bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of release of particulate solutes incorporated in cellulosic polymer matrices as a function of solute solubility and polymer swellability. III. Moderately soluble solute
Authors: Papadokostaki K. G. , Herouvim M. E. 
Published: August 2002

AbstractOur previous investigation of the kinetics of release of simple particulate solutes of very low (CaSO4 or SrSO4) or very high aqueous solubility (NaCl) from cellulose acetate (CA) matrices (in the form of thin films) in contact with an eluant aqueous phase is here extended to a solute of moderate solubility (CsNO3). Simultaneous measurement of the concurrent variation of the water content of the matrix revealed the occurrence of osmotically induced excess water uptake by the loaded matrix for all loads studied, as previously observed in the case of NaCl at lower loads. The resulting enhancement of solute release rate was considerable but much less than that generated by NaCl. Sorption and diffusion of the solute in the corresponding particle‐depleted polymer matrices was also investigated. The results exhibited a pattern qualitatively very similar to that of NaCl but greatly attenuated in quantitative terms. These observations are in keeping with the relatively weak osmotic power of CsNO3. A mechanism for osmotically induced enhancement of solute release rate previously formulated (in terms of the growth of zones of enhanced hydration of the polymer matrix surrounding the embedded solute particles) to account for NaCl release behavior observed at lower particle loads was found to be applicable here at all loads examined. The degree of hydration of the (neat) CA polymer matrix was also varied (by varying the conditions of film preparation or by wet thermal after‐treatment of the as‐prepared films) and its effect on CsNO3 partition and diffusion coefficients was studied. The results provided the basic information needed for interpretation of the corresponding particle‐depleted film data, in comparison with the previous ones for NaCl. It was thus shown that imbibed water was more homogeneously distributed in NaCl‐depleted, than in CsNO3‐depleted, films. It was also observed that variation of the degree of polymer hydration affected primarily the rate, and only secondarily the kinetics, of particulate CsNO3 release. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2028–2039, 2002; DOI 10.1002/app.10499
Dissolution and mutual diffusion of poly(N‐vinyl pyrrolidone) in short‐chain poly(ethylene glycol) as observed by optical wedge microinterferometry
Authors: Bairamov D. F. , Chalykh A. E. , Feldstein M. M. , Siegel R. A. , Platé N. A. 
Published: August 2002

AbstractDissolution and mutual diffusion of poly(N‐vinylpyrrolidone) (PVP) in short‐chain poly(ethylene glycol) PEG400 were studied by wedge microinterferometry over the temperature range of 40–100°C. Successive photographs of interference patterns measured at λ = 546 nm with an optical microscope at 130× magnification were used to determine the PVP/PEG concentration–distance profiles. These profiles were found to be highly asymmetric, exhibiting steep concentration gradients near the surface of the glassy polymer sample. The PVP/PEG system is completely miscible, and interdiffusion kinetics are Fickian with a concentration‐dependent mutual diffusion coefficient, DV. Thermal activation of diffusion was studied in terms of an Arrhenius‐type relation, with concentration dependent activation energy Ea. Values of DV and Ea are in accord with the compositional behavior of the glass transition temperature in PVP–PEG blends, indicating that PVP plasticized with PEG behaves like an elastomer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1128–1136, 2002
Ecological aspects of the manufacture and application of highly pure liquid substances
Authors: Ryabenko E. A. , Yaroshenko A. M. , Blum G. Z. , Zaikov G. E. , Zaikov V. G. 
Published: August 2002

AbstractThe action mechanism for aggressive and highly pure media on fluoropolymer constructional elements is assumed to consist of two basic microeffects: destructive changes in the fluoropolymer and contamination of the environment. Our approach to a quantitative estimation of the physicochemical stability is based on logic similar to that of a thermodynamic model of a two‐component system. A fluoropolymer and changes in its microstructure are considered the first component of the system. The second component is composed of liquid media contaminated with fluoroorganic compounds extracted from the fluoropolymer. The proposed methods for delivering aggressive and highly pure fluids to consumers allow the exclusion of pollution from working areas with gaseous products through an exception to a number of intermediate stages of product transport. The discussed principles allow the creation of a modern, highly effective, and safe (with respect to the ecology and raw materials) production of aggressive liquid chemicals for consumers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 906–910, 2002
Photon transmission technique for monitoring drying processes in acrylamide gels formed with various crosslinker contents
Authors: Kara Selim , Pekcan Önder 
Published: August 2002

