bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibition of α‐ketoglutarate dehydrogenase complex promotes cytochrome c release from mitochondria, caspase‐3 activation, and necrotic cell death
Authors: Huang Hsueh‐Meei , Ou Hsiu‐Chong , Xu Hui , Chen Huan‐Lian , Fowler Corinne , Gibson Gary E. 
Published: February 2004

AbstractMitochondrial dysfunction has been implicated in cell death in many neurodegenerative diseases. Diminished activity of the α‐ketoglutarate dehydrogenase complex (KGDHC), a key and arguably rate‐limiting enzyme of the Krebs cycle, occurs in these disorders and may underlie decreased brain metabolism. The present studies used α‐keto‐β‐methyl‐n‐valeric acid (KMV), a structural analogue of α‐ketoglutarate, to inhibit KGDHC activity to test effects of reduced KGDHC on mitochondrial function and cell death cascades in PC12 cells. KMV decreased in situ KGDHC activity by 52 ± 7% (1 hr) or 65 ± 4% (2 hr). Under the same conditions, KMV did not alter the mitochondrial membrane potential (MMP), as assessed with a method that detects changes as small as 5%. KMV also did not alter production of reactive oxygen species (ROS). However, KMV increased lactate dehydrogenase (LDH) release from cells by 100 ± 4.7%, promoted translocation of mitochondrial cytochrome c to the cytosol, and activated caspase‐3. Inhibition of the mitochondrial permeability transition pore (MPTP) by cyclosporin A (CsA) partially blocked this KMV‐induced change in cytochrome c (−40%) and LDH (−15%) release, and prevented necrotic cell death. Thus, impairment of this key mitochondrial enzyme in PC12 cells may lead to cytochrome c release and caspase‐3 activation by partial opening of the MPTP before the loss of mitochondrial membrane potentials. © 2003 Wiley‐Liss, Inc.
Repression of phospho‐JNK and infarct volume in ischemic brain of JIP1‐deficient mice
Authors: Im Joo‐Young , Lee Ko‐Woon , Kim Man Ho , Lee Si Hyoung , Ha Hye‐Yeong , Cho Ik‐Hyeun , Kim Doyeun , Yu Myung Sik , Kim Jung‐Bin , Lee Ja‐Kyeong , Kim Young Joo , Youn Byung‐Woo , Yang Sung‐Don , Shin Hee‐Sup , Han Pyung‐Lim 
Published: February 2004

AbstractMice lacking JIP1, a scaffold protein that organizes JNK pathway components, were constructed independently by two groups. The proposed in vivo function, however, remains contradictory; One study reported that targeted disruption of the jip1 caused embryonic death due to the requirement of JIP1 for fertilized eggs (Thompson et al. [2001] J. Biol. Chem. 276:27745–27748). In contrast, another group (Whitmarsh et al. [2001] Genes Dev. 15:2421–2432) demonstrated that JIP1‐deficient mice were viable and that the JIP1 null mutation inhibited the kainic acid‐induced JNK activation and neuronal death. The current study was undertaken to re‐elucidate the in vivo roles of JIP1 using newly generated JIP1 knockout mice. Our JIP1‐deficient mice were viable and healthy. The transient focal ischemic insult produced by middle cerebral artery occlusion (MCAO) strongly activated JNK in brain of jip1+/+, jip1+/−, and jip1−/− mice. Increased JNK activity was sustained for more than 22 hr in jip1+/+ and jip1+/−, whereas it was repressed rapidly in jip1−/−. Concomitantly, the infarct volume produced by the ischemic insult in jip1−/− was reduced notably compared to that in jip1+/+ brain. These results suggest that JIP1 plays a pivotal role in regulating the maintenance of phosphorylated JNK and neuronal survival in postischemic brain, but is not essential for JNK activation and early development. © 2003 Wiley‐Liss, Inc.
Brain transplantation of genetically engineered human neural stem cells globally corrects brain lesions in the mucopolysaccharidosis type VII mouse
Authors: Meng Xing‐Li , Shen Jin‐Song , Ohashi Toya , Maeda Hiroshi , Kim Seung Up , Eto Yoshikatsu 
Published: February 2004

