bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling of “living” free‐radical polymerization processes. I. Batch, semibatch, and continuous tank reactors
Authors: Zhang Min , Ray W. Harmon 
Published: October 2002

AbstractA comprehensive mathematical model is developed for “living” free‐radical polymerization carried out in tank reactors and provides a tool for the study of process development and design issues. The model is validated using experimental data for nitroxide‐mediated styrene polymerization and atom transfer radical copolymerization of styrene and n‐butyl acrylate. Simulations show that the presence of reversible capping reactions between growing and dormant polymer chains should boost initiation efficiency when using free nitroxide in conjunction with conventional initiator and also increase the effectiveness of thermal initiation. A study shows the effects of the value of the capping equilibrium constant and capping reaction rate constants for both nitroxide‐mediated styrene polymerization (using alkoxyamine as polymer chain seeds) and atom transfer radical polymerization of n‐butyl acrylate (using methyl 2‐bromopropionate as chain extension seeds). Also the effect of introducing additional conventional initiator into atom transfer radical polymerization of n‐butyl acrylate is studied. It is found that the characteristics of long chain growth are determined by the fast exchange of radicals between growing and dormant polymer chains. Polymerization results in batch, semibatch, and a series of continuous tank reactors are analyzed. The simulations also show that a semibatch reactor is most flexible for the preparation of polymers with controlled architecture. For continuous tank reactors, the residence time distribution has a significant effect on the development of chain architecture. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1630–1662, 2002
Adsorption studies of fatty acids on montmorillonite‐based filler clay
Authors: Khalil Hanaa S. A. , Abdelhakim A. A. 
Published: October 2002

AbstractSurface coating of montmorillonite‐based filler clay with stearic and oleic (9‐octadecenoic acid) acids was presented. Sedimentation measurements showed that the sedimentation rate and the sediment volume decreased sharply with the adsorbed amount of the acid up to a certain concentration and then became constant. The chemical analysis showed that the adsorbed amount of either acid by montmorillonite clay increased with the equilibrium concentration of the acid in the solution. The adsorption isotherm indicated the formation of a monolayer on the clay surface at a lower concentration of the acids followed by formation of multilayers of the acids on the clay surfaces at higher concentrations. XRD analysis indicated no intercalation of either acid in the lamella of the clay. We concluded the possibility of surface coating of montmorillonite clay with a monolayer of fatty acids that render the clay organophilic. The adsorption of either acid improved the dispersibility of the clay particles in organic or polymeric media. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2574–2580, 2002
Gas‐transport properties through cation‐exchanged sulfonated polysulfone membranes
Authors: Bum Park Ho , Yong Nam Sang , Won Rhim Ji , Min Lee Jung , Kim Sun E. , Ran Kim Jung , Moo Lee Young 
Published: October 2002

AbstractSulfonated polysulfone (SPS) membranes were prepared, and the gas‐transport properties of the resulting ionic polymers were examined. Gas‐transport measurements were made on dense films of these polymers with a continuous flow technique. The sulfonation of polysulfone and the metal‐cation exchange of SPS were confirmed with Fourier transform infrared spectroscopy and electron spectroscopy for chemical analysis. The SPS membranes exchanged with the monovalent metal ions showed higher permeability coefficients than the SPS membranes exchanged with the multivalent metal ions, whereas the selectivities of all the metal‐cation‐exchanged sulfonated polysulfone (MeSPS) membranes for O2/N2 and CO2/N2 gas pairs were higher than those of SPS membranes. When the MeSPS membranes with metal cations of similar ionic radii were compared, the ideal selectivities of O2/N2 and CO2/N2 through MeSPS with divalent cations were higher than those through MeSPS with monovalent cations. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2611–2617, 2002
A convenient procedure for preparation of a novel allylphenoxytriazine monomer and the properties of its copolymer with bismaleimide (BMI)
Authors: Fang Qiang , Jiang Biao , Yu Yi‐Hua , Zhang Xiao‐Bing , Jiang Lu‐Xia 
Published: October 2002

