bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reversible Assembly and Disassembly of Gold Nanoparticles Directed by a Zwitterionic Polymer
Authors: Ding Ya , Xia Xing‐Hua , Zhai He‐Sheng 
Published: January 2007

AbstractHerein, we have successfully introduced the stimuli‐response concept into the controllable synthesis of gold nanoparticles (AuNPs) with designed properties. We used a pH‐responsive zwitterionic polymer that acted as a template and a stabilizer. Gold colloids prepared in situ from the polymer solution have a narrow size distribution of about 5 nm. The assembly and disassembly of AuNPs can be finely tuned by modulating the net charges of the zwitterionic polymer so that they are either positive or negative as a function of the solution pH. Different aggregates and colors appear on altering the solution pH. In acidic solutions, gold colloids form large symmetrical aggregates, while the AuNPs disperse in solutions with a pH≈9.6. However, as the solution pH increases (>9.6), needle‐like aggregates with a small interparticle distances are formed. On the basis of TEM, SEM, 1H NMR and UV/Vis measurements, we attribute pH‐triggered aggregation and color changes of the gold colloids to the ionization process and conformational change of the polymer. The ionization process governs the choice of ligand anchored on the surface of AuNPs, and the conformational change of the polymer modulates the interspaces between AuNPs. The present approach, which is based on a rational design of the physicochemical properties of the template used in the synthesis process, provides a powerful means to control the properties of the nanomaterial. Furthermore, the colorimetric readout can be visualized and applied to future studies on nanoscale switches and sensors.
Effect of Protonation and Interaction with Anions on a Lead(II) Complex with a Lateral Macrobicycle Containing a Phenol Schiff‐Base Spacer
Authors: Esteban‐Gómez David , Platas‐Iglesias Carlos , Avecilla Fernando , de Blas Andrés , Rodríguez‐Blas Teresa 
Published: January 2007

AbstractThe macrobicycle receptor L4, derived from 1,10‐diaza‐15‐crown‐5 incorporating a phenol Schiff‐base spacer, forms stable complexes with lead(II). In [Pb(L4)(ClO4)](ClO4)·CH3CN (1), the lead(II) ion is asymmetrically placed at the one end of the macrobicyclic cavity, because of the intramolecular hydrogen bonding interaction that occurs between an imine nitrogen atom and the phenol group. This asymmetric position of the metal ion inside the macrobicyclic cavity induces chirality in this system. Variable temperature 1H NMR spectroscopic experiments indicate that the asymmetric coordination of the metal ion inside the macrocyclic cavity is maintained in acetonitrile solution, but a translocation of the PbII ion from one end of the macrobicyclic cavity to the second one occurs. This dynamic behaviour, which corresponds to the interconversion between the two possible enantiomeric forms of the complex, is fast on the NMR timescale at 320 K but slow at low temperatures, and we have estimated an activation barrier of ΔG‡ = 68 ± 2 kJ mol–1. We have also studied the effect of the protonation on 1 by NMR and UV/Vis spectroscopy in CH3CN solutions at room temperature, finding that diprotonation causes demetallation of the complex without receptor destruction, recovering L4 in its protonated form. On the other hand, the interaction of compound 1 with anions such as NO3– and SCN– has been evaluated by using spectrophotometric titrations in acetonitrile solution, finding log K values of 5.83(1) for NO3– and 6.27(2) forSCN–. The [Pb(L4)]2+, [Pb(L4)(NO3)]+, [Pb(L4)(NCS)]+ and [Pb(L4)(SCN)]+ systems were characterized by means of density functional theory calculations (DFT) performed by using the B3LYP model, and the coordination geometry as well as the role of the PbII lone pair has been investigated and discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Polymer‐Supported Dioxido‐MoVI Complexes as Truly Functional Molybdenum Oxotransferase Model Systems
Authors: Heinze Katja , Fischer Andreas 
Published: January 2007

AbstractA truly functional model system for molybdenum oxotransferases provides evidence for all biologically realistic intermediates, namely mononuclear MoVI, MoV and MoIV species. Dinucleation to EPR‐silent [MoV2O3] species prevailing in homogeneous solution is suppressed by immobilising the active species to a polymeric support by two‐point attachment.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Polymorphic occurrence and crystallization rates of tristearin/tripalmitin mixtures under non‐isothermal conditions
Authors: Himawan Chrismono , MacNaughtan William , Farhat Imad A. , Stapley Andrew G. F. 
Published: January 2007