AbstractIn the present study, we investigated the feasibility of using human neural stem cells (NSCs) in the treatment of diffuse central nervous system (CNS) alterations in a murine model of mucopolysaccharidosis VII (MPS VII), a lysosomal storage disease caused by a genetic defect in the β‐glucuronidase gene. An immortalized NSC line derived from human fetal telencephalon was genetically engineered to overexpress β‐glucuronidase and transplanted into the cerebral ventricles of neonatal MPS VII mouse. Transplanted human NSCs were found to integrate and migrate in the host brain and to produce large amount of β‐glucuronidase. Brain contents of the substrates of β‐glucuronidase were reduced to nearly normal levels, and widespread clearing of lysosomal storage was observed in the MPS VII mouse brain at 25 days posttransplantation. The number of engrafted cells decreased markedly after the transplantation, and it appears that the major cause of the cell death was not the immune response of the host but apoptotic cell death of grafted human NSCs. Results showed that human NSCs would serve as a useful gene transfer vehicle for the treatment of diffuse CNS lesions in human lysosomal storage diseases and are potentially applicable in the treatment of patients suffering from neurological disorders. © 2003 Wiley‐Liss, Inc.
Temperature oscillation calorimetry by means of a Kalman‐like observer: the joint estimation of Qr and UA in a stirred tank polymerization reactor
Authors: Freire Fábio Bentes , Giudici Reinaldo 
Published: February 2004

AbstractThe present work is concerned with the joint estimation of the rate of heat produced by the emulsion terpolymerization of styrene, butyl acrylate and methyl methacrylate (Qr), and the overall heat transfer coefficient (UA) from temperature measurements and reactor heat balance. By making specific assumptions on the dynamics of the parameters UA and Qr, we designed a Kalman‐like observer to carry out the estimation of these two time‐varying parameters, without the need for neither additional measurements nor on‐line samples. Temperature oscillations are induced in the cooling jacket in order to ensure the observability of the system. One further aspect of our approach is that it only requires the reactor energy balance to perform the estimation.
Simulating cumulative distributions under transient conditions in well‐mixed, continuous and batch polymerization reactors
Authors: Sachs William H. 
Published: February 2004

AbstractInstantaneous property methods are applied to the simulation of cumulative distributions of polymer chain architecture in well‐mixed, continuous and batch reactors. We show how cumulative distributions can be simulated under transient conditions using a general convolution integral and suitable output from a dynamic reactor simulation package such as POLYREDTM. We also show how the state equations that describe a polymerizing system can be augmented for direct simulation of these distributions. Examples of the impact of catalyst kinetics, reactor operating policies, and process upsets on the molecular weight distribution of bimodal high molecular weight polyethylene produced in well‐mixed, stirred‐bed gas‐phase reactors are simulated for a binary transition‐metal catalyst system.
Butyl acrylate/methyl methacrylate latexes: adhesive properties
Authors: Jovanović Renata , Ouzineb Keltoum , McKenna Timothy F. , Dubé Marc A. 
Published: February 2004

AbstractIn this study, butyl acrylate/methyl methacrylate (BA/MMA) latexes of bimodal molecular weight and particle size distribution were prepared in a multi‐step process by seeded conventional emulsion and seeded miniemulsion polymerization. For the conventional emulsion case, a BA/MMA batch copolymerization was conducted as a first step (seed generation) and was followed by a monomer addition step to ensure particle growth. In a third step, a BA/MMA pre‐emulsified mixture was added to generate a second particle population. For the miniemulsion case, a BA/MMA copolymerization was carried out as a first step (seed generation) and was followed by a monomer addition step. The addition of a BA/MMA miniemulsion served to generate a bimodal particle size and molecular weight distribution. The final latexes were coated onto a polyethylene terephthalate carrier, dried and their performance as pressure‐sensitive adhesives was evaluated using tack, peel and shear adhesion measurements. Structure‐property relationships between the adhesive properties and the weight‐average molecular weight and average particle size were examined. Even though the polymers obtained by miniemulsion showed better shear resistance, their shear resistance was low. There was no statistically significant difference in peel resistance of the polymers obtained by the two reactions. While a significant difference in tackiness between the two emulsion procedures was found when the adhesives were tested using the less sensitive, rolling ball test, no differences were found when they were tested using a loop tack test.
An experimental and numerical study on crystallization analysis fractionation (Crystaf)
Authors: Anantawaraskul Siripon , Soares João B.P. , Wood‐Adams Paula M. 
Published: February 2004