AbstractA novel allylphenoxytriazine monomer, 2,4‐di (2‐allylphenoxy)‐6‐N,N‐dimethylamino‐1,3,5‐triazine (DAPDMT) was prepared in one‐pot by reacting cyanuric chloride with 2‐allylphenol at first, and then by directly treating the adduct with N,N‐dimethylamine without separation. The monomer was used to modify a popular commercial bismaleimide (BMI) resin, 4,4′‐bismaleimidodiphenyl methane (BMDPM), and the results showed that the monomer could effectively improve mechanical properties of BMDPM resin without greatly decreasing heat resistance of the resin. The better results were obtained when the molar ratio of DAPDMT/BMDPM was 1 : 4. Because of more reactive sites in the monomer, the potential uses of the monomer were predicted. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2279–2284, 2002
Improvement in the water‐absorbing properties of superabsorbent polymers (acrylic acid‐co‐acrylamide) in supercritical CO2
Authors: Ma Li , Zhang Le , Yang Ji‐Chu , Xie Xu‐Ming 
Published: October 2002

AbstractSuperabsorbent resins prepared by ultraviolet radiation‐inducing polymerization techniques with acrylic acid/acrylamide were treated with supercritical carbon dioxide (SC‐CO2). The water‐absorbing properties of the treated resins were greatly improved. The water‐absorbing properties of resins treated with SC‐CO2 in the pressure range of 10–35 MPa and the temperature range of 40–60°C were studied. The effects of the treatment time and depressurizing speed of CO2 after treatment were also examined. Obviously, different results were found for particles of different sizes. Smaller particles were more efficient under the same treatment conditions. Samples were tested with differential scanning calorimetry. The results showed that the plasticizing effect of CO2 reduced the glass‐transition temperature of the polymer, and it was proposed that the plasticization effect might have led to polymer chain redistribution and better flexibility. Minor changes in the surface morphology of the particles were observed with scanning electron microscopy. The extraction of the unpolymerized monomers by SC‐CO2 was also studied. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2272–2278, 2002
Effects of the actual diameters and diameter ratios of barrels and dies on the elastic swell and entrance pressure drop of natural rubber in capillary die flow
Authors: Sombatsompop N. , Dangtangee R. 
Published: October 2002

AbstractThe effects of the actual diameters and diameter ratios of barrels and dies on the elastic swell and entrance pressure drop of natural rubber compounds in an extrusion capillary rheometer were investigated. Either the barrel diameter or the die diameter was altered so that different barrel‐diameter/die‐diameter (DB/DD) ratios were obtained, both the barrel and die diameters also being varied simultaneously. The extrudate swell and entrance pressure drop were dependent not only on DB/DD but also on the actual diameters used. For fixed DB/DD ratios, the change in the extrudate swell was linearly influenced by the entrance pressure drop at low actual barrel and die diameters (DB/DD = 20/4–30/7 mm/mm) but was associated with a change in the material viscosity at high barrel and die diameters (DB/DD = 35/7–40/8 mm/mm). When the die diameter was fixed, the relationship between the entrance pressure drop and the extrudate swell was linear up to a certain value of the barrel diameter greater than 30 mm. Beyond this critical barrel value, the relationship became nonlinear and associated with the shearing stress generated by the formation of semipluglike flow patterns and the residence time of the material. For a constant barrel diameter, the smaller the die diameter was, the greater the extrudate swell was because of the increases in the extensional deformation and wall shear rate coupled with a reduction in the material residence time. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1762–1772, 2002
Functionalized multiarm poly(ϵ‐caprolactone)s: Synthesis, structure analysis, and network formation
Authors: Lang Meidong , Chu Chih‐Chang 
Published: October 2002

