bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxidative stress and DNA interactions are not involved in Enniatin‐ and Beauvericin‐mediated apoptosis induction
Authors: Dornetshuber Rita , Heffeter Petra , Lemmens‐Gruber Rosa , Elbling Leonilla , Marko Doris , Micksche Michael , Berger Walter 
Published: August 2009

AbstractThe fusariotoxins beauvericin (BEA) and the structurally related enniatins (ENN) are frequent contaminants of grain‐based food and feed. They exert potent cytotoxic activities based on apoptosis induction. Since it is known, that reactive oxygen species (ROS) and DNA damage lead to apoptotic cell death, this study aimed to clarify whether oxidative stress and DNA interactions are involved in ENN‐ and BEA‐induced cytotoxicity. Diverse cellular and molecular assays indicated that oxidative stress does not contribute to ENN‐ and BEA‐induced cytotoxicity. In contrast, both fusariotoxins were shown to exert moderate antioxidative activities. Moreover, only at high concentrations (>100 μM) both mycotoxins were found to intercalate substantially into dsDNA and to inhibit the catalytic activity of topoisomerase I and II. Furthermore, the potent cytotoxic activity of ENN and BEA was shown to be widely independent of cellular mismatch‐ and nucleotide excision repair pathways. Also the ataxia‐telangiectasia mutated (ATM) protein kinase, a well known DNA damage sensor, did not affect BEAs cytotoxic potential while in ENN‐induced cytotoxicity ATM had a detectable but not a major modulating influence. Together, our data suggest that ROS and DNA damage are not key factors in ENN‐ and BEA‐mediated cytotoxicity.
NMR determination of pKa values of indoloquinoline alkaloids
Authors: Grycová Lenka , Dommisse Roger , Pieters Luc , Marek Radek 
Published: August 2009

AbstractMalaria is one of the most serious global health problems. Isolating new therapeutic agents with potential antimalarial activity from natural sources or preparing such agents either semisynthetically or synthetically is one strategy for solving the problem of resistance constantly evolving to the drugs currently in use.For alkaloids, the acid–base dissociation constant, pKa, is an important characteristic, thought to be associated with biological activity. In this contribution, pKa values for several indoloquinoline alkaloids were determined by using 1H NMR spectroscopy in a mixture of solvents. The data were recalculated for water solutions using the correction factors reported previously. The structural dependence of the pKa values for cryptolepine and its isomers neocryptolepine, isocryptolepine and isoneocryptolepine as well as some substituted neocryptolepine derivatives is discussed. Copyright © 2009 John Wiley & Sons, Ltd.
Structural characterization of hypoglycin B, a diastereomeric dipeptide from the ackee fruit (Blighia sapida Koenig) by NMR experiments
Authors: Bowen‐Forbes Camille S. , Minott Donna A. 
Published: August 2009

AbstractThe dipeptide hypoglycin B, one of two toxins of the ackee fruit (Blighia sapida Koenig), was characterized for the first time by NMR spectral data, which led to the discovery that it exists naturally as a pair of diastereomers. No distinction was observed in the 1H NMR signals of the diastereomers; however, complete and distinct 13C NMR assignments for the individual diastereomers were made. The 13C NMR spectrum of hypoglycin B compared very well with that of the corresponding signals in the spectrum for hypoglycin A, which is one of its constituent amino acids. The 1H and 13C NMR assignments were further supported by DEPT, gCOSY, gHSQC and gHMBC experiments. Copyright © 2009 John Wiley & Sons, Ltd.
Chebyshev‐like root‐finding methods with accelerated convergence
Authors: Petković M. S. , Rančić L. , Petković L. D. , Ilić S. 
Published: August 2009

AbstractIterative methods for the simultaneous determination of simple or multiple complex zeros of a polynomial, based on a cubically convergent Chebyshev method, are considered. Using Newton's and Halley's corrections the convergence of the basic method of the fourth order is increased to five and six, respectively. The improved convergence is achieved with negligible number of additional calculations, which significantly increases the computational efficiency of the accelerated methods. One of the most important problems in solving polynomial equations, the construction of initial conditions that enable both guaranteed and fast convergence, is also studied for the proposed methods. These conditions are computationally verifiable since they depend only on initial approximations, the polynomial coefficients and the polynomial degree, which is of practical importance. Finally, modified methods of Chebyshev's type for finding multiple zeros and single‐step methods based on the Gauss–Seidel approach are constructed. Copyright © 2009 John Wiley & Sons, Ltd.
On the convergence of general stationary iterative methods for range‐Hermitian singular linear systems
Authors: Zhang Naimin , Wei Yi‐Min 
Published: August 2009

