bluuebunny/crossref_metadata_2025 huggingface dataset:
Aromatic–Aliphatic acrylic monomers and polymers: Synthesis and characterization
Authors: Bicu Ioan , Mustata Fanica
Published: August 2002

Two new ester‐type monomers were synthesized by the condensation of acrylic acid with the products of the hydroxyethylation of 4‐nonylphenol or 4‐tert‐butylphenol. The hydroxyethylation reaction was performed with 1,3‐dioxolan‐2‐ona in the presence of alkalies. By hydroxyethylation, the phenols were changed into alcoholic derivatives able to react with acrylic acid to give acrylic esters. The insertion of the aryl–alkyl groups into the structure of the acrylic esters, and implicitly of the corresponding polymers, was carried out with the intention of increasing their thermostability and improving their behavior as pressure‐sensitive adhesives on the whole. The monomers and the polymers were characterized by elemental and thermogravimetric analyses, IR and 1H‐NMR spectroscopy, and other special methods. The results of these investigations confirmed the formulated suppositions. The inherent viscosities of the resulting polymers were in the range of 47–64 mL/g, and their thermal stability was up to 315–320°C, far higher than that of the polyacrylates used. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 802–814, 2002
Lifetime predictions for the epoxy system BADGE n=0/m‐XDA using kinetic analysis of thermogravimetry curves
Authors: Fraga F. , Rodríguez Núñez E.
Published: August 2002

Lifetime of the epoxy system diglycidil ether of Bisphenol A (BADGE n=0)/ m‐xylylenediamine (m‐XDA) was calculated by thermogravimetric analysis. The Flynn‐Wall‐Ozawa method is used to determine the activation energy of the reaction. Experimental lifetimes in the range of 60–300°C vary from 1.41 109 (2682 years) to 3.35 10−4 min. This isoconversional method is not appropiate to calculate lifetime prediction because of high errors. Scaling factors were determined using the ratio of two reaction rates. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1692–1696, 2002
Ultrafiltration of metal ions by water‐soluble chelating poly(N‐acryloyl‐N‐methylpiperazine‐co‐N‐acetyl‐α‐aminoacrylic acid)
Authors: Rivas Bernabé L. , Pooley S. Amalia , Luna Maribel
Published: August 2002

Water‐soluble copolymers of N‐acryloyl‐N‐methylpiperazine and N‐acetyl‐α‐aminoacrylic acid were synthesized by radical polymerization. The copolymerization yield ranged between 60 and 97%. The FTIR and NMR spectra demonstrated that the copolymerization occurred. The copolymer composition was determined from 1H‐NMR spectra by comparison of methyl groups from both moieties. The copolymers were richest in AAA units. The metal ion retention properties were investigated by the liquid‐phase polymer‐based retention (LPR) technique at different pH and filtration factors. The affinity for the metal ions depended on the copolymer composition, pH, and filtration factor. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2556–2561, 2002
Removing paraffin‐based wax coatings from old corrugated containers using supercritical carbon dioxide
Authors: Stauffer Thad C. , Venditti Richard A. , Gilbert Richard D. , Kadla John F.
Published: August 2002

Supercritical carbon dioxide (SC‐CO2) extractions of paraffin‐based wax coatings from saturated and curtain‐coated old corrugated containers (OCC) are reported. Extractions were performed in a 500‐mL reactor (300 bar, 100°C, 50 g CO2/min and 1 h). Wax removal efficiencies of 98 and 70% for saturated and curtain‐coated OCC, respectively, were obtained. Under similar conditions, extractions in the presence of water resulted in an extraction efficiency of 99% for saturated OCC. Decreasing the operating pressure to 200 bar decreased the extraction efficiency to approximately 50%. Gas chromatography (GC) of the wax coatings on OCC, before and after extraction with SC‐CO2, showed a slight shift in the molecular weight distribution of the paraffin wax (after SC‐CO2 extraction) toward higher molecular weights for both saturating wax and curtain‐coating wax. There was no evidence of chemical degradation or modification of the paraffin wax coatings by SC‐CO2. The packing density, packing arrangement, and dimensions of the curtain‐coated OCC in the extraction apparatus affected the extraction efficiency. Loose packing compared to tight packing, 1 × 1 cm squares versus 1 × 20 cm strips, had higher extraction efficiencies; a random packing arrangement was better than packing with the fluting material in the direction of SC‐CO2 flow. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2699–2704, 2002
Mechanical properties of soft liner–poly(methyl methacrylate)‐based denture material
Authors: Usanmaz Ali , Latifoğlu M. Alper , Doğan Arife , Akkaş Nuri , Yetmez Mehmet
Published: August 2002