AbstractThe purpose of this research was to synthesize and characterize a novel class of four‐arm, star‐shape biodegradable polymers having double‐bond functionality as a precursor for free‐radical polymerization, with unsaturated monomers or macromers or photocrosslinking for network formation. The synthesis involved two basic steps. First, hydroxyl‐functionalized four‐arm poly(ϵ‐caprolactone)s (PPCL‐OH) were synthesized by the ring‐opening polymerization of ϵ‐caprolactone in the presence of pentaerythritol and stannous octoate. Second, double‐bond–functionalized four‐arm poly(ϵ‐caprolactone)s (PPCL‐Ma) were synthesized by reacting PPCL‐OH with maleic anhydride in the melt at 130°C. Quantitative conversion of hydroxyl functionality in PPCL‐OH to double‐bond functionality was achieved for low molecular weight PPCL‐OH. Both the PPCL‐OH and the PPCL‐Ma were characterized by FTIR, 1H‐NMR, 13C‐NMR, SEC, and DSC. The capability of the double‐bond–functionalized four‐arm poly(ϵ‐caprolactone)s (PPCL‐Ma) to form network structures was preliminarily shown by photocrosslinking PPCL‐Ma. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2296–2306, 2002
Preparation and properties of waterborne polyurethane–urea anionomers. I. The influence of the degree of neutralization and counterion
Authors: Yang Jung‐Eun , Kong Ju‐Shik , Park Sang‐Woo , Lee Dong‐Jin , Kim Han‐Do 
Published: October 2002

AbstractTwo series of waterborne polyurethane–urea anionomers were prepared by a polyaddition reaction with isophorone diisocyanate, poly(tetramethylene oxide) glycol (weight‐average molecular weight = 1000), dimethylol propionic acid (DMPA), and ethylene diamine as chain extenders. Triethylamine (TEA) or 28:1 mol/mol ammonium hydroxide (NH4OH)/cupric hydroxide [Cu(OH)2] was used as a neutralization agent [NH(C2H5) or NH/Cu2+ counterion] for the pendant COOH group of DMPA. The effects of the degree of neutralization and counterion on the particle size of the dispersions, the conductivity, and the antibacterial and mechanical properties of polyurethane–urea anionomer films were investigated. The particle sizes of the two sample series dispersions decreased with an increasing degree of neutralization. Aqueous dispersions of polyurethane–urea anionomers with particle sizes of 30–120 nm were stable for about 3 months. By infrared spectroscopy, it was found that TEA‐based samples (T series) had higher fractions of hydrogen‐bonded carbonyl groups in the ordered region than NH4OH/Cu(OH)2‐based samples (S series). However, the fractions of hydrogen‐bonded carbonyl groups in the disordered region of the S‐series samples were higher than those of the T‐series samples. The conductivities of the S‐series film samples were higher than those of the T‐series samples. However, the T‐series film samples commonly had higher tensile strengths and initial moduli than the S‐series samples. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2375–2383, 2002
Antiarthritic activity of an orally active C5a receptor antagonist against antigen‐induced monarticular arthritis in the rat
Authors: Woodruff Trent M. , Strachan Anna J. , Dryburgh Nathan , Shiels Ian A. , Reid Robert C. , Fairlie David P. , Taylor Stephen M. 
Published: October 2002

AbstractObjectiveTo determine if the new, orally active C5a receptor antagonist, the cyclic peptide AcF‐[OPdChaWR], reduces the severity of pathology in a rat model of immune‐mediated monarticular arthritis.MethodsArthritis was induced in the right knee of previously sensitized rats by the intraarticular injection of methylated bovine serum albumin. Rats were examined for either 14 days or 28 days, or for 49 days following a second antigen challenge at 28 days. The C5a antagonist (1 or 3 mg/kg/day) and/or ibuprofen (30 mg/kg/day) were administered orally on a daily basis either before or after arthritis induction.ResultsRats receiving AcF‐[OPdChaWR] had significant reductions in right knee swelling, gait disturbance, lavaged joint cell numbers, and right knee histopathology, as well as in serum levels of tumor necrosis factor α (TNFα) and intraarticular levels of interleukin‐6 and TNFα on day 14. In the 14‐ and 28‐day studies, ibuprofen resulted in a similar reduction in gait abnormalities and intraarticular inflammatory cells compared with the C5a antagonist, but was less effective in reducing knee swelling over the course of the study and had no effect on knee histopathology. Combination therapy with AcF‐[OPdChaWR] and ibuprofen resulted in no greater efficacy than with the C5a antagonist alone. Rats injected twice with the antigen in the 49‐day study displayed the most severe histopathology and this, as well as knee swelling and gait abnormalities, was significantly reduced by repeated treatment with the C5a antagonist.ConclusionAn agent that inhibits the action of C5a in this model significantly reduced joint pathology, while ibuprofen was not effective. C5a antagonists could therefore have broader therapeutic benefits than nonsteroidal antiinflammatory drugs as antiarthritic agents for rheumatoid arthritis.
Contribution of hospital characteristics to the volume–outcome relationship: Dislocation and infection following total hip replacement surgery
Authors: Solomon Daniel H. , Losina Elena , Baron John A. , Fossel Anne H. , Guadagnoli Edward , Lingard Elizabeth A. , Miner Andrew , Phillips Charlotte B. , Katz Jeffrey N. 
Published: October 2002

