bluuebunny/crossref_metadata_2025_split huggingface dataset:
Persistent spectral hole‐burning study on dendrimer porphyrins
Authors: Machida Shinjiro , Sugihara Koichi , Takahashi Isoko , Horie Kazuyuki , Jiang Dong‐Lin , Aida Takuzo 
Published: August 2002

AbstractWe report the first results of persistent spectral hole burning of dendrimer porphyrins having three‐, four‐, or five‐layered aryl ether dendritic arrays. We evaluate structural relaxations of dendrimer framework around the porphyrin core at low temperatures. A large environmental change around the porphyrin core, as evaluated from the hole area, was suppressed in dendrimer porphyrins of higher generation numbers, whereas a small environmental change, as evaluated from hole width, showed no dependence on the number of generations. The dendrimer porphyrins showed sharp holes at 20 K, suggesting a long dephasing time and the suppression of spontaneous spectral diffusion. The results of dendrimer‐embedded polymer sample indicated that the structural relaxation of polymer chain outside the dendrimer does not have an influence on the resonant frequency of the porphyrin core. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 210–215, 2002
Approach for the calculation of high‐order connectivity indices of polymers and its application
Authors: Zhong Chongli , Yang Chunsheng 
Published: August 2002

AbstractA method for the calculation of connectivity indices of polymers was developed that can be used to calculate any order connectivity indices of polymers in a consistent and unambiguous manner without any truncation errors. The proposed method makes it possible to correlate the physical properties of polymers in terms of connectivity indices of higher than first order, which may not only improve the correlation and prediction accuracy but also possibly eliminate the normally required atomic and group correction terms to develop more general correlations with reliable predictive capability. As an example, two correlations with connectivity indices up to the third order are proposed to correlate the thermal conductivities at room temperature for 20 amorphous polymers. The two proposed correlations give comparable or even better accuracy than the existing one, which requires connectivity indices up to the first order and an atomic correction term. Because only connectivity indices were used in the newly proposed correlations, they are general models with better predictive capability. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 401–407, 2002; DOI 10.1002/polb.10104
Effect of compression on the solid polymer electrolytes: The modified lattice‐fluid model
Authors: Young Ahn Woo , Bae Young Chan 
Published: August 2002

AbstractA molecular thermodynamic model based on the theory of melting point depression, the Adam–Gibbs configurational entropy model, and the modified lattice‐fluid model was developed to interpret ionic conductivities of solid polymer electrolytes with various pressures. A new configurational entropy, S was introduced in this model. Quantitative descriptions according to the proposed model agreed with the experimental data for the given systems. Our results showed that a eutectic point moves toward higher melting temperatures, whereas a lower weight fraction of salt and the ionic conductivity significantly decrease with pressure. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 706–713, 2002
Lactone ring formation in poly(α‐hydroxyacrylic acid)
Authors: Yamazawa Kazuyoshi , Kawauchi Susumu , Satoh Mitsuru 
Published: August 2002

AbstractLactone ring formation in poly(α‐hydroxyacrylic acid) (PHA) was investigated by means of 1H and 13C NMR. The stereoregularity of PHA was estimated as syndio‐rich (ca. 86%) on the basis of methylene proton peak of the sodium salt, PHANa, in aqueous solution. On the other hand, analyses of the 13C NMR spectra obtained as a function of the degree of dissocation (α) suggested that the lactone ring is formed at every other residue at half dissociation (α = 0.5). This specific way of lactone formation supposed for PHA is discussed in relation to the critical change in the dissociation behavior of the polyacid which has been found at α = 0.5. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1400–1405, 2002
Molecular dynamics study of the stereostructure of 1,4‐linked poly(cyclohexa‐1,3‐diene) obtained with π‐allylnickel‐based catalysts
Authors: Tanimura Shinobu , Matsuoka Takaaki , Nakano Mitsuru , Usuki Arimitsu 
Published: August 2002

AbstractTemperature‐constant and pressure‐constant molecular dynamics simulations of crystalline 1,4‐linked poly(cyclohexa‐1,3‐diene) (CHD) were performed using the COMPASS force field. Powder X‐ray diffraction spectra calculated from the simulated atomic coordinates were compared with the measured spectrum of the crystal of 1,4‐linked poly(CHD), obtained using a bis(allylnickel bromide) (ANiBr)/methylaluminoxane (MAO) catalyst. As a result of the comparison, the geometrical isomerism of the 1,4‐linked poly(CHD) obtained with the ANiBr/MAO catalyst was found to be cis syndiotactic. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 973–978, 2001
Induced changes of polymer organization in a gel of poly(vinyl alcohol) crosslinked by Congo red
Authors: Atkin N. J. , Abeysekera R. M. , Chenery D. H. , Robards A. W. 
Published: August 2002