In this study, the mechanical properties of two different permanent soft lining materials and their bonding to poly(methyl methacrylate) (PMMA) were compared. Both of the soft liners were heat‐cured commercial materials. The polymerization was carried out by conventional methods suggested by manufacturer, and the curing was done at the temperature of boiling water for 5, 15, 25, and 35 min. The sample groups were tested in the computer‐aided tensile‐testing machine at a rate of 2 mm/min. The slow rate helps the collection of more and more reliable data. At this time, the stress–strain curves were used to calculate ultimate tensile strength, elastic modulus, resilience, and toughness. The measurements were carried for PMMA, Molloplast B, Flexor, and a combination of PMMA/soft liner. After introducing the soft lining material on PMMA of the same thickness, the new material structure was more elastic than the original PMMA. Flexor showed adhesive failure at studied curing periods, but Molloplast B gave larger tear strength values and cohesive rather than adhesive failure at the 25‐min and 35‐min curing times. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 467–474, 2002
Detection of lead ion binding on bifunctional chelating/ion‐exchange resins by cross‐polarization/magic‐angle spinning solid‐state nuclear magnetic resonance
Authors: Wang Cheng‐Chien , Chen Chuh‐Yung
Published: August 2002

Solid‐state nuclear magnetic resonance (S‐NMR) can reveal much useful information, including conformations, stereoregularity, defect structures, and comonomer sequence. S‐NMR is especially useful for revealing microstructural differences that can alter local polymer chains. A series of bifunctional chelating/ion‐exchange resins, containing differing ratios of iminodiacetic acid to acetic acid, were synthesized. Cross‐polarization magic‐angle spinning (CP/MAS) 13C‐NMR was employed to measure conformation changes both before and after the bonding of ligands and lead ion adsorbed on bifunctional chelated/ion‐exchange resins in this investigation. From the 13C‐NMR spectra, as the lead ion was adsorbed by the iminodiacetic acid chelating group, the motion of molecular chain would be inhibited and the resonance peaks of the carboxylate anion at 170 ppm would shift downfield. Compared to the FTIR results, the downfield shift of the resonance peaks indicated that the bonding of carboxylate anion and lead ion adsorbed displayed an ionic trend. Furthermore, the bonding of the carboxylic group and lead ion adsorbed changed from ionic to covalent as the chelating group in bifunctional/ion‐exchange resins decreased. The linear relationship between the areas of those resonance peaks and the amount of lead ion adsorbed was obtained from the spectra fitting. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 919–928, 2002
Modeling of solid state polymer properties at the stage of synthesis: Fractal analysis
Authors: Kozlov G. V. , Temiraev K. B. , Shustov G. B. , Mashukov N. I.
Published: August 2002

The genetic relationship between the polymer structures in solution and the condensed state are discovered within the framework of fractal analysis. It allows us to predict and model the properties of polymers already at the stage of synthesis, using the representation of a cluster model of the amorphous polymer state. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1137–1140, 2002
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

Our 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

Dissolution 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

The 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

In 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

Three 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

The 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

Two 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

The 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

The 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

Dynamic 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

Monodispersed 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

Multiple 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

Objective

To 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).

Methods

SLE 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.

Results

We 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.

Conclusion

Sequential 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

Objective

To explore the Fc receptor–dependent handling of immune complexes (ICs) by the fixed mononuclear phagocytic systems (MPS) in patients with systemic lupus erythematosus (SLE).

Methods

The 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.

Results

In 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.

Conclusion

These 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

There 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.
Static magnetic field measurements in residences in relation to resonance hypotheses of interactions between power‐frequency magnetic fields and humans
Authors: Kaune W. T. , Banks R. S. , Linet M. S. , Hatch E. E. , Kleinerman R. A. , Wacholder S. , Tarone R. E. , Haines C.
Published: August 2002

