bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and physical properties of low‐molecular‐weight redistributed poly(2,6‐dimethyl‐1,4‐phenylene oxide) for epoxy resin
Authors: Hwang Hann‐Jang , Hsu Su‐Wen , Wang Chun‐Shan 
Published: July 2008

AbstractLow‐molecular‐weight poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) was prepared by the redistribution of regular PPO with 4,4′‐isopropylidenediphenol (bisphenol A) with benzoyl peroxide as an initiator in toluene. The redistributed PPO was characterized by proton nuclear magnetic resonance, mass spectra, and Fourier transform infrared spectroscopy. The redistributed PPO oligomers with terminal phenolic hydroxyl groups and low molecular weights (weight‐average molecular weight = 800–4000) were used in the modification of a diglycidyl ether of bisphenol A/4,4′‐diaminodiphenylmethane network system. The curing behaviors were investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy. The effect of molecular weight and the amount of redistributed PPO oligomers incorporated into the network on the physical properties of the resulting systems were investigated. The thermal properties of the cured redistributed PPO/epoxy resins were studied by dynamic mechanical analysis, thermal mechanical analysis, thermogravimetric analysis, and dielectric analysis. These cured redistributed PPO/epoxy resins exhibited lower dielectric constants, dissipation factors, coefficients of thermal expansion, and moisture absorptions than those of the control diglycidyl ether of bisphenol A based epoxy. The effects of the composition on the glass‐transition temperature and thermal stability are discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and properties of homopolyamide and copolyamides fibers based on 2,6‐bis(p‐aminophenyl)benzo[1,2‐d;5,4‐d′]bisoxazole
Authors: Chen Xiangqun , Sun Qiu , Huang Yudong , Cai Wei 
Published: July 2008

AbstractA novel aromatic homopolyamide with benzobisoxazole units in the main chain was synthesized with 2,6‐bis(p‐aminophenyl)benzo[1,2‐d;5,4‐d′]bisoxazole and terephthaloyl chloride by low temperature solution polycondensation, the inherent viscosity of which was 1.98 dL/g. The diamine and p‐phenylendiamine with terephthaloyl chloride were used to synthesize the copolyamides. The structures of homopolyamide and copolyamides were characterized by IR spectra, elemental analysis, and wide‐angle X‐ray diffraction. Wide‐angle X‐ray diffraction measurements showed that homopolyamide and copolyamides were predominantly crystallinity. The results of thermal analysis indicated that the thermal stabilities of the copolymer increased with an increase of the molar fraction of benzobisoxazole in the copolymers. The thermal stability of the copolyamides with decomposition temperatures (at 10% weight loss) above 570°C was better than that of poly(p‐phenylene terephthalamide) (PPTA). Fibers of homopolyamide and copolyterephthalamides were spun from lyotropic liquid crystal dope in 100% H2SO4. When compared with PPTA fibers prepared under the same conditions, the tensile strengths of copolyamides fibers improved by 20–33% with tensile strengths of 1.81 GPa, tensile moduli of 76 GPa, and elongations at break of 3.8–4.1%, which indicated that copolyamides fibers had outstanding mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Shear flow behaviors of poly(p‐phenylene benzobisoxazole) spinning dope
Authors: Chen Xiaojun , Liu Xiaoyun , Qian Jun , Zhuang Qixin , Li Xinxin , Han Zhewen 
Published: July 2008

AbstractIn this study, the shear flow properties of Poly(p‐phenylene benzobisoxazole) (PBO)/poly(phosphoric acid) (PPA) spinning dope were studied by means of capillary rheometer. The effect of shear stress, temperature, PBO concentration, and PBO molecular weight on the apparent viscosity of PBO/PPA dope was discussed. The results showed that the apparent viscosity of the dope decreased with the increase of the shear stress and the temperature. The flow behavior index increased with the increase of temperature, which indicated that the non‐Newtonian behavior of the dope became weaker at high temperature. Moreover, it was also found that at high shear stress, the apparent viscosity of the dope was insensitive to the temperature, PBO molecular weight, and PBO concentration. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Copolymers of unsaturated and saturated poly(ether ester amide)s: Synthesis, characterization, and biodegradation
Authors: Guo Kai , Chu C. C. 
Published: July 2008

