bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional Graphenic Materials Via a Johnson−Claisen Rearrangement
Authors: Sydlik Stefanie A. , Swager Timothy M. 
Published: November 2012

AbstractCurrent research in materials has devoted much attention to graphene, with a considerable amount of the chemical manipulation going through the oxidized state of the material, known as graphene oxide (GO). In this report, the hydroxyl functionalities in GO, the vast majority that must be allylic alcohols, are subjected to Johnson−Claisen rearrangement conditions. In these conditions, a [3, 3] sigmatropic rearrangement after reaction with triethyl orthoacetate gives rise to an ester functional group, attached to the graphitic framework via a robust C−C bond. This variation of the Claisen rearrangement offers an unprecedented versatility of further functionalizations, while maintaining the desirable properties of unfunctionalized graphene. The resultant functional groups were found to withstand reductive treatments for the deoxygenation of graphene sheets and a resumption of electronic conductivity is observed. The ester groups are easily saponified to carboxylic acids in situ with basic conditions, to give water‐soluble graphene. The ester functionality can be further reacted as is, or the carboxylic acid can easily be converted to the more reactive acid chloride. Subsequent amide formation yields up to 1 amide in 15 graphene carbons and increases intergallery spacing up to 12.8 Å, suggesting utility of this material in capacitors and in gas storage. Other functionalization schemes, which include the installation of terminal alkynes and dipolar cycloadditions, allow for the synthesis of a highly positively charged, water‐soluble graphene. The highly negatively and positively charged graphenes (zeta potentials of −75 mV and +56 mV, respectively), are successfully used to build layer‐by‐layer (LBL) constructs.
Nanostructured Porous Silicon‐Solid Lipid Nanocomposite: Towards Enhanced Cytocompatibility and Stability, Reduced Cellular Association, and Prolonged Drug Release
Authors: Liu Dongfei , Mäkilä Ermei , Zhang Hongbo , Herranz Barbara , Kaasalainen Martti , Kinnari Päivi , Salonen Jarno , Hirvonen Jouni , Santos Hélder A. 
Published: November 2012

AbstractA major bottleneck in nanometer‐scale drug delivery systems is the fabrication of nanocarriers with excellent stability under physiological conditions that can both efficiently encapsulate therapeutic agents and controllably release their payloads. Herein, the formation of a novel nanocomposite based on the encapsulation of thermally hydrocarbonized porous silicon (THCPSi) nanoparticles with solid lipid nanoparticles (SLNs) on a 1:1 ratio is described. The THCPSi‐SL nanocomposites (THCPSi‐SLNCs) are formed using a solid‐in‐oil‐in‐water emulsion solvent evaporation method. TEM and FTIR analyses prove that THCPSi nanoparticles are successfully encapsulated in the SLN matrix. The formation of the THCPSi‐SLNCs alters the surface smoothness and hydrophobicity of the THCPSi nanoparticles, and also remarkably enhances their stability in human plasma. After encapsulation, the cytocompatibility of the THCPSi nanoparticles with intestinal, liver, and macrophage cancer cells is also greatly improved. A prolonged release of the model drug, furosemide, from THCPSi‐SLNC is achieved, indicating that the SLN matrix successfully seals the pores of the THCPSi nanoparticles. Flow cytometry and confocal fluorescence microscopy studies demonstrates the significantly reduced cellular association of THCPSi‐SLNCs with the cells comparing to bare THCPSi nanoparticles. Overall, the THCPSi‐SLNCs exhibits superior suspensibility and better stability against aggregation in aqueous buffer solutions, increases the particle surface smoothness and cytocompatibility, reduces the cellular association, increases the in vitro stability in human plasma, and prolonges the drug release. These results suggest that the nanocomposite is a promising nanovector system for drug delivery applications.
Synthesis of Benzoindolines via a Copper‐Catalyzed Reaction of 1‐Bromoethynyl‐2‐(cyclopropylidenemethyl)arenes with N‐Allylsulfonamide
Authors: Li Shaoyu , Li Zhiming , Wu Jie 
Published: November 2012

