bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of High Pressure on the Heck Reaction − A Contribution to a Deeper Understanding of the Mechanism
Authors: Buback Michael , Perković Thomas , Redlich Stefan , Meijere Armin de 
Published: June 2003

AbstractThe influence of high pressure on the Heck reactions of iodobenzene with methyl, ethyl and tert‐butyl acrylate, and of both 4‐nitrophenyl iodide and 4‐nitrophenyl triflate with methyl acrylate, has been studied for the first time by quantitative on‐line FT‐IR spectroscopy. Reaction rates and activation parameters (ΔH‡, ΔS‡, ΔV‡) were determined at temperatures between 50 and 120 °C and pressures up to 3000 bar. A clear influence on the kinetics of the reactions was observed by the nature of the leaving group and by the steric and electronic features of the acrylate. tert‐Butyl acrylate, which is more electron‐rich than methyl acrylate according to PES measurements, was found to react 1.4‐times faster on average than methyl acrylate and, at elevated pressures, triflate turned out to be a better leaving group than iodide. Thus, the observed activation volume for the reaction of iodobenzene with tert‐butyl acrylate (ΔV‡ = −12 cm3 mol−1) is more negative than that of the reaction of iodobenzene with ethyl acrylate (ΔV‡ = −7 cm3 mol−1) or methyl acrylate (ΔV‡ = −5 cm3 mol−1). For the variation of the leaving group in 4‐nitrophenyl iodide and 4‐nitrophenyl triflate, the activation volumes for the reaction of each with methyl acrylate are −9 and −37 cm3 mol−1, respectively. The results suggest that the rate‐determining step of the overall reaction is not the oxidative addition, but is either the alkene coordination or the subsequent carbopalladation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis of a Cellobiosylated Dimer and Trimer and of Cellobiose‐Coated Polyamidoamine (PAMAM) Dendrimers to Study Accessibility of an Enzyme, Cellodextrin Phosphorylase
Authors: Choudhury Ambar K. , Kitaoka Mitomitsu , Hayashi Kiyoshi 
Published: June 2003

AbstractTo examine the accessibility of the enzyme cellodextrin phosphorylase (CDP) towards multivalent cluster carbohydrates, the cellobiosylated dimer 10 and trimer 12, as well as the cellobiose‐coated PAMAM dendrimers 14, 16, 18, 20 and 22, with four, eight, sixteen, thirty‐two and sixty‐four cellobiose units at the outer surface of PAMAM dendrimers, respectively, have been synthesized for the first time and used as acceptor substrates for the enzyme CDP. It was found that CDP was able to transfer a glucosyl moiety from glucose‐1‐phosphate (Glc‐1‐P) into these synthesized cluster cellobiosylated glycoconjugates and cellobiose‐coated PAMAM dendrimers, which were thus acceptor substrates for CDP. It was found that the ability of CDP to interact with smaller cellobiosylated glyconjugates and with PAMAM dendrimers containing up to eight cellobiose units was similar to that seen with cellobiose. However, this capability of CDP was somewhat lessened with the PAMAM dendrimer containing sixteen cellobiose moieties and dramatically decreased towards PAMAM dendrimers with thirty‐two and sixty‐four cellobiose units. This might be due to their steric bulk, CDP enzyme no longer being able to hold them properly on its active site. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Successive Cycloadditions between 4‐Fluoro‐5‐trifluoromethyl‐1,2‐dithiole‐3‐thione and Dimethyl Acetylenedicarboxylate: New Fluorinated Thiaheterocycles through New Reaction Mechanisms
Authors: Timoshenko Vadim M. , Bouillon Jean‐Philippe , Chernega Alexander N. , Shermolovich Yuriy G. , Portella Charles 
Published: June 2003

AbstractThe cycloaddition reaction between dimethyl 2‐(1‐fluoro‐2‐trifluoromethyl‐2‐thioxoethylidene)‐1,3‐dithiole‐4,5‐dicarboxylate and dimethyl acetylenedicarboxylate proceeds efficiently under irradiation conditions in air. A study of the reaction conditions resulted in the proposal of a chain mechanism initiated by a photochemically induced single‐electron transfer to oxygen. On the other hand, the cycloadduct can be transformed into a rearranged hydroxylated product by filtration through silica gel. Either the cycloadduct or its rearranged product can be obtained selectively in a one‐pot process from the parent 1,2‐dithiole‐3‐thione. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
The Reactivity of (Z)‐5‐Acetyl‐3‐aryl‐2,3‐dihydro‐2‐[(thioacyl)methylene]1,3,4‐thiadiazoles: A Surprising Base‐Induced Conversion into 3‐(N‐arylamino)thiophenes
Authors: Benincori Tiziana , Pilati Tullio , Rizzo Simona , Sada Mara , Sannicolò Franco 
Published: June 2003

