bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoinitiating polymerization to prepare biocompatible chitosan hydrogels
Authors: Hu Xiaohong , Gao Changyou 
Published: July 2008

AbstractChitosan hydrogels were prepared from water soluble chitosan derivatives (chitosan‐MA‐LA, CML) by photoinitiating polymerization under the existence of Irgacure2959 and the irradiation of UV light. The CML was obtained by amidation of the amine groups of chitosan with lactic acid and methacrylic acid. Gelation time of the hydrogel could be adjusted within a range of 5–50 min, and controlled by factors such as the degree of MA substitution, initiator concentration, existence of oxygen, and salt. The dry hydrogel adsorbed tens to hundred times of water, forming a highly hydrated gel. The swelling ratio was smaller at the higher degree of MA substitution, higher pH, and higher salt concentration. Rheological test showed that the hydrogel is elastomeric in the measuring frequency range, with a storage modulus and loss modulus of 0.8–7 kPa and 10–100 Pa, respectively. In vitro culture of chondrocytes demonstrated that the cells could normally proliferate in the extractant of the hydrogels, showing no cytotoxicity at lower initiator concentration. By contrast, the extractant of the hydrogel made by the redox initiating system, i.e., ammonium persulfate (APS) and N,N,N′,N′‐tetramethylethylenediamine (TEMED), showed apparent cytotoxicity. Thus, the chitosan hydrogels initiated by the Irgacure2959 have better comprehensive properties, in particular better biocompatibility, and are more suitable for biomedical applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis of poly(methyl methacrylate)/silica nanocomposite through emulsion polymerization using dimethylaminoethyl methacrylate
Authors: Barari Mohammad , Sharifi‐Sanjani Naser 
Published: July 2008

AbstractPolymer/Silica nanocomposite latex particles were prepared by emulsion polymerization of methyl methacrylate (MMA) with dimethylaminoethyl methacrylate (DM). The reaction was performed using a nonionic surfactant and in the presence of silica nanoparticles as the seed. The polymer‐coated silica nanoparticles with polymer content and number average particle sizes ranged from 32 to 93 wt % and 114–310 nm, respectively, were obtained depending on reaction conditions. Influences of some synthetic conditions such as MMA, DM, surfactant concentration, and the nature of initiator on the coating of the silica nanoparticles were studied. Electrostatic attraction between anionic surface of silica beads and cationic amino groups of DM is the main driving force for the formation of the nanocomposites. It was demonstrated that the ratio of DM/MMA is important factor in stability of the system. The particle size, polymer content, efficiency of the coating reaction, and morphology of resulted nanocomposite particles showed a dependence on the amount of the surfactant. Zeta potential measurements confirmed that the DM was located at the surface of the nanocomposites particles. Thermogravimeteric analysis indicated a relationship between the composition of polymer shell and polymer content of the nanocomposites. The nanocomposites were also characterized by FTIR and differential scanning calorimetry techniques. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Cross‐linked and uncross‐linked biodegradable nanocomposites. I. Nonisothermal crystallization kinetics and gas permeability
Authors: Shih Y. F. , Wang T. Y. , Jeng R. J. , Wu J. Y. , Wuu D. S. 
Published: July 2008

AbstractVarious nanocomposites of poly(butylene succinates) (PBS) with different ratios of organically modified layered silicates (OMLS) were prepared. Moreover, such PBS nanocomposites cross‐linked by dicumyl peroxide (DCP) were also prepared in this work. Effects of cross‐linking and OMLS on nonisothermal crystallization kinetics and the gas permeability of PBS samples were investigated further. WAXD indicates that the layers of clay were intercalated by the modifiers, and that the interlayer distance of OMLS in the nanocomposites could be expanded to about 2.96 nm. The results of DSC analysis revealed that the crystallization temperatures of nanocomposites shifted to the lower temperature with the increase of OMLS content. With the addition of OMLS, crystallinity was decreased, whereas the half‐life of crystallization was increased. On the other hand, even the cross‐linked effects also increased the half‐life of crystallization of the materials, but did not necessarily decrease crystallinity in all cases. Moreover, the PBS/OMLS nanocomposites showed a 23.87–46.64% decrease in permeability of oxygen when compared with the pristine PBS sample. Yet, the cross‐linked nanocomposites exhibited decrements of 6.38–39.53%. This indicates that the gas permeability of PBS was more effectively depressed by the addition of OMLS than by the cross‐linking reaction. The cross‐linked structure of polymer seemed not to be very effective in decreasing the gas permeability of PBS. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Interferometric study of creep deformation and some structural properties of polypropylene fiber at three different temperatures
Authors: Fouda I. M. , EL‐Farahaty K. A. , Seisa E. A. 
Published: July 2008