AbstractGeneral stationary iterative methods with a singular matrix M for solving range‐Hermitian singular linear systems are presented, some convergence conditions and the representation of the solution are also given. It can be verified that the general Ortega–Plemmons theorem and Keller theorem for the singular matrix M still hold. Furthermore, the singular matrix M can act as a good preconditioner for solving range‐Hermitian linear systems. Numerical results have demonstrated the effectiveness of the general stationary iterations and the singular preconditioner M. Copyright © 2009 John Wiley & Sons, Ltd.
Combined interior‐point method and semismooth Newton method for frictionless contact problems
Authors: Miyamura Tomoshi , Kanno Yoshihiro , Ohsaki Makoto 
Published: August 2009

AbstractIn the present paper, a solution scheme is proposed for frictionless contact problems of linear elastic bodies, which are discretized using the finite element method with lower order elements. An approach combining the interior‐point method and the semismooth Newton method is proposed. In this method, an initial active set for the semismooth Newton method is obtained from the approximate optimal solution by the interior‐point method. The simplest node‐to‐node contact model is considered in the present paper, that is, pairs of matching nodes exist on the contact surfaces. However, the discussions can be easily extended to a node‐to‐segment or segment‐to‐segment contact model. In order to evaluate the proposed method, a number of illustrative examples of the frictionless contact problem are shown. The proposed combined method is compared with the interior‐point method and the semismooth Newton method. Two numerical examples that are difficult to solve using the semismooth Newton method are solved effectively using the proposed combined method. It is shown that the proposed method converges within far fewer iterations than the semismooth Newton methods or the interior‐point method. Copyright © 2009 John Wiley & Sons, Ltd.
Autonomy or organisation? Reforms in the Ghanaian internal revenue service
Authors: Joshi Anuradha , Ayee Joseph 
Published: August 2009

AbstractAutonomous Revenue Authorities (ARAs) have recently become a popular organisational reform to improve revenue collection in developing countries. The success of ARAs is commonly attributed to ‘autonomy’ which reduces political interference, and increases financial independence and managerial freedom. This article examines the case of the Ghanaian ARA – the Internal Revenue Service and argues that its strong performance is the result of not ‘autonomy’, but other more nuts and bolts reforms, specifically: (a) strategies designed to direct the focus of the IRS to different taxpayer segments, particularly the informal sector and (b) significant attempts to bring the tax administration closer to the taxpayer through decentralisation and improved taxpayer services. To the extent that autonomy enables ARAs to undertake these other reforms it forms an important piece of the picture, however, they do not require autonomy – they could well be adopted under traditional tax administrations. Copyright © 2009 John Wiley & Sons, Ltd.
New thermally stable and organosoluble heterocyclic poly(naphthaleneimide)s
Authors: Damaceanu Mariana‐Dana , Rusu Radu‐Dan , Bruma Maria , Rusanov Alexander L. 
Published: August 2009

AbstractAs majority of polyheteroarylenes based on bis(naphthalic anhydrides), are difficult to process due to their infusiblity and insolubility in common organic solvents and solubility only in strong acids, this study is concerned with the synthesis and properties of new, easily processable polyimides and copolyimides containing naphthalene and oxadiazole rings. These polymers have been synthesized and their properties have been compared with regard to the influence of oxadiazole and naphthalene units on their physical properties. The polyimides were prepared by polycondensation reaction in solution of the aromatic diamines containing preformed oxadiazole ring with two dianhydrides having naphthalene units, at high temperature. Also, copolyimides were prepared by using a mixture of each naphthalene‐containing dianhydride, with hexafluoroisopropylidene‐dianhydride in the polycondensation reaction with the same diamino‐oxadiazoles. Most of the resulting polyimides and copolyimides were soluble in polar amidic solvents and in less polar solvents, and their solutions gave flexible films when spread onto glass plates. The thermal stability and glass transition temperature of these polyimides and copolyimides were measured and compared. The quality and the roughness of the spin‐coated films of these polymers were investigated by atomic force microscopy. The photoluminescence properties of the polymers in solution were studied to determine the color of emission. The UV absorption was also studied to determine the Stokes shift, and hence the possible reabsorption effects. The properties of the present polyimides make them attractive for applications in advanced optoelectronics and other related fields. Copyright © 2009 John Wiley & Sons, Ltd.
Bilateral gonadoblastoma with dysgerminoma and pilocytic astrocytoma with WT1 GT‐IVS9 mutation: A 46 XY phenotypic female with Frasier syndrome
Authors: Subbiah Vivek , Huff Vicki , Wolff Johannes E.A. , Ketonen Leena , Lang Frederick F. , Stewart John , Langford Lauren , Herzog Cynthia E. 
Published: August 2009