AbstractWe report the reactivity shown by two classes of rarely investigated heterocycles, the 5‐acetyl‐2,3‐dihydro‐3‐phenyl‐2‐(phenylmethylene)‐1,3,4‐thiadiazoles (6) and the 5alkanoyl‐3‐aryl‐2,3‐dihydro‐2‐[(thioacyl)methylene]‐1,3,4thiadiazoles 1a−e. In both cases, strong bases promote cleavage of the thiadiazole ring with loss of thiocyanate anion, generating N‐arylketeneimines and N‐aryl(thioacyl)keteneimines 5, respectively. These very reactive species undergo either nucleophilic addition or [4+2] cycloaddition reactions involving the thioacyl function. The most surprising result was found in the reactions of the 5‐acetyl‐3‐aryl‐2,3‐dihydro‐2‐[(thioacyl)methylene]‐1,3,4‐thiadiazoles 1a,d,e, which afford 3‐(arylamino)thiophenes 2, 10, and 14 as the main products. This serendipitous transformation, which seems to be rather general, probably involves an intermediate step in which the acetyl group of the substrates is converted into ketene. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Flash Vacuum Thermolysis of 1‐Azabicyclo[1.1.0]butanes. Photoelectron Spectrum of 3‐Phenyl‐2‐azabuta‐1,3‐diene
Authors: Bartnik Romuald , Baylère Patrick , Chrostowska Anna , Galindo Alberto , Leśniak Stanislaw , Pfister‐Guillouzo Geneviève 
Published: June 2003

AbstractThe reaction behaviour of 1‐azabicyclo[1.1.0]butanes under flash vacuum thermolysis (FVT) conditions was studied. It has been found that the thermal rearrangement of title compounds produces unstable 2‐aza‐1,3‐dienes. The formation of these products was established by reduction, by Diels−Alder reactions and by UV photoelectron spectroscopy. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Enantioselective Synthesis of the Ester Side Chain of Homoharringtonine
Authors: Keller Laurent , Dumas Françoise , d’Angelo Jean 
Published: June 2003

AbstractDetails of the synthesis of the methyl ester of the side chain of homoharringtonine, a natural product with antileukemic properties, are reported below. The key tactical element involved a Michael addition between the known chiral imine 4 and 2‐acetoxyacrylonitrile (5), furnishing the adduct (2R,1′R)‐6 with a high degree of regio‐ and stereoselectivity. This adduct was then converted into the target compound (R)‐2 by a linear sequence of ten chemical operations, in 6.0% overall yield. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis and Reactivity of a New Heptacarbon Chain Carboxonium Salt − Access to a New Class of Streptocyanine Dyes
Authors: Izquierdo Albert , Payrastre Corinne , Gornitzka Heinz , Madaule Yves 
Published: June 2003

AbstractA new highly reactive heptacarbon chain carboxonium salt 1 was synthesized. It leads, by action of various amines and hydrazone, to a new class of symmetrical heptacarbon chain streptocyanine dyes 2−6. A hemicarboxonium salt 7, which leads to a dissymmetrical streptocyanine, was also obtained. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A life‐cycle assessment (LCA) model for cables based on the fire‐LCA model
Authors: Simonson Margaret , Andersson Petra , Emanuelsson Viktor , Stripple Håkan 
Published: June 2003

AbstractA novel life‐cycle assessment (LCA) model has been developed for the investigation of the environmental impact of the choice of material in cable production. In the first application polyolefin based material and PVC material is used. In both cases equivalent fire behaviour is assumed and a fire model is established based on existing fire statistics. This study represents the second full application of the fire‐LCA model.In this paper the new ‘cables fire‐LCA’ model will be presented together with the results of this first application. Aspects such as end‐of‐life scenarios, fire statistics, and fire scenarios and large scale fire performance of cables are discussed together with details of the straw LCA model defined for cables and the results of four different end‐of‐life scenarios. Copyright © 2003 John Wiley & Sons, Ltd.
Charring rates and temperature profiles of wood sections
Authors: Frangi Andrea , Fontana Mario 
Published: June 2003