Bowman et al. used epidemiologic data to test a model in which subjects were classified as being “in‐resonance” or “not‐in‐resonance” for 60‐Hz magnetic‐field exposures depending on single static magnetic‐field measurements at the centers of their bedrooms. A second paper by Swanson concluded that a single static magnetic‐field measurement is insufficient to meaningfully characterize a residential environment. The main objective of this study was to investigate exposure‐related questions raised by these two papers in two U.S. data sets, one containing single spot measurements of static magnetic fields at two locations in homes located in eight states, and the other repeated spot measurements (seven times during the course of one year) of the static magnetic fields at the centers of bedrooms and family rooms and on the surfaces of beds in 51 single‐family homes in two metropolitan areas. Using Bowman's criterion, bedrooms were first classified as being in‐resonance or not‐in‐resonance based on the average of repeated measurements of the static magnetic field measured on the bed where the presumed important exposure actually occurred. Bedrooms were then classified a second time using single spot measurements taken at the centers of bedrooms, centers of family rooms, or on the surfaces of beds, as would be done in the typical epidemiologic study. The kappa statistics characterizing the degree of concordance between the first (on‐bed averages) and second (spot measurements) methods of assessing resonance status were 0.44, 0.33, and 0.67, respectively. This level of misclassification could significantly affect the results of studies involving the determination of resonance status. Bioelectromagnetics 22:294–305, 2001. © 2001 Wiley‐Liss, Inc.
Magnetic fields produced by hand held hair dryers, stereo headsets, home sewing machines, and electric clocks
Authors: Kaune W.T. , Miller M.C. , Linet M.S. , Hatch E.E. , Kleinerman R.A. , Wacholder S. , Mohr A.H. , Tarone R.E. , Haines C.
Published: August 2002

A recent epidemiologic study reported associations between leukemia risk in children and their personal use of television (TV) sets, hair dryers, and stereo headsets, and the prenatal use by their mothers of sewing machines. To provide exposure data to aid in the interpretation of these findings, extremely and very low frequency (ELF and VLF) magnetic fields produced by a sample of each type of appliance were characterized in a field study of volunteers conducted in Washington DC and its Maryland suburbs. Questionnaire data regarding children's or mothers' patterns of usage of each type of appliance were also collected. ELF magnetic fields measured 10 cm from the nozzles of hair dryers were elevated over the ambient by a mean factor of 17 when these devices were in use. Fields near headsets being used to listen to music were not distinguishable from ambient levels except at frequencies below and well above 60 Hz and, even then, field levels were < 0.01 μT. Home sewing machines produced ELF magnetic fields that were elevated by a factor of 2.8 over ambient levels at the front surfaces of the lower abdomens of mothers. Estimated mean daily times of usage of hair dryers, stereo headsets, and sewing machines were 2.6, 19, and 17 minutes, respectively. These data and previously published data on TV sets, do not provide a consistent picture of increased (or decreased) leukemia risk in relation to increasing peak or time weighted average (TWA) ELF magnetic field exposure. The data could, however, conceivably be compatible with some more complex biophysical model with unknown properties. Overall, the results of this study provide little evidence supporting the hypothesis that peak or TWA ELF magnetic fields produced by appliances are causally related to the risk of childhood leukemia in children. Bioelectromagnetics 23:14–25, 2002. © 2002 Wiley‐Liss, Inc.
The development of the Drosophila genital disc
Authors: Sánchez Lucas , Guerrero Isabel
Published: August 2002

The imaginal discs of Drosophila melanogaster, which form the adult epidermal structures, are a good experimental model for studying morphogenesis. The genital disc forms the terminalia, which are the most sexually dimorphic structures of the fly. Both sexes of Drosophila have a single genital disc formed by three primordia. The female genital primordium is derived from 8th abdominal segment and is located anteriorly, the anal primordium (10 and 11th abdominal segments) is located posteriorly, and the male genital primordium from the 9th abdominal segment lies between them. In both sexes, only two of these three primordia develop to form the adult terminalia. The anal primordium develops in both sexes but, depending on the genetic sex, will form either male or female analia. However, only one of the genital primordia develops in each sex, forming either the male or the female genitalia. This depends on the genetic sex of the fly. Therefore, the genital disc is a very good experimental model of how the sex‐determination and homeotic genes — which determine cell identity — interact to direct the development of a population of cells into male or female terminalia. It has been proposed that the sexually dimorphic development of the genital disc is the result of an integrated genetic input, made up by the sex‐determination gene doublesex and the homeotic gene Abdominal‐B. This input acts by modulating the response to Hedgehog, Wingless, and Decapentaplegic morphogenetic signals. BioEssays 23:698–707, 2001. © 2001 John Wiley & Sons, Inc.
Organ formation in Drosophila: Specification and morphogenesis of the salivary gland
Authors: Bradley Pamela L. , Haberman Adam S. , Andrew Deborah J.
Published: August 2002

