bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conformational Restriction of the Calix[6]arene Macrocycle by the Ritter Reaction
Authors: Vatsouro Ivan M. , Shokova Elvira A. , Shestakova Alla K. , Chertkov Vyacheslav A. , Kovalev Vladimir V. 
Published: November 2005

AbstractHerein we report on the development of a novel and efficient approach to the restriction of the conformational mobility of calix[6]arenes. The method involves the addition of tertiary alcohols to calix[6]arenes with one, three and six cyanomethoxy groups attached to the lower rim under modified Ritter reaction conditions. Alkylation of monocyanomethoxy‐p‐tert‐butylcalix[6]arene (1) and 37,39,41‐trimethoxy‐38,40,42‐tricyanomethoxy‐p‐tert‐butylcalix[6]arene (2) with 3‐R‐1‐adamantanols (R = H, CH2COOH) in trifluoroacetic acid afforded the corresponding mono‐ and triamides with cone‐like conformations. The partial alkylation of hexanitrile derivatives showed unexpected regioselectivity. Addition of 1‐adamantanol or tert‐butyl alcohol to hexacyanomethoxy‐p‐X‐calix[6]arenes 3a–c (X = tert‐butyl, 1‐adamantyl, 3‐methoxycarbonylmethyl‐1‐adamantyl) gave 37,40‐dinitrile‐38,39,41,42‐tetraamides as the major products. These tetraamides are conformationally restricted in solution over a wide range of temperatures and adopt a flattened 1,2,3‐alternate conformation, as shown by 2D and variable‐temperature NMR experiments. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
3‐Substituted Cyclopenta[c]pyrans: Synthesis and Electrophilic Substitutions
Authors: Güllük Eduard , Bogdan Elena , Christl Manfred 
Published: November 2005

AbstractThe literature procedure for the preparation of the parent cyclopenta[c]pyran (1) was shown to provide only a low yield on mechanistic grounds. Intended as an alternative starting material for the synthesis of 1, the cyclopenta[c]pyran‐3‐ones 10 were prepared. However, their conversion into 1 could be achieved at best in 1 % yield. Derivatives of 1 with an oxygen functionality in the 3‐position were obtained by deprotonation, silylation and benzoylation of 10b, giving rise to the lithium enolate 15, the ketene acetals 16–18 and the ketene hemiacetal ester 19, respectively. The olefination of 10b with substituted methylenetriphenylphosphoranes furnished cyclopenta[c]pyran‐3‐ylacetonitrile (21) and methyl cyclopenta[c]pyran‐3‐ylacetate (22) in modest yields. These compounds as well as the primary alcohol 23, which resulted from 22 on reduction with LiAlH4, underwent an electrophilic aromatic substitution reaction with trifluoroacetic anhydride to form the 7‐(trifluoroacetyl)cyclopenta[c]pyrans 24–27. In the case of the acetonitrile 27, a second and a third trifluoroacetyl group were readily introduced, giving rise to the highly resonance‐stabilised anions 28 and 29, the latter exhibiting a strong green fluorescence. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Substituent Effects in Tandem Ring‐Closing Metathesis Reactions of Dienynes
Authors: Boyer François‐Didier , Hanna Issam 
Published: November 2005

AbstractSeveral dienynes bearing different substituents have been synthesized and subjected to a ring‐closing metathesis (RCM) reaction using ruthenium carbene complexes. Dienynes containing a pre‐existing ring and a quaternary center attached to the alkyne give the expected tandem metathesis products in high yields. For these substrates, a high selectivity for different ring sizes was achieved by modifying the reactivity of one alkene. In one case, an unusual non‐metathetic activity of the second‐generation Grubbs catalyst was observed and the cycloisomerization product was obtained as the major product. In the absence of favorable factors, especially when the starting substrates contain hindered alkenes, a long tether chain and/or an ester group on the alkyne part, the tandem process is slowed down or completely impeded. In these cases, dienynes behave like simple enynes and afford initial metathesis products whose further reactions give dimeric compounds.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Synthesis of Dendritic Branches with Peripheral Fullerene Subunits
Authors: Hahn Uwe , Hosomizu Kohei , Imahori Hiroshi , Nierengarten Jean‐François 
Published: November 2005

