bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elektronentransfer entlang Peptiden mit Cystein und Methionin als Relais‐Aminosäuren
Authors: Wang Min , Gao Jian , Müller Pavel , Giese Bernd 
Published: May 2009

AbstractSprung ins Wasser: Bei mehrstufigen Elektronentransferreaktionen (ETs) durch Peptide können auch aliphatische Aminosäuren als Relaisstationen fungieren. Mit Cystein erfolgt ein protonengekoppelter Elektronentransfer (PCET), wobei Wasser als Mediator für den Protonentransfer wirkt (siehe Bild).magnified image
Three Redox States of Nitrosyl: NO+, NO., and NO−/HNO Interconvert Reversibly on the Same Pentacyanoferrate(II) Platform
Authors: Montenegro Andrea C. , Amorebieta Valentín T. , Slep Leonardo D. , Martín Diego F. , Roncaroli Federico , Murgida Daniel H. , Bari Sara E. , Olabe José A. 
Published: May 2009

AbstractNot so elusive: [FeII(CN)5(HNO)]3− has been characterized spectroscopically after the two‐electron reduction of nitroprusside (see scheme). The complex is stable at pH 6, slowly decomposing to [Fe(CN)6]4− and N2O. It is deprotonated at increasing pH value with oxidation of bound NO− to [FeII(CN)5(NO)]3−. [FeII(CN)5(HNO)]3− is the first non‐heme iron–nitroxyl complex prepared in aqueous solution that is reversibly redox‐active under biologically relevant conditions.magnified image
Bioinspired Colorimetric Detection of Calcium(II) Ions in Serum Using Calsequestrin‐Functionalized Gold Nanoparticles
Authors: Kim Sunghyun , Park Jeong Won , Kim Dongkyu , Kim Daejin , Lee In‐Hyun , Jon Sangyong 
Published: May 2009

AbstractSeeing is sensing: Calsequestrin (CSQ) functionalized gold nanoparticles undergo calcium‐dependent CSQ polymerization, which results in a clear color change (see picture) together with precipitation. The sensing system is specific for Ca2+ ions and the differences between normal and disease‐associated abnormal (hypercalcemia) Ca2+ ion levels in serum can be distinguished with the naked eye.magnified image
Disterolphospholipids: Nonexchangeable Lipids and Their Application to Liposomal Drug Delivery
Authors: Huang Zhaohua , Jaafari Mahmoud Reza , Szoka Francis C. 
Published: May 2009

AbstractExtreme makeover of cholesterol: Cholesterol exchange is a major reason for the instability of liposomes in blood. The formation of a covalent hybrid between cholesterol and glycerophosphocholine preserves the bilayer‐stabilizing effect of free cholesterol but prevents its transfer from the bilayer. Thus, disterolphospholipids (e.g.1) are valuable new components for liposome formulation.magnified image
Electron Transfer in Peptides with Cysteine and Methionine as Relay Amino Acids
Authors: Wang Min , Gao Jian , Müller Pavel , Giese Bernd 
Published: May 2009

AbstractCaught on the hop: In multistep electron transfer (ET) reactions through peptides, aliphatic amino acids can also act as relay stations. With cysteine, the reaction occurs as a proton‐coupled electron transfer (PCET) with water used as a mediator for the proton transfer (see picture).magnified image
Symmetry‐Based Design for the Chemoenzymatic Synthesis of Oseltamivir (Tamiflu) from Ethyl Benzoate
Authors: Sullivan Bradford , Carrera Ignacio , Drouin Melissa , Hudlicky Tomas 
Published: May 2009

AbstractA short chemoenzymatic formal synthesis of oseltamivir from ethyl benzoate has been achieved. The key steps involve a toluene dioxygenase‐mediated dihydroxylation, hetero‐Diels–Alder cycloaddition, and generation of C4 acetamido functionality. The formal synthesis of oseltamivir is achieved in ten steps and incorporates a unique translocation of the olefin with concomitant elimination of the C2 hydroxy group (see scheme).magnified image
Degradation behavior of nanoreinforced epoxy systems under pulse laser
Authors: Calhoun M. , Kumar A. , Aglan H. 
Published: May 2009

