bluuebunny/crossref_metadata_2025_split huggingface dataset:
Green composites reinforced with hemp nanocrystals in plasticized starch
Authors: Cao Xiaodong , Chen Yun , Chang Peter R. , Stumborg Mark , Huneault Michel A. 
Published: June 2008

AbstractNew nanocomposite films were prepared from a mixed suspension of hemp cellulose nanocrystals (HCNs) and thermoplastic starch, or plasticized starch (PS), by the casting and evaporating method. The morphology, thermal behavior, mechanical properties, and water sensitivity of the films were investigated by means of scanning electron microscopy, wide‐angle X‐ray diffraction, differential scanning calorimetry, tensile testing, contact angle measurements, and water absorption. The results indicate that the cellulose nanocrystals dispersed in the PS matrix homogeneously and resulted in an increase in the glass‐transition temperature ascribed to the fact that the flexibility of the starch molecular chains in the starch‐rich phase was reduced because of the strong intermolecular interactions between the starch and stiff HCNs. The films exhibited significant increases in the tensile strength and Young's modulus, from 3.9 to 11.5 MPa and from 31.9 to 823.9 MPa, respectively, with increasing HCN content from 0 to 30 wt %. In addition to the improvement in mechanical properties, the incorporation of HCNs into the PS matrix also led to a decrease in the water sensitivity of the final composite materials. Therefore, the HCNs played an important role in improving the mechanical properties and water resistance of the starch‐based material. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Thermal and rheological properties of poly(vinyl alcohol) and water‐soluble chitosan hydrogels prepared by a combination of γ‐ray irradiation and freeze thawing
Authors: Yang Xiaomin , Zhu Zhiyong , Liu Qi , Chen Xiliang 
Published: June 2008

AbstractPoly(vinyl alcohol) (PVA)/water‐soluble chitosan (ws‐chitosan) hydrogels were prepared by a combination of γ‐irradiation and freeze thawing. The thermal and rheological properties of these hydrogels were compared with those of hydrogels prepared by pure irradiation and pure freeze thawing. Irradiation reduced the crystallinity of PVA, whereas freeze thawing increased it. Hydrogels made by freeze thawing followed by irradiation had higher degrees of crystallinity and higher melting temperatures than those made by irradiation followed by freeze thawing. ws‐Chitosan disrupted the ordered association of PVA molecules and decreased the thermal stability of both physical blends and hydrogels. All the hydrogels showed shear‐thinning behavior in the frequency range of 0.2–100 rad/s. Hydrogels made by freeze thawing dissolved into sol solutions at about 80°C, whereas those made by irradiation showed no temperature dependence up to 100°C. The chemical crosslinking density of the hydrogels made by irradiation followed by freeze thawing was much greater than that of hydrogels made by freeze thawing followed by irradiation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
A fractal model of tensile fracture surfaces for particulate‐filled polymer composites
Authors: Liang J. Z. , Wu C. B. 
Published: June 2008

AbstractTensile mechanical properties are important for the characterization of the utilization performances of materials. Inorganic particles are usually used to reinforce and toughen resins and to reduce costs in the polymer industry. It is, therefore, very important to quantitatively appraise the break way and mechanisms and the reinforcing or toughening effect of the fracture surface of tensile specimens. A tensile fracture surface fractal model of particulate‐filled polymer composites on the basis of fractal theory is established and a corresponding equation for the tensile fracture surface fractal dimension is proposed in this article. Tensile fracture surface fractal dimensions of particulate‐filled polymer composites at filler volume fractions of 2–30% were estimated by means of this equation, and the calculations were compared with the measuring values of calcium carbonate filled acrylonitrile–butadiene–styrene (ABS) resin and titanium dioxide filled ABS resin composites reported in the literature. The results show that the theoretic estimations and the measuring values were roughly close to each other. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Characterization of high‐performance exfoliated natural rubber/organoclay nanocomposites
Authors: Li Peiyao , Wang Li , Song Guojun , Yin Lanlan , Qi Feng , Sun Liangdong 
Published: June 2008

