bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Spring‐Like Behavior of Chiral Block Copolymer with Helical Nanostructure Driven by Crystallization
Authors: Chiang Yeo‐Wan , Ho Rong‐Ming , Thomas Edwin L. , Burger Christian , Hsiao Benjamin S. 
Published: December 2008

AbstractThe crystallization of helical nanostructure resulting from the self‐assembly of a chiral diblock copolymer, poly(styrene)‐b‐poly(L‐lactide) (PS‐PLLA), is studied. Various crystalline PS‐PLLA nanostructures are obtained by controlling the crystallization temperature of PLLA (Tc,PLLA), at which crystalline helices and crystalline cylinders occur while Tc,PLLA < Tg,PS (the glass transition temperature of PS) and Tc,PLLA ≥ Tg,PS, respectively. As evidenced by selected‐area electron diffraction and two‐dimensional X‐ray diffraction results, the PLLA crystallites under confinement reveal a unique anisotropic character regardless of the crystallization temperature. On the basis of observed uniaxial scattering results the PLLA crystallites grown within the microdomains are identified as crystals with preferential growth directions either along the [100] or along the [110]‐axes of the PLLA crystalline unit cell, at which the molecular chains and the growth direction are normal and parallel to the central axes of helices, respectively. The formation of this exclusive crystalline growth is attributed to the spatial confinement effect for crystallization. While Tc,PLLA < Tg,PS, owing to the directed crystallization by helical confinement, the preferential crystalline growth leads to the crystallization following a helical track with growth direction parallel to the central axes of helices through a twisting mechanism. Consequently, winding crystals with specific crystallographic orientation within the helical microdomains can be found. By contrast, while Tc,PLLA ≥ Tg,PS, the preferential growth may modulate the curvature of microdomains by shifting the molecular chains to access the fast path for crystalline growth due to the increase in chain mobility. As a result, a spring‐like behavior of the helical nanostructure can be driven by crystallization so as to dictate the transformation of helices, resulting in crystalline cylinders that might be applicable to the design of switchable large‐strain actuators.
An N‐Linked Bidentate Phosphoramidite Ligand (N‐Me‐BIPAM) for Rhodium‐Catalyzed Asymmetric Addition of Arylboronic Acids to N‐Sulfonylarylaldimines
Authors: Kurihara Kazunori , Yamamoto Yasunori , Miyaura Norio 
Published: December 2008

AbstractA chiral N‐linked C2‐symmetric bidentate phosphoramidite (N‐Me‐BIPAM) was newly developed for the rhodium‐catalyzed enantioselective addition of arylboronic acids to N‐sulfonylimines. This ligand achieved high enantioselectivities in a range of 84–99% ee in additions of arylboronic acids to N‐tosyl‐ and N‐nosylarylaldimines.
Development of an anatomically based whole‐body musculoskeletal model of the Japanese macaque (Macaca fuscata)
Authors: Ogihara Naomichi , Makishima Haruyuki , Aoi Shinya , Sugimoto Yasuhiro , Tsuchiya Kazuo , Nakatsukasa Masato 
Published: December 2008

AbstractWe constructed a three‐dimensional whole‐body musculoskeletal model of the Japanese macaque (Macaca fuscata) based on computed tomography and dissection of a cadaver. The skeleton was modeled as a chain of 20 bone segments connected by joints. Joint centers and rotational axes were estimated by joint morphology based on joint surface approximation using a quadric function. The path of each muscle was defined by a line segment connecting origin to insertion through an intermediary point if necessary. Mass and fascicle length of each were systematically recorded to calculate physiological cross‐sectional area to estimate the capacity of each muscle to generate force. Using this anatomically accurate model, muscle moment arms and force vectors generated by individual limb muscles at the foot and hand were calculated to computationally predict muscle functions. Furthermore, three‐dimensional whole‐body musculoskeletal kinematics of the Japanese macaque was reconstructed from ordinary video sequences based on this model and a model‐based matching technique. The results showed that the proposed model can successfully reconstruct and visualize anatomically reasonable, natural musculoskeletal motion of the Japanese macaque during quadrupedal/bipedal locomotion, demonstrating the validity and efficacy of the constructed musculoskeletal model. The present biologically relevant model may serve as a useful tool for comprehensive understanding of the design principles of the musculoskeletal system and the control mechanisms for locomotion in the Japanese macaque and other primates. Am J Phys Anthropol, 2009. © 2008 Wiley‐Liss, Inc.
Markers of physiological stress in juvenile bonobos (Pan paniscus): Are enamel hypoplasia, skeletal development and tooth size interrelated?
Authors: Lukacs John R. 
Published: December 2008