AbstractInfluence of temperature on creep deformation for polypropylene PP fiber under a constant load was studied interferometrically. The automated multiple‐beam Fizeau system in transmission was equipped with a mechanical creep device attached to a wedge interferometer. This system was used to determine the optical properties (n∥, n⟂, and Δn) of PP fiber during the creep process at constant loading with varying temperature. The creep compliance was drawn as a function of both time and temperature. An empirical formula was suggested to describe the creep compliance curves for PP fibers and the constants of this formula were determined. Two Kelvin elements combined in series were used to provide an accurate fit to the experimental compliance curves. The stress–strain curve via creep was studied to determine some mechanical parameter of PP fibers, Young's modulus E, yield stress σy, and yield strain εy. The optical orientation function f(θ), the dielectric constant d, the dielectric susceptibility χ, the surface reflectivity $ \overline R $, and the average work per chain W′ were also calculated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Effect of fiber length on processing and properties of extruded wood‐fiber/HDPE composites
Authors: Migneault Sébastien , Koubaa Ahmed , Erchiqui Fouad , Chaala Abdelkader , Englund Karl , Krause Cornelia , Wolcott Michael 
Published: July 2008

AbstractFiber length and distribution play important roles in the processing and mechanical performance of fiber‐based products such as paper and fiberboard. In the case of wood–plastic composites (WPC), the production of WPC with long fibers has been neglected, because they are difficult to handle with current production equipment. This study provides a better understanding of the effect of fiber length on WPC processing and properties. The objectives of this study were therefore to determine the role of fiber length in the formation process and property development of WPC. Three chemithermomechanical pulps (CTMP) with different lengths, distributions, and length‐to‐diameter ratios (L/D) were obtained by mechanical refining. Length, shape, and distribution were characterized using a fiber quality analyzer (FQA). The rheometer torque properties of high‐density polyethylene (HDPE) filled with the pulps at different loads were studied. Variations in fiber load and length distribution resulted in significant variations in melting properties and torque characteristics. Composites from the three length distributions were successfully processed using extrusion. Physical and mechanical properties of the obtained composites varied with both length distribution and additive type. Mechanical properties increased with increasing fiber length, whereas performance in water immersion tests decreased. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and characterization of an amphiphilic pluronic‐poly(D,L‐lactide‐co‐glycolide) copolymer and their nanoparticles as protein delivery systems
Authors: Wu Yan , Che Fu‐Bin , Chen Jiang‐Han 
Published: July 2008

AbstractA new amphiphilic Pluronic (F68)‐PLGA copolymer, which can be used to prepare the stealth or long‐circulating nanoparticles, was synthesized with Pluronic (F68), DL‐Lactide, and glycolide. The structures of Pluronic (F68)‐PLGA copolymer as the products were characterized with infrared spectrometry, nuclear magnetic resonance and their molecular weights were determined by gel permeation chromatography. Two methods, double emulsion (DE) and nanoprecipitation (NP), were employed to fabricate the polymeric nanoparticles. Bovine serum albumin (BSA) was loaded into nanoparticles as a model protein. Influence of the preparation conditions on the nanoparticles size, encapsulation efficiency, and release profile in vitro was investigated. They showed the entrapment efficiency of 42.9–63.4% and the average diameter of 119.1–342.8 nm depending on the fabrication technique of nanoparticles and the type of copolymer. The stability maintenance of BSA in the nanoparticle release in vitro was also measured via sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE), circular dichroism (CD), and fluorescence spectrometry. The results showed that the new copolymer could load BSA effectively and BSA kept stable after it was released from the nanoparticles. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
A comparison of the properties of rice husk ash, silica, and calcium carbonate filled 75 : 25 NR/EPDM blends
Authors: Arayapranee Wanvimon , Rempel Garry L. 
Published: July 2008

