bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aliovalent Substitutions in Olivine Lithium Iron Phosphate and Impact on Structure and Properties
Authors: Meethong Nonglak , Kao Yu‐Hua , Speakman Scott A. , Chiang Yet‐Ming 
Published: February 2009

AbstractLithium transition metal phosphate olivines are enabling a new generation of high power, thermally stable, long‐life rechargeable lithium batteries that may prove instrumental in the worldwide effort to develop cleaner and more sustainable energy. Nanoscale (<100 nm) derivatives of the olivine family LiMPO4 (M = Fe, Mn, Co, Ni) are being adopted in applications ranging in size scale from hybrid and plug‐in hybrid electric vehicles to utilities‐scale power regulation. Following the previous paradigm set with intercalation oxides, most studies have focused on the pure ordered compounds and isovalent substitutions. In contrast, even the possibility for, and role of, aliovalent doping has been widely debated. Here, critical tests of plausible defect compensation mechanisms using compositions designed to accommodate Mg2+, Al3+, Zr4+, Nb5+ ions on the M1 and/or M2 sites of LiFePO4 with appropriate charge‐compensating defects are carried out, and conclusive crystallographic evidence for lattice doping, e.g., up to at least 12 atomic percent added Zr, is obtained. Structural and electrochemical analyses show that doping can reduce the lithium miscibility gap, increase phase transformation kinetics during cycling, and expand Li diffusion channels in the structure. Aliovalent modifications may be effective for introducing controlled atomic disorder into the ordered olivine structure to improve battery performance.
Bifurcated Mechanical Behavior of Deformed Periodic Porous Solids
Authors: Singamaneni Srikanth , Bertoldi Katia , Chang Sehoon , Jang Ji‐Hyun , Young Seth L. , Thomas Edwin L. , Boyce Mary C. , Tsukruk Vladimir V. 
Published: February 2009

AbstractThe transformation of periodic microporous structures fabricated by interference lithography followed by their freezing below glass transition is described. Periodic porous microstructures subjected to internal compressive stresses can undergo sudden structural transformation at a critical strain. The pattern transformation of collapsed pores is caused by the stresses originated during the polymerization of acrylic acid (rubbery component) inside of cylindrical pores and the subsequent solvent evaporation in the organized microporous structure. By confining the polymerization of acrylic acid to localized porous areas complex microscopic periodic structures can be obtained. The control over the mechanical instabilities in periodic porous solids at a sub‐micron scale demonstrated here suggests the potential mechanical tunability of photonic, transport, adhesive, and phononic properties of such periodic porous solids.
Polyphenylene‐Based Materials: Control of the Electronic Function by Molecular and Supramolecular Complexity
Authors: Schmaltz Bruno , Weil Tanja , Müllen Klaus 
Published: February 2009

AbstractOrganic electronics is one of the hottest and most exciting research topics today. However, its performance still lags behind that of inorganic‐based electronics. This Progress Report demonstrates that by controlling the complexity of organic molecules at the molecular and at the supramolecular level as well as by choosing suitable processing techniques, the desired function for applications in electronics can be achieved. Our main focus is on polyphenylene‐based nanomaterials, versatile organic molecules that allow access to novel intricate materials. We emphasize the molecular complexity as well as the supramolecular organization and the interfacing of novel organic materials as key guidelines.
Formation of Network and Cellular Structures by Viscoelastic Phase Separation
Authors: Tanaka Hajime 
Published: February 2009

AbstractNetwork (sponge) and cellular structures are often seen in various types of materials. Materials with such structures are generally characterized by light weight and high mechanical strength. The usefulness of such materials is highlighted, for example, by the remarkable material properties of bone tissue, which often has a highly porous structure. In artificial materials, plastic and metallic foams and breads have such structures. Here, we describe a physical principle for producing network and cellular structures using phase separation, and its potential applications to the morphological control of materials spanning from soft to hard matter.
Social facilitation of exploratory foraging behavior in capuchin monkeys (Cebus apella)
Authors: Dindo Marietta , Whiten Andrew , de Waal Frans B. M. 
Published: February 2009

