bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Temperature Semibatch Free Radical Copolymerization of Butyl Methacrylate and Styrene
Authors: Li Deheng , Hutchinson Robin A. 
Published: December 2006

AbstractHigh temperature starved feed semibatch solution polymerization is used to produce acrylic resins for automotive coatings. These operating conditions promote secondary reactions that have a strong impact on polymerization rate and polymer molecular weight (MW). This study experimentally investigates high temperature semibatch copolymerization of butyl methacrylate and styrene, a system subject to the combined effect of depropagation and penultimate propagation kinetics. A mechanistic model including these complexities is constructed in Predic®. With the termination rate coefficient fit to the semibatch results and all other coefficients taken from independent experiments, the model provides good predictions of monomer conversion and MW. Various representations of copolymer termination kinetics from the literature are compared to the values fit from experiment.
Hydrodynamics in a Gas‐Solids Fluidized Bed Using X‐Ray Fluoroscopy and Pressure Fluctuation Measurements
Authors: Wu Bangyou , He Zhengxing , Kantzas Apostolos , Bellehumeur Céline T. , Kryuchkov Sergey 
Published: December 2006

AbstractIn this work, non‐intrusive techniques were used to characterize the hydrodynamics in a gas‐solids bubbling fluidized bed using polyethylene powder and glass beads of comparable mean diameter (dp = 360 µm) but different density. X‐ray fluoroscopy measurements and pressure fluctuations were performed on a pseudo 2‐dimensional gas‐solids fluidized bed. Bubble properties were captured from X‐ray fluoroscopy measurements. Similarities and differences of flow behavior of the two particle systems were revealed from comparison of bubble properties. Bubble properities normally varied similary with operating conditions for the two particle systems, while bubble sizes for the glass beads system are larger than those for the polyethylene system. Wavelet analysis of pressure fluctuations was applied to investigate the gas and solids phase flow behavior. Multi‐scale flow behavior was extracted from the standard deviation of the decomposed coefficient series. Flow behavior due to particles and bubbles of different sizes were captured at different decomposition levels of pressure fluctuations, which is difficult to know from analysis of the original signal. Results extracted from X‐ray fluoroscopy and pressure fluctuation measurements were consistent, suggesting that conventional pressure fluctuation measurements can be effectively used for investigation of the bubbling behavior.
Dynamic Monte Carlo Simulation of Graft Copolymers Made with ATRP and Metallocene Catalysts
Authors: Al‐Harthi Mamdouh , Soares João B.P. , Simon Leonardo C. 
Published: December 2006

AbstractThe synthesis of polyolefin graft copolymers made with coordination polymerization was studied by dynamic Monte Carlo simulation. Narrow molecular weight distribution macromonomers, containing terminal vinyl groups made with atom‐transfer radical polymerization (ATRP), were incorporated randomly into the polyolefin backbone. In addition to average molecular weights and polydispersity index, the model predicts the complete molecular weight distribution (MWD) and branching density of the graft copolymer. The effect of the concentration of macromonomers on the grafting efficiency was also studied.
Simultaneous Data Reconciliation and Parameter Estimation in Bulk Polypropylene Polymerizations in Real Time
Authors: Prata Diego Martinez , Lima Enrique Luis , Pinto José Carlos 
Published: December 2006

AbstractThis work presents the implementation of a methodology for dynamic data reconciliation and simultaneous estimation of quality and productivity parameters in real time, using data from an industrial bulk Ziegler‐Natta propylene polymerization process. A phenomenological model of the real process, based on mass and energy balances, was developed and implemented for interpretation of actual plant data. The resulting nonlinear dynamic optimization problem was solved using a sequential approach on a time window specifically tuned for the studied process. Despite the essentially isothermal operation conditions, obtained results show that inclusion of energy balance constraints allows for increase of information redundancy and, as a consequence, for computation of better parameter estimates than the ones obtained when the energy balance constraints are not considered (Prata et al., 2005). Examples indicate that the proposed technique can be used very effectively for monitoring of polymer quality and identification of process malfunctions in real time even when laboratory analyses are scarce.
Modeling the Vulcanization of Rubber Blends
Authors: Likozar Blaž , Krajnc Matjaž 
Published: December 2006

AbstractKinetics and heat transfer during vulcanization of various blends of polybutadiene (BR) and polyisoprene (NR) were studied simultaneously using mechanistic approach for description of reaction kinetics. Fourier transform infrared spectroscopy (FTIR) was used to study the kinetics of accelerator and retarder chemistry. Differential scanning calorimetry (DSC) and dynamic rheometry were applied in order to retrieve the data for heat transfer modeling during induction period and kinetic modeling throughout the process. Model reaction scheme was based on one of the best possible proposed individual reaction mechanisms. Molecular modeling was applied to differentiate between the reactions of chemically similar species. Physical and chemical model parameters were calculated from the experimental data. A minimum of average rubber heat transfer coefficient was found to be at equal BR and NR weight fractions in the blend while activation energies of crosslinking and reversion reactions increased linearly with increasing BR weight fraction.
Batch and Semicontinuous Styrene–Butadiene Emulsion Copolymerization Reactions
Authors: Filho Aluisio Pinelli , Araujo Odair , Giudici Reinaldo , Sayer Claudia 
Published: December 2006

AbstractIn this work an experimental and simulation study of batch and semicontinuous styrene/butadiene emulsion copolymerization process was developed. The mathematical model combines the classical emulsion copolymerization equations, with mass balances, partitioning of components among all liquid phases, micellar and homogenous nucleation mechanisms and mass transfer equations between liquid and gaseous phases. Simulation results show good agreement with experimental measurements of conversion, average particle diameter and pressure.
Initiation Efficiency Reduction in Semicontinuous Styrene and Butyl Acrylate Emulsion Copolymerization Reactions
Authors: Hirota Wilson H. , Giudici Reinaldo , Sayer Cláudia 
Published: December 2006

AbstractThe decrease of initiation efficiency (radical entry efficiency) during seeded emulsion copolymerizations of styrene and butyl acrylate with different residual monomer reduction strategies was evaluated. Experiments were carried out using 50 and 99wt.% of styrene in monomer feed stream. Simulations were performed with a detailed mathematical model of the process that takes into account the diffusion control of initiation, propagation and termination. Results showed that the radical entry into polymer particles is strongly influenced by the aqueous phase kinetics and by the monomer solubility in aqueous phase. Simulation results were compared to experimental results of residual monomer and showed that the residual monomer content can be reduced by a temperature increase at the end of the polymerization. However, an additional feeding of more initiator, even when combined with such an increase of temperature, did not lead to a smaller residual monomer content due, mainly, the kinetic of termination in aqueous phase and radical anchoring. A model that accounts for the reduction of initiator efficiency (free radical entry efficiency) was successfully used to explain the behavior of the experimental observations and was able to correctly predict the qualitative trends of the effectiveness of different residual monomer reduction strategies.
Dynamics of Foaming of Polystyrene Particles
Authors: Salejova Gabriela , Kosek Juraj 
Published: December 2006

AbstractSeptember 24, 2006Summary: In this work, we address the industrially relevant problem of the foaming of expandable polystyrene (PS) impregnated by pentane as a traditional down‐stream processing in the suspension polymerization of styrene. Once the polystyrene foam is formed by means of a proper foaming agent, e.g., pentane or fluoro‐ or chloro‐hydrocarbons, the blowing agent diffuses out from the cellular structure. Environmental efforts call for the reduced consumption of blowing agents. The dynamics of foaming of polystyrene particles was recorded video‐microscopically in our laboratory as the sequence of images of expanding particle located in the small pressure cell placed under the microscope with sufficient depth of focus. The amount of pentane sorbed in PS was controlled by the length of the impregnation period and was determined independently by gravimetric measurements. Strong dependence of the structure of the produced foam and of the foaming dynamics on the amount of sorbed pentane, temperature and particle size is reported and explanations for some observed foaming phenomena are provided.
Bulk Polymerisation or Copolymerisation in a Novel Continuous Kneader Reactor
Authors: Fleury Pierre‐Alain 
Published: December 2006

AbstractA new type of kneader reactor is proposed for the continuous radical (co‐) polymerisation without solvent, based on the proven design of mature (kneader‐) dryer technology. The reactor has been developed to satisfy all major aspects required for (co‐) polymerisation while maintaining the safety and reliability of the previous mechanical design. The new kneader reactor offers a perfect combination of surface renewal and evaporative cooling to control temperature to high conversion (85 to 95%), even for bulk systems that have a strong gel effect (Trommsdorff's effect) and high exothermicity. The reactor can be tested batch‐wise to optimise the recipe, as shown in this work for bulk free radical polymerisation of methyl methacrylate (MMA). A simulation program was correlated to the experimental batch data to determine the optimum concentrations of initiator and of chain transfer agent to target a given molecular weight of PMMA. Design of a continuous kneader reactor to optimise the conversion as a function of residence time, to eliminate foam formation, and to produce copolymers without composition drift, is also presented.
Continuous Reactor Concepts with Superimposed Secondary Flow – Polymerization Process Intensification
Authors: Pauer Werner , Moritz Hans‐Ulrich 
Published: December 2006

AbstractDifferent unconventional continuous polymerization reactor concepts with superimposed secondary flow are presented. Exemplary polymerization reactions and the residence time distributions are discussed. In the case of the Taylor reactor polymerization process intensification is demonstrated by examples of emulsion and micro‐emulsion polymerization which actually results in an increase in space time yield of up to a factor of 50.
Non‐standard finite difference schemes for multi‐dimensional second‐order systems in non‐smooth mechanics
Authors: Dumont Yves , Lubuma Jean M.‐S. 
Published: December 2006

AbstractThis work is an extension of the paper (Proc. R. Soc. London 2005; 461A:1927–1950) to impact oscillators with more than one degree of freedom. Given the complex and even chaotic behaviour of these non‐smooth mechanical systems, it is essential to incorporate their qualitative physical properties, such as the impact law and the frequencies of the systems, into the envisaged numerical methods if the latter is to be reliable. Based on this strategy, we design several non‐standard finite difference schemes. Apart from their excellent error bounds and unconditional stability, the schemes are analysed for their efficiency to preserve some important physical properties of the systems including, among others, the conservation of energy between consecutive impact times, the periodicity of the motion and the boundedness of the solutions. Numerical simulations that support the theory are provided. Copyright © 2006 John Wiley & Sons, Ltd.
1‐Cyclohepta‐2,4,6‐trienyl‐selanes—a77Se NMR study: Indirect nuclear77Se13C spin–spin coupling constants and application of density functional theory (DFT) calculations
Authors: Wrackmeyer Bernd , Hernández Zureima García , Herberhold Max 
Published: December 2006

Abstract1‐Cyclohepta‐2,4,6‐trienyl‐selanes Se(C7H7)2(2c), RSeC7H7with R = Bu,tBu, Ph, 4‐FC6H4(12a,b,c,d) were prepared by the reaction of the corresponding silanes, Si(SeMe3)2and RSeSiMe3, respectively, with tropylium bromide C7H7Br. In spite of the low stability of the selanes even in dilute solutions and at low temperature, they could be characterised by their1H,13C and77Se NMR parameters. Coupling constants1J(77Se,13C) were measured and calculated by DFT methods at the B3LYP/6‐311+G(d,p) level of theory. The comparison of experimental and calculated coupling constants1J(77Se,13C) included numerous selenium carbon compounds with largely different SeC bonds, revealing a satisfactory agreement. Both the spin–dipole (SD) and the paramagnetic spin‐orbital (PSO) terms contributed significantly to the spin–spin coupling interaction, in addition to the Fermi contact (FC) term. Copyright © 2006 John Wiley & Sons, Ltd.
The clinical aspects of newborn screening: Importance of newborn screening follow‐up
Authors: James Philip M. , Levy Harvey L. 
Published: December 2006

AbstractThe aim of newborn screening is to identify presymptomatic healthy infants that will develop significant metabolic or endocrine derangements if left undiagnosed and untreated. The goal of ultimately reducing or eliminating irreversible sequelae is reached by maximizing test sensitivity of the primary newborn screening that measures specific analytes by a number of methodologies. Differentiation of true from false negatives is accomplished by the test specificity. This review discusses disorders for which, in general, there are available therapies and that are detected by routine and expanded newborn screening. Recommendations are presented for evaluation by a primary care physician, with confirmation by a metabolic or endocrinology specialist. Disorders are organized in tabular format by class of pathway or analyte, with attention to typical clinical presentations, confirmatory biochemical and molecular tests, and therapies. There are numerous challenges in clinical follow‐up, including diagnosis and appropriate understanding of the consequences of the disorders. The data required to meet these challenges can be acquired only by large scale longitudinal comprehensive studies of outcome in children identified by newborn screening. Only with such data can newborn screening fully serve families. © 2006 Wiley‐Liss, Inc. MRDD Research Reviews 2006;12:246–254.
Pilot programs in newborn screening
Authors: Pass Kenneth , Green Nancy S. , Lorey Fred , Sherwin John , Comeau Anne Marie 
Published: December 2006

AbstractThe term “pilot study” has been used over the years to describe the evaluation of the many elements involved in deciding whether a proposed condition should be added to a newborn screening (NBS) panel, and until recently, was unilaterally used to describe the evaluation of the assay to be used before the condition was officially adopted by a state for its newborn screening panel. Since Guthrie's introduction of screening for PKU, each time a new condition was added to the panel, the screening assay itself was validated through a population‐based trial, in which the test was performed with de‐identified samples to avoid association between the test result and the infant. This is considered by the laboratory as the “pilot phase” of adding a new condition. To advance the science of NBS, especially to accommodate new technologies that may provide new types of information (genetic versus physiological) for each new condition, pilot programs are essential. Involvement of the clinical community serves to improve these evaluations and provides the needed clinical validation of decisions made as a result of it. This paper describes the historical context of pilot programs in population‐based NBS that utilize laboratory‐based markers as indicators of concern; specifically, three applications that demonstrate different approaches to the use of pilots in adding conditions to a NBS panel are described. © 2006 Wiley‐Liss, Inc. MRDD Research Reviews 2006;12:293–300.
Universal newborn screening and adverse medical outcomes: A historical note
Authors: Brosco Jeffrey P. , Seider Michael I. , Dunn Angela C. 
Published: December 2006

AbstractUniversal newborn screening programs for metabolic disorders are typically described as a triumph of medicine and public policy in the US over the last 50 years. Advances in science and technology, including the Human Genome Project, offer the opportunity to expand universal newborn screening programs to include many additional metabolic and genetic conditions. Although the benefits of such screening programs appear to outweigh their costs, some critics have claimed that historical examples of inadvertent harm ensuing from false‐positive screening results and subsequent inappropriate medical treatment should make us wary of expanding universal newborn screening. In this essay, we report the results of a review of the published literature to assess whether the extension of screening from at risk populations to all newborns led to substantial morbidity and mortality from misguided medical treatment. We provide a historical overview of universal newborn screening programs in the United States, and then focus on six early NBS programs: congenital hypothyroidism, phenylketonuria, congenital adrenal hyperplasia, galactosemia, sickle cell disease, and maple syrup urine disease. Our comprehensive search of published sources did not reveal a widespread problem of harm ensuing from medical treatment of children with false positive screening test results. © 2006 Wiley‐Liss, Inc. MRDD Research Reviews 2006;12:262–269.
The role of National Library of Medicine® web sites in newborn screening education
Authors: Fomous Cathy , Miller Naomi 
Published: December 2006

AbstractExpanded newborn screening programs and subsequent detection of rare genetic disorders challenge parents and their medical providers to learn about the treatment and management of these disorders. Many people seek medical information on the Internet but may encounter requests for registration or fees, or find that resources are out of date, difficult to understand, or buried in advertisements. The U.S. National Library of Medicine (NLM), a component of the National Institutes of Health, provides web‐based resources that address the challenges of newborn screening education. These resources include MedlinePlus®, Genetics Home Reference™, ClinicalTrials.gov, and PubMed®. NLM websites are not commercial, do not require registration or fees, and provide varied levels of information for a continuum of audiences from low‐literacy consumers to health professionals. Using phenylketonuria as an example, this study describes the information that parents and their medical providers can find through NLM resources. NLM has embraced the digital age and provides the public with reliable, accurate, and up‐to‐date educational materials. © 2006 Wiley‐Liss, Inc. MRDD Research Reviews 2006;12:305–312.
Current status of newborn screening: Decision‐making about the conditions to include in screening programs
Authors: Watson Michael S. 
Published: December 2006

AbstractNewborn screening is considered a highly successful public health program that has resulted in the reduction of mortality, mental retardation, and other serious disabilities in thousands of children since the introduction of screening for phenylketonuria (PKU) in the 1960s. Programs are based in state public health departments such that each state independently reaches decisions as to which conditions should be mandated for inclusion in programs, leading to considerable variability among the states as to what is being screened. New technologies and knowledge of the genetics of many conditions have greatly expanded the number of conditions with potential for inclusion in newborn screening. © 2006 Wiley‐Liss, Inc. MRDD Research Reviews 2006;12:230–235.
An extension of Hill's three‐component model to include different fibre types in finite element modelling of muscle
Authors: Stojanovic B. , Kojic M. , Rosic M. , Tsui C. P. , Tang C. Y. 
Published: December 2006

AbstractMost of the proposed versions of the Hill's model use a sliding‐element theory, considering a single sarcomere. However, a muscle represents a collection of different fibre types with a large range in contractile properties among them. An extension of Hill's three‐component model is proposed here to take into account different fibre types. We present a model consisting of a number of sarcomeras of different types coupled in parallel with the connective tissue. Each sarcomere is modelled by one non‐linear elastic element connected in series with one non‐linear contractile element.Using the finite element method, in an incremental‐iterative scheme of calculating equilibrium configurations of a muscle, the key step is the determination of stresses corresponding to strain increments. The stress calculation procedure for the extended Hill's model is reduced to the solution of a number of independent non‐linear equations with respect to the stretch increments of the serial elastic elements in each sarcomere.Since the distribution of the specific fibre type is non‐uniform over the muscle volume, we have material heterogeneity which we modelled by using the so‐called ‘Generalized Isoparametric Element Formulation’ for functionally graded materials (FGMs).The proposed computational scheme is built in our FE package PAK, so that muscles of complex three‐dimensional shapes can be modelled. In numerical examples, we illustrate the main characteristics of the developed numerical model and some possibilities of realistic modelling of muscle functioning. Copyright © 2006 John Wiley & Sons, Ltd.