bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas‐Response Studies of Polyaniline Composite Film Containing Zeolite to Chemical Vapors
Authors: Ma Xingfa , Xu Huizhong , Li Guang , Wang Mang , Chen Hongzheng , Chen Song 
Published: November 2006

AbstractSummary: In order to obtain new materials with synergetic or complementary behaviors, polyaniline composite was prepared by chemical oxide method using zeolite as template. A film over interdigital carbon electrodes was formed via casting approach. Gas sensitivity of the film to trimethylamine was examined at room temperature. The results indicated that, in comparison with the polyaniline film prepared by normal in situ polymerization, not only the morphology of polyaniline composite was clearly different, but also the heat stability of polyaniline film was improved significantly by adding zeolite. Gas sensitivity of the composite film to trimethylamine strongly depended on the type of zeolite added. For the system containing β‐zeolite (its specific surface area was 592 m2 · g−1, the size of the channel was 2.27 nm, mole ratio of Si/Al was 60), the gas sensitivity to trimethylamine decreased remarkably compared with that of polyaniline film and for FUYB‐zeolite (its specific surface area was 740 m3 · g−1, the size of the channel was 2.46 nm, mole ratio of Si/Al was 12), it was enhanced significantly. All these may be the results of synergetic effects or complementary behaviors between polyaniline and zeolite. This composite film showed excellent gas sensitivity and stability, rapid response to trimethylamine, and good selectivity to analogous gases while being easily recovered with high‐purity N2 to exhibit good reproducibility.Dynamical response of polyaniline composite film containing zeolite to trimethylamine.magnified imageDynamical response of polyaniline composite film containing zeolite to trimethylamine.
Structure and Morphology Development in Films of mLLDPE/LDPE Blends During Blowing
Authors: Silvestre Clara , Cimmino Sossio , Raimo Maria , Duraccio Donatella , del Amo Fernandez Bernardo , Lafuente Pilar , Sanz Virginia Leal 
Published: November 2006

AbstractSummary: In this work the analysis of the structure orientation, morphology, relaxation time and optical properties of blown films of mLLDPE, LDPE and their blends were performed by using WAXD, SALS, AFM, DSC and rheological and haze tests. For mLLDPE film, the crystals do not present “a”‐axis orientation along the machine direction; a distinct spherulite like superstructure is seen. The film surface is very rough. The values of bulk and surface haze are higher than LDPE and blends, whereas the relaxation time is lower. For LDPE film the (110) planes are parallel and at same time twisted with respect to the layer of the film with the “a”‐axis well oriented along the machine direction. No spherulite superstructure is observed and the surface of the film is more regular. High values of relaxation time are observed. The surface haze is the predominant contribution to the total haze. For the blend films no clear and distinct spherulite structures are observed. The orientation degree increases with composition never approaching that of LDPE. The surface is very more regular and smooth than that of the pure polymers. The haze values are below the values of pure materials. It was underlined that bulk and surface morphology and orientation degree of the crystalline planes along the machine direction dictate the optical properties of the films. Moreover both orientation and morphology are defined by the PE molecular and melt rheology characteristics, processing conditions and blend composition.Total, bulk and surface haze of mLLDPE/LDPE blend films as a function of composition.magnified imageTotal, bulk and surface haze of mLLDPE/LDPE blend films as a function of composition.
Catalyzed Solid‐State Polyamidation
Authors: Vouyiouka Stamatina N. , Papaspyrides Constantine D. , Pfaendner Rudolf 
Published: November 2006

AbstractSummary: The current study is focused on key experiments on catalyzed SSP, examining the effect of selected phosphonates on the overall process rate. Catalyst incorporation was achieved through melt blending in a single screw extruder, providing a suitable and homogenous starting material for the reaction in the solid phase. More specifically, the post‐polycondensation runs were performed in a fixed bed reactor under flowing nitrogen at 160 and 200 °C. The additives used were found to catalyze the reaction in the solid phase, resulting even in tripling the solution relative viscosity after 4 h of SSP. Differences in the catalytic performance of the added materials were observed and correlated to the catalysts properties and morphology. An indicative potential catalysis mechanism is suggested, in which reactivity enhancement through partial attachment of the phosphorus compounds on the polyamide chain is the key step. Finally, the kinetics of the process were examined based on a power‐law rate expression, which was further modified so as to relate the apparent SSP rate constant with the phosphorus concentration.SSP rate constants as a function of catalyst content.magnified imageSSP rate constants as a function of catalyst content.
Preparation and Properties of Vinylester Resin/Clay Nanocomposites
Authors: Ray Dipa , Sengupta Suparna , Sengupta S. P. , Mohanty Amar K. , Misra Manjusri 
Published: November 2006

