bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetic studies on curing of hydroxy‐terminated polybutadiene prepolymer‐based polyurethane networks
Authors: Singh Manohar , Kanungo B. K. , Bansal T. K.
Published: August 2002

Hydroxy‐terminated polybutadiene (HTPB) prepolymer prepared by free‐radical mechanism at Chemical Engineering Complex, Vikram Sarabhai Space Center, Thiruvananthapuram was reacted with toluene diisocyanate (TDI), a curative at varying stoichiometric ratios (r = [NCO]/ [OH]) equal to 0.7, 0.8, 0.9, 1.0, and 1.1 at a constant temperature of 70°C. The increased rate of viscosity of polyurethane networks formed was used to calculate the rate constant. Similarly, the rate of change of viscosity of curing networks at different r values (0.7–1.1) and temperature intervals (30–70°C) was used to calculate activation energy. The results of the curing networks showed that the rate constant at r > 0.9 is constant and the rate of decrease of activation energy is lower at r ≤ 1; thereafter, it becomes quite significant. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 842–846, 2002
Influence of ethylene‐co‐vinyl acetate copolymers on the flow properties of wax synthetic systems
Authors: Machado André L. C. , Lucas Elizabete F.
Published: August 2002

Wax crystallization can cause serious damage to petroleum flow because as the viscosity increases, there is organic deposition in the pipe lines, which causes oil production reduction. Ethylene–vinyl acetate copolymers (EVA) are used as an alternative to prevent such problems. The influence of EVA copolymers on the properties of wax synthetic systems, composed of a solvent mixture and paraffin and petroleum asphalt residue (PAR), was evaluated in this work. The performance of EVA as a wax inhibitor depends on the molecular weight and vinyl acetate content of the copolymer and on the presence of the asphalt fraction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1337–1348, 2002
A study on nanofiber‐reinforced thermoplastic composites (II): Investigation of the mixing rheology and conduction properties
Authors: Lozano K. , Bonilla‐Rios J. , Barrera E. V.
Published: August 2002

This article is portion of a comprehensive study on the development of nanofiber‐reinforced polymer composites for electrostatic discharge materials and structural composites. Vapor‐grown carbon fibers with an average diameter of 100 nm were used as a precursor and model fiber system for carbon nanotubes. These nanofibers were purified and functionalized to provide for an open network of high‐purity nanofibers. Banbury‐type mixing was used to disperse the nanofibers in the polymer matrix. Rheological and microscopic analysis showed that the high shear processing of the polymer/nanofiber mixture led to a homogeneous dispersion of nanofibers with no agglomerates present and no shortening of the nanofibers. The shear thinning behavior of polymeric materials helps in the mixing of the nanofibers to form the composites. A percolation threshold for electrical conduction of 9–18 wt % was observed for the highly dispersed nanofiber networks. The electrical behavior of these materials was not affected by changes in humidity. Microscopic analysis showed highly dispersed nanofibers with no indications of porosity. These conducting polymers are well suited for electrostatic discharge applications, and might well become multifunctional materials for strength/electrical applications. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1162–1172, 2001
Effects of various kinds of fillers on the tribological behavior of polytetrafluoroethylene composites under dry and oil‐lubricated conditions
Authors: Zhang Zhao‐Zhu , Liu Wei‐Min , Xue Qun‐Ji
Published: August 2002

Polytetrafluoroethylene (PTFE)‐based composites filled with various inorganic fillers in a volume fraction of 30% were prepared. The tribological behavior of the PTFE composites sliding against AISI52100 steel under dry and liquid paraffin‐lubricated conditions was investigated on an MHK‐500 model ring‐on‐block test rig. The morphologies of worn surfaces and wear debris were observed with a scanning electron microscope (SEM) and an optical microscope. As the results, different fillers show different effects on the tribological behavior of the PTFE composites, while the composite shows much different tribological behavior under lubricated conditions as compared with dry sliding. The tribological behavior of the PTFE composites under dry sliding is greatly related to the uniformity and thickness of the transfer films. Only the PTFE composites with a transfer film of good uniformity and proper thickness may have excellent tribological behavior. The PTFE composites show much better tribological behavior under lubrication of liquid paraffin than under dry sliding, namely, the friction coefficients are decreased by 1 order of magnitude and the wear rate by 1–3 orders of magnitude. Observation of the worn composite surfaces with SEM indicates that fatigue cracks were generated under lubrication of liquid paraffin, owing to the absorption and osmosis of liquid paraffin into the microdefects of the PTFE composites. The creation and development of the fatigue cracks led to fatigue wear of the PTFE composites. This would reduce the mechanical strength and load‐supporting capacity of the PTFE composites. Therefore, the tribological behavior of the PTFE composites under lubrication of liquid paraffin is greatly dependent on the compatibility between the PTFE matrix and the inorganic fillers. In other words, the better is the compatibility between PTFE and fillers the better is the tribological behavior of the composites. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1891–1897, 2001
Examination of selected synthesis parameters for wood adhesive‐type urea–formaldehyde resins by 13C NMR spectroscopy. III
Authors: Kim Moon G.
Published: August 2002

The varying polymer structures of wood adhesive‐type urea–formaldehyde resins resulting from different formaldehyde/first urea (F/U1) mole ratios used in the first step of resin manufacture were investigated using 13C. As the F/U1 mole ratio decreased progressively from 2.40 to 2.10 and to 1.80, the viscosity increase due to polymerization during resin synthesis became faster and resulted in decreasing side‐chain branches and increasing free urea amide groups in the resin structure. The resultant UF resins, with the second urea added to an overall F/(U1 + U2) of 1.15, showed viscosity decreases when heated with stirring or allowed to stand at room temperature that were also characteristic with the F/U1 mole ratios used in resin synthesis. The formaldehyde emission levels of particleboards bonded with the freshly made UF resins showed relatively small but similarly characteristic variations. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2800–2814, 2001
Fluidized‐bed reactor modeling for polyethylene production
Authors: Fernandes Fabiano André Narciso , Ferrareso Lona Liliane Maria
Published: August 2002

Gas‐phase technology for polyethylene production has been widely used by industries around the world. A good model for the reactor fluid dynamics is essential to properly set the operating conditions of the fluidized‐bed reactor. The fluidized‐bed model developed in this work is based on a steady‐state model, incorporating interactions between separate bubble, emulsion gas phase, and emulsion solid polymer particles. The model is capable not only of computing temperature and concentration gradients for bubble and emulsion phases, calculating polymer particle mean diameter throughout the bed and polyethylene production rate, but also of pinpointing the appearance of hot spots and polymer meltdown. The model differs from conventional well‐mixed fluidized‐bed models by assuming that the particles segregate within the bed according to size and weight differences. The model was validated using literature and patent data, presenting good representation of the behavior of the fluidized‐bed reactor used in ethylene polymerization. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 321–332, 2001
Processing and compressive strengths of syntactic foams with and without fibrous reinforcements
Authors: Karthikeyan C. S. , Sankaran S. , Jagdish Kumar M. N. , Kishore
Published: August 2002

Syntactic foam composites containing 0, 0.9, 1.76, 2.54, 3.54, and 4.5 vol % of E‐glass fibers in the form of chopped strands were fabricated and subjected to compression testing. It was found that the compressive strength values generally increased with fiber content except for the 3.54% fiber‐bearing cast slab, which recorded lower values. This lone exception was due to the difference in processing route adopted in fabricating this particular fiber‐bearing foam. Also noticed was the fact that the compressive strength of the 0.9 vol % fiber‐bearing system was lower compared to the fiber‐free system. This was correlated to the higher level of void content noticed with this fiber‐bearing foam compared to that seen in the unreinforced foam. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 405–411, 2001
Yielding of commercial poly(vinyl chloride) pipe material
Authors: Ragab A. R. , Mahmoud M. A. , Khorshied S. A.
Published: August 2002

Tubular test specimens of commercial poly(vinyl chloride) pipe material were tested in biaxial stress systems covering the four quadrants of the plane–stress space. The test rig provided yield stresses at a constant temperature and controlled strain rate tension, compression, internal pressure, external pressure, and torsion combined loading. The experimental yield points fit the von Mises yield criterion. This result was confirmed by the ratio of compressive to tensile yield stresses; being unity, the density remaining constant with the applied hydrostatic stress, and, finally, the normality of the strain vector to the yield locus at the corresponding stressing point. Subsequent yielding loci of previously deformed specimens deviated largely from the von Mises locus. This deviation may have been caused by craze–void interaction. Finally, the viscous behavior, the dependence of yield stresses on the strain rate and temperature, is represented with a generalized phenomenological model based on an Eyring–Ward‐type expression. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 991–999, 2001
Kinetic crystallization of polypropylene in ternary composites based on fiber‐reinforced PP‐EPDM blends
Authors: López Manchado Miguel A. , Torre Luigi , Kenny José M.
Published: August 2002

The crystallization of isotactic polypropylene (iPP) in its blends with ethylene–propylene–diene terpolymer (EPDM), reinforced with different fibers, is described in this work. In particular, the effects of both the fibers and the EPDM on the crystallization kinetics and morphology of iPP are analyzed. The study was performed using differential scanning calorimetry (DSC) in dynamic and isothermal conditions and optical microscopy. It was found that all the fibers act as effective nucleant agents on iPP crystallization independently of the blend composition. The results obtained highlight the accelerating effect of the fibers and of the EPDM on the PP crystallization up to a certain EPDM percentage. The halftime of crystallization, τ1/2, and the overall crystallization rate, Kn, increase in the presence of all the fibers analyzed, showed the aramidic ones the most effective. The isothermal crystallization kinetics of ternary composites based on PP–EPDM blend matrices reinforced with different types of fibers can be modeled using the Avrami equation. On the other hand, the kinetic curves obtained under nonisothermal conditions provide a further confirmation of the nucleating action of the fibers on the PP crystallization. Optical polarizing microscopy was also used to investigate the effect of EPDM on the spherulite growth and the transcrystallinity phenomenon on the surface of the fibers. The results of such analysis showed that the transcrystallinity phenomenon is hindered at high rubber percentages. As in the case of the rate of crystallization, the highest proportion of transcrystallinity was observed in the presence of the aramidic fibers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1063–1074, 2001
Synthesis and swelling characteristics of acid‐containing poly(vinyl alcohol) hydrogels
Authors: Ruiz J. , Mantecón A. , Cádiz V.
Published: August 2002