AbstractIn situ photon transmission experiments were performed using UV‐visible (UVV) spectrometer during the drying of polyacrylamide (PAAm) gels. These gels are formed from acrylamide (AAm) with various N,N′‐methylenebis(acrylamide) (Bis) contents by free radical crosslinking copolymerization (FCC) in water. The transmitted light intensity, Itr increased continuously as PAAm gels are dried. Increase in Itr was attributed to the decrease in the scattered light intensity, Isc, which might be originated from the contrast between “frozen blob clusters” and holes in the drying gel. Decrease in Isc was modeled using Rayleigh's equation, where drying times with various exponents were found to be proportional to the volume of frozen blob clusters. It was observed that the radius of frozen blob cluster (correlation length), ξc increased in various power of time, depending on Bis contents during drying of gels. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1898–1906, 2001
Modification of bismaleimide with allyl compound and N‐phenylmaleimide
Authors: Xiaoyan Ma , Hongxia Yan , Rongchang Ning 
Published: August 2002

AbstractThree different formulas with low‐cost resins, made up of N,N′‐bismaleimidephenylmethane (BMI), O,O′‐diallybisphenol A(BA), and N‐phenylmaleimide (NPMI) were developed. The properties of prepolymers, such as activation energies, enthalpy, and constants of reaction rate, were obtained by a kinetic programmer on DSC. Thermal and mechanical properties of neat resins were also studied. The results showed that the systems had low melting point and low viscosity. All cured resins presented excellent thermal and good mechanical properties. The mechanical properties could be affected by the quantity of NPMI and postcuring process. The water absorption is ≤1.98%; heat deflection temperature (HDT) is ≥250°C after aging for 100 h in distilled water of 90°C. The data indicate that the BMI can be effectively improved by adding BA and NPMI, while its heat resistance and hot/wet mechanical properties can be fairly retained. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2518–2522, 2001
Modeling of particle growth and morphology in the gas phase polymerization of butadiene. II. Simulation and discussion
Authors: Zhao Junzi , Sun Jianzhong , Zhou Qiyun , Pan Zuren 
Published: August 2002

AbstractThe improved multigrain model was used to simulate the gas phase polymerization of butadiene catalyzed by low‐, medium‐, and high‐activity catalysts, respectively. For the low‐activity catalyst, the mass and heat transfer resistances in the particle were negligible. The morphology of the polymeric particles was uniform. For the medium‐activity catalyst, the overall mass transfer effectiveness was > 90%, the maximal temperature rise was 8K, and the heat transfer resistance in the particle was negligible. Mass transfer resistance does not affect the morphology of product particle significantly. For the high‐activity catalyst, the overall mass transfer effectiveness was within the range of 70–96%, the morphology of the product particle was affected by the mass transfer resistance to some extent. The maximal temperature rise was 21K; the heat transfer resistance in the particle was negligible as well. However, there was some severe mass transfer resistance in the particle, and the maximal temperature rise was ≤ 30K for the large catalyst particle with the same activity. Thus, the polymeric particle morphology was comparatively poor, with the occurrence of particle softening and sticking. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 730–741, 2001
Design of multiple flame‐retardant polymers
Authors: Roy Sabitabrata , Maiti Sukumar 
Published: August 2002

AbstractTwo polyphosphonates having multiple flame‐retardant actions were synthesized by interfacial polycondensation of a bisphenol and dichlorophenylphosphine oxide using cetyl trimethyl ammonium chloride as a phase transfer catalyst (PTC) at 0°C. The polyphosphanates thus prepared were characterized by viscometry, elemental analysis, IR, 1H‐NMR, 31P‐NMR, and X‐ray diffraction studies. These polymers are highly soluble in polar solvents such as DMF, DMAc, DMSO, etc., as well as in chlorinated hydrocarbon solvents such as CH2Cl2, CHCl3, etc. The thermal study of polymers was carried out by TGA and DTA analyses. The flammability of the polymers was studied by the limiting oxygen index measurements. The polymers are self‐extinguishing, and begin to lose weight at around 252°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 785–792, 2001
Phase equilibria of polypropylene samples with hydrocarbon solvents at high pressures
Authors: Dariva C. , Oliveira J.Vladimir , Tavares F. W. , Pinto J. C. 
Published: August 2002