AbstractNanocomposites using EPON 824 as their matrix were exposed to pulse laser at 532 nm for various time intervals. The developed nanomaterials used for this study were manufactured using EPON 824 with multiwalled carbon nanotubes (MWCNTs) at a loading rate of 0.15% by weight and nanoclays at a loading rate of 2% by weight as reinforcements. The effect of laser irradiation on polymer composites has been investigated. The degradation mechanism for the epoxy was of a laser induced burning nature. Of all specimens tested, the ultimate strength of the MWCNT‐reinforced specimens decreased the most as a function of radiation time; the nanoclay‐reinforced epoxy retained the most strength after 2 min of laser radiation. In addition, the threshold fluence for decomposition indicated that less energy was required to initiate decomposition in the MWCNT‐reinforced epoxy than in the nanoclay‐reinforced epoxy. This can be attributed to the high thermal conductivity of the carbon nanotubes. Measurement of surface damage in the material was observed via electron microscopy. Fourier transform infrared spectroscopy was used to investigate changes to the molecular structure as a function of exposure time. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Preparation and thermal and thermo‐oxidative stability of vinylidene chloride‐co‐vinyl chloride copolymer/synthetic hectorite nanocomposites
Authors: Hsieh Tar‐Hwa , Ho Ko‐Shan , Bi Hsiaotao T. , Hung Jan‐Kuan , Han Yu‐Kai , Yang Shin‐Shiao , Chang Yu‐Chen 
Published: May 2009

AbstractPoly(vinylidene chloride‐co‐vinylchloride)/organically modified hectorite (VDC‐VC/SPN) nanocomposites were prepared by melt blending VDC‐VC copolymer with SPN in the presence of dioctyl phthalate, which acted as a plasticizer. As a result, the exfoliated structure was found in the VDC‐VC/SPN nanocomposites. In nitrogen atmosphere, VDC‐VC/SPN nanocomposites exhibited a single‐step thermal degradation. The thermal stability of VDC‐VC/SPN nanocomposites is significantly influenced by the SPN, which was modified with long alkyl ternary ammonium salt. In air atmosphere, VDC‐VC/SPN nanocomposites revealed a two‐step thermo‐oxidative degradation behavior. At the first degradation stage, the weight loss pattern is similar to that of VDC‐VC composites in nitrogen, in which the thermo‐oxidative stability of VDC‐VC/SPN nanocomposites is affected by the ternary ammonium salt and oxygen rather than its morphology. At the second degradation stage, both the enhanced thermo‐oxidative stability and the flame‐retardation ability of VDC‐VC composites are strongly and closely related to the morphology of nanocomposites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci ,2009
Dynamically vulcanized blends of polypropylene and ethylene octene copolymer: Influence of various coagents on mechanical and morphological characteristics
Authors: Babu R. Rajesh , Singha Nikhil K. , Naskar Kinsuk 
Published: May 2009

AbstractDynamically cured blends of polypropylene (PP) and ethylene octene copolymer (EOC) with coagent‐assisted peroxide curative system were prepared by melt‐mixing method. It was well established that PP exhibits β‐chain scission in the presence of peroxide. Principally, incorporation of a coagent increases the crosslinking efficiency in the EOC phase and decreases the extent of degradation in the PP phase. The present study mainly focused on the influence of three structurally different coagents, namely, triallyl cyanurate (TAC), trimethylol propane triacrylate (TMPTA), and N,N′‐m‐phenylene dimaleimide (MPDM), on the mechanical properties of the PP/EOC thermoplastic vulcanizates (TPVs). The reactivity and efficiency of different coagents were characterized by cure study on EOC gum vulcanizate. TAC showed the highest torque values followed by MPDM and TMPTA. Significant improvements in the physical properties of the TPVs were inferred with the addition of coagents. Among the three coagents used, MPDM showed the best balance of mechanical properties in these TPVs. The results indicated that torque values obtained during mixing and the final mechanical properties can be correlated. Different aspects were explained for the selection of a coagent that forms a product with desired properties. The phase morphologies of the TPVs prepared were studied by scanning electron microscopy. Tensile fracture patterns were also analyzed to study the failure mechanism of the samples. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Reduction of free radicals and endotoxin by conjugated linoleic acid loaded in an in situ‐synthesized poly(N‐isopropyl acrylamide) thin layer
Authors: Huang Li‐Heng , Wu Jiunn‐Tzong , Su Te‐Li , Yang Ming‐Chien , Kuo Yu‐Lin , Kung Fu‐Chen 
Published: May 2009