AbstractThe exfoliated natural rubber (NR)/organoclay nanocomposites were successfully prepared with an optimal organoclay by direction blending. The optimal‐type organoclay was chosen by characterization of XRD and the mechanical properties characterization of the NR/organoclay composites from three kinds of organoclay. The observation of transmission electron microscopy (TEM) revealed well‐ordered exfoliated single layers of organoclay. The results of mechanical properties measurement showed that the tensile strength, tensile modulus, and tear strength were improved remarkably with small amounts of organoclay, whose contents were below 5.0 phr. For example, incorporating with 3.0 phr organoclay, the tensile strength and tear strength of nanocomposite were 24.7 MPa and 34.7 kN/m, respectively, which increased ∼ 89.5% and 61.6%. Furthermore, the results of coreinforcement system with high performance indicated a promising application of the organoclay and nanocomposites. The values of the weight‐swelling ratio of nanocomposites decreased much, which meant the oil resistance of nanocomposites enhanced. The TGA results indicated that the thermal stability of nanocomposites was improved. The reduction of oxygen permeability implied the gas‐barrier properties of the nanocomposites improved. Furthermore, the mechanism of barrier of clay layers was discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and simple method of estimating macroporosity of methyl methacrylate–divinylbenzene copolymer beads
Authors: Malik Muhammad Arif , Ali Syed Wasim 
Published: June 2008

AbstractMacroporous methyl methacrylate–divinylbenzene copolymer beads having diameter ∼ 300 μm were synthesized by free radical suspension copolymerization. The macroporosity was generated by diluting the monomers with inert organic liquid diluents. The macroporosity was varied in the range of ∼0.1 to ∼ 1.0 mL/g by varying a number of porosity controlling factors, such as the diluents, solvent to nonsolvent mixing ratios when employing a mixture of the two diluents, degree of dilution, and crosslinkage. Increase in pore volume from 0.1 to 0.45 mL/g resulted in a sharp increase in mesopores having diameters in the range of 3–20 nm whereas the macropores remained negligible when compared with mesopores. Increase in pore volume from 0.45 to 1 mL/g resulted in a sharp increase in macropores, whereas mesopores having diameters in the range of 3–20 nm remained almost constant. The mesopores having diameters in the range of 20–50 nm showed an increase with the increase in pore volume throughout the whole range of pore volume studied. Macroporosity characteristics, i.e., pore volume (Vm), surface area (SA), and pore size distributions were evaluated by mercury penetration method. Statistical analysis of the data obtained in the present study shows that the macroporosity characteristics can be estimated with a reasonable accuracy from the pore volumes, which in turn are determined from the densities of the copolymers. These results are explained on the basis of pore formation mechanism. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Modeling solubility parameters and permeation data of organic solvents versus butyl gloves from four manufacturers
Authors: Evans Katherine M. , Guo Wumin , Hardy James 
Published: June 2008

AbstractA model based on the combination of Hansen solubility parameter theory and Flory‐Rehner polymer solution theory was used to determine the solubility parameters of butyl glove material provided by several different manufacturers using a nonlinear least‐square regression. To evaluate the validity of this model, weight gain data were collected for 26 solvents versus butyl gloves from four different vendors. Good correlation was found with R2 ranging from 0.858 to 0.961, which was attributed to extended weight gain testing and weight gain calculations based on glove sample weight after immersion and postdrying. Steady‐state permeation rates (molar steady‐state permeation rates), breakthrough times, and lag times for the butyl glove samples against solvents were determined and correlated to solvent‐polymer interactive term χϕp2. A high level of correlation was observed for all glove materials. Correlation was also made with permeation data collected from three of the four glove materials, and a high degree of correlation was found with R2 ranging from 0.8644 to 0.9369 for steady‐state permeation rates (molar steady‐state permeation rates), breakthrough times, and lag times. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Radical polymerization behavior of dimethyl vinylphosphonate: Homopolymerization and copolymerization with trimethoxyvinylsilane
Authors: Sato Tsuneyuki , Hasegawa Makoto , Seno Makiko , Hirano Tomohiro 
Published: June 2008