The Drosophila salivary gland has emerged as an outstanding model system for the process of organ formation. Many of the component steps, from initial regional specification through cell specialization and morphogenesis, are known and many of the genes required for these different processes have been identified. The salivary gland is a relatively simple organ; the entire gland comprises of only two major cell types, which derive from a single contiguous primordium. Salivary cells cease dividing once they are specified, and organ growth is achieved simply by an increase in size of individual cells, thus eliminating concerns about the potential unequal distribution of determinants during mitosis. Drosophila salivary glands form by the same cellular mechanisms as organs in higher organisms, including regulated cell shape changes, cell intercalation and directed cell migration. Thus, learning how these events are coordinated for tissue morphogenesis in an organism for which the genetic and molecular tools are unsurpassed should provide excellent paradigms for dissecting related processes in the more intricate organs of more complicated species. BioEssays 23:901–911, 2001. © 2001 John Wiley & Sons, Inc.
General properties of silated hydroxyethylcellulose for potential biomedical applications
Authors: Bourges Xavier , Weiss Pierre , Coudreuse Arnaud , Daculsi Guy , Legeay Gilbert
Published: August 2002

The general properties of hydroxyethylcellulose (HEC) grafted with 3‐glycidoxypropyltrimethoxysilane (GPTMS) or 3‐glycidoxypropylmethyldiethoxysilane (GPDMS) were studied for potential biomedical applications. The graft involved a Williamson reaction between the free hydroxyl function of HEC and the epoxy function of the two silanes. As the grafted silanes are in ionic form (sodium silanolate), this product remains in gel form at basic pH (>12.3) in aqueous solution. When pH decreases, sodium silanolate is transformed into silanol (2 or 3 silanol functions are carried by silicon, depending on the silane grafted). The silanols interreact, and the gel is transformed into a cross‐linking form at room or body temperature. Studies were conducted to optimise this product for specific uses.

Steam sterilization was used to compare self‐hardening as a function of the silane grafted. Our previous work indicated that HEC grafted with GPTMS has good reactivity, but requires high pH for dissolution, whereas dissolution occurs at lower pH with GPMDS. The rate of silanol condensation for silated HEC was then determined as a function of pH, temperature, type of silane, and the percentage grafted. Condensation rates were ascertained by the viscosity method, and gels were neutralized by different solutions to obtain buffered forms at various pH. The time required to obtain 105 mPa · s, with an initial state of 2500 mPa · s, was then calculated. Condensation was catalysed in acid or basic medium at a lower rate at pH 5.5–6.5, and a temperature rise increased the condensation rate, regardless of the pH or silane studied. Silanetriol was more reactive than silanediol. However, as HEC lost considerable viscosity after sterilization, further studies will be conducted to develop new polysaccharides grafted with silane. © 2002 John Wiley & Sons, Inc. Biopolymers 63: 232–238, 2002; DOI 10.1002/bip.10053
The impact of fluid‐dynamic‐generated stresses on chDNA and pDNA stability during alkaline cell lysis for gene therapy products
Authors: Chamsart S. , Patel H. , Hanak J. A. J. , Hitchcock A. G. , Nienow A. W.
Published: August 2002

Extensive tests have been carried out to assess the impact of fluid‐dynamic‐generated stress during alkaline lysis of Escherichia coli cells (host strain DH1 containing the plasmid pTX 0161) to produce a plasmid DNA (pDNA) solution for gene therapy. Both a concentric cylinder rheometer and two stirred reactors have been used, and both the alkaline addition and neutralization stages of lysis have been studied. Using a range of shear rates in the rheometer, stirrer speeds in the reactors, and different periods of exposure, their impact on chromosomal DNA (chDNA) and pDNA was assessed using agarose gel electrophoresis, a Qiagen Maxiprep with a polymerase chain reaction (PCR) assay, and a Qiagen Miniprep purification with a UV spectrophotometer. Comparison has been made with unstressed material subjected to similar holding times. These tests essentially show that under all these conditions, <2% chDNA was present in the pDNA solution, the pDNA itself was not fragmented, and a yield of 1 mg/g cell was obtained. These results, together with studies of rheological properties, have led to the design of a 60‐L, stirred lysis reactor and the production of high‐quality pDNA solution with <1% chDNA after further purification. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75:387–392, 2001.
Entrapment of dispersed pancreatic islet cells in CultiSpher‐S macroporous gelatin microcarriers: Preparation, in vitro characterization, and microencapsulation
Authors: Del Guerra S. , Bracci C. , Nilsson K. , Belcourt A. , Kessler L. , Lupi R. , Marselli L. , De Vos P. , Marchetti P.
Published: August 2002