Poly(vinyl alcohol) (PVA) was modified with phthalic and succinic anhydrides to produce vinyl alcohol‐vinyl ester copolymers that contain free carboxylic acid or carboxylate groups. These half‐esters were then crosslinked using the diglycidylether of 1,4‐butanediol. Low crosslinker/carboxylic acid ratios were used to obtain low degrees of crosslinking, so that the capacity to absorb water of the resulting hydrogel was high. Water absorption was determined gravimetrically as a function of time at room temperature. The swelling behavior was significantly different in both ionic and nonionic polymers. The water uptake of the former was high enough for products to be considered superabsorbents. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1444–1450, 2001
Synthesis and swelling properties of 2‐hydroxyethyl methacrylate‐co‐1‐vinyl‐3‐(3‐sulfopropyl)imidazolium betaine hydrogels
Authors: Lee Wen‐Fu , Chen Ying‐Jou
Published: August 2002

A series of 2‐hydroxyethyl methacrylate/1‐vinyl‐3‐(3‐sulfopropyl)imidazolium betaine (HEMA/VSIB) copolymeric gels were prepared from various molar ratios of HEMA and the zwitterionic monomer VSIB. The influence of the amount of VSIB in copolymeric gels on their swelling behavior in water and various saline solutions at different temperatures and the drug‐release behavior, compression strength, and crosslinking density were investigated. Experimental results indicated that the PHEMA hydrogel and the lower VSIB content (3%) in the HEMA/VSIB gel exhibited an overshooting phenomenon in their dynamic swelling behavior, and the overshooting ratio decreased with increase of the temperature. In the equilibrium water content, the value increased with increase of the VSIB content in HEMA/VSIB hydrogels. In the saline solution, the water content for these gels was not affected by the ion concentration when the salt concentration was lower than the minimum salt concentration (MSC) of poly(VSIB). When the salt concentration was higher than the MSC of poly(VSIB), the deswelling behavior of the copolymeric gel was more effectively suppressed as more VSIB was added to the copolymeric gels. However, the swelling behavior of gels in KI, KBr, NaClO4, and NaNO3 solutions at a higher concentration would cause an antipolyelectrolyte phenomenon. Besides, the anion effects were larger than were the cation effects in the presence of a common anion (Cl−) with different cations and a common cation (K+) with different anions for the hydrogel. In drug‐release behavior, the addition of VSIB increased the drug‐release ratio and the release rate. Finally, the addition of VSIB in the hydrogel improved the gel strength and crosslinking density of the gel. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2888–2900, 2001
The effect of temperature on physical aging of glassy polymers
Authors: Drozdov Aleksey D.
Published: August 2002

Constitutive equations are derived for the linear viscoelastic response of amorphous glassy polymers subjected to physical aging. Stress–strain relations are applied to fit experimental data for poly(methyl methacrylate), poly(styrene‐co‐acronitrile), and poly(vinyl acetate) in tensile relaxation tests and in torsional dynamic tests at various temperatures. Fair agreement is demonstrated between observations and results of numerical simulation. It is revealed that an increase in the annealing temperature results in an increase in the rate of relaxation and a decrease in the apparent rate of structural recovery. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3309–3320, 2001
Morphology and mechanical properties of interpenetrating polymer networks of poly(allyl diglycol carbonate) and rigid polyurethane
Authors: Dadbin Susan , Chaplin R. P.
Published: August 2002

Novel simultaneous interpenetrating polymer networks (SINs) of poly(allyl diglycol carbonate) (ADC) and a rigid high modulus polyurethane based on the Conathane UC‐33 prepolymer system (UC) were synthesized. The completion of each component reaction was verified by means of Fourier transform IR spectroscopy. The effects of the composition on the morphology, mechanical properties, and thermal transition behavior of the SINs were studied. At 10% composition, transmission electron microscopy revealed complete phase miscibility. This was also supported by the high optical transparency of the sample. As the UC content increased to 20% a two‐phase morphology was observed in which the UC phase domains were dispersed in the matrix of the ADC phase. At higher UC content the ADC continuous phase was replaced by the UC phase, implying the occurrence of phase inversion. This variation of morphology allowed the SINs to have a property range from the UC‐toughened plastics to the ADC‐reinforced polyurethane. The SINs containing 50% UC showed synergism in the mechanical properties as the elongation was significantly increased to 4 times that of the unmodified UC and ADC homopolymers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3361–3370, 2001
The effect of addition of different elastomers upon the crystalline nature of PP
Authors: Da Silva Ana Lúcia N. , Rocha Marisa C. G. , Lopes Léa , Chagas Beatriz S. , Coutinho Fernanda M. B.
Published: August 2002

Thermal and morphological studies have been performed on polymer blends based on ethylene–octene copolymer (PEE)/PP and ethylene–propylene–diene copolymer (EPDM)/PP. The thermal and morphological behavior of PEE, EPDM, PEE/PP, and EPDM/PP systems were analyzed by differential scanning calorimetry (DSC) and polarizing light microscopy, respectively. It was observed that the behaviors of crystallization kinetics of PEE/PP and EPDM/PP blends were similar. It was also observed that addition up to 10–20% (w/w) of elastomers resulted in increasing of spherulite size. The heat of fusion (ΔHf) and crystallinity degree of PEE/PP and EPDM/PP systems decreased when the elastomer contents were increased. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3530–3537, 2001
Molecular interactions in poly(methacrylic acid)/poly(N‐isopropyl acrylamide) interpenetrating polymer networks
Authors: Zhang Jing , Peppas Nicholas A.
Published: August 2002