AbstractMuch of the research on animal social learning focuses on complex cognitive functions such as imitation and emulation. When compelling evidence for such processes is not forthcoming, simpler processes are often assumed but rarely directly tested for. In this study we address the phenomenon of social facilitation, whereby the presence of a feeding conspecific is hypothesized to affect the motivation and behavior of the subject, elevating the likelihood of exploration and discovery in relation to the task at hand. Using a novel foraging task, sufficiently challenging that only just over half the subjects successfully gained food from it, we compared the performance of capuchin monkeys working either alone, or in a “social” condition where an actively feeding conspecific was in an adjacent chamber. Although similar numbers of subjects in these conditions were eventually successful during the 20 trials presented, the latency to successful solution of the task was over three times faster for monkeys in the social condition. The minority of monkeys that failed to learn (9/23) were then exposed to a proficient model. Only those older than 5 years provided evidence of learning from this. Accordingly, we obtained evidence for the social facilitation the study was designed to test for, and limited supplementary evidence for social learning in the older individuals who had not learned individually. These results are discussed in relation to other recent evidence for social learning in monkeys. Am. J. Primatol. 71:419–426, 2009. © 2009 Wiley‐Liss, Inc.
The influence of age, sex, population group, and dentition on the mandibular angle as measured on a South African sample
Authors: Oettlé Anna C. , Becker Piet J. , de Villiers Elzabe , Steyn Maryna 
Published: February 2009

AbstractThe mandibular angle is measured in physical anthropological assessments of human remains to possibly assist with the determination of sex and population affinity. The purpose of this investigation was to establish how the mandibular angle changes with age and loss of teeth among the sexes in South African population groups. The angles of 653 dried adult mandibles from the Pretoria Bone Collection were measured with a mandibulometer. Males and females of both South African whites and blacks were included. To compensate for imbalances in numbers among subgroups, type IV ANOVA testing was applied. No association was found between age and angle within either of the populations, within sexes, or within dentition groups. The angle was the most obtuse in individuals without molars and with an uneven distribution of molars, and most acute in the group with an even distribution of molars on both sides. Statistically significant differences (P < 0.001) were found in the angle between the two population groups and sexes in the overall sample as well as in the subgroup with absent molar teeth (P = 0.003 for sex, males more acute angle, and P = 0.001 for population group, blacks more acute angle), although a very large overlap existed. No significant differences could be demonstrated between the sexes or populations within the subgroups with molars. We concluded that the loss of molars, especially if complete or uneven, has a considerable effect on the mandibular angle. In the assessment of human remains, the mandibular angle is not very usable in determining sex. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.
Detection and Analysis of Low‐Abundance Cell‐Surface Biomarkers Using Enzymatic Amplification in Microfluidic Droplets
Authors: Joensson Haakan N. , Samuels Michael L. , Brouzes Eric R. , Medkova Martina , Uhlén Mathias , Link Darren R. , Andersson‐Svahn Helene 
Published: February 2009

AbstractProteine auf Zelloberflächen sind nützliche Biomarker für Krankheiten, allerdings konnten Hochdurchsatzmethoden bisher nur Zellen detektieren, die mindestens einige Hundert Proteine exprimieren. Enzymatische Amplifikation in Tröpfchen in einem Mikrofluidikgerät eignet sich zur Messung und Analyse von Biomarkern, die in geringer Konzentration auf einzelnen menschlichen Zellen exprimiert werden. Durch Farbstoffmarkierung der Tröpfchen können mehrere Proben gleichzeitig analysiert werden.magnified image
Total Synthesis of Cribrostatin 6
Authors: Knueppel Daniel , Martin Stephen F. 
Published: February 2009

AbstractKurz und trocken: Das antimikrobielle und antineoplastische Cribrostatin 6 wurde durch eine Totalsynthese hergestellt, deren längste lineare Sequenz lediglich vier Stufen umfasste. Im Schlüsselschritt erzeugte ein Tandemprozess aus 4π‐elektrocyclischer Ringöffnung, radikalischer Cyclisierung und homolytischer aromatischer Substitution das tricyclische Gerüst des Naturstoffs.magnified image
Titelbild: SERS‐Marker für die Anregung mit rotem Laserlicht: Glasverkapselte SAMs auf Gold/Silber‐Nanoschalen (Angew. Chem. 11/2009)
Authors: Küstner Bernd , Gellner Magdalena , Schütz Max , Schöppler Friedrich , Marx Alexander , Ströbel Philipp , Adam Patrick , Schmuck Carsten , Schlücker Sebastian 
Published: February 2009