AbstractA copper‐catalyzed tandem reaction of 1‐bromoethynyl‐2‐(cyclopropylidenemethyl)arenes with N‐allylsulfonamide proceeds smoothly, affording functionalized benzoindolines in moderate to good yields. The transformation is a four‐step cascade involving Ullmann coupling, aza‐Claisen rearrangement, 6π‐electrocyclization, and intramolecular rearrangement.
Impact of UV‐Visible Light on the Morphological and Photochemical Behavior of a Low‐Bandgap Poly(2,7‐Carbazole) Derivative for Use in High‐Performance Solar Cells
Authors: Tournebize Aurélien , Bussière Pierre‐Olivier , Wong‐Wah‐Chung Pascal , Thérias Sandrine , Rivaton Agnès , Gardette Jean‐Luc , Beaupré Serge , Leclerc Mario 
Published: November 2012

AbstractThis paper reports on the photochemical behavior upon exposure to UV‐visible light of a poly(2,7‐carbazole) derivative for use in high‐performance solar cells. Poly[N‐9′‐hepta‐decanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)] (PCDTBT) is one of a relatively large class of push‐pull carbazole‐based copolymers that have been synthesized to better harvest the solar spectrum. The 2,7‐carbazole building block of PCDTBT is also used with different electron‐accepting units in a large variety of low‐band‐gap polymers. The photochemical and morphological behavior of PCDTBT thin films is investigated from the molecular scale to the nanomechanical properties. The photo‐oxidation mechanism is shown to be governed by chain‐scission and cross‐linking reactions. It results in dramatic evolution of the morphology, roughness and stiffness of thin PCDTBT films. Based on the identification of several photoproducts formed along the macromolecular chains or released into the gas phase, the main pathways of PCDTBT photochemical evolution are discussed. These processes first involve the scission of the C–N bond between the carbazole group and the tertiary carbon atom bearing the alkyl side‐chain. Modifications of the chemical structure of PCDTBT, the evolution of its UV‐visible absorbance, and its nanomechanical properties initiated by light irradiation are shown to be closely related.
Perspectives on asymmetry: The erickson lecture
Authors: Cohen M. Michael 
Published: November 2012

AbstractTopics discussed include asymmetry of the brain; prosopagnosia with asymmetric involvement; the blaspheming brain; effects of the numbers of X chromosomes on brain asymmetry; normal facial asymmetry; kissing asymmetry; left‐ and right‐handedness; left‐sided baby cradling; Nodal signaling and left/right asymmetry; primary cilium and left/right asymmetry in zebrafish; right/left asymmetry in snails; species differences in Shh and Fgf8; primary cilium in vertebrate asymmetry; Hedgehog signaling on the cilium; Wnt signaling on the cilium; situs solitus, situs inversus, and situs ambiguus (heterotaxy); ciliopathies; right‐sided injuries in trilobites; unilateral ocular use in the octopus; fiddler crabs; scale‐eating cichlids; narwhals; left‐footed parrots; asymmetric whisker use in rats; and right‐sided fatigue fractures in greyhounds. © 2012 Wiley Periodicals, Inc.
Brief communication: The Granada osteological collection of identified infants and young children
Authors: Alemán Inmaculada , Irurita Javier , Valencia Alba R. , Martínez Argia , López‐Lázaro Sandra , Viciano Joan , Botella Miguel C. 
Published: November 2012

AbstractThe objective of this study is to present the characteristics of a collection of identified infants and young children housed in the Laboratory of Anthropology of the University of Granada, Spain. The sample, which is still being enlarged, is currently composed of 230 complete skeletons aged from 5 months of gestation to 8 years, with a majority below 1 year. It mainly dates from the mid‐20th century. The state of preservation is very good, and antemortem information is available from burial and death certificates, among other documents. Our sample makes an important contribution to the relatively few collections available in the world for investigating the osteological development of the skeletons of infants and young children from a physical anthropological perspective. Am J Phys Anthropol, 2012. © 2012 Wiley Periodicals, Inc.
Synthesis of Aromatic Nitriles Using Nonmetallic Cyano‐Group Sources
Authors: Kim Jinho , Kim Hyun Jin , Chang Sukbok 
Published: November 2012

