size and ultrafiltration transmembrane pressure allowed the recovery of nearly 100% infectious particles. Further purification of the RVs by AEXc resulted in high removal of protein contaminants while maintaining high recoveries of infectious vectors (77 ± 11%). Up‐scaling of the process resulted in high titer vector preparations, 3.2 × 108 infectious particles (IP)/ml (85‐fold concentration), with an overall recovery reaching 26%. The process yielded vectors with transduction efficiencies higher than the starting material and more than 99% pure, relative to protein contamination.ConclusionsThe combination of membrane separation and AEXc processes results in a feasible and scaleable purification strategy for MLV‐derived vectors, allowing the removal of inhibitory contaminants thus yielding pure vectors with increased transduction efficiencies. Copyright © 2007 John Wiley & Sons, Ltd.
Characterization of antimicrobial histone sequences and posttranslational modifications by mass spectrometry
Authors: Ouvry‐Patat Séverine A. , Schey Kevin L. 
Published: April 2007

AbstractHistones typically play a role in DNA packaging and transcription regulation. These proteins are heavily modified by acetylation, methylation, phosphorylation and/or ubiquitination, and various combinations of these modifications alter histone functions and form the basis of the histone code. Furthermore, histones, including those found in shrimp, have recently been found to possess antimicrobial properties; however, the sequences and posttranslational modifications of shrimp histones are largely unknown. In this study mass spectrometry was used to characterize the primary structure of the shrimp antimicrobial histone. A combination of in‐solution digestion and in‐gel propionylation/digestion followed by LC‐MS‐MS and MALDI‐TOF‐TOF analysis was used. Over 80% of each histone sequence was obtained by in‐solution digestion; however, none of the N‐terminal domains was sequenced with this method. An in‐gel propionylation method was optimized to recover and sequence the extremely hydrophilic histone N‐termini. This method was then applied to shrimp hemocyte lysates separated on a 1‐D SDS‐PAGE gel. Overall, 95% coverage was obtained for the histone sequences as well as the identification of posttranslational sites such as acetylation, methylation and phosphorylation. Copyright © 2007 John Wiley & Sons, Ltd.
Exfoliation corrosion and electrochemical impedance spectroscopy of an Al‐Li alloy in EXCO solution
Authors: Li J.F. , Zheng Z.Q. , Li S.C. , Ren W.D. , Chen W.J. 
Published: April 2007

AbstractThe exfoliation corrosion and electrochemical impedance spectroscopy (EIS) of an Al‐2.8%Cu‐1.5%Li‐0.3%Mg‐0.3%Zn‐0.3%Mn‐0.15%Zr alloy with various aging states in EXCO solution were investigated. The equilibrium precipitates at grain boundaries are anodic to the alloy base at their adjacent periphery. With prolonging aging time, the amount and the size of the equilibrium precipitates at grain boundaries are increased, resulting in an enhanced susceptibility to exfoliation corrosion. At the beginning of immersion in EXCO solution, the EIS plot of the alloys is composed of a capacitive arc in the high frequency range and an inductive loop in the low frequency range. As immersion time is increased, two capacitive arcs appear in the high‐mediate and mediate‐low frequency ranges respectively and the appearance time of two capacitive arcs could be an indication of the speed of localized corrosion development in EXCO solution. The longer appearance time of two capacitive arcs of the under‐aged alloy indicates its slower localized corrosion development.
High temperature corrosion of alloy Haynes 556 in carburizing/oxidizing environments
Authors: Allam I.M. , Gasem Z.M. 
Published: April 2007