AbstractGlasverkapselte SAMs (SAM: selbstorganisierte Monoschicht) auf durchstimmbaren Au/Ag‐Nanoschalen werden von S. Schlücker et al. in der Zuschrift auf S. 1984 ff. vorgestellt. Diese Systeme haben ein großes Potenzial als Marker für die oberflächenverstärkte Raman‐Streuung (SERS) in bioanalytischen und biomedizinischen Anwendungen, die auf einer Anregung mit rotem Laserlicht beruhen, z. B. in Assays und der Mikroskopie. Die Methode kombiniert die spektroskopischen Vorteile von SAMs mit der Stabilität einer Glashülle.magnified image
Enantioselective Catalysis Based on Cationic Oxazaborolidines
Authors: Corey E. J. 
Published: February 2009

AbstractChiral oxazaborolidines can be activated by N‐protonation using strong protic acids or by N‐coordination with AlBr3 to form very strong chiral Lewis acids. The resulting chiral boron electrophiles (see structure) are powerful chiral catalysts that effectively promote [4+2], [3+2], and [2+2]‐cycloaddition reactions with high enantioselectivity.magnified imageOver the past several decades a revolution has occurred in chemistry that has essentially been unnoticed by those outside the field, even in other sciences. In brief, this includes the following: 1) our understanding of how chemical reactions occur, 2) our ability to invent new reactions, 3) our ability to utilize reactions that construct a vast assortment of useful or complicated molecules, and 4) our ability to apply chemical principles and knowledge to understand biological and medical problems. Within synthetic chemistry, a new science has been set in place beside the old, especially in terms of the control of absolute and relative stereochemistry and the creation of new types of useful catalysts that function in ways that were hitherto unimaginable. This Review deals with one aspect of such catalysis which has emerged only in the past six years: the generation and application of super‐Lewis acidic chiral oxazaborolidinium ions for enantioselective catalysis. Progress in this area has encompassed the formation of such catalysts, the detailed pathways of the reactions that they control and accelerate, the reactions that they can promote, and the ways in which they can be applied to advantage.
Total Synthesis and Absolute Configuration of the Bisanthraquinone Antibiotic BE‐43472B
Authors: Nicolaou K. C. , Lim Yee Hwee , Becker Jochen 
Published: February 2009

AbstractAn‐T‐biotic: The first total synthesis of the T‐shaped bisanthraquinone natural product BE‐43472B was accomplished and its absolute configuration assigned. Key transformations in the pivotal cascade sequence include a Diels–Alder reaction, a hemiketal formation, and a nucleophilic aromatic ipso substitution.magnified image
Synthesis and characterization of functional copolymers of citronellol with butylmethacrylate initiated by benzoyl peroxide
Authors: Pathak Shalini , Srivastava A. K. 
Published: February 2009

AbstractBenzoyl peroxide (BPO)‐initiated free radical copolymerization of citronellol with butylmethacrylate (BMA) in xylene at 80°C ± 0.1°C under the inert atmosphere of nitrogen has been studied. The kinetics expression is Rp α [I]0.5±0.27 [citronellol]1.0±0.13 [BMA]1.0±0.18. The overall activation energy has been calculated as 65 kJ/mol. Bands at 3436 and 1732 cm−1 in the FTIR spectrum of the copolymer(s) have indicated the presence of hydroxy, ester group of citronellol and butylmethacrylate, respectively. The 1H‐NMR spectrum shows peaks at 7.0–7.7 δ due to OH proton of citronellol and at 3.2–4.0 δ due to OCH2 proton of butylmethacrylate. The molecular weight Mv and ηint of the copolymers have been measured with the help of gel permeation chromatography in tetrahydrofuran at 25°C to calculate Mark‐Houwink constants as K = 2.68 × 10−4 and α = 0.34 ± 0.40. The alternating nature of the copolymer is confirmed by reactivity ratios r1 (BMA) = 0.023 ± 0.004 and r2 (Citronellol) = 0.0025 ± 0.22. The Alfrey‐Price Q‐e parameters for citronellol have been calculated as Q2 = 0.13 and e2 = –1.28. Thermal decompositions of copolymer are evaluated with the help of thermal gravimetric analysis technique. The mechanism of copolymerization has been elucidated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
A general synthesis approach toward halloysite‐based composite nanotube
Authors: Li Cuiping , Liu Jiguang , Qu Xiaozhong , Yang Zhenzhong 
Published: February 2009