AbstractA research project was carried out at the Swiss Federal Institute of Technology (ETH) to study the fire behaviour of hollow core timber slabs and timber‐concrete composite slabs. This paper describes the main results of the basic fire behaviour of timber measured in the study. The first part of the analysis looks at the charring rate of timber. In the second part a new calculation model for the temperature development in wood members exposed to the standard ISO‐fire is presented and compared with the fire test results. Copyright © 2003 John Wiley & Sons, Ltd.
Numerical simulation of three‐dimensional free surface flows
Authors: Maronnier V. , Picasso M. , Rappaz J. 
Published: June 2003

AbstractA numerical model is presented for the simulation of complex fluid flows with free surfaces in three space dimensions. The model described in Maronnier et al. (J. Comput. Phys. 1999; 155(2) : 439) is extended to three dimensional situations. The mathematical formulation of the model is similar to that of the volume of fluid (VOF) method, but the numerical procedures are different.A splitting method is used for the time discretization. At each time step, two advection problems—one for the predicted velocity field and the other for the volume fraction of liquid—are to be solved. Then, a generalized Stokes problem is solved and the velocity field is corrected. Two different grids are used for the space discretization. The two advection problems are solved on a fixed, structured grid made out of small cubic cells, using a forward characteristic method. The generalized Stokes problem is solved using continuous, piecewise linear stabilized finite elements on a fixed, unstructured mesh of tetrahedrons.The three‐dimensional implementation is discussed. Efficient postprocessing algorithms enhance the quality of the numerical solution. A hierarchical data structure reduces memory requirements. Numerical results are presented for complex geometries arising in mold filling. Copyright © 2003 John Wiley & Sons, Ltd.
A non‐linear k–ε model with realizability for prediction of flows around bluff bodies
Authors: Kimura Ichiro , Hosoda Takashi 
Published: June 2003

AbstractThe incompressible flow around bluff bodies (a square cylinder and a cube) is investigated numerically using turbulence models. A non‐linear k–ε model, which can take into account the anisotropy of turbulence with less CPU time and computer memory then RSM or LES, is adopted as a turbulence model. In tuning of the model coefficients of the non‐linear terms are adjusted through the examination of previous experimental studies in simple shear flows. For the tuning of the coefficient in the eddy viscosity (=Cμ), the realizability constraints are derived in three types of basic 2D flow patterns, namely, a simple shear flow, flow around a saddle and a focal point. Cμ is then determined as a function of the strain and rotation parameters to satisfy the realizability. The turbulence model is first applied to a 2D flow around a square cylinder and the model performance for unsteady flows is examined focussing on the period and the amplitude of the flow oscillation induced by Karman vortex shedding. The applicability of the model to 3D flows is examined through the computation of the flow around a surface‐mounted cubic obstacle. The numerical results show that the present model performs satisfactorily to reproduce complex turbulent flows around bluff bodies. Copyright © 2003 John Wiley & Sons, Ltd.
Numerical simulation of turbulent flow through series stenoses
Authors: Lee T. S. , Liao Wei , Low H. T. 
Published: June 2003

AbstractThe flow fields in the neighbourhoods of series vascular stenoses are studied numerically for the Reynolds numbers from 100 to 4000, diameter constriction ratios of 0.2–0.6 and spacing ratios of 1, 2, 3, 4 and ∞. In this study, it has been further verified that in the laminar flow region, the numerical predictions by k–ω turbulence model matched those by the laminar‐flow modelling very well. This suggests that the k–ω turbulence model is capable of the prediction of the laminar flow as well as the prediction of the turbulent stenotic flow with good accuracy. The extent of the spreading of the recirculation region from the first stenosis and its effects on the flow field downstream of the second stenosis depend on the stenosis spacing ratio, constriction ratio and the Reynolds number. For c1 = 0.5 with c2 ≤ c1, the peak value of wall vorticity generated by the second stenosis is always less than that generated by the first stenosis. However, the maximum centreline velocity and turbulence intensity at the second stenosis are higher than those at the first stenosis. In contrast, for c1 = 0.5 with c2 = 0.6, the maximum values at the second stenosis are much higher than those at the first stenosis whether for centreline velocity and turbulence intensity or for wall vorticity. The peak values of the wall vorticity and the centreline disturbance intensity both grow up with the Reynolds number increasing. The present study shows that the more stenoses can result in a lower critical Reynolds number that means an earlier occurrence of turbulence for the stenotic flows. Copyright © 2003 John Wiley & Sons, Ltd.
Dispersion and stability analyses of the linearized two‐dimensional shallow water equations in boundary‐fitted co‐ordinates
Authors: Sankaranarayanan S. , Spaulding Malcolm L. 
Published: June 2003

