bluuebunny/crossref_metadata_2025_split huggingface dataset:
Liquid‐crystalline organic–inorganic hybrid polymers with functionalized silsesquioxanes
Authors: Kim Kyung‐Min , Chujo Yoshiki 
Published: August 2002

AbstractLiquid‐crystalline (LC) hybrid polymers with functionalized silsesquioxanes with various proportions of LC monomer were synthesized by the reaction of polyhedral oligomeric silsesquioxane (POSS) macromonomer with methacrylate monomer having an LC moiety under common free‐radical conditions. The obtained LC hybrid polymers were soluble in common solvents such as tetrahydrofuran, toluene, and chloroform, and their structures were characterized with Fourier transform infrared, 1H NMR, and 29Si NMR. The thermal stability of the hybrid polymers was increased with an increasing ratio of POSS moieties as the inorganic part. Because of the steric hindrance caused by the bulkiness of the POSS macromonomer, the number‐average molecular weight of the hybrid polymers gradually decreased as the molar percentage of POSS in the feed increased. Their liquid crystallinities were very dependent on the POSS segments of the hybrid polymers behaving as hard, compact components. The hybrid polymer with 90 mol % LC moiety (Cube‐LC90) showed liquid crystallinity, larger glass‐transition temperatures, and better stability with respect to the LC homopolymer. The results of differential scanning calorimetry and optical polarizing microscopy showed that Cube‐LC90 had a smectic‐mesophase‐like fine‐grained texture. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4035–4043, 2001
Long‐lived intermediates in reversible addition–fragmentation chain‐transfer (RAFT) polymerization generated by γ radiation
Authors: Barner‐Kowollik Christopher , Vana Philipp , Quinn John F. , Davis Thomas P. 
Published: August 2002

AbstractA novel experimental procedure is presented that allowed probing of reversible addition–fragmentation chain‐transfer (RAFT) free‐radical polymerizations for long‐lived species. The new experimental sequence consisted of gamma irradiation of a mixture of initial RAFT agent (cumyl dithiobenzoate) and monomer at ambient temperature, a subsequent predetermined waiting period without initiation source also at ambient temperature, and then heating of the reaction mixture to a significantly higher temperature. After each sequence step, the monomer conversion and molecular weight distribution were determined, indicating that controlled polymer formation occurs only during the heating period. The results indicated that stable intermediates (either radical or nonradical in nature) are present in such experiments because thermal self‐initiation of the monomer can be excluded as the reason for polymer formation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1058–1063, 2002
Negative‐working photoresist of methacrylate polymers based on the transesterification of the 2‐hydroxyethyl group in the presence of an acid
Authors: Lee Jongsoo , Aoai Toshiaki , Kondo Syun'ichi , Miyagawa Nobukazu , Takahara Shigeru , Yamaoka Tsuguo 
Published: August 2002

AbstractThis article reports a novel crosslinking functionality of the 2‐hydroxyethyl methacrylate unit (HEMA) in the presence of an acid. The polymeric compositions, consisting of a polymer containing the HEMA unit and a photoacid generator, were insolubilized in an aqueous base developer on exposure to UV light and a successive baking process to provide a negative‐working photoresist. A series of poly(benzyl methacrylate‐co‐methacrylic acid‐co‐2‐hydroxyethyl methacrylate) terpolymers with various contents of HEMA were prepared to elucidate the photopolymeric characteristics. The polymer behavior in films was examined by a comparison of the photosensitivity and IR spectroscopic method. Experiments with a model compound were also carried out. On the basis of the results, we found that the resist was insolubilized by crosslinking through the transesterification of HEMA segments due to acid generated from the photoacid generator and subsequent heating. The advantage of using the 2‐hydroxyethyl group is that in the terpolymer, the HEMA unit is transparent at a short‐wavelength region and is a promising crosslinking unit for ArF lithographic photoresists. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1858–1867, 2002
Ionic poly(p‐phenylene terephthalamide)s: Solubility and thermal stability
Authors: Chen W. C. , Sauer J. A. , Hara M. 
Published: August 2002