AbstractAromatic nitriles are prepared efficiently through transition‐metal‐mediated cyanation of aryl (pseudo)halides with metallic cyano‐group sources, such as CuCN, KCN, NaCN, Zn(CN)2, TMSCN, or K4[Fe(CN)6]. However, this approach often suffers from drawbacks, such as the formation of stoichiometric amounts of metal waste, the poisoning of the metal catalysts, or the generation of toxic HCN gas. As a result, a range of “nonmetallic” organic cyano‐group sources have been explored for the cyanation of aryl halides and arene CH bonds. This Minireview summarizes types of nonmetallic cyano‐group sources and their applications in the preparation of aryl nitriles.
Crystallization and thermomechanical properties of PLA composites: Effects of additive types and heat treatment
Authors: Wootthikanokkhan J. , Cheachun T. , Sombatsompop N. , Thumsorn S. , Kaabbuathong N. , Wongta N. , Wong‐On J. , Na Ayutthaya S. Isarankura , Kositchaiyong A. 
Published: November 2012

AbstractThis research work has concerned a study on thermomechanical and crystallization properties of poly(lactic acid) (PLA) composites containing three different types of additives; namely: kenaf fiber (20 pph), Cloisite30B nanoclay (5 pph), and hexagonal boron nitrile (h‐BN; 5 pph). The composites were prepared using a twin screw extruder before molding. Crystallization behaviors of the various composites were also examined using a differential scanning calorimetry. By adding the additives, tensile modulus of the polymer composites increased, whereas their tensile strength and elongation values decreased as compared to those of the neat PLA. Heat distortion temperature (HDT) values of the materials slightly increased, for about 3–5°C. However, after annealing at 100°C, HDT values of the fabricated PLA composites rapidly increased with annealing time before reaching a plateau after 10 min. The HDT values of above 120°C were achieved when 20 pph kenaf fiber was used as an additive. The above results were in a good agreement with DSC thermograms of the composites, indicating that percentage crystallinity of the materials increased on annealing and crystallization rate of the PLA/kenaf system was the highest. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Submicrometer‐sized rubber particles as “craze‐bridge” for toughening polystyrene/high‐impact polystyrene
Authors: Zhu Li Dan , Yang Hong Yu , Cai Gui Di , Zhou Chao , Wu Guang Feng , Zhang Ming Yao , Gao Guang Hui , Zhang Hui Xuan 
Published: November 2012

AbstractSubmicrometer core‐shell polybutadiene‐graft‐polystyrene (PB‐g‐PS) copolymers were synthesized by emulsion grafting polymerization with 1,2‐azobisisobutyronitrile as an initiator. Then, PB‐g‐PS copolymers were blended with high‐impact polystyrene (HIPS) and PS to prepare HIPS/PS/PB‐g‐PS. It is generally accepted that PS could only be toughened by 1–3‐μm rubber particles effectively. From the Izod impact test, however, the results showed that PS could be toughened effectively by submicrometer rubber particles (around 300 nm) in our study. Moreover, the impact strength of HIPS/PS/PB‐g‐PS is much higher than that of HIPS due to the synergism between submicrometer rubber particles and micrometer salami particles. Subsequently, the stress‐whitening zones for HIPS, PS/PB‐g‐PS, and HIPS/PS/PB‐g‐PS were also observed in detail by transmission electron microscope. Based on mechanical properties and deformation morphologies, the deformation mechanism in the HIPS/PS/PB‐g‐PS blends was given as follows: crazes could be initiated from large rubber particles, passed through “craze‐bridge” rubber particles, and ended to neighboring small one, which prevented excessively crazing to be form cracks, absorbed energy, and finally enhanced the toughness of PS. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Temperature sensitivities of doped polyaniline nanoscale films on flexible substrates
Authors: Ahmad Hakeem Abrar , Nayak Debabrata , Panda Siddhartha 
Published: November 2012

AbstractThere is a need to develop more sensitive and cheaper flexible temperature sensors and sensor arrays. In this work, sub‐100‐nm thick polyaniline films of different thicknesses and doping content, coated on flexible PET substrates were used to study the temperature sensing behavior. The material and electrical properties of the films were characterized. The temperature sensitivities, based on DC measurements, varied with the film thickness and the doping content, with the variations being more pronounced at lower thicknesses. Higher sensitivities were obtained with thinner films at lower doping levels and these values are significantly higher than those obtained in commercially available flexible temperature sensors and moreover, these sensitivities could be tuned over a wider range. A possible mechanism was proposed to explain the experimental results, which was supported by the values of the calculated phonon frequencies. AC studies were conducted to identify the transport mechanisms and the transport parameters were calculated. An optimum window of conductivity was needed to obtain high sensitivities and the sensitivities could be tuned by varying the film thickness and the doping content. These films did not show discernable change in resistance upon bending and could be used on curved surfaces. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Enhanced fire behavior of rigid polyurethane foam by intumescent flame retardants
Authors: Hu Xiang‐Ming , Wang De‐Ming 
Published: November 2012