AbstractThe objective of this work is to provide high‐pressure phase equilibrium data for polypropylene (PP) samples (two commercial and one metallocenic grades) with some hydrocarbon solvents (propane, propylene, n‐butane and 1‐butene). The experiments were carried out in a high‐pressure variable‐volume view cell in the temperature range of 75–150°C, for polymer compositions ranging from 0.3 to 10 wt %. Phase transitions were recorded visually as cloud points and identified as liquid–liquid and vapor–liquid transitions. When pressure transition data obtained for olefins and paraffins of similar chain length and at similar temperatures and polymer compositions are compared, it may be observed that paraffins lead to the decrease of the pressure transition values. Therefore, the one‐phase region is larger for paraffins than for olefins. In the range of commercial interest analyzed, it is also observed that the influence of polymer average molecular weight upon the cloud points is negligible. Experimental data are then used to build the P‐T diagrams for these systems, allowing the identification of the LCST (Lower Critical Solution Temperatures) and LCEP (Lower Critical End Points) curves. Finally, the original SAFT equation of state (SAFT‐EOS) is used to model the experimental data. It is shown that the SAFT‐EOS provides an excellent description of the solution behavior in the whole experimental range analyzed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3044–3055, 2001
Development of a new silicone‐base transdermal therapeutic system. II. Study of trifunctional ingredients
Authors: Wagner Ödön 
Published: August 2002

AbstractThe effect of two trifunctional silicon compounds was investigated on the polarity behavior of silicone elastomers by investigating the swelling properties in solvents of various polarity. The properties of the silicone elastomer were also influenced by methyltrimethoxysilane (MTS) and N‐[(aminoethyl)aminopropyl]trimethoxysilane (GF‐91) if they were used together with the networking agent. The cooperative effect of the polar liquid ingredients [glycerol, ethylene glycol, propylene glycol, poly(ethylene glycol) 400] and GF‐91 as well as the dissolution of the liquid ingredients from the silicone elastomer were studied. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1187–1194, 2001
Melt rheology of poly(ϵ‐caprolactone)/poly(styrene‐co‐acrylonitrile) blends
Authors: Aoki Yuji , Arendt Oliver 
Published: August 2002

AbstractDynamic viscoelastic properties for miscible blends of poly(ϵ‐caprolactone) (PCL) and poly(styrene‐co‐acrylonitrile) (SAN) were measured. It was found that the time–temperature superposition principle is applicable over the entire temperature range studied for the blends. The temperature dependency of the shift factors aT can be expressed by the Williams–Landel–Ferry equation: log aT = −8.86(T − Ts)/(101.6 + T − Ts). The compositional dependency of Ts represents the Gordon–Taylor equation. The zero‐shear viscosities are found to increase concavely upward with an increase in weight fraction of SAN at constant temperature, but concavely downward at constant free volume fraction. It is concluded that the relaxation behavior of the PCL/SAN blends is similar to that of a blend consisting of homologous polymers. It is emphasized that the viscoelastic functions of the miscible blends should be compared in the iso‐free volume state. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2037–2041, 2001
Study on synthesis and morphology control of poly(4‐vinylpyridine‐co‐butyl acrylate)/poly(styrene‐co‐butyl acrylate) composite microspheres
Authors: Ma Qianli , Gu Lixia , Ma Shiyu , Ma Guanghui 
Published: August 2002