AbstractThe effect of composition and cooling rate on polymorphic occurrence and crystallization rates in binary mixtures of tripalmitoylglycerol (PPP) and tristearoylglycerol (SSS) has been studied using differential scanning calorimetry (DSC), light microscopy and X‐ray diffraction under constant cooling rates. In general, β and β' polymorphs were observed at cooling rates of 0.5 K/min and less, and the α form at higher cooling rates. Double peaks were observed in the DSC exotherms of mixtures containing more than 30% SSS. The X‐ray data showed that, when cooling at 0.5 K/min, the double peaks correspond to the crystallization of the α and β' forms. However, when cooling at 1 K/min and higher, the double peaks appear to arise from the crystallization of two α phases – one PPP rich and the other SSS rich. Light microscopy experiments also show two distinct morphologies, which corroborates this view. The apparent SSS‐rich phase crystallizes as irregular spherulites whereas the apparent PPP‐rich phase forms a fine crystal mass. Analyses of thermograms relating to the α form show that the amount of supercooling at the onset of crystallization is virtually independent of composition. However, peak width information shows that, once started, pure‐component samples crystallize faster than mixtures.
Evaluation of partially hydrogenated methyl esters of soybean oil as biodiesel
Authors: Moser Bryan R. , Haas Michael J. , Winkler Jill K. , Jackson Michael A. , Erhan Sevim Z. , List Gary R. 
Published: January 2007

AbstractBiodiesel, an alternative fuel derived from vegetable oils or animal fats, continues to undergo rapid worldwide growth. Specifications mandating biodiesel quality, most notably in Europe (EN 14214) and the USA (ASTM D6751), have emerged that limit feedstock choice in the production of biodiesel fuel. For instance, EN 14214 contains a specification for iodine value (IV; 120 g I2/100 g maximum) that eliminates soybean oil as a potential feedstock, as it generally has an IV >120. Therefore, partially hydrogenated soybean oil methyl esters (PHSME; IV = 116) were evaluated as biodiesel by measuring a number of fuel properties, such as oxidative stability, low‐temperature performance, lubricity, kinematic viscosity, and specific gravity. Compared to soybean oil methyl esters (SME), PHSME were found to have superior oxidative stability, similar specific gravity, but inferior low‐temperature performance, kinematic viscosity, and lubricity. The kinematic viscosity and lubricity of PHSME, however, were within the prescribed US and European limits. There is no universal value for low‐temperature performance in biodiesel specifications, but PHSME have superior cold flow behavior when compared to other alternative feedstock fuels, such as palm oil, tallow and grease methyl esters. The production of PHSME from refined soybean oil would increase biodiesel production costs by US$ 0.04/L (US$ 0.15/gal) in comparison to SME. In summary, PHSME are within both the European and American standards for all properties measured in this study and deserve consideration as a potential biodiesel fuel.
ω‐Alkyne‐Mono‐ and Diphosphonates – Synthesis and Sonogashira Cross‐Coupling Reaction with Aryl Halides
Authors: Delain‐Bioton Lise , Villemin Didier , Jaffrès Paul‐Alain 
Published: January 2007

AbstractA convergent approach to functionalise aromatic compounds with a linker terminated by a phosphonate group is reported. The starting point of this strategy is the synthesis of five new ω‐alkyne‐phosphonates. The linker between the phosphonate group and the alkyne part is either an alkyl or an ether chain. This strategy is based on the use of the phosphonate group as the anchoring point for the attachment of organic compounds onto alumina and the alkyne group, which is used to functionalise aryl halide compounds by a Sonogashira cross‐coupling. The use of 1,10‐phenanthroline as substrate illustrates the application of this strategy to an aromatic ligand. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Effects of rock fragments incorporated in the soil matrix on concentrated flow hydraulics and erosion
Authors: Rieke‐Zapp D. , Poesen J. , Nearing M. A. 
Published: January 2007

AbstractRock fragments can act as a controlling factor for erosional rates and patterns in the landscape. Thus, the objective of this study is to better understand the role that rock fragments incorporated into the soil matrix play in concentrated flow hydraulics and erosion. Laboratory flume experiments were conducted with soil material that was mixed with rock fragments. Rock fragment content ranged from 0 to 40 per cent by volume. Other treatments were slope (7 and 14%) and flow discharge (5·7 and 11·4 l min−1). An increase in rock fragment content resulted in lower sediment yield, and broader width of flow. Rock fragment cover at the soil surface, i.e. surface armour, increased with time in experiments with rock fragments. Flow energy was largely dissipated by rock fragment cover. For more turbulent flow conditions, when roughness elements were submerged in the flow, hydraulic roughness was similar for different rock fragment contents. In experiments with few or no rock fragments a narrow rill incised. Flow energy was dissipated by headcuts. Total sediment yield was much larger than for experiments with rock fragments in the soil. Adding just a small number of rock fragments in the soil matrix resulted in a significant reduction of sediment yield. Copyright © 2007 John Wiley & Sons, Ltd.
Quantitative biorelevant profiling of material microstructure within 3D porous scaffolds via multiphoton fluorescence microscopy
Authors: Liu Er , Treiser Matthew D. , Johnson Patrick A. , Patel Parth , Rege Aarti , Kohn Joachim , Moghe Prabhas V. 
Published: January 2007