AbstractA series of biodegradable random unsaturated/saturated poly(ether ester amide)s copolymers (USPEEAs) were synthesized by an active solution polycondensation of unsaturated and saturated dicarboxylic acid‐based diester monomers with diamine salts of phenylalanine and saturated oligo(ethylene glycol) (OEG). These USPEEA copolymers were obtained with fairly good yields in DMA solvent. The chemical structures of the USPEEA copolymers were confirmed by both IR and NMR spectra. The molecular weights (Mn and Mw) of USPEEAs measured by GPC ranged from 3 to 27 kg/mol with the molecular weight distribution (MWD) ranging from 1.52 to 2.13. USPEEA copolymers obtained had Tg lower than that of the pure UPEEAs but higher than that of pure saturated poly(ether ester amide)s (SPEEA). An increase in the unsaturated component in USPEEAs led to an increase in their Tg. A preliminary in vitro biodegradation property of USPEEA copolymers were investigated in both pure PBS buffer and α‐chymotrypsin solutions. The USPEEA copolymers showed a pronounced weight loss in enzyme solutions, but a smaller weight loss in a pure PBS. The biodegradation rates of USPEEA copolymers in α‐chymotrypsin solution were much slower than those of pure PEEAs. Therefore, upon adjusting monomers feed ratio, USPEEA copolymers could have controlled chemical, physical, and biodegradation properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
A Femtosecond Study of the Interaction of Human Serum Albumin with a Surfactant (SDS)
Authors: Mandal Ujjwal , Ghosh Subhadip , Mitra Gopa , Adhikari Aniruddha , Dey Shantanu , Bhattacharyya Kankan 
Published: July 2008

AbstractThe interaction of a protein, human serum albumin (HSA) with a surfactant (sodium dodecyl sulfate, SDS) was studied by femtosecond up‐conversion. HSA was labeled covalently with a probe (CPM, 7‐dimethylamino‐3‐(4‐maleimidophenyl)‐4‐methylcoumarin). Binding of SDS to HSA is found to accelerate the solvation dynamics ∼1.3‐fold. The solvation dynamics in HSA displays two time components: 30 ps (20 %) and 800 ps (80 %). When ∼10 SDS molecules bind to HSA the components are 15 ps (40 %) and 800 ps (60 %). It is argued that SDS may increase the solvent exposure of the probe (CPM); it may also displace the buried water molecules in the immediate vicinity of CPM.
PdII‐Catalyzed Asymmetric Addition Reactions of 1,3‐Dicarbonyl Compounds: Mannich‐Type Reactions with N‐Boc Imines and Three‐Component Aminomethylation
Authors: Hamashima Yoshitaka , Sasamoto Naoki , Umebayashi Natsuko , Sodeoka Mikiko 
Published: July 2008

AbstractThis paper describes catalytic asymmetric Mannich‐type reactions of β‐ketoesters and malonates using chiral palladium complexes. Although readily enolizable, carbonyl compounds are attractive substrates, the use of such compounds as nucleophiles in Mannich‐type reactions has not been extensively investigated. In the presence of chiral Pd aqua complexes (2.5 mol %), β‐ketoesters reacted with various N‐Boc imines (Boc=tert‐butoxycarbonyl) to afford the desired β‐aminocarbonyl compounds in good yield with high to excellent stereoselectivity (up to 96:4 d.r., 95–99 % ee in most cases). In these reactions, construction of highly crowded vicinal quaternary and tertiary carbon centers was achieved in one step. A chiral Pd enolate is considered to be the key intermediate. To elucidate the stereoselectivity observed in the reaction, possible transition‐state models are discussed, taking into account steric and stereoelectronic effects. Furthermore, this catalytic system was applied to the Mannich‐type reaction of malonates with N‐Boc imine as well as one‐pot classical aminomethylation of β‐ketoesters using benzylamine salt and formalin. The reactions proceeded smoothly, and the corresponding Mannich products were obtained in high yield with moderate to good enantioselectivity.
Tin‐Free Radical Carbonylation of Alkylsulfonyl Derivatives into Alkylcarbonyl Derivatives
Authors: Kim Sangmo , Lim Kyoung‐Chan , Kim Sunggak 
Published: July 2008

