bluuebunny/crossref_metadata_2025_split huggingface dataset:
Amphiphilic polymer gel electrolytes. I. preparation of gels based on poly(ethylene oxide) graft copolymers containing different ionophobic groups
Authors: Gavelin Patrik , Jannasch Patric , Wesslén Bengt 
Published: October 2004

AbstractAmphiphilic graft copolymers were prepared via the radical copolymerization of poly(ethylene oxide) (PEO) macromonomers with fluorocarbon or hydrocarbon acrylates in toluene with 2,2′‐azobisisobutyronitrile (AIBN) as an initiator. 1H NMR spectroscopy confirmed that the composition of the graft copolymers corresponded well to the monomer feed. For gel electrolytes prepared from the amphiphilic copolymers, the nature of the ionophobic parts of the amphiphilic graft copolymers had a great influence on the ion conductivity. Gel electrolytes based on graft copolymers containing fluorocarbon side chains showed significantly higher ion conductivity than electrolytes based on graft copolymers containing hydrocarbon groups. The ambient‐temperature ion conductivity was about 2.6 mS/cm at 20 °C for a gel electrolyte based on an amphiphilic graft copolymer consisting of an acrylate backbone carrying PEO and fluorocarbon side chains. Corresponding gels based on graft copolymers with PEO side chains and hydrocarbon groups showed an ambient‐temperature ion conductivity of about 1.2 mS/cm. The gel electrolytes contained 30 wt % copolymer and 70 wt % 1 M LiPF6 in an ethylene carbonate/γ‐butyrolactone (2/1 w/w) mixture. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2223–2232, 2001
Aromatic polybenzoxazoles containing ether–sulfone linkages
Authors: Hsiao Sheng‐Huei , Chiou Jiun‐Hsiang 
Published: October 2004

AbstractA series of poly(o‐hydroxy amide)s having both ether and sulfone linkages in the main chain were synthesized via the low‐temperature solution polycondensation of 4,4′‐[sulfonylbis(1,4‐phenylene)dioxy]dibenzoyl chloride and 4,4′‐[sulfonylbis(2,6‐dimethyl‐1,4‐phenylene)dioxy]dibenzoyl chloride with three bis(o‐aminophenol)s including 4,4′‐diamino‐3,3′‐dihydroxybiphenyl, 3,3′‐diamino‐4,4′‐dihydroxybiphenyl, and 2,2‐bis(3‐diamino‐4‐hydroxyphenyl)hexafluoropropane. Subsequent thermal cyclodehydration of the poly(o‐hydroxy amide)s afforded polyethersulfone benzoxazoles. Most of the poly(o‐hydroxy amide)s were soluble in polar organic solvents such as N‐methyl‐2‐pyrrolidone; however, the polybenzoxazoles without the hexafluoroisopropylidene group were organic‐insoluble. The polybenzoxazoles exhibited glass‐transition temperatures (Tg) in the range of 219–282 °C by DSC and softening temperatures (Ts) of 242–320 °C by thermomechanical analysis. Thermogravimetric analyses indicated that most polybenzoxazoles were stable up to 450 °C in air or nitrogen. The 10% weight loss temperatures were recorded in the ranges of 474–593 °C in air and 478–643 °C in nitrogen. The methyl‐substituted polybenzoxazoles had higher Tg's but lower Ts's and initial decomposition temperatures compared with the corresponding unsubstituted polybenzoxazoles. For a comparative purpose, the synthesis and characterization of a series of sulfonyl polybenzoxazoles without the ether group that derived from 4,4′‐sulfonyldibenzoyl chloride and bis(o‐aminophenol)s were also reported. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2262–2270, 2001
Copolymers of (2‐cyclohexylidene‐1,3‐dioxolane‐4‐yl) methyl methacrylate with acrylonitrile and styrene: Synthesis, characterization, and monomer reactivity ratios
Authors: İlter Zülfi̇ye , Coşkun Mehmet , Erol İbrahi̇m 
Published: October 2004

