bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of plant gums on thermal polymerization of acrylonitrile
Authors: Jana S. C. , Maiti S. , Sengupta P. K. , Biswas S. 
Published: October 2002

AbstractThe effect of some plant gums on the polymerization of acrylonitrile (AN) using ceric ammonium nitrate (CAN) as an initiator in the presence of air (containing 21% oxygen) was studied. The induction period and percent conversion were determined. The induction period in the presence of gum was comparatively lower than that under a N2 atmosphere. The rate of polymerization has a 1.5‐power dependence on the monomer concentration and the rate is sufficiently high at moderate temperature. The rate also increased with an increasing initiator concentration and reaches a maximum value of 93% at 0.72 × 10−2 mol L−1 of CAN. The activation energy was found to be 6.4 kcal mol−1. Both the molecular weight and density of the polyacrylonitrile (PAN) prepared in the presence of gum were higher than those of PAN prepared in the absence of the gum. The PAN produced in the presence of the gum was thermostable than that prepared in its absence. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3596–3600, 2002
Analysis of physical properties of PET/CD‐PET polyblend hollow fiber and its kinetics of alkaline hydrolysis
Authors: Hsiao Kai‐Jen , Jen Zhi‐Feng , Lu Cheng‐Liang 
Published: October 2002

AbstractCationic dyeable poly(ethylene terephthalate) (CD‐PET) was formed by copolymerizing dimethylterephthalate (DMT),5‐sodium sulfonate dimethyl isophthalate (SIPM) with a molar ratio of 2% and ethylene glycol (EG). Blends of regular poly(ethylene terephthalate) (PET) and CD‐PET were spun into hollow fibers. The fibers were then treated with aqueous NaOH. This study investigated the physical properties of PET/CD‐PET polyblend hollow fibers and their kinetic behavior of alkaline hydrolysis using differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), the density gradient method, a gel permeation chromatograph (GPC), a rheometer, and regression analysis of the statistical method. For the alkaline hydrolysis kinetics equation of PET, CD‐PET, and PET/CD‐PET polyblend materials: − dW/dt = KCαAβ, β values of chip and POY/ FOY hollow fibers are equal to 1. Moreover, R2 of the kinetics equation of chip/POY/FOY for a from 1.09–1.35/1.08–1.32/1.06–1.29 were better than those of a = 1. Experimental results indicate that the rate constant of alkaline hydrolysis was CD‐PET hollow fiber > PET/CD‐PET polyblend hollow fibers > PET hollow fiber and FOY > POY > > Chip. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3601–3610, 2002
Characterization of an amorphous surface layer on blown polyolefin film
Authors: Chang A. C. , Chum S. P. , Hiltner A. , Baer E. 
Published: October 2002

AbstractThis study concerned an amorphous surface layer on blown polyethylene film with a composition different from that of the bulk. The surface layer was characterized by gentle probing with an atomic force microscope. The demonstration of an amorphous layer uniformly covering the surface of a blown Ziegler–Natta‐catalyzed polyethylene (znPE) film reproduced previous reports. Removing the surface layer by solvent washing confirmed the hypothesis that the layer consisted of lower molecular weight, higher branch content fractions. A blown film of znPE blended with up to 30 wt % impact‐modified high‐melt‐strength polypropylene (hmsPP) also exhibited an amorphous surface layer. In thin films, it was advantageous for the mobile, amorphous fractions of ethylene–propylene rubber (EPR) to locate at the surface rather than at the phase interface. The amorphous EPR tended to segregate into pools on the film surface, and this pointed to a substantial difference between the amorphous surface layers on the znPE and hmsPP/znPE blend films. Surface enrichment best described the compositional gradient that resulted from the concentration of lower molecular weight, higher branch content chains at the surface of the znPE film. Surface segregation was more appropriate for the emergence of EPR fractions as a separate phase on the surface of the hmsPP blend film. Films blown from a blend of a Ziegler–Natta‐catalyzed polyethylene and a metallocene‐catalyzed polyethylene (zn/mPE) and its blend with hmsPP reproduced the primary features of surface enrichment and surface segregation. Some differences between the znPE and zn/mPE films were attributed to the metallocene constituent of zn/mPE. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3625–3635, 2002
Block copolyesters of poly(pentamethylene 2,6‐naphthalenedicarboxylate) and poly(tetramethylene adipate)
Authors: Tsai Ruey‐Shi , You Jiang‐Wen , Lee Yu‐Der , Tsai Hong‐Bing 
Published: October 2002