AbstractObjectiveMortality and complication rates after total hip replacement (THR) are inversely associated with the volume of THRs performed at hospitals and by individual surgeons. It is not clear, however, why a higher volume of such procedures is associated with better outcomes. We evaluated the contribution of hospital structural characteristics to the volume–outcome relationship in THR by examining the rates and predictors of postoperative complications.MethodsWe analyzed data pertaining to 5,211 Medicare patients who underwent primary THR in 1995 or 1996 at 167 hospitals in Colorado, Pennsylvania, and Ohio. Data were derived from several sources, including Medicare Part A and Part B claims, the American Board of Medical Specialties, a hospital survey regarding institution‐specific characteristics and structural aspects of the care setting, and the American Hospital Association 1995 Annual Survey. Multivariate models were constructed to determine whether hospital structure or surgeon‐associated factors may underlie the relationship between volume of THRs and the occurrence of perioperative orthopedic adverse events, defined as deep wound infection or hip dislocation within 90 days of surgery.ResultsOf the patients studied, 2.6% experienced an orthopedic adverse event after THR. Sixty‐nine percent fewer events occurred in hospitals where >100 THRs in Medicare patients were performed annually, compared with hospitals where ≤25 THRs were performed. In univariate analyses, several hospital‐level factors were associated with a reduced (∼50%) risk of adverse events, including private (versus public) ownership, membership in the Council of Teaching Hospitals, presence of any residency training program, availability of a dedicated orthopedic nursing unit, and existence of operating rooms with laminar flow exhaust systems. However, the only hospital‐level factor associated with adverse events in multivariate models was the use of laminar flow exhaust systems. When surgeon volume was added to the models, it was the strongest predictor of adverse events, with hospital volume and hospital‐level factors having no appreciable association with adverse events.ConclusionHospital‐level factors were not independent predictors of the association between hospital volume and orthopedic adverse events. The volume of THRs performed by individual surgeons is the most important determinant of orthopedic complications and should be considered in efforts to improve THR outcomes.
HLA–DRB1 genotype associations in 793 white patients from a rheumatoid arthritis inception cohort: Frequency, severity, and treatment bias
Authors: Fries James F. , Wolfe Frederick , Apple Raymond , Erlich Henry , Bugawan Teodorica , Holmes Tyson , Bruce Bonnie 
Published: October 2002

AbstractObjectiveThe HLA–DRB1 “shared epitope” (SE) genotypes are associated with rheumatoid arthritis (RA), but it remains controversial whether the association is with incidence, severity, or both, whether there are associations in seronegative patients, and whether different DRB1 alleles that contain the SE have similar effects on RA susceptibility and/or severity. The present study was undertaken to study these issues in a large cohort of patients with RA.MethodsWhite patients with RA of <6 months' duration (n = 793) were enrolled in an inception cohort. HLA–DRB1 typing was performed, and patients were categorized into 21 DRB1 genotype groups. The disability index of the Health Assessment Questionnaire was the primary outcome measure.ResultsDRB1 associations in seronegative RA patients closely resembled those in controls. Of seropositive patients, 21% had 2 copies of the epitope, 52% had 1 copy, and 27% had none. However, not all genotypes with 1 copy were associated with increased susceptibility; for example, frequencies of DRB1*0404/X and *01/X did not differ from those in controls. Absolute differences between seropositive RA patients and controls were greatest for DRB1*0401 homozygosity (3.8% versus 0.8%, respectively) and *0401/0404 heterozygosity (4.7% versus 1.0%). DRB1*0404 was increased in frequency in seropositive RA but, unlike *0401, an increased frequency was seen only with 2 epitope copies. The relatively rare DRB1*10 had an unexpected association with seropositive RA, being present in 1.7% of seropositive RA patients and 0.7% of controls, and also showed a trend toward association with greater disease severity. The presence of 2 epitope copies was associated with increased frequency of seropositivity and younger age at disease onset, not with disease severity. Treatment indication bias was substantial and may have accounted for some of these effects. HLA–DRB1*0401/0404 was found much more frequently in men and in patients with a lower age at disease onset, and there was a trend toward a higher frequency of *0404/0401 in women.ConclusionThis large inception cohort study confirms previously identified major associations and provides additional insights. Only one dominant association was found: *0401, which differs from other SE alleles in a single Lys‐for‐Arg substitution. The association of the rare DRB1*10 allele has not previously been postulated. Sex associations were confirmed. Associations with seronegative RA were not seen. Not all genotypes containing an SE copy showed increased susceptibility to RA. The association of SE genotypes found in this study related to disease susceptibility rather than severity.
Inhibiting viral proteases: Challenges and opportunities
Authors: Bianchi Elisabetta , Pessi Antonello 
Published: October 2002