AbstractThe copolymerization of (2‐cyclohexylidene‐1,3‐dioxolane‐4‐yl) methyl methacrylate monomer with styrene and acrylonitrile were carried out in 1,4‐dioxane solution at 60 °C using BPO as an initiator. The copolymers were characterized by Fourier transform infrared, 1H NMR, and 13C NMR spectroscopic techniques. Thermal properties of the polymers were also studied by thermogravimetric analysis and differential scanning calorimetry. The copolymer compositions were determined by elemental analysis. The monomer‐reactivity ratios were calculated by the application of conventional linearization methods as a result of Fineman–Ross and Kelen–Tüdős to less than 1 for both monomers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2326–2331, 2001
Synthesis of aminosaccharide‐derived polymers with urea, urethane, and amide linkages
Authors: Bachmann Frank , Ruppenstein Marcus , Thiem Joachim 
Published: October 2004

AbstractThe synthesis of novel polyurethanes and polyureas based on modified glycosylamines and glucosamines has been successfully accomplished by catalytic polymerizations. Several modified glucosamine monomers were synthesized to study their reactivities during these polymerization reactions. It was found that the anomeric hydroxyl groups are more reactive than the amino groups. The resulting polymers were characterized by NMR and IR spectroscopy, elementary analysis, viscosimetry, and gel permeation chromatography. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2332–2341, 2001
Effect of ionic additives on deformation behavior of bisphenol a polycarbonate
Authors: Lee Sang‐Soo , Cho Kilwon , Kim Joonkyung 
Published: October 2004

AbstractThe deformation behavior of bisphenol A polycarbonate containing only a small amount of oligoionomeric additives in the range of a few parts per hundred parts of resin was examined. The impact strength of polycarbonate markedly decreased as the content of additive increased, and brittle fracture of polycarbonate was observed in tensile tests when the concentration of additive was above 2.5 phr. The ductile‐to‐brittle transition that was determined using a comparison of the critical shear yield stress and the critical craze stress appeared to exist in the range of 2.5–3.5 phr of additive. The measured entanglement density was also found to decrease significantly with the addition of a few parts per hundred parts of resin of additives, and the change of the dominant deformation mechanism from ductile to brittle failure was recognized as a result of the change of the entanglement density of polycarbonate. Therefore, it was concluded that the presence of a small amount of ionomeric additives caused the loss of entanglement density that induced transition of the deformation mechanism of polycarbonate from ductile to brittle failure and led to the corresponding deterioration of impact strength. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2635–2643, 2001
Homopolymer and small‐molecule tracer diffusion in a gyroid matrix
Authors: Milhaupt Jodi M. , Lodge Timothy P. 
Published: October 2004

AbstractForced Rayleigh scattering was used to measure the tracer diffusion coefficients of the photochromic dye tetrathioindigo (TTI) and a 1,4‐polyisoprene (PI) homopolymer (8000 g/mol) in a poly(styrene‐b‐isoprene) (SI) diblock copolymer matrix that formed a bicontinuous gyroid microstructure. The diblock copolymer contained 63% polystyrene (PS) by volume and had a total molecular weight of 21,300 g/mol. Rheology and small‐angle X‐ray scattering confirmed that the diblock copolymer microphase‐separated into the bicontinuous gyroid over the temperature range 60–230 °C, where the sample disordered. For both the TTI and PI tracers, two distinct modes of transport were observed. The faster mode displayed a temperature dependence consistent with diffusion within a PI matrix, whereas the slower mode had a temperature dependence more similar to diffusion within PS. The fast diffusivities were both over an order of magnitude lower than in a corresponding PI homopolymer matrix. For TTI, this was attributed to the preferential selectivity of the dye for PS and, therefore, an averaging of the mobility between the PS and PI domains. The slow mode was consistent with a small fraction of the TTI dye molecules becoming trapped within the much slower PS domains. For the PI tracer, the reduction in the diffusion coefficient for the fast mode was attributed to a combination of the tortuosity of the struts, the suppression of constraint release within the diblock matrix, and additional friction due to the presence of some styrene segments within the PI domains. The inevitable presence of grain boundaries or defects within the matrix interrupted the percolation of the PI struts, thereby forcing some of the PI tracers to diffuse through PS. Consequently, the slow mode was attributed to the diffusion through these defects, where the PI diffusion was retarded by both the increased segmental friction and the thermodynamic barrier to entering the PS domains. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 843–859, 2001
Effects of hydroxyl‐group end capping and branching on the physical properties of tailored polyethylene terephthalates
Authors: Oh Sung Jin , Kim Byoung Chul 
Published: October 2004

AbstractPolyethylene terephthalates (PETs) with well‐defined chemical structures were prepared by molecular design, and the effect of the chemical structure on the physical properties of PET was investigated. Hydroxyl‐group end‐capped PETs with ηinh = 0.4–0.6 dL/g exhibited a viscosity behavior similar to Bingham fluids, although other PETs with similar molecular weights (MWs) showed Newtonian flow behavior. This rheological feature was more noticeable for hydroxyl‐group end‐capped branched PETs. In addition, hydroxyl‐group end‐capped branched PETs became solidlike from 80 rad/s as the frequency was increased. On the other hand, hydroxyl end‐capped linear PETs showed a noticeable viscoelastic transition peak around 20 rad/s. High MW linear and branched PETs with ηinh ≥ 0.9 prepared by multistep synthesis showed non‐Newtonian fluid behavior. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1027–1035, 2001
Kinetically controlled phase transitions in LC polymers. I. Isokinetic range crossover for the Sm B–Sm H transition in a side‐chain polysiloxane
Authors: Kozlovsky Mikhail V. 
Published: October 2004

AbstractThe kinetics of smectic‐phase formation in a siloxane copolymer, as compared with the crystallization of the relating homopolymer, was studied by the Avrami analysis of DSC data. A crossover from the diffusion‐controlled kinetics (the Avrami exponent k ∼0.35) to the two‐dimensional free‐growth mode (k ∼1.5) with increasing temperature was detected. The influence of the annealing temperature on the sequence of mesophases, transition temperatures, and enthalpies of the polymers was also investigated. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1055–1060, 2001
Viscoelastic properties and phase behavior of 12‐tert‐butyl ester dendrimer/poly(methyl methacrylate) blends
Authors: Emran S. K. , Liu Y. , Newkome G. R. , Harmon J. P. 
Published: October 2004

AbstractThis study used refractometry, ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and dielectric analysis to assess the viscoelastic properties and phase behavior of blends containing 0–20% (w/w) 12‐tert‐butyl ester dendrimer in poly(methyl methacrylate) (PMMA). Dendritic blends were miscible up through 12%, exhibiting an intermediate glass‐transition temperature (Tg; α) between those of the two pure components. Interactions of PMMA CO groups and dendrimer NH groups contributed to miscibility. Tg decreased with increasing dendrimer content before phase separation. The dendrimer exhibited phase separation at 15%, as revealed by Rayleigh scattering in ultraviolet–visible spectra and the emergence of a second Tg in dielectric studies. Before phase separation, clear, secondary β relaxations for PMMA were observed at low frequencies via dielectric analysis. Apparent activation energies were obtained through Arrhenius characterization. A merged αβ process for PMMA occurred at higher frequencies and temperatures in the blends. Dielectric data for the phase‐separated dendrimer relaxation (αD) in the 20% blend conformed to Williams–Landel–Ferry behavior, which allowed the calculation of the apparent activation energy. The αD relaxation data, analyzed both before and after treatment with the electric modulus, compared well with neat dendrimer data, which confirmed that this relaxation was due to an isolated dendrimer phase. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1381–1393, 2001
Calorimetry of nanophase‐separated poly(oligoamide‐alt‐oligoether)s
Authors: Di Lorenzo M. L. , Pyda M. , Wunderlich B. 
Published: October 2004

AbstractThe miscibility, crystallization, vitrification, and melting behavior of multiblock copolymers consisting of alternating components of oligo[imino(1‐oxododecamethylene)] and oligo(oxytetramethylene) were investigated in their dependence of composition and molecular mass of the blocks. In all compositions studied, the copolymers present two separate glass transitions at temperatures not far from those of the corresponding homopolymers. The immiscible components are linked by chemical bonds to nanophase‐separated layers. In such a situation, the structure and mobility of each phase affect the other, causing small shifts of the glass‐transition temperatures. The enthalpy‐based crystallinity was calculated separately for each component, using the known information on heat capacities and latent heats. The crystallinity is influenced by the block lengths. The oligoamide segments crystallize from an isotropic melt with a relatively high crystallinity, whereas the oligoether blocks solidify in the presence of crystals and glass of the second component in the adjacent solid nanophases, which greatly reduces their overall long‐range chain mobility, and as a consequence, their crystallinity is rather small. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1594–1604, 2001
Evaluation methods of the longest Rouse relaxation time of an entangled polymer in a semidilute solution
Authors: Osaki K. , Inoue T. , Uematsu T. , Yamashita Y. 
Published: October 2004