AbstractA simple radical approach based on tin‐free radical carbonylation is devised for the direct conversion of alkylthiosulfonates, alkylsulfonyl cyanides, and alkylsulfonyl oxime ethers into the corresponding alkyl thiol esters, acyl cyanides, and acylated oxime ethers in a single step. The present approach is very simple, highly efficient, and minimizes the formation of byproducts.
Phosphine‐Free Cp*Ru(Diamine) Catalysts in the Hydrogenation of Imines
Authors: Cheruku Pradeep , Church Tamara L. , Andersson Pher G. 
Published: July 2008

AbstractWe previously reported the phosphine‐free Cp*Ru(diamine)‐catalyzed hydrogenation of aryl methyl ketones. Herein we present the first report of ruthenium–diamine‐catalyzed imine hydrogenation to form amines. The most effective catalyst, I/KOtBu, completely converted several imines to amines at room temperature. The effect of electron‐donating and ‐withdrawing groups on the reaction was investigated using a suitable series of substrates. The asymmetric version of the reaction was studied for two substrates, and the chiral amine products could be obtained in moderate enantiomeric excess.
Soft tissue anatomy around the hip and its implications for choice of entry point in antegrade femoral nailing
Authors: Moein C.M. Ansari , Verhofstad M.H.J. , Bleys R.L.A.W. , van der Werken Chr. 
Published: July 2008

AbstractAntegrade intramedullary nailing is an accepted method of treatment for femoral shaft fractures. Entrance of the nail through the trochanteric fossa is currently recommended by some surgeons. This approach results in some cases, however, in loss of abduction strength and persistent pain. Nail insertion at the tip of the greater trochanter may be more favorable. In this study the anatomical relationships of the trochanteric fossa and of the tip of the greater trochanter were explored. Dissection was carried out in 10 fresh human cadaver femurs. The risks and safety of the two entry points with respect to the adjacent soft tissues were assessed. Abductor muscles and tendons, branches of the medial circumflex femoral artery and the hip joint capsule were at risk during nail insertion through the trochanteric fossa. These structures were not endangered during insertion through the trochanteric tip. The reported clinical morbidity after nailing through the trochanteric fossa may result from direct soft tissue injury and may be reduced by choosing the route through the greater trochanter. Clin. Anat. 21:568–574, 2008. © 2008 Wiley‐Liss, Inc.
Probing the Compatibility of Type II Ketosynthase–Carrier Protein Partners
Authors: Worthington Andrew S. , Hur Gene H. , Meier Jordan L. , Cheng Qian , Moore Bradley S. , Burkart Michael D. 
Published: July 2008

AbstractDrug discovery often begins with the screening of large compound libraries to identify lead compounds. Recently, the enzymes that are involved in the biosynthesis of natural products have been investigated for their potential to generate new, diverse compound libraries. There have been several approaches toward this end, including altering the substrate specificities of the enzymes involved in natural product biosynthesis and engineering functional communication between enzymes from different biosynthetic pathways. While there exist assays to assess the substrate specificity of enzymes involved in these pathways, there is no simple method for determining whether enzymes from different synthases will function cooperatively to generate the desired product(s). Herein we report a method that provides insight into both substrate specificity and compatibility of protein–protein interactions between the acyl carrier protein (ACP) and ketosynthase (KS) domains involved in fatty acid and polyketide biosynthesis. Our technique uses a one‐pot chemoenzymatic method to generate post‐translationally modified ACPs that are capable of covalently interacting with KS domains from different biosynthetic systems. The extent of interaction between ACPs and KSs from different systems is easily detected and quantified by a gel‐based method. Our results are consistent with previous studies of substrate specificity and ACP–KS binding interactions and provide new insight into unnatural substrate and protein interactions.
Preparation and Properties of Stable Nanocrystalline Anatase TiO2 Colloids
Authors: Chen X.‐Q. , Shen W.‐H. 
Published: July 2008

AbstractThe nanocrystalline anatase TiO2 colloid has widely been applied in solar energy conversion, photo‐degradation of organic pollutions, photochemical disinfection, processing of sensors, and papermaking. It can be obtained from the hydrolysis of titanyl organic compounds [TiO(OOCCH3)2 and Ti2O(OC4H9)2(OOCCH3)4] at low temperature and normal pressure. TEM (Transmission Electron Microscope), SEM (Scattering Electron Microscope), and LS (Layer Scattering) analysis showed that the colloidal particles are spherical and possess a narrow size distribution, that the mean size (80 °C, 2 h, sample B) is 8.9 nm and its isoelectric point is 6.67. The SBET of the gel powders are 262.7457 m2/g (60 °C, 2 h, sample A) and 258.0024 m2/g (80 °C, 2 h, sample B). Research experiments showed that the turbidities of colloidal solutions decreased along with the decrease of water content in the mixed water‐alcohol dispersants, which predicated that the colloidal stability fell when lowering the electrical conductivity of the dispersant. The zeta potentials of the colloids are 14 mV ∼ 30 mV at pH 4.5 ∼ 6.0 in the presence of 0.5 · 10–2 mol L–1 NaNO3 electrolyte. Furthermore, the UV absorbance of the nanocrystalline TiO2 colloidal solutions increased with a decrease in particle size. The experimental results of photocatalytic degradation of the dye rhodamine revealed that the nanocrystalline TiO2 colloidal particles from this preparation method have good photocatalytic activity, which is better if doped with 0.2 % Fe3+.
The Transient Dynamics of a Small Bubble Rising in a Low Morton Number Regime
Authors: Ohta M. , Tsuji M. , Yoshida Y. , Sussman M. 
Published: July 2008

AbstractThe effect of initial bubble conditions on the transient dynamics of a small bubble (d = 1.5 mm) rising in water is computationally considered by a fully three‐dimensional direct numerical simulation. The numerical algorithm is based on the coupled level set/volume‐of‐fluid (CLSVOF) method for representing and updating the air‐water interface and the sharp interface approach is used to treat the air‐water interfacial boundary conditions. The transient bubble dynamics are investigated using bubbles with five different kinds of shapes as initial bubble conditions. It is shown computationally that the states of bubble shape, bubble trajectory, and terminal velocities greatly depend on initial conditions. As a consequence, the computational results have led us to conclusions in support of the experimental findings by Wu and Gharib [1] and Tomiyama et al. [2]. That is, the dynamic behavior of a rising bubble in a surface tension force dominant system is effected by the initial conditions.
Modeling and Characterization of Air Emissions from Laboratory and Industrial Fluidized Beds
Authors: Whitcombe J. M. , Braddock R. D. , Agranovski I. E. 
Published: July 2008

AbstractA fluidized bed model using several elutriation correlations was developed and tested against an operating fluidized bed used in a Fluidized Catalytic Cracker Unit (FCCU) and a 1:8.5 scale laboratory system. It was found that there was little variation between the emission rates predicted using different elutriation correlations, although the newly developed equations were slightly more accurate for the laboratory‐scale system. Although total emission rates were predicted with reasonable accuracy, the actual volatility and fluctuations seen in real fluidized beds emissions were not predicted. When the model was used to predict particle emission from the industrial FCCU, they preformed poorly, grossly overestimating the actual levels. It was determined that the attrition terms used in emission modeling were inappropriate and that the model preformed better without them, but still overestimated the actual emissions. This overestimation was greater in the industrial system compared with the smaller laboratory system. It was also found that the older elutriation terms were better for predicting industrial emissions compared with those of the smaller scale units.
Heterogeneous Catalysis in Supercritical Media: 2. Near‐Critical and Supercritical Water
Authors: Kruse A. , Vogel H. 
Published: July 2008

AbstractIt was demonstrated in part I, also published in this journal, that supercritical carbon dioxide may be advantageous for the use as a reaction medium in heterogeneously catalyzed reactions. Due to its miscibility with hydrogen, hydrogenations of increased selectivity can be carried out or carbonization of catalysts can be reduced by the dissolution and removal of coke precursors. The drawback of supercritical H2O (Tcrit = 374 °C) as compared to supercritical CO2 (Tcrit = 31 °C) is its relatively high critical point. At these temperatures, organic substances decompose within minutes. Consequently, many reactions are carried out below this critical point, in the so‐called “near‐critical water” or “hot compressed water.” Reaction conditions in near‐critical and supercritical water are also referred to as “hydrothermal.” In spite of the relatively high pressures and temperatures required and the associated high experimental expenditure, many types of reactions have already been studied, as the strong dependence of physical and chemical properties on pressure and temperature makes near‐critical and supercritical water a unique and extraordinary solvent.
The geometry of ASCA
Authors: Smilde Age K. , Hoefsloot Huub. C.J. , Westerhuis Johan. A. 
Published: July 2008