AbstractWe have demonstrated a general template synthesis halloysite‐based composite nanotube. Starting from a parent halloysite nanotube, polymer composite nanotubes were synthesized by atom transfer radical polymerization (ATRP). The shell thickness and the cavity size of the polymer composite nanotubes were tunable by altering the polymerization time. Composition of the polymer layer could be tuned by the monomers, for example, polystyrene (PS) layer was achieved by ATRP of styrene. Sulfonated PS layer (sPS) can be derived by the sulfonation of the PS layer. By specific interactions of desired materials with the sPS gel, a favorable growth of other materials, for example, metallic Ni, conductive polyaniline, inorganic titania is allowed. Besides, sPS can self‐catalyze into carbon at high temperature. Thus, the composition of the composite layers can be broadly controlled ranging within metal or metallic compounds, polymer, inorganic, carbon, and their composites. This concept is general and can be extended to other polymeric gels and grown materials, expecting a huge family of composite nanotube. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Melt rheological behavior of a triblock copolymer based on aramide end‐segments
Authors: Arun Araichimani , Gaymans Reinoud J. 
Published: February 2009

AbstractMelt rheological behavior of a ABA triblock polymer made of poly(tetramethylene oxide) (PTMO) (Mn = 2,900 g mol−1) soft segment and aramide hard segment was studied. The aramide end‐segments (A) were short and mono‐disperse in length. The mid‐segment (B) consisted of PTMO2900 extended with terephthalate units to a molecular weight of 9000 g mol−1. The molecular weight of the triblock was 9700 g mol−1. Rheological behavior of this material was studied by parallel‐plate and capillary method. The ABA triblock copolymer was compared with a B polymer (PTMO‐terephthalate) of a similar molecular weight. The low molecular weight B polymer had a Newtonian behavior. The low molecular weight triblock copolymer had at high frequencies a low complex viscosity. However, at low frequencies the triblock copolymer had a very high complex viscosity. Also the G″/G′ ratio decreased with decreasing frequency to values less then one and the G′ seemed to have at low frequencies a plateau value. The activation energy of the process increased in value with decreasing shear rate. All these results indicate that the triblock copolymer at low frequencies had a gel‐like behavior and this probably due to the clustering of the aramide segments. The aramide clusters are thought to be the (weak) network points of the gel. This network was also found to have a time dependant rheological response and thus a thixotropic behavior. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Adhesion in polypropylene/aluminum laminates made by extrusion coating
Authors: Devisme S. , Haudin J.‐M. , Agassant J.‐F. , Combarieu R. , Rauline D. , Chopinez F. 
Published: February 2009

AbstractThe purpose of this article is to study how processing parameters can promote adhesion in grafted polypropylene/aluminum laminates made by extrusion coating. The density of bonds created at the interface is quantified by X‐ray spectroscopy after dissolution of the polymer film. dynamic mechanical analysis (DMA) and tensile tests are performed to characterize the mechanical properties of polymer films. They are linked with the crystalline structure, as revealed by optical microscopy and X‐ray diffraction. A numerical model of extrusion coating is used to quantify the impact of cooling conditions on adhesion. A good correlation is found between the temperature history, the formation of bonds, and the mechanical properties of the polymer films. High temperature conditions can improve adhesion by increasing the open time for the reaction and the rate of the chemical reaction between grafted polymer chains and aluminum. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Study of a novel halogen‐free flame retardant system through TGA and structure analysis of polymers
Authors: Jang Bok Nam , Jung Inchul , Choi Jinhwan 
Published: February 2009

AbstractButadiene‐rubber toughened styrene polymers, such as acrylonitrile‐butadiene‐styrene (ABS) copolymer and high impact polystyrene (HIPS), are noncharring polymers. They are generally blended with polycarbonate (PC) or polyphenyleneether (PPE), which are char forming polymers, to improve char forming ability for styrenic blends containing conventional phosphate flame retardants. To achieve cost effective flame retardant system, PET was selected as a potential char‐source for ABS blends through the thermogravimetric analysis (TGA) and chemical structure analysis of various polymers. PET may contribute to the enhancement of flame retardancy of ABS/PET blends, especially in the presence of small amounts of phenol novolac (PN). The effective flame retardancy of this system is believed to be accomplished through the enhancement of interchain reactions by PN. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Solvent‐crazed PET fibers imparting antibacterial activity by release of Zn2+
Authors: Weichold Oliver , Goel Pooja , Lehmann Karl‐Heinz , Möller Martin 
Published: February 2009