The molecular interactions between the component networks in poly(methacrylic acid)/poly(N‐isopropyl acrylamide) (PMAA/PNIPAAm) interpenetrating polymer networks (IPNs) were investigated using attenuated total reflectance (ATR)‐Fourier transform IR (FTIR) spectroscopy. Hydrogen‐bond formation was noted between the carboxyl groups of PMAA and the amide groups of PNIPAAm. The ATR‐FTIR results showed shifts in the carboxylic and amide groups, indicating the existence of hydrogen bonding between these two individual networks within the IPNs. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1077–1082, 2001
Studies on the synthesis and properties of hydroxyl azacrown ether‐grafted chitosan
Authors: Yang Zhikuan , Yuan Yang
Published: August 2002

The chitosan hydroxyl azacrown ether was synthesized by reaction of hydroxyl azacrown ether with epoxy‐activated chitosan. The C2 amino group in chitosan was protected from the reaction between benzaldehyde and chitosan to form N‐benzylidene chitosan. After reaction with epichlorohydrin and azacrown ether, reacting O‐aryl mesocyclic diamine‐N‐benzylidene chitosan and dilute ethanol hydrochloride solution to obtain novel chitosan‐azacrown ether bearing hydroxyl removed the Schiff base. Its structure was confirmed with elemental analysis, FTIR spectra analysis, X‐ray diffraction analysis, and solid‐state 13C NMR analysis. Its static adsorption properties for Ag(I), Cd(II), Pb(II), and Cr(III) were also investigated. The experimental results showed that the hydroxyl azacrown ether grafted chitosan has good adsorption capacity and high selectivity for Ag(I) in the coexistence of Pb(II) and Cd(II), the selectivity coefficients of hydroxyl azacrown ether chitosan were KAg(I)/Pb(II) = 32.34; KAg(I)/Cd(II) = 56.12. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1838–1843, 2001
Study on molecular interaction behavior, and thermal and mechanical properties of polyacrylic acid and lactose blends
Authors: Fan Xiao‐Dong , Hsieh You‐Lo , Krochta John M. , Kurth Mark J.
Published: August 2002

Polyacrylic acid (PAA) blending with lactose or polyol, a lactose derivative, is investigated by Fourier transform infrared, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and stress–strain tests. The IR spectra of PAA/lactose blends exist shifting around 1700 cm and 3400 cm−1, implying intermolecular hydrogen‐bonding interaction between two compounds. DSC data show that PAA and lactose are miscible below 17% lactose. At the higher content of lactose, phase separation occurs due to lactose self‐association. Comparing to PAA/lactose blends, PAA/ polyol systems show much weaker hydrogen‐bonding interaction effect. All blending systems studied exhibit extensive reduction in their thermal and mechanical properties. The result suggests that both lactose and polyol cannot be used as effective additives to enhance the physical properties of PAA. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1921–1927, 2001
Morphology and mechanical properties of pullulan/poly(vinyl alcohol) blends crosslinked with glyoxal
Authors: Teramoto Naozumi , Saitoh Masahiko , Kuroiwa Johta , Shibata Mitsuhiro , Yosomiya Ryutoku
Published: August 2002

We prepared pullulan/poly(vinyl alcohol) (PVA) blend films by casting the polymer solution in dimethyl sulfoxide. Their morphology and mechanical properties were investigated. Scanning electron micrographs revealed that the pullulan was immiscible with PVA over the entire composition range. The tensile strength and modulus of the blend films were lower than those predicted by the upper bound composite equation. To improve the mechanical properties, we investigated the reaction of the 40/60 blend with glyoxal. The infrared spectral change and the increase in the glass‐transition temperature (corresponding to the PVA component) accompanying the reaction indicated that crosslinking with glyoxal had proceeded. The crosslinked films were homogeneous and had higher tensile strengths and moduli than the simple blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2273–2280, 2001
Phase‐separation prevention and performance improvement of poly(vinyl acetate)/TEOS hybrid using modified sol‐gel process
Authors: Jang Jyongsik , Bae Joonwon , Kang Doohwan
Published: August 2002

The formation of covalent bonds between silanols in copolymer and those in silica prevents organic–inorganic phase separation. Two series of hybrid composite materials, poly(vinyl acetate‐co‐vinyl trimethoxysilane)/TEOS and poly[vinyl acetate‐co‐3‐(trimethoxysilyl)propyl methacrylate]/TEOS, were fabricated using a modified sol‐gel process. The hybrids were transparent. Two kinds of silane coupling agents, vinyl trimethoxysilane (VTS) and 3‐(trimethoxysilyl)propyl methacrylate (γ‐MPS), were used to prevent macrophase separation through formation of covalent bonds. Thermal analysis showed that γ‐MPS was more effective than VTS for the formation of covalent bonds. Enhancement of thermal stability of the hybrids was investigated by thermogravimetric analysis. Photomicrographs of scanning electron microscopy and images of atomic force microscopy indicated that inorganic silica particles were homogeneously dispersed in less than 50 nm in organic matrix. The morphological properties of hybrids were strongly dependent on the organic–inorganic composition. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2310–2318, 2001
Chemical, chromatographic, and thermal analysis of rosemary (Rosmarinus officinalis)
Authors: Kaloustian J. , Portugal H. , Pauli A. M. , Pastor J.
Published: August 2002

Rosemary (Rosmarinus officinalis) is mainly known for its cooking qualities, but it possesses an essential oil with pharmacological properties. Moreover, this plant was the start of forest fires in Provence, France. The presence of biopolymers can contribute to electrical energy production by biomass combustion. The aim of this work was to study a stalk of rosemary during its biological cycle (November 1998 to June 1999). The chemical analysis (water, mineral ashes, cellulose, lignin, holocellulose, and extractives) showed few variations during this period. Leaves and branches differentiated themselves according to their chemical composition. Analyzed by chromatography gas–liquid chromatography/mass spectroscopy (GC‐MS) and gas–liquid chromatography/flam ionization detector (GC‐FID), the essential oil of this rosemary had a high level of camphor (30–45%), which could be used in new therapeutics (cardiac and respiratory analeptic). Finally, the simultaneous thermal analysis (DTA‐TG) was run on the fresh plants and the dried powdered samples. Several kinetic constants of the biopolymers had been computed: activation energies of cellulose and holocellulose. During heating, the rosemary's lignin decomposed more than others plants, thereby increasing the fire risks. The chemical, chromatographic, and thermal analysis run on the rosemary could be applied on other species in the Mediterranean basin. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 747–756, 2002
Simultaneous SAXS and WAXS investigations of changes in native cellulose fiber microstructure on swelling in aqueous sodium hydroxide
Authors: Crawshaw J. , Bras W. , Mant G. R. , Cameron R. E.
Published: August 2002

Simultaneous small‐ and wide‐angle X‐ray scattering was used to follow changes in the microstructure of native cellulose (cellulose I) fibers during conversion to sodium cellulose I (Na‐cellulose I) by aqueous sodium hydroxide. Wide‐angle X‐ray scattering was used to monitor the extent of conversion, while small‐angle X‐ray scattering was used to explore what occurs at the higher structural levels of the elementary fibrils, microfibrils, and interfibrillar voids. Native cellulose fibers, swollen in either water or aqueous sodium hydroxide, exhibited an increase in the void volume fraction and a decrease in the void cross‐section size, as the swelling agent separated elementary fibrils, opening up the structure, and creating many small voids. After conversion of swollen native cellulose to sodium cellulose I, the void volume fraction and average void cross‐section dimensions both increased. During conversion from dry cellulose I fibers to swollen Na‐cellulose I fibers, the void cross‐section dimensions went through a minimum, suggesting that the void structure may go via an intermediate similar to the water swollen structure of cellulose I. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1209–1218, 2002
Properties of high‐temperature drilling fluids incorporating disodium itaconate/acrylamide/sodium 2‐acrylamido‐2‐methylpropanesulfonate terpolymers as fluid‐loss reducers
Authors: Wu Y. M. , Sun D. J. , Zhang B. Q. , Zhang Ch. G.
Published: August 2002

The terpolymer of disodium itaconate (DIA), acrylamide (AM) and sodium 2‐acrylamido‐2‐methyl‐1‐propane sulfonate (SAMPS) was synthesized through free‐radical polymerization, and characterized using FTIR and TGA methods. The IR spectra of DIA‐AM‐SAMPS terpolymer confirmed that there was no olefinic band at 1635–1620 cm−1, while the TGA results revealed that the terpolymer was of higher thermal stability than the SAMPS homopolymer. The filtrate volume reduced with increase of the terpolymer concentration before or after the aging test. The rheology properties of both fresh‐water mud and salt‐water mud were improved by DIA‐AM‐SAMPS terpolymer, and apparent viscosity (ηa); plastic viscosity (ηb) and yield point (τ0) of salt‐water mud reached the smallest values at 1.2% of the terpolymer concentration after the aging test. The particle size data demonstrated that only a small change of the clay particle size occurred before and after the aging test at 220°C. This further confirmed the thermal stability of the terpolymer–clay dispersion from another point of view. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3068–3075, 2002; DOI 10.1002/app.2335
Ecoregional planning in marine environments: identifying priority sites for conservation in the northern Gulf of Mexico
Authors: Beck Michael W. , Odaya Mami
Published: August 2002

1. The overall aim of this work was to identify sites within the northern Gulf of Mexico that, if protected, would fully represent the biological diversity of the nearshore waters of this ecoregion. In this paper, we focus on the eastern subregion, northwest Florida, to illustrate the process of ecoregional planning in marine environments.

2. The basic steps in ecoregional planning include: identification of conservation targets, i.e. species and habitats; collection of data on their ecology and distribution; determination of conservation goals for the amount of targets that must be protected; and identification of a set of sites that meets these goals for all targets.

3. As a preliminary goal, it was determined that the set of priority sites should contain at least 20% of the current distribution of each target habitat and species.

4. Two primary tools were used to choose a set of priority sites: a reserve selection program, SITES, and interviews and a workshop with scientists and managers. The final set of priority sites integrated information from these various sources.

5. The goals were exceeded for all conservation targets in the priority sites. On average, 75 and 58% of the distributions of the habitat targets were contained within the priority and high priority sites, respectively. These priority and high priority sites only occupied 29 and 17% of the study area, respectively.