AbstractA thin layer of poly(N‐isopropyl acrylamide) (pNIPAAm) was synthesized in situ on the surface of hydrolyzed polyacrylonitrile (PAN) membrane. This thin layer exhibited both pH response due to the poly(acrylic acid) moiety and temperature response due to the pNIPAAm moiety. The swelling behavior of the membranes was evaluated under various temperatures and pH. The curve of the swelling ratio for the PAN‐NIPAAm showed a lower critical solution temperature. Then, conjugated linoleic acid (CLA) was loaded into the pNIPAAm layer. The effects of CLA on the blood coagulation and oxidative stress were evaluated with the use of human blood. The level of reactive oxygen species (ROS) was measured by the chemiluminescence (CL) method to evaluate the oxidative stress. Furthermore, the removal of bacterial endotoxin (lipopolysaccharide) by CLA‐loaded PAN‐NIPAAm was measured with enzyme‐linked immunosorbent assay. The results show that the LCST swelling curve was at 37°C. PNIPAAm chains form expanded structures under 37°C. At temperatures greater than 37°C, however, the chains form compact structures by dehydration. This makes PNIPAAM membrane due to rapid hydration and dehydration changes of the polymer chain. In addition, the swelling ratio increased by 71% when the pH increased from 5 to 10. The concentration of LPS can be reduced by CLA‐loaded PAN‐NIPAAm 2.1 and 1.2 times of that by unmodified PAN and PAN‐NIPAAm membranes, respectively. In addition, the level of ROS against CLA‐loaded PAN‐NIPAAm was reduced significantly than that against unmodified PAN and PAN‐NIPAAm. Therefore CLA‐loaded PAN‐NIPAAm membrane could offer protection for patients against oxidative stress and could also inhibit lipopolysaccharide for clinical applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Preparation and properties of poly(WPSF‐co‐butyl acrylate) copolymer emulsion with ultrasonic radiation II. Monomer conversion rate and characterization
Authors: Ai Zhao Quan , Zhang Hai Rong , Liu Qing , Hu Ying 
Published: May 2009

AbstractA stable emulsion of poly(WPSF‐co‐butyl acrylate) based on butyl acrylate, waste polystyrene foam was synthesized through emulsion polymerization using sodium dodecyl sulfate and octyl phenyl polyoxyethylene ether as surfactant, ammonium persulfate and sodium hydrogen bisulfate as mixed redox initiator, under ultrasound irradiation in the absence of inert gas. The effects of various copolymerization conditions on the monomer conversion were reported. The copolymers were characterized by means of IR, 1HNMR, and gel permeation chromatography. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Thermal and mechanical characterization of maleimide‐functionalized copoly(urethane‐urea)s
Authors: Gaina Constantin , Gaina Viorica , Ciobanu Constantin 
Published: May 2009

AbstractMaleimide functionalized copoly(urethane‐urea)s were prepared by the reaction of a binary mixture of dibenzyldiisocyanate and 5‐maleimidoisophthalic diisocyanate with a macrodiol (PEGA‐2000), using diethylene glycol and trimethylol‐propane as chain extender and crosslinkers in toluene‐dichloromethane solutions at the ratio NCO/OH = 1.2. Structures of polymers were confirmed by IR spectroscopy and properties were studied by thermal and mechanical analysis (dynamic mechanical analysis (DMA), differential scanning calorimetry, thermogravimetric analysis, stress‐strain) and other physical methods. Maleimide modification increased the storage modulus and Young's modulus of copoly(urethane‐urea)s, slightly increased their glass transition temperature from −10.6°C to −6.3°C. Copoly(urethane‐urea) networks obtained by thermal polymerization of maleimide functions showed significantly increased of the mechanical properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
The characterization of polyaniline and polypyrrole composites by pyrolysis mass spectrometry
Authors: Hacaloglu Jale , Tezal Feride , Kücükyavuz Zühal 
Published: May 2009

AbstractIn this work, direct insertion probe pyrolysis mass spectrometry technique was applied to investigate the thermal and structural characteristics of electrochemically prepared polyaniline (PANI), polypyrrole (PPy), and their composites/copolymers synthesized either by electrochemical polymerization of pyrrole on PANI‐coated electrode (PANI/PPy) or by coating PANI on PPy (PPy/PANI) in H2SO4 solutions. It has been determined that the polymer first coated on the electrode degraded to a certain extent during the polymerization of the second. The extent of degradation was greater for PPy and increased with the increase in acid concentration. On the other hand, the detection of mixed dimers confirmed copolymer formation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Electromagnetic interference shielding behavior of polyaniline/graphite composites prepared by in situ emulsion pathway
Authors: Saini Parveen , Choudhary Veena , Sood K. N. , Dhawan S. K. 
Published: May 2009