AbstractPoly(ethylene terephthalate) fibers containing zinc chloride in the fiber bulk were prepared by solvent crazing. Fibers containing 6 g/Kg and 13 g/Kg Zn2+ were investigated. SEM‐EDX analyses and the formation of the pink bis(1,5‐dithiocarbazonato‐N,S) complex inside the fibers confirm the presence of zinc. UV‐Vis spectroscopy indicates a slow release of zinc ions into the aqueous media and, thus, the fibers serve as a release system to inhibit the growth of Escherichia coli during the first exposure. Thermal annealing of the freshly prepared fibers above Tg was shown to modify the release profile so that bacterial growth was also inhibited during repetitive and prolonged exposures. The washing fastness is fair and after 10 washing cycles, ∼ 30% of the original zinc content still remains in the fiber. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Substrate thickness: An effective control parameter for polymer thin film buckling on PDMS substrates
Authors: Hyun Dong Choon , Jeong Unyong 
Published: February 2009

AbstractBuckling patterns of polymer thin films on plasma‐treated poly(dimethylsiloxane) (PDMS) substrates were sensitively affected by the thickness of the substrate in addition to the substrate modulus. On highly crosslinked PDMS substrates, the buckling wavelength of polymer thin films sharply increased as the thickness of the substrates were raised and approached a plateau value when the substrate was 2.5 mm‐thick. On weakly crosslinked PDMS substrates, the wavelength still increased even when the substrate was thicker than 20 mm. The high dependence of the buckling on the substrate thickness has not been reported before and is unexpected from the current predictions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis and swelling behavior of a new superabsorbent hydrogel network based on polyacrylamide grafted onto salep
Authors: Pourjavadi Ali , Bardajee Ghasem Rezanejade , Soleyman Rouhollah 
Published: February 2009

AbstractSynthesis and swelling behavior of a new superabsorbent hydrogel based on natural salep grafted with polyacrylamide is described. The new superabsorbent hydrogel biopolymer was synthesized via radical crosslinking and graft copolymerization of acrylamide monomer onto salep backbones. Regarding to the water absorption of hydrogel, the best synthesis condition is reported. FTIR spectroscopy and thermogravimetric analysis were used to confirm the structure of the final product and a mechanism for superabsorbent hydrogel formation was also suggested. After preparing the desired hydrogels based on optimum condition, several factors affecting the swelling behavior of hydrogel including pH of medium, sensitivity to the salt solution, and mixture of solvents were studied. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Characterization of metallocene ethylene‐1‐octene copolymers with high comonomer content cross‐linked by dicumyl peroxide or β‐radiation
Authors: Nicolás J. , Ressia J. A. , Vallés E. M. , Merino J. C. , Pastor J. M. 
Published: February 2009

AbstractTwo metallocene ethylene‐1‐octene copolymers differing in comonomer content were cross‐linked either by dicumyl peroxide (DCP) or β‐radiation with doses ranging from 0.5 to 4% DCP and 25 to 200 kGy, respectively. The effect of cross‐linking on the crystalline morphology was analyzed by differential scanning calorimetry (DSC). Slight alterations in the crystalline structure were found, which were more severe in the case of peroxi modification. Through infrared spectroscopy (FTIR analysis), oxidation during the cross‐linking process was detected on the DCP cross‐linked samples, while β‐irradiated samples do not exhibited significant degrees of oxidation. The state of cure was studied following the changes in the rheological properties in small‐amplitude oscillatory shear mode, and the evolution of the molecular weight and molecular weight distribution through size exclusion chromatography. Irradiation doses below 200 kGy increased the molecular weight and branching of both copolymers but were not sufficient to reach gelation. All the peroxide modified samples resulted in a post‐gel condition. Optimal mechanical properties were obtained with concentration of about 1% DCP. At higher doses, scission reactions diminish the tensile strength and the elongation at break. When polymers with equivalent amounts of gel fraction obtained by the two modification procedures studied in this work are compared, higher tensile strength and elongation at break are obtained with irradiation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009