AbstractFrasier syndrome is characterized by a 46 XY disorder of sex development, nephropathy, and increased risk for gonadoblastoma due to Wilms tumor 1(WT1) mutation in the donor splice site of intron‐9, resulting in the splice form +KTS. Germ cell tumors and gonadoblastomas have been reported previously in Frasier syndrome. We present the clinical, radiological, and genetic (WT1 mutation analysis) of a 46 XY phenotypic female with Frasier syndrome with bilateral gonadoblastoma with dysgerminoma who developed pilocytic astrocytoma. Pediatr Blood Cancer 2009; 53:1349–1351. © 2009 Wiley‐Liss, Inc.
Synthesis and characterization of poly(lactic acid) and aliphatic polycarbonate copolymers
Authors: Yu Tao , Ren Jie , Gu Shuying , Yang Ming 
Published: August 2009

AbstractBACKGROUND: Poly(lactic acid) (PLA) has received much attention as a biodegradable polymer. But the physical properties of PLA, such as brittleness, limit its wider applicability. Copolymerization polymers ing soft blocks provides a useful method to improve the mechanical properties of PLA.RESULTS: Poly(lactic acid)‐block‐(polycarbonate diol) (PLA‐PCD) copolymers were synthesized using a two‐step process with polycondensation and chain extension reactions. The effect of polycarbonate diol content on the prepolymer properties was studied. The chain‐extended products were characterized using 1H NMR, F and. The effect of the NCO/OH ratio on the properties of the chain‐extended products, including the mechanical properties and thermal properties, was studied. eight‐average molecular weight of the product can reach 210 000 g mol−1 when the molar ratio of NCO to OH is 3:1.CONCLUSION: The PLA‐PCD copolymers obtained can crystallize, and the crystallinity decreases with chain‐extension reaction. The products exhibit superior mechanical properties with elongation at break above 230%, which is much higher than that of PLA chain‐extended products. The products have a good potential for packaging applications. Copyright © 2009 Society of Chemical Industry
Reactivity of acrylamide as an alkylating agent: a kinetic approach
Authors: Céspedes‐Camacho Isaac F. , Manso José A. , Pérez‐Prior M. Teresa , Gómez‐Bombarelli Rafael , González‐Pérez Marina , Calle Emilio , Casado Julio 
Published: August 2009

AbstractAcrylamide (AA), an industrially produced reactive molecule, is used worldwide. The US EPA and IARC have classified this molecule as a probable human carcinogen. In this work, the alkylating potential of AA was investigated kinetically. The conclusions drawn are as follows: (i) AA shows alkylating ability on the nucleophile 4‐(p‐nitrobenzyl)pyridine (NBP), a trap for alkylating agents with nucleophilic characteristics similar to those of DNA bases; (ii) the rate equation for the NBP–AA adduct formation is as follows: $r = k_{{\rm alk}} \left[ {{\rm AA}} \right]\left[ {{\rm NBP}} \right]$; (ii) the thermoentropic term, TΔ‡Sθ, is the main term responsible for the lower reactivity of AA as an alkylating agent; (iii) the value of the Gibbs energy of activation, Δ‡Gθ, for the NBP alkylation reaction by AA is consistent with the conclusions of epidemiologic studies concerning the carcinogenicity of this substance; (iv) the results obtained here may be useful when working with hydrophilic/lipophilic media, such as in Food Science, since the dielectric constant of the medium, where alkylation occurs, influences the reaction rate, and alkylation can be inhibited by lowering the dielectric constant of the medium. Copyright © 2009 John Wiley & Sons, Ltd.
Silver metal nanoparticles: Facile dendrimer‐assisted size‐controlled synthesis and selective catalytic reduction of chloronitrobenzenes
Authors: Sutton Amy , Franc Grégory , Kakkar Ashok 
Published: August 2009