6. One of the first steps in the conservation of the bays identified as priority sites is the recognition that they are integrally linked by important processes to the surrounding terrestrial and aquatic environments. Conservation in a part of these estuarine landscapes will benefit biodiversity across environments. Copyright © 2001 John Wiley & Sons, Ltd.
Differential expression of multiple genes during articular chondrocyte redifferentiation
Authors: Haudenschild Dominik R. , McPherson John M. , Tubo Ross , Binette François
Published: August 2002

Articular chondrocytes undergo a rapid change in phenotype and gene expression, termed dedifferentiation, when isolated from cartilage tissue and cultured on tissue culture plastic. On the other hand, “redifferentiation” of articular chondrocytes in suspension culture is characterized by decreased cellular proliferation and the reinitiation of synthesis of hyaline articular cartilage extracellular matrix molecules. The molecular triggers for these events have yet to be defined. Subtracted cDNA libraries representing genes involved in the early events of adult human articular chondrocyte redifferentiation were generated from human articular chondrocytes that were first cultured in monolayer, and subsequently transferred to suspension culture at 106 cells/ml for redifferentiation. Differential regulation of genes involved in cellular organization, nuclear structure, cellular growth regulation, and extracellular matrix deposition and remodeling were observed within 48 hr of this transfer. Many of these genes had not been previously identified in the chondrocyte differentiation pathway and a number of the isolated cDNAs did not have homologies to sequences in the public data banks. Genes involved in IL‐6 signal transduction including acute phase response factor (APRF), Mn superoxide dismutase, and IL‐6 itself were up‐regulated in suspension culture. Membrane glycoprotein gp130, a component of the IL‐6 receptor, was down‐regulated. Other genes involved in cell polarity, cell adherence, apoptosis, and possibly TGF‐beta signaling were differentially regulated. The differential regulation of the cytokine connective tissue growth factor (CTGF) during the early stages of articular chondrocyte redifferentiation, decreasing within 48 hours of transfer to suspension culture, was particularly interesting given its reported role in the stimulation of cellular proliferation. CTGF was highly expressed in proliferative monolayer culture, and then greatly reduced by redifferentiation in standard high‐density suspension culture. When articular chondrocytes were seeded in suspension at low‐density (104 cells/ml), however, high levels of CTGF were observed along with increased levels of mature articular cartilage extracellular matrix protein RNAs, such as type II collagen and aggrecan. Although the role of CTGF in articular cartilage biology remains to be elucidated, the results described here demonstrate the potential utility of subtractive hybridization in understanding the process of articular chondrocyte redifferentiation. Anat Rec 263:91–98, 2001. © 2001 Wiley‐Liss, Inc.
Effects of hypocholesterolaemic agents on the expression and activity of 3‐hydroxy‐3‐methylglutaryl‐CoA reductase in the fat body of the German cockroach
Authors: Zapata Rafael , Martín David , Piulachs Maria‐Dolors , Bellés Xavier
Published: August 2002

In the fat body of adult Blattella germanica females, the expression of 3‐hydroxy‐3‐methylglutaryl‐CoA reductase (HMG‐CoA reductase) during the first reproductive cycle is parallel to that of vitellogenin, suggesting a functional link between the mevalonate pathway, and vitellogenesis and reproduction. We have studied the effects of compactin and fluvastatin, two inhibitors of HMG‐CoA reductase, on the expression and activity of the enzyme in the fat body, and on the ootheca formation, ootheca viability, and number of larvae per viable ootheca. Short‐term assays showed that both compounds reduce the protein levels and enzymatic activity of HMG‐CoA reductase, and long‐term experiments revealed that fluvastatin impairs embryo development. Arch. Insect Biochem. Physiol. 49:177–186, 2002. © 2002 Wiley‐Liss, Inc.
Hydrogen peroxide detoxification in the midgut of the blood‐sucking insect, Rhodnius prolixus
Authors: Paes Marcia Cristina , Oliveira Mariana Borges , Oliveira Pedro L.
Published: August 2002

Here we investigated H2O2 production and detoxification in the hematophagous hemiptera, Rhodnius prolixus. Superoxide dismutase (SOD) catalyzes the dismutation of superoxide radical (O2–). This reaction produces hydrogen peroxide, which is scavenged by antioxidant enzymes such as catalase (CAT). SOD and CAT activities were found in all tissues studied, being highest in the midgut. CAT was dose‐dependently inhibited in vivo by injections of 3‐amino‐1,2,4‐triazole (AT). Insects treated with AT showed a twofold increase in H2O2 levels. Injection of DL‐buthionine‐[S, R]‐sulfoximine (BSO), an inhibitor of glutathione synthesis, also resulted in a fourfold increase in H2O2, together with stimulation of CAT activity. Simultaneous administration of both AT and BSO had a synergistic effect on midgut H2O2 content. Taken all together, our results suggest that CAT and glutathione‐dependent mechanisms cooperate to control H2O2 concentration in the midgut cell and prevent hydroxyl radical generation by Fenton reaction in this tissue. Arch. Insect Biochem. Physiol. 48:63–71, 2001. © 2001 Wiley‐Liss, Inc.
Developmental variation in cytochrome P450 expression in Papilio polyxenes in response to xanthotoxin, a hostplant allelochemical
Authors: Harrison Terry L. , Zangerl Arthur R. , Schuler Mary A. , Berenbaum May R.
Published: August 2002

Although developmental variation in activity and inducibility is typical of cytochrome P450 monooxygenases (P450s) in insects, the adaptive significance of such variation is often unclear, in part because the natural function of insect P450s is rarely known. In this study, we examined developmental variation in expression of CYP6B1 and CYP6B3 in Papilio polyxenes, the black swallowtail. Enzymes encoded by these genes have been implicated in the metabolism of xanthotoxin, a furanocoumarin characteristic of the apiaceous hostplants of P. polyxenes. In each life stage—egg, five larval instars, pupa, and adult—we examined individuals exposed to foliage with and without supplemental xanthotoxin. For each stage, we conducted enzyme assays to estimate xanthotoxin metabolism, Northern analysis to detect constitutive and induced mRNA levels, and RT‐PCR amplification and Southern analysis to differentiate among P450 genes expressed. Inducible xanthotoxin metabolism, previously reported in fifth instars, was observed in four of five larval stages but was absent or undetectable in all stages that do not feed on foliage; the highest levels of activity were in early larval instars. The same pattern was observed in both Northern and RT‐PCR gel blot analyses. In inducible larval stages, inducibility of CYP6B1 transcripts by xanthotoxin was greater than the inducibility of CYP6B3 transcripts. These findings support earlier suggestions that these two P450s contribute to xanthotoxin metabolism in this species and that expression of these P450 genes is regulated in an adaptive fashion with respect to probability of exposure to hostplant toxins over the course of development. Arch. Insect Biochem. Physiol. 48:179–189, 2001. © 2001 Wiley‐Liss, Inc.
The role of biomechanical factors and HLA‐B27 in magnetic resonance imaging‐determined bone changes in plantar fascia enthesopathy
Authors: McGonagle Dennis , Marzo‐Ortega Helena , O'Connor Philip , Gibbon Wayne , Pease Colin , Reece Richard , Emery Paul
Published: August 2002

Objective

To study the role of biomechanical factors and HLA‐B27 in plantar fasciitis.

Methods

T1‐weighted and T2 spectral presaturation with inversion recovery (fat suppressed) magnetic resonance imaging (MRI) sequences of the plantar fascia insertion and adjacent bone were performed on 28 patients with plantar fasciitis; 17 had spondylarthropathy (SpA)‐associated disease, and 11 had mechanically induced disease. The relationship between the degree of bone edema, scored on a semiquantitative scale (from absent to severe), and the patient's HLA‐B27 status was determined.

Results

On MRI, edema within the soft tissue at the enthesis was evident in both groups. Bone edema in the adjacent calcaneum was evident in 64.7% (11 of 17) of patients with SpA and in 45% (5 of 11) of those with mechanically induced disease (P = 0.441). HLA‐B27 was identified in 9 (53%) of the patients with SpA but in none (0%) of those with mechanically induced disease. All 6 of the SpA patients with extensive bone edema but none of the 5 SpA patients with mild bone edema were HLA‐B27 positive (P = 0.002).

Conclusion

The association of HLA‐B27 with bone pathology in early enthesitis may have implications for a better understanding of the pathogenesis of SpA.
Intranasal absorption of sumatriptan and naratriptan: no evidence of local transfer from the nasal cavities to the brain arterial blood in male rats
Authors: Einer‐Jensen Niels , Larsen Lise , Deprez Stephanie , Starns Elaine , Schwartz Sheila
Published: August 2002

Nasal administration to rats of small molecules (tritiated water, tyrosine, and propanol) results in a higher concentration in the brain arterial blood than in other arteries. The preferential distribution is based on a counter current transfer, which takes place between nasal vein blood and brain arterial blood in the cavernous sinus‐carotid artery complex. This model was used to investigate whether the antimigraine 5HT1B/1D receptor agonists sumatriptan and naratriptan may also be transferred by the system. The ratio of ‘head’:‘heart’ plasma concentrations obtained from two carotid catheters after intranasal administration was not different from 1.00 for either compound, and thus, there was no experimental evidence of a preferential local transfer of drug from the nose to the carotid artery circulation. However, plasma concentrations increased from the first minute after intranasal dosing suggesting that sumatriptan and naratriptan are absorbed into the general systemic circulation from the nasal cavity in rats in a first‐order fashion with no lag time. This is consistent with the clinical onset of efficacy of sumatriptan after an intranasal dose which occurs as early as 15 min post dose. Copyright © 2001 John Wiley & Sons, Ltd.
The effect of enzyme inhibitor and absorption site following [D‐ala2, D‐leu5]enkephalin oral administration in rats
Authors: Lee Hye J. , Amidon Gordon L.
Published: August 2002

The effects of enzyme inhibitor, amastatin, and absorption site following intravenous (i.v.) oral (p.o.), jejunal and ileal administration of [D‐ala2, D‐leu5]enkephalin (YdAGFdL) were investigated in rats. Model dependent and independent pharmacokinetic parameters were obtained and compared. Linear pharmacokinetics of YdAGFdL were evaluated at 0.28 and 500 µg doses for i.v. and at 1, 500, and 1000 µg for p.o. and ileal routes. Plasma samples were collected and assayed for intact YdAGFdL using a radiometric thin layer chromatography. The clearance (CL) and half lives of the distribution and elimination phases following the 0.28 µg (n=6) i.v. dose were 42.7±26.2 (S.D.) ml/min, 0.48±0.17 min, and 3.98±0.92 min, while those of the 500 µg dose (n=6) were 48.0±23.3 ml/min, 0.59±0.25, and 6.81±3.12 min, respectively, suggesting apparent linear kinetics. The CL values were close to the cardiac output of rats (50 ml/min) indicating very rapid elimination from the body. Mean bioavailability (F) values following p.o. (n=15), jejunal (n=4), and ileal (n=16) administration were 0.40±0.24% (S.E.), 1.25±0.39, and 1.78±0.40, respectively, and were not significantly different (p<0.05) among three doses (1, 1000, 5000 µg). The F value of YdAGFdL following ileal administration in the presence of amastatin was 8.76±4.47% (n=6), a 22 fold increase over po administration and a five fold increase over ileal administration without an inhibitor. These results indicate that ‘effective’ oral delivery of small peptides may be achievable. Copyright © 2002 John Wiley & Sons, Ltd.
Study of thermal effects of ultrasound stimulation on fracture healing
Authors: Chang Walter Hong‐Shong , Sun Jui‐Sheng , Chang Su‐Pei , Lin James C.
Published: August 2002

Low intensity ultrasound stimulation has been used as a strategy to promote fracture healing. This study investigated the mechanism of ultrasound stimulation in enhancing fracture healing. Forty‐five adult New Zealand White rabbits were divided into control, microwave treated, and ultrasound stimulation groups. After anesthesia, transverse osteotomy was created at midportion of the fibula bone. Intravital staining followed by fluorescence microscopic examination of new bone formation in the osteotomy site and biomechanical tests on torsional stiffness of the osteotomy site were performed. The difference between each examination was evaluated and analyzed. After ultrasound stimulation, new bone formation in the osteotomy site of the stimulated limb was 23.1–35.8% faster than that of the sham treated limb; the torsional stiffness of the stimulated limb was 44.4–80.0% higher than that of the sham treated limb. In the group of microwave hyperthermia treatment, the new bone formation was higher than that of the sham treated limb, but the difference was not statistically significant. The difference in torsional stiffness between the microwave hyperthermia treated limbs and the sham treated limb was not quite statistically significant. We demonstrated that low intensity ultrasound stimulation could increase the new bone formation and torsional stiffness. These effects probably are not mediated via hyperthermia. Bioelectromagnetics 23:256–263, 2002. © 2002 Wiley‐Liss, Inc.
Human electrophysiological and cognitive effects of exposure to ELF magnetic and ELF modulated RF and microwave fields: A review of recent studies
Authors: Cook C.M. , Thomas A.W. , Prato F.S.
Published: August 2002

The investigation of weak (<500 μT), extremely low frequency (ELF, 0–300 Hz) magnetic field (MF) exposure upon human cognition and electrophysiology has yielded incomplete and contradictory evidence that MFs interact with human biology. This may be due to the small number of studies undertaken examining ELF MF effects upon the human electroencephalogram (EEG), and the associated analysis of evoked related potentials (ERPs). Relatively few studies have examined how MF exposure may affect cognitive and perceptual processing in human subjects. The introduction of this review considers some of the recent studies of ELF MF exposure upon the EEG, ERPs and cognitive and perceptual tasks. We also consider some of the confounding factors within current human MF studies and suggest some new strategies for further experimentation. Bioelectromagnetics 23:144–157, 2002. © 2002 Wiley‐Liss, Inc.
Chromosomal aberrations in peripheral lymphocytes of train engine drivers
Authors: Nordenson Ingrid , Mild Kjell Hansson , Järventaus Hilkka , Hirvonen Ari , Sandström Monica , Wilén Jonna , Blix Nils , Norppa Hannu
Published: August 2002

Studies of Swedish railway employees have indicated that railroad engine drivers have an increased cancer morbidity and incidence of chronic lymphatic leukemia. The drivers are exposed to relatively high magnetic fields (MF), ranging from a few to over a hundred μT. Although the possible genotoxic potential of MF is unclear, some earlier studies have indicated that occupational exposure to MF may increase chromosome aberrations in blood lymphocytes. Since an increased level of chromosomal aberrations has been suggested to predict elevated cancer risk, we performed a cytogenetic analysis on cultured (48 h) peripheral lymphocytes of Swedish train engine drivers. A pilot study of 18 engine drivers indicated a significant difference in the frequency of cells with chromosomal aberrations (gaps included or excluded) in comparison with seven concurrent referents (train dispatchers) and a control group of 16 office workers. The engine drivers had about four times higher frequency of cells with chromosome‐type aberrations (excluding gaps) than the office workers (P < 0.01) and the dispatchers (P < 0.05). Seventy‐eight percent of the engine drivers showed at least one cell per 100 with chromosome‐type aberrations compared with 29% among the dispatchers and 31% among the office workers. In a follow‐up study, another 30 engine drivers showed an increase (P < 0.05) in the frequency of cells with chromosome‐type aberrations (gaps excluded) as compared with 30 referent policemen. Sixty percent of the engine drivers had one or more cells (per 100 cells) with chromosome‐type aberrations compared with 30% among the policemen. In conclusion, the results of the two studies support the hypothesis that exposure to MF at mean intensities of 2–15 μT can induce chromosomal damage. Bioelectromagnetics 22:306–315, 2001. © 2001 Wiley‐Liss, Inc.