AbstractCrystallization analysis fractionation (Crystaf) is a new technique used to estimate the chemical composition distribution (CCD) of semi‐crystalline copolymers. In this study, the effect of chain microstructure and operation parameters on Crystaf profiles was investigated using a series of ethylene/1‐hexene copolymers and their blends. The Crystaf profiles were also modeled via stochastic simulation based on the distribution of average ethylene sequence lengths.
Chemical composition distribution of multicomponent copolymer chains
Authors: Anantawaraskul Siripon , Soares João B.P. , Wood‐Adams Paula M. 
Published: February 2004

AbstractProbability theory was used to model the microstructure of copolymer chains. Specifically, we derived analytical expressions to describe the chemical composition distribution of multicomponent random copolymers and the longest monomer sequence length distribution of binary copolymers. The results agree with Stockmayer's distribution for binary copolymers and with Monte Carlo simulations for multicomponent copolymers.
A new tool for the study of polymerization under supercritical conditions – preliminary results
Authors: Fortini Sophie , Lavanchy Frédéric , Nising Philip , Meyer Thierry 
Published: February 2004

AbstractEfficient stirring is needed to realize heat flow analysis with a thermally homogeneous medium. Because dispersion polymerization with supercritical fluids can be destabilized under stirring, a preliminary target has been to find a compromise between synthesis and basic reaction calorimetry requirements. This paper describes the use of poly (dimethylsiloxane) macromonomer with a molecular weight 5000 g/mol as stabilizer for the dispersion polymerization of methyl methacrylate in supercritical carbon dioxide. The effect of stirring speed and stabilizer concentration has been examined. This study has shown that poly (methyl methacrylate) can be produced at high yield and molecular weight using 10 wt% (respect to monomer) poly (dimethylsiloxane) macromonomer at stirring speeds up to 600 rpm. A polymerization enthalpy of −57.6±2 kJ/mol has been calculated being in good agreement with previously reported data. Thus, preliminary results for the heat balance using the newly developed high pressure reaction calorimeter for supercritical fluid applications have shown the important potential of reaction calorimetry to promote supercritical fluid technologies at industrial scale allowing for the determination of kinetics and thermodynamic and safety data, respectively.
On growth patterns of branched polymer architectures
Authors: Iedema Piet D. , Hoefsloot Huub C.J. 
Published: February 2004

AbstractIn nature trees may have many different forms and so have all natural branched structures. Differences in branched architectures of synthetic polymers can only be explained by kinetics. We compare radical polymerization of low density Polyethylene (PE) and PE polymerization with Constrained Geometry Catalyst (CGC) metallocene. The architectures generated by our synthesis algorithms revealed marked differences between the two PE‐systems. Metallocene‐PE turned out to be more comb‐like. This could partially be explained by analyzing growth patterns of the two PE types as incorporated in the architecture synthesis algorithms.
Compartmentalisation in miniemulsions: exploration of compartmentalisation and some interesting end‐uses
Authors: Ouzineb Keltoum , Graillat Christian , Dubé Marc A. , Jovanović Renata , McKenna Timothy F. 
Published: February 2004

AbstractInfrared spectroscopy and differential scanning calorimetry were used to demonstrate that miniemulsions of relatively hydrophobic monomers are compartmentalised during the reaction. Experiments with blends of miniemulsions of different composition revealed that no mass transfer takes place between droplets of different composition in the same reactor. In addition, it was shown that it is possible to make high solids content, low viscosity latexes with bimodal particle size and molecular weight distributions because of this property.
Batch process monitoring and its application to polymerization systems
Authors: Ündey Cenk , Ertunç Sinem , Tatara Eric , Teymour Fouad , Çιnar Ali 
Published: February 2004