AbstractA simple and versatile synthetic methodology to silver metal nanoparticles that utilizes 3,5‐dihydroxybenzyl alcohol‐based dendrimers as templates and does not necessitate the addition of any external reducing agent is reported. An evaluation of the role of addition rate of the silver acetate solution, and the dendrimer to silver acetate molar ratio, as well as the dendritic effect on nanoparticle growth, suggests that the size of these metal nanoparticles can be controlled by simple variations of these parameters. A probe of the mechanism of the nanoparticle formation and growth indicates that the terminal hydroxyl groups of the dendrimers play a major role in metal ion isolation and reduction, in addition to providing stabilization to the growing metal particles. These silver metal nanoparticles are highly active catalysts for the selective reduction of chloronitrobenzenes to chloroanilines. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4482–4493, 2009
Synthesis of well‐defined azide‐terminated poly(vinyl alcohol) and their subsequent modification via click chemistry
Authors: Tong Yin‐Yin , Wang Rui , Xu Ning , Du Fu‐Sheng , Li Zi‐Chen 
Published: August 2009

AbstractA new azide‐functionalized xanthate, S‐(4‐azidomethylbenzyl) O‐(2‐methoxyethyl) xanthate, was synthesized and used to mediate the reversible addition fragmentation chain transfer polymerization of vinyl acetate. The polymerization was demonstrated to be controlled, and well‐defined PVAc with α‐azide, ω‐xanthate groups were obtained, the xanthate groups of which were further removed by radical‐induced reduction with lauroyl peroxide in the presence of excess 2‐propanol. Hydrolysis of α‐azide‐terminated PVAc (N3‐PVAc) led to the formation of the corresponding α‐azide‐terminated PVA (N3‐PVA). Finally, end‐modification of N3‐PVA by click chemistry with alkyne‐end‐capped poly(caprolactone) (A‐PCL), alkynyl‐mannose, and alkynyl‐pyrene was carried out to obtain a new block copolymer PCL‐b‐PVA, and two PVA with mannose or pyrene as the end functional groups. The polymers were characterized by gel permeation chromatography, 1H NMR spectroscopy, and FTIR. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4494–4504, 2009
Controlled reduction of polypropylene isotacticity and crystallinity by epimerization during reactive processing
Authors: Henry Gaëtan R. P. , Drooghaag Xavier , Vandeuren Mikhaël , Sclavons Michel , Schanck André , Devaux Jacques , Carlier Véronique , Marchand‐Brynaert Jacqueline 
Published: August 2009

AbstractAmorphous and low crystallinity polypropylenes were produced by reactive processing of commercial isotactic polypropylenes in the presence of a peroxide (2,5‐dimethyl‐2,5‐di(tert‐butylperoxy)hexane) and N‐bromosuccinimide. Characterization of the modified polypropylene microstructures using 13C NMR spectroscopy revealed that crystallinity loss is correlated with the epimerization of numerous methynes randomly along the polymer backbone, leading to decreasing isotacticities ([mmmm]) and average isotactic block lengths. Moreover, degradation usually induced by peroxide was shown to be comparatively limited in additional presence of N‐bromosuccinimide. This fast and easy process therefore allows the production of polypropylene plastomers and elastomers with controlled and homogeneous crystallinities and isotacticities, and relatively low molecular weight distributions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4505–4518, 2009
Study of electrical, mechanical, and nanoscale free‐volume properties of NBR and EPDM rubber reinforced by bentonite or kaolin
Authors: EL‐Nashar D. E. , Gomaa E. , Abd‐El‐Messieh S. L. 
Published: August 2009

AbstractThe effect of Na bentonite, Ca bentonite, and kaolin fillers on the macrostructure and microstructure of acrylonitrile butadiene rubber, ethylene propylene diene rubber, and their blend (50/50) was studied through electrical and mechanical measurements, as well as with positron annihilation lifetime spectroscopy. The real part of permittivity (ε′), dielectric loss (ε″), and the crosslinking density were found to increase with increasing filler content. The increase of crosslinking density of the blend with increasing amount of fillers reflects a decrease in the equilibrium swelling up to 21.50 wt % compared with that of the unfilled blends. The mechanical investigation showed pronounced increase in the tensile strength, and in elongation at break with the addition of up to 21.50 wt % of filler. In addition, comparing between different fillers showed that the reinforcing effect of Na bentonite is more effective than Ca bentonite and kaolin but the physico‐mechanical of Ca bentonite is less than that for kaolin. The positron annihilation lifetime measurements revealed that the free‐volume properties were strongly affected by the amount and type of filler, in particular, the free‐volume fraction was dramatically decreased with increasing filler content. Furthermore, correlations were made between the free‐volume parameters and both electrical and mechanical properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1825–1838, 2009
Self‐association of cellulose ethers with random and regioselective distribution of substitution
Authors: Sun Shaomin , Foster Timothy J. , MacNaughtan William , Mitchell John R. , Fenn Dominik , Koschella Andreas , Heinze Thomas 
Published: August 2009