AbstractThis study presents a novel approach, based on fluorescence multiphoton microscopy (MPM), to image and quantitatively characterize the microstructure and cell–substrate interactions within microporous scaffold substrates fabricated from synthetic biodegradable polymers. Using fluorescently dyed scaffolds fabricated from poly(DTE carbonate)/poly(DTO carbonate) blends of varying porosity and complementary green fluorescent protein‐engineered fibroblasts, we reconstructed the three‐dimensional distribution of the microporous and macroporous regions in 3D scaffolds, as well as cellular morphological patterns. The porosity, pore size and distribution, strut size, pore interconnectivity, and orientation of both macroscale and microscale pores of 3D scaffolds were effectively quantified and validated using complementary imaging techniques. Compared to other scaffold characterizing techniques such as confocal imaging and scanning electron microscopy (SEM), MPM enables the acquisition of images from scaffold thicknesses greater than a hundred microns with high signal‐to‐noise ratio, reduced bulk photobleaching, and the elimination of the need for deconvolution. In our study, the morphology and cytoskeletal organization of cells within the scaffold interior could be tracked with high resolution within the limits of penetration of MPM. Thus, MPM affords a promising integrated platform for imaging cell–material interactions within the interior of polymeric biomaterials. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007
Enhanced retention of polymer physical characteristics and mechanical strength of 70:30 poly(L‐lactide‐co‐D,L‐lactide) after ethylene oxide sterilization
Authors: McManus Anastasia J. , Moser Rodney C. , Dabkowski Rhiannon B. , Thomas Kevin A. 
Published: January 2007

AbstractThis study examined the effect of ethylene oxide (EtO) and electron beam (e‐beam) irradiation on the properties of 70:30 poly(L‐lactide‐co‐D,L‐lactide). The effects of sterilization upon the polymer physical characteristics and strength retention of the material were examined, both initially and after being subjected to real time ageing. Commercially available 70:30 poly(L‐lactide‐co‐D,L‐lactide) material was fabricated into rectangular, cylindrical, screw, and sheet designs, and tested in compression, shear, or tension. Sterilization of 70:30 poly(L‐lactide‐co‐D,L‐lactide) by ethylene oxide had a nearly negligible effect on the physical properties of the polymer, regardless of specimen size or manufacturing technique. The molecular weight and inherent viscosity of the specimens decreased by ∼3% after sterilization by EtO. However, sterilization of 70:30 poly(L‐lactide‐co‐D,L‐lactide) by e‐beam irradiation resulted in immediate changes to some of the physical properties of the polymer. Specimens sterilized by e‐beam irradiation displayed an immediate decrease in inherent viscosity of ∼67% as compared to the respective nonsterile samples. The immediate decrease in inherent viscosity and molecular weight with e‐beam irradiation required ∼39 weeks of real time ageing of the EtO sterilized parts. At all time points investigated in the present study, the strength retention of the EtO sterilized devices equaled or exceeded that of the e‐beam irradiated samples. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007
New insights on the bridge carbon–carbon bond in propellanes: A theoretical study based on the analysis of the electron localization function
Authors: Polo Victor , Andres Juan , Silvi Bernard 
Published: January 2007