AbstractDialkyl vinylphosphonates such as dimethyl vinylphosphonate (DMVP) and diethyl vinylphosphonate were quantitatively polymerized with dicumyl peroxide (DCPO) at 130°C in bulk. The polymerization of DMVP with DCPO was kinetically studied in bulk by fourier transform near‐infrared spectroscopy (FTNIR) and electron spin resonance (ESR) spectroscopy. The initial polymerization rate (Rp) was given by Rp = k[DCPO]0.5[DMVP]1.0 at 110°C, being the same as that of the conventional radical polymerization involving bimolecular termination. The overall activation energy of the polymerization was estimated to be 26.2 kcal/mol. The polymerization system involved ESR‐observable propagating polymer radicals under the practical polymerization conditions. ESR‐determined rate constants of propagation (kp) and termination (kt) were kp = 19 L/mol s and kt = 5.8 × 103 L/mol s at 110°C, respectively. The molecular weight of the resultant poly(DMVP)s was low (Mn = 3.4 − 3.5 × 103), because of the high chain transfer constant (Cm = 3.9 × 10−2 at 110°C) to the monomer. DMVP (M1) showed a considerably high reactivity in the radical copolymerization with trimethoxyvinylsilane (TMVS) (M2) at 110°C in bulk, giving an inorganic component‐containing functional copolymer with potential flame‐retardant properties; r1 = 1.6 and r2 = 0. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Structural, Functional and Calorimetric Investigation of MosA, a Dihydrodipicolinate Synthase from Sinorhizobium meliloti L5–30, does not Support Involvement in Rhizopine Biosynthesis
Authors: Phenix Christopher P. , Nienaber Kurt , Tam Pui Hang , Delbaere Louis T. J. , Palmer David R. J. 
Published: June 2008

AbstractMosA is an enzyme from Sinorhizobium meliloti L5–30, a beneficial soil bacterium that forms a symbiotic relationship with leguminous plants. MosA was proposed to catalyze the conversion of scyllo‐inosamine to 3‐O‐methyl‐scyllo‐inosamine (compounds known as rhizopines), despite the MosA sequence showing a strong resemblance to dihydrodipicolinate synthase (DHDPS) sequences rather than to methyltransferases. Our laboratory has already shown that MosA is an efficient catalyst of the DHDPS reaction. Here we report the structure of MosA, solved to 1.95 Å resolution, which resembles previously reported DHDPS structures. In this structure Lys161 forms a Schiff base adduct with pyruvate, consistent with the DHDPS mechanism. We have synthesized both known rhizopines and investigated their ability to interact with MosA in the presence and absence of methyl donors. No MosA‐catalyzed methyltransferase activity is observed in the presence of scyllo‐inosamine and S‐adenosylmethionine (SAM). 2‐Oxobutyrate can form a Schiff base with MosA, acting as a competitive inhibitor of MosA‐catalyzed dihydrodipicolinate synthesis. It can be trapped on the enzyme by reaction with sodium borohydride, but does not act as a methyl donor. The presence of rhizopines does not affect the kinetics of dihydrodipicolinate synthesis. Isothermal titration calorimetry (ITC) shows no apparent interaction of MosA with rhizopines and SAM. Similar experiments with pyruvate as titrant demonstrate that the reversible Schiff base formation is largely entropically driven. This is the first use of ITC to study Schiff base formation between an enzyme and its substrate.
Layer‐By‐Layer Assembly of Viral Nanoparticles and Polyelectrolytes: The Film Architecture is Different for Spheres Versus Rods
Authors: Steinmetz Nicole F. , Findlay Kim C. , Noel Timothy R. , Parker Roger , Lomonossoff George P. , Evans David J. 
Published: June 2008

AbstractThe development of tuneable thin film assemblies that contain (bio)nanoparticles is an emerging field in nanobiosciences/nanotechnology. Our research focuses on the utilisation of viral nanoparticles (VNPs) as tools and building blocks for materials science. In previous reports we studied multilayered arrays of chemically modified cowpea mosaic virus (CPMV) particles and linker molecules. To extend these studies and to gain more insights into the architecture of the arrays, we report here on the construction of multilayered assemblies of native plant viral particles and polyelectrolytes. We specifically addressed the question of whether the shape of the VNPs influences the overall structures of the arrays. To study this, we have chosen two particles with similar surface properties but different shapes: CPMV was used as a sphere‐like VNP, and tobacco mosaic virus (TMV) served as a rod‐shaped VNP. The multilayers were self‐assembled on solid supports through electrostatic interactions. Multilayer build‐up was followed by quartz crystal microbalance with dissipation monitoring and UV/Vis spectroscopy. Scanning electron microscopy was used to characterize the topologies of the thin films. Our studies show that shape indeed matters. Incorporation of CPMV in alternating arrays of VNPs and polyelectrolytes is demonstrated; in stark contrast, TMV particles were found to be excluded from the arrays, and floated atop the architecture in an ordered structure.
Stereospecific effects of benzo[d]isothiazolyloxypropanolamine derivatives at β‐adrenoceptors: Synthesis, chiral resolution, and biological activity in vitro
Authors: Comini Mara , Pozzoli Cristina , Incerti Matteo , Rossi Daniela , Collina Simona , Azzolina Ornella , Di Vittorio Elena , Morini Giovanni , Poli Enzo 
Published: June 2008