AbstractEstimation methods for the longest Rouse relaxation time (τR) of an entangled polymer in a semidilute solution were examined. We evaluated τR by fitting the dynamic modulus (G′) with the Rouse model theory in the power law range, where G′ was proportional to the square root of the angular frequency (ω). The τR values thus obtained for polystyrene (PS) solutions in tricresyl phosphate (TCP) were employed to derive an empirical formula for the evaluation of τR from the viscosity (η): M is the molecular weight, and c is the mass of polymer per unit volume; Me = cRT/GN is the entanglement molecular weight, where GN is the G′ value at the inflection point of the graph of log G′ versus log ω. The subscript η indicates that τR is derived from η data. The proposed equation was also applicable to bulk PS and bulk polyisoprene. Discrepancies among reported τR values in semidilute solutions seem to be mostly due to discrepancies in Me values. For PS solutions in dioctyl phthalate, a Θ solvent, the τR value derived from η was much larger than that from the G′ curve. Apart from the evaluation method of τR, we observed for PS that Me was independent of temperature for good solvent systems and melts, that Me for solutions in TCP agreed with that for solutions in another good solvent, and that Me for a Θ‐solvent system was equal to that for good solvent systems with the same M and c values. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1704–1712, 2001
Molecular dynamics studies on HIV‐1 protease: Drug resistance and folding pathways
Authors: Cecconi Fabio , Micheletti Cristian , Carloni Paolo , Maritan Amos 
Published: October 2004

AbstractDrug resistance to HIV‐1 protease involves the accumulation of multiple mutations in the protein. We investigate the role of these mutations by using molecular dynamics simulations that exploit the influence of the native‐state topology in the folding process. Our calculations show that sites contributing to phenotypic resistance of FDA‐approved drugs are among the most sensitive positions for the stability of partially folded states and should play a relevant role in the folding process. Furthermore, associations between amino acid sites mutating under drug treatment are shown to be statistically correlated. The striking correlation between clinical data and our calculations suggest a novel approach to the design of drugs tailored to bind regions crucial not only for protein function, but for folding as well. Proteins 2001;43:365–372. © 2001 Wiley‐Liss, Inc.
Theoretical evidence of a salt bridge disruption as the initiating process for the α1d‐adrenergic receptor activation: A molecular dynamics and docking study
Authors: Carrieri A. , Centeno N.B. , Rodrigo J. , Sanz F. , Carotti A. 
Published: October 2004

AbstractThis study reports the building of the three‐dimensional structure of the rat α1d‐adrenergic receptor through a topology approach based on the structure of the rhodopsin receptor from cryoelectron microscopy. The validity and reliability of the receptor model were assessed through exhaustive molecular dynamics and docking studies. Some interesting ligand‐receptor interactions were identified along with significant differences between the binding mode of agonists and antagonists. The importance of the disruption of a salt bridge as a possible initial event leading to receptor activation is discussed on the basis of data from mutagenesis and molecular dynamics studies. Proteins 2001;43:382–394. © 2001 Wiley‐Liss, Inc.
Demographic versus genetic dispersal measures
Authors: Vandewoestijne Sofie , Baguette Michel 
Published: October 2004

AbstractQuantifying dispersal, a fundamental biological process, is far from simple. Here, both direct and indirect methods were employed to estimate dispersal in an endangered butterfly species. A high and significant correlation between the dispersal patterns, generated by an inverse power function fitted to capture‐mark‐recapture (CMR) data on the one hand, and population genetic analyses on the other hand, was observed. Stepping‐stone type movements were detected by both methods, evidence for the importance of connectivity in the studied metapopulation. These results are particularly relevant to those population and conservation biology studies where quantifying dispersal is essential for the elaboration of successful management actions.
Nasopharyngeal Tuberculosis: Manifestations between 1991 and 2000
Authors: Srirompotong Somchai , Yimtae Kwanchanok , Jintakanon Darunee 
Published: October 2004