AbstractHighly soluble dendritic branches with two, four, eight or 16 methanofullerene subunits at their peripheries and carboxylic acid functions at their focal points have been prepared by a convergent approach. Starting from a methanofullerene derivative possessing a tert‐butyl ester function, the successive dendrimer generations were obtained by repetition of a reaction sequence involving cleavage of the tert‐butyl ester moiety under acidic conditions, followed by a DCC‐mediated esterification reaction with an A2B building block possessing two benzylic alcohol functions and a tert‐butyl ester group. This repetitive synthetic sequence is very efficient and allowed the dendritic growth up to the fifth‐generation derivative, containing 16 peripheral fullerene subunits. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
SN2′ Reactions between Lithiated Carbon Nucleophiles and Silylated Vinyloxiranes – Effects of Salts and Solvents on the Stereocontrol
Authors: Marié Jean‐Charles , Courillon Christine , Malacria Max 
Published: November 2005

Abstract(α,β‐Epoxy‐γ,δ‐alkenyl)‐tert‐butyldimethylsilanes 1 display, a priori, three electrophilic centres and two acidic protons. Depending on the configurations of their oxirane rings, the title compounds react towards lithiated bases either through metallation or SN2′ reactions. In this paper we demonstrate that the trans‐2‐(tert‐butyldimethylsilyl)‐3‐vinyloxiran 1a reacts regioselectively with primary, secondary and tertiary butyllithium in SN2′ fashion, which allows the formation of α‐silylated allylic alcohols with diastereomeric ratios of over 7 to 1 in favour of the Z olefins. A study of the effect of temperature, time, addition of salt and polarity of the solvent on the diastereoselectivity of the reaction is described and the results are interpreted in terms of different mechanistic models. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Cover Picture: Synthesis and Structures of Fullerene Bromides and Chlorides (Eur. J. Org. Chem. 23/2005)
Authors: Troyanov Sergey I. , Kemnitz Erhard 
Published: November 2005

AbstractThe cover picture shows a variety of fullerene bromides and chlorides synthesized and structurally investigated in the last few years. A rich “harvest” of fullerene chlorides of C60 and C70 has been “collected” by using inorganic chlorides and oxychlorides for the chlorination of fullerenes. Even a fullerene chloride with a drum‐shaped carbon cage, D3‐C60Cl30, could be obtained. The maximum degree of chlorination of both C60 (left) and C70 (right) is much higher than that of bromination. More about the synthesis and molecular structures of fullerene bromides and chlorides can be found in the Microreview by S. I. Troyanov and E. Kemnitz on p. 4951 ff.
Membrane‐based bimetallic nanoparticles for environmental remediation: Synthesis and reactive properties
Authors: Xu Jian , Bhattacharyya Dibakar 
Published: November 2005

AbstractNanoscale bimetallic particles have important applications in the environmentally important catalytic reactions at room temperature because of the novel physical and chemical properties. We report an innovative in situ synthesis method of functionalizing microfiltration membranes with highly reactive bimetallic core/shell Fe/Ni and Fe/Pd nanoparticles. The core/shell structure was confirmed by X‐ray energy dispersive spectroscopy mapping images. Using TCE and PCB as model compounds, the reactivity of membrane‐immobilized bimetallic nanoparticles was quantified in terms of both reaction mechanism shift and product distribution. Complete dechlorination was achieved with both compounds. © 2005 American Institute of Chemical Engineers Environ Prog, 2005
Potential and drawbacks of microbiology–membrane interaction in membrane bioreactors
Authors: Drews Anja , Evenblij Herman , Rosenberger Sandra 
Published: November 2005

AbstractIn membrane bioreactors (MBRs), biomass and membranes interact in a number of ways, making it difficult to extrapolate phenomena and models known from conventional activated sludge processes. Originally, MBRs were thought to enable immense process intensifications through very high MLSS (mixed liquor suspended solid) concentrations and resulting low footprint. Economic considerations, however, currently lead to lower concentrations because high biomass content impedes oxygen transfer and increases sludge viscosity. On the other hand, the interactions can lead to a number of new potentials, which as yet were unknown in each unit operation individually such as increased removal efficiencies through a change in the microbial community or sludge age. Here, both potentials and limits of biomass–membrane interactions are reviewed with a focus on recent results from Europe, especially from Germany. © 2005 American Institute of Chemical Engineers Environ Prog, 2005
Seismic behaviour of cracked concrete gravity dams
Authors: Pekau O. A. , Zhu Xueye 
Published: November 2005

AbstractA finite element model of incremental displacement constraint equations (IDCE), based on an existing node‐to‐surface concept, is implemented to deal with dynamic contact surfaces in the seismic behaviour analysis of cracked concrete gravity dams. After verification for sliding, rocking and impact, the IDCE model is applied to study the seismic responses of concrete gravity dams with different profiles and crack locations for a variety of parameters, such as coefficient of friction, water level and type of earthquake, as well as impact damping based on the concept of coefficient of restitution. It is revealed that cracked concrete gravity dams can experience not only sliding and rocking modes, but also the drifting mode in some cases of crack either at the base or at a height. Downstream sliding is normally accompanied by rocking, especially for the cases of crack at a height. Due to rocking and drifting, a cracked dam may still acquire a certain amount of residual sliding even if the effective coefficient of friction is relatively high. Copyright © 2005 John Wiley & Sons, Ltd.
Simplified methods for design of base‐isolated structures in the long‐period high‐damping range
Authors: Weitzmann Ruediger , Ohsaki Makoto , Nakashima Masayoshi 
Published: November 2005

AbstractA recent trend in the design of base‐isolated structures is the extension of the natural period and the incorporation of high damping. This paper shows that the existing simplified methods perform less accurately in this field of application, mainly due to inappropriate use of spectral data and insufficiently adjusted equivalent models. The paper proposes new period‐dependent concepts to reduce pseudo‐acceleration spectra and to transform these values into total accelerations with respect to the viscous damping ratio. The model of equivalent damping is adjusted to reflect several period‐dependent effects. The estimation of the accelerations in MDOF systems is based on additional period shifts. All modifications are derived for a simplified linear approach based on eigenforms, and a non‐linear approach based on pushover and capacity spectrum analysis. To illustrate observed problems and to demonstrate the capabilities of the proposed concepts, example structures are studied in detail. Furthermore, intensive statistical tests prove the effectiveness of the modifications in a wide parameter range and show considerable improvements over traditional approaches. Copyright © 2005 John Wiley & Sons, Ltd.
Aeolian deposition of dust over hills: the effect of dust grain size on the deposition pattern
Authors: Goossens Dirk 
Published: November 2005

AbstractWind tunnel experiments were conducted to investigate the effects of topography on the grain size characteristics of aeolian dust deposits. Experiments were performed on three isolated hills having various size and aspect ratios. The longitudinal profile of the median grain diameter was investigated for each hill. The longitudinal dust deposition profile was also studied for nine grain size classes of between 10 and 104 µm, as were wind and dust concentration profiles in the atmosphere upwind of, over and downwind of a hill. The wind tunnel experiments show that the grain size characteristics of aeolian dust deposits are affected by topography. Most apparent is the occurrence of a zone of reduced grain size on the leeside of hills, which extends from just upwind of the summit to a distance of several times the height of the hill. Slightly coarser than normal dust is deposited on the concave windward hill slope and in a zone downwind of the area of reduced grain size, but the increase in grain size in these zones remains very small. Although the normalized dust deposition profile for a hill does not vary substantially as a function of grain size, systematic trends are observed. The most important tendencies are: (1) a progressive extension, in the downwind direction, of a zone of decreased dust deposition on the leeside of a hill (the coarser the grains, the further downwind the zone of reduced deposition extends); (2) a progressive increase in dust deposition immediately upwind of a hill (the finer the grains, the higher the deposition value upwind of a hill becomes). Both tendencies are explained by the difference in inertia of the grains, which is controlled by grain size. Copyright © 2005 John Wiley & Sons, Ltd.
Structural patterns in river network organization at both infra‐ and supra‐basin levels: the case of a granitic relief
Authors: Cudennec Christophe , Fouad Youssef 
Published: November 2005

AbstractWithin a landform, the channelized water path from any point to the corresponding outlet is split into successive components within the Strahler ordering scheme. The probability density functions (pdf) of the length L of the whole channelized path and of the lengths of the components are studied as multi‐level structural functions. We have considered a granitic area and studied both its main basin and the set of its 48 constituent basins. With respect to the main basin, the pdf of the component lengths exhibit a strong scaling property, except for the highest orders, due to a hierarchical constraint; hence, the pdf of sum L has no particular shape. We have nevertheless identified an underlying structural pattern at particular infra‐ and supra‐basin levels, where the hierarchical constraint is weaker. This identification process entails noting structurally emerging patterns based on multi‐level variables and distributions, which satisfy the general self‐similarity of networks. The fairly good fit of an analytical gamma law with most of these emerging patterns can prove to be a positive step towards both a general modelling approach to the geomorphometric functions and a stronger geomorphological basement of hydrological transfer functions. Copyright © 2005 John Wiley & Sons, Ltd.
Characteristics and dynamics of multiple intertidal bars, north Lincolnshire, England
Authors: van Houwelingen Selma , Masselink Gerhard , Bullard Joanna 
Published: November 2005

AbstractMultiple intertidal bars and troughs, often referred to as ‘ridges and runnels’, are significant features on many macrotidal sandy beaches. Along the coastline of England and Wales, they are particularly prevalent in the vicinity of estuaries, where the nearshore gradient is gentle and a large surplus of sediment is generally present. This paper examines the dynamics of such bar systems along the north Lincolnshire coast.A digital elevation model of the intertidal morphology obtained using LIDAR demonstrates that three to five intertidal bars are consistently present with a spacing of approximately 100 m. The largest and most pronounced bars (height = 0·5–0·8 m) are found around mean sea level, whereas the least developed bars (height = 0·2–0·5 m) occur in the lower intertidal zone. Annual aerial photographs of the intertidal bar morphology were inspected to try to track individual bars from year to year to derive bar migration rates; however, there is little resemblance between concurrent photographs, and ‘resetting’ of the intertidal profile occurs on an annual basis. Three‐dimensional beach surveys were conducted monthly at three locations along the north Lincolnshire coast over a one‐year period. The intertidal bar morphology responds strongly to the seasonal variation in the forcing conditions, and bars are least numerous and flattest during the more energetic winter months. Morphological changes over the monthly time scale are strongly affected by longshore sediment transport processes and the intertidal bar morphology can migrate along the beach at rates of up to 30 m per month.The behaviour of intertidal bars is complex and varies over a range of spatial and temporal scales in response to a combination of forcing factors (e.g. incident wave energy, different types of wave processes, longshore and cross‐shore sediment transport), relaxation time and morphodynamic feedback. Copyright © 2005 John Wiley & Sons, Ltd.
Quantitative V&V of CFD simulations and certification of CFD codes
Authors: Stern Fred , Wilson Robert , Shao Jun 
Published: November 2005

AbstractDefinitions and equations are provided for the quantitative assessment of numerical (verification) and modelling (validation) errors and uncertainties for CFD simulations and of intervals of certification for CFD codes. Verification, validation, and certification methodology and procedures are described. Examples of application of quantitative certification of RANS codes are presented for ship hydrodynamics. Opportunities and challenges for achieving consensus and standard V&V and certification methodology and procedures are discussed. Copyright © 2005 John Wiley & Sons, Ltd.
Numerical simulation of incompressible viscous flow past a heaving airfoil
Authors: Sarkar Sunetra , Venkatraman Kartik 
Published: November 2005

AbstractNumerical simulations of a heaving airfoil undergoing non‐sinusoidal motions in an incompressible viscous flow is presented. In particular, asymmetric sinusoidal motions, constant heave rate oscillations, and sinusoidal motions with a quiescent gap, are considered. The wake patterns, thrust force coefficients, and propulsive efficiency at various values of non‐dimensional heave velocity are computed. These have been compared with those of corresponding sinusoidal heaving motions of the airfoil. It is shown that for a given non‐dimensional heave velocity and reduced frequency of oscillation, asymmetric sinusoidal motions give better thrust and propulsive efficiencies in comparison to pure harmonic motion. On the other hand, constant rate heave motion do not compare favourably with harmonic motion. A train of sinusoidal pulses separated by a quiescent gap compares favourably with a pure sinusoidal motion, but with the notable exception that the quiescent gap induces a discontinuity that induces large impulses to the wake pattern. Copyright © 2005 John Wiley & Sons, Ltd.
Comparisons of CIP, compact and CIP‐CSL2 schemes for reproducing internal solitary waves
Authors: Nakayama K. 
Published: November 2005

AbstractSix different models were evaluated for reproducing internal solitary waves which occur and propagate in a stratified flow field with a sharp interface. Three stages were used to compute internal solitary waves in a stratified field: (1) first‐phase computation of momentum equations, (2) second‐phase computation of momentum equations, which corresponds to computing the Poisson's equation, and (3) density computation. The six models discussed in this paper consisted of combinations of four different schemes, a three‐point combined compact difference scheme (CCD), a normal central difference scheme (CDS), a cubic‐polynomial interpolation (CIP), and an exactly conservative semi‐Lagrangian scheme (CIP‐CSL2). The residual cutting method was used to solve the Poisson's equation. Three tests were used to confirm the validity of the computations using KdV theory; i.e. the incremental wave speed and amplitude of internal solitary waves, the maximum horizontal velocity and amplitude, and the wave form. In terms of the shape of an internal solitary wave, using CIP for momentum equations was found to provide better performance than CCD. These results suggest one of the most appropriate scheme for reproducing internal solitary waves may be one in which CIP is used for momentum equations and CCD to solve the Poisson's equation. Copyright © 2005 John Wiley & Sons, Ltd.
Droplets on patterned substrates: water off a beetle's back
Authors: Dupuis A. , Yeomans J. M. 
Published: November 2005

AbstractWe present a lattice Boltzmann model to describe the spreading of droplets on chemically and topologically patterned substrates. As an example, we consider the process by which a Namibian beetle captures water on its back which is hydrophobic but covered by peaks with hydrophilic tops. Copyright © 2005 John Wiley & Sons, Ltd.
Pyrometamorphism of 19th‐century kiln artifacts from Caledonia Springs, Ontario, Canada
Authors: Owen J. Victor , Culhane Phil 
Published: November 2005

AbstractMarked, 19th‐century kiln bricks and rocks from Caledonia Springs (CS) have black glass coatings that can easily be mistaken for glass produced at the elusive CS glassworks (c. 1844–1846). The glass‐on‐brick material, however, is more aluminous (nearly 20% Al2O3) than virtually any analyzed historical glass, and the glass‐on‐rock is compositionally similar to the rock itself, which shows clear signs of having undergone extensive melting. Mineral thermometry (Cpx‐Ol, Pl‐melt) indicates that parts of the kiln‐achieved temperatures of approximately 1200–1300°C. The CS samples show that caution must be exercised when identifying seemingly obvious waste glass near defunct glassworks sites. © 2005 Wiley Periodicals, Inc.