AbstractInhibitor design against viral targets must take into account the peculiar characteristics of viral biology—in particular, the plasticity of their replicative machinery. This includes maturational cleavage of the polyprotein, which is mediated by virally encoded proteases. Designing against a movable target is particularly challenging, but at the same time it offers new opportunities. Here we describe our experience with the NS3/4A (NS: nonstructural) serine protease of human hepatitis C virus (HCV). By extensive use of combinatorial peptide libraries, various inhibitor types were generated, including product inhibitors, serine traps, P–P′ inhibitors, and prime side inhibitors. The latter represent a first case for a serine protease. A key finding, derived from structural studies utilizing these inhibitors, was that NS3 is an induced‐fit protease, requiring both the NS4A cofactor protein and the substrate to fully activate its catalytic machinery. In the absence of cofactor and/or substrate, NS3 exists in solution as a large conformational ensemble, which can be matched by a correspondingly large set of peptide inhibitors, each one stabilizing a given conformer. In the perspective of inhibiting viral proteases in general, we suggest that combinatorial ligand ensembles may be a powerful tool, to contrast the adaptive potential of the viral quasispecies. © 2002 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 66: 101–114, 2002
Aggregation kinetics of well and poorly differentiated human prostate cancer cells
Authors: Enmon Richard M. , O'Connor Kim C. , Song Hong , Lacks Daniel J. , Schwartz Daniel K. 
Published: October 2002

AbstractAggregation of attachment‐dependent animal cells represents a series of motility, collision, and adhesion events applicable to such diverse fields as tissue engineering, bioseparations, and drug testing. Aggregation of human prostate cancer cells in liquid‐overlay culture was modeled using Smoluchowski's collision theory. Using well (LNCaP) and poorly differentiated (DU 145 and PC 3) cell lines, the biological relevance of the model was assessed by comparing aggregation rates with diffusive and adhesive properties. Diffusion coefficients ranged from 5 to 90 μm2/min for single LNCaP and PC 3 cells, respectively. Similar diffusivities were predicted by the persistent random walk model and Einstein relation, indicating random motion. LNCaP cells were the most adhesive in our study with reduced cell shedding, 100% adhesion probability, and enhanced expression of E‐cadherin. There was an increase in DU 145 cells staining positive for E‐cadherin from nearly 20% of single cells to uniform staining across the surface of all aggregates; under 30% of PC 3 aggregates stained positive. Aggregation rates were more consistent with adhesive properties than with motilities, suggesting that aggregation in our study was reaction‐controlled. Relative to other assays employed here, aggregation rates were more sensitive to phenotypic differences in cell lines and described size‐dependent changes in aggregation at a finer resolution. In particular, model results suggest similar aggregation rates for two‐dimensional DU 145 and PC 3 aggregates and upwards of 4‐fold higher rates for larger three‐dimensional DU 145 spheroids, consistent with expression of E‐cadherin. The kinetic model has application to spheroid production, to cell flocculation and as an adhesion assay. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 580–588, 2002.