AbstractIn the present investigation, a Fourier analysis is used to study the phase and group speeds of a linearized, two‐dimensional shallow water equations, in a non‐orthogonal boundary‐fitted co‐ordinate system. The phase and group speeds for the spatially discretized equations, using the second‐order scheme in an Arakawa C grid, are calculated for grids with varying degrees of non‐orthogonality and compared with those obtained from the continuous case. The spatially discrete system is seen to be slightly dispersive, with the degree of dispersivity increasing with an decrease in the grid non‐orthogonality angle or decrease in grid resolution and this is in agreement with the conclusions reached by Sankaranarayanan and Spaulding (J. Comput. Phys., 2003; 184: 299–320). The stability condition for the non‐orthogonal case is satisfied even when the grid non‐orthogonality angle, is as low as 30° for the Crank Nicolson and three‐time level schemes. A two‐dimensional wave deformation analysis, based on complex propagation factor developed by Leendertse (Report RM‐5294‐PR, The Rand Corp., Santa Monica, CA, 1967), is used to estimate the amplitude and phase errors of the two‐time level Crank–Nicolson scheme. There is no dissipation in the amplitude of the solution. However, the phase error is found to increase, as the grid angle decreases for a constant Courant number, and increases as Courant number increases. Copyright © 2003 John Wiley & Sons, Ltd.
A new VOF‐based numerical scheme for the simulation of fluid flow with free surface. Part II: application to the cavity filling and sloshing problems
Authors: Soo Kim Min , Sun Park Jong , Lee Woo Il 
Published: June 2003

AbstractFinite element analysis of fluid flow with moving free surface has been performed in 2‐D and 3‐D. The new VOF‐based numerical algorithm that has been proposed by the present authors (Int. J. Numer. Meth. Fluids, submitted) was applied to several 2‐D and 3‐D free surface flow problems. The proposed free surface tracking scheme is based on two numerical tools; the orientation vector to represent the free surface orientation in each cell and the baby‐cell to determine the fluid volume flux at each cell boundary. The proposed numerical algorithm has been applied to 2‐D and 3‐D cavity filling and sloshing problems in order to demonstrate the versatility and effectiveness of the scheme. The proposed numerical algorithm resolved successfully the free surfaces interacting with each other. The simulated results demonstrated applicability of the proposed numerical algorithm to the practical problems of large free surface motion. It has been also demonstrated that the proposed free surface tracking scheme can be easily implemented in any irregular non‐uniform grid systems and can be extended to 3‐D free surface flow problems without additional efforts. Copyright © 2003 John Wiley & Sons, Ltd.
Numerical simulation of unsteady multidimensional free surface motions by level set method
Authors: Yue Wusi , Lin Ching‐Long , Patel Virendra C. 
Published: June 2003

AbstractThis paper presents a numerical method that couples the incompressible Navier–Stokes equations with the level set method in a curvilinear co‐ordinate system for study of free surface flows. The finite volume method is used to discretize the governing equations on a non‐staggered grid with a four‐step fractional step method. The free surface flow problem is converted into a two‐phase flow system on a fixed grid in which the free surface is implicitly captured by the zero level set. We compare different numerical schemes for advection of the level set function in a generalized curvilinear format, including the third order quadratic upwind interpolation for convective kinematics (QUICK) scheme, and the second and third order essentially non‐oscillatory (ENO) schemes. The level set equations of evolution and reinitialization are validated with benchmark cases, e.g. a stationary circle, a rotating slotted disk and stretching of a circular fluid element. The coupled system is then applied to a travelling solitary wave, and two‐ and three‐dimensional dam breaking problems. Some interesting free surface phenomena are revealed by the computational results, such as, the large free surface vortices, air entrapment and splashing of the water surge front. The computational results are in excellent agreement with theoretical predictions and experimental data, where they are available. Copyright © 2003 John Wiley & Sons, Ltd.
Fourth‐order finite difference scheme for the incompressible Navier–Stokes equations in a disk
Authors: Lai Ming‐Chih 
Published: June 2003

AbstractWe develop an efficient fourth‐order finite difference method for solving the incompressible Navier–Stokes equations in the vorticity‐stream function formulation on a disk. We use the fourth‐order Runge–Kutta method for the time integration and treat both the convection and diffusion terms explicitly. Using a uniform grid with shifting a half mesh away from the origin, we avoid placing the grid point directly at the origin; thus, no pole approximation is needed. Besides, on such grid, a fourth‐order fast direct method is used to solve the Poisson equation of the stream function. By Fourier filtering the vorticity in the azimuthal direction at each time stage, we are able to increase the time step to a reasonable size. The numerical results of the accuracy test and the simulation of a vortex dipole colliding with circular wall are presented. Copyright © 2003 John Wiley & Sons, Ltd.
Responsibility for safety and risk minimization: Outline of an attribution‐based approach regarding modern technological and societal systems
Authors: Lenk Hans 
Published: June 2003

AbstractAfter the terrorist attacks of September 11, 2001, questions of safety management and responsibility became topical to a high degree. The notion of individual responsibility is, also for institutional and corporate decisions and enterprises, of particular importance for technology. Problems of collective and corporate responsibility are becoming and still will become even more topical. Engineering ethics codes should be developed, improved, and operationally implemented. Rules of priority outlined here for handling responsibility conflicts must be elaborated much further. This seems necessary to meet the ideal requirements of social responsibility for technology in society. © 2003 Wiley Periodicals, Inc. Hum Factors Man 13: 203–222, 2003.
Does safety science fulfill the requirements of modern technical systems?
Authors: Kuhlmann Albert 
Published: June 2003

AbstractSince the idea of safety science was first conceived, technical systems have grown larger and increasingly complex, thus causing a pronounced impact on the complexity of required safety analyses and risk calculations. The author emphasizes his point of view that the physical risk definition provides the most appropriate concept for engineers when it comes to planning including risk cadastres. In order to avoid human errors, he pleads for the consideration of human factors in the early design phase and for interdisciplinary cooperation. © 2003 Wiley Periodicals, Inc. Hum Factors Man 13: 223–230, 2003.
The acceptance of systemic thinking in various fields of technology and consequences on the respective safety philosophies
Authors: Geysen Willy , Verbruggen Johan 
Published: June 2003

AbstractSystemic thinking aims to develop a common language that makes it possible for scientists of different disciplines and technologies to communicate with one another. The specific methodology of systemic thinking is a means of tackling complex, interrelated problems by applying a holistic approach that focuses on the interrelation of individual aspects. In this article, an attempt is made to show the impact of systemic thinking in different areas of science and technology. In particular, the authors argue that a multidisciplinary, systemic approach can play an important role in developing a general theory of safety science. © 2003 Wiley Periodicals, Inc. Hum Factors Man 13: 231–242, 2003.
Technical responsibility management— an indispensable element of corporate governance
Authors: Althoff Jürgen 
Published: June 2003

AbstractWe define technical responsibility management as the organized fulfillment of all the legal and other responsibilities connected with the use of technical means of production and installations in an enterprise. To act legally responsible even under the condition of permanently changing regulations and to produce cost efficiency at the same time, a responsibility management system (RMS) is being presented, a system that, as it were, automatizes and rationalizes the fulfillment of all liabilities valid at the time. All existing installations in the enterprise, as well as all relevant legal provisions, are represented in adequate form by experts and, resulting from this, software determines optimized schedules that also take into account additional secondary operational conditions. Internet/intranet technology even permits complete outsourcing. RMSs heighten the safety level in the enterprise, provide legal security, and open up hitherto inaccessible savings potentials. The author pleads for the OECD principles for good “Corporate Governance Systems (Management and Controlling)” to demand the future introduction of RMSs. © 2003 Wiley Periodicals, Inc. Hum Factors Man 13: 253–259, 2003.