AbstractSummary: Vinylester resin matrix composites were fabricated with 1, 3, 5 and 10 wt.‐% loadings of organoclay. The composite samples were subjected to various characterization techniques like X‐ray diffraction, flexural testing, dynamic mechanical analysis, thermogravimetric analysis, and scanning electron microscopy. The clay samples as well as the clay–resin composites were investigated by X‐ray diffraction. From the shift in the peak positions and the change in d‐spacing values, it was evident that there was intercalation in the 10 wt.‐% composites, whereas exfoliation occurred in the 1, 3, and 5 wt.‐% composites. The flexural strength and the breaking energy of all the composites were decreased compared with the unfilled resin, but there was an increase in flexural modulus value by 13%. From the dynamic mechanical analysis of the 3 and the 5 wt.‐% composites, it was observed that the loss modulus value was higher in the 3 wt.‐% composites, but the glass transition temperature was slightly higher in the 5 wt.‐% composites. Thermal degradation behavior was also improved in the 5 wt.‐% composites compared with the 3 wt.‐% composites.Fracture surface of 3 wt.‐% clay filled vinylester resin matrix composite in different magnifications.magnified imageFracture surface of 3 wt.‐% clay filled vinylester resin matrix composite in different magnifications.
Study on Superabsorbent Composite, 14
Authors: Zhang Junping , Chen Hao , Li Ping , Wang Aiqin 
Published: November 2006

AbstractSummary: Organo‐attapulgite (organo‐APT) was prepared by modifying APT using four quaternary ammonium salts with various lengths of the alkyl group, including (octyl)trimethylammonium bromide (OTMABr) and (stearyl)trimethylammonium chloride (STMACl), etc. A series of composite hydrogels, poly(acrylic acid)/organo‐APT, from acrylic acid (AA), and organo‐APT was prepared by aqueous polymerization, using N,N′‐methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator. The organification and organification degree of APT as well as the corresponding composites were characterized by FTIR, TGA, and XRD. The effects of the length of the alkyl group for different quaternary ammonium salts, organification degree of APT, and organo‐APT content on water absorbency and swelling behaviors in various electrolyte solutions were investigated in this study. Equilibrium water absorbency strongly depends on chain length of the alkyl group of quaternary ammonium salts, organification degree of APT as well as organo‐APT content. Longer alkyl group, higher organification degree, and proper organo‐APT content are of benefit for the improvement of equilibrium water absorbency. Equilibrium water absorbency in distilled water for PAA/APT was enhanced from 350.1 to 562.1 g · g−1 after 10 wt.‐% organo‐APT, modified with STMACl for the highest degree, was introduced. The kind of cation is the key factor influencing equilibrium water absorbency of these composite hydrogels in electrolyte solutions. Organification of APT could enhance responsiveness of the corresponding composite hydrogel to electrolyte solutions.Schematic structure of PAA/organo‐APT composite in a dry state (left) and in a swollen state (right).magnified imageSchematic structure of PAA/organo‐APT composite in a dry state (left) and in a swollen state (right).
Effect of Carbon Nanofiber Functionalization on the Dispersion and Physical and Mechanical Properties of Polystyrene Nanocomposites
Authors: Morales‐Teyssier Octavio , Sánchez‐Valdes Saul , Ramos‐de Valle Luis Francisco 
Published: November 2006

