bluuebunny/crossref_metadata_2025 huggingface dataset:
Controls on englacial sediment deposition during the November 1996 jökulhlaup, Skeiđarárjökull, Iceland
Authors: Roberts Matthew J. , Russell Andrew J. , Tweed Fiona S. , Knudsen Óskar
Published: January 2005

This paper presents sedimentary evidence for rapid englacial debris entrainment during jökulhlaups. Previous studies of jökulhlaup sedimentology have focused predominantly on proglacial impact, rather than depositional processes within glaciers. However, observations of supraglacial floodwater outbursts suggest that englacial sediment emplacement is possible during jökulhlaups. The November 1996 jökulhlaup from Skeiđarárjökull, Iceland presented one of the first opportunities to examine englacial flood deposits in relation to former supraglacial outlets. Using observations from Skeiđarárjökull, this paper identifies and explains controls on the deposition of englacial flood sediments and presents a qualitative model for englacial jökulhlaup deposition. Englacial jökulhlaup deposits were contained within complex networks of upglacier‐dipping fractures. Simultaneous englacial deposition of fines and boulder‐sized sediment demonstrates that englacial fracture discharge had a high transport capacity. Fracture geometry was an important control on the architecture of englacial jökulhlaup deposits. The occurrence of pervasively frozen flood deposits within Skeiđarárjökull is attributed to freeze‐on by glaciohydraulic supercooling. Floodwater, flowing subglacially or through upglacier‐dipping fractures, would have supercooled as it was raised to the surface faster than its pressure‐melting point could increase as glaciostatic pressure decreased. Evidence for floodwater contact with the glacier bed is supported by the ubiquitous occurrence of sheared diamict rip‐ups and intra‐clasts of basal ice within jökulhlaup fractures, deposited englacially some 200–350 m above the bed of Skeiđarárjökull. Evidence for fluidal supercooled sediment accretion is apparent within stratified sands, deposited englacially at exceptionally high angles of rest in the absence of post‐depositional disturbance. Such primary sediment structures cannot be explained unless sediment is progressively accreted to opposing fracture walls. Ice retreat from areas of former supraglacial outbursts revealed distinct ridges characterized by localized upwellings of sediment‐rich floodwater. These deposits are an important addition to current models of englacial sedimentation and demonstrate the potential for post‐jökulhlaup landform development. Copyright © 2001 John Wiley & Sons, Ltd.
Chalk micropalaeontology and the provenancing of middle pleistocene lowestoft formation till in eastern England
Authors: Fish P. R. , Whiteman C. A.
Published: January 2005

The distribution and deposits of British and Scandinavian Middle Pleistocene ice sheets in eastern England remain problematic. A new till provenancing technique based on Chalk micropalaeontology is described, with the object of refining understanding of the ice sheet which deposited the Lowestoft Formation till (Anglian/Elsterian) and its relationship to Scandinavian ice sheets. The technique involves extracting foraminifera from Chalk erratics and till matrix obtained from stratigraphically controlled till sections and comparing their micropalaeontology with that of Upper Cretaceous Chalk bedrock. Application to the Lowestoft Formation till of eastern England suggests that current models of ice‐flow in this region require revision involving reinstatement of some earlier ideas. Chalk provenance data indicate an initial phase of glaciation, with ice streaming southwards across eastern England before fanning across East Anglia from the position of the Fen basin. This was followed by a later phase in which the main southward trajectory of ice‐flow was located further east in the North Sea Basin, but again with ice fanning out across East Anglia. These ice‐flow trajectories imply constraint of the British ice sheet by Scandinavian ice. Copyright © 2001 John Wiley & Sons, Ltd.
Runoff and interrill erosion on sandy soils under cultivation in the western Paris basin: mechanisms and an attempt at measurement
Authors: Larue Jean Pierre
Published: January 2005

Measurements made on different scales, such as rainfall simulations on 1 m2 and 20 m2 experimental plots and water sampling at the outlet of a watershed, enable the analysis of the mechanisms of pluvial erosion and therefore the importance of runoffs and soil losses in the hilly and sandy parts of the western Paris basin. Interrill erosion accounts for slow transfer of materials towards the lower part of plots and slopes. The overland flow caused by restructuring of the surface Tertiary and Cenomanian soils erodes some 150 to 200 kg ha−1 during the month following sowing. Only a part of these deposits reach the river, which carries away less than 50 kg ha−1 each month. Interrill erosion makes slopes still more uneven, fills in valley bottoms, and so paves the way to catastrophic erosion, which scoops out rises in the ground and colluvial deposits in the lower part of slopes and valley bottoms. Copyright © 2001 John Wiley & Sons, Ltd.
Geomorphological conservation and public policy in England: a geomorphological critique of English Nature's ‘Natural Areas’ approach
Authors: Gray J. Murray
Published: January 2005

The traditional top‐down, site‐based approach to nature conservation has been extended in recent years to include the conservation interests of ‘the wider countryside’. English Nature's response to this movement has been to divide the country into Natural Areas which have coherence in terms of geology, landform, soils, plants and wildlife. These represent more meaningful units for setting nature conservation objectives than do administrative boundaries. They are also intended to allow easier integration of Earth science and wildlife conservation objectives and to provide a meaningful framework into which the interests of individual sites can be set, thus leading to a less fragmented approach to nature conservation. This paper reviews the geomorphological content of the 120 Natural Area Profiles, eight regional summaries and the relevant pages of the English Nature web site. It concludes that wildlife conservation, which dominates the profiles, has fully grasped the principles of conservation in the wider countryside, but geomorphological conservation has largely missed the opportunities provided. The site‐based approach still dominates, there is an inconsistency in approach and the few encouraging geomorphological descriptions or objectives that do occur are never fashioned into sustained geomorphological strategies for the wider countryside. What is needed is a strengthening of geomorphological/Quaternary conservation within English Nature and its Local Area Teams, a more detailed approach to geomorphological description of the Natural Areas which recognizes landform evolution, landform character and sensitivity to change, and improved links between geomorphology and the land‐use planning system. Copyright © 2001 John Wiley & Sons, Ltd.
Empirical predictors of annual bed load travel distance, and implications for salmonid habitat restoration and protection
Authors: Beechie Timothy J.
Published: January 2005

Measurements of annual travel distance (Lb) of bed load sediment at 16 locations in Alaska, the intermountain USA, west coast USA and Scotland are strongly correlated with bankfull channel width (r2 = 0·86, p < 0·001). Travel distance of particles is probably limited by trapping in bars, which have a longitudinal spacing proportional to channel width. Increased abundance of woody debris reduces bar spacing and may reduce Lb. Longer cumulative duration of bed load transporting flows in a year appears to increase Lb. Other predictors of annual travel distance such as stream power per unit length, drainage area and bankfull discharge were less well correlated with Lb (r2 ranging from 0·27 to 0·51). Stream power per unit bed area, basal shear stress and slope were not significantly related to Lb (r2 < 0·05). Most correlations were improved when regressions were limited to data from the west coast USA. Travel distance estimates can be used to help identify reaches that may take longer to recover from large, short‐term increases in sediment supply. Published in 2001 by John Wiley & Sons, Ltd.
An adaptive Lagrangian boundary element approach for three‐dimensional transient free‐surface Stokes flow as applied to extrusion, thermoforming, and rheometry
Authors: Khayat Roger E. , Genouvrier Delphine
Published: January 2005

An adaptive (Lagrangian) boundary element approach is proposed for the general three‐dimensional simulation of confined free‐surface Stokes flow. The method is stable as it includes remeshing capabilities of the deforming free surface and thus can handle large deformations. A simple algorithm is developed for mesh refinement of the deforming free‐surface mesh. Smooth transition between large and small elements is achieved without significant degradation of the aspect ratio of the elements in the mesh. Several flow problems are presented to illustrate the utility of the approach, particularly as encountered in polymer processing and rheology. These problems illustrate the transient nature of the flow during the processes of extrusion and thermoforming, the elongation of a fluid sample in an extensional rheometer, and the coating of a sphere. Surface tension effects are also explored. Copyright © 2001 John Wiley & Sons, Ltd.
Lung effect on the hemodynamics in pulmonary artery
Authors: Tsai S. F. , Sheu Tony W. H. , Chang T. M.
Published: January 2005

The present study investigates blood flow in a pulmonary artery. The aim is to gain a better understanding of offset value in vascular circulation through a two‐dimensional analysis of the Navier–Stokes equations. In this study, the hemodynamics in a blood vessel with truncated outlets at which constant pressure is specified is examined. To simplify the analysis, the vessel walls are regarded as being rigid. In quadratic elements, the streamline upwind Petrov–Galerkin finite element model is employed to simulate the incompressible Newtonian blood flow. The adopted finite element model introduces artificial damping terms solely in the streamline direction. With these terms added to the formulation, the discrete system is enhanced while solution accuracy is maintained without deterioration due to numerical diffusion errors. Copyright © 2001 John Wiley & Sons, Ltd.
Finite element simulation of fully non‐linear interaction between vertical cylinders and steep waves. Part 1: methodology and numerical procedure
Authors: Ma Q. W. , Wu G. X. , Eatock Taylor R.
Published: January 2005

A methodology for computing three‐dimensional interaction between waves and fixed bodies is developed based on a fully non‐linear potential flow theory. The associated boundary value problem is solved using a finite element method (FEM). A recovery technique has been implemented to improve the FEM solution. The velocity is calculated by a numerical differentiation technique. The corresponding algebraic equations are solved by the conjugate gradient method with a symmetric successive overrelaxation (SSOR) preconditioner. The radiation condition at a truncated boundary is imposed based on the combination of a damping zone and the Sommerfeld condition. This paper (Part 1) focuses on the technical procedure, while Part 2 [Finite element simulation of fully non‐linear interaction between vertical cylinders and steep waves. Part 2. Numerical results and validation. International Journal for Numerical Methods in Fluids 2001] gives detailed numerical results, including validation, for the cases of steep waves interacting with one or two vertical cylinders. Copyright © 2001 John Wiley & Sons, Ltd.
Large‐scale eigenvalue calculations for stability analysis of steady flows on massively parallel computers
Authors: Lehoucq Richard B. , Salinger Andrew G.
Published: January 2005

This paper presents an approach for determining the linear stability of steady states of partial differential equations (PDEs) on massively parallel computers. Linearizing the transient behavior around a steady state solution leads to an eigenvalue problem. The eigenvalues with the largest real part are calculated using Arnoldi's iteration driven by a novel implementation of the Cayley transformation. The Cayley transformation requires the solution of a linear system at each Arnoldi iteration. This is done iteratively so that the algorithm scales with problem size. A representative model problem of three‐dimensional incompressible flow and heat transfer in a rotating disk reactor is used to analyze the effect of algorithmic parameters on the performance of the eigenvalue algorithm. Successful calculations of leading eigenvalues for matrix systems of order up to 4 million were performed, identifying the critical Grashof number for a Hopf bifurcation. Copyright © 2001 John Wiley & Sons, Ltd.
Advection upwinding splitting method to solve a compressible two‐fluid model
Authors: Niu Yang‐Yao
Published: January 2005

In this study, the advection upwinding splitting method (AUSM) is modified for the resolution of two‐phase mixtures with interfaces. The compressible two‐fluid model proposed by Saurel and Abgrall is chosen as the model equations. Dense and dilute phases are described in terms of the volume fraction and equations of state to represent multi‐phase mixtures. Test cases involving an air–water shock tube, water faucet, and dilute particulate turbulent flows through a 90° bend are used to verify the current work. It is shown that the AUSM based on flux differences (AUSMD) contains the mechanism to correctly capture the contact discontinuity and interfaces between phases. In addition, a successful application to dilute particulate turbulence flows by the AUSMD is demonstrated. Copyright © 2001 John Wiley & Sons, Ltd.
Viscoelastic simulations of stick‐slip and die‐swell flows
Authors: Ngamaramvaranggul V. , Webster M. F.
Published: January 2005

Numerical solutions of viscoelastic flows are demonstrated for a time marching, semi‐implicit Taylor–Galerkin/pressure‐correction algorithm. Steady solutions are sought for free boundary problems involving combinations of die‐swell and stick‐slip conditions. Flows with and without drag flow are investigated comparatively, so that the influence of the additional component of the drag flow may be analysed effectively. The influence of die‐swell is considered that has application to various industrial processes, such as wire coating. Solutions for two‐dimensional axisymmetric flows with an Oldroyd‐B model are presented that compare favourably with the literature. The study advances our prior fixed domain formulation with this algorithm, into the realm of free‐surface viscoelastic flows. The work involves streamline‐upwind/Petrov–Galerkin weighting and velocity gradient recovery techniques that are applied upon the constitutive equation. Free surface solution reprojection and a new pressure‐drop/mass balance scheme are proposed. Copyright © 2001 John Wiley & Sons, Ltd.
Finite volume multigrid method of the planar contraction flow of a viscoelastic fluid
Authors: Al Moatssime H. , Esselaoui D. , Hakim A. , Raghay S.
Published: January 2005

This paper reports on a numerical algorithm for the steady flow of viscoelastic fluid. The conservative and constitutive equations are solved using the finite volume method (FVM) with a hybrid scheme for the velocities and first‐order upwind approximation for the viscoelastic stress. A non‐uniform staggered grid system is used. The iterative SIMPLE algorithm is employed to relax the coupled momentum and continuity equations. The non‐linear algebraic equations over the flow domain are solved iteratively by the symmetrical coupled Gauss–Seidel (SCGS) method. In both, the full approximation storage (FAS) multigrid algorithm is used. An Oldroyd‐B fluid model was selected for the calculation. Results are reported for planar 4:1 abrupt contraction at various Weissenberg numbers. The solutions are found to be stable and smooth. The solutions show that at high Weissenberg number the domain must be long enough. The convergence of the method has been verified with grid refinement. All the calculations have been performed on a PC equipped with a Pentium III processor at 550 MHz. Copyright © 2001 John Wiley & Sons, Ltd.
The design of improved smoothing operators for finite volume flow solvers on unstructured meshes
Authors: de Foy Benjamin , Dawes William
Published: January 2005

Spatial operators used in unstructured finite volume flow solvers are analysed for accuracy using Taylor series expansion and Fourier analysis. While approaching second‐order accuracy on very regular grids, operators in common use are shown to have errors resulting in accuracy of only first‐, zeroth‐ or even negative‐order on three‐dimensional tetrahedral meshes. A technique using least‐squares optimization is developed to design improved operators on arbitrary meshes. This is applied to the fourth‐order edge sum smoothing operator. The improved numerical dissipation leads to a much more accurate prediction of the Strouhal number for two‐dimensional flow around a cylinder and a reduction of a factor of three in the loss coefficient for inviscid flow over a three‐dimensional hump. Copyright © 2001 John Wiley & Sons, Ltd.
An implicit time‐marching algorithm for shallow water models based on the generalized wave continuity equation
Authors: Dresback Kendra M. , Kolar Randall L.
Published: January 2005

Wave equation models currently discretize the generalized wave continuity equation with a three‐time‐level scheme centered at k and the momentum equation with a two‐time‐level scheme centered at k+1/2; non‐linear terms are evaluated explicitly. However in highly non‐linear applications, the algorithm becomes unstable at even moderate Courant numbers. This paper examines an implicit treatment of the non‐linear terms using an iterative time‐marching algorithm. Depending on the domain, results from one‐dimensional experiments show up to a tenfold increase in stability and temporal accuracy. The sensitivity of stability to variations in the G‐parameter (a numerical weighting parameter in the generalized wave continuity equation) was examined; results show that the greatest increase in stability occurs with G/τ=2–50. In the one‐dimensional experiments, three different types of node spacing techniques—constant, variable, and LTEA (Localized Truncation Error Analysis)—were examined; stability is positively correlated to the uniformity of the node spacing. Lastly, a scaling analysis demonstrates that the magnitudes of the non‐linear terms are positively correlated to those that most influence stability, particularly the term containing the G‐parameter. It is evident that the new algorithm improves stability and temporal accuracy in a cost‐effective manner. Copyright © 2001 John Wiley & Sons, Ltd.
Towards a transparent boundary condition for compressible Navier–Stokes equations
Authors: Bruneau C. H. , Creusé E.
Published: January 2005

A new artificial boundary condition for two‐dimensional subsonic flows governed by the compressible Navier–Stokes equations is derived. It is based on the hyperbolic part of the equations, according to the way of propagation of the characteristic waves. A reference flow, as well as a convection velocity, is used to properly discretize the terms corresponding to the entering waves. Numerical tests on various classical model problems, whose solutions are known, and comparisons with other boundary conditions (BCs), show the efficiency of the BC. Direct numerical simulations of more complex flows over a dihedral plate are simulated, without creation of acoustic waves going back in the flow. Copyright © 2001 John Wiley & Sons, Ltd.
Numerical simulation of the flow field in the vicinity of an axial flow fan
Authors: Meyer C.J. , Kröger D.G.
Published: January 2005

The main purpose of the current investigation is the development and evaluation of a numerical model used to simulate the effect of an axial flow fan on the velocity field in the vicinity of the fan blades. The axial flow fan is modeled as an actuator disc, where the actuator disc forces are calculated using blade element theory. The calculated disc forces are expressed as sources/sinks of momentum in the Navier–Stokes equations solved by a commercially available computational fluid dynamic (CFD) code, Flo++. The model is used to determine the fan performance characteristics of an axial flow fan as well as the velocity fields directly up‐ and downstream of the fan blades. The results are compared with experimental data. In general, good agreement is obtained between the numerical results and experimental data, although the fan power consumption, as well as radial velocity downstream of the fan blades, is underpredicted by the fan model. Copyright © 2001 John Wiley & Sons, Ltd.
On estimation of entrance boundary parameters from downstream measurements using adjoint approach
Authors: Alekseev A.K.
Published: January 2005

An estimation of entrance boundary conditions from the downstream measurements is considered in variational statement form for two‐dimensional supersonic laminar flow. The adjoint problem is used for the calculation of the discrepancy gradient in space of control parameters. The numerical tests presented demonstrate the successful estimation of boundary parameters of spatial distribution by using gradient methods. Copyright © 2001 John Wiley & Sons, Ltd.
Boundary element analysis of driven cavity flow for low and moderate Reynolds numbers
Authors: Aydin M. , Fenner R. T.
Published: January 2005

A boundary element method for steady two‐dimensional low‐to‐moderate‐Reynolds number flows of incompressible fluids, using primitive variables, is presented. The velocity gradients in the Navier–Stokes equations are evaluated using the alternatives of upwind and central finite difference approximations, and derivatives of finite element shape functions. A direct iterative scheme is used to cope with the non‐linear character of the integral equations. In order to achieve convergence, an underrelaxation technique is employed at relatively high Reynolds numbers. Driven cavity flow in a square domain is considered to validate the proposed method by comparison with other published data. Copyright © 2001 John Wiley & Sons, Ltd.
Vortex surface method: some numerical problems of the potential calculation
Authors: Belamri T. , Bakir F. , Kouidri S. , Rey R.
Published: January 2005

The singularities method is used to analyze the flow around an isolated profile or through a plane cascade. In this paper, a numerical study has been developed in order to discuss the accuracy of solutions. The aims of this study are summarized as follows: (1) to expose the elements that influence the method—precision in the geometrical profile definition, trailing‐edge geometry, smoothing problems, number of discretization points, precision of calculation, etc.; (2) to provide an accurate solution for these different problems. For example, some profiles, obtained by the Joukowski transformation, present, in spite of an analytical definition, a crossing of the suction and pressure sides at the trailing edge. This crossing causes a serious error in the velocity field computation. A new procedure to solve this problem is presented. Copyright © 2001 John Wiley & Sons, Ltd.
Vortex method with meshless spatial adaption for accurate simulation of viscous, unsteady vortical flows
Authors: Barba L. A. , Leonard A. , Allen C. B.
Published: January 2005

A vortex method has been developed where spatial adaption of the Lagrangian vortex particles is provided by the technique of radial basis function interpolation. In this way, the meshless formulation of the vortex method is preserved throughout. Viscous effects are provided by the core spreading method, where core size control is accomplished in the spatial adaption, thus ensuring convergence. Numerical experiments demonstrate considerable increase in accuracy, in comparison with standard remeshing schemes used with vortex methods. Proof‐of‐concept is achieved successfully on a problem of quasi‐steady tripole vortex flow, and parallel implementation of the method has permitted high‐accuracy computations of vortex interactions at high Reynolds number. Copyright © 2005 John Wiley & Sons, Ltd.
Anisotropic, isothermal, turbulent swirling flow in a complex combustor geometry
Authors: Jones L. N. , Gaskell P. H. , Thompson H. M. , Gu X. J. , Emerson D. R.
Published: January 2005

The performance of popular second moment closure (LRR, SSG) turbulence models is assessed and compared against experimental data for anisotropic swirling flow in a cylindrical combustion chamber. In contrast to previous studies, where the dissipation anisotropy is correlated with the stress anisotropy, the benefit of approximating the former for swirling flows in terms of the mean strain and vorticity is investigated. Second moment closure models are found to predict mean and turbulent flow quantities reasonably well everywhere except near the wall. The anisotropic dissipation model is found to improve prediction of mean flow quantities near the chamber axis and acts to preserve turbulence further downstream. Copyright © 2005 John Wiley & Sons, Ltd.
High‐resolution simulation of inviscid flow in general domains
Authors: Hall Oskar , Schroll Hans Joachim , Svensson Fredrik
Published: January 2005

In this paper, a high‐resolution finite volume method for calculating solutions to a hyperbolic conservation law is presented. The method works in two space dimensions on general domains and uses curvilinear meshes. A non‐trivial estimation of gradients needed for the reconstructions is presented. The paper contains examples of numerical solutions of the Euler gas dynamics equations. Copyright © 2005 John Wiley & Sons, Ltd.
Splitting methods for high order solution of the incompressible Navier–Stokes equations in 3D
Authors: Brüger Arnim , Gustafsson Bertil , Lötstedt Per , Nilsson Jonas
Published: January 2005

The incompressible Navier–Stokes equations are discretized in space by a hybrid method and integrated in time by the method of lines. The solution is determined on a staggered curvilinear grid in two space dimensions and by a Fourier expansion in the third dimension. The space derivatives are approximated by a compact finite difference scheme of fourth‐order on the grid. The solution is advanced in time by a semi‐implicit method. In each time step, systems of linear equations have to be solved for the velocity and the pressure. The iterations are split into one outer iteration and three inner iterations. The accuracy and efficiency of the method are demonstrated in a numerical experiment with rotated Poiseuille flow perturbed by Orr–Sommerfeld modes in a channel. Copyright © 2005 John Wiley & Sons, Ltd.
Implicit subgrid‐scale models in space–time variational‐multiscale discretizations
Authors: Hulshoff S. J.
Published: January 2005

The behaviour of space–time variational‐multiscale discretizations is investigated using a moving‐wave solution of the one‐dimensional viscous Burgers equation. Effects of spatial discretization parameters are demonstrated using time‐converged numerical results. Two approaches for estimating implicit subgrid‐scale energy dissipation are described, and the dependence of implicit dissipation on spatial discretization parameters is examined. Copyright © 2005 John Wiley & Sons, Ltd.
On numerical flux evaluation using coupled reconstruction based on entropic redundant variables
Authors: de Felice G. , Mazzotti G. , Meola C.
Published: January 2005

This paper describes a novel approach to the simulation of conservation systems based on redundant variables constraints. This allows the imposition of more physical conditions to obtain a better determination of the reconstruction problem. The results achieved for a passive scalar transport and a Burgers equation test case are illustrated. Reported numerical simulations of simple 2D incompressible flows also indicate the good quality of the proposed approach. Copyright © 2005 John Wiley & Sons, Ltd.
Development of a CFD real gas flow solver for hybrid grid
Authors: Cirri Massimiliano , Adami Paolo , Martelli Francesco
Published: January 2005

This paper describes the development and the testing of a CFD real gas flow solver. In the first part of the paper is the description of the analysis performed to define the best approach to a real gas flow solver and the various solution considered. In the second part the various solution adopted are described, in the last part of the paper the CFD solver tests are presented together with results. Copyright © 2005 John Wiley & Sons, Ltd.
Precise FEM solution of a corner singularity using an adjusted mesh
Authors: Burda P. , Novotný J. , Šístek J.
Published: January 2005

Within the framework of the finite element method problems with corner‐like singularities (e.g. on the well‐known L‐shaped domain) are most often solved by the adaptive strategy: the mesh near the corners is refined according to the a posteriori error estimates. In this paper we present an alternative approach. For flow problems on domains with corner singularities we use the a priori error estimates and asymptotic expansion of the solution to derive an algorithm for refining the mesh near the corner. It gives very precise solution in a cheap way. We present some numerical results. Copyright © 2005 John Wiley & Sons, Ltd.
Parallel ILU preconditioning and parallel mesh adaptation with load balancing for general domain decompositions for the Navier–Stokes equations
Authors: Staff Ørnulf , Wille S. Ø.
Published: January 2005

A complete framework for solving the incompressible Navier–Stokes equations in parallel is presented. An unstructured mesh is decomposed into non‐overlapping subdomains corresponding to the number of processors. Each subdomain is adaptively refined independently based on local Reynolds number estimates. Computational load is balanced by transferring element‐octrees between subdomains.

A parallel conjugate gradient solver with ILU preconditioning is achieved by resolving node dependencies based on mesh structure. Each node is sorted by category giving an a priori pivoting suited for parallel solution. The parallel solver has convergence rates comparable to serial solvers with a similar ILU strategy. Copyright © 2005 John Wiley & Sons, Ltd.
Gisbornian (Caradoc) graptolites from New South Wales, Australia: systematics, biostratigraphy and evolution
Authors: Rickards Barrie , Sherwin Lawrence , Williamson Penelope
Published: January 2005

The biodiversity record of graptolites from the Cheeseman's Creek Formation, considered herein as late Gisbornian (Caradoc) in age, has been substantially increased to fifteen taxa, including the new species Dicellograptus praemorrisi sp. nov. and Climacograptus vandenbergi sp. nov. Some of the records have global correlative significance enabling us to identify the wilsoni Biozone ( = calcaratus Biozone of eastern Australia). Several evolutionary lineages have been recognized:

Dicellograptus moffatensis (Carruthers, 1858) →  D. praemorrisi sp. nov → D. morrisi Hopkinson, 1871

Glossograptus hincksi Hopkinson, 1872 → Glossograptus? sp.

Climacograptus bicornis (J. Hall, 1847) → C. vandenbergi sp. nov. → C. lanceolatus VandenBerg, 1990.

Copyright © 2001 John Wiley & Sons, Ltd.
Biodiversity on land and in the sea
Authors: Benton Michael J.
Published: January 2005

Life on land today is as much as 25 times as diverse as life in the sea. Paradoxically, this extraordinarily high level of continental biodiversity has been achieved in a shorter time and it occupies a much smaller area of the Earth's surface than does marine biodiversity. Raw palaeontological data suggest very different models for the diversification of life on land and in the sea. The well‐studied marine fossil record appears to show evidence for an equilibrium model of diversification, with phases of rapid radiation, followed by plateaux that may indicate times of equilibrium diversity. The continental fossil record shows exponential diversification from the Silurian to the present. These differences appear to be real: the continental fossil record is unlikely to be so poor that all evidence for a high initial equilibrial diversity has been lost. In addition, it is not clear that the apparently equilibrial marine model is correct, since it is founded on studies at familial level. At species level, a logistic family‐level curve probably breaks down to an exponential. The rocketing diversification rates of flowering plants, insects, and other land life are evidently hugely different from the more sluggish rates of diversification of life in the sea, perhaps as a result of greater endemism and habitat complexity on land. Copyright © 2001 John Wiley & Sons, Ltd.
The evolutionary radiation of modern birds: systematics and patterns of diversification
Authors: Dyke Gareth J.
Published: January 2005

The timing of the evolutionary radiation of the modern, or neornithine, birds is controversial. The fossil record has indicated that the radiation occurred mainly in the aftermath of the Cretaceous–Tertiary (KT) extinction event. However, recent estimates of lineage divergence times calculated from molecular data have instead indicated that most of the major clades of modern birds originated in the Cretaceous. Because the known Mesozoic fossil record of modern birds is poor, fossils from the early Tertiary provide the first opportunity to document the pattern of the radiation. The limited phylogenetic hypotheses produced to date and including this post‐KT fossil material suggest that only some of the ‘more basal’ clades of modern birds were, most likely, present during the Mesozoic Era, and that the radiation of the ‘more derived’ landbird group of clades occurred in the early Tertiary. Copyright © 2001 John Wiley & Sons, Ltd.
What are Lazarus taxa?
Authors: Fara Emmanuel
Published: January 2005

The many definitions and interpretations associated with the ‘Lazarus effect’ have considerably confused this notion. While several authors regard the Lazarus effect as the temporary disappearance of taxa from the fossil record in any given time interval, many others consider the Lazarus effect as a pattern restricted to mass extinction episodes. The adequacy of the fossil record is the key for interpreting the Lazarus pattern: either Lazarus taxa reflect the incompleteness of the fossil record (the ‘stratigraphic alternative’), or they illustrate genuine extinction‐linked phenomena (the ‘biological alternative’). The latter option includes two traditional hypotheses implying existence of refugia and post‐extinction low population diversity. Differences between these two biological explanations seem to be more rhetorical than substantiated. In addition, the sampling intensity is an external factor commonly linked with both the stratigraphic and the biological alternatives. Interpreting the Lazarus effect is an asymmetrical procedure because the biological alternative is only favoured when the stratigraphic one cannot be documented. Consequently, analytical techniques assessing the completeness of the fossil record are critical to understand the meaning of Lazarus taxa. In particular, gap distributions are better compared with extinction and origination rates rather than with total diversity estimates. Finally, the Lazarus effect should be defined broadly to include range gaps from any given time interval. Copyright © 2001 John Wiley & Sons, Ltd.
Do all mass extinctions represent an ecological crisis? Evidence from the Late Ordovician
Authors: Brenchley P. J. , Marshall J. D. , Underwood C. J.
Published: January 2005

The high rate of species extinction in recent decades is seen by many ecologists as heralding an extinction of catastrophic magnitude in the near future. The ecological consequences of such a biodiversity crisis are hard to predict, but some indication of likely effects can be gained from the knowledge of mass extinctions in the past. The Late Ordovician extinction was one of the five great extinctions in the geological record. It occurred in two phases about 0.5–1million years (Ma) apart and resulted from climatic and related environmental changes associated with the rapid growth and decay of the large Gondwanan ice cap. Overall, an estimated 86% of species became extinct, 61% of genera and 12–24% of families, but few or no orders or higher taxa. The extinction severely affected both marine benthos and plankton. Using brachiopod data as a measure of ecological change, it can be seen that the number of within‐habitat species (alpha diversity) was severely reduced and the number and distinctness of benthic communities (beta diversity) on marine shelves also declined sharply. Concurrently the number of palaeogeographic provinces fell from ten to five, possibly as a result of a loss of endemic species and preferential survival of cosmopolitan species. At the peak of extinction, following the second extinction phase, the ecological structure of both benthic and planktonic ecosystems had been severely disrupted and downgraded in complexity as a wide variety of niches were ‘vacated’. In spite of the profound biodiversity and ecological crisis within this ‘survival’ interval, communities returned to their pre‐extinction levels of alpha and beta diversity during the subsequent ‘recovery’ interval. In spite of the large amount of vacant ecospace to be filled there was very little innovation in terms of adaptive strategy, so that the structure of the emerging Silurian communities was similar to that of the Ordovician. In these terms the ecological recovery was remarkable, but it was also prolonged over about 4–5 Ma. On a geological time scale the biosphere returned to ‘normal’, but on a human time scale the mass extinction produced a very severely degraded biosphere. Copyright © 2001 John Wiley & Sons, Ltd.
Incompleteness of the Permian–Triassic fossil record: a consequence of productivity decline?
Authors: Twitchett Richard J.
Published: January 2005

Analysis of published data shows that, for most animal groups, the fossil record in the immediate aftermath of the end‐Permian biotic crisis is less complete than during the Late Permian or Middle Triassic. Completeness is measured by the Simple Completeness Metric. The interval of poor quality fossil record spans the entire Lower Triassic and may have serious consequences for our perception of the magnitude of the end‐Permian event. A model is presented which seeks to explain this phenomenon. There is abundant evidence that levels of primary productivity were severely reduced in the very latest Permian. In response to this, animal biomass must also have been reduced. The biomass of a particular taxon is the product of the size of individual organisms multiplied by the number of individuals. Those taxa that reduced population size, but maintained original body size, would tend not to be preserved (apparent extinction) and would also be more prone to ‘real’ extinction. Those taxa that retained large population sizes, but reduced body size, would resist extinction and would also maintain their presence in the fossil record. One testable prediction is that taxa present in the fossil record in the immediate aftermath of the end‐Permian crisis will have smaller body size than their pre‐event relatives, regardless of their initial size. Anecdotal evidence supports this prediction. Such a biomass reduction model may also be applicable to other mass extinction events. Copyright © 2001 John Wiley & Sons, Ltd.
Colonization of the deep‐marine environment during the early Phanerozoic: the ichnofaunal record
Authors: Orr Patrick J.
Published: January 2005

Temporal changes in the ichnogeneric diversity and ethological structure of 50 Cambrian to Carboniferous deep‐marine ichnofaunal assemblages were quantified. Assemblages of Cambrian age are distinctive: their diversity is lower, pascichnia and agrichnia relatively unimportant, and ‘shallow‐marine’ ichnotaxa more common, than in subsequent periods. There appear to be no environmental reasons that would have precluded more extensive colonization of the deep‐marine environment during the Cambrian. The significant restructuring of deep‐marine communities at, or near, the Cambrian–Ordovician boundary is therefore attributed to competition for ecospace and/or resources within shallow‐marine environments during the early Phanerozoic, as a result of which ichnotaxa, including examples of pascichnia and agrichnia, were displaced offshore. The Nereites ichnofacies, as traditionally understood, is thus characteristic of only deep‐marine environments younger than the Cambrian. Copyright © 2001 John Wiley & Sons, Ltd.
Palaeozoic brachiopod extinctions, survival and recovery: patterns within the rhynchonelliformeans
Authors: Harper David A. T. , Jia‐Yu Rong
Published: January 2005

The brachiopod‐dominated seabeds of the Palaeozoic were modified by a series of biotic extinctions and recoveries. The ecologic and taxonomic dynamics of the Cambrian and Paleozoic Evolutionary Faunas were interrupted during the late Cambrian, end‐Ordovician, late Devonian and end‐Permian by a multiple series of extinctions. While the balance between the deltidiodont and cyrtomatodont rhynchonelliformeans was maintained during the Palaeozoic, the dominant role of the orthides and strophomenides during the early to mid‐Palaeozoic was usurped by the productides during the late Palaeozoic. The deltidiodont morphology did not survive the end‐Permian extinctions; the modern articulated brachiopod fauna is dominated by cyrtomatodonts with crurae and loops. Nevertheless, a recurring trend is the long‐term success of brachiopod taxa with widespread distributions and the demise of the more specialized and highly adapted morphs having more restricted distributions commonly evolved during interregna between phases of extinction. Copyright © 2001 John Wiley & Sons, Ltd.
Biodiversity and the history of reefs
Authors: Wood Rachel
Published: January 2005

Current biodiversity estimates suggest that modern coral reefs house between 4 and 5% of all described species, although increasingly sophisticated molecular techniques may reveal the actual diversity to be far higher. The origins and maintenance of this considerable taxonomic biodiversity remain, however, poorly known, particularly as the relative importance of controls that maintain the structure of reef communities differ according to the scale of consideration. The diversity of local coral reef communities is strongly correlated with water depth and differences between habitats. Ecological structure is considered to be ordered mainly by interspecific interactions and differential responses to disturbance, whereas determinants of diversity at regional geographical scales include variation in rates of dispersal and recruitment from the available metapopulation. On evolutionary timescales, historical events such as unique radiations of key taxa and mass extinctions appear to be the main controls on biodiversity change. All these processes operate simultaneously, and must be integrated in order to gain an understanding of the evolutionary perspective. Depending upon the scale of population considered, reef communities may operate as both individualistic assemblages of taxa with similar requirements, and as more tightly integrated ecological entities. Copyright © 2001 John Wiley & Sons, Ltd.
A facile stereoselective synthesis of (E)‐1,2‐disubstituted vinylic selenides via hydromagnesiation of alkylarylacetylenes
Authors: Cai Mingzhong , Xia Jun , Hao Wenyan
Published: January 2005

Hydromagnesiation of alkylarylacetylenes 1 in diethyl ether gave (E)‐α‐arylvinyl Grignard reagents 2, which reacted with arylselenenyl bromides 3 in THF to afford stereoselectively (E)‐1,2‐disubstituted vinylic selenides
4 in good yields. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:65–68, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20066
Syntheses, characterizations and crystal structures of new triorganotin complexes with 2‐mercaptopyrimidine and 4‐amino‐2‐mercaptopyrimidine
Authors: Ma Chunlin , Shi Yang , Jiang Qin
Published: January 2005

Four triorganotin(IV) complexes with 2‐mercaptopyrimidine (HSpym) and 4‐amino‐2‐mercaptopyrimidine (HSapym) of the type, R3SnL (L= Spym, R=Ph, 1; R=PhCH2, 2; L=Sapym, R=Ph, 3; R=PhCH2, 4), were synthesized. All the complexes 1–4 have been characterized by elemental, IR, 1H NMR, and X‐ray crystallography diffraction analyses, which revealed that the structures of 1–4 are penta‐coordinated with R3Sn‐coordinated to the thiol S and heterocyclic N atoms, and the structural distortion for each is a displacement from tetragonal toward trigonal bipyramidal geometry. The complex 1 is a one‐dimensional chain complex, while compounds 3 and 4 are dimers due to the existence of N···H hydrogen bonding. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:69–75, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20068
New access to pyrazole, oxa(thia)diazole and oxadiazine derivatives
Authors: Hassan Alaa A. , El‐Shaieb Kamal M. , Shaker Raafat M. , Döpp Dietrich
Published: January 2005

1,4‐Disubstituted thiosemicarbazides 1b–f reacted with ethenetetracarbonitrile (5) in di‐ methylformamide with formation of 2‐substituted 5‐phenyl‐1,3,4‐thiadiazoles 2a–f and 2‐substituted 5‐phenyl‐1,3,4‐oxadiazoles 4a–f. Upon addition of 5 to 1c–e in chlorobenzene, 3‐amino‐2‐benzoyl‐4,5,5‐tri‐ cyano‐2,5‐dihydro‐1H‐pyrazole‐1‐[N‐(4‐tricyanovi‐nyl)phenyl]carbothioamide (12), 5‐benzylamino‐, and 5‐allylamino‐4‐benzoyl‐2,3‐dihydro‐[1,3,4]thiadiazol‐ 2,2‐dicarbonitrile (13a,b) and 5‐amino‐1‐benzoylpyrazole‐3,4‐dicarbonitrile (14) as well as 2‐phenyl‐ 4H‐[1,3,4]‐oxadiazine‐5,6‐dicarbonitrile (15) were formed. Rationales for the role of the solvent and the conversions observed are presented. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:12–19, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20071
Synthesis of 3‐aryl(hetaryl)‐1,2,3‐diazaphospholines
Authors: Chaikovskaya Aleksandra A. , Kudrya Tamara N. , Lakhtadir Aleksandr I. , Smaliy Radomir V. , Pinchuk Aleksandr M. , Tolmachev Andrei A.
Published: January 2005

A reaction of cyclohexanone phenylhydrazone with (het)aryldihalogenophosphines has been studied. As shown, cyclohexanone phenylhydrazone reacts with phenyldibromophosphine and 5‐methyl‐2‐furyldibromophosphine to provide the corresponding 1,2,3‐diazaphospholines in high yields. The diazaphospholines thus obtained have been derivatized. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:81–83, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20074