bluuebunny/crossref_metadata_2025_split huggingface dataset:
Viscoplastic constitutive modeling of polymers—Flow rules and the plane strain response
Authors: Sweeney J. , Naz S. , Coates P. D. 
Published: October 2008

AbstractPlane strain compression tests, measuring both axial and transverse forces, are performed on ultra‐high molecular weight polyethylene up to true axial strains of −0.4. As the deformation proceeds, the transverse stress becomes an increasing proportion of the axial stress, with the proportion growing from its initial value of 0.5 up to a value of 0.8. A constitutive model is applied that combines Ogden models and Eyring processes. It is found that when a Levy‐Mises flow rule is used in conjunction with the Eyring model, the predicted ratio of transverse to axial stress remains much smaller than that observed, and is not greatly affected by changes in the Ogden exponent. However, when the flow rule is replaced by one that incorporates strain‐induced anisotropy, realistic predictions are possible. For each Ogden model, we associate a flow rule for which the transverse strains in both the Ogden and Eyring models are individually zero. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Highly processable ternary systems based on benzoxazine, epoxy, and phenolic resins for carbon fiber composite processing
Authors: Rimdusit Sarawut , Jongvisuttisun Passarin , Jubsilp Chanchira , Tanthapanichakoon Wiwut 
Published: October 2008

AbstractEffects of resin compositions in ternary systems of benzoxazine, epoxy, and phenolic novolac resins on processability, and thermomechanical properties of their carbon fiber‐reinforced composites are investigated. At suitable range of resin mass ratios, the ternary mixtures can provide a relatively wide processing window ranging from 50 to 200°C by maintaining their low A‐stage viscosity for a relatively long time which is crucial in the fiber preimpregnating process. Furthermore, relatively long shelf‐life of the ternary mixtures stored at room temperature (∼ 30°C) up to 270 days is obtained with minimal effect on their processability. The optimum mass ratio of B : E : P was determined to be 3 : 6 : 2, i.e., BEP362 resin. Finally, the carbon fiber composite based on BEP362 was found to exhibit substantial enhancement in its mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Preparation and physical properties of LLDPE grafted with novel nonionic surfactants
Authors: Li Lili , Yin Jinghua , Costa Giovanna , Stagnaro Paola 
Published: October 2008

AbstractCopolymers of linear low‐density polyethylene (LLDPE) grafted with two novel nonionic surfactants, acrylic glycerol monostearate ester (AGMS) and acrylic polyoxyethylenesorbitan monooleate ester (ATWEEN80), containing hydrophilic and hydrophobic groups and 1‐olefin double bond were prepared by using a plasticorder at 190°C. To evaluate the grafting degree, two different approaches based on 1H‐NMR data were proposed, and FTIR calibration was showed to validate these methods. The rheological response of the molten polymers, determined under dynamic shear flow at small‐amplitude oscillations, indicated that crosslinking formation of the chains could be decreased with increasing the monomer concentration. Their thermal behavior was studied by DSC and polarization microscope (PLM): The crystallization temperature (TC) of grafted LLDPE shifted to higher temperature compared with neat LLDPE because the grafted chains acted as nucleating agents. Water and glycerol were used to calculate the surface free energy of grafted LLDPE films. The results indicated that the novel polyoxyethylene surfactant ATWEEN80 could greatly improve the hydrophilicity of LLDPE and the surface free energy varied from 33 mN/m of neat LLDPE to 106 mN/m of the grafted LLDPE film. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
A study on swelling behavior of poly(p‐chloro styrene) networks in some aromatic hydrocarbons and linear poly(p‐chloro styrene) solutions
Authors: Celik Onur , Sakar Dolunay , Cakar Fatih , Cankurtaran Ozlem , Karaman Ferdane 
Published: October 2008

AbstractCrosslinked networks (NPPCS) and linear polymers (LPPCS) of poly (p‐chloro styrene) were synthesized by free‐radical polymerization of p‐chloro styrene. NPPCS networks were swollen in four different molecular weights of LPPCS solutions in toluene at three different concentrations. The equilibrium swelling results were evaluated by means of Flory‐Rehner theory to obtain network–linear polymer interaction parameter, χ′23 between NPPCS and LPPCS. It was concluded that the parameter χ′23 decreased with molecular weight but increased with concentration of LPPCS in outer solution. The solvent independent interaction parameter between NPPCS and PPCS was estimated as 0.7 by extrapolation of the values of χ′23 to zero value of the fraction ratio of solvent to linear polymer, ν1/ν3 inside the network. As well as, the binary interaction parameters, χ12 of NPPCS with benzene, ethyl benzene, n‐propyl benzene and isopropyl benzene were obtained by means of Flory‐Rehner theory at temperatures between 25 and 55°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Noncovalent probes for the investigation of structure and dynamics of protein‐nucleic acid assemblies: The case of NC‐mediated dimerization of genomic RNA in HIV‐1
Authors: Turner Kevin B. , Kohlway Andrew S. , Hagan Nathan A. , Fabris Daniele 
Published: October 2008

AbstractThe nature of specific RNA‐RNA and protein‐RNA interactions involved in the process of genome dimerization and isomerization in HIV‐1, which is mediated in vitro by stemloop 1 (SL1) of the packaging signal and by the nucleocapsid (NC) domain of the viral Gag polyprotein, was investigated by using archetypical nucleic acid ligands as noncovalent probes. Small‐molecule ligands make contact with their target substrates through complex combinations of H‐bonds, salt bridges, and hydrophobic interactions. Therefore, their binding patterns assessed by electrospray ionization mass spectrometry can provide valuable insights into the factors determining specific recognition between species involved in biopolymer assemblies. In the case of SL1, dimerization and isomerization create unique structural features capable of sustaining stable interactions with classic nucleic acid ligands. The binding modes exhibited by intercalators and minor groove binders were adversely affected by the significant distortion of the duplex formed by palindrome annealing in the kissing‐loop (KL) dimer, whereas the modes observed for the corresponding extended duplex (ED) confirmed a more regular helical structure. Consistent with the ability to establish electrostatic interactions with highly negative pockets typical of helix anomalies, polycationic aminoglycosides bound to the stem‐bulge motif conserved in all SL1 conformers, to the unpaired nucleotides located at the hinge between kissing hairpins in KL, and to the exposed bases flanking the palindrome duplex in ED. The patterns afforded by intercalators and minor groove binders did not display detectable variations when the corresponding NC‐SL1 complexes were submitted to probing. In contrast, aminoglycosides displayed the ability to compete with the protein for overlapping sites, producing opposite effects on the isomerization process. Indeed, displacing NC from the stem‐bulges of the KL dimer induced inhibition of stem melting and decreased the efficiency of isomerization. Competition for the hinge region, instead, eliminated the NC stabilization of a grip motif formed by nucleobases of opposite strands, thus facilitating the strand‐exchange required for isomerization. These noncovalent probes provided further evidence that the structural context of the actual binding sites has significant influence on the chaperone activities of NC, which should be taken in account when developing potential drug candidates aimed at disrupting genome dimerization and isomerization in HIV‐1. © 2008 Wiley Periodicals, Inc. Biopolymers 91: 283–296, 2009.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Beyond eco‐efficiency: a resilience perspective
Authors: Korhonen Jouni , Seager Thomas P. 
Published: October 2008

AbstractBusiness strategy with regard to sustainability is currently dominated by an eco‐efficiency approach that seeks to simultaneously reduce costs and environmental impacts using tactics such as waste minimization or reuse, pollution prevention or technological improvement. However, in practice, eco‐efficiency optimization rarely results in improved diversity or adaptability and consequently may have perverse consequences to sustainability by eroding the resilience of production systems. This editorial article contrasts a resilience approach with an eco‐efficiency approach as they relate to strategic sustainable development. In some cases, the system attributes that are critically important to resilience – such as spare capacity, reserve resource stocks and redundancy – are in opposition to eco‐efficiency. Our most important insight is the realization that investments in what may seem counter to eco‐efficiency can nonetheless be important for sustainability. Copyright © 2008 John Wiley & Sons, Ltd and ERP Environment.
Glucose metabolism by lymphocytes, macrophages, and tumor cells from Walker 256 tumor‐bearing rats supplemented with fish oil for one generation
Authors: Aikawa Júlia , Moretto Karla D. , Denes Francilene , Yamazaki Ricardo K. , Freitas Fábio A. P. , Hirabara Sandro M. , Tchaikovski Osvaldo , Kaelher Marcos de A. , Brito Gleysson A. P. , Curi Rui , Fernandes Luiz C. 
Published: October 2008

AbstractHere we investigated the effect of lifelong supplementation of the diet with coconut fat (CO, rich in saturated fatty acids) or fish oil (FO, rich in n‐3 polyunsaturated fatty acids) on tumor growth and lactate production from glucose in Walker 256 tumor cells, peritoneal macrophages, spleen, and gut‐associated lymphocytes. Female Wistar rats were supplemented with CO or FO prior to mating and then throughout pregnancy and gestation and then the male offspring were supplemented from weaning until 90 days of age. Then they were inoculated subcutaneously with Walker 256 tumor cells. Tumor weight at 14 days in control rats (those fed standard chow) and CO supplemented was approximately 30 g. Supplementation of the diet with FO significantly reduced tumor growth by 76%. Lactate production (nmol h−1 mg−1 protein) from glucose by Walker 256 cells in the group fed regular chow (W) was 381.8 ± 14.9. Supplementation with coconut fat (WCO) caused a significant reduction in lactate production by 1.6‐fold and with fish oil (WFO) by 3.8‐fold. Spleen lymphocytes obtained from W and WCO groups had markedly increased lactate production (553 ± 70 and 635 ± 150) when compared to non‐tumor‐bearing rats (∼260 ± 30). FO supplementation reduced significantly the lactate production (297 ± 50). Gut‐associated lymphocytes obtained from W and WCO groups increased lactate production markedly (280 ± 31 and 276 ± 25) when compared to non‐tumor‐bearing rats (∼90 ± 18). FO supplementation reduced significantly the lactate production (168 ± 14). Lactate production by peritoneal macrophages was increased by tumor burden but there was no difference between the groups fed the various diets. Lifelong consumption of FO protects against tumor growth and modifies glucose metabolism in Walker tumor cells and lymphocytes but not in macrophages. Copyright © 2008 John Wiley & Sons, Ltd.
Efficient DNA Binding and Nuclear Uptake by Distamycin Derivatives Conjugated to Octa‐arginine Sequences
Authors: Vázquez Olalla , Blanco‐Canosa Juan B. , Vázquez M. Eugenio , Martínez‐Costas Jose , Castedo Luis , Mascareñas José L. 
Published: October 2008

AbstractEfficient targeting of DNA by designed molecules requires not only careful fine‐tuning of their DNA‐recognition properties, but also appropriate cell internalization of the compounds so that they can reach the cell nucleus in a short period of time. Previous observations in our group on the relatively high affinity displayed by conjugates between distamycin derivatives and bZIP basic regions for A‐rich DNA sites, led us to investigate whether the covalent attachment of a positively charged cell‐penetrating peptide to a distamycin‐like tripyrrole might yield high affinity DNA binders with improved cell internalization properties. Our work has led to the discovery of synthetic tripyrrole–octa‐arginine conjugates that are capable of targeting specific DNA sites that contain A‐rich tracts with low nanomolar affinity; they simultaneously exhibit excellent membrane and nuclear translocation properties in living HeLa cells.
A Theoretical Evaluation of the pKHBand Δ$H{{{\,\ominus}\hfill \atop {\rm HB}\hfill}}}$ Hydrogen‐Bond Scales of Nitrogen Bases
Authors: Besseau François , Graton Jérôme , Berthelot Michel 
Published: October 2008

AbstractThe experimental pKHBhydrogen‐bond (HB) basicity scale and the corresponding Δ${H{{{\ominus}\hfill \atop {\rm HB}\hfill}}}$enthalpic scale of nitrogen compounds are extended and analysed in light of simple theoretical descriptors using the B3LYP density functional method and a medium‐size basis set (6‐31+G(d,p)). The selected training set includes 59 monofunctional unhindered nitrogen bases for which homogeneous and accurate experimental pKHBand Δ${H{{{\ominus}\hfill \atop {\rm HB}\hfill}}}$data have been determined by means of the association equilibrium of the bases with a reference hydrogen‐bond acid, 4‐fluorophenol, in CCl4. The three hybridisation states encountered in the nitrogen atom, sp, sp2and sp3, are equally represented in this data set. A proper estimation of their experimental enthalpy (Δ${H{{{\ominus}\hfill \atop {\rm HB}\hfill}}}$) is directly attainable from the theoretical enthalpy of the complexation reaction with hydrogen fluoride (ΔH⊖(HF)). However, a second parameter is required to calculate with good accuracy the experimental free energy of association represented by pKHB. About 99 % of the variance of the pKHBscale is described by a bilinear equation using the minimum electrostatic potential (Vs,min) of the monomer in addition to the interaction energy (${D{{({\rm HF})\hfill \atop 0\hfill}}}$). The equations are tested for an external set of 99 additional compounds including very different nitrogen bases such asortho‐substituted pyridines, polyazines and azoles. Theoretical calculations give a reliable estimation of hydrogen‐bond basicity provided that the populations of the different isomers of the bases are taken into account by using the Boltzmann law, and that a specific halogen‐bond interaction with the solvent CCl4is considered for polybasic molecules. The pKHBscale can thus be extended to important classes of species experimentally inaccessible in CCl4, to polynitrogen compounds and to molecules of biological significance.
“Chemical Ligation”: A Versatile Method for Nucleoside Modification with Boron Clusters
Authors: Wojtczak Błazej A. , Andrysiak Agnieszka , Grüner Bohumír , Lesnikowski Zbigniew J. 
Published: October 2008

AbstractA general approach to the synthesis of nucleoside conjugates containing carborane and metallocarborane complexes, based on Huisgen 1,3‐dipolar cycloaddition (“chemical ligation”), is described. Boron‐cluster‐donors bearing terminal azide or ethynyl groups were prepared in the ring‐opening reaction of dioxane‐boron‐cluster adducts and an azide anion or suitable alkynol‐derived alcoholate nucleophile. Analogous derivatives bearing terminal sulfhydryl groups were also prepared. Nucleosides with various spacers containing terminal azide or ethynyl groups, located within nucleobases or sugar residues, were used as boron‐cluster acceptors. The proposed methodology provides a convenient way to synthesize libraries of boron‐cluster‐modified nucleosides for various applications.
Development of a Library of N‐Substituted Maleimides for the Local Functionalization of Linear Polymer Chains
Authors: Pfeifer Sebastian , Lutz Jean‐François 
Published: October 2008

AbstractA novel kinetic process was investigated for functionalizing “on‐demand” local regions of well‐defined linear polystyrene chains. This concept relies on the atom transfer radical copolymerization (ATRP) of functional N‐substituted maleimides with styrene. This copolymerization is a controlled radical process, which combines two unique kinetic features: i) all the polymers chains are growing simultaneously and ii) the cross‐propagation of the comonomers is highly‐favored as compared to homopolymerization. Thus, discrete amounts of N‐substituted maleimides (e.g., 1 equiv as compared to initiator) are consumed extremely fast in the copolymerization process and are therefore locally incorporated in narrow regions of the growing polystyrene chains. MALDI‐TOF analysis of model copolymers indicated that this kinetic concept is efficient. Although a sequence distribution is observed, well‐defined polymer chains having only one or two functional maleimide units per chain were found to be the most abundant species. Furthermore, the position of the functional groups in the polystyrene chains can be kinetically‐controlled by adding the N‐substituted maleimides at desired times during the course of the polymerization. This method is very versatile and can be applied to a wide variety of N‐substituted maleimides. Herein, a library of 20 different maleimides bearing various functional groups (e.g., aromatic moieties, fluorinated groups, hydroxy functions, protected esters, protected amines, light‐responsive moieties, fluorophores and biorelevant functions such as short poly(ethylene glycol) segments or biotin moieties) was investigated. In most cases, the functional N‐substituted maleimides could be efficiently incorporated in the polystyrene chains.
Living Radical Polymerization of Acrylates Mediated by 1,3‐Bis(2‐pyridylimino)isoindolatocobalt(II) Complexes: Monitoring the Chain Growth at the Metal
Authors: Langlotz Björn K. , Lloret Fillol Julio , Gross Jürgen H. , Wadepohl Hubert , Gade Lutz H. 
Published: October 2008