AbstractWe performed the asymmetric synthesis of four enantiopure benzo[d] isothiazo‐3‐or 5‐yloxypropanolamine derivatives, previously described as competitive antagonists at β‐adrenoceptors. The chemical characterization of each enantiomer was accomplished by1H NMR and HPLC/DAD/CD. The direct chromatographic separation of the enantiomersviachiral HPLC was investigated. The best resolutions were achieved using cellulose tris (3,5‐dimethylphenyl carbamate) (Chiralcel OD‐H) and amylose tris (3,5‐dimethylphenyl carbamate) (Chiralpak AD). The enantiomers obtained had enantiomeric purities suitable for biological assays. Tested in isolated rat cardiac and intestinal tissues to evaluate their effects at β1‐ and β3‐adrenoceptors, the (S)‐enantiomers revealed a higher degree of antagonism than (R)‐enantiomers at both subtypes, even though their activity was greater at the cardiac β1‐subtype. The potent and cardiospecific antagonistic effect exerted by the compounds tested suggests that the benzisothiazole moiety could be an interesting scaffold for discovering new chiral β‐blocking drugs. Chirality, 2009. © 2008 Wiley‐Liss, Inc.
Synaptic circuits of the Drosophila optic lobe: The input terminals to the medulla
Authors: Takemura Shin‐Ya , Lu Zhiyuan , Meinertzhagen Ian A. 
Published: June 2008

AbstractUnderstanding the visual pathways of the fly's compound eye has been blocked for decades at the second optic neuropil, the medulla, a two‐part relay comprising 10 strata (M1–M10), and the largest neuropil in the fly's brain. Based on the modularity of its composition, and two previous reports, on Golgi‐impregnated cell types (Fischbach and Dittrich, Cell Tissue Res.,1989; 258:441–475) and their synaptic circuits in the first neuropil, the lamina, we used serial‐section electron microscopy to examine inputs to the distal strata M1–M6. We report the morphology of the reconstructed medulla terminals of five lamina cells, L1–L5, two photoreceptors, R7 and R8, and three neurons, medulla cell T1 and centrifugal cells C2 and C3. The morphology of these conforms closely to previous reports from Golgi impregnation. This fidelity provides assurance that our reconstructions are complete and accurate. Synapses of these terminals broadly localize to the terminal and provide contacts to unidentified targets, mostly medulla cells, as well as sites of connection between the terminals themselves. These reveal that R8 forms contacts upon R7 and thus between these two spectral inputs; that L3 provides input upon both pathways, adding an achromatic input; that the terminal of L5 reciprocally connects to that of L1, thus being synaptic in the medulla despite lacking synapses in the lamina; that the motion‐sensing input cells L1 and L2 lack direct interconnection but both receive input from C2 and C3, resembling lamina connections of these cells; and that, as in the lamina, T1 provides no output chemical synapses. J. Comp. Neurol. 509:493–513, 2008. © 2008 Wiley‐Liss, Inc.
Glial investment of the adult and developing antennal lobe of Drosophila
Authors: Oland Lynne A. , Biebelhausen John P. , Tolbert Leslie P. 
Published: June 2008

AbstractIn recent years the Drosophila olfactory system, with its unparalleled opportunities for genetic dissection of development and functional organization, has been used to study the development of central olfactory neurons and the molecular basis of olfactory coding. The results of these studies have been interpreted in the absence of a detailed understanding of the steps in maturation of glial cells in the antennal lobe. Here we present a high‐resolution study of the glia associated with olfactory glomeruli in adult and developing antennal lobes. The study provides a basis for comparison of findings in Drosophila with those in the moth Manduca sexta that indicate a critical role for glia in antennal lobe development. Using flies expressing GFP under a Nervana2 driver to visualize glia for confocal microscopy, and probing at higher resolution with the electron microscope, we find that glial development in Drosophila differs markedly from that in moths: glial cell bodies remain in a rind around the glomerular neuropil; glial processes ensheathe axon bundles in the nerve layer but likely contribute little to axonal sorting; their processes insinuate between glomeruli only very late and then form only a sparse, open network around each glomerulus; and glial processes invade the synaptic neuropil. Taking our results in the context of previous studies, we conclude that glial cells in the developing Drosophila antennal lobe are unlikely to play a strong role in either axonal sorting or glomerulus stabilization and that in the adult, glial processes do not electrically isolate glomeruli from their neighbors. J. Comp. Neurol. 509:526–550, 2008. © 2008 Wiley‐Liss, Inc.
Bone morphogenetic protein regulation of enteric neuronal phenotypic diversity: Relationship to timing of cell cycle exit
Authors: Chalazonitis Alcmène , Pham Tuan D. , Li Zhishan , Roman Daniel , Guha Udayan , Gomes William , Kan Lixin , Kessler John A. , Gershon Michael D. 
Published: June 2008

AbstractThe effects of bone morphogenetic protein (BMP) signaling on enteric neuron development were examined in transgenic mice overexpressing either the BMP inhibitor, noggin, or BMP4 under control of the neuron specific enolase (NSE) promoter. Noggin antagonism of BMP signaling increased total numbers of enteric neurons and those of subpopulations derived from precursors that exit the cell cycle early in neurogenesis (serotonin, calretinin, calbindin). In contrast, noggin overexpression decreased numbers of neurons derived from precursors that exit the cell cycle late (γ‐aminobutyric acid, tyrosine hydroxylase [TH], dopamine transporter, calcitonin gene‐related peptide, TrkC). The numbers of TH‐ and TrkC‐expressing neurons were increased by overexpression of BMP4. These observations are consistent with the idea that phenotypic expression in the enteric nervous system (ENS) is determined, in part, by the number of proliferative divisions neuronal precursors undergo before their terminal mitosis. BMP signaling may thus regulate enteric neuronal phenotypic diversity by promoting the exit of precursors from the cell cycle. BMP2 increased the numbers of TH‐ and TrkC‐expressing neurons developing in vitro from immunoselected enteric crest‐derived precursors; BMP signaling may thus also specify or promote the development of dopaminergic TrkC/NT‐3‐dependent neurons. The developmental defects in the ENS of noggin‐overexpressing mice caused a relatively mild disturbance of motility (irregular rapid transit and increased stool frequency, weight, and water content). Although the function of the gut thus displays a remarkable tolerance for ENS defects, subtle functional abnormalities in motility or secretion may arise when ENS defects short of aganglionosis occur during development. J. Comp. Neurol. 509:474–492, 2008. © 2008 Wiley‐Liss, Inc.
Discovery of textual knowledge flow based on the management of knowledge maps
Authors: Luo Xiangfeng , Hu Qingliang , Xu Weimin , Yu Zhian 
Published: June 2008

AbstractTextual knowledge flow (TKF) provides an effective technique and theoretical support for the discovery and cooperation of knowledge innovation, intelligent browsing, and personalized recommendation in Web services and e‐Science Knowledge Grid. For the discovery of TKF, firstly knowledge map (KM) is proposed to represent the textual knowledge; then a hash algorithm is used to code KMs in order to form an Island which contains enormous KMs belonging to a domain. Under the control of the Island, C‐Location and R‐Location are introduced to manage those KMs belonging to an Island. KM‐Chord is proposed to manage the number of Islands, C‐Locations and R‐Locations in Web or a library. With the help of the management of KMs, similar relation and associated relation between KMs are found to build the semantic link network (SLN) between KMs. Based on the SLN and users' profile and input, similar or associated TKF with the user's different demands is activated. Experiments show that the proposed method can effectively discover TKF for Web services and e‐Science Knowledge Grid. Copyright © 2008 John Wiley & Sons, Ltd.