AbstractThe nature of the bonding between bridgehead carbon atoms (Ca, Ca′) as well as the ring strain in a family of 10 propellanes formed by three‐, four‐, or five‐member rings: [1.1.1] (I), [2.1.1] (II), [3.1.1] (III), [2.2.1] (IV), [3.2.1] (V), [2.2.2] (VI), [3.3.1] (VII), [3.2.2] (VIII), [3.3.2] (IX), and [3.3.3] (X) are studied by means of the electron localization function (ELF) at the DFT level (B3LYP/cc‐pVTZ). The ELF analysis of smaller propellanes (I, II, and III) reveals the coexistence of two resonance forms: one with a nonbonding electron pair partially delocalized between Ca and Ca′ atoms outside the cage (ionic) and the other with a bridge bond between the same atoms (covalent). The weights of each form are calculated according to the ELF‐basin populations, yielding 94, 88, and 53% for the ionic structure of I, II, and III, respectively, while larger propellanes (IV–X) present only the covalent form. The question of the s‐character of the bridge bond is addressed by dissecting the bridge‐bond ELF basin into the molecular orbital contributions. Finally, σ‐aromaticity associated to surface electron delocalization has been analyzed by means of nucleus‐independent chemical shift (NICS) calculations. The results point out that the stability of the fused ring structure of propellanes I, II, and III, can be assigned to the remarkable σ‐aromaticity of the involved three‐member rings. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Reduced chondrogenic potential of adipose tissue derived stromal cells correlates with an altered TGFβ receptor and BMP profile and is overcome by BMP‐6
Authors: Hennig Thea , Lorenz Helga , Thiel Angela , Goetzke Katrin , Dickhut Andrea , Geiger Florian , Richter Wiltrud 
Published: January 2007

AbstractRecent interest has focused on mesenchymal stem cells (MSC) for tissue engineering and regenerative therapy of cartilage defects. MSC originating from adipose tissue (ATSC) are attractive as they are easily available and abundant. They have similar properties like bone marrow derived MSC (BMSC), except for a reduced chondrogenic potential under standard culture conditions driven by TGFβ. Aim of this study was to search for possible differences explaining the reduced differentiation capacity of ATSC and to eliminate it by adaptation of induction protocols. Expanded MSC were analyzed for their growth factor and related receptor repertoire and ATSC spheroid cultures were supplemented with BMP‐2,‐4,‐6,‐7, TGFβ, FGFa, FGFb, IGF‐1, and PTHrP alone or in combination with TGFβ. In contrast to BMSC, ATSC showed reduced expression of BMP‐2, ‐4, and ‐6 mRNA and did not express TGFβ‐receptor‐I protein. Consistent with this, increased concentrations of TGFβ did not improve chondrogenesis of ATSC. BMP6 treatment induced TGFβ‐receptor‐I expression and combined application of TGFβ and BMP‐6 eliminated the reduced chondrogenic potential of ATSC inducing a gene expression profile similar to differentiated BMSC. Like in BMSC, chondrogenesis of ATSC was associated with hypertrophy according to premature collagen Type X expression, upregulation of alkaline‐phosphatase activity and in vivo calcification of spheroids after ectopic transplantation in SCID mice. In conclusion, a distinct BMP and TGFβ‐receptor repertoire may explain the reduced chondrogenic capacity of ATSC in vitro, which could be compensated by exogenous application of lacking factors. Further studies should now be directed to induce chondrogenesis in the absence of hypertrophy. J. Cell. Physiol. 211: 682–691, 2007. © 2007 Wiley‐Liss, Inc.
Bifurcated hydrogen‐bonding effect on the shielding and coupling constants in trifluoroacetyl pyrroles as studied by 1H, 13C and 15N NMR spectroscopy and DFT calculations
Authors: Afonin Andrei V. , Ushakov Igor A. , Mikhaleva Al'bina I. , Trofimov Boris A. 
Published: January 2007

AbstractAccording to the 1H, 13C and 15N NMR spectroscopic data and DFT calculations, bifurcated NH···N and NH···O intramolecular hydrogen bond is shown to be present in 2‐trifluoroacetyl‐5‐(2′‐pyridyl)‐pyrrole. This bifurcated hydrogen bond causes an increase in the absolute size of the 1J(N,H) coupling constant by about 6 Hz, and the deshielding of the bridge proton by 2 ppm. DFT calculations show that the influence of the NH···N and NH···O intramolecular hydrogen bonds on the 1J(N,H) coupling and proton shielding is almost additive, although the components of the bifurcated hydrogen bond slightly weaken each other. In 2‐trifluoroacetyl‐5‐(2′‐pyridyl)‐pyrrole, the coupling constants involving the fluorine and the NH covalent bond nuclei depend dramatically on the spatial position of the pyridine ring. The pyridine ring rotation operates as a quantum switch controlling the spin information transfer between the 19F and 15N nuclei, as well as the proton. Copyright © 2007 John Wiley & Sons, Ltd.
Complete 1H and 13C NMR assignments of sesquiterpene glucosides from Ixeris sonchifolia
Authors: Na ZeyEi , Cho Jeong‐Yong , Lee Hyoung Jae , Chung Jin Ho , Park Ki Deok , Lee Young Ju , Shin Soo Cheol , Rim Yo Sup , Park Keun‐Hyung , Moon Jae‐Hak 
Published: January 2007