AbstractIonic sulfonate groups were incorporated onto molecules of the rigid‐rod polymer poly(p‐phenylene terephthalamide) (PPTA) in two different positions. In one type, S‐PPTA, ionic sulfonate groups were attached to the phenylene ring of the backbone chain. S‐PPTA solubility was achieved in dimethylsulfoxide (DMSO) when 50% of the repeat units contained an ionic group. In the second type, PPTA‐PS, where ionic propanesulfonate groups served as side chains, solubility was achieved in DMSO when 30% of the repeat units contained the ionic group. For both of the partially sulfonated ionic polymers, the thermal stability was enhanced in comparison with the stability of the acid‐form polymers, but it was less than that of PPTA. The effect was more dramatic when the ionic groups were located at the end of side chains. The nature of the counterion also played a role, with doubly ionized calcium giving the best results. Polarized light micrographs of the ionic PPTA polymers displaced birefringent patterns and indicated that greater rigidity was present when the ionic groups were directly attached to the backbone, rather than at the end of a short side chain. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2888–2897, 2001
Influence of long‐chain branching on the miscibility of poly(ethylene‐r‐ethylethylene) blends with different microstructures
Authors: Chen Ying Ying , Lodge Timothy P. , Bates Frank S. 
Published: August 2002

AbstractThe melt miscibility of two series of poly(ethylene‐r‐ethylethylene) (PEExx) polymers with different percentages (xx) of ethylethylene (EE) repeat units was examined with small‐angle neutron scattering (SANS). The first series consisted of comb/linear blends in which the first component is a heavily branched comb polymer (B90) containing 90% EE and an average of 62 long branches with a weight‐average molecular weight (MW) of 5.5 kg/mol attached to a backbone with MW = 10.0 kg/mol. The comb polymer was blended with six linear PEExx copolymers, all of which had MW ≈ 60 kg/mol and EE percentages ranging from 55 to 90%; they were denoted L55 to L90, with the number referring to the percentage of EE repeat units. The second series consisted of linear/linear blends; the first component, with MW = 220 kg/mol and 90% EE, was denoted L90A, and the second components were the same series of linear polymers, with MW ≈ 60 kg/mol and various EE compositions. The concentrations investigated were 50/50 w/w, except for the blend of branched B90 and linear L90 (both components were 90% EE), for which 25/75 and 75/25 concentrations were also examined. The SANS results indicated that for the comb/linear blends, only the dB90/L90 blends were miscible, whereas the other five blends phase‐separated; for the linear/linear blends, dL90A/L83 and dL90A/L78 were miscible, whereas the other three blends were immiscible. These results indicate that long‐chain branching significantly narrowed the miscibility window of these polyolefin blends. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 466–477, 2002; DOI 10.1002/polb.10102
Development of a methodology to predict material properties from environmental exposure. I. Kinetic treatment
Authors: Robertson J. E. , Ward T. C. 
Published: August 2002

AbstractThis study focuses on bisphenol A polycarbonate and tracks changes in the properties of this material as a function of the degree of degradation, τ, induced by a hostile environment. Among many possible environmental effects, we have limited this investigation to those associated with elevated temperature, although the methodology is general. This τ parameter is a product of the kinetic rate constant, k, found from isothermal kinetics, and the time of degradation, t. The elucidation of τ has been linked to the measurement of the molecular weight distribution, which, in turn, can be related to various properties to yield valuable predictive relationships. Only the thermal history of the polymer and its initial properties are required for the model. This technique is not limited to a specific polymer or even to thermal degradation. As long as the kinetics of the process can be mathematically modeled, this approach should apply to a host of other situations, providing property prediction simply from knowledge of the material history. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 794–801, 2002
Effect of stereosequences on crystallinity and properties of zone‐drawn poly(vinyl alcohol) microfibrils
Authors: Lyoo Won Seok , Kim Joon Ho , Koo Kang , Lee Joon Seok , Kim Sam Soo , Yoon Won Sik , Ji Byung Chul , Kwon Ick Chan , Lee Chul Joo 
Published: August 2002