AbstractHydroxy‐terminated poly(pentamethylene 2,6‐naphthalenedicarboxylate) oligomers were prepared by melt polycondensation of dimethyl 2,6‐naphthalenedicarboxylate with excess 1,5‐pentanediol followed by evacuating out some 1,5‐pentanediol. The molecular weight of the poly(pentamethylene 2,6‐naphthalenedicarboxylate) oligomers was controlled by the charge molar ratio of 1,5‐pentanediol to dimethyl 2,6‐naphthalenedicarboxylate and the amount of 1,5‐pentanediol removed under vacuum. The 1H‐NMR spectra of the poly(pentamethylene 2,6‐naphthalenedicarboxylate) oligomers indicate that the transesterification between dimethyl 2,6‐naphthalenedicarboxylate and 1,5‐pentanediol was almost complete. Block copolyesters with hard segments of poly(pentamethylene 2,6‐naphthalenedicarboxylate) and soft segments of poly(tetramethylene adipate) were prepared by coupling the poly(pentamethylene 2,6‐naphthalenedicarboxylate) oligomer and a poly(tetramethylene adipate) glycol with methylene‐4,4′‐diphenylene diisocyanate in solution. The block copolyesters were characterized by IR, 1H‐NMR, DSC, and X‐ray diffraction. The hard segments in the block copolyesters display an amorphous state. However, the thermal transitions of soft segments in the block copolyesters are strongly dependent on the composition. When the content of the hard segments increases, the glass transition temperature of the soft segments increases. Thus, the amorphous parts of the soft segments would be partially miscible with the hard segments. When the content of the hard segments is very low, the soft segments of the block copolyesters exhibit high crystallinity. But, as the content of the hard segments is about 30 wt % or more, the soft segments of the block copolyesters become amorphous. This is described as the effect of the presence of the hard segments which are partially miscible with the soft segments. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3652–3659, 2002
Effects of microstructures on the viscoelastic and rheological properties of metallocene‐catalyzed cyclo‐olefin copolymers: A preliminary study
Authors: Shih Hsi‐Hsin , Shiao Po‐Ling , Hsu Hsiu‐Chin , Liu Hsin‐Ju , Huang Chi‐Jou , Tsai Chin‐Chin 
Published: October 2002

AbstractWe characterized metallocene‐catalyzed cyclo‐olefin copolymers (mCOCs) with similar heat distortion temperatures but dramatic differences in melt‐flow indices to understand how the molecular conformation affected their rheological and viscoelastic properties. The mCOC conformations were identified with 13C‐NMR, whereas the viscoelastic and rheological properties were measured with cone‐and‐plate and high‐pressure capillary rheometers. Our preliminary results showed that the mCOC rheological and viscoelastic properties might depend strongly on the conformation rather than the norbornene content, molecular weight, and molecular weight distribution. mCOCs containing ‐NNN‐ locks (where N represents norbornene) exhibited stronger molecular entanglements than those having no ‐NNN‐ blocks, as reflected in lower crossover frequencies and higher crossover torque. Furthermore, the existence of larger rigid ‐NNN‐ blocks resulted in higher molten viscosities and flow activation energies. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3695–3701, 2002
Surface characteristics of water‐soluble cationic fluoro copolymers containing perfluoroalkyl, quaternized amino, and hydroxyl groups
Authors: Lee Chang‐Yong , Ha Jong‐Wook , Jun Park In , Lee Soo‐Bok 
Published: October 2002

AbstractVarious water‐soluble cationic fluoro copolymers in quaternized form with perfluoroalkyl, amino, and hydroxyl groups were prepared by varying the contents of perfluoroalkyl ethyl acrylate (FA), 2‐(dimethylamino) ethyl methacrylate (DAMA), and 2‐hydroxyethyl methacrylate (HEMA). The solvent polymerization was carried out in acetone, with the subsequent addition of acetic acid to form a quaternized polymer. Polyurethanes films were prepared by curing aqueous solutions containing water‐soluble cationic fluoro copolymers and a blocked isocyanate at 190°C. The surface characteristics of the water‐soluble cationic fluoro copolymers and the polyurethanes were investigated on the basis of FA and DAMA contents. The contact angles for both water and methylene iodide (MI) on the cationic fluoro copolymer and the polyurethane increase steadily as FA content increases, and decrease gradually with increasing DAMA content. The contact angles on the polyurethane are slightly higher than those on the cationic fluoro copolymer. The cationic fluoro copolymer and the polyurethane with FA content of 40 wt % and DAMA content of <30 wt % show extremely low surface free energies of 13–15 dynes/cm. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3702–3707, 2002
Synthesis and structure of polymethylsilsesquioxane–clay nanocomposite via in situ intercalative polymerization
Authors: Ma Jun , Shi Lianghe , Yang Mingshu , Li Baiyu , Liu Haiyun , Xu Jian 
Published: October 2002