AbstractMonodispersed crosslinked cationic poly(4‐vinylpyridine‐co‐butyl acrylate) [P(4VP‐BA)] seed latexes were prepared by soapless emulsion polymerization, using 2,2′‐azobismethyl(propionamidine)dihydrochloride (V50) as an initiator and divinylbenzene (DVB) or ethylene glycol dimethacrylate (EGDMA) as a crosslinker. The optimum condition to obtain monodispersed stable latex was investigated. It was found that the colloidal stability of the P4VP latex can be improved by adding an adequate amount of BA (BA/4VP = 1/4, w/w), and adopting a semicontinuous monomer feed mode. Subsequently, poly(4‐vinylpyridine‐co‐butyl acrylate)/Poly(styrene‐co‐butyl acrylate) [P(4VP‐BA)/P(ST‐BA)] composite microspheres were synthesized by seeded polymerization, using the above latex as a seed and a mixture of ST and BA as the second‐stage monomers. The effects of the type of crosslinker, the degree of crosslinking, and the initiators (AIBN and V50) on the morphology of final composite particles are discussed in detail. It was found that P(4VP‐BA)/P(ST‐BA) composite microspheres were always surrounded by a PST‐rich shell when V50 was used as initiator, while sandwich‐like or popcorn‐like composite particles were produced when AIBN was employed. This is because the polarity of the polymer chains with AIBN fragments is lower than for the polymer with V50 fragments, hence leading to higher interfacial tension between the second‐stage PST‐rich polymer and the aqueous phase, and between PST‐rich polymer and P4VP‐rich seed polymer. As a result, the seed cannot be engulfed by the PST‐rich polymer. Furthermore, the decrease of Tg of the second‐stage polymer promoted phase separation between the seeds and the PST‐rich polymer: sandwich‐like particles formed more preferably than popcorn‐like particles. It is important knowledge that various morphologies different from PST‐rich core/P4VP‐rich shell morphology, can be obtained only by changing the initiator, considering P4VP is much more hydrophilic than PST. The zeta potential of composite particles initiated by AIBN in seeded polymerization shifted from a positive to a negative charge. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1190–1203, 2002
Developmental regulation of connexin 43 expression in fetal mouse testicular cells
Authors: Pérez‐Armendariz E. Martha , Lamoyi Edmundo , Mason J. Ian , Cisneros‐Armas David , Luu‐The Van , Bravo Moreno J. Francisco 
Published: August 2002

AbstractMultiple connexins have been identified in testicular cells. Several lines of evidences indicate that, among them, connexin 43 (Cx43) may be unique for control of gonad development and spermatogenesis. To date, however, it is not known whether Cx43 is expressed in the fetal testis and what possible types of cellular interactions mediated by this connexin are critical to male fertility. In the present work, expression of Cx43 was investigated at various developmental ages in cryosections from mouse testis by using specific antibodies against Cx43. In serial or double‐labeled sections, Cx43 localization was compared with immunocytochemical distribution of steroidogenic enzyme, 3β‐hydroxysteroid dehydrogenase (3βHSD), Mullerian inhibitory hormone (MIH), and germinal nuclear cell antigen (GCNA1), which are specific markers, respectively, of interstitial Leydig, Sertoli, and germinal cells. Sections were analyzed by fluorescence microcopy. We found that Cx43 immunofluorescence (IF) was uniformly distributed in the undifferentiated gonad at 11.5 days post coitus (dpc) and in cells of the mesonephric tubules. In the undifferentiated gonad, Cx43 was localized between primordial germ cells and somatic cells. At 12.5 dpc, when the gonad has undergone sexual differentiation, in the interstitium Cx43 was localized in Leydig cells and in the seminiferous cord it was localized between adjacent Sertoli cells. In Leydig and Sertoli cells, Cx43 labeling increased at 14.5, 16.5, and 18.5 dpc. From day 12.5 up to 18.5 dpc, Cx43 was also localized in cell borders between germinal and Sertoli cells. In conclusion, this study demonstrates that from the earliest stages of gonadal development, Cx43 is expressed in the principal cell types that participate in the control of male fertility. It also shows that Cx43 expression in Leydig and Sertoli cells increase during fetal life. Finally, it provides evidence that, throughout embryonic life, Cx43 forms gap junctions between Sertoli and germinal cells. Anat Rec 264:237–246, 2001. © 2001 Wiley‐Liss, Inc.
Outcome and prognostic indicators of diffuse proliferative lupus glomerulonephritis treated with sequential oral cyclophosphamide and azathioprine
Authors: Mok Chi Chiu , Ho Carmen Tze Kwan , Chan Kwok Wah , Lau Chak Sing , Wong Raymond Woon Sing 
Published: August 2002