AbstractPolyaniline–graphite composites were prepared via in situ emulsion pathway, using different weight ratios of aniline to graphite. These composites were characterized for thermal, electrical, and spectral attributes. The thermal stability (∼ 230°C) and electrical conductivity (67.9 S/cm) were improved significantly as compared with polyaniline doped with conventional inorganic dopants such as HCl (140°C and 10 S/cm). Scanning electron micrographs indicated a systematic change in morphology from globular to flaky with increasing amounts of graphite. The relative shifting of UV–visible bands indicates that some interactions exist between doped polyaniline and graphite. Absorption‐dominated total electromagnetic interference shielding effectiveness of the order of −33.6 dB suggests that these materials can be used as futuristic microwave shielding materials. The good electrical conductivity and thermal stability make them ideal candidates for preparing conducting composites by melt blending with conventional thermoplastics such as polyethylene, polypropylene, and polystyrene, etc. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Modification of cellulose acetate with oligomeric polycaprolactone by reactive processing: Efficiency, compatibility, and properties
Authors: Klébert Szilvia , Nagy Lajos , Domján Attila , Pukánszky Béla 
Published: May 2009

AbstractOligomeric polycaprolactone (oPCL) was used for the modification of cellulose acetate by reactive processing in an internal mixer at 180°C, 50 rpm, 60 min reaction time, and 45 wt % caprolactone (CL) content. The product of the reaction was characterized by several analytical techniques and its mechanical properties were determined by dynamic mechanical thermal analysis and tensile testing. The synthesized oPCL contained small and large molecular weight components. The small molecular weight fraction plasticized cellulose acetate externally and helped fusion. Although composition and structure did not differ considerably from each other when CL monomer or polycaprolactone oligomer was used for modification, the grafting of a few long chains had considerable effect on some properties of the product. The large molecular weight chains attached to CA increased the viscosity of the melt considerably and resulted in larger deformability. oPCL homopolymer is not miscible with cellulose acetate and migrates to the surface of the polymer. Exuded polycaprolactone oligomers crystallize on the surface but can be removed very easily. More intense conditions may favor the grafting of long chains leading to polymers with advantageous properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Durability enhancement of Nafion® fuel cell membranes via in situ sol‐gel‐derived titanium dioxide reinforcement
Authors: Patil Yatin , Mauritz Kenneth A. 
Published: May 2009

AbstractTo improve durability of Nafion® membranes, samples were modified via an in situ sol‐gel polymerization of titanium isopropoxide to generate titania quasi‐networks in the polar domains. The incorporated titania reduced water uptake but equivalent weight was essentially unchanged. Fuel cell performance of the modified membrane was inferior to that of the unfilled membrane although these were considered as model studies with focus on mechanical durability. Mechanical analysis of contractile stress buildup during drying from a swollen state in samples clamped at constant length demonstrated considerable reinforcement of Nafion® by the titania structures. Tensile studies showed that at 80°C and 100% relative humidity the dimensional change of the composite membrane is one half and the initial modulus is three times higher than that of the unmodified membrane. During an open circuit voltage decay test the voltage decay rate for the modified membrane is 3.5 times lower than that of control Nafion®. Fluoride emission for the composite is at least an order of magnitude lower than that of the control Nafion® membrane indicating reduced chemical degradation. These model studies indicate that this in situ inorganic modification offers a way to enhance fuel cell membrane durability by reducing both physical and chemical degradation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
The role of auxiliary monomers and emulsifiers on wet scrub resistance of various latex paints at different pigment volume concentrations
Authors: Khorassani M. , Afshar‐Taromi F. , Mohseni M. , Pourmahdian S. 
Published: May 2009

AbstractThis work is an attempt to study the effect of different latex types containing various auxiliary monomers and emulsifiers on their pigmentation and their corresponding behavior on scrub resistance. The auxiliary monomers investigated were acrylic acid (AA), methacrylic acid (MAA), and itaconic acid and the emulsifiers contained sodium lauryl sulfate (SLS) and sodium dodecylbenzene sulfonate (SDBS). It was shown that a semibatch polymerization technique which led to smaller particles and sharper size distributions is preferable. The best wet scrub results were obtained by using MAA and SLS. It was also shown that the proper selection of an auxiliary monomer generally depended on the range of incorporated pigment volume concentration (PVC). At high PVCs, AA gave better performances compared with MMA. The reverse effect was shown to occur at low PVCs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Introduction of a new vegetable fiber for textile application
Authors: Mortazavi Sayed Majid , Moghadam Meghdad Kamali 
Published: May 2009