OBJECTIVES/HYPOTHESISTo present the clinical manifestation of nasopharyngeal tuberculosis.STUDY DESIGNClinical analysis of 23 patients with pathologically confirmed nasopharyngeal tuberculosis was carried out retrospectively.SETTINGSrinagarind Hospital, Khon Kaen University. Thailand.RESULTSThe most common presenting symptom was cervical lymphadenopathy (91.3%). The common locations of nodes were the superior and middle cervical. The abnormalities of the nasopharynx were found in 16 patients. The pathological findings were caseous granuloma with positive acid‐fast bacilli (AFB) in 15 cases, caseous granuloma with negative AFB in 3 cases, and chronic granulomatous inflammation with negative AFB in 5 cases. Pulmonary tuberculosis was found in 8 of 18 patients. Sixteen patients who received complete treatment responded well.CONCLUSIONNasopharyngeal tuberculosis commonly presents with cervical lymphadenopathy. The differential diagnosis of tuberculosis from nasopharyngeal carcinoma is difficult. In the patients who have cervical lymphadenopathy and no other identified causes, biopsy of nasopharynx would give an additive information for diagnosis.
Starplasty: Revisiting a Pediatric Tracheostomy Technique
Authors: Solares C. Arturo , Krakovitz Paul , Hirose Keiko , Koltai Peter J. 
Published: October 2004

OBJECTIVETo determine the efficacy the “starplasty” pediatric tracheostomy technique in reducing the incidence of major complications and tracheotomy‐related death.METHODSRetrospective chart analysis of all the cases of starplasty performed at 2 tertiary care centers between 1990 and 2002.RESULTSThere were 94 children in our cohort ranging in age from 2 days to 14 years. Of the patients, 47 (50%) were females and 47 (50%) were males and 60 of the children (64%) were younger than 1 year of age. Forty‐one patients (44%) had neurologically related airway problems as their primary indication for tracheostomy, 34 (36%) had upper airway obstruction, and the remainder had pulmonary diseases, prolonged intubation, or metabolic‐related airway problems. There were 41 short‐term complications including 5 cases of tracheal tube dislodgement. There were no instances of pneumothorax or tracheostomy‐related death. There were 26 long‐term complications. There were no cases of clinically relevant suprastomal collapse that compromised decannulation and no instances of tracheal stenosis. Twenty‐six patients underwent decannulation, all of whom developed a tracheocutaneous fistula (TCF). Two patients had spontaneous closure of the TCF; 9 patients underwent surgical repair of their fistulas, 53 patients remain tracheostomy‐dependent, and 8 patients died of their primary disease.CONCLUSIONThe need for pediatric tracheotomy has increased as a consequence of our success in treating chronically ill children. Starplasty reduces the incidence of major complications, including pneumothorax and death from accidental decannulation. Its major drawback is the need for secondary reconstruction of a tracheocutaneous fistula. EBM rating: C.
Phenotypic and Microarray Gene Expression Analysis of Tri‐Dimensional Raft‐Modeled Human Head and Neck Squamous Cell Carcinoma
Authors: Zanation Adam M. , Yin Xiaoying , Shores Carol , Yarbrough Wendell G. 
Published: October 2004

OBJECTIVESTo describe the phenotypic and gene expression differences in monolayer and tri‐dimensional cultures systems.METHODSNormal oral epithelial cells (NOEC), primary head and neck squamous cell carcinoma (HNSCC), and HNSCC cell lines were used to create and study modeled tri‐dimensional tissue. Using cDNA microarray analysis, monolayer and raft‐modeled tri‐dimensional HNSCC cell lines were compared.RESULTSNOEC, HNSCC, and both together can be modeled with tri‐dimensional differentiation and cytokeratin characteristics analogous to in vivo tissue. Modeling of primary HNSCC resulted in a morphology of invasive HNSCC with areas of direct collagen invasion and MMP2 expression. Gene array analysis suggests that the individual cell lines themselves are the primary gene expression predictor and not the presence of tri‐dimensional tissue architecture.CONCLUSIONSThis tissue culture modeling system approximates the differentiation and tri‐dimensional structure of in vivo tissues, and that raft modeled tri‐dimensional HNSCC does not have a significantly different gene expression profile than the corresponding monolayer culture.