AbstractObjectiveTo study the outcome and prognostic indicators of diffuse proliferative glomerulonephritis (DPGN) in patients with systemic lupus erythematosus (SLE) treated with sequential oral cyclophosphamide (CYC) and azathioprine (AZA).MethodsSLE patients with biopsy‐proven DPGN treated with sequential oral CYC and AZA were studied. Those who achieved renal remission at 12 months were identified, and the clinical predictors of complete remission were evaluated by regression analysis. All patients were followed up until a relapse of the nephritis or a doubling of the serum creatinine level occurred. The timing and risk factors for flares and creatinine doubling were evaluated by Kaplan‐Meier analysis and with the Cox proportional hazards model.ResultsWe studied 55 patients (47 women, 8 men; mean ± SD age at renal biopsy 31.1 ± 10.4 years); 25 (46%) had a serum creatinine level >106 μmoles/liter, and 29 (53%) had nephrotic syndrome. At 12 months posttreatment, 37 (67%) had complete remission and 12 (22%) had partial remission. The initial serum creatinine level was an independent predictor of complete remission. Excluding the 4 patients who were treatment‐ resistant or died, 21 patients (41%) had renal flares during a median followup of 4 years. The cumulative risk of renal flare was 6% at 1 year, 21% at 3 years, and 32% at 5 years. The median time to relapse was 43 months. The histologic activity score and the mean daily dose of CYC were multivariate predictors of renal flare, by Cox regression. At the last followup visit, 9 of 54 patients (17%) had a doubling of the creatinine level, 6 of whom (11%) underwent dialysis. The cumulative risk of creatinine doubling was 8.4% at 5 years and 18.2% at 10 years. An increasing chronicity index at the time of initial renal biopsy was an independent predictor of deterioration in renal function.ConclusionSequential therapy with oral CYC followed by AZA appears to be an effective treatment regimen for DPGN in patients with SLE, with 89% of patients achieving complete or partial remission at 12 months, 62.8% remaining in remission after 5 years, and 81.8% having stable renal function after 10 years. Predictors of treatment resistance and relapse include increasing serum creatinine level, higher histologic activity scores, and a lower dose of CYC. Increasing chronicity indices predict a deterioration of renal function.
Defective Fc‐dependent processing of immune complexes in patients with systemic lupus erythematosus
Authors: Davies Kevin A. , Robson Michael G. , Peters A. Michael , Norsworthy Peter , Nash Julian T. , Walport Mark J. 
Published: August 2002

AbstractObjectiveTo explore the Fc receptor–dependent handling of immune complexes (ICs) by the fixed mononuclear phagocytic systems (MPS) in patients with systemic lupus erythematosus (SLE).MethodsThe processing in vivo of soluble model 123I–hepatitis B/ anti–hepatitis B ICs was studied in 12 healthy subjects and 10 patients with active SLE. ICs that fixed complement poorly were prepared specifically in order to explore Fc receptor–dependent clearance mechanisms. Clearance kinetics and organ uptake were assessed by computer‐aided gamma scintigraphy and serial blood sampling.ResultsIn both patients and controls, the main site of IC clearance was the liver; only 2–6% of injected ICs were taken up in the spleen. The kinetics of initial IC clearance were similar in both groups, but defective hepatic retention of ICs was demonstrated in patients with SLE. At 1 hour, hepatic activity in patients had fallen to 56% of maximum, compared with 74% in controls (P = 0.0002). Precipitation studies performed on serum samples using staphylococcal protein A–Sepharose indicated that antibody‐complexed tracer was released from the liver 20–50 minutes after injection.ConclusionThese results indicate that Fc‐mediated clearance of ICs is defective in patients with SLE and suggest that ligation of ICs by Fc receptors is critical for their efficient binding and retention by the fixed MPS in the liver.
Term dependence: A basis for Luhn and Zipf models
Authors: Losee Robert M. 
Published: August 2002

AbstractThere are regularities in the statistical information provided by natural language terms about neighboring terms. We find that when phrase rank increases, moving from common to less common phrases, the value of the expected mutual information measure (EMIM) between the terms regularly decreases. Luhn's model suggests that midrange terms are the best index terms and relevance discriminators. We suggest reasons for this principle based on the empirical relationships shown here between the rank of terms within phrases and the average mutual information between terms, which we refer to as the Inverse Representation—EMIM principle. We also suggest an Inverse EMIM term weight for indexing or retrieval applications that is consistent with Luhn's distribution. An information theoretic interpretation of Zipf's Law is provided. Using the regularity noted here, we suggest that Zipf's Law is a consequence of the statistical dependencies that exist between terms, described here using information theoretic concepts.