AbstractSummary: The effect of peroxide functionalization of carbon nanofibers (CNF) on the physical and mechanical properties of polystyrene (PS)–CNF nanocomposites prepared via melt mixing was studied. The CNF functionalization was evidenced by Raman spectroscopy, comparing the ratio of peaks at 1 371 and at 1 590 cm−1 (peaks related to the disordered sp3‐hybridized carbon atom and to the graphitic structure of the sp2‐hybridized carbon atoms, respectively). The variation of the storage (E′) and tensile modulus (E) of the PS–CNF composites as a function of the untreated and peroxide treated CNF concentration were evaluated. Three different peroxide concentrations were used for treating the CNF. It was found that both E′ and E increase with CNF concentration and, in addition, increase further with the peroxide treated CNFs. Nonetheless, it was found that the greater the peroxide concentration used in treating the CNF, the greater the PS degradation via free radical attack on the polymer chain, with the corresponding negative effect on the storage and tensile modulus. Dispersion of the CNF was assessed using scanning and optical microscopy, and the positive effect of the peroxide treatment on the dispersion of the CNF is evidenced.Tensile stress‐strain behavior of PS/CNF nanocomposites.magnified imageTensile stress‐strain behavior of PS/CNF nanocomposites.
Crypticity and functional distribution of the membrane associated α‐L‐fucosidase of human sperm
Authors: Venditti Jennifer J. , Donigan Katherine A. , Bean Barry S. 
Published: November 2006

AbstractTwo distinctive isoforms of the enzyme α‐L‐fucosidase are found within human semen in substantial amounts, suggesting specialized functions during reproduction. The membrane‐associated isozyme of human sperm cells was previously characterized biochemically, and here we report on its subcellular localization. Intact, detergent permeabilized, capacitated, and acrosome‐reacted sperm were investigated using antifucosidase immunofluorescence, binding of the fluorescent fucosylated glycoconjugate RITC‐BSA‐fucose (RBF), and enzyme activity in the presence and absence of selected inhibitors. Both immunolocalization and RBF binding show that fucosidase is broadly distributed over the membrane systems of human sperm, but is relatively enriched within the equatorial segment. Upon detergent treatment or induction of acrosome reaction (AR), a portion of enzyme activity is recoverable in the supernatant, presumably associated with released remnants of the outer acrosomal membrane. Surprisingly, cell‐bound enzyme activity increases sharply following permeabilization of intact sperm, representing cryptic fucosidase that is relatively stable and corresponds with strong fluorescence in the equatorial segment and other sperm membranes. These observations support the notion that the fucosidase has a role in the intimate species signature interactions between sperm and oocyte. Mol. Reprod. Dev. 74: 758–766, 2007. © 2006 Wiley‐Liss, Inc.
Ultrastructural analysis reveals striking differences of intercellular contact lengths in bovine embryos produced in vivo, in vitro and by somatic cell nuclear transfer
Authors: Bhojwani S. , Tomek W. , Jonas L. , Becker F. , Alm H. , Torner H. , Kanitz W. , Poehland R. 
Published: November 2006

AbstractCellular coherence and communication, thus cell‐to‐cell contact is an indispensable premise to sustain the formation of complex, multi‐cellular organisms. We have analyzed intercellular contact lengths in NT‐cloned bovine embryos compared to the in vivo or in vitro produced counterparts. Therefore, ultrastructural analysis was carried out by transmission electron microscopy (TEM) at the 8‐cell and blastocyst stage of development. To obtain embryos generated in vivo, oviducts of superovulated cows were flushed 3 days after insemination, subsequent to slaughter. Standard in vitro maturation (IVM) and ‐fertilization (IVF) were utilized to obtain in vitro embryos. Cloned embryos by somatic nuclear transfer were produced by the handmade cloning (HMC™) procedure. The points of apposition/focal contact points (CPs) between the blastomeres were of the shortest order in cloned embryos (236 ± 135 nm) and of highest order in the in vivo produced embryos (2,085 ± 1,540 nm), although no significant differences regarding the blastomere sizes in the various groups of 8‐cell embryos could be established. In summary, the CP lengths in case of in vitro and in vivo 8‐cell embryos were, on an average, five or nine times longer, respectively, than in the case of the cloned embryos. These differences of CP lengths vanished in embryos reaching the blastocyst stage of embryonic development in all the three groups of embryos. The observed differences of intercellular contact length at distinct stages of embryonic development could be responsible for differences in intercellular communication between the blastomeres at the beginning of cellular differentiation. These may be one reason for the lower developmental competence of cloned (NT) embryos. Mol. Reprod. Dev. 74: 775–784, 2007. © 2006 Wiley‐Liss, Inc.
Conjugate gradient method for the Robin inverse problem associated with the Laplace equation
Authors: Jin Bangti 
Published: November 2006