AbstractThe effects of incorporation of three different fillers, i.e., rice husk ash (RHA), silica, and calcium carbonate (CaCO3), over a loading range of 0–60 phr on the curing characteristics, processability, mechanical properties, and morphology of 75 : 25 natural rubber (NR)/ethylene‐propylene‐diene monomer (EPDM) blends were studied using a conventional vulcanization system. Filler loading and type influence the processability of the blends in which RHA and CaCO3 offer better processing advantage over silica. The best improvement in the tensile and tear strength and abrasion resistance of the 75 : 25 NR/EPDM blends with additional fillers was achieved when filled with silica. However, RHA and CaCO3 were better in resilience property compared to that of silica. The RHA filled blends showed higher failure properties and abrasion resistance but lower ozone resistance than that containing CaCO3. Scanning electron micrographs revealed that the morphology of the blend filled with silica is finer and more homogenous compared to the blend filled with RHA and CaCO3. According to these observations, RHA can be used as a cheaper filler to replace CaCO3 in rubber blends where improved mechanical properties are not so critical. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis–structure–performance relationship of cocondensed phenol–urea–formaldehyde resins by MALDI‐ToF and 13C NMR
Authors: Du Guanben , Lei Hong , Pizzi A. , Pasch H. 
Published: July 2008

AbstractMatrix assisted laser desorption ionization time of flight (MALDI‐ToF) mass spectrometry has consistently confirmed on a number of PUF resins that phenol–urea cocondensates exist in phenol–urea–formaldehyde (PUF) resins. A noticeable proportion of methylene‐linked phenol to urea cocondensates were detected in all the PUF resins tried, alongside methylene bridges connecting phenol to phenol and urea to urea. The PUF, PF, and UF oligomers formed were identified. Variations of the PUF preparation procedure did always yield a certain proportion of the mixed phenol to urea cocondensates. Their relative proportion was determined and related the synthesis procedure used. Comparison of the MALDI‐ToF results with a 13C NMR investigation showed that in a real PUF resin in which phenol to urea cocondensates were identified the methylene bridge NMR signal at 44 ppm, characteristic of phenol to urea unsubstituted model compound cocondensates, does not appear at all. This confirmed that this peak cannot be taken as an indication of the existence of phenol and urea condensation under actual resin preparation conditions. The peak indicating cocondensation in PUF resins in which the phenolic nuclei and urea are substituted appears instead at 54.7–55.0 ppm. Thermomechanical analysis has again confirmed that the resin gel times greatly accelerates with increasing urea molar content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Alkali resistance of a casein‐acrylonitrile graft copolymer fiber
Authors: Tang Ren‐Cheng , Mei Jie 
Published: July 2008

AbstractThe casein‐acrylonitrile graft copolymer fiber was treated in sodium hydroxide, sodium carbonate, and sodium bicarbonate solutions to evaluate its alkali resistance which was very important for wet processing. The weight loss and whiteness of the treated fibers were examined. UV spectra of the alkaline treatment solutions and IR spectra of the treated fibers were analyzed. The study showed that the fiber exhibited poor alkali resistance. Treating temperature, alkali concentration, and strength affected the weight loss and whiteness of the treated fibers. A high weight loss was found even at low alkali concentration, and the obvious yellowing was observed at higher alkali concentration and temperature. The weight loss was primarily due to the hydrolysis of casein, whereas the yellowing was caused by the hydrolysis of nitrile groups and induced formation of CN conjugated system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis of morphologically different, metal absorbing aniline‐formaldehyde polymers including micron‐sized sphere using simple alcohols as morphology modifier
Authors: Koner Rik Rani , Albino Kumar Potsangbam , Chakraborty Saswati , Ray Manabendra 
Published: July 2008

AbstractAniline‐formaldehyde condensate (AFC) is an amine functional group containing polymer. The sticky resinous nature of the polymer limits its usefulness. Synthesis of AFC in presence of methanol, isopropanol, t‐butanol, n‐octanol or glycerine formed solid cakes instead of resinous material. The scanning electron microscopic (SEM) picture of the polymer synthesized in presence of t‐butanol shows the formation of micron sized spheroids while the presence of methanol, isopropanol, n‐octanol and glycerine leads to amorphous polymer. The polymers were characterized with IR, MALDI‐TOF mass and Energy Dispersive X‐ray (EDAX) analysis. To probe the accessibility of the amine functional groups by external reagents and as an application, metal removal property of the polymers were tested using aqueous Cr(VI) solution. All the polymers remove Cr(VI) efficiently at pH 3 with extent of metal removal depends on their morphology. Polymer synthesized in presence of isopropanol removes ∼ 66% Cr(VI) removal from an initial concentration of 9 mg/L. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Biogenic amine levels change in the brains of stressed honeybees
Authors: Chen Yi‐Ling , Hung Yu‐Shan , Yang En‐Cheng 
Published: July 2008

AbstractThree different stress treatments, CO2 anesthesia, chilling anesthesia, and vertical spin, were applied to test whether honeybee (Apis mellifera) workers express stress responses in rewarding behaviors. In the present work, we defined the rewarding behaviors as the bees flying between the hive and feeder. The results from behavioral observation show that the flight time interval of the rewarding behavior of bee workers, flying between hive and feeder, was longer when they were stressed, suggesting that the stress treatments affected the workers' rewarding behavior. The biogenic amine levels in the workers' brains were measured to examine the rapid biochemical brain response to the stressors. After the chilling anesthesia, the dopamine (DA) and octopamine (OA) levels were significantly decreased; with the CO2 anesthesia for durations of both 2 min and 4 min, only DA showed a significant decrease. In the non‐anesthesia treatments, the vertical spin with a velocity of 50 and 60 rpm for 90 s, the DA and OA levels were significantly decreased. Our results suggest that when the bees were under stress, the brain levels of OA and DA were depressed, and this may have caused latency in the rewarding behavior. The serotonin (5‐HT) levels under these stress treatments were not changed. Arch. Insect Biochem. Physiol. 68:241–250, 2008. © 2008 Wiley‐Liss, Inc.
Effects of RH‐5992 on ecdysteroidogenesis of the prothoracic glands during the fourth larval instar of the silkworm, Bombyx mori
Authors: Gu Shi‐Hong , Lin Ju‐Ling , Lin Pei‐Ling , Kou Rong , Smagghe Guy 
Published: July 2008

AbstractStage‐dependent effects of RH‐5992 on ecdysteroidogenesis of the prothoracic glands during the fourth larval instar of the silkworm, Bombyx mori, were studied in the present report. When larvae were treated with RH‐5992 during the early stages of the fourth larval instar (between day 0 and day 1), initially ecdysteroid levels in the hemolymph were inhibited. However, 24 h after RH‐5992 application, ecdysteroid levels were greatly increased as compared with those treated with acetone. The examination of the in vitro prothoracic gland activity upon RH‐5992 application during the early stages of the fourth larval instar confirmed a short‐term inhibitory effect. When RH‐5992 was applied to the later stages of the fourth larval instar, no effects on both hemolymph ecdysteroid levels and prothoracic gland activity were observed. Addition of RH‐5992 to incubation medium strongly inhibited ecdysteroid secretion by the prothoracic glands from the early fourth instar, indicating direct action of RH‐5992 on ecdysteroidogenesis by prothoracic glands. Four hours after application with RH‐5992 on day 1.5, prothoracic glands still showed an activated response to PTTH in both PTTH‐cAMP signaling and the extracellular signal‐regulated kinase (ERK) signaling. Moreover, addition of RH‐5992 to incubation medium did not interfere with the stimulatory effect of the glands to PTTH in ecdysteroidogenesis. These results indicated that both PTTH‐cAMP signaling and PTTH‐ERK signaling may not be involved in short‐term inhibitory regulation by RH‐5992. Arch. Insect Biochem. Physiol. 68:197–205, 2008. © 2008 Wiley‐Liss, Inc.
Total Synthesis and Biological Potential of Psammosilenin A
Authors: Dahiya Rajiv 
Published: July 2008

