bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hyperbranched aromatic poly(ether imide)s: Synthesis, characterization, and modification
Authors: Wu Fang‐Iy , Shu Ching‐Fong 
Published: August 2002

AbstractThe synthesis and characterization of hyperbranched aromatic poly(ether imide)s are described. An AB2 monomer, which contained a pair of phenolic groups and an aryl fluoro moiety activated toward displacement by the attached imide heterocyclic ring, was prepared. The nucleophilic substitution of the fluoride with the phenolate groups led to the formation of an ether linkage and, subsequently, to the hyperbranched poly(ether imide), which contained terminal phenolic groups. A similar one‐step polymerization involving a monomer that contained silyl‐protected phenols yielded a hyperbranched poly(ether imide) with terminal silylated phenols. The degree of branching of these hyperbranched polymers was approximately 55%, as determined by a combination of model compound studies and 1H NMR integration experiments. End‐capping reactions of the terminal phenolic groups were readily accomplished with a variety of acid chlorides and acid anhydrides. The nature of the chain‐end groups significantly influenced physical properties, such as the glass‐transition temperature and the solubility of the hyperbranched poly(ether imide)s. As the length of the acyl chain of the terminal ester groups increased, the glass‐transition temperature value for the polymer decreased, and the solubility of the polymer in polar solvents was reduced, becoming more soluble in nonpolar solvents. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2536–2546, 2001
Synthesis of carboxy‐telechelic oligostyrene by dead‐end polymerization: Evaluation of primary radical termination by kinetic study and kinetic simulation model
Authors: David Ghislain , Robin Jean‐Jacques , Boutevin Bernard 
Published: August 2002

AbstractStyrene was polymerized with azobiscyanovaleric acid (ACVA) to obtain carboxy‐telechelic polystyrene. Our aim was to synthesize an oligostyrene with a molecular weight of about 2000 g/mol. Thus, styrene was polymerized at 90 °C, where t1/2ACVA is very short, and at very high initiator concentrations. In these conditions a new termination reaction appeared, known as the primary radical termination (PRT). At first, PRT was observed by a deviation from the simple kinetic law. Then, the constant of PRT was determined by several kinetic models to be more important than the constant of bimolecular termination. Finally, the PREDICI simulation program was used to confirm the predominance of PRT. This simulation program allowed the determination of the constant of primary radical deactivation krr and the influence of this reaction on the conversion rate. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2740–2750, 2001
Mechanism of emulsion polymerization of styrene using a reactive surfactant
Authors: Wang X. , Sudol E. D. , El‐Aasser M. S. 
Published: August 2002

AbstractThe emulsion polymerization of styrene using the reactive surfactant sodium dodecyl allyl sulfosuccinate (TREM LF‐40) was studied. The polymerization kinetics were found to be unusual in that Rp was not directly proportional to Np (Rp ∝ Np0.67). Several reasons are stated to explain the unusual kinetics, including chain transfer to TREM LF‐40, copolymerization of styrene with TREM LF‐40, and the influence of the homopolymer of TREM LF‐40 [poly(TREM)] and/or the copolymer [poly(TREM‐co‐styrene)] on the entry and exit rates of free radicals. The possibility of both chain transfer and copolymerization exists primarily at the oil/water interface, whereas both can also occur in the aqueous and monomer phases. Bulk polymerizations of styrene in the presence of TREM LF‐40 and poly(TREM) were conducted, and the results show that the reaction rate decreased for the styrene/TREM LF‐40 system. Latex characterization by serum replacement and titration measurements provided evidence for the chemical bonding of TREM LF‐40 to the polymer particles. The fraction of chemically bound reactive surfactant decreased with increasing surfactant concentration and increased with increasing initiator concentration. Relatively high contact angles of water on films cast from the latexes showed that TREM LF‐40 did not migrate significantly to the surface of the film, which was consistent with the latex‐surface characterization results. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3093–3105, 2001
Adhesive and mechanical properties of soft nanocomposites: Model studies with blended latex films
Authors: Fabbroni Elizabeth F. , Shull Kenneth R. , Hersam Mark C. 
Published: August 2002