AbstractPolymethylsilsesquioxane (PMSQ)–montmorillonite (MMT) nanocomposites were prepared by in situ intercalative polymerization. The dispersion of the MMT layers within the matrix was verified by X‐ray diffraction and transmission electron microscopy, which revealed an intercalated morphology with layer spacing of 3.42 nm. The layer spacing was not increased after annealing at 150°C for 3 h. The reason for this result is explained in light of the molecular structure of PMSQ synthesized in and out of the nanoconfined environment. The coherent order of the silicate layer was decreased after the annealing, possibly because of the change in the PMSQ molecule during the annealing process. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3708–3711, 2002
Study on foaming water‐swellable EPDM rubber
Authors: Sun Xiaohong , Zhang Guo , Shi Qiang , Tang Benchen , Wu Zhongwen 
Published: October 2002

AbstractA foaming ethylene propylene diene terpolymer (EPDM) water‐swellable rubber (WSR) was prepared using the multicomponent mechanical blending technology. The morphology of unfilled and silica‐filled foaming EPDM WSR was studied from micrographs. The average cell size, maximum cell size, and cell density of the foaming WSR had a peak value with a 4‐phr foaming agent loading in both unfilled and silica‐filled WSR. The addition of silica made the average cell size and maximum cell size decrease and the cell uniform. With incorporation of silica, the tensile strength of the unfoaming WSR increased three times, while that of the foaming WSR increased about six times before immersing it into water. After water‐swelling, the mechanical properties of both the unfilled WSR and silica‐filled unfoaming WSR decreased, but that of the silica‐filled foaming WSR increased. The silica filler accelerated the water‐swelling rate and cut down the water‐swelling equilibrium time at the same time. The foaming WSR had a better volume water‐swelling ratio than that of the unfoaming WSR in both the unfilled and silica‐filled WSR. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3712–3717, 2002
Moisture absorption behavior of rubber‐modified epoxy resins
Authors: Lin King‐Fu , Yeh Ren‐Jie 
Published: October 2002

AbstractThe moisture absorption behavior of diglycidyl ether of bisphenol A/ethylene diamine resins incorporating a carboxy‐terminated butadiene–acrylonitrile rubber was investigated and associated with their morphology of phase separation. Although the diffusion coefficient of moisture was increased with the rubber content, its activation energy and free volume for moisture diffusion were barely changed until phase inversion occurred. After phase inversion, the free volume was significantly increased, and the activation energy decreased. In addition, the moisture absorption also reduced the β‐transition temperature of the resins and slightly increased the glass‐transition temperature before phase inversion. However, the reverse was found after phase inversion. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3718–3724, 2002
Networks of photocrosslinked poly(meth)acrylates in linear poly(vinyl chloride)
Authors: Kaczmarek Halina , Ołdak Dagmara , Szalla Aleksandra 
Published: October 2002

AbstractFive different multifunctional acrylic monomers (trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol pentaacrylate) were photopolymerized alone or in a matrix of linear poly(vinyl chloride) (PVC) with 2,2‐dimethyl‐2‐hydroxyacetophenone as a photoinitiator. The course of photopolymerization was estimated with Fourier transform infrared spectroscopy. The amount of insoluble gel formed during photopolymerization was determined gravimetrically. The crosslinked polymerization of pure monomers was much faster than that in the presence of PVC. However, the efficiency of the reaction was higher when it was carried out in a PVC blend because of the higher mobility of the propagating macroradicals. The influence of the monomer structure and functionality on the polymerization course was examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3725–3734, 2002
Evidence that thermodynamic stability of papaya glutamine cyclase is only marginal
Authors: Azarkan Mohamed , Amrani Amina , Zerhouni Samira , Oberg Keith A. , Ruysschaert Jean‐Marie , Wintjens René , Looze Yvan 
Published: October 2002