AbstractUsing expandable graphite (EG) and ammonium polyphosphate (APP) as flame retardants, we prepared two series of polyisocyanurate–polyurethane (PIR–PUR) foams (i.e., EG foams filled with different amounts of EG alone and APEG foams containing different amounts of expanded EG and APP) and evaluated the effect of the additives on the physical–mechanical property, fire behavior and thermal stability of the foams based on compressive strength test, limiting oxygen index (LOI), cone calorimeter test, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The addition of EG alone or both EG and APP into the foam greatly influences the physical–mechanical property. The compressive strength of APEG foams is closely related to the apparent density. The LOI value showed good improvement in both EG and APEG foams. The addition of APP in APEG foams gave better fire behavior than the EG foams with an obvious decrease in PHRR and increase in residue. In addition, the TGA curves illustrated that APP might be an effective charring agent to promote char formation. The SEM results showed that the incorporation of APP and EG allowed the formation of a cohesive and dense char layer, which inhibited the transfer of heat and combustible gas and increased the thermal stability of PIR‐PUR. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Online ultrasonic film casting of LLDPE and LLDPE/clay nanocomposites
Authors: Niknezhad Setareh , Isayev Avraam I. 
Published: November 2012

AbstractTransparent cast films of linear low density polyethylene (LLDPE) with nanoclay up to 10 wt % were prepared in one step process using an ultrasonically assisted compounding extruder operating at various ultrasonic amplitudes combined with film casting machine operating at various take up speeds. Thermal, rheological, morphological, and mechanical properties and gas permeability of these films were studied. Ultrasonic treatment introduced an increase in the complex viscosity and storage modulus and a reduction in the tangent loss of LLDPE/clay nanocomposite melts. Cast films prepared by ultrasonic treatment at an amplitude of 7.5 μm showed the highest mechanical properties in both the machine and transverse directions and the lowest oxygen permeability. X‐ray diffraction patterns along with the SEM and TEM images revealed the presence of the exfoliated structure due to the ultrasonic treatment for cast films containing up to 7.5 wt % of clay loading. NMR studies of LLDPE cast films showed an increase of branching due to the ultrasound treatment. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Synthesis and characterization of PS‐b‐PDMS‐b‐PS triblock copolymer
Authors: Jiang Yan , Shi Hongyan , Cai Min , Liang Yuan , Li Bin , Zhang Hongwen , Song Renguo 
Published: November 2012

AbstractA series of polystyrene‐b‐poly(dimethylsiloxane)‐b‐polystyrene (PS/PDMS/PS) triblock copolymers had been synthesized by atom transfer radical polymerization (ATRP). The products had been characterized by Fourier transform infrared, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, contact angle, and scanning electron microscope. The results indicate that the PS chains have been successfully blocked onto the PDMS back bone, and the PS‐b‐PDMS‐b‐PS triblock copolymers have low‐surface tension, good thermal stability, and microphase separation configuration. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Improvement in wettability of pressure‐sensitive adhesive on silicon wafer using crosslinking agent with siloxane groups
Authors: Pang Beili , Ryu Chong‐Min , Kim Hyung‐Il 
Published: November 2012

AbstractAcrylic copolymers are prepared by radical polymerization of 2‐ethylhexyl acrylate, ethyl acrylate, and acrylic acid followed by crosslinking to manufacture the pressure‐sensitive adhesives (PSAs) for silicon wafer protection. Both higher reliability and wettability are required for the protective acrylic PSAs in the semiconductor processing applications. The siloxane linkages are introduced in the acrylic PSAs via crosslinking with siloxane‐containing crosslinking agent to modify the thermal and wetting properties of PSAs efficiently. The more efficient formation of crosslinked network structure was achieved with higher content of tetra‐functional crosslinking agent, and the surface energy of PSAs decreased significantly with increasing the content of siloxane linkage resulting in the improved areal wetting rate. The thermal stability of PSAs was also improved significantly by incorporation of siloxane linkages. The adhesion properties such as peel strength and probe tack of acrylic PSAs decreased significantly by increasing the content of either crosslinking agent or siloxane linkage. The acrylic PSA with siloxane group showed both satisfactory wetting and clean debonding properties for the optimal protection of thin silicon wafers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Preparation and properties of biocomposites composed of sorbitol‐based epoxy resin, tung oil‐pyrogallol resin, and wood flour
Authors: Shibata Mitsuhiro , Teramoto Naozumi , Yoshihara Satoru , Itakura Yusuke 
Published: November 2012