Abstract2 to 4% aqueous solutions of regioselectively substituted 3‐mono‐O‐ethyl‐ (3‐EC) and randomly substituted ethyl‐ (EC) cellulose show association and gelation above 50–60 and 20–30 °C, respectively. In contrast, almost no association or gelation was seen with regioselectively substituted 3‐mono‐O‐methoxyethyl cellulose (3‐MEC). This could be assessed by eye and measured using the techniques of 1H high‐resolution nuclear magnetic resonance, oscillatory rheology, and micro‐differential scanning calorimetry (DSC). Several processes are thought to occur during association and gelation of EC and 3‐EC. These were separated with respect to temperature, to varying degrees, on cooling and have been modeled using DSC data. In accordance with other work in the literature, they are thought to be, on heating, the disassociation of structures in solution followed first by the formation of water cages and then by the association of hydrophobic moieties into a precipitate or gel. Contrasting with previous work (Haque and Morris, Carbohydr Polym 1993, 22, 161–173), the rheological measurements do not show “two distinct waves of structure formation” at the present concentrations and the DSC measurements show, on cooling, an extremely wide separation in temperature of the processes for the regioselectively substituted cellulose derivative 3‐EC. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1743–1752, 2009
Physical aging and structural relaxation in polymer nanocomposites
Authors: Liu Amy Y.‐H. , Rottler Jörg 
Published: August 2009

AbstractMolecular dynamics simulations of a coarse‐grained polymer nanocomposite model are used to study the impact of nanoparticles on physical aging. The physical aging rate of the composites is obtained from measurements of the per‐particle pair energy, while the (segmental) mean‐squared displacement and creep compliance are used to probe simultaneously the dependence of structural relaxation times on waiting time elapsed since the glass was formed. Although bulk regions behave similarly to a neat polymer glass, interfacial regions exhibit a reduction in the physical aging rate for attractive polymer–nanoparticle interactions. Repulsive interactions lead instead to a significant increase. This change in physical aging rate is found to be proportional to the local mobility of the polymer atoms. By contrast, aging exponents obtained from time‐waiting time superposition of mean‐squared displacements or compliance curves are much less affected by the nanoinclusions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1789–1798, 2009
Thermodynamic and kinetic thermal analyses on dual crystal forms in polymorphic poly(heptamethylene terephthalate)
Authors: Yen Kai‐Cheng , Woo Eamor M. 
Published: August 2009

AbstractThermal analyses were performed for determining the equilibrium melting temperatures T of the respective α‐ and β‐crystal in melt‐crystallized polymorphic poly(heptamethylene terephthalate) (PHepT) using both linear and nonlinear Hoffman‐Weeks (H‐W) methods for comparison of validity. These two crystals in PHepT do not differ much in their melting temperatures. The equilibrium melting temperatures of the α‐ and β‐crystal as determined by the linear H‐W method are 98 °C and 100.1 °C, respectively; but the nonlinear H‐W method yielded higher values for both crystals. The equilibrium melting temperatures of the α‐ and β‐crystal according to the nonlinear H‐W method are 121 °C and 122.5 °C, respectively. Both methods consistently indicate that T of the β‐crystal is only slightly higher than that of the α‐crystal. Such small difference in T between the α‐ and the β‐crystal causes difficulties in judging the relative thermodynamic stability of these two crystals. Thus, kinetics of these two crystals was compared using the Avrami and Ozawa theory. The crystallization produced by quenching from Tmax = 110 °C and 150 °C shows a heterogeneous and homogeneous nucleation mechanism, respectively. The lower Tmax = 110 °C leads to heterogeneous nucleation and only α‐crystal in PHepT, whose crystallization rates at same Tc are much higher than crystallization rates by quenching from Tmax = 150 °C leading to either α‐ or β‐crystal with homogeneous nucleation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1839–1851, 2009