AbstractSlight changes in raw material properties or operating conditions during critical periods of operation of batch and semi‐batch polymerization reactors may have a strong influence on reaction mechanism and impact final product quality. Online process monitoring, fault detection, fault diagnosis, and product quality prediction in real‐time ensure safe reactor operation and warn operators about excursions from normal operation that may lead to deterioration in product properties. Multivariate statistical process monitoring and quality prediction using multiway principal components analysis and multiway partial least squares have been successful in detecting abnormalities in process operation and product quality. When abnormal process operation is detected, fault diagnosis tools are used to determine the source cause of the deviation. Illustrative case studies are presented via simulated polyvinyl acetate polymerization.
On‐line monitoring of all‐acrylic emulsion polymerization reactors by Raman spectroscopy
Authors: Elizalde Oihana , Leiza Jose Ramon , Asua José M. 
Published: February 2004

AbstractFourier Transform Raman spectroscopy was used as an on‐line sensor in order to monitor high solids content (50 wt%) n‐BA/MMA emulsion copolymerization reactions. Due to the similarity of the chemical structure of the monomers, no separate bands could be detected for each monomer, and therefore a multivariate calibration technique was required (Partial Least Squares Regression, PLSR). Using experimental data from several semi‐batch reactions independent PLSR models were built for the solids content, cumulative copolymer composition and unreacted amounts of n‐BA and MMA. Those models were experimentally validated by monitoring reactions not used for calibration. It is demonstrated that FT‐Raman spectroscopy can be successfully applied to on‐line monitor emulsion polymerization reactors. This technique also shows a high potential for process control purposes because independent information about several molecular properties can be obtained from a single apparatus.
Branching and crosslinking in emulsion polymerization
Authors: Bouvier‐Fontes Ludivine , Pirri Rosangela , Arzamendi Gurutze , Asua José M. , Leiza Jose R. 
Published: February 2004

AbstractThe seeded semibatch emulsion polymerization of butyl acrylate (BA) with allyl methacrylate (AMA) and butanediol diacrylate (BDA) was used to study the influence of the crosslinkers on the kinetics, branching and crosslinking density, gel fraction and sol MWD produced during the experiments carried out at 80°C using potassium persulfate as initiator. Surprisingly, the most reactive crosslinker, BDA, produced the less crosslinked, branched and gel containing polymer. These results were explained with the help of a mathematical model in terms of cyclization reactions and diffusion controlled propagation and termination reactions.
Comparing near infrared and Raman spectroscopy for on‐line monitoring of emulsion copolymerization reactions
Authors: Reis Marlon M. , Araújo Pedro H.H. , Sayer Claudia , Giudici Reinaldo 
Published: February 2004

AbstractIn this work, Raman and Near InfraRed (NIR) spectroscopies are evaluated for the monitoring of different semicontinuous emulsion homo‐ and co‐polymerization reactions. Important process variables, namely monomer concentrations and average particle sizes, were monitored by both techniques under realistic conditions that would be found in an industrial environment (e.g. low signal/noise ratio, probe placed in the reaction medium). Results suggest that Raman and NIR are suitable for on‐line monitoring of emulsion polymerization reactions and that the success of their application is mainly related to representative calibration models used for the estimation of the properties of interest.
Butyl acrylate and vinyl acetate semicontinuous emulsion copolymerizations: study of stabilization performance
Authors: Araújo Pedro H. H. , Giudici Reinaldo , Sayer Claudia 
Published: February 2004

AbstractThe use of small amounts of carboxylic monomers in industrial recipes with high solids content enhances colloidal stability due to the presence of carboxylic groups on the outer surface of the polymer particles. Understanding the relationship between several different but interdependent phenomena, including particle nucleation, kinetics, particle aggregation, monomer type, solids content, the role of the carboxylic monomer and the influence of reaction temperature may improve the control over particle size and latex stability. In this work, the kinetics and stabilization performance of semicontinuous vinyl acetate (VA) and butyl acrylate (BA) emulsion copolymerization reactions are studied under different reaction temperatures, acrylic acid (AA) concentrations, solids contents and monomer feed compositions. Results show that choosing optimal AA concentrations and reaction temperatures are key factors in order to enhance the stabilization performance in semicontinuous VA/BA emulsion copolymerization.
Analysis of mass transport limitation during emulsion polymerization using reaction calorimetry and conductivity measurement
Authors: Henninger Björn , Rehfeld Matthias , Pauer Werner , Moritz Hans‐Ulrich 
Published: February 2004