AbstractThe biocomposites composed of sorbitol polyglycidyl ether (SPE), tung oil‐pyrogallol resin (TPG), and wood flour (WF) were prepared by the compression molding at 190°C, and their thermal and mechanical properties were investigated in detail. The epoxy/hydroxy ratio was fixed to 1/1 in the curing reaction of SPE and TPG, based on the fact that the degree of addition of pyrogallol to each tung oil molecule for the TPG used as a flexible bio‐based hardener is evaluated to be 2.3 by 1H‐NMR method. The SPE‐TPG/WF biocomposites showed much higher storage moduli than SPE‐TPG did, although tan δ peak temperatures of the biocomposites (44.5–45.6°C) were a little lower than that of SPE‐TPG (53.5°C). Tensile moduli of the biocomposites increased with an increase of WF content in the range of 0–50 wt %. Furthermore, the biocomposites had a little higher tensile strength than the cured neat resin did. Field emission‐scanning electron microscopy analysis of the biocomposites revealed that WF is tightly incorporated into the crosslinked epoxy resins. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Synthesis, Crystal Structure, and Physical Property of Sterically Unprotected Thiophene/Phenylene Co‐Oligomer Radical Cations: A Conductive π–π Bonded Supermolecular meso‐Helix
Authors: Chen Xiaoyu , Ma Binbin , Chen Shuang , Li Yizhi , Huang Wei , Ma Jing , Wang Xinping 
Published: November 2012

AbstractSterically unprotected thiophene/phenylene co‐oligomer radical cation salts BPnT.+[Al(ORF)4]− (ORF=OC(CF3)3, n=1–3) have been successfully synthesized. These newly synthesized salts have been characterized by UV/Vis‐NIR absorption and EPR spectroscopy, and single‐crystal X‐ray diffraction analysis. Their conductivity increases with chain length. The formed meso‐helical stacking by cross‐overlapping radical cations of BP2T.+ is distinct from previously reported face‐to‐face overlaps of sterically protected (co‐)oligomer radical cations.
Hysteresis Switching Design for Stabilization of a Class of Switched Neutral Systems
Authors: Li Tai‐Fang , Zhao Jun , Dimirovski Georgi M. 
Published: November 2012

AbstractStabilization of a class of switched neutral systems with discrete time‐varying delays is investigated in this paper. The upper bound of the derivative of the discrete time‐varying delay is an arbitrary given unknown constant. Each subsystem is not assumed stable. In order to avoid sliding modes and chattering, a hysteresis switching law is designed based on state space partition, which considers the information of both discrete delays and neutral delays sufficiently. The obtained delay‐dependent stabilization criterion is given in terms of linear matrix inequality by introducing free‐weighting matrices. Finally, a simulation example is given to motivate and exemplify the proposed strategy.
Transient Stability Enhancement of Multi–Machine Power Systems: Synchronization via Immersion of a Pendular System
Authors: Dib W. , Ortega R. , Hill D. 
Published: November 2012

AbstractIn this paper the problem of designing excitation controllers to improve the transient stability of multi‐machine power systems is addressed adopting two new perspectives. First, instead of the standard formulation of stabilization of an equilibrium point, we aim here at the more realistic objective of keeping the difference between the generators rotor angles bounded and their speeds equal—which is called synchronization in the power literature—and translates into a problem of stabilization of a set. Second, we adopt the classical viewpoint of power systems as a set of coupled nonlinear pendula, and express our control objective as ensuring that some suitable defined pendula dynamics are (asymptotically) immersed into the power system dynamics. Our main contribution is the explicit computation of a control law for the two–machine system that achieves global synchronization. The same procedure is applicable to the n–machine case, for which the existence of a locally stabilizing solution is established.