AbstractThe iron based alloy Haynes 556 has been recently used in hydrocarbon and carbonaceous environments due to its excellent resistance to carburization. This alloy outperforms stainless steels and some of the best commercial carburization‐resistant nickel‐based alloys. This paper is concerned with the behavior of alloy Haynes 556 in high temperature carburizing environments containing trace amounts of oxygen. Thermal cyclic exposures were conducted in 2% and 10% CH4/H2 gas mixtures at 800, 900, 1000, and 1100°C for 10 cycles, 50 h each. Carbon activities, oxygen partial pressures, and stabilities of oxides and carbides were used to identify the role played by the reaction products in providing protection. Thermodynamic analyses, weight changes, and microstructural characterization were correlated with environmental parameters and alloy composition to elucidate the causes of its marked resistance to carburization. The results indicate protective character in both gas mixtures under all exposure conditions except the most aggressive, namely 1100°C in 10% CH4/H2 gas mixture. Below 1000°C, the formation of Cr, Al, and Si oxides along with Cr carbides provides the primary means of protection. Catastrophic failure at 1100°C was manifested by extensive fracture and crack development within the outer substrate surface in the 10% CH4/H2 gas mixture resulting in a dramatic increase in weight gain. This has been attributed to the increased carbon pick‐up, coupled with the loss of the protective outer scales.
Necessary optimality conditions for fractional action‐like integrals of variational calculus with Riemann–Liouville derivatives of order (α, β)
Authors: El‐Nabulsi Rami Ahmad , Torres Delfim F. M. 
Published: April 2007

AbstractWe derive Euler–Lagrange‐type equations for fractional action‐like integrals of the calculus of variations which depend on the Riemann–Liouville derivatives of order (α, β), α>0, β>0, recently introduced by Cresson. Some interesting consequences are obtained and discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Controlled release of 2‐heptanone using starch gel and polycaprolactone matrices and polymeric films
Authors: Glenn Gregory M. , Klamczynski Artur P. , Shey Justin , Chiou Bor‐Sen , Holtman Kevin M. , Wood Delilah F. , Ludvik Charles , Hoffman Gloria DeGrandi , Orts William J. , Imam Syed 
Published: April 2007

AbstractVarroa jacobsoni is a parasitic mite that is threatening the honeybee industry in many parts of the world. 2‐Heptanone, a natural product made by honeybees at low concentrations, is effective at elevated concentrations in controlling mite populations in honeybee colonies, especially when released over a 42 day period. An extrusion process was used to encapsulate 14, 18, and 25% 2‐heptanone in a polycaprolactone (PCL) matrix. Less than 18% of the 2‐heptanone was encapsulated in the PCL matrix. The high vapor permeability of PCL to 2‐heptanone resulted in a high flux rate and limited the usefulness of PCL as an encapsulation matrix for controlled‐release devices. A starch gel containing three times its weight in 2‐heptanone was prepared from starch‐based microcellular foam (MCF). The gel had compressive, tensile, and flexural strength values in the range of 0.56 to 1.9 MPa. 2‐Heptanone quickly evaporated from non‐laminated gels. However, when the gel was laminated with different polymeric films, a wide range of flux rates was obtained. The T50 for gels laminated or coated with poly(vinyl alcohol) (PVAL, 99% hydrolyzed) and ethylene‐vinyl alcohol copolymer (EVAL) was 72 and 1030 days, respectively. The most promising film was a starch/glycerol film that released 50% of the 2‐heptanone (T50) in approximately 13 days. Copyright © 2007 John Wiley & Sons, Ltd.
Swelling characterization of novel ternary semi‐IPNs: acrylamide/1‐vinylimidazole/PEG hydrogels
Authors: Üzüm Ömer Barış , Karadağ Erdener 
Published: April 2007

AbstractNew ternary semi interpenetrating polymer networks (semi‐IPNs) systems containing acrylamide (AAm), 1‐vinylimidazole (VI) and poly (ethylene glycol) (PEG) have been prepared. AAm/VI hydrogels and semi‐IPN's, poly (AAm/VI/PEG) with 0.25, 0.50, 0.75 and 1.00 g of PEG (per 1.00 g AAm) were prepared by free radical solution polymerization in aqueous solution of AAm with VI as comonomer and a multifunctional crosslinker such as 1,4 butanediol dimethacrylate (BDMA). Swelling experiments were performed in water at 25°C, gravimetrically. The influence of VI and PEG content in hydrogels were examined. AAm/VI and AAm/VI/PEG hydrogels showed large extents of swelling in aqueous media, the swelling being highly dependent on the chemical composition of the hydrogels. Percentage swelling ratio of AAm/VI hydrogels and AAm/VI/PEG hydrogels was shown as 650–4167%. The values of equilibrium water content (EWC) of the hydrogels are between 0.8990 and 0.9750. Diffusion behavior was investigated. Water diffusion into hydrogels was found to be non‐Fickian in character. Copyright © 2007 John Wiley & Sons, Ltd.
TLC‐Densitometric analysis of artemisinin for the rapid screening of high‐producing plantlets of Artemisia annua L.
Authors: Koobkokkruad Thongchai , Chochai Araya , Kerdmanee Chalermpol , De‐Eknamkul Wanchai 
Published: April 2007

AbstractA simple TLC‐densitometric technique has been developed for the rapid and accurate analysis of artemisinin in a large number of Artemisia annua plantlets cultured in vitro. This new analytical method is based on the structural conversion of artemisinin on a silica gel layer by ammonia vapour to form 10‐azadesoxyartemisinin, a chromophore‐containing compound (λmax 320 nm) that can be detected by UV‐based TLC densitometry. The TLC system was evaluated quantitatively in terms of product stability, precision, accuracy and calibration. Good linearity was obtained in the range of 0.01–0.12 µg artemisinin. The technique appeared to be accurate and sensitive as compared with the complicated pre‐column reaction‐HPLC technique. Among 90 samples of A. annua plantlets, the artemisinin content in the leaves appeared to be highly variable, ranging from 0.02 to 0.67% w/w dry weight. These results demonstrate that densitometric TLC can be a cheap and simple technique for the accurate screening of high‐artemisinin‐producing plants. Copyright © 2007 John Wiley & Sons, Ltd.
Analysis of the essential oil from the roots of Eupatorium cannabinum subsp. corsicum (L.) by GC, GC‐MS and 13C‐NMR
Authors: Paolini Julien , Costa Jean , Bernardini Antoine‐François 
Published: April 2007

AbstractEupatorium cannabinum subsp. corsicum (L.) is an endemic subspecies from the island of Corsica. The essential oil from the roots of this aromatic plant has been studied by GC, GC‐MS and by 13C‐NMR. In contrast to the essential oil from the aerial parts, which is dominated by hydrocarbon compounds (76.9%) and particularly by sesquiterpene components (43.3%), the essential oil from the roots was characterized by a high content of oxygenated compounds (61.0%), particularly oxygenated monoterpenes (54.0%). In the root oil, 106 components were identified representing 96.1% of the total amount. This oil was dominated by the monoterpenes esters (33%), the major components of which were neryl isobutyrate (17.6%), thymyl methyl oxide (15.1%), δ‐2‐carene (14.5%) and β‐pinene (5.7%). Aromatic esters, nerol derivatives (esters and diesters) and a benzofuran were investigated by GC‐MS using different ionization modes including electron impact ionization, and positive‐ and negative‐chemical ionization. These components have not previously been reported in the essential oil of aerial parts of E. cannabinum from Corsica island. Copyright © 2007 John Wiley & Sons, Ltd.
Selective ultrasound‐assisted extractions of lipophilic constituents from Betula alleghaniensis and B. papyrifera wood at low temperatures
Authors: Lavoie J.‐M. , Stevanovic T. 
Published: April 2007

AbstractBetula alleghaniensis and B. papyrifera are widely distributed in the province of Québec (Canada) and, since these trees are valuable exports for the local lumber industry, large amounts of their residual ligneous biomass are available for further exploitation. Betula species are well known for their significant concentrations of triterpenes, some of which were recently discovered to present promising bioactivity. The secondary transformation of birch biomass could therefore become important for many industries, particularly the pharmaceutical industry. In the present study, extracts from birch sawdust were obtained using an optimised ultrasound‐assisted extraction in which the careful choice of temperature permitted a selective extraction of the targeted triterpenes. Moreover, compared with the classical Soxhlet method, higher extraction yields were obtained in a shorter time. The lipophilic extracts obtained using dichloromethane as a solvent were analysed by GC‐MS and the major compounds identified as lupane‐type cyclic triterpenoids accompanied by the non‐cyclic triterpene squalene. Numerous aliphatic long‐chain fatty acids were also found in the extracts together with phytosterols. Betulonic acid and squalene, the major extract constituents for both B. alleghaniensis and B. papyrifera, are both bioactive molecules. Copyright © 2007 John Wiley & Sons, Ltd.
Poly(ethylene oxide)/clay nanocomposites for solid polymer electrolyte applications
Authors: Ratna Debdatta , Divekar Swapnil , Patchaiappan Sivaraman , Samui Asit Baran , Chakraborty Bikash Chandra 
Published: April 2007