AbstractA reduction in enamel thickness due to disrupted amelogenesis is referred to as enamel hypoplasia (EH). Linear EH in permanent teeth is a widely accepted marker of systemic physiological stress. An enigmatic, nonlinear form of EH commonly manifest in great ape and human deciduous canines (dc) is known as localized hypoplasia of primary canines (LHPC). The etiology of LHPC and what it signifies—localized traumatic or systemic physiological stress—remains unclear. This report presents frequency data on LHPC, hypostotic cranial traits, and tooth size in a sample of juvenile bonobos, then tests hypotheses of intertrait association that improve knowledge of the etiology and meaning of LHPC. The fenestration hypothesis is tested using hypostotic cranial traits as a proxy for membrane bone ossification, and the relationship between tooth size, LHPC, and hypostosis is investigated. Macroscopic observations of EH, hypostotic traits, and measurements of buccolingual tooth size were conducted according to established standards. LHPC was found in 51.2% of bonobos (n = 86) and in 26% of dc teeth (n = 269). Hypostotic traits were observed in 55.2% of bonobos (n = 96). A test of the association between LHPC and hypostosis yielded nonsignificant results (χ2 = 2.935; P = 0.0867). Primary canines were larger in specimens with LHPC than in unaffected specimens (paired samples t test; udc, P = 0.011; ldc, P = 0.018), a result consistent with the fenestration hypothesis of LHPC pathogenesis. Hypostosis was not associated with differences in tooth size (P > 0.05). LHPC may be an indirect indicator of physiological stress, resulting from large, buccally displaced primary canines. Am J Phys Anthropol, 2009. © 2008 Wiley‐Liss, Inc.
Food mechanical properties in three sympatric species of Hapalemur in Ranomafana National Park, Madagascar
Authors: Yamashita Nayuta , Vinyard Christopher J. , Tan Chia L. 
Published: December 2008

AbstractWe investigated mechanical dietary properties of sympatric bamboo lemurs, Hapalemur g. griseus, H. aureus, and H. (Prolemur) simus, in Ranomafana National Park, Madagascar. Each lemur species relies on bamboo, though previous behavioral observations found that they specialize on different parts of a common resource (Tan: Int J Primatol 20 1999 547–566; Tan: PhD dissertation 2000 State University of New York, Stony Brook). On the basis of these earlier behavioral ecology studies, we hypothesized that specialization on bamboo is related to differences in mechanical properties of specific parts. We quantified mechanical properties of individual plant parts from the diets of the bamboo lemur species using a portable tester. The diets of the Hapalemur spp. exhibited high levels of mechanical heterogeneity. The lemurs, however, could be segregated based on the most challenging (i.e., mechanically demanding) foods. Giant bamboo culm pith was the toughest and stiffest food eaten, and its sole lemur consumer, H. simus, had the most challenging diet. However, the mechanical dietary properties of H. simus and H. aureus overlapped considerably. In the cases where lemur species converged on the same bamboo part, the size of the part eaten increased with body size. Plant parts that were harvested orally but not necessarily masticated were the most demanding, indicating that food preparation may place significant loads on the masticatory apparatus. Finally, we describe how mechanical properties can influence feeding behavior. The elaborate procurement processes of H. simus feeding on culm pith and H. griseus and H. aureus feeding on young leaf bases are related to the toughnesses of protective coverings and the lemurs' exploitation of mechanical vulnerabilities in these plants. Am J Phys Anthropol, 2009. © 2008 Wiley‐Liss, Inc.
Ex uno plures (“aus Einem Vieles”): Konzepte zur Erweiterung des Polyolefin‐Repertoires durch reversiblen Gruppentransfer
Authors: Sita Lawrence R. 
Published: December 2008