AbstractPapaya glutamine cyclase (PQC), a glycoprotein with a molecular mass of 32,980 Da, is a minor constituent of the papaya latex protein fraction. In neutral aqueous solutions, PQC adopts an all‐β conformation and exhibits high resistance to both proteolysis and denaturation. Complete unfolding of PQC requires a combination of an acidic medium and chemical denaturant such as urea or guanidine hydrochloride. The unfolding process takes place through formation of an intermediate A state that accumulates in the absence of chemical denaturants and displays all the features of a molten globule state. The different conformational states—N (native), A (acid‐inactivated), and U (unfolded)—have been characterized by means of circular dichroism measurements, fluorescence spectroscopies, Stokes radii determinations, and 8‐anilino‐1‐naphtalenesulfonic acid (ANS) binding characteristics. The unfolding pathways of the enzyme was further studied to estimate thermodynamic parameters characterizing both transitions N ⇔ A and A ⇔ U. In its A state, PQC is catalytically inefficient and highly susceptible to proteolysis. Also, its thermodynamic stability is decreased by some 3–5 kcal/mol. Conversion of the native to the A state involves digging up of five amino functions together with protonation of four to five acidic groups with pKas, in the native state, around 2.7. It proceeds both cooperatively and reversibly although, in vitro, the refolding process is slow. Unfolding of the A state, on the other hand, occurs with a low degree of cooperativity. The intermediate A state thus seems to be only marginally more stable than the unfolded state. The role of suspected internal ion pairs in the stabilization of the native state of this enzyme is discussed. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 325–335, 2002
The ribbon of hydrogen bonds and the pseudomolecule in the three‐dimensional structure of globular proteins. III. Bovine pancreatic ribonuclease A and bovine seminal ribonuclease
Authors: Peters David , Peters Jane 
Published: October 2002

AbstractThe model of the three‐dimensional structure of globular proteins, which is based on a ribbon of hydrogen bonds along the whole of the backbone, is now applied to the comparison between monomeric bovine pancreatic ribonuclease A and dimeric bovine seminal ribonuclease. Some waters are involved in the hydrogen bonding of the ribbon, and the protein molecule plus these waters forms a pseudomolecule. The conformations of the three backbones are essentially identical and the three ribbons of hydrogen bonds are conserved with greater than 90% accuracy. We suggest that the conservation of the backbone conformations of the two molecules is a consequence of the conservation of the ribbons of hydrogen bonds. There are 16 simple mutations between the two molecules, of which 15 involve only side‐chain groups with no more than one hydrogen bond to the backbone. Such mutations are not sufficient to change the ribbon of hydrogen bonds and hence there is no change in the backbone conformation. Generalizing this result, we suggest that the conservation of the ribbon is the reason why single point mutations rarely change the conformation of the backbone of the globular proteins. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 347–353, 2002
Peptide conformational changes induced by tryptophan–phosphocholine interactions in a micelle
Authors: Neidigh Jonathan W. , Andersen Niels H. 
Published: October 2002

AbstractSodium dodecylsulfate (SDS) and dodecylphosphocholine (DPC) micelles are often used to mimic the membrane‐ or receptor‐bound states of peptides in NMR studies. From the present examination of a 26‐residue analog of exendin‐4 (TrEX4) by NMR and CD in water, aqueous 30% trifluoroethanol (TFE), and bound to both SDS and DPC micelles, it is clear that these two lipid micelles can yield very different peptide structures. The Trp‐cage fold (also observed in 30% TFE) is present when TrEX4 is bound to SDS micelles; however, tertiary structure is absent in the presence of DPC micelles. The loss of tertiary structure is attributed to an energetically favorable interaction (estimated as 2–3 kcal/mol) of the tryptophan side chain with the phosphocholine head groups. These dramatic structural differences suggest that care must be taken when using either SDS or DPC to mimic the membrane‐ or receptor‐bound states. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 354–361, 2002
Redefining the tonotopic core of rat auditory cortex: Physiological evidence for a posterior field
Authors: Doron Neot N. , Ledoux Joseph E. , Semple Malcolm N. 
Published: October 2002

AbstractPrevious physiological studies have identified a tonotopically organized primary auditory cortical field (AI) in the rat. Some of this prior research suggests that the rat, like other mammals, may have additional fields surrounding AI. We, therefore, recorded in the Sprague‐Dawley rat extracellular responses of single neurons throughout AI, and continued posteriorly to verify the existence of a posterior field (P) and to compare the neuronal properties in the two regions. Acoustic stimuli, including tones, bandpass noise, broadband noise, and temporally modulated stimuli, were delivered dichotically via sealed systems. Consistent with previous findings, AI was characterized by an anterior‐to‐posterior tonotopic progression from high to low frequencies (ranging from >40 kHz to <1 kHz). A frequency reversal at the posterior border of AI marked entry into a second core tonotopic region, P, with progressively higher frequencies encountered further posteriorly, up to a point (approximately 8 kHz) where cells were no longer tone responsive. Nevertheless, bandpass noise was an effective stimulus in P, enabling characterization of cells up to 15 kHz. Compared with AI, the frequency tuning of response areas was relatively broader in P, the response latency was often longer and more variable, and the response magnitude was more commonly a nonmonotonic function of stimulus level. In both fields, most neurons were binaurally influenced. The presence of multiple auditory cortical fields in the rat is consistent with auditory cortical organization in other mammals. Moreover, the response properties of P relative to AI in the rat also resemble those found in other mammals. Finally, the physiological data suggest that core auditory cortex (temporal area TE1) is composed not only of AI as previously thought, but also of at least two other subdivisions, P and an anterior field (A). Furthermore, our physiological characterization of TE1 reveals that it is larger than suggested by previous anatomical characterizations. J. Comp. Neurol. 453:345–360, 2002. © 2002 Wiley‐Liss, Inc.
Roles of estrogen receptor α and androgen receptor in the regulation of neuronal nitric oxide synthase
Authors: Scordalakes Elka M. , Shetty Savera J. , Rissman Emilie F. 
Published: October 2002

AbstractIn brain and peripheral tissues, steroid hormones regulate nitric oxide synthase (nNOS). We asked whether estrogen receptor‐α (ERα) and/or androgen receptor (AR) regulated nNOS immunoreactivity in mouse brain. First, we quantified cells singly labeled for nNOS immunoreactivity or labeled dually with ERα‐immunoreactive (‐ir) or AR‐ir cells in the nucleus accumbens (Acb), preoptic area (POA), bed nucleus of the stria terminalis (BNST), posterior dorsal and posterior ventral regions of the medial amygdala (MePD and MePV, respectively), and paraventricular nucleus (PVN). The POA and MePD contained the greatest number of double‐labeled cells. More nNOS‐ir cells were colabeled with ERα immunoreactivity compared with AR immunoreactivity. Next, by using a double mutant mouse in which males lacked functional ERα, AR, or both, we investigated the roles of these steroid receptors in nNOS‐ir cell numbers and immunoreactive area staining under testosterone (T) and estradiol (E2) conditions. Our data show that functional ERα is correlated with more nNOS‐ir cells under T conditions and more immunoreactive area staining in the POA under both T and E2 conditions. However, ERα decreases nNOS‐ir cell number in the BNST under E2 treatment. In summary, the data suggest that AR has organizational actions on nNOS‐ir cell numbers in the MePV, that interactions between ERα and AR genes occur in PVN, and that sex differences in nNOS‐ir area staining are limited to the POA. Thus, we show that ERα and AR interact to regulate nNOS in male and female brain in a site‐specific manner. J. Comp. Neurol. 453:336–344, 2002. © 2002 Wiley‐Liss, Inc.
Changes in grain size of sand in transport over a foredune
Authors: Arens S. M. , van Boxel J. H. , Abuodha J. O. Z. 
Published: October 2002

AbstractSuspended sand is sampled at several heights and positions on a beach and foredune, providing detailed insight into the vertical and horizontal variation in sand content in the air during landward transport. Grain‐size analysis is used to study the changes in grain‐size distribution during landward transport. Mean grain size and sorting decrease during transport. Changes in textural parameters follow a gradual and regular path when the sediment is transported into the foredune. Sediment trapped on the seaward slope at a height of 30–50 cm above the surface closely resembles the sediment trapped landward, which implies that changes in the direction of transport are related to vertical changes within the sediment transport profiles. The movement of sand over the vegetated foredunes is induced by turbulent forces created by the air flowing across the vegetation and the foredune, leading to a change from saltation on the beach to modified saltation and suspension on the foredune. Small grains are lifted higher and fall more slowly than coarse grains and therefore are transported further landward, resulting in a gradual decrease in grain size of the landward‐deposited sediment. Copyright © 2002 John Wiley & Sons, Ltd.