AbstractThe seeded emulsion polymerization of styrene was investigated by reaction calorimetry in combination with conductivity measurements using the RC1e calorimeter (Mettler Toledo). Varying the stirrer speed showed the existence of mass transport limitation in the lower speed range. For the case of using the autoclave HP60 with an anchor stirrer a minimum stirrer speed of 400 rpm is required to be sure of adequate mixing in the reactor.
Analysis of particle formation under monomer‐starved conditions in emulsion polymerization reactors
Authors: Sajjadi Shahriar , Yianneskis Michael 
Published: February 2004

AbstractAn important characteristic of monomer‐starved nucleation in semibatch reactors is that the rate of growth of particles is controlled by the rate of monomer addition. The reduced rate of growth of particles prolongs the nucleation interval by slowing down the rate of emulsifier micelle depletion and forms a larger number of particles (Np). Model calculations show how Np varies with the formulation parameters as the monomer‐flooded nucleation shifts into monomer‐starved one. Particle formation in the intermediate conversion of interval III of the styrene batch emulsion polymerization also showed an enhancement because of a low rate of growth of newly formed particles. However, at a higher conversion, the rate of particle formation decreased significantly. Modeling results show that the reduction in the rate of particle formation at high conversions could not be simply explained by existing theories which rely on the decrease in monomer concentration in the aqueous phase as a means to explain the decrease in the rate of radical capture.
Diffusion‐controlled reactions in vinyl chloride suspension polymerization
Authors: De Roo Tony , Heynderickx Geraldine J. , Marin Guy B. 
Published: February 2004

AbstractThe vinyl chloride suspension polymerization is kinetically modeled with a general approach for the independent calculation of diffusion effects on polymerization reactions. For the initiator decomposition, propagation and termination an apparent rate coefficient is determined, built up from two contributions: the intrinsic rate coefficient and a diffusional contribution. The diffusional contribution is calculated with the Smoluchowski model, the diffusion coefficients being determined from the free volume theory. When applying the free volume theory no adjustable parameters are used. The intrinsic rate coefficients are taken from the literature. Hence, a model without any adjustable parameters is obtained. Calculations show that the glass effect appears only at (very) high conversions. Due to the cage effect the initiator efficiency decreases strongly as soon as the monomer phase has disappeared. The gel effect always occurs in the polymer‐rich phase and results in a decrease of the termination rate coefficient at the start of the third stage in the polymerization process. There is a good agreement with experimental results.
Continuous styrene – methyl methacrylate – glycidyl methacrylate terpolymerizations in homogeneous mixtures with supercritical carbon dioxide
Authors: Beuermann Sabine , Buback Michael , Gadermann Moritz , Jürgens Michael , Günzler Fabian 
Published: February 2004

AbstractFree‐radical terpolymerizations of styrene, methyl methacrylate, and glycidyl methacrylate were carried out in a tubular reactor in the presence of 20 wt.% CO2 at temperatures between 120 and 180°C and pressures of 300 and 350 bar. The number average molecular weights, MN, were mostly between 2000 and 3000 g·mol−1 and polydispersity indices around 2. In part of the experiments molecular weights were controlled by n‐dodecyl mercaptan serving as the chain‐transfer agent. PREDICI modeling indicates that the targeted molecular weights of MN∼2500 g·mol−1 and polydispersities around 2 may also be reached by using an initiator cocktail, a mixture of two initiators with significantly different decomposition rate coefficients. The predictions are confirmed experimentally.
Simulation model for urea‐formaldehyde reactors
Authors: Mejdell Thor , Schjønsby Hans K. 
Published: February 2004

AbstractA comprehensive simulation model for urea/formaldehyde (UF)‐resins has been developed. The model utilizes kinetic results reported in the literature for low molecular weight systems and extends these to higher molecular weight systems by using a functional group approach. The model consists of‐ 9 functional groups, 5 urea groups and 4 formaldehyde groups.‐ 9 reactions, 5 methylolation reactions and 4 condensation reactions. In all these reactions both the formation and the decomposition reactions are included.All the kinetic constants are pH and temperature dependent.Two batch runs with different U/F ratios were used to adjust a couple of model parameters. Samples from these batch runs were analyzed with HPLC for low molecular weight compounds, and GPC for the average molecular weight. A run with continuous IR measurement showed excellent fit for the formaldehyde concentration. The model also estimates the viscosity from the functional groups.