bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diastereomeric difference of inclusion modes between (−)‐epicatechin gallate, (−)‐epigallocatechin gallate and (+)‐gallocatechin gallate, with β‐cyclodextrin in aqueous solvent
Authors: Ishizu Takashi , Kajitani Shinya , Tsutsumi Hiroyuki , Yamamoto Hideji , Harano Kazunobu 
Published: March 2008

AbstractInclusion complexes of (−)‐epicatechin gallate (ECg) as well as (+)‐gallocatechin gallate (GCg) and β‐cyclodextrin (β‐CD) in an aqueous solution were investigated using several NMR techniques and a computational method. ECg and EGCg formed a 1:1 complex with β‐CD, in which the A ring and a portion of the C ring were included from the wide secondary hydroxyl group side of the β‐CD cavity, and the B and B′ rings were left outside the cavity. GCg formed a 1:2 complex with β‐CD, in which the A and B rings of GCg were included by two molecules of β‐CD. The difference between the two modes of inclusion of the 1:1 complex of ECg, EGCg·β‐CD and the 1:2 complex of GCg·β‐CD might have resulted from the size of the space between the B and B′ rings in aqueous solution. As a result of nueclear Overhauser effect (NOE) experiments, GCg was considered to have a large enough space between the B and B′ rings to include the B ring in the β‐CD cavity; on the other hand, ECg and EGCg have no such large space. Copyright © 2008 John Wiley & Sons, Ltd.
Copolymerization of 2‐Acrylamido‐2‐methyl‐1‐propanesulfonic Acid and 1‐Vinylimidazole in Inverse Miniemulsion
Authors: Wiechers Susann , Schmidt‐Naake Gudrun 
Published: March 2008

AbstractThe copolymerization behavior of the acidic monomer 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (APSA) and 1‐vinylimidazole in inverse miniemulsion was studied under various conditions. Initially, different surfactants and surfactant concentrations were investigated. After determining a suitable composition of the miniemulsion, changes in the reaction behavior under different pH values and monomer feed compositions were studied. The highest polymerization rates could be produced under neutral conditions over all monomer feed ratios. The addition of acid or base to change the pH value of the monomer mixture also has influence on the polymers obtained. The thermal stability, rheological stiffness and intrinsic viscosity increase when Na‐APSA is incorporated.magnified image
Chain Length Distributions of Polyolefins Made in Stopped‐Flow Reactors for Non‐Instantaneous Site Activation
Authors: Soares João B. P. , Hamielec A. E. 
Published: March 2008

AbstractWe developed an analytical solution to describe how the chain length distribution (CLD) of polymers made with coordination polymerization catalysts vary as a function of time for very short polymerizations considering non‐instantaneous site activation. This solution is an extension of our previous analytical expression for instantaneous site activation. We validated the analytical solution with dynamic Monte Carlo simulation and obtained excellent agreement. Simulation results indicate that, unless the catalyst activation rate is much lower than the propagation rate, it will have only a minor effect on the initial shape of the CLD of polymers made in stopped‐flow reactors (SFR). We also show how incorrect polymerization kinetic parameters may be estimated when assuming instantaneous site activation when this hypothesis is not applicable to the polymerization data under investigation.magnified image
Continuous Soluble Ziegler‐Natta Ethylene Polymerizations in Reactor Trains, 2 – Estimation of Kinetic Parameters from Industrial Data
Authors: Embiruçu Marcelo , Prata Diego Martinez , Lima Enrique Luis , Pinto José Carlos 
Published: March 2008

AbstractWe show that it is possible to estimate kinetic parameters for complex mechanistic polymerization models from available industrial data. A methodology is developed for efficient handling and reconciliation of industrial data and is then applied to allow estimation of kinetic parameters for industrial ethylene polymerizations performed in reactor trains using soluble Ziegler‐Natta catalysts. The parameter estimation procedure is formulated as a nonlinear optimization procedure subject to hard and soft model and process constraints. Parameter estimates obtained for the catalyst system allow a very good description of actual industrial data used during the estimation process and also allow very good prediction of process performance when completely new operating conditions are considered. It is concluded that complex phenomenological models can be successfully fitted to actual industrial processes without the need to carry out extensive experimental tests in the laboratory.magnified image
Continuous Soluble Ziegler‐Natta Ethylene Polymerizations in Reactor Trains, 3 – Influence of Operating Conditions upon Process Performance
Authors: Embiruçu Marcelo , Pontes Karen , Lima Enrique Luis , Pinto José Carlos 
Published: March 2008

AbstractThe behavior of continuous solution ethylene/but‐1‐ene polymerizations through Ziegler‐Natta catalysts is analyzed, based on a previously developed mathematical model. In order to do that, dynamic simulations are carried out and process responses are analyzed as functions of process operating policies and flowsheet configuration, at conditions that resemble the actual operation of industrial sites. It is shown that system responses are highly nonlinear and very sensitive to disturbances of the operating conditions and that catalyst decay is of fundamental importance for proper understanding of process behavior. Results indicate that mixing conditions inside the reactor vessels exert a significant impact upon the final polymer quality and can be manipulated for in‐line control of final resin properties. Finally, it is shown that the development of feed policies, based on the use of lateral feed streams, allows the simultaneous control of melt flow index, stress exponent and polymer density of the final polymer resin.magnified image
Critical branching processes in neural networks
Authors: Levina Anna , Herrmann J. Michael , Denker Manfred 
Published: March 2008

AbstractSelf‐organized criticality generates complex behavior in systems of simple elements. It is observed in various biological neural systems and has been analyzed in simplified model systems. Branching processes often considered to be a mean‐field approximation to the dynamics of critical systems. Here we study the validity of such an approximation for the case of a neural network. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coupled nonlinear effects in modeling field emission from CNTs
Authors: Melnik R.V.N. , Mahapatra D. Roy , Sinha N. , Yeow J.T.W. 
Published: March 2008

AbstractField emission from carbon nanotubes (CNTs) is a complex process involving a range of physical effects and phenomena. In this paper, we systematically develop a multiphysics model to describe this process. We integrate the model numerically to estimate the output current from a CNT based field emission device. Numerical simulations have been able to capture the transients in current as observed in actual experiments. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interior point methods for linear complementarity problems
Authors: Potra Florian A. 
Published: March 2008

AbstractA short survey of interior point methods for linear complementarity problems with emphasis on algorithms that have both polynomial complexity and superlinear convergence is presented. Some recent results obtained by the author and his collaborators are briefly summarized and several directions of future research are proposed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal control of robots under stochastic uncertainty: robust feedback control
Authors: Schacher Michael 
Published: March 2008

AbstractThe most important aspect in the optimal control and design of manipulators is the determination of the basic movement, i.e. the calculation of the optimal trajectory on which the robot has to move. Having an optimal reference trajectory and an optimal open‐loop control, there is the need of control corrections by applying a certain feedback control. Different attempts exist for this.In this article a method will be shown which is based on classical control theory, that works with cost functions being minimized. The aim is to take into account stochastic parameter variations in order to obtain robust optimal feedback controls. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Applications of homogenization techniques to the electrical conduction in biological tissues
Authors: Amar Micol , Andreucci Daniele , Bisegna Paolo , Gianni Roberto 
Published: March 2008

AbstractWe study a family of problems set in a finely mixed periodic medium, modelling electrical conduction in biological tissues. We prove a unified derivation of these different schemes from the Maxwell equations in the quasi‐stationary approximation and we investigate the behaviour of the corresponding macroscopic models. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface integral methods for high‐frequency electromagnetic scattering
Authors: Ganesh M. , Hawkins S. C. 
Published: March 2008

AbstractSurface integral equation based methods are advantageous for simulation of electromagnetic waves scattered by three dimensional obstacles, because they efficiently reduce the dimension of the problem and are robust for high‐frequency problems. However, the cost of setting up the associated discretized dense linear systems is prohibitive due to evaluation of highly oscillatory magnetic and electric dipole surface integral operators using standard cubatures. The computational complexity of evaluating such integrals depends on the incident wave frequency, and the size and shape of the obstacles. In this work we discuss a surface integral reformulation of the scattering problem that involves evaluation of surface integrals with a highly oscillatory physical density, and discuss methods for efficient evaluation of such integrals for a class of smooth three dimensional scatterers whose diameter is a large multiple of the incident wavelength. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On wear pattern generation in elastic systems
Authors: Hoffmann Norbert 
Published: March 2008

AbstractIn systems with moving contacts spatially periodic wear patterns may appear on the contact partners surfaces. There is agreement that the patterns are related to structural resonances. Using a simple model with a moving point contact and an idealized wear model the present work reviews some of the present understanding of wear‐pattern generation. Then the effect of randomly specified relative velocities on the wavelength selection process is investigated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evaluating drug toxicity signals: is a hierarchical classification of evidence useful or a hindrance?
Authors: van Staa T. P. , Smeeth L. , Persson I. , Parkinson J. , Leufkens H. G. M. 
Published: March 2008

AbstractPurposeOnly randomized clinical trials (RCTs) are deemed suitable to determine causality, as epidemiological studies are considered not ‘robust’. The objective of this study was to evaluate whether causality should remain the only consideration with drug toxicity signals. Cyclooxygenase‐2 (Cox‐2) inhibitors provided an example.MethodsOur study population included patients aged 40+ years prescribed Cox‐2 inhibitors in the General Practice Research Database (GPRD) (N = 150 000). We estimated the risks of upper gastrointestinal (GI) events and myocardial infarction (MI). Attributable risks were estimated using simulation methodology based on various hypothetical scenarios.ResultsThe risk–benefit profile was strongly related to the rate of GI events. With a RCT incidence, the GI benefits would exceed MI risks. With a ‘real‐life’ GI incidence, the benefits did not exceed the risks substantially. The onset and offset of drug effects also predicted the magnitude of both risks and benefits. If risks and benefits occurred in different sub‐groups, the risk–benefit profile varied substantially. Also, it was found that any restriction of use to patients at high risk of drug toxicity may not improve the risk–benefit profile when this restriction affected patients who would benefit most.ConclusionsWe conclude that rigid classification of evidence is not appropriate in the monitoring of risks and benefits and all valid study evidence—not only that derived from a RCT— needs to be included. The first priority should be to consider the potential impact of a drug toxicity signal. Copyright © 2008 John Wiley & Sons, Ltd.
Current Distribution on the Substrate in a Vacuum Arc Deposition Setup
Authors: Baranov Oleg , Romanov Maxim 
Published: March 2008

AbstractThe effect of a magnetic field generated by a planar magnetron on the ion current distribution on the substrate has been investigated as a function of the substrate voltage and gas pressure for two configurations of the magnetic field. The probe and the substrate were biased by negative potentials of −60 to −280 V with respect to the grounded anode, in order to collect the saturated ion current and investigate the influence of the magnetron magnetic field on the distribution of the ion flux of the vacuum arc source. It was shown that the planar magnetron placed under the substrate strongly affects the ion current and ion current distribution near the substrate. For a broad pressure range, the maximum ion flux collected by the probe increased by 40%, while the net ion current to the substrate increased by 20%. We have demonstrated that the ion current increased by 18%, and maximum ion current density increased by 40%. The results were explained in terms of the plasma flux interaction with the magnetic field of the magnetron. The setup may be suitable for controlling ion flux density on large substrates.magnified image
Mechanical and thermal behaviour of flexible food packaging polymeric films materials under high pressure/temperature treatments
Authors: Galotto M J , Ulloa P.A , Hernández D. , Fernández‐Martín F. , Gavara R. , Guarda A. 
Published: March 2008

AbstractThe effect of high‐pressure processing on mechanical and thermal properties of four complex packaging materials (polyethylene/ethylene vinyl alcohol/ polyethylene: PE/EVOH/PE; metallized polyester/polyethylene: PETmet/PE; polyester/polyethylene: PET/PE; polypropylene SiOx recovered: PPSiOx) was studied. Pouches of the different materials containing distilled water or olive oil as food simulants, as well as empty ones, were subjected to 400  MPa for 30  min, at temperatures of 20 or 60°C. Delamination and wrinkling were a general consequence of the high‐pressure processing of multilayer polymeric systems. However, no significant changes were observed regarding the mechanical properties of PE containing laminates after pressurization. PPSiOx underwent significant modifications as SiOx completely broke down. Neither thermal property was affected by pressure, as it was the processing temperature that induced tempering effects on the crystallization behaviour of polymeric components. Only PE/EVOH/PE, when in contact with water as a simulant, presented a decrease in the melting point temperature. Copyright © 2008 John Wiley & Sons, Ltd.
Validation of a mixed‐layer closure. II: Observational tests
Authors: Lilly Douglas K. 
Published: March 2008

AbstractData from the DYCOMS2 observational campaign are used to test a mixed‐layer entrainment model presented previously by the author. The model is extended to include the effects of drizzle precipitation and radiative warming from the surface. The most consistent results are obtained under the assumption that the mixed‐layer top is unsaturated, that is, the cloud top is below the top of the turbulent flow. With this assumption, the predicted entrainment rates lie near those obtained by Faloona et al., and are well correlated with them, but are sensitive to the evaluation of temperature and moisture jumps and other parameters. The predicted entrainment rates are substantially smaller than those observed by Gerber et al., and are not correlated with them.Drizzle precipitation, as evaluated by VanZanten et al., reduces entrainment rates due to evaporative cooling below cloud base. This effect appears to improve the comparisons with observations. Tests of the robustness of the model calculations show mostly encouraging results. The effect of surface radiation into cloud base is found to be almost negligible. A new criterion for cloud‐top entrainment instability, based on the entrainment closure, indicates stability for most observed conditions. The homogeneity of the DYCOMS2 data is beneficial for obtaining reliable measures of entrainment, but limits the ability to test closure predictions over a wide range of conditions.Use of this model for parametrization of marine stratiform cloud layers in large‐scale or climate prediction models is considered plausible with limitations. Copyright © 2008 Royal Meteorological Society
Validation of a mixed‐layer closure. I: theoretical tests
Authors: Lilly Douglas K. , Stevens Bjorn 
Published: March 2008

AbstractA flux closure formula introduced earlier for predicting entrainment into a mixed layer is tested through analytic solution of the kinetic energy equation and through large‐eddy simulation. For this purpose, the closure formulation and the simulation model are applied to the ‘smoke cloud’ mixed layer, that includes both radiative cooling at the cloud top and surface heating or cooling at the surface, but without the effects of latent heat. The unique aspect of the closure, height weighting of the integral of buoyancy flux, is found to be directly related to the ratio of coefficients of the dissipation and diffusion terms of the energy equation.The simulation results indicate that the previous expression for predicting the entrainment flux is about 10% too small. Results of analytic solutions of the energy equation and the simulations are in general agreement. Disagreements are believed to be due to approximations in the energy equation and possible imperfections in the simulation model.A special issue investigated is the condition for decoupling of energy by surface radiative cooling. The maximum negative buoyancy flux before decoupling predicted by the flux closure and by the energy equation differ by almost a factor of 2, but it is not clear which is better. Copyright © 2008 Royal Meteorological Society
A numerical study of three catastrophic precipitating events over southern France. I: Numerical framework and synoptic ingredients
Authors: Nuissier O. , Ducrocq V. , Ricard D. , Lebeaupin C. , Anquetin S. 
Published: March 2008

AbstractThis study examines the simulation of three torrential rain events observed on 13–14 October 1995 (the Cévennes case), 12–13 November 1999 (the Aude case) and 8–9 September 2002 (the Gard case) over the southeastern part of France using the Meso‐NH non‐hydrostatic mesoscale numerical model. These cases were associated with extreme Heavy Precipitation Events (HPEs) with significant precipitation amounts exceeding 500 mm in less than 24 hours. Several sets of numerical experiments were performed with 10 km and 2.5 km horizontal resolutions. In part I of this study, special attention is paid to the experimental design for obtaining realistic simulations of HPEs with the Meso‐NH model, as well as the evolution of the synoptic patterns in which the rainfall events are embedded.The best 2.5 km numerical simulations show the ability of the Meso‐NH model to reproduce significant quasi‐stationary rainfall events. Moreover, the model fairly reproduces the low‐level mesoscale environments associated with the three HPEs. The HPEs formed in a slow‐evolving synoptic environment favourable for the development of convective systems (diffluent upper‐level southerly flow, PV anomalies, etc.). At lower levels, a southerly to easterly moderate to intense flow provided conditionally unstable and moist air as it moved over the relatively warm Mediterranean Sea, typical for this time of the year (late summer and autumn). The two extreme cases (Gard and Aude) differ from the more classical event (Cévennes) in terms of larger low‐level moisture fluxes. Weaker values of conditional convective instability, as in the Aude case, is counterbalanced by a stronger warm and moist low‐level jet. The mesoscale triggering and/or sustaining ingredients for deep convection and the physical mechanisms leading to the stationarity of these rainfall events are presented and discussed in a companion paper. Copyright © 2008 Royal Meteorological Society
Aircraft type‐specific errors in AMDAR weather reports from commercial aircraft
Authors: Drüe C. , Frey W. , Hoff A. , Hauf Th. 
Published: March 2008

AbstractAMDAR (Aircraft Meteorological DAta Relay) automated weather reports from commercial aircraft provide an increasing amount of input data for numerical weather prediction models. Previous studies have investigated the quality of AMDAR data. Few of these studies, however, have revealed indications of systematic errors dependent upon the aircraft type. Since different airlines use different algorithms to generate AMDAR reports, it has remained unclear whether a dependency on the aircraft type is caused by physical properties of the aircraft or by different data processing algorithms. In the present study, a special AMDAR dataset was used to investigate the physical type‐dependent errors of AMDAR reports. This dataset consists of AMDAR measurements by Lufthansa aircraft performing over 300 landings overall at Frankfurt Rhein/Main (EDDF/FRA) on 22 days in 2004. All of this data has been processed by the same software, implying that influences from different processing algorithms should not be expected. From the comparison of single descents to hourly averaged vertical profiles, it is shown that temperature measurements by different aircraft types can have systematic differences of up to 1 K. In contrast, random temperature errors of most types are estimated to be less than 0.3 K. It is demonstrated that systematic deviations in AMDAR wind measurements can be regarded as an error vector, which is fixed to the aircraft reference system. The largest systematic deviations in wind measurements from different aircraft types (more than 0.5 m s−1) were found to exist in the longitudinal direction (i.e. parallel to the flight direction). Copyright © 2008 Royal Meteorological Society