AbstractDifferent gel microstructures are induced at variable poly(vinyl alcohol) (PVA) and Congo red concentrations, as revealed by ultrarapid freezing and a replica technique for transmission electron microscopy. The polymer microstructures observed include random coils, rigid polymer rods, and long fibers. The development of the different polymer conformations is proposed to be dependent on the degree of intramolecular and intermolecular crosslinking and on the electrostatic interactions of the Congo red ions. The rigid‐rod conformation appears to be the most energetically stable form; it is disrupted by electrostatic effects around the polymer overlap concentration (C*PVA). We propose that the gel microstructure influences the physical properties of the gel. Gels possessing the rigid‐rod microstructure have increased Young's storage modulus values. Two possible mechanisms of gelation are suggested. The first describes a one‐stage reaction when the polymer concentration approximates C*PVA, where polymers in an extended random‐coil conformation undergo intermolecular crosslinking without any microstructural changes. The second describes a two‐stage reaction when the polymer concentration is less than or greater than C*, where a disorder–order transition results in the formation of rigid polymer rods and fibers followed by the formation of a macromolecular network. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1471–1483, 2001
A novel approach to the determination of the crosslink density in rubber materials with the dipolar correlation effect in low magnetic fields
Authors: Garbarczyk Maciej , Grinberg Farida , Nestle Nikolaus , Kuhn Winfried 
Published: August 2002

AbstractWe present a novel NMR approach to the determination of crosslink densities in rubber materials. The method is based on the dipolar correlation effect (DCE) on the stimulated echo examined in a series of rubber samples and linear polyisoprene. The parameter evaluated from the echo attenuation curves is the mean‐squared dipolar fluctuation associated with anisotropic reorientations of macromolecular backbones. The contributions to the DCE of the constraints due to excluded volume effects and chemical crosslinks are estimated. A strong dependence of the mean‐squared dipolar fluctuation on the crosslink density of rubber combined with the simplicity of performing the measurements with inexpensive low‐field instruments suggests that the DCE is a useful tool for routine applications. The potential and problems of performing DCE measurements in low‐magnetic‐field conditions are discussed in detail. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2207–2216, 2001
Size asymmetry in diblock copolymers of cylindrical morphology in thin films
Authors: Suh K. Y. , Lee Hong H. 
Published: August 2002

AbstractWe calculate the free energy of an AB diblock copolymer thin film of cylindrical morphology under confined geometry and find that the size of the cylinder can be asymmetric, depending on the film thickness and surface tension. The size of the cylinder right above the surface is slightly smaller than that of the other cylinders. The equilibrium period in this thin film is different from that in the bulk because of the surface effect. The tendency toward asymmetry diminishes as the film thickness increases and the interfacial tension between the major block (A) and the substrate decreases. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2217–2224, 2001
In‐line monitoring of immiscible polymer blends in a rheometer with a fiber‐optics‐assisted fluorescence detection system
Authors: Vorobyova Olga , Winnik Mitchell A. 
Published: August 2002

AbstractIn‐line studies of the initial stages of shear‐induced coalescence in two‐phase polymer blends were carried out with a home‐built device combining a cone and plate rheometer and a fiber‐optic‐assisted fluorescence detection system. A blend of 90 wt % poly(2‐ethylhexyl methacrylate) (PEHMA) and 10 wt % poly(butyl methacrylate) (PBMA) was prepared by the casting of films onto a solid substrate from mixed aqueous latex dispersions of the two polymers. The dispersions were prepared via emulsion polymerization under conditions in which both components were formed as spherical particles with a very narrow size distribution. By using a 14:1 particle ratio of PEHMA to PBMA, we obtained films in which 120‐nm PBMA particles were surrounded by a PEHMA matrix. The blend contained phenanthrene‐labeled PBMA particles and anthracene‐labeled PBMA particles in a ratio of 4:1, whereas the PEHMA matrix polymer was unlabeled. We monitored the anthracene‐to‐phenanthrene fluorescence intensity ratio (I470/I360) as a measure of direct nonradiative energy transfer from phenanthrene to anthracene, whereas the blend was sheared at different shear rates and temperatures. Under no‐shear conditions, the results of in‐line experiments were in good agreement with the results of off‐line measurements of energy transfer by conventional techniques. In blends under shear, the two sets of experiments, in‐line and off‐line, did not agree with each other. The cause of this disagreement was associated with normal forces in the blend under shear that affected the optical path length and the relative intensities of the fluorescence signals of the phenanthrene and anthracene groups in the blend. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2302–2316, 2001
A note on the ice crystallography and geochemistry of a debris cone, Northern Foothills, Antarctica
Authors: Guglielmin Mauro , Camusso Marina , Polesello Stefano , Valsecchi Sara , Teruzzi Mario 
Published: August 2002

AbstractAn ice‐core collected in November 1996 from a debris cone near Amorphous Glacier, not far from the PNRA Terra Nova Bay Station, Antarctica, was analysed crystallographically and chemically. Based upon the shape, size and orientation of the c‐axes of the ice crystals, and the occurrence of gas and mineral inclusions, several different layers were distinguished. They indicate episodes of water congelation under different kinetic and thermodynamic conditions. These findings suggest the Amorphous debris cone is a frost‐heaved mound and not the product of glacier differential ablation. Copyright © 2002 John Wiley & Sons, Ltd.
Enhanced release of thromboxane A2 after exposure of human airway epithelial cells to meconium
Authors: Khan Amir M. , Lally Kevin P. , Larsen Gary L. , Colasurdo Giuseppe N. 
Published: August 2002

AbstractMeconium aspiration syndrome (MAS) is a cause of significant morbidity and mortality in the perinatal period. Despite the clinical relevance of MAS, its pathogenesis is poorly understood. Epithelial cell‐derived prostanoids are involved in the regulation of several cellular functions within the lung, including the control of tone and reactivity of airway and vascular smooth muscle. In this study, we evaluated whether exposure to meconium affects the metabolic function of human airway epithelial cells. Monolayers of A549 cells, a transformed human epithelial cell line, were incubated with various concentrations of meconium. Control cells were incubated with serum‐free medium in a similar manner. The supernatant fluid was removed at various time points and assayed for thromboxane A2 (TXA2) production. The latter was accomplished by measuring its immediate and stable metabolite thromboxane B2, using an enzyme‐linked immunosorbent assay (ELISA). In selected experiments, the modulatory effects of indomethacin (10− 6 M), dexamethasone (10− 6 M), and L‐nitroarginine methyl ester (L‐NAME, 10− 6 M) on TXA2 production were evaluated. Results were expressed in terms of pg/mg protein (mean ± SE).We found that exposure to meconium produced a significant release of TXA2 from A549 cells. Indomethacin, dexamethasone, and in part, L‐NAME inhibited meconium‐induced release of TXA2.Our findings demonstrate that meconium enhances the production of thromboxanes from A549 cells, suggesting that airway epithelial cells and their metabolic products may play an important role in the pathogenesis of MAS. Pediatr Pulmonol. 2002; 33:111–116. © 2002 Wiley‐Liss, Inc.
Assessment of a low‐cost home monitoring spirometer for children*
Authors: Bastian‐Lee Yvonne , Chavasse Richard , Richter Hazel , Seddon Paul 
Published: August 2002

AbstractElectronic devices are now available to measure and store lung function parameters in the home. Before adopting a device for clinical or research use, it is important to validate it in the target patient group. The aim of this study was to assess a low‐cost, portable, logging spirometer, the VM Plus (VM), against a standard laboratory Jaeger spirometer (JS) for use in children with respiratory disease. Seventy children with stable asthma or cystic fibrosis performed spirometry on the two devices, and results for peak expiratory flow (PEF) and forced expiratory volume in 1 sec (FEV1) were compared. Comparison was made both using the two devices separately (separate method) and with the devices connected in series (series method). Reproducibility of the VM measurements was also assessed.Correlation between measurements was close (R values: separate, PEF, 0.91; FEV1, 0.94; series, PEF, 0.97, FEV1, 0.99), but PEF readings on the VM Plus were substantially higher than with the JS (mean difference: separate, 54.8 L/min; series, 28.2 L/min). This reflects well‐reported differences in PEF measurements between the Mini‐Wright PEF meter, on which the VM Plus spirometer is based, and conventional spirometers. Limits of agreement (series method) were: PEF, −13.2 to +69.6 L/min; FEV1, −0.03 to +0.19 L. Reproducibility of VM Plus measurements was acceptable: coefficient of variation for PEF was 4%; for FEV1, 4.3%; coefficient of reproducibility for PEF, 39 L/min; for FEV1, 0.26 L.The VM Plus provides reasonably accurate, reproducible measurements of PEF and FEV1, but intrinsic bias, particularly in PEF measurement, needs to be taken into account. Its potential to document longitudinal changes in lung function in children with respiratory disease at home merits further study. Pediatr Pulmonol. 2002; 33:388–394. © 2002 Wiley‐Liss, Inc.
Effects of dexamethasone on proliferation, chemotaxis, collagen I, and fibronectin‐metabolism of human fetal lung fibroblasts
Authors: Brenner R.E. , Felger D. , Winter C. , Christiansen A. , Hofmann D. , Bartmann P. 
Published: August 2002

AbstractPremature infants at risk for bronchopulmonary dysplasia (BPD) are often treated with dexamethasone (Dex), which has been shown to suppress inflammatory processes in the lung. To elucidate a possible direct influence on the fibroproliferative component of the disease, we studied the effects of Dex in therapeutic and supratherapeutic dosages (5–50 nmol/L) on proliferation, chemotaxis, procollagen I, and fibronectin metabolism of human fetal lung fibroblasts in vitro.Proliferation was inhibited by Dex in a dose‐dependent manner. Chemotactic activity in response to conditioned medium of human fetal fibroblasts also showed a dose‐dependent inhibition after pretreatment with Dex. The amount of procollagen I C‐terminal propeptide and fibronectin per cell in the cell culturesupernatant was increased in the presence of Dex.Our results show that Dex does not uniformly suppress the fibroproliferative activity of human fetal lung fibroblasts, which may explain in part the unsatisfactory long‐term effects of Dex treatment in BPD. Pediatr Pulmonol. 2001; 32:1–7. © 2001 Wiley‐Liss, Inc.
Efficacy and safety of aerosolized tobramycin in cystic fibrosis
Authors: Pai Vinita B. , Nahata Milap C. 
Published: August 2002

AbstractAerosolized tobramycin has been extensively used in cystic fibrosis (CF) patients in order to directly deliver the antibiotic to the endobronchial site of infection, and decrease toxicity by limiting systemic absorption. Aerosolized tobramycin doses ranging from 80 mg twice or three times daily to 600 mg three times daily have been used in various clinical trials. At an 80‐mg dose, preservation of pulmonary function with little or no improvement over the baseline was reported. Tobramycin, nebulized at 600 mg three times daily, significantly improved clinical and pulmonary functions and reduced the density of Pseudomonas aeruginosa in the sputum. No ototoxicity or nephrotoxicity was reported at either dose.TOBI®, a tobramycin solution for inhalation, received Food and Drug Administration approval for maintenance treatment of P. aeruginosa lung infections in CF patients at least 6 years of age. Patients received TOBI® nebulize 300 mg of tobramycin every 12 hr daily for 28 days, followed by 28 days off the drug in alternating cycles. In phase III trials, TOBI® improved pulmonary function and decreased sputum density of P. aeruginosa compared to placebo. Serum creatinine was minimally, transiently elevated in both groups. More patients in the TOBI® group reported voice alterations. All reports of tinnitus were in the TOBI® group. An increased risk of emergence of resistant strains of P. aeruginosa was noted at all doses, after prolonged use. Pediatr Pulmonol. 2001; 32:314–327. © 2001 Wiley‐Liss, Inc.
Acute respiratory distress syndrome due to cyanotic spell in an infant with tetralogy of Fallot
Authors: Grech Victor , Goldman Alan 
Published: August 2002

AbstractAcute respiratory distress syndrome (ARDS) is characterized by fulminant respiratory failure due to noncardiac pulmonary edema. This can be triggered by a heterogeneous group of diseases. We report an unusual case of an infant who developed severe ARDS in association with a severe cyanotic attack due to tetralogy of Fallot. Pediatr Pulmonol. 2001; 32:406–407. © 2001 Wiley‐Liss, Inc.
Lysophosphatidic acid stimulates proliferation of cultured smooth muscle cells from human BPH tissue: Sildenafil and papaverin generate inhibition
Authors: Adolfsson Per I. , Ahlstrand Christer , Varenhorst Eberhard , Svensson Samuel P.S. 
Published: August 2002