AbstractTo effectively orient the molecular chains of novel syndiotactic poly(vinyl alcohol) (PVA) microfibrillar fiber (PVA fibril), a high‐temperature zone‐drawing method was adopted. The PVA fibrils were directly prepared from the saponification and in situ fibrillation without a spinning procedure. The maximum draw ratio of the PVA fibril increased with a decrease in the syndiotactic diad (r‐diad) content, indicating that the deformability of PVA molecules was lowered in higher syndiotactic PVA. Degree of crystal orientations up to 0.990 were achieved by stretching the PVA fibril with the r‐diad content of 65.1% and the original degree of crystal orientation of 0.902 at 250 °C close to its crystal melting temperature (Tm). When the same draw ratio was applied to the fibrils, a higher crystal orientation was achieved for the fibrils having higher syndiotacticity. Wide‐angle X‐ray data show that the longitudinal crystal sizes of drawn PVA fibrils were larger in higher syndiotacticities. The degree of crystal orientation, crystallinity, Tm, longitudinal crystal size, and tensile strength of the maximum drawn PVA fibril with a r‐diad content of 65.1% were 0.99, 0.97, 279 °C, 187 Å, and 4.66 N/tex, respectively. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1263–1271, 2001
Photoviscoelastic behavior of amorphous polymers during transition from the glassy to rubbery state
Authors: Shyu G. D. , Isayev A. I. , Li C. T. 
Published: August 2002

AbstractTensile stress‐relaxation experiments with simultaneous measurements of Young's relaxation modulus, E, and the strain‐optical coefficient, Cϵ, were performed on two amorphous polymers—polystyrene (PS) and polycarbonate (PC)—over a wide range of temperatures and times. Master curves of these material functions were obtained via the time‐temperature superposition principle. The value of Cϵ of PS is positive in the glassy state at low temperature and time; then it relaxes and becomes negative and passes through a minimum in the transition zone from the glassy to rubbery state at an intermediate temperature and time and then monotonically increases with time, approaching zero at a large time. The stress‐optical coefficient of PS is calculated from the value of Cϵ. It is positive at low temperature and time, decreases, passes through zero, becomes negative with increasing temperature and time in the transition zone from the glassy to rubbery state, and finally reaches a constant large negative value in the rubbery state. In contrast, the value of Cϵ of PC is always positive being a constant in the glassy state and continuously relaxes to zero at high temperature and time. The value of Cσ of PC is also positive being a constant in the glassy state and increases to a constant value in the rubbery state. The obtained information on the photoelastic behavior of PS and PC is useful for calculating the residual birefringence and stresses in plastic products. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2252–2262, 2001
Respiratory syncytial virus bronchiolitis: Disease severity, interleukin‐8, and virus genotype*
Authors: Smyth Rosalind L. , Mobbs Kevin J. , O'Hea Una , Ashby Deborah , Hart C. Anthony 
Published: August 2002

AbstractIn infants with respiratory syncytial virus (RSV) bronchiolitis, we investigated whether disease severity is associated with the genotype of the infecting virus, or with the infant's immunological response to the infection, as determined by measurement of interleukin‐8 mRNA in the nasopharyngeal aspirate. This was a cross‐sectional observational study, performed in the Accident and Emergency Department, wards, and Intensive Care Unit of a large pediatric hospital. Participants included 276 infants with respiratory syncytial virus infection. Outcome variables included: disease severity (infants requiring oxygen or ventilation were classified as having severe disease); RSV virus genotype (determined according to typing scheme based on the nucleoprotein and G glycoprotein genes); and amount of interleukin‐8 mRNA in the nasopharyngeal aspirate, as measured by a semiquantitative polymerase chain reaction assay. This was corrected for the amount of cellular material in the sample by expressing it relative to mRNA for a constitutively expressed gene, HGPRT.We found a highly significant association between the ratio of interleukin‐8 mRNA/HGPRT mRNA in the nasopharyngeal aspirate and the occurrence of severe disease. Odds ratio per unit increase of interleukin‐8 mRNA/HGPRT mRNA was 1.15 (95% CI, 1.06, 1.24), P = 0.0004. There was no association between virus genotype and either disease severity or amount of interleukin‐8 mRNA/HGPRT mRNA.In conclusion, there is a strong, dose‐related association between interleukin‐8 mRNA produced locally in the airways and disease severity, and a lack of association with virus genotype. This suggests that clinical manifestations of respiratory syncytial virus bronchiolitis are determined by local immunological responses to infection, rather than by characteristics of the infecting virus. Pediatr Pulmonol. 2002; 33:339–346. © 2002 Wiley‐Liss, Inc.
Platelet endothelial cell adhesion molecule‐1 and capillary loading in premature infants with and without chronic lung disease*
Authors: Olsen Steven L. , Thibeault Donald W. , Mabry Sherry M. , Norberg Michael , Truog William E. 
Published: August 2002

AbstractIt was our objective to quantify platelet endothelial cell adhesion molecule‐1 (PECAM‐1) by immunohistochemistry in control infants of 22–50 weeks postconceptual age, and to correlate it with varying degrees of neonatal chronic lung disease (CLD). We tested the hypothesis that the density of PECAM‐1 staining will positively correlate with increasing gestational age (GA) and the inflammatory process in CLD. A library of postmortem lung tissue of infants receiving ventilator care was accessed. The population consisted of 35 control infants exposed briefly to oxygen and positive pressure ventilation, and 31 infants who were 23–30 weeks GA with mild to severe CLD. A monoclonal anti‐human PECAM‐1 antibody was used to stain 5‐μm paraffin sections. The slides were viewed at a magnification of × 40 by a blinded examiner. Twenty consecutive fields from standardly expanded tissue samples were viewed, and the volume density of PECAM‐1 (VV PECAM) per parenchyma was measured, using point counting. In addition, 1‐μm sections from 15 controls and 5 infants with CLD were stained with Toluidine blue and viewed under oil at a magnification of × 100, and the volume density of capillaries (VV CAP) and capillary load (CL) were calculated.The VV PECAM increased significantly with GA in controls (r = 0.72, P < 0.001). There was no relationship between VV PECAM and severity of CLD. Both VV CAP and CL increased significantly with GA (r = 0.93, P < 0.001; r = 0.94, P < 0.001, respectively). The infants with CLD had a normal or increased VV CAP and CL compared to controls.In summary, VV PECAM, VV CAP, and CL increased significantly with gestational age in control infants, but the postconceptional age range in CLD infants was too short to determine whether the VV PECAM changed. Infants with CLD had normal or increased VV CAP and CL compared to controls. The PECAM‐1 immunostain does not appear to be a sensitive method for assessing capillary density in infants with CLD. These findings of normal or increased capillary load may represent a vascular adaptation for the lack of secondary septation and decreased surface area in CLD. Pediatr Pulmonol. 2002; 33:255–262. © 2002 Wiley‐Liss, Inc.
The regulatory system for aquaculture in the Republic of Ireland
Authors: Grist Berna 
Published: August 2002

AbstractThe control of aquaculture in the Republic of Ireland falls under a number of different legislative codes and, consequently, responsibility for the regulation of the industry is divided between a number of ministers and state agencies. The principal responsibility lies with the Minister for the Marine and Natural Resources. The 1997 Fisheries Act was framed to replace an outdated regulatory system with one which would enjoy the confidence of a rapidly expanding industry and of all other relevant interests, in particular by establishing an independent authority for the determination of aquaculture licence appeals. Powers in relation to the authorisation and control of medicines are shared between the Minister for Agriculture and the Minister for Health, while local authorities are responsible for planning permission and discharge licences in respect of land‐based facilities.© 2002 Society of Chemical Industry
Biological activity of kiwifruit peel extracts
Authors: Motohashi Noboru , Shirataki Yoshiaki , Kawase Masami , Tani Satoru , Sakagami Hiroshi , Satoh Kazue , Kurihara Teruo , Nakashima Hideki , Wolfard Kristina , Miskolci Csilla , Molnár Joseph 
Published: August 2002

AbstractVarious bioactive substances in kiwifruit extracts were fractionated by organic solvent extractions, followed by silica gel and ODS chromatographies. Both cytotoxic activity and multi‐drug resistance reversal activity were found in the less polar fractions. Cytotoxic activity was not always parallel the radical intensity. Antibacterial activity was distributed into various fractions and all fractions were inactive against Candida albicans and H. pylori. Only 70% methanol extracts showed anti‐human immunodeficiency virus activity, and produced a broad ESR signal under alkaline conditions, in a fashion similar to lignin. These fractions also effectively scavenged O2− produced by the xanthine–xanthine oxidase reaction, suggesting a bimodal (pro‐oxidant and antioxidant) action. These data suggest a medicinal efficacy of kiwifruit peel extracts. Copyright © 2001 John Wiley & Sons, Ltd.
Imperfect inspection of a multi‐attribute deteriorating production system—a continuous time model
Authors: Rabinowitz Gad , Yahalom Orly 
Published: August 2002