AbstractFour sesquiterpene glucosides were isolated from Ixeris sonchifolia Hance. The structure of a new compound (1) was assigned as 9β‐monohydroxy‐2,12‐dioxo‐guaia‐3,11(13)‐dien‐1α,5α,6β,7α,9β,10αH‐12,6‐olide‐9‐O‐β‐D‐ glucopyranoside (ixerinoside). In addition, unambiguous and complete assignments of 1H NMR chemical shifts for crepidiaside A (2), ixerin Z (3), and 11,13α‐dihydroixerin Z (4) are presented. The assignments were achieved by two‐dimensional NMR (gCOSY, gHSQC, gHMBC, NOESY) and one‐dimensional nuclear Overhauser effect (NOE) experiments. Copyright © 2007 John Wiley & Sons, Ltd.
Quantitative characterization of hemodynamic properties and vasculature dysfunction of high‐grade gliomas
Authors: Nagesh Vijaya , Chenevert Thomas L. , Tsien Christina I. , Ross Brian D. , Lawrence Theodore S. , Junck Larry , Cao Yue 
Published: January 2007

AbstractAberrations in tumor and peritumoral vasculature may not be distinguishable by cerebral blood flow (CBF) or cerebral blood volume (CBV) alone. The relationships between CBF and CBV were examined to estimate vasculature‐specific hemodynamic characteristics. Twenty glioma patients were studied with dynamic susceptibility T2*‐weighted MRI [(dynamic contrast‐enhanced magnetic resonance imaging (DSC‐MRI)] before and during week 1 and 3 of radiotherapy (RT). CBF and CBV were calculated from DSC‐MRI, and relationships between the two were evaluated: the physiological measure of mean transit time (MTT) = CBV/CBF; empirical fitting using the power law CBV = constant × (CBF)β. Three different tissue types were assessed: the Gd‐enhancing tumor volume (GEV); non‐enhanced abnormal tissue located beyond GEV but within the abnormal hyperintense region on FLAIR images (NEV); normal tissue in the hemisphere contralateral to the tumor (CNT). The effects of tissue types, CBV magnitudes (low, medium and high), before and during RT, on MTT and β were analyzed by analysis of variance (ANOVA). The MTT and β for the three tissue types were significantly different (p < 0.009). MTT increased from CNT (1.60 s) to NEV (1.93 s) to GEV (2.28 s) (p < 0.0005). β was significantly greater in GEV (1.079) and NEV (1.070) than in CNT (1.025). β increased with increasing CBV magnitude while MTT was independent of CBV magnitude. There was a significant decrease in MTT of NEV and GEV during week 3 of RT compared with pre‐RT values for all CBV magnitudes. There was a significant increase in β during RT in the tumor and peritumor. Progressive abnormalities in vasculature and hemodynamic characteristics of the vascular bed were delineated, with significant disorder in the tumor but mild abnormality in peritumoral tissue. Copyright © 2007 John Wiley & Sons, Ltd.
Computation of accurate nodal derivatives of finite element solutions: the finite node displacement method
Authors: Ilinca F. , Pelletier D. 
Published: January 2007

AbstractThis paper presents a new method for extracting high‐accuracy nodal derivatives from finite element solutions. The approach involves imposing a finite displacement to individual mesh nodes, and solving a very small problem on the patch of surrounding elements, whose only unknown is the value of the solution at the displaced node. A finite difference between the original and perturbed values provides the directional derivative. Verification is shown for a one‐dimensional diffusion problem with exact nodal solution and for two‐dimensional scalar advective–diffusive problems. For internal nodes the method yields accuracy slightly superior to that of the superconvergent patch recovery (SPR) technique of Zienkiewicz and Zhu (ZZ). We also present a variant of the method to treat boundary nodes. In this case, the local discretization is enriched by inserting an additional mesh point very close to the boundary node of interest. We show that the new method gives normal derivatives at boundary points that are consistent with the so‐called ‘auxiliary fluxes’. The resulting nodal derivatives are much more accurate than those obtained by the ZZ SPR technique. Copyright © 2007 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.
British attitudes on nuclear weapons
Authors: Byrom Andy 
Published: January 2007

Abstract
In an increasingly unstable world post‐911, the political landscape seems to be continually shifting, with many of the old certainties around combatants and how to wage war being subject to revision—not least the role of nuclear weapons in a post‐Cold War age. But have our attitudes towards the development and use of nuclear weapons fundamentally changed over the past 50 years? Andy Byrom, Associate Director at Ipsos MORI, examines data from the previous half‐century which lead to some surprising conclusions.

Copyright © 2007 John Wiley & Sons, Ltd.