bluuebunny/crossref_metadata_2025_split huggingface dataset:
Micelle formation and sol–gel transition behavior of comb‐like amphiphilic poly((PLGA‐b‐PEG)MA) copolymers
Authors: Park Chung Won , Lee Su Jeong , Kim Dukjoon , Lee Doo Sung , Kim Sung Chul 
Published: February 2008

AbstractComb‐like amphiphilic poly(poly((lactic acid‐co‐glycolic acid)‐block‐poly(ethylene glycol)) methacrylate (poly((PLGA‐b‐PEG)MA)) copolymers were synthesized by radical polymerization. (PLGA‐b‐PEG)MA macromonomer was prepared by ring‐opening bulk polymerization of DL‐lactide and glycolide using purified poly(ethylene glycol) monomethacrylate (PEGMA) as an initiator. (PLGA‐b‐PEG)MA macromonomer was copolymerized with PEGMA and/or acrylic acid (AA) by radical polymerization to produce comb‐like amphiphilic block copolymers. The molecular weight and chemical structure were investigated by GPC and 1H NMR. Poly((PLGA‐b‐PEG)MA) copolymer aqueous solutions showed gel–sol transition behavior with increasing temperature, and gel‐to‐sol transition temperature decreased as the compositions of the hydrophilic PEGMA and AA increased. The gel‐to‐sol transition temperature of the terpolymers of the poly((PLGA‐b‐PEG)MA‐co‐PEGMA‐co‐AA) also decreased when the pH was increased. The effective micelle diameter obtained from dynamic light scattering increased with increasing temperature and with increasing pH. The critical micelle concentration increased as the composition of the hydrophilic monomer component, PEGMA and AA, were increased. The spherical shape of the hyperbranched polymers in aqueous environment was observed by atomic force microscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1954–1963, 2008
Ozonolysis efficiency of PS‐b‐PI block copolymers for forming nanoporous polystyrene
Authors: Chen Suz‐Yen , Huang Yuming , Tsiang Raymond Chien‐Chao 
Published: February 2008

AbstractA PS‐b‐PI diblock copolymer has been synthesized and blended with a homopolystyrene of a variable molecular weight at a variable weight ratio, resulting in different volume fractions of PS to PI and various morphologies. After being cast as a film, the double bonds in the PI microdomains were cleaved via ozonolysis resulting in the formation of a nanoporous PS. The ease of ozonolysis depended strongly upon the morphology of the PI microdomains. The degree of ozonization after 24‐h reaction was about 90% for lamellar microdomains, about 80% for bicontinuous microdomains, about 70% for cylindrical microdomains, and about 50% for spherical microdomains. These variations were attributed to the decrease in the contact area of PI microdomains with ozone and the total volume of PI microdomains accessible to ozone. All PS‐b‐PI/homopolystyrene samples have turned into nanoporous materials after the removal of PI nanodomains. SEM, AFM, and TEM images indicated that the resulting PS had a pore size of 20–30 nm, and thus was potentially useful for photonic crystals or fuel cell applications. © 2008 Wiley Periodicals, Inc. JPolym Sci Part A: Polym Chem 46: 1964–1973, 2008
Free‐radical‐promoted cationic photopolymerization under visible light in aerated media: New and highly efficient silane‐containing initiating systems
Authors: Lalevée Jacques , El‐Roz Mohamad , Allonas Xavier , Pierre Fouassier Jean 
Published: February 2008

AbstractNew systems for the visible‐light‐induced polymerization of cationic resins working through a free‐radical‐promoted process are presented. They are based on a photoinitiator (camphorquinone, isopropylthioxanthone, Eosin), a silane, and a diphenyl iodonium salt, the new compound being the silane. The overall efficiency is strongly affected by the silane structure. The rates of polymerization and final percent conversion are noticeably higher than those obtained in the presence of already studied reference systems. Moreover, contrary to previously investigated free‐radical‐promoted cationic polymerizations, oxygen does not inhibit the process and an unusual enhancement of the polymerization kinetics is found in aerated conditions: such an observation seems to have never been reported so far. The excited state processes and the role of oxygen as revealed by laser flash photolysis are discussed. The particular behavior of the silyl radicals is outlined. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2008–2014, 2008
Self‐assembly of supramolecular polymers into tunable helical structures
Authors: Kim Ho‐Joong , Lim Yong‐Beom , Lee Myongsoo 
Published: February 2008

AbstractThere is growing interest in the design of synthetic molecules that are able to self‐assemble into a polymeric chain with compact helical conformations, which is analogous to the folded state of natural proteins. Herein, we highlight supramolecular approach to the formation of helical architectures and their conformational changes driven by external stimuli. Helical organization in synthetic self‐assembling systems can be achieved by the various types of noncovalent interactions, which include hydrogen bonding, solvophobic effects, and metal‐ligand interactions. Since the external environment can have a large influence on the strength and configuration of noncovalent interactions between the individual components, stimulus‐induced alterations in the intramolecular noncovalent interactions can result in dynamic conformational change of the supramolecular helical structure thus, driving significant changes in the properties of the materials. Therefore, these supramolecular helices hold great promise as stimuli‐responsive materials. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1925–1935, 2008
Convenient synthesis of poly(γ‐benzyl‐L‐glutamate) from activated urethane derivatives of γ‐benzyl‐L‐glutamate
Authors: Kamei Yasutaka , Nagai Atsushi , Sudo Atsushi , Nishida Haruo , Kikukawa Kiyoshi , Endo Takeshi 
Published: February 2008

AbstractA series of activated urethane‐type derivatives of γ‐benzyl‐L‐glutamate were synthesized, and their potential as monomers for polypeptide synthesis was investigated. The derivatives of the focus of this work were a series of N‐aryloxycarbonyl‐γ‐benzyl‐L‐glutamate 1, of which aryl groups were phenyl, 4‐chlorophenyl, and 4‐nitrophenyl. These urethanes 1 were reactive in polar solvents such as dimethylsulfoxide, N,N‐dimethylformamide (DMF), and N,N‐dimethylacetamide (DMAc), and were efficiently converted into poly(γ‐benzyl‐L‐glutamate) (poly(BLG)) under mild conditions; at 60 °C without addition of any catalyst. Among the three urethanes, that having 4‐nitrophenoxycarbonyl group 1c was the most reactive to give poly(BLG) efficiently, as was expected from the highly electron deficient nature of the nitrophenoxycarbonyl group. On the other hand, the urethane 1a having phenoxycarbonyl group was also efficiently converted into poly(BLG), in spite of the intrinsically less electrophilicity of the phenoxycarbonyl group. In addition, the successful formation of poly(BLG) by the reaction of 1a favored its diluted concentration (0.1 M) much more than 2.0 M, the optimum initial concentration for 1c. 1H NMR spectroscopic analyses of the reactions in situ revealed that the predominant pathway from 1 to poly(BLG) involved the intramolecular cyclization of 1 into the corresponding N‐carboxyanhydride, with release of phenol and its successive ring‐opening polymerization with release of carbon dioxide. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2649–2657, 2008
Stability of Ionic Liquids under the Influence of Glow Discharge Plasmas
Authors: Xie Yong‐Bing , Liu Chang‐Jun 
Published: February 2008

AbstractThe combination of cold plasma and ionic liquids is very promising for many applications in chemical syntheses and nano material fabrication. Using NMR and FTIR analyses, we confirmed for the first time that imidazolium ionic liquids remain stable under the influence of a glow discharge plasma. Reduction of HAuCl4 and PdCl2 using an argon glow discharge was performed at room temperature for the formation of metal nano particles in 1‐butyl‐3‐methylimidazolium tetrafluoroborate. TEM and XRD showed that the Au particles were hexagonal with average sizes of 32.7 nm, while the Pd particles were spherical with average size of 5.0 nm.magnified image
Design of a bivalent peptide with two independent elements of secondary structure able to fold autonomously
Authors: Pantoja‐Uceda David , Pastor M. Teresa , Salgado Jesús , Pineda‐Lucena Antonio , Pérez‐Payá Enrique 
Published: February 2008

AbstractThis article describes a strategy to develop, starting from a de novo design, bivalent peptides containing two different (α‐helix and β‐hairpin) and independent secondary‐structure elements. The design was based on the use of conformationally restricted peptide libraries. Structural characterization by NMR revealed that the peptides were stable and did not show any long‐range NOE interactions between the N‐terminal β‐hairpin and the C‐terminal α‐helix. These results suggest that the two elements of secondary structure are stable and well folded. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.
Aggregation of Aβ(1–42) in the presence of short peptides: conformational studies
Authors: Laczkó Ilona , Vass Elemér , Soós Katalin , Fülöp Livia , Zarándi Márta , Penke Botond 
Published: February 2008

AbstractCD and infrared spectroscopic studies were performed on (i) the inhibitory effects of equimolar quantities of LPFFD‐OH and LPYFD‐NH2 on the time‐dependent aggregation of amyloid β‐protein (Aβ) (1–42) and (ii) the β‐sheet‐breaker effects of two‐fold molar excess of the pentapeptides on aggregated Aβ(1–42) aged 1 week. The data obtained from the time‐dependent studies demonstrated that LPFFD‐OH did not significantly influence, whereas LPYFD‐NH2 exerted some inhibitory effect on the aggregation of Aβ(1–42). When added to a solution of Aβ(1–42) aged 1 week, LPFFD‐OH accelerated, while LPYFD‐NH2 delayed, but did not prevent further fibrillogenesis. The difference in the effects of these two pentapeptides on the aggregational profile of Aβ(1–42) is probably due to the difference in their conformational preferences: LPFFD‐OH adopts a β‐turn and extended structures, while LPYFD‐NH2 adopts a prevailing β‐turn conformation. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.
Internal migration and ethnic groups: evidence for Britain from the 2001 Census
Authors: Finney Nissa , Simpson Ludi 
Published: February 2008

AbstractRelatively little is known about the internal migration behaviour of different ethnic groups. This paper reviews existing evidence, and analyses 2001 Census data for Britain to provide an overview of patterns in the level of migration and the distance migrated, according to the characteristics of migrants and for diverse ethnic groups. Those who migrate in each ethnic group have similar characteristics, leading to the assertion that differences in levels of migration result mainly from differing socio‐economic and age compositions of ethnic groups. This is confirmed through regression analysis. Differences in distance migrated, however, are not explained by the composition of ethnic groups, but may be explained by their primarily urban current areas of residence. Exceptions to the general patterns are highlighted as avenues for further investigation. Copyright © 2008 John Wiley & Sons, Ltd.
Mass spectrometry in the characterization of ambers. I. Studies of amber samples of different origin and ages by laser desorption ionization, atmospheric pressure chemical ionization and atmospheric pressure photoionization mass spectrometry
Authors: Tonidandel Loris , Ragazzi Eugenio , Roghi Guido , Traldi Pietro 
Published: February 2008

AbstractAmber is a fossil resin constituted of organic polymers derived through complex maturation processes of the original plant resin. A classification of eight samples of amber of different geological age (Miocene to Triassic) and geographical origin is here proposed using direct mass spectrometric techniques, i.e. laser desorption ionization (LDI), atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI), in order to obtain a fingerprint related to the amber origin. Differences and similarities were detected among the spectra with the four methods, showing quite complex spectra, full of ionic species in the mass range investigated (up to m/z 2000). The evaluation required statistical analysis involving multivariate techniques. Cluster analysis or principal component analysis (PCA) generally did not show a clear clustering with respect to the age of samples, except for the APPI method, which allowed a satisfying clustering. Using the total ion current (TIC) obtained by the different analytical approaches on equal quantities of the different amber samples and plotted against the age, the only significant correlation appeared to be that involving APPI. To validate the method, four amber samples from Cretaceous of Spain were analyzed. Also in this case a significant correlation with age was found only with APPI data. PCA obtained with TIC values from all the MS methods showed a fair grouping of samples, according to their age. Three main clusters could be detected, belonging to younger, intermediate and older fossil resins, respectively. This MS analysis on crude amber, either solid or extract, followed by appropriate multivariate statistical evaluation, can provide useful information on amber age. The best results are those obtained by APPI, indicating that the quantity of amber soluble components that can be photoionized decreases with increasing age, in agreement with the formation of highly stable, insoluble polymers. Copyright © 2008 John Wiley & Sons, Ltd.
Simulation of X‐ray diffractograms obtained by grazing incidence X‐ray diffraction of implanted stainless steel
Authors: Dudognon J. , Vayer M. , Pineau A. , Erre R. 
Published: February 2008

AbstractA method to interpret grazing incidence X‐ray diffractograms observed for expanded phases occurring after Mo implantation in an austenitic steel was extended to Ag and N ion implantation in austenitic or ferritic stainless steels.Theoretical X‐ray diffractograms were built taking into account the information depth profile, the implanted element concentration depth profile and a linear relationship between implanted element concentration and lattice parameter through an expansion coefficient (k). Experimental X‐ray diffractograms were adjusted to the theoretical ones. The adjustment led to the determination of k and/or ion‐implanted concentration profile as a function of depth.For Ag implantation in AISI 316 LVM and 430 stainless steels, the concentration depth profile was predicted using SRIM‐2003 computer program and confirmed by experimental measurement using RBS. The built austenite or ferrite X‐ray diffraction peaks were in good accordance with the experimental ones. k was shown to be independent on the incident angle and on the fluence but dependant on the type of initial lattice.For nitrided austenitic stainless steels, the k value was determined with N‐implanted AISI 316 LVM steel. The element concentration depth profiles and k value were determined for low‐energy high‐flux nitrogen implantation‐diffusion of AISI 304 steels. The predicted profiles were confirmed by NRA measurements. Copyright © 2008 John Wiley & Sons, Ltd.
Composite of Ti6Al4V and SiC fibres: evolution of fibre–matrix interface during heat treatments
Authors: Donnini Riccardo , Kaciulis Saulius , Mezzi Alessio , Montanari Roberto , Testani Claudio 
Published: February 2008

AbstractThe changes in fibre–matrix interface during the heat treatment of Ti6Al4V matrix reinforced with carbon‐coated SiC fibres, have been studied using XPS, AES and SEM/EDS (energy dispersion spectroscopy) techniques. The samples were characterized before and after heating at different temperatures up to 600 °C with long exposure times up to 1000 h. Particular attention was paid to the C/matrix interface, where high temperature treatment could lead to the formation of titanium carbide. Due to the experimental difficulties to separate the contributions of TiC and SiC, the interaction between titanium and carbon was simulated by heating Ti6Al4V and pure Ti foils covered with graphite. Obtained interfaces have been analysed by XPS depth profiling. Experimental results were supported by theoretical calculations of carbon diffusion. Copyright © 2008 John Wiley & Sons, Ltd.
Analysis of Cu segregation to oxide–metal interface of Ni‐base alloy by HX‐PES
Authors: Doi Takashi , Kitamura Kazuyuki , Nishiyama Yoshitaka , Otsuka Nobuo , Kudo Takeo , Sato Masugu , Ikenaga Eiji , Kobayashi Keisuke , Hashimoto Tamotsu 
Published: February 2008

AbstractHard X‐ray Photoelectron spectroscopy (HX‐PES) has been realized using high‐brilliance synchrotron radiation. High‐energy photon excitation enables us to probe photoelectrons with larger escape depth compared to conventional PES. This allows us to conduct a study of embedded interface of materials as the oxide–metal interface without destruction. We apply HX‐PES to investigate for Cu segregation in the oxide–metal interface during metal dusting corrosion. The effective concentration of Cu in the segregation layer was estimated a few 10 times higher than the bulk concentration. These results on the interface layer can explain the variation in the corrosion resistance. Copyright © 2008 John Wiley & Sons, Ltd.
Anchoring of sulfur‐containing alkylphosphonic and semifluorinated alkylphosphonic molecules on a polycrystalline aluminum substrate
Authors: Fonder G. , Delhalle J. , Essahli M. , Ameduri B. , Mekhalif Z. 
Published: February 2008

AbstractSelf‐assembly on a polycrystalline aluminum substrate of two sulfur‐containing alkylphosphonic acids, CH3(CH2)11S (CH2)2PO(OH)2, and CF3(CF2)7(CH2)2S(CH2)2PO(OH)2, has been compared with CH3(CH2)15PO(OH)2. The reaction of the phosphonic head groups with the hydroxyls at the alumina surface to form phosphonates was studied with X‐ray photoelectron spectroscopy (XPS) and polarization modulation infrared reflection‐absorption spectroscopy (PM‐IRRAS). Barrier effects of the resulting layers was assessed by electrochemical polarization curves. With the conditions used in the present work for the self‐assembly reaction, it appears that the sulfur‐containing molecules do not perform as well as CH3(CH2)15PO(OH)2 in terms of film quality. Questions are raised about the possibility that the sulfur‐containing molecules could undergo cleavage during surface modification. Copyright © 2008 John Wiley & Sons, Ltd.
ARXPS and high energy XPS characterisation of titanium surfaces for medical implants
Authors: Sunding Martin F. , Jensen Ingvild T. , Stenstad Per M. , Diplas Spyros 
Published: February 2008

AbstractSurfaces of pure Ti before and after treatment with phosphoric acid and aminopropyl trimethoxysilane (APTMS) were analysed with XPS at normal emission and in angle‐resolved mode. In addition, three different excitation energies with increasing analysis depth were used, namely, Mg Kα, Al Kα and Ag Lα. The use of monochromatic Ag Lα enabled the acquisition of both 1s, 2p and KLL peaks for Si and P. We used these peaks to identify the chemical states of Si and P via the use of the 2p‐KLL and 1s‐KLL Auger parameters (AP). The Si and P AP values were in the region of silanes/silicones and phosphates respectively. The various spectral features confirmed the expected chemical states of the surfaces, except for the oxidation level of Ti in the titanium phosphate layer: results suggest the presence of a Ti(IV) phosphate instead of a Ti(III) phosphate reported in literature. Copyright © 2008 John Wiley & Sons, Ltd.
Uncertainty and the market valuation of R&D within a real options logic
Authors: Oriani Raffaele , Sobrero Maurizio 
Published: February 2008

AbstractThe aim of this study is to provide new theoretical insights and empirical evidence on the effect of market and technological uncertainty on the market valuation of a firm's R&D capital. A set of hypotheses is developed adopting a real options logic and tested on a panel dataset of 290 manufacturing firms traded in the UK. Consistently with our theoretical model, we show that market and technological uncertainty have distinct effects on the valuation of R&D investments. The results have several important implications for resource allocation to R&D under uncertainty, which we discuss in the concluding section. Copyright © 2008 John Wiley & Sons, Ltd.
Trust‐opportunism paradox, relationalism, and performance in interfirm relationships: evidence from the retail industry
Authors: Lado Augustine A. , Dant Rajiv R. , Tekleab Amanuel G. 
Published: February 2008

AbstractBuilding on recent theoretical work documenting that interorganizational relationships (IORs) are ‘multifaceted and multiplex’ we investigate, from the agent's perspective, the joint effects of trust and opportunism in fostering (or inhibiting) relationalism, which, in turn, is predicted to influence performance within interfirm exchange relationships. Based on longitudinal survey data on 409 catalog intermediaries affiliated with a large retail firm, we found strong support for most of the hypothesized relationships. Implications for future research are offered. Copyright © 2008 John Wiley & Sons, Ltd.
Isolation in design reuse
Authors: Gamble M. T. , Gamble R. F. 
Published: February 2008

AbstractSoftware composition relies heavily on the ability to reuse software within the context of a complex target system. When components are built or sourced from third party suppliers, some form of design material is reused that embodies a variety of artifacts that differ in both granularity and abstraction. The more concrete the design material, particularly if it is in the form of a fully realized reusable component, the more likely it has evolved from a distinct supplier development path that will cause interoperability problems in the composite design. Unfortunately, recognizing integration problems occurs late in a typical design process, often disrupting the process of choosing alternative components. We express the design reuse process using a concept map whose nodes represent sources of design material. Guidance for consolidating and analyzing reuse alternatives is shown via design moves between concepts culminating in the choice of components for the target system. We use isolation as the determinant for interoperability assessment. Leveraging a biological analogy, we define distinct integration levels where isolating mechanisms occur to add assessment clarity. This is illustrated with an example showing conflicts between reusable components from different suppliers. Copyright © 2008 John Wiley & Sons, Ltd.