AbstractThe reliability of a multi‐attribute deteriorating production system is controlled using versatile identical inspection facilities. An attribute state is dichotomous (up designates proper function versus down). A product item is conforming if all the system attributes are up when it is produced. When a system attribute is detected as down it is restored back to an up state. Inspection of an attribute can rely on observations of the system, recently produced items, or both. Inspection policy determines the inspection capacity, frequency of inspecting each attribute and inspection schedule. These decisions involve a tradeoff between the cost of inspectors and the loss associated with the roportion of non‐conforming items due to lack of adequate inspection. Three models are introduced, analyzed and solved. In the first model, inspection and restoration are perfect, product attribute is up (down) when the system attribute is up (down), and restoration is immediate. The assumptions of perfect inspection and restoration are relaxed in the second model. The third model relaxes in addition the assumption of immediate restoration. An efficient heuristic solution scheme is provided for solving these models. Sensitivity of the solution to system parameters is studied. Numerical experiments provide some insights regarding the combined effect of imperfect production, inspection and restoration, in various conditions of inspection and restoration durations. Copyright © 2001 John Wiley & Sons Ltd.
Structural and electronic properties of La‐doped CaTiO3 crystal
Authors: Erazo Franklin , Stashans Arvids 
Published: August 2002

AbstractThere is experimental and computational evidence that some important properties such as electrical conductivity and ferroelectricity in the CaTiO3 crystal change according to the dopant states. Using an INDO quantum‐chemical computational method modified for crystal calculations we explore the stability of the La‐doped CaTiO3 crystal in both phases, cubic and orthorhombic. The calculations are carried out by means of the supercell model based on the LUC (large unit cell) approach as it is implemented into the CLUSTERD computer code. The equilibrium geometry for impurity is found together with the crystalline lattice distortions. Atomic displacements and relaxation energies are analyzed in a comparative manner for the two crystallographic phases. A new effect of electron transfer from the local one‐electron energy level within the band‐gap to the conduction band is observed. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Vacancy interactions in cluster expansion formalism
Authors: Fuks David , Dorfman Simon 
Published: August 2002

AbstractVacancies in metal are studied in the model of the atom‐vacancy solid solution. Vacancy formation energy is discussed in terms of cluster expansion formalism. It is shown that effective interaction of vacancies is formally included in the energy of vacancy formation. The cluster expansion method illustrates that pairwise and nonpairwise interactions between atoms and vacancies are responsible for the interaction of vacancies in the atom‐vacancy solid solution. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Metal‐assisted esterification: glutaric acid–iron(II) complexes in the gas phase
Authors: Lee Yong‐III , Jo Sung‐Chan , Tao W. Andy , Cooks R. Graham 
Published: August 2002

AbstractTransition metal ions are routinely used to assist organic reactions; however, direct detection of the intermediates in such reactions is uncommon. Here, we demonstrate a transition metal ion‐assisted reaction between glutaric acid (L) and methanol, using electrospray ionization mass spectrometry (ESI‐MS). Esterification of glutaric acid does not occur in aqueous methanol solution under ESI conditions, but the FeII‐bound acid cluster, [FeIIL2 − H]+, adds methanol and dehydrates to give rise to an abundant product ion with a 14 Da increased mass. The occurrence of methyl esterification is supported by collision‐induced dissociation and isotopic labeling data, which indicate that the sequence by which the product ion is generated is loss of water, followed by the addition of methanol. Electrospray ionization conditions, specifically the tube lens offset voltage, strongly affect the reaction efficiency, presumably through control of the dehydration process. Other transition metal ions, such as NiII, ZnII, CoII and CuII, also show distinctive metal‐assisted reactions. Copyright © 2001 John Wiley & Sons, Ltd.