AbstractDas Gebiet der Polyolefinewird als ausgereift betrachtet und vermittelt den Eindruck, man könne jede Polymerstruktur durch iterative Derivatisierung des Koordinationskatalysators erhalten. Dieses Konzept ist jedoch selbstbeschränkend. Bimolekulare Gruppentransferreaktionen bieten dagegen eine einfache Möglichkeit, ausgehend von einem Katalysator durch Variieren der Reaktionsparameter vielfältige Polyolefinmaterialien zugänglich zu machen.magnified imageDas Gebiet der Polyolefine, die mit homogenen, löslichen Katalysatoren durch Koordinationspolymerisation von Ethen und 1‐Alkenen hergestellt werden, wird heute als ausgereift betrachtet. Mit diesem Status ist der allgemeine Eindruck verbunden, dass inzwischen jede gewünschte stereochemische Mikrostruktur oder Copolymerzusammensetzung durch iterative Derivatisierung eines ursprünglichen Moleküldesigns routinemäßig und mit hoher Zuverlässigkeit erhältlich ist. Dieses “Ein‐Katalysator‐ein‐Material”‐Konzept ist aber in sich selbstbeschränkend, weil die Zahl der Molekülstrukturen, die synthetisiert und verwendet werden können, begrenzt ist. Vor kurzem eingeführte Reaktionen mit nicht‐terminierenden, reversiblen Gruppentransferprozessen, die mit der Kettenfortpflanzung konkurrieren, bilden indes die Basis für neuartige “Ein‐Katalysator‐viele‐Materialien”‐Konzepte, die das Potenzial haben, die Bandbreite von Polyolefinmaterialien für das 21. Jahrhundert enorm zu vergrößern.
“Wenn Schweine fliegen könnten”: Zum Prinzip der mikroskopischen Reversibilität
Authors: Blackmond Donna G. 
Published: December 2008

AbstractWie durch einen dunklen Spiegel: Mehrere kürzlich beschriebene autokatalytische Reaktionsmodelle, die den Ursprung der Homochiralität erklären sollen, umfassen Regenerierungsreaktionen in einem abgeschlossenen System, um die Umwandlung des einen Produktenantiomers in das andere einzubeziehen. Es wird aufgezeigt, dass diese Modelle das Prinzip der mikroskopischen Reversibilität verletzen, das für Reaktionsnetzwerke auch weit entfernt vom Gleichgewicht Gültigkeit haben muss.magnified image
Synthese, Struktur und Komplexierungseigenschaften von partiell und vollständig reduziertenmeso‐Octamethylporphyrinogenen (Calix[4]pyrrolen)
Authors: Blangy Valeria , Heiss Christoph , Khlebnikov Vsevolod , Letondor Christophe , Stoeckli‐Evans Helen , Neier Reinhard 
Published: December 2008

AbstractAus alt mach neu: Calixpyrrole sind bekannte Anionenbinder und können nur schwer in Übergangsmetallkomplexe überführt werden. Die vollständige Hydrierung eines Calixpyrrols ergab nun einen Liganden, der leicht klassische Kupfer‐, Nickel‐ und Palladiumkomplexe bilden kann. Die Metallkomplexe enthalten ein Netzwerk von vier ausgerichteten Wasserstoffbrücken, die spezifisch Gegenionen binden (siehe Bild; blau N, weiß H, grün Cl, rot Cu, Ni oder Pd).magnified image
Bifunctional Dendrimers: From Robust Synthesis and Accelerated One‐Pot Postfunctionalization Strategy to Potential Applications
Authors: Antoni Per , Hed Yvonne , Nordberg Axel , Nyström Daniel , von Holst Hans , Hult Anders , Malkoch Michael 
Published: December 2008

AbstractZwei Sätze von difunktionellen AB2C‐Dendrimeren mit internen Acetylen/Azid‐ und externen Hydroxygruppen wurden synthetisiert. Eine erfolgreiche Funktionalisierung in situ belegte das chemoselektive Verhalten der Dendrimere, die außerdem in dendritische Nanopartikel umgewandelt oder als dendritische Vernetzer beim Aufbau von Hydrogelen eingesetzt werden konnten.magnified image
Synthetische Lectine
Authors: Kubik Stefan 
Published: December 2008

AbstractKonkurrenz zur Natur: Bei der Kohlenhydraterkennung kann die supramolekulare Chemie in Wasser nun in Bezug auf Effizienz und Selektivität mit natürlichen Systemen konkurrieren. Ein synthetischer Kohlenhydratrezeptor bindet N‐Acetyl‐D‐glucosaminderivate (siehe Bild; grau C, weiß H, blau N, rot O) ähnlich stark wie das Lectin Weizenkeimagglutinin und übertrifft sogar dessen Selektivität. Damit kann dieser Rezeptor möglicherweise in Zelladhäsionsprozesse eingreifen.magnified image
Bifunctional Dendrimers: From Robust Synthesis and Accelerated One‐Pot Postfunctionalization Strategy to Potential Applications
Authors: Antoni Per , Hed Yvonne , Nordberg Axel , Nyström Daniel , von Holst Hans , Hult Anders , Malkoch Michael 
Published: December 2008