AbstractWe used a unique approach based on contact mechanics to quantify the adhesive and linear viscoelastic properties of latex films approximately 100 μm thick. The latex films were formed from a mixture of two particle types and form stable films consisting of rigid and compliant regions. We used atomic force microscopy to verify that these regions remained well dispersed on the length scale of the original particle size. The properties of the films were determined by ϕh, the volume fraction of the stiffer component. For ϕh < 0.45, the films were quite adhesive, with viscoelastic properties determined by the compliant matrix material. Adhesive interactions between the film and indenter enabled us to oscillate the indenter in the direction normal to the film surface while maintaining a constant contact area, allowing us to determine the frequency dependence of the dynamic moduli of the films. Stiffer films with higher volume fractions of hard particles were characterized by indentation measurements, from which we were able to determine the time dependence of the relaxation modulus of the latex films. All results were consistent with a power‐law form of the relaxation modulus with an exponent of 0.25. The magnitude of the relaxation modulus increased by a factor of 3000 as the volume fraction of hard particles increased from 0 to 0.89. For low values of ϕh, the composition dependence of the film stiffness was similar to the concentration dependence of the viscosity of spherical particle suspensions. A much weaker concentration dependence was observed for the highest values of ϕh, where the properties of the films were dominated by the stiffer component. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 3090–3102, 2001
Dynamic evolution of gases in the γ‐ and helium‐ion radiolyses of solid polymers
Authors: Chang Z. , Laverne Jay A. 
Published: August 2002

AbstractThe dynamic evolution of gaseous hydrogen, methane, and carbon dioxide in the γ‐ and 4He‐ion radiolyses of solid polymers was investigated. The polymers used include low‐density and high‐density polyethylene, polypropylene, polystyrene, poly(methyl methacrylate), Nylon 11, Nylon 6, and poly(dimer acid‐co‐alkyl polyamine). An inline quadrupole mass spectrometer was utilized to monitor the dynamic profiles of the gases produced in the radiolysis. One‐ and two‐dimensional numerical diffusion models were developed to simulate and extract optimum diffusion coefficients and gas yields from the experimental dynamic gas profiles. It was found that the dynamic evolution of molecular hydrogen from the bulk polymer is controlled by its diffusion in most cases, such as CO2 in poly(methyl methacrylate). In the γ radiolysis of some polymers such as low‐density polyethylene and polypropylene, the dynamic evolution of methane is only partially controlled by the diffusion process, and some other postirradiation process is a factor. It is concluded that the simulation method developed in this article is helpful in understanding and predicting the mechanisms of gas evolution in the radiolysis of solid polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci B Part B: Polym Phys 39: 1449–1459, 2001
Characterization of chemical heterogeneity in polymer systems using hydrolysis and tapping‐mode atomic force microscopy
Authors: Raghavan D. , Gu X. , Nguyen T. , Vanlandingham M. 
Published: August 2002

AbstractCharacterization of polymer coatings microstructure is critical to the fundamental understanding of the corrosion of coated metals. An approach for mapping the chemical heterogeneity of a polymer system using chemical modification and tapping‐mode atomic force microscopy (TMAFM) is demonstrated. This approach is based on the selective degradation of one of the phases in a multiphase polymer blend system and the ability of TMAFM to provide nanoscale lateral information about the different phases in the polymer system. Films made of a 70:30 polyethyl acrylate/polystyrene (PEA/PS) blend were exposed to a hydrolytic acidic environment and analyzed using TMAFM. Pits were observed to form in the PEA/PS blend films, and this degradation behavior was similar to that of the PEA material. Using these results, the domains in the 70:30 blend were identified as the PS‐rich regions and the matrix as the PEA‐rich region. This conclusion was confirmed by Fourier transform infrared‐attenuated total reflection analyses that revealed the hydrolysis of the PEA material. TMAFM phase imaging was also used to follow pit growth of the blend as a function of exposure time. The usefulness of the chemical modification/AFM imaging approach in understanding the degradation process of a coating film is discussed. © 2001 John Wiley & Sons, Inc. J Polym Sci B Part B: Polym Phys 39: 1460–1470, 2001
Selective fiberoptic left main‐stem intubation for severe unilateral barotrauma in a 24‐week premature infant
Authors: Meyer Michael T. , Rice Tom B. , Glaspey John C. 
Published: August 2002

AbstractA 24‐week premature infant developed severe right‐sided pulmonary barotrauma secondary to mechanical ventilation for respiratory distress syndrome (RDS). High‐frequency oscillatory ventilation and permissive hypercapnia were initiated. A chest tube was placed to relieve a pneumothorax, and a catheter was inserted into an air‐filled cyst for drainage. These maneuvers failed to improve the child's respiratory status.The child's left main‐stem bronchus was then successfully fiberoptically intubated for single‐lung ventilation in order to reduce the unilateral barotrauma. Single‐lung ventilation was effectively and safely continued for 5 days, with complete resolution of the pulmonary barotrauma. Pediatr Pulmonol. 2002; 33:227–231. © 2002 Wiley‐Liss, Inc.
Determinants of bronchial responsiveness to methacholine at school age in twin pairs
Authors: Nikolajev Kari , Korppi Matti , Remes Kyllikki , Länsimies Esko , Jokela Veikko , Heinonen Kirsti 
Published: August 2002

AbstractThe methacholine inhalation challenge test (MIC) was used to evaluate bronchial responsiveness in 67 children who were the products of multiple pregnancies when they were 7–15 years old.At birth, 30 (45%) infants had intrauterine growth retardation (IUGR; birth weight < 2 SD below normal birth weight, or birth weight difference > 1.3 SD between twin‐pairs), and 59 (88%) were born before 37 weeks of gestation. None of the children had doctor‐diagnosed asthma. The provocative dose of methacholine causing a 20% fall in Wright's peak expiratory flow (WPEF) (PD20) was below 1,000 μg in 10 (15%) children, and they were classified as MIC responders. There were no differences in perinatal or neonatal factors between MIC responders and nonresponders; in particular, MIC responses did not differ between IUGR infants, and children with appropriate growth for gestational age (AGA) at birth. There were seven discordant pairs in which one child was a MIC responder and the other was not; 5 responders were IUGR, and 2 were AGA children (ns). Respiratory tract infections after the neonatal period were equally common in IUGR and AGA children. However, these infections were associated with later bronchial hyperresponsiveness. Doctor‐diagnosed respiratory infections, numbers of antibiotic courses, episodes of otitis media, and the need for adenoidectomy, tonsillectomy, and tympanostomy were more common in MIC responders than in nonresponders.We conclude that IUGR was not associated with subsequent bronchial hyperresponsiveness in twin pairs assessed by the MIC test. A significant relationship was seen between bronchial hyperresponsiveness and infections after the neonatal period. Pediatr Pulmonol. 2002; 33:167–173. © 2002 Wiley‐Liss, Inc.
Impact of a multidisciplinary day program on disease and healthcare costs in children and adolescents with severe asthma: A two‐year follow‐up study
Authors: Bratton Donna L. , Price Marcella , Gavin Leslie , Glenn Karen , Brenner Manon , Gelfand Erwin W. , Klinnert Mary D. 
Published: August 2002

AbstractFor patients whose asthma remains in poor control necessitating high utilization of medical services, a referral to a specialized “center of excellence” is often considered. A decade ago, we evaluated our pediatric asthma program of long‐term hospitalization (median stay of 75 days) and found significant decreases in subjects' medical utilization following this intervention. In an effort to contain treatment costs, the former program was markedly altered to one of abbreviated stay with emphasis on family management of asthma. The purpose of the present study was to determine the outcome of children treated in the revised program with regard to disease severity, quality of life, and subsequent utilization of medical resources. Children with severe asthma who were admitted to the program and fulfilled study criteria were consecutively enrolled. Data was obtained concerning disease characteristics, treatment, and quality of life at admission, and at 1 and 2 years following discharge. Medical records for the year prior to program admission and for the 2 years following discharge were coded for medical care encounters.Ninety‐eight children, aged 9 months to 18 years (mean age, 10.9 years), were enrolled. They participated in the program for a mean of 15.6 ( ± 8 SD), median of 15.0, and range of 2–51 treatment days. The group showed significant improvement (P < 0.0001) from admission to 1‐ and 2‐year follow‐up in median corticosteroid use, asthma functional severity, perceived competence in asthma management, and quality of life for both caregiver and child. Medical record data showed significant improvement (P < 0.0001) at both 1‐ and 2‐year follow‐up in median number of corticosteroid bursts, emergency department visits, hospital days, and overall utilization of medical care encounters. A median total medical encounter cost/patient of $16,250 ($6,972–$25,714 interquartile range (IQR)) for the year prior to program participation was reduced to $1,902 ($505–$6,524 IQR) at 1‐year and $690 ($185–$3,550 IQR) at 2‐ year follow‐up (P < 0.0001).We conclude that multidisciplinary care in a short‐term, outpatient, day treatment program can significantly contribute to improvement in asthma severity, quality of life, and reduction in healthcare costs. Pediatr Pulmonol. 2001; 31:177–189. © 2001 Wiley‐Liss, Inc.
Effect of acidic phospholipids on the structural properties of recombinant cytosolic human glyoxalase II
Authors: Scirè Andrea , Saccucci Franca , Bertoli Enrico , Cambria Maria Teresa , Principato Giovanni , D'Auria Sabato , Tanfani Fabio 
Published: August 2002

AbstractA peculiar characteristic of highly concentrated cytosolic recombinant human glyoxalase II (GII) solutions is to undergo partial precipitation. Previous work indicated that anionic phospholipids (PLs) exert a noncompetitive inhibition on the enzymatic activity of the soluble enzyme. In this study, FTIR spectroscopy was used to analyze the structural properties and the thermal stability of the soluble protein in the absence and in the presence of liposomes made of different phospholipids (PLs). The structural analysis was performed on the precipitate as well. The interaction of acidic PLs with GII lowered the thermal stability of the enzyme and inhibited protein intermolecular interactions (aggregation) brought about by thermal denaturation. Infrared data indicated that ionic and hydrophobic interactions occur between GII and acidic PLs causing small changes in the secondary structure of the enzyme. No interactions of the protein with egg phosphatidylcholine liposomes were detected. The results are consistent with the destabilization of the protein tertiary structure, and indicate that GII possesses hydrophobic part(s) that interact with the acyl chains of PLs. Data on precipitated GII did not show remarkable modification of secondary structure, suggesting that hydrophobic stretches of the enzyme may also be involved in the protein–protein association (precipitation) at high GII concentration. The alterations in the GII structure and the noncompetitive inhibition exerted by acidic PLs are strictly related. Proteins 2002;48:126–133. © 2002 Wiley‐Liss, Inc.
Predicted impact of transgenic, herbicide‐tolerant corn on drinking water quality in vulnerable watersheds of the mid‐western USA
Authors: Wauchope R Don , Estes Tammara L , Allen Richard , Baker James L , Hornsby Arthur G , Jones Russell L , Richards R Peter , Gustafson David I 
Published: August 2002

AbstractIn the intensely farmed corn‐growing regions of the mid‐western USA, surface waters have often been contaminated by herbicides, principally as a result of rainfall runoff occurring shortly after application of these to corn and other crops. In some vulnerable watersheds, water quality criteria for chronic human exposure through drinking water are occasionally exceeded. We selected three settings representative of vulnerable corn‐region watersheds, and used the PRZM‐EXAMS model with the Index Reservoir scenario to predict corn herbicide concentrations in the reservoirs as a function of herbicide properties and use pattern, site characteristics and weather in the watersheds. We compared herbicide application scenarios, including broadcast surface pre‐plant atrazine and alachlor applications with a glyphosate pre‐plant application, scenarios in which losses of herbicides were mitigated by incorporation or banding, and scenarios in which only glyphosate or glufosinate post‐emergent herbicides were used with corn genetically modified to be resistant to them. In the absence of drift, in almost all years a single runoff event dominates the input into the reservoir. As a result, annual average pesticide concentrations are highly correlated with annual maximum daily values. The modeled concentrations were generally higher than those derived from monitoring data, even for no‐drift model scenarios. Because of their lower post‐emergent application rates and greater soil sorptivity, glyphosate and glufosinate loads in runoff were generally one‐fifth to one‐tenth those of atrazine and alachlor. These model results indicate that the replacement of pre‐emergent corn herbicides with the post‐emergent herbicides allowed by genetic modification of crops would dramatically reduce herbicide concentrations in vulnerable watersheds. Given the significantly lower chronic mammalian toxicity of these compounds, and their vulnerability to breakdown in the drinking water treatment process, risks to human populations through drinking water would also be reduced.© 2001 Society of Chemical Industry
Passive control methods for seismic response modification
Authors: Towashiraporn P , Park J , Goodno B J , Craig J I 
Published: August 2002

AbstractPassive energy dissipation devices have been successfully implemented in buildings around the world to reduce structural response, primarily due to earthquakes, but also for wind and other dynamic loading conditions. The basic objective in using passive energy dissipation devices is to try to concentrate as much of the energy dissipation as possible into specially designed devices, rather than to allow it to develop in the primary structural elements, and thereby to reduce damage in the main structure. Passive approaches differ from active ones in that they do not require any external sources of power to operate, and this is particularly useful in situations such as earthquakes where power is likely to be interrupted when it is most needed.The focus of this paper is a review of passive energy dissipation devices for seismic response modification applications. Past developments and contemporary examples of metallic hysteresis, friction and viscoelastic devices suitable for building applications are included in the first part of the paper. Current design guidelines based on both linear and nonlinear procedures are summarized next. Finally, three recent applications of metallic hysteretic damping devices are described. The first two examples present the use of metallic damping devices as cladding connections, while the third example shows an application of metallic devices in a relatively stiff, unreinforced masonry building. These examples show the potential versatility of passive energy dissipation devices and illustrate some of the analysis methods that might be used.
Tea pigments inhibit the production of type 1 (TH1) and type 2 (TH2) helper T cell cytokines in CD4+ T cells
Authors: Tomita Michiyo , Irwin Kara I. , Xie Zi‐Jian , Santoro Thomas J. 
Published: August 2002

AbstractTea pigments are oxidized products of polyphenols derived from tea leaves (Camellia sinensis). Theaflavins are constituents of tea pigments with antioxidant, antineoplastic and antiinflammatory properties similar to their parent compounds. The biological properties of polyphenols and theaflavins have been linked to their capacity to inhibit the activation of nuclear factor‐κB (NF‐κB), a transcription factor, which is critically involved in the molecular regulation of a number of proinflammatory cytokines. The current study examines the requirement for NF‐κB in the immunosuppressive effects mediated by tea antioxidants. Specifically, we tested the hypothesis that cytokines produced by type 1 (TH1) CD4+ T cells which require NF‐κB for gene expression, such as interleukin‐2 (IL‐2) and interferon gamma (IFN γ), are selectively inhibited by tea pigments. We found that tea pigments potently suppress IL‐2 secretion, IL‐2 gene expression and the activation of NF‐κB in murine spleens enriched for CD4+ T cells, as expected. Consistent with our hypothesis, tea pigments also inhibited the induction of IFNγ mRNA. However, the expression of the TH2 cytokines IL‐4 and IL‐5, which lack functional NF‐κB sites within their promoters was unexpectedly suppressed by tea pigments, as well. The results indicate that NF‐κB may be only one of multiple transcription factors inhibited by tea pigments. Copyright © 2002 John Wiley and Sons, Ltd.
Determination of stability of MIG/MAG welding processes
Authors: Suban Marjan 
Published: August 2002

AbstractThe paper treats several methods of evaluating the stability of MIG/MAG welding processes, which are based on measurement of time‐varying welding‐current intensity and welding voltage. The stability of the welding process is affected by numerous parameters. The most unfavourable result of poor stability are spatters, which are problematic in terms of material losses and extension of production times due to cleaning, as well as appearance. The experimental part of the paper is based on stability analyses carried out with three different gas‐shielding atmospheres. Two different welding domains were compared. The first was short‐circuit material transfer, and the second spraying material transfer. The results obtained in the analysis of the signals measured indicate a more stable short‐circuit material transfer in the case of welding with the pure CO$_2$ gas, and a more stable spray material transfer in the case of welding with the transferred ionized molten energy mixture. Copyright © 2001 John Wiley & Sons, Ltd.