AbstractFor analyzing designed high‐dimensional data, no standard methods are currently available. A method that is becoming more and more popular for analyzing such data is ASCA. The mathematics of ASCA are already described elsewhere but a geometrical interpretation is still lacking. The geometry can help practitioners to understand what ASCA does and the more advanced user can get insight into the properties of the method. This paper shows the geometry of ASCA in both the row‐ and column‐space of the matrices involved. Copyright © 2008 John Wiley & Sons, Ltd.
A New Aptameric Biosensor for Cocaine Based on Surface‐Enhanced Raman Scattering Spectroscopy
Authors: Chen Jiwei , Jiang Jianhui , Gao Xing , Liu Guokun , Shen Guoli , Yu Ruqin 
Published: July 2008

AbstractThe present study reports the proof of principle of a reagentless aptameric sensor based on surface‐enhanced Raman scattering (SERS) spectroscopy with “signal‐on” architecture using a model target of cocaine. This new aptameric sensor is based on the conformational change of the surface‐tethered aptamer on a binding target that draws a certain Raman reporter in close proximity to the SERS substrate, thereby increasing the Raman scattering signal due to the local enhancement effect of SERS. To improve the response performance, the sensor is fabricated from a cocaine‐templated mixed self‐assembly of a 3′‐terminal tetramethylrhodamine (TMR)‐labeled DNA aptamer on a silver colloid film by means of an alkanethiol moiety at the 5′ end. This immobilization strategy optimizes the orientation of the aptamer on the surface and facilitates the folding on the binding target. Under optimized assay conditions, one can determine cocaine at a concentration of 1 μM, which compares favorably with analogous aptameric sensors based on electrochemical and fluorescence techniques. The sensor can be readily regenerated by being washed with a buffer. These results suggest that the SERS‐based transducer might create a new dimension for future development of aptameric sensors for sensitive determination in biochemical and biomedical studies.
Uniform Metal (Hydr)Oxide Particles from Water/Ionic Liquid Precursor (ILP) Mixtures
Authors: Li Zhonghao , Rabu Pierre , Strauch Peter , Mantion Alexandre , Taubert Andreas 
Published: July 2008

AbstractWe have recently shown that the hydrated ionic liquid tetrabutylammonium hydroxide (TBAH) is an efficient ionic liquid precursor (ILP) for the fabrication of ZnO/carbohydrate materials (D. Mumalo‐Djokic, W. B. Stern, A. Taubert, Cryst. Growth Des. 2008, 8, 330). The current paper shows that ZnO is just one example out of the large group of technologically important metal (hydr)oxides that can be made using TBAH. Simply by using different metal acetates as precursors in TBAH, it is possible to make a wide variety of metal (hydr)oxides with well‐defined size, morphology, and chemical composition. It is also possible to dope metal oxide particles or to synthesize mixed metal oxide particles, and therefore to control properties like magnetism.
Magnetic Endohedral Transition‐Metal‐Doped Semiconduncting‐Nanoclusters
Authors: Matxain Jon M. , Formoso Elena , Mercero Jose M. , Piris Mario , Lopez Xabier , Ugalde Jesus M. 
Published: July 2008

AbstractEndohedral first‐row transition‐metal‐doped TM@ZniSi nanoclusters, in which TM stands for the first‐row transition‐metals from Sc to Zn, and i=12, 16, have been characterized. In these structures the dopant metals are trapped inside spheroidal hollow semiconducting nanoclusters. It is observed that some of the transition metals are trapped in the center of mass of the cluster, whereas others are found to be displaced from that center, leading to structures in which the transition metals display a complex dynamical behavior upon encapsulation. This fact was confirmed by quantum molecular dynamics calculations, which further confirmed the thermal stability of endohedral compounds. In the endohedrally‐doped nanoclusters in which the transition‐metal atom sits on the center of mass, the host hollow cluster structure remains undistorted after dopant encapsulation. Conversely, if the encapsulated transition‐metal atom is displaced from the center of mass, the host hollow cluster structure suffers a very tiny distortion. Additionally, it is found that there is negligible charge transfer between the dopant transition‐metal atom and its hollow cluster host and, after encapsulation, the spin densities remain localized on the transition‐metal atom. This allows for the atomic‐like behavior of the trapped transition‐metal atom, which gives rise to their atomic‐like magnetic properties. The encapsulation free energies are negative, suggesting that these compounds are thermodynamically stable.