AbstractThis paper studies a non‐linear inverse problem associated with the Laplace equation of identifying the Robin coefficient from boundary measurements. A variational formulation of the problem is suggested, thereby transforming it into an optimization problem. Mathematical properties relevant to its numerical computation are established. The optimization problem is solved using the conjugate gradient method in conjunction with the discrepancy principle, and the algorithm is implemented using the boundary element method. Numerical results are presented for several benchmark problems with both exact and noisy data, and the convergence of the algorithm with respect to mesh refinement and decreasing the amount of noise in the data is investigated. Copyright © 2006 John Wiley & Sons, Ltd.
The role of ionic liquids in co‐catalysis of Baylis‐Hillman reaction: interception of supramolecular species via electrospray ionization mass spectrometry
Authors: Santos Leonardo Silva , DaSilveira Neto Brenno A. , Consorti Crestina S. , Pavam Cesar Henrique , Almeida Wanda P. , Coelho Fernando , Dupont Jairton , Eberlin Marcos N. 
Published: November 2006

AbstractThe Baylis–Hillman reaction is a general and multifaceted method for CC bond formation in organic synthesis. Using electrospray ionization mass spectrometry in both the positive and negative ion modes, we performed on‐line monitoring of the reaction in the presence of imidazolium ionic liquids. Loosely bonded supramolecular species formed by coordination of neutral reagents, products and the protonated forms of zwitterionic Baylis–Hillman intermediates with cations and anions of ionic liquids were gently and efficiently transferred directly from the solution to the gas phase. Mass measurements and structural characterization of these unprecedented species via collision‐induced dissociation in tandem mass spectrometry experiments were performed. The interception of several supramolecular species indicates that ionic liquids co‐catalyze Baylis–Hillman reactions by activating the aldehyde toward nucleophilic enolate attack and by stabilizing the zwitterionic species that act as the main BH intermediates. Copyright © 2006 John Wiley & Sons, Ltd.
Complex intermediates in the NO insertion reactions into lithium amides
Authors: Vázquez Alvaro , Nudelman N. Sbarbati 
Published: November 2006

AbstractNitric oxide (NO) is known to produce the carcinogenetic nitrosamines but it has also been recently reported, both as a regulator of many important physiological functions and as a possible pharmaceutical delivery system. The present paper describes the NO insertion into NLi bond of lithium amides, to afford very good to almost quantitative yields of N‐nitrosamines. A study of the reaction intermediate suggested a further advantage of this synthetic methodology, widening its scope to its use in tandem reactions. Thus, in situ addition of an organolithium reagent into the NO bond leads to an almost quantitative conversion into the corresponding hydrazone. This compound could further add a second equivalent of the same (or another) organolithium affording substituted hydrazines. The hydrazines thus prepared have a potential chiral carbon, by running the reaction in the presence of a chiral auxiliary, enantiomeric excess could be obtained. By reducing the compound with Raney Ni, the scope of this methology could be enlarged for the potential preparation of chiral primary amines, project that is currently under progress. Copyright © 2006 John Wiley & Sons, Ltd.
Hydrological connectivity and seasonal storage change of tundra ponds in a polar oasis environment, Canadian High Arctic
Authors: Woo Ming‐Ko , Guan Xiu Juan 
Published: November 2006

AbstractTundra ponds are a common type of wetland in the High Arctic. Their preservation is predicated upon ample water supply and storage to overcome evaporation losses. Two years of hydrological study of a cluster of ponds in a polar oasis of the Canadian Arctic showed the dominance of overland flow in the spring as an agent that recharged the pond storage. The freshet produced by snowmelt gave rise to extensive surface flow connections between the ponds and with their surrounding areas, but such flow connectivity lasted only about 2 weeks. After that, the ponds appeared to be separated from lateral drainage. Detailed mapping of the water and frost table positions together with water balance investigation, however, indicated the presence of subsurface flows between some ponds and with their adjacent slope. The flow magnitude was small relative to the vertical processes of evaporation and rainfall. Evaporation loss was mainly responsible for storage depletion, leading to a decline in pond level and shrinkage of open water area, unless major rain events restored the storage (as in 2006). It is postulated that climate warming could increase evaporation and active layer thickness to promote greater loss in surface water storage, or geomorphic processes could breach the pond rims, leading to the demise of ponds. Copyright © 2006 John Wiley & Sons, Ltd.
Profiles of temporal thaw depths beneath two arctic stream types using ground‐penetrating radar
Authors: Brosten Troy R. , Bradford John H. , McNamara James P. , Zarnetske Jay P. , Gooseff Michael N. , Bowden W. Breck 
Published: November 2006

AbstractThaw depths beneath arctic streams may have significant impact on the seasonal development of hyporheic zone hydraulics. To investigate thaw progression over the 2004 summer season we acquired a series of ground‐penetrating radar (GPR) profiles at five sites from May–September, using 100, 200 and 400 MHz antennas. We selected sites with the objective of including stream reaches that span a range of geomorphologic conditions on Alaska's North Slope. Thaw depths interpreted from GPR data were constrained by both recorded subsurface temperature profiles and by pressing a metal probe through the active layer to the point of refusal. We found that low‐energy stream environments react much more slowly to seasonal solar input and maintain thaw thicknesses longer throughout the late season whereas thaw depths increase rapidly within high‐energy streams at the beginning of the season and decrease over the late season period. Copyright © 2006 John Wiley & Sons, Ltd.
Frost boils and soil ice content: field observations
Authors: Overduin P. P. , Kane D. L. 
Published: November 2006

AbstractOur aim is to measure and explain the seasonal changes in soil ice content in the frost boils of Galbraith Lake, Alaska. Instruments were installed in a frost boil to monitor the ground surface position and soil state over a period of 4 years. By comparing the subsidence and thaw rates, we calculate the soil ice content as a function of depth. Measured soil temperatures, liquid water contents and bulk apparent thermal conductivities are used to estimate latent heat production and release in the soil. The frost boil heaves during freezing and settles during thaw while the surrounding tundra heaves negligibly, but subsides measurably. Despite large changes in freezing rates from year to year, total heave and its distribution across the frost boil are similar between years. Winter air temperature and snow depth influence the freezing rate and ice distribution as a function of depth, but not the overall heave. This suggests that heave is controlled by water availability rather than the rate of heat removal from the soil. Areal ground subsidence rates between 2 and 5 cm/yr are due to the disappearance of ice at the base of the active layer, raising the possibility of ongoing thermokarst expansion around Galbraith Lake. Copyright © 2006 John Wiley & Sons, Ltd.
Riverbank freeze‐thaw erosion along a small mountain stream, Nikko volcanic area, central Japan
Authors: Yumoto Manabu , Ogata Takayuki , Matsuoka Norikazu , Matsumoto Eiji 
Published: November 2006

AbstractProcesses of riverbank erosion involve fluvial entrainment, mass failure and subaerial erosion. The role of freeze‐thaw action in these erosion processes was investigated along a small mountain stream in a region with seasonal frost. Riverbank profiles, horizontal erosion, soil temperature, frost depth and soil water content were monitored over 20 months including two winters. Diurnal and annual freeze‐thaw action directly triggers subaerial erosion and indirectly contributes to mass failure and fluvial entrainment. The rate of subaerial erosion reaches a maximum during the thawing period, reinforced by increasing water content and decreasing soil hardness. The subaerial erosion, which occurs uniformly along the riverbank and recurs every year, contributes to progressive deepening of a notch developed above the water level as both preparatory and erosive processes. The overdeepening of the notch decreases bank stability, followed by occasional mass failure immediately after the thawing period and periodic fluvial entrainment during the summer flood period. The annual amount of subaerial erosion is comparable to that of fluvial entrainment. These observations demonstrate that freeze‐thaw erosion plays a fundamental role in erosion of riverbanks subject to deep seasonal frost. Copyright © 2006 John Wiley & Sons, Ltd.