AbstractA new type of mediator for cobalt(II)‐mediated radical polymerization is reported which is based on 1,3‐bis(2‐pyridylimino)isoindolate (bpi) as ancillary ligand. The modular synthesis of the bis(pyridylimino)isoindoles (bpiH) employed in this work is based on the condensation of 2‐aminopyridines with phthalodinitriles. Reaction of the bpiH protio‐ligands with a twofold excess of cobalt(II) acetate or cobalt(II) acetylacetonate in methanol gave [Co(bpi)(OAc)], which crystallize as coordination polymers, and a series of [Co(acac)(bpi)(MeOH)], which are mononuclear octahedral complexes. Upon heating the [Co(acac)(bpi)(MeOH)] compounds to 100 °C under high vacuum, the coordinated methanol was removed to give the five‐coordinate complexes [Co(acac)(bpi)]. The polymerization of methyl acrylate at 60 °C was investigated by using one molar equivalent of the relatively short‐lived radical source 2,2′‐azobis(4‐methoxy‐2,4‐dimethylvaleronitrile) (V‐70) as initiator (monomer/catalyst/V‐70: 600:1:1). The low solubility of the acetato complexes inhibits their significant activity as mediators in this reaction, whereas the acetylacetonate complexes control the radical polymerization of methyl acrylate more effectively. The radical polymerizations of the hexacoordinate complexes did not show a linear increase in number‐average molecular weight (Mn) with conversion; however, the polydispersities were relatively low (PDI=1.12–1.40). By using the pentacoordinate complexes [Co(acac)(bpi)] as mediators, a linear increase in Mn values with conversion, which were very close to the theoretical values for living systems, and very low polydispersities (PDI<1.13) were obtained. This was also achieved in the block copolymerization of methyl acrylate and n‐butyl acrylate. The intermediates with the growing acrylate polymer radical (.PA) were identified by liquid injection field desorption/ionization mass spectrometry as following the general formula [Co(acac)(4‐methoxy‐bpi)‐(MA)n‐R] (MA: methyl acrylate; R: C(CH3)(CH2C(CH3)2OCH3)CN), a notion also confirmed by NMR end‐group analysis.
Hemoglobin on Phosphonic Acid Terminated Self‐Assembled Monolayers at a Gold Electrode: Immobilization, Direct Electrochemistry, and Electrocatalysis
Authors: Chen Yu , Jin Bo , Guo Li‐Rong , Yang Xiao‐Jing , Chen Wei , Gu Gang , Zheng Li‐Min , Xia Xing‐Hua 
Published: October 2008

AbstractPhosphonic acid (PO3H2) terminated self‐assembled monolayers (SAMs) on a gold surface were used as a functional interface to immobilize hemoglobin (Hb). In situ surface‐enhanced infrared absorption spectroscopy (SEIRAS) measurements show that Hb immobilization is a sluggish process due to formation of multilayer Hb structures on the PO3H2‐terminated SAMs, as revealed by ellipsometry, atomic force microscopy (AFM), and cyclic voltammetry (CV). In the multilayered Hb film, the innermost Hb molecules can directly exchange electrons with the electrode, whereas Hb beyond this layer communicates electronically with the electrode via protein–protein electron exchange. In addition, electrochemical measurements indicate that immobilization of Hb on the PO3H2‐terminated SAMs is not driven by the electrostatic interaction, but likely by hydrogen‐bonding interaction. The immobilized Hb molecules show excellent bioelectrocatalytic activity towards hydrogen peroxide, that is, the PO3H2‐terminated SAMs are promising for construction of third‐generation biosensors.
Photovoltaic activity of Ti/MCM‐41
Authors: Atienzar Pedro , Navarro Maite , Corma Avelino , Garcia Hermenegildo 
Published: October 2008

AbstractTi/MCM‐41 is a well‐known heterogeneous catalyst for alkene epoxidation with organic peroxides. This titanosilicate contains isolated titanium atoms forming part of a framework of mesoporous silica whose structure is formed by parallel hexagonal channels 3.2 nm in diameter. The surface area and porosity of Ti/MCM‐41 are about 880 m2 g−1 and 0.70 cm3 g−1, respectively. These values are among the highest for any material. Herein, we show that Ti/MCM‐41 exhibits photovoltaic activity. Dye‐sensitized solar cells using mesoporous Ti/MCM‐41 (2.8–5.7 % Ti content) as active layer, black dye N3 as photosensitizer and I3−/I− in methoxyacetonitrile as electrolyte exhibit a VOC, JSC and FF of 0.44 V, 0.045 mA cm−2 and 0.33, respectively. These values compare well against 0.75 V, 4.1 mA cm−2 and 0.64, respectively, measured for analogous solar cells using conventional P‐25 TiO2. However, the specific current density (JSC/Ti atom) for the Ti/MCM‐41 is very similar to that of P25 TiO2.