AbstractFinding textile applications for a new or underused fiber is always very attractive, especially when the fiber is natural and indigenous. Leafiran fiber is derived form the leaves of a plant called Typha australis, which belongs to the family Typhaceae. The fiber was obtained by chemical retting. Some properties of this fiber, such as its tensile strength, chemical composition, thermal properties, moisture absorption, and IR spectra, were determined. Leafiran is a lignocellulosic fiber having a cellulose content of 54%, a moisture regain of 8–10%, and a tenacity of 29 cN/tex. The results show that Leafiran could be an ideal replacement for some widely used natural textile fibers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Dynamic study of free volume properties in polyethylene/styrene butadiene rubber blends by positron annihilation lifetime method
Authors: Mostafa N. , Ali E. Hassan , Mohsen M. 
Published: May 2009

AbstractPositronium (Ps) formation in low and high‐density polyethylene (LDPE and HDPE) and styrene butadiene rubber (SBR), as well as in their blends (LDPE/SBR: 50/50 and HDPE/SBR: 50/50) has been investigated by positron annihilation lifetime (PAL) measurements as a function of low temperature (100–300 K). The glass transition temperature (Tg) for the initial polymers and their blends are determined by ortho‐positronium (o‐Ps) lifetime, τ3 versus temperature as well as by differential scanning calorimetry (DSC) measurements. The temperature dependence of nanoscale free volume size shows similar trend for all the investigated samples indicating an abrupt change at Tg, which is found to be higher for SBR sample characterized by its high chain mobility. In addition, The Tg values deduced from PAL measurements are compared with the corresponding data deduced from DSC. The variation of o‐Ps formation probability I3 versus temperature for polyethylene and their blends were interpreted in the frame work of spur reaction model of Ps formation. On the other hand, the lifetime coefficient below and above Tg is found to be one order of magnitude larger than the linear expansion coefficient. This constitutes evidence that Ps is only probing free volumes. The results obtained from change in free volume–hole distribution with temperature reflect both thermal expansion and increase in free volume–hole size with the rise in temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Terpolymer resin–III: Synthesis and characterization of 8‐hydroxyquinoline–dithiooxamide–formaldehyde terpolymer resins
Authors: Katkamwar S. S. , Zade A. B. , Rahangdale S. S. , Gurnule W. B. 
Published: May 2009

AbstractTerpolymer resins (8‐HQDF) were synthesized by the condensation of 8‐hydroxyquinoline (8‐HQ) and dithiooxamide (D) with formaldehyde (F) in the presence of acid catalyst and using varied molar ratios of reacting monomers. Terpolymer resins compositions have been determined on the basis of their elemental analysis and the number average molecular weights of these resins were determined by conductometric titration in non‐aqueous medium. Viscometric measurements in dimethyl formamide (DMF) have been carried out with a view to ascertain the characteristic functions and constants. The UV‐visible, FTIR, and proton nuclear magnetic resonance (H+ NMR) spectra were studied to elucidate the structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Humidity‐dependent bending recovery and relaxation of human hair
Authors: Wortmann Franz J. , Stapels Michael , Chandra Lalitesh 
Published: May 2009

AbstractThe time‐dependent bending recovery of human hair fibers was investigated for a variety of relative humidities and aging times. The data were analyzed on the basis of a viscoelastic filament/matrix model and the Denby‐equation, containing the parameter K as the ratio of the elastic bending rigidities of the matrix and the filaments and the Kohlrausch‐Williams‐Watts (KWW) function as relaxation function. The first stage of the analysis ascertained that the recovery curves shift with aging time on the time scale with the expected aging rate of μ ≈ 1. The second stage showed that the shape factor of the KWW function exhibits a mean value across the aging and humidity range of m = 0.28, which is close to the “universal” value of 1/3. On this basis, it was found that virtually no change occurs for the modulus ratio for low water contents up to about 10%, being constant at K0= 6 .1, while linearly decreasing beyond this threshold. The reduced, characteristic relaxation time drops on the log‐time scale from logτr(0) = 0.47 for the dry fiber linearly with water content, covering about two thirds of a decade for 0–20% water content. With the pronounced humidity dependence of the parameters, hair shows what is termed hydro‐rheologically complex (HRC) in analogy to thermo‐rheologically complex behavior. Using the HRC approach, the dynamical mechanical performance of hair (1 Hz) was calculated for a range of water contents and aging times and found to be in good general agreement with experimental data. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009