AbstractBackgroundThe endogenous substance lysophosphatidic acid (LPA) has been found to generate proliferation of cultured smooth muscle cells (SMC). Therefore, the effect of LPA on human benign prostate hyperplasia (BPH) could be of interest.MethodsThe proliferative effect of LPA on cultured human prostatic SMC from specimens obtained at trans‐urethral resection of the prostate (TURP) because of BPH, was analyzed by [3H]‐thymidine and [35S]‐methionine incorporation. In addition, LPA stimulated BPH SMC were treated with papaverin, forskolin, sildenafil or zaprinast, well known to increase the intracellular level of cAMP or cGMP.ResultsLPA produced a dose‐dependent increase in BPH SMC, both regarding DNA‐ and protein‐synthesis with EC50 values of 3 and 10 μM, respectively. Furthermore, both papaverin, a general phosphodiesterase inhibitor regarding cAMP hydrolyzes, and forskolin, an adenylyl cyclase stimulating agent, inhibited the LPA‐stimulated DNA replication in a dose dependent manner with IC50 = 2.5, and 0.35 μM, respectively. cGMP increasing agents, such as the NO‐donors SIN‐1 and SNAP, produced a weak anti‐proliferative response. However, both phosphodiesterase 5 inhibitors sildenafil (Viagra®) and zaprinast efficiently blocked DNA replication. In addition, when the protein synthesis was examined, we found that the LPA response was significantly inhibited by forskolin and papaverin.ConclusionsThe major conclusion of this investigation is that the endogenous serum component LPA, is able to promote human BPH SMC growth. In addition, our study indicates that cyclic nucleotides can inhibit this effect. Future clinical studies will be needed to determine if different specific phosphodiesterase inhibitors per se or in combination could represent a new therapeutic possibility for the treatment of BPH. Prostate 51:50–58, 2002. © 2002 Wiley‐Liss, Inc.
GSTA1 expression in normal, preneoplastic, and neoplastic human prostate tissue
Authors: Parsons J. Kellogg , Nelson Chad P. , Gage Wesley R. , Nelson William G. , Kensler Thomas W. , De Marzo Angelo M. 
Published: August 2002

AbstractBACKGROUNDGlutathione S‐transferases (GSTs), inducible enzymes that catalyze the detoxification of reactive electrophiles and oxidants, protect against neoplastic transformation. Prostatic adenocarcinoma and high‐grade prostatic intraepithelial neoplasia (HGPIN) fail to express GSTP1, a major class of GST. This failure of expression is associated with methlyation of the GSTP1 promoter, a somatic alteration proposed to be a critical step in prostatic carcinogenesis. However, simple atrophy and post‐atrophic hyperplasia—proliferative lesions associated with chronic inflammation, which we have termed “proliferative inflammatory atrophy” (PIA)—express elevated levels of GSTP1. We postulated that this increase in GSTP1 expression in PIA occurs in response to increased oxidative stress. We examined the expression of another major class of GST, GSTA1, in the human prostate.METHODSWe performed immunohistochemistry against GSTA1 on formalin‐fixed radical prostatectomies (n = 45). A stereological grid point counting method was used to estimate the percent of cells staining positive for GSTA1 in normal prostate, PIA, HGPIN, and adenocarcinoma.RESULTSIn contrast to GSTP1, normal peripheral zone epithelium was virtually devoid of GSTA1. Strikingly, though, epithelial cells in PIA demonstrated strong staining for GSTA1 (median of percent of cells staining positive = 44) as compared to those in normal peripheral zone (median = 3.0, P < .00001), HGPIN (median = 2.9, P < .00001), and adenocarcinoma (median = 3.8, P < .00001). Variations in GSTA1 were also detected between normal anatomic zones: the central zone showed an increase in the percentage of cells staining positive (median = 20.9) as compared to the transition (median = 0.47, P < .0002) and the peripheral (P < .0001) zones.CONCLUSIONSExpression of GSTA1 is increased in PIA, supporting the concept that cells within these lesions are subject to localized increases in oxidative stress. Low levels of GSTA1 and GSTP1 in HGPIN and adenocarcinoma suggest a broad lack of detoxification activity in these cells, which may be associated with carcinogenesis in the prostate. Prostate 49:30–37, 2001. © 2001 Wiley‐Liss, Inc.