AbstractPoly(ethylene oxide) (PEO)/clay nanocomposites were prepared using a solution intercalation method. The organoclay (Nanocore I30E) used for nanocomposite synthesis was basically an octadecylammonium salt of montmorillonite clay prepared using an ion exchange method. Nanocomposite‐based solid polymer electrolytes were prepared using LiBF4. The nanocomposite structures were characterised using wide‐angle X‐ray diffraction. The crystallisation behaviour and thermal properties were studied using differential scanning calorimetry. It was found that the crystallinity of the composite electrolytes decreases with increasing clay concentration up to 7.5 wt% and then increases with a further increase in clay concentration. The trend is different from that observed in PEO/clay nanocomposites without lithium salt where the crystallinity gradually decreases with increasing clay concentration. The solid polymer electrolyte samples were evaluated using an alternating current impedance analyser. A considerable increase in room temperature conductivity was observed at the optimum clay concentration. The conductivity decreases beyond the optimum clay concentration. Copyright © 2007 Society of Chemical Industry
Effect of unsaturated chain end‐group on thermal oxidative behavior of polypropylene
Authors: Nakatani Hisayuki , Suzuki Shoutarou , Tanaka Takamasa , Terano Minoru 
Published: April 2007

AbstractIn order to clarify the influences of unsaturated chain end‐groups on the oxidative degradation of isotactic polypropylene (iPP), values of activation energy (ΔE) for the oxidative degradation reactions of Ziegler‐catalyzed iPP (ZiPP) and metallocene‐catalyzed iPP (MiPP) having similar tacticity were evaluated by the temperature dependence of the oxidation induction time as determined by thermogravimetric analysis over the range 130–145 °C. The correlation between the content of unsaturated chain end‐groups and the change of ΔE was also studied. The results obtained indicated that the unsaturated chain end‐groups strongly influenced the rate of iPP degradation. Moreover, on addition of oligomer‐like MiPP having unsaturated chain end‐groups, the ΔE value of ZiPP became lower, suggesting that iPP having unsaturated chain end‐groups served as an infectious agent of the degradation. Copyright © 2007 Society of Chemical Industry
Monodisperse polymeric spheres in the micron size range by a single step process
Authors: Almog Yaacov , Reich Shimon , Levy Moshe 
Published: April 2007

AbstractA method for the formation of monodisperse polystyrene (PS) and polymethylmethacrylate (PMMA) spheres, in the micron diameter range, was developed. The polymerisation reaction was carried out in a series of alcohols, using homo‐ and co‐polymers as steric stabilisers in combination with a quaternary ammonium salt which probably acts as an electrostatic co‐stabiliser. Monodisperse PS spheres were formed in the particle size range of 1–6 μm, by a single step process. The size range could be extended by further addition of monomer to the reaction mixture during the polymerisation. The solubility parameter of the alcohol used and the nature of the surfactant determine the diameter of the resulting spheres. However, the concentration of surfactant did not seem to affect strongly the size of the spheres but only the dispersity.
Preparation and properties of phenolated phenanthrene‐formaldehyde resins
Authors: Herbert Lesley D. , Robinson J. Gordon , Marr George 
Published: April 2007

AbstractPhenanthrene‐formaldehyde resins of different oxygen content were reacted with phenol 110°C in the presence of a strong acid catalyst. Cleavage occurred at the dimethylene ether and acetal bridges joining the aromatic nuclei with the concomitant formation of phenanthrene‐formaldehyde‐phenol resins. These resins were characterised by gel permeation chromatography, 1H n.m.r. and infrared spectroscopy.
Study of cure of epoxy resins by torsional braid analysis
Authors: Lee W. Alex , Oliver Martin J. 
Published: April 2007

AbstractThe use of torsional braid analysis (TBA) for the dynamic mechanical characterisation of polymers in composites has been inhibited to some degree by difficulties associated with both the measurement and processing of data. Methods for overcoming difficulties associated with spurious motions of the TBA pendulum and for the rapid and optimum processing of raw output data are outlined. A description follows of the application of the modified TBA technique to the analysis of six nominally similar epoxy resins systems. It is shown, by the presentation of comparative data, that the TBA method gives highly reproducible results, with little scatter, in studies both of gelation and vitrification times over a wide range of isothermal temperatures, and of activation energies for the processes involved, and also in studies of dynamic mechanical behaviour over a wide temperature range.
Chromatographic studies of epoxy resins
Authors: Hinton Ian G. 
Published: April 2007

AbstractMethods are given for the‘derivatisation’ of various of the components of epoxy resins: after fractionation by g.p.c. but before further analysis by h.p.l.c. or g.p.c.This paper describes the use of the following reagents for this purpose: concentrated HCl (to convert epoxy groups into chlorohydrin units); solid NaOH (to convert 1, 2‐chlorohydrin groups into epoxy units); phenol (to open epoxy rings); N‐methylaniline (to open epoxy rings); and KMnO4 (to oxidise —CH2 — and — OCH2CHOHCH2O — bridging units).
The examination of some thermosetting polymers by inelastic electron tunnelling spectroscopy
Authors: Comyn John , Horley Colin C. , Oxley David P. , Pritchard Robert G. , Tegg Janet L. 
Published: April 2007

AbstractThis paper first discusses the principles of Inelastic Electron Tunnelling Spectroscopy (IETS) and describes the experimental procedures needed to obtain spectra. Spectra are presented for an epoxide resin and two aliphatic amine‐hardeners, and for epoxideamine mixtures both before and after a heat curing schedule. From the latter it can be seen that the normal curing reaction between amine and epoxide groups does not take place within an IETS junction. A possible reason for this is the adsoprtion of amines onto the aluminium oxide surface of the substrate.
Addition of polyethersulphone to epoxy resins
Authors: Bucknall Clive B. , Partridge Ivana K. 
Published: April 2007

AbstractPhase separation of polyethersulphone from solution in epoxy resins has been studied as a function of polyethersulphone concentration, type of resin, and curing conditions. The resins chosen were a rapidly curing tetrafunctional and a trifunctional epoxy resin, hardened with either diaminodiphenylsulphone, or dicyandiamide. Fracture surfaces of some of the cured blends exhibited nodular features between 0.2μm and 6μm in diameter. Using X‐ray microanalysis and scanning electron microscopy these nodules were shown to contain high concentrations of polyethersulphone. Mechanical properties, including fracture energy, dynamic mechanical relaxation and creep, were studied for the same range of blend compositions. Dynamic mechanical spectra provided further evidence for phase separation in certain blends, while elastic modulus, fracture toughness and creep showed little dependence upon composition.
Toughened multiphase thermosetting polymers
Authors: Kinloch A. J. 
Published: April 2007

AbstractIn recent years a new generation of advanced structural adhesives has become available. They are typically based upon epoxy resins modified by the presence of a second phase of dispersed rubbery particles. This multiphase microstructure results in the material possessing a considerably higher toughness or crack resistance, compared to the unmodified, single‐phase resin, but with only a minimal reduction in other important properties such as modulus and high‐temperature and creep resistance. Even more recently, polyimide adhesives have also been toughened employing this principle.The present paper considers the following aspects:

The chemistry of rubbery‐toughened thermosetting polymers developed for adhesive applications.
Structure‐property relationships of multiphase adhesives which incorporate a dispersed rubbery phase or rigid particulate fillers. The mechanisms of toughening are discussed and related to the microstructure. The effects of volume fraction, particle size and particle size distribution on the polymer's fracture energy are also described
The particular problems encountered when using such toughened multiphase adhesives in structural joints are reviewed, including aspects of joint design and environmental effects.