AbstractA fourth wheel: Two sets of bifunctional AB2C dendrimers having internal acetylene/azides and external hydroxy groups were constructed utilizing benign synthetic protocols. An in situ postfunctionalization strategy was successfully carried out to illustrate the chemoselective nature of these dendrimers. The dendrimers were also transformed into dendritic nanoparticles or utilized as dendritic crosslinkers for the fabrication hydrogels.magnified image
Ultrasonic and mechanical measurements for the detection of crosslink density of SBR and NBR based on various curing systems
Authors: Lawandy S. N. , Halim S. F. , Afifi H. A. 
Published: December 2008

AbstractThe stress–strain measurements of styrene‐butadiene rubber (SBR) samples based on various curing systems were used to access the crosslink density of various rubber mixes. Same materials were subjected to various uniaxial compression strains. The thicknesses before compression and after recovery were recorded. After recovery, pulse echo method was used to measure the ultrasonic velocity for the dilatational wave and that of shear wave at a frequency of 2 MHz and at room temperature. Both of the ultrasonic velocities were used to determine the elastic moduli of the samples. The relation between the elastic moduli and the corresponding recovery values were used to determine the crosslink density of samples. The crosslink density values obtained from the two techniques were compared. Butadiene‐acrylonitrile (NBR) rubber mix was used to show that the ultrasonic technique is applicable for other rubber compounds. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Bonding properties between nitrile–butadiene rubber and aluminum alloy treated by anodizing methods
Authors: Zhang Xiao‐Feng , Fan Li , Zhao Xu‐Hui , Zhang Li‐Qun , Liu Li , Zuo Yu 
Published: December 2008

AbstractIn this work, the bonding properties between the LD7 aluminum alloy anodized by sulfuric acid or phosphoric acid and nitrile–butadiene rubber (NBR) were investigated. The bonding properties between the anodized aluminum alloys and NBR were compared with those between aluminum alloys treated by burnishing or sandblasting and NBR. The results revealed that, in comparison with sulfuric acid anodized samples, samples anodized in phosphoric acid solutions showed higher 90° peel strength. Under the same conditions, an increase in the anodic film thickness in the studied range may improve the adhesion property between rubber and an aluminum alloy. In comparison with aluminum alloys treated by burnishing or sandblasting, the surface of the anodized aluminum alloy showed homogeneously dispersed pores, which resulted in better and homogeneous bonding properties. A vacuum‐drying process on the anodized aluminum alloys after they were coated with adhesives facilitated penetration of the adhesive molecules into the pores on the oxide layer, which considerably improved the bonding properties. In addition, rubber macromolecules could also penetrate the pores in the aluminum oxide layer, leading to a strong physical anchor–hold interaction after a long time of soaking and diffusion. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Photochemistry of low‐density polyethylene–montmorillonite composites
Authors: Ghafor Wael A. , Halley Peter J. , Hill David J. T. , Martin Darren J. , Rasoul Firas , Whittaker Andrew K. 
Published: December 2008

AbstractPhoto‐oxidation at the exposed surfaces of low‐density polyethylene/montmorillonite composites was analyzed with attenuated total reflection/Fourier transform infrared spectroscopy. It was found that the clay particles were dispersed but not exfoliated in the polymer matrix. The extent of oxidative degradation of the low‐density polyethylene matrix was slightly greater when montmorillonite was present and was greatest for the blend of low‐density polyethylene and organically modified montmorillonite. The Fourier transform infrared measurements demonstrated that the rate of photo‐oxidation in the bulk was lower than that observed at the surface, but the oxidation chemistry was similar at the surface and in the bulk. The distribution of the photo‐oxidation products was somewhat modified in the presence of montmorillonite and organically modified montmorillonite in comparison with pure low‐density polyethylene, with the yield of acidic products higher and the yield of double bonds lower. These observations were attributed to a slightly higher yield of radicals and some modification of the quantum yield for the processes leading to the formation of double bonds when the clay filler was present. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis and characterization of graft copolymers of syndiotactic polystyrene with polybutadiene and 4‐methylstyrene
Authors: Srinate Nathinee , Thongyai Supakanok , Praserthdam Piyasan 
Published: December 2008