Immunoprotection of pancreatic islets for successful allo‐ or xenotransplantation without chronic immunosuppression is an attractive, but still elusive, approach for curing type 1 diabetes. It was recently shown that, even in the absence of fibrotic overgrowth, other factors, mainly insufficient nutrition to the core of the islets, represent a major barrier for long‐term survival of intraperitoneal microencapsulated islet grafts. The use of dispersed cells might contribute to solve this problem due to the conceivably easier nutritional support to the cells. In the present study, purified bovine islets, prepared by collagenase digestion and density gradient purification, and dispersed bovine islet cells, obtained by trypsin and DNAsi (viability > 90%), were entrapped into either 2% (w/v) sodium alginate (commonly used for encapsulation purposes) or (dispersed islet cells only) macroporous gelatin microcarriers (CulthiSpher‐S, commonly used for the production of biologicals by animal cells). Insulin release studies in response to glucose were performed within 1 week and after 1 month from preparation of the varying systems and showed no capability of dispersed bovine islet cells within sodium alginate microcapsules to sense glucose concentration changes. On the contrary, bovine islet cells entrapped in CulthiSpher‐S microcarriers showed maintained capacity of increasing insulin secretion upon enhanced glucose concentration challenge. In this case, insulin release was approximately 60% of that from intact bovine islets within sodium alginate microcapsules. MTT and hematoxylineosin staining of islet cell‐containing microcarriers showed the presence of viable and metabolically active cells throughout the study period. This encouraging functional data prompted us to test whether the microcarriers could be immunoisolated for potential use in transplantation. The microcarriers were embedded within 3% sodium alginate, which was then covered with a poly‐L‐lysine layer and a final outer alginate layer. Maintained insulin secretion function of this system was observed, which raises the possibility of using microencapsulated CulthiSpher‐S microcarriers, containing dispersed pancreatic islet cells, in experimental transplantation studies. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 741–744, 2001.
Affinity ultrafiltration: Effects of ligand binding on selectivity and process optimization
Authors: Romero Jonathan , Zydney Andrew L.
Published: August 2002

The effective design of affinity ultrafiltration processes using a selective macroligand requires a detailed understanding of the effects of ligand‐binding interactions on product yield and purification. Theoretical calculations were performed to evaluate the performance of affinity diafiltration separations with both competitive and independent binding interactions for the product and impurity. The intrinsic selectivity for independent binding decreased during the diafiltration due to the increase in fractional impurity binding as the impurity is selectively removed. The opposite behavior was seen for competitive binding because the strongly bound product displaces the impurity from the binding sites. Purification‐yield diagrams were used to examine the effects of affinity‐ligand concentration and binding constants on the separation. Model calculations were in excellent agreement with experimental data for the separation of tryptophan isomers using bovine serum albumin as the steroselective macroligand. Simulations with a fixed number of diavolumes show a clear optimum in product yield and purification factor at an intermediate ligand concentration due to the competing effects of the intrinsic selectivity and the rate of impurity removal. These results provide an appropriate framework for the design and optimization of affinity ultrafiltration systems. © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 256–265, 2002.
Production of Acinetobacter radioresistens lipase with repeated batch culture in presence of nonwoven fabric
Authors: Lin Ying‐Chien , Wu Jau‐Yann , Chen Teh‐Liang
Published: August 2002

Cultivation of Acinetobacter radioresistens on n‐hexadecane for lipase production was investigated with repeated batch culture in the presence of a hydrophobic nonwoven fabric. Lipase production followed the growth‐associated model, and the repeated batch culture could achieve both high enzyme yield and increased volumetric productivity. The fabric was shown to be able to disperse n‐hexadecane, to adsorb the unused hydrocarbon, and to retain bioemulsifiers excreted from the cells; therefore, it enhanced cell growth and, in turn, lipase production. In the repeated batch culture in the absence of the fabric, lipase yield and volumetric productivity were found to be 21 U/mL and 875 U/L · h, respectively. However, if the fabric was equipped in the fermentor, lipase yield and volumetric productivity increased to 30 U/mL and 2500 U/L · h, respectively. The lipase production profile could be further improved by raising the amount of nitrogen source and, as a result, a lipase yield of 54 U/mL and a volumetric productivity of 2250 U/L · h were obtained. In this study we assess the beneficial effects of nonwoven fabric on lipase production. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 76: 214–218, 2001.