AbstractThe present work reports the synthesis of a plant‐originated cyclooctapeptide – psammosilenin A 8 by cyclization of linear peptide fragment phe‐pro‐phe‐phe‐ala‐pro‐leu‐pro‐Opfp which was prepared by coupling of tetrapeptide units Boc‐phe‐pro‐phe‐phe‐OH and ala‐pro‐leu‐pro‐OMe followed by proper deprotection of terminal groups and activation of the acid functionality. During synthesis, dicyclohexylcarbodiimide (DCC) and N,N‐diisopropylcarbodiimide (DIPC) were used as the coupling agents and N‐methylmorpholine (NMM)/triethylamine (TEA) were used as bases. Structure of the synthesized peptide was elucidated by spectral as well as elemental data. The newly synthesized peptide was subjected to biological screening and found to possess potent cytotoxic activity against DLA and EAC cell lines with IC50 value of 7.93 and 17.06 μM, respectively. Furthermore, good anthelmintic activity against earthworms M. konkanensis and Eudrilus species at 1 and 2 mg/mL was also observed for the synthesized cyclic peptide. Studies indicated that N‐methylmorpholine was a more useful base for cyclization of linear peptide unit in comparison to pyridine.
Synthesis and In‐Vitro Antibacterial Activity of 5‐Substituted 1‐Methyl‐4‐nitro‐1H‐imidazoles
Authors: Letafat Bahram , Emami Saeed , Aliabadi Alireza , Mohammadhosseini Negar , Moshafi Mohammad Hassan , Asadipour Ali , Shafiee Abbas , Foroumadi Alireza 
Published: July 2008

AbstractA series of 5‐substituted 1‐methyl‐4‐nitro‐1H‐imidazole derivatives were synthesized and evaluated for in‐vitro antibacterial activity against a panel of microorganisms including Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, Esherichia coli, Klebsiella pneumonia, Entrobacter aerogenes, and Helicobacter pylori using conventional agar dilution method. Among the test compounds, 1‐methyl‐4‐nitro‐5‐(phenylsulfonyl)‐1H‐imidazole was the most potent against Gram‐positive bacteria, with a MIC value of ⪇8 μg/mL. All compounds showed no significant activity against Gram‐negative bacteria at concentrations ⪇64 μg/mL The MIC values against 15 clinical isolates of H. pylori indicated that compounds 10 and 11 were the most active compounds in this series in terms of inhibiting the growth of H. pylori (MIC = 2 μg/mL). It was also demonstrated that their corresponding activities were four times larger than that of metronidazole.
Synthesis and Evaluation of the Luciferase‐Oligodeoxynucleotide for the Sequence‐Selective Detection of Nucleic Acids
Authors: Nagatsugi Fumi , Nakahara Ryusuke , Inoue Kaori , Sasaki Shigeki 
Published: July 2008

AbstractA new method for the synthesis of ODN‐luciferase conjugate was investigated as a signal‐amplifying sensor of the target nucleic acids. The conjugation of the luciferase was successfully achieved between the cysteine residue and the 2‐amino‐6‐vinylpurine nucleoside of the ODN probe without significant inactivation of luciferase. The ODN‐luciferase conjugate modified with PEG retained the luciferase activity and selectivity during the hybridization with the target ODN.
Synthesis of Nitroxyl Radicals for Overhauser‐enhanced Magnetic Resonance Imaging
Authors: Yamada Ken‐ichi , Kinoshita Yuichi , Yamasaki Toshihide , Sadasue Hiromi , Mito Fumiya , Nagai Mika , Matsumoto Shingo , Aso Mariko , Suemune Hiroshi , Sakai Kiyoshi , Utsumi Hideo 
Published: July 2008

AbstractNon‐invasive measurement and visualization of free radicals in vivo would be important to clarify their roles in the pathogenesis of free radical‐associated diseases. Nitroxyl radicals can react with free radicals and be derivatized to achieve specific cellular / subcellular localizing capabilities while retaining the simple spectral features useful in imaging. Overhauser‐enhanced magnetic resonance imaging (OMRI), which is a double resonance technique, creates images of free radical distributions in small animals by enhancing the water proton signal intensity via the Overhauser Effect. In this study, we synthesized various nitroxyl probes having 15N nuclei and deuterium, and measured the enhancement factor for Overhauser‐enhanced magnetic resonance imaging experiments. 15N‐D‐4‐Oxo‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (15N‐D‐oxo‐TEMPO) has the highest enhancement factor compared with other nitroxyl probes. The proton signal enhancement was higher for 15N‐labeled nitroxyl probes when compared to the 14N‐labeled analogues because of the reduced spectral multiplicity of the I = 1/2 nucleus. Furthermore, this enhancement is proportional to the line width and number of electron spin resonance lines of nitroxyl radicals. Finally, we compared the Overhauser‐enhanced magnetic resonance image of 15N‐labeled, deuterated 4‐Oxo‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl with that of 14N‐H‐TEMPOL. These results suggested that the selective deuteration of the nitroxyl probes enhanced the signal‐to‐noise ratio and thereby improved spatial and temporal resolutions.