AbstractThe basic method for synthesizing syndiotactic polystyrene‐g‐polybutadiene graft copolymers was investigated. First, the syndiotactic polystyrene copolymer, poly(styrene‐co‐4‐methylstyrene), was prepared by the copolymerization of styrene and 4‐methylstyrene monomer with a trichloro(pentamethyl cyclopentadienyl) titanium(IV)/modified methylaluminoxane system as a metallocene catalyst at 50°C. Then, the polymerization proceeded in an argon atmosphere at the ambient pressure, and after purification by extraction, the copolymer structure was confirmed with 1H‐NMR. Lastly, the copolymer was grafted with polybutadiene (a ready‐made commercialized unsaturated elastomer) by anionic grafting reactions with a metallation reagent. In this step, poly(styrene‐co‐4‐methylstyrene) was deprotonated at the methyl group of 4‐methylstyrene by butyl lithium and further reacted with polybutadiene to graft polybutadiene onto the deprotonated methyl of the poly(styrene‐co‐4‐methylstyrene) backbone. After purification of the graft copolymer by Soxhlet extraction, the grafting reaction copolymer structure was confirmed with 1H‐NMR. These graft copolymers showed high melting temperatures (240–250°C) and were different from normal anionic styrene–butadiene copolymers because of the presence of crystalline syndiotactic polystyrene segments. Usually, highly syndiotactic polystyrene has a glass‐transition temperature of 100°C and behaves like a glassy polymer (possessing brittle mechanical properties) at room temperature. Thus, the graft copolymer can be used as a compatibilizer in syndiotactic polystyrene blends to modify the mechanical properties to compensate for the glassy properties of pure syndiotactic polystyrene at room temperature. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Spoliation of fluoroperm rigid gas permeable contact lens by sodium chloride: A positron annihilation study
Authors: Deepa Urs M. V. , Ranganathaiah C. 
Published: December 2008

AbstractThe interaction of sodium chloride with Fluoroperm92 contact lens has been investigated using several techniques. Results indicate adhesion of sodium chloride to the methacrylate and fluorine sites of the lens resulting to zones of excess salt concentration. Na+ and Cl− ions appear to be pushed toward the polymer by water molecules, which favor the bulk water structures. Further inference is that lens with more free water leads to localized spots of drying resulting to sites for lipid deposition and lens spoilage. The changes in refractive index of the lens due to salt adhesion correlate well with the free volume. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Mechanical properties of poly(ε‐caprolactone) and poly(lactic acid) blends
Authors: Simões C. L. , Viana J. C. , Cunha A. M. 
Published: December 2008

AbstractThe aim of this work was to better understand the performance of binary blends of biodegradable aliphatic polyesters to overcome some limitations of the pure polymers (e.g., brittleness, low stiffness, and low toughness). Binary blends of poly(ε‐caprolactone) (PCL) and poly(lactic acid) (PLA) were prepared by melt blending (in a twin‐screw extruder) followed by injection molding. The compositions ranged from pure biodegradable polymers to 25 wt % increments. Morphological characterization was performed with scanning electron microscopy and differential scanning calorimetry. The initial modulus, stress and strain at yield, strain at break, and impact toughness of the biodegradable polymer blends were investigated. The properties were described by models assuming different interfacial behaviors (e.g., good adhesion and no adhesion between the dissimilar materials). The results indicated that PCL behaved as a polymeric plasticizer to PLA and improved the flexibility and ductility of the blends, giving the blends higher impact toughness. The strain at break was effectively improved by the addition of PCL to PLA, and this was followed by a decrease in the stress at break. The two biodegradable polymers were proved to be immiscible but nevertheless showed some degree of adhesion between the two phases. This was also quantified by the mechanical property prediction models, which, in conjunction with material property characterization, allowed unambiguous detection of the interfacial behavior of the polymer blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis of a photoimmobilizable histidine polymer for surface modification
Authors: Sakuragi Makoto , Tsuzuki Saki , Hasuda Hirokazu , Wada Akira , Matoba Kenji , Kubo Izumi , Ito Yoshihiro 
Published: December 2008

AbstractA novel photoreactive polymer with histidine polar groups was synthesized through the copolymerization of two types of methacrylic acid, one carrying histidine groups and the other carrying azidoaniline groups. The polymer was photoimmobilized on polyester disks for surface modification. The effect of the surface modification on the hydrophilic and biofouling properties was investigated. Static contact angle measurements showed that the polymeric surface was modified to be comparatively hydrophilic in the polymer‐immobilized region. Micropattern immobilization was carried out with a photolithographic method. Atomic force microscopy measurements showed that the polymer was formed on the disks in response to ultraviolet irradiation. Protein adsorption was reduced on the polymer‐immobilized regions, and in those regions, spreading and adhesion of mammalian cells were reduced in comparison with that in nonimmobilized regions. In conclusion, a novel histidine‐containing polymer was photoreactively immobilized on a conventional polymer surface, and it had reduced interaction with proteins and cells. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009