bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical method for unsteady compressible boundary layers driven by compression or expansion wave
Authors: Kim Jae‐Soo , Chang Keun‐Shik
Published: October 2005

A numerical analysis is presented for the unsteady compressible laminar boundary layer driven by a compression or expansion wave. Approximate or series expansion methods have been used for the problems because of the characteristics of the governing equations, such as non‐linearity, coupling with the thermal boundary layer equation and initial conditions. Here a transformation of the governing equations and the numerical linearization technique are introduced to deal with the difficulties. First, the governing equations are transformed for the initial conditions by Howarth and semisimilarity variables. These transformations reduce the number of independent variables from three to two and the governing equations from partial to ordinary differential equations at the initial point. Next, the numerical linearization technique is introduced for the non‐linearity and the coupling with the thermal boundary layer equation. Because the non‐linear terms are linearized without sacrifice of numerical accuracy, the solutions can be obtained without numerical iterations. Therefore the exact numerical solution, not approximate or series expansion, can be obtained. Compared with the approximate or series expansion method, this method is much improved. Results are compared with the series expansion solutions.
Three‐dimensional simulations of natural convection in a sidewall‐heated cube
Authors: Fusegi Toru , Hyun Jae Min , Kuwahara Kunio
Published: October 2005

A high‐resolution, finite difference numerical study is reported on three‐dimensional natural convection of air in a differentially heated cubical enclosure over an extensive range of Rayleigh number from 103 to 1010. The maximum number of grid points is 122 × 62 × 62. Solutions to the primitive variable formulation of the incompressible Navier‐Stokes and energy equations are acquired by a control‐volume‐based procedure together with a higher‐order upwind‐differencing technique. The field characteristics at large‐time limits are examined in detail by state‐of‐the‐art numerical visualizations of the three‐dimensional results. The emergence of the well‐defined boundary layers and the interior core at high Rayleigh numbers is captured by elaborate numerical visualizations. Both the similarities and discrepancies between the three‐ and two‐dimensional computations are pointed out. These emphasize the need for three‐dimensional calculations to accurately determine the flow characteristics and heat transfer properties in realistic, high‐Rayleigh‐number situations.
Semi‐implicit finite difference methods for three‐dimensional shallow water flow
Authors: Casulli Vincenzo , Cheng Ralph T.
Published: October 2005

A semi‐implicit finite difference method for the numerical solution of three‐dimensional shallow water flows is presented and discussed. The governing equations are the primitive three‐dimensional turbulent mean flow equations where the pressure distribution in the vertical has been assumed to be hydrostatic. In the method of solution a minimal degree of implicitness has been adopted in such a fashion that the resulting algorithm is stable and gives a maximal computational efficiency at a minimal computational cost. At each time step the numerical method requires the solution of one large linear system which can be formally decomposed into a set of small three‐diagonal systems coupled with one five‐diagonal system. All these linear systems are symmetric and positive definite. Thus the existence and uniquencess of the numerical solution are assured. When only one vertical layer is specified, this method reduces as a special case to a semi‐implicit scheme for solving the corresponding two‐dimensional shallow water equations. The resulting two‐ and three‐dimensional algorithm has been shown to be fast, accurate and mass‐conservative and can also be applied to simulate flooding and drying of tidal mud‐flats in conjunction with three‐dimensional flows. Furthermore, the resulting algorithm is fully vectorizable for an efficient implementation on modern vector computers.
Improved shock‐capturing of Jameson's scheme for the Euler equations
Authors: Van Der Burg J. W. , Kuerten J. G. M. , Zandbergen P. J.
Published: October 2005

It is known that Jameson's scheme is a pseudo‐second‐order‐accurate scheme for solving discrete conservation laws. The scheme contains a non‐linear artificial dissipative flux which is designed to capture shocks. In this paper, it is shown that the, shock‐capturing of Jameson's scheme for the Euler equations can be improved by replacing the Lax‐Friedrichs' type of dissipative flux with Roe's dissipative flux. This replacement is at a moderate expense of the calculation time.
A finite volume approach to large eddy simulation of compressible, homogeneous, isotropic, decaying turbulence
Authors: Vreman A. W. , Geurts B. J. , Kuerten J. G. M. , Zandbergen P. J.
Published: October 2005

Large eddy simulation of compressible, homogeneous, isotropic, decaying turbulence in a rectangular box is performed using finite volume techniques. An analysis of the energy spectra obtained from the simulations shows that an agreement with the Kolmogorov law for the inertial range is found only when an appropriate spatial discretization method is used. This agreement is obtained both for a low (0·05) and a moderate (0·6) Mach number when Smagorinsky's subgrid model is employed.
Numerical solution of transonic full‐potential‐equivalent equations in von Mises co‐ordinates
Authors: An C.‐F. , Barron R. M.
Published: October 2005

In this paper a new approach to calculate transonic flows is developed. A set of full‐potential‐equivalent equations in the von Mises co‐ordinate system is formulated under the irrotationality and isentropic assumptions. The emphasis is placed on supercritical flow, in which the treatment of embedded shock waves is crucial to get convergent solutions. Shock jump conditions are employed and shock point operators (SPOs) are constructed in the body‐fitting streamline co‐ordinate system. SPOs and a type‐dependent difference scheme are applied to solve the ‘main’ equation for the ‘main’ variable, the streamline ordinate y. A number of ‘secondary’ equations are deduced for the corresponding ‘secondary’ variables. An optimal combination for the ‘secondary’ variable, its equation and related difference scheme is selected to be the generalized density R, its linear equation and the Crank‐Nicolson scheme. Numerical results show that the present approach gives good agreement with experimental data and other computational work for NACA0012 and biconvex aerofoils in both subcritical and supercritical ranges.
The behaviour of several stress–velocity–pressure mixed finite elements for Newtonian flows
Authors: Buscaglia Gustavo C.
Published: October 2005

The Q2/P1, P/P1, P2/P0 and Q1/P0 velocity–pressure mixed elements are extended to the stress–velocity–pressure formulation, using the same interpolants for stress and velocity, and tested in the 4‐to‐1 contraction problem for Stokes flow. The comparison shows significant differences among them, which are not present when the velocity–pressure formulation is used.

To provide a better understanding of the phenomenon, several variants of the previous elements are introduced, obtained by either changing the pressure space or by enriching the stress space with bubble functions. The formulation exhibits a strong sensitivity to the first alternative, while the second produces only a minor effect. These observations are confirmed by a convergence test effected on a regular problem with the explicit analytical solution. Also, as a result of the whole comparison, the P/P/P1 element looks promising for three‐field calculations.
Shallow flow modelling using curvilinear depth‐averaged stream function and vorticity transport equations
Authors: Borthwick A. G. L. , Kaar E. T.
Published: October 2005

Most receiving water, such as lakes and open reservoirs, have large plan dimensions with respect to their depth. In such cases, the flow may be nearly two‐dimensional and the depth‐averaged Reynolds equations are appropriate. This paper presents a new version of the governing equations in curvilinear depth‐averaged stream function and vorticity transport (ψ, ω) form appropriate for non‐orthogonal computational meshes. The equations are discretized using finite differences and solved using successive over‐relaxation for the depth‐averaged stream function equation and an alternating direction implicit scheme for the vorticity transport equation. Results from the numerical model are validated against data from flow past a backward facing step and jet‐forced flow in a circular reservoir. The results indicate that the (ψ, ω) form of the shallow water equations may be useful for applications where the free surface can either be assumed horizontal, or is know a priori.
Is the steady viscous incompressible two‐dimensional flow over a backward‐facing step at Re = 800 stable?
Authors: Gresho Philip M. , Gartling David K. , Torczynski J. R. , Cliffe K. A. , Winters K. H. , Garratt T. J. , Spence A. , Goodrich John W.
Published: October 2005

A detailed case study is made of one particular solution of the 2D incompressible Navier–Stokes equations. Careful mesh refinement studies were made using four different methods (and computer codes): (1) a high‐order finite‐element method solving the unsteady equations by time‐marching; (2) a high‐order finite‐element method solving both the steady equations and the associated linear‐stability problem; (3) a second‐order finite difference method solving the unsteady equations in streamfunction form by time‐marching; and (4) a spectral‐element method solving the unsteady equations by time‐marching. The unanimous conclusion is that the correct solution for flow over the backward‐facing step at Re = 800 is steady—and it is stable, to both small and large perturbations.
An adaptive multigrid finite‐volume scheme for incompressible Navier–Stokes equations
Authors: Lin San‐Yih , Wu Tsuen‐Muh
Published: October 2005

An algorithm for the solutions of the two‐dimensional incompressible Navier–Stokes equations is presented. The algorithm can be used to compute both steady‐state and time‐dependent flow problems. It is based on an artificial compressibility method and uses higher‐order upwind finite‐volume techniques for the convective terms and a second‐order finite‐volume technique for the viscous terms. Three upwind schemes for discretizing convective terms are proposed here. An interesting result is that the solutions computed by one of them is not sensitive to the value of the artificial compressibility parameter. A second‐order, two‐step Runge–Kutta integration coupling with an implicit residual smoothing and with a multigrid method is used for achieving fast convergence for both steady‐ and unsteady‐state problems. The numerical results agree well with experimental and other numerical data. A comparison with an analytically exact solution is performed to verify the space and time accuracy of the algorithm.
The numerical solution of the flow in a general bifurcating channel at moderately high Reynolds number using boundary‐fitted co‐ordinates, primitive variables and Newton iteration
Authors: Hunt Roland
Published: October 2005

A numerical code has been implemented for the numerical solution of the steady, incompressible Navier–Stokes equations using primitive variables in a bifurcating channel. A boundary‐fitted, numerically generated grid is placed onto the domain of the channel which is transformed into either a rectilinear C‐ or T‐shaped region. The differenced equations are solved using Newton's iteration which makes upwinding at high Reynolds number unnecessary. Practical implications of inverting the huge Jacobian matrix of Newton's method are discussed. The results have relative error of 2–3 × 10−3 at Reynolds number 100, with T‐geometry being marginally but significantly more accurate than C‐geometry. Results have been obtained for Reynolds numbers up to 1000 for three bifurcations one of which models the carotid arterial bifurcation in the human head. For this latter bifurcation the wall shear stress is calculated in connection with the onset of atherosclerosis. Finally, the results of flows having different daughter tube end pressures are presented.
Integral transform analysis of natural convection in porous enclosures
Authors: Baohua Cai , Cotta R. M.
Published: October 2005

A hybrid numerical‐analytical solution for steady‐state natural convection in a porous cavity is proposed, based on application of the ideas in the generalized integral transform technique. The integral transformation process reduces the original coupled partial differential equations, for temperature and stream function, into an infinite system of non‐linear ordinary differential equations for the transformed potentials, which is adaptively truncated and numerically solved through well‐established algorithms. The approach is applied to a vertical rectangular enclosure subjected to uniform internal heat generation. The convergence characteristics of the explicit inversion formulae are illustrated and critical comparisons with previously reported purely numerical solutions are performed.
Boundary element method for steady 2D high‐Reynolds‐number flow
Authors: Rek Z. , Škerget L.
Published: October 2005

This paper deals with the numerical simulation of fluid dynamics using the boundary–domain integral technique (BEM). The steady 2D diffusion–convection equations are discussed and applied to solve the plane Navier‐Stokes equations. A vorticity–velocity formulation has been used. The numerical scheme was tested on the well‐known ‘driven cavity’ problem. Results for Re = 1000 and 10,000 are compared with benchmark solutions. There are also results for Re = 15,000 but they have only qualitative value. The purpose was to show the stability and robustness of the method even when the grid is relatively coarse.
Computation of unsteady laminar viscous flow past an aerofoil using the CPI method
Authors: Deng G. B. , Guilmineau E. , Piquet J. , Queutey P. , Visonneau M.
Published: October 2005

The present work is a discussion of the computation of unsteady laminar incompressible two‐dimensional viscous flow past complex geometries. A new physically consistent method is presented for the reconstruction of velocity fluxes which arise from the mass and momentum balance discrete equations. This closure method for fluxes makes possible the use of a cell‐centred grid in which velocity and pressure unknowns share the same location while circumventing the occurrence of spurious pressure modes. The method is validated using the impulsively started cylinder problem for circular or aerofoil‐like shapes at several Reynolds numbers of the order of 103–104.
An element level zero‐divergence finite element approach
Authors: Mack A. N. F.
Published: October 2005

An innovative idea for the solution of viscous incompressible flows, in which the equation for conservation of mass is satisfied at the element level, is termed the solenoidal finite element approach. The term ‘solenoidal’ derives from the fact that the velocity components need to be solenoidal, i.e. to have zero divergence. The difficulty with this idea centres on the construction of a specialized element in which the velocity components are constrained to be solenoidal by the nature of their interpolation functions. If such an element can be constructed, then the pressure is suppressed from the prime solution. This has obvious attractions, although recourse to another novel idea is needed for its eventual retrieval. The validity of these ideas is demonstrated herein by the results for some classical benchmark problems. Where possible, comparisons are made with other results, both from other codes and from the literature.
Prediction of turbulent wall shear flows directly from wall
Authors: Jaw Shenq‐Yuh , Hwang Robert R.
Published: October 2005

The fully elliptic Reynolds‐averaged Navier–Stokes equations have been used together with Lam and Bremhorst's low‐Reynolds‐number model, Chen and Patel's two‐layer model and a two‐point wall function method incorporated into the standard k‐ϵ model to predict channel flows and a backward‐facig step flow. These flows enable the evaluation of the performance of different near‐wall treatments in flows involving streamwise and normal pressure gradients, flows with separation and flows with non‐equilibrium turbulence characteristics. Direct numerical simulation (DNS) of a channel flow with Re =3200 further provides the detailed budgets of each modelling term of the k and ϵ‐transport equations. Comparison of model results with DNS data to evaluate the performance of each modelling term is also made in the present study. It is concluded that the low‐Reynolds‐number model has wider applicability and performs better than the two‐layer model and wall function approaches. Comparison with DNS data further shows that large discrepancies exist between the DNS budgets and the modelled production and destruction terms of the ϵ equation. However, for simple channel flow the discrepancies are similar in magnitude but opposite in sign, so they are cancelled by each other. This may explain why, even when employing such an inaccurately modelled ϵ‐equation, one can still predict satisfactorily some simple turbulent flows.
Damped artificial compressibility iteration scheme for implicit calculations of unsteady incompressible flow
Authors: McHugh P. R. , Ramshaw J. D.
Published: October 2005

Peyret (J. Fluid Mech., 78, 49–63 (1976)) and others have described artificial compressibility iteration schemes for solving implicit time discretizations of the unsteady incompressible Navier‐Stokes equations. Such schemes solve the implicit equations by introduing derivatives with respect to a pseudo‐time variable τ and marching out to a steady state in τ. The pseudo‐time evolution equation for the pressure p takes the form ∂p/∂ = −a2∂∇.u, where a is an artificial compressibility parameter and u is the fluid velocity vector. We present a new scheme of this type in which convergence is accelerated by a new procedure for setting a and by introducing an artificial bulk viscosity b into the momentum equation. This scheme is used to solve the non‐linear equations resulting from a fully implicit time differencing scheme for unsteady incompressible flow. We find that the best values of a and b are generally quite different from those in the analogous scheme for steady flow (J. D. Ramshaw and V. A. Mousseau, Comput. Fluids, 18, 361–367 (1990)), owing to the previously unrecognized fact that the character of the system is profoundly altered by the pressence of the physical time derivative terms. In particular, a Fourier dispersion analysis shows that a no longer has the significance of a wave speed for finite values of the physical time step δt,. Inded, if on sets a ˜ |u| as usual, the artificial sound waves cease to exist when δt is small and this adversely affects the iteration convergence rate. Approximate analytical expressions for a and b are proposed and the benefits of their use relative to the conventional values a ∼ |u| and b = 0 are illustrated in simple test calculations.
An h4 accurate vorticity‐velocity formulation for calculating flow past a cylinder
Authors: Dennis S. C. R. , Hudson J. D.
Published: October 2005

A method of solution for the two‐dimensional Navier‐Stokes equations for incompressible flow past a cylinder is given in which the euquation of continuity is solved by a step‐by‐step integration procedure at each stage of an interative process. Thus the formulation involves the solution of one first‐order and one second‐order equation for the velocity components, together with the vorticity transport equation. the equations are solved numerically by h4‐accurate methods in the case of steady flow past a circular cylinder in the Reynolds number range 10–100. Results are in satisfactory agreement with recent h4‐accurate calculations. An improved approximation to the boundary conditions at large distance is also considered.
An investigation of artificial dissipation for the cell‐vertex finite volume method
Authors: Mackenzie J. A.
Published: October 2005

This paper is concerned with an investigation of artificial dissipation models that are used with the cell‐vertex finite volume approximation of the compressible Euler and Navier‐Stokes equations. Based on the observation that first and second‐order upwind schemes can be written as a central discretization plus an appropriately scaled dissipative flux, a matrix scaling of second and fourth‐differences is implemented in an artificial dissipation model that also uses a procedure to limit the applicability of shock‐capturing dissipation. Analysis of the model and the associated boundary conditions is given to determine the effect on accuracy. Numerical results are given for transonic Euler flow past a NACA0012 aerofoil profile which demonstrate the improved shock‐capturing capability of the model. Results for laminar subsonic viscous flow over a flat plate show that the matrix‐dissipation model reduces the amount of spurious artificial dissipation within boundary layers.
An application of Roe's flux‐difference splitting for k‐ϵ turbulence model
Authors: Siikonen Timo
Published: October 2005

In this paper Roe's flux‐difference splitting is applied for the solution of Reynolds‐averaged Navier‐Stokes equations. Turbulence is modelled using a low‐Reynolds number form of the k‐ϵ tubulence model. The coupling between the turbulence kinetic energy equation and the inviscid part of the flow equations is taken into account. The equations are solved with a diagonally dominant alternating direction implicit (DDADI) factorized implicit time integration method. A multigrid algorithm is used to accelerate the convergence. To improve the stability some modifications are needed in comparison with the application of an algebraic turbulence model. The developed method is applied to three different test cases. These cases show the efficiency of the algorithm, but the results are only marginally better than those obtained with algebraic models.
Numerical modelling of ice jam resistance to main channel flow
Authors: Saadé Raafat G. , Amruthur  , Ramamurthy S. , Troitsky Michael S.
Published: October 2005

In northern countries, subfreezing temperatures during the winter season result in the formation of ice covers on most rivers. Towards the end of the winter season, during the spring break‐up period, stationary ice covers become weak in strength and break up. The resulting broken ice pieces or ice floes are significantly larger in thickness and have a rougher undersurface relative to sheet ice and impose higher hydraulic resistance. The downstream movement of the ice floes may be arrested under conditions such as an intact ice cover, bridge piers or channel constrictions, among others, thereby initiating a break‐up ice jam. These ice jams most often have been observed to cause very high water stages. Detrimental effects caused by these high water levels encompass those of operational and design‐related problems such as the flooding of communities due to ice‐jam‐induced backwater, flood risk assessments, altering of the open water flow regime, bed scour and flooding of bridges.

The ability to predict the influence of an ice jam on the main flow is of considerable importance in river engineering and can be viewed upon by its effects on the variation in the water surface levels. All other information is dependent on the foregoing. The ice jam influence on the main flow can be regarded with respect to local and global standpoints.

The primary objective of this study is to formulate the influence of the ice jam on the main channel flow. The formulation is then coupled with a two‐dimensional numerical model for the simulation of the water flow regime. The data from different laboratory experiments on ice jams are reproduced numerically. Various simulations are then carried out to compute the water surface levels and velocities in channels under ice jam conditions. The numerical results are then compared with the laboratory data.

Results show that the mathematical formulation developed to predict the water surface levels and velocities along the ice jam length as well as upstream and downstream of its leading and trailing edges respectively gives satisfactory predictions.
Implementation of some higher‐order convection schemes on non‐uniform grids
Authors: Li Yuguo , Baldacchino Lisa
Published: October 2005

A generalized formulation is applied to implement the quadratic upstream interpolation (QUICK) scheme, the second‐order upwind (SOU) scheme and the second‐order hybrid scheme (SHYBRID) on non‐uniform grids. The implementation method is simple. The accuracy and efficiency of these higher‐order schemes on non‐uniform grids are assessed. Three well‐known bench mark convection‐diffusion problems and a fluid flow problem are revisited using non‐uniform grids. These are: (1) transport of a scalar tracer by a uniform velocity field; (2) heat transport in a recirculating flow; (3) two‐dimensional non‐linear Burgers equations; and (4) a two‐dimensional incompressible Navier‐Stokes flow which is similar to the classical lid‐driven cavity flow. The known exact solutions of the last three problems make it possible to thoroughly evaluate accuracies of various uniform and non‐uniform grids. Higher accuracy is obtained for fewer grid points on non‐uniform grids. The order of accuracy of the examined schemes is maintained for some tested problems if the distribution of non‐uniform grid points is properly chosen.
Estimation of canopy drying time after rainfall using sap flow measurements in an emergent tree in a lowland mixed‐dipterocarp forest in Sarawak, Malaysia
Authors: Kume Tomonori , Kuraji Koichiro , Yoshifuji Natsuko , Morooka Toshiyuki , Sawano Shinji , Chong Lucy , Suzuki Masakazu
Published: October 2005

This study emphasizes the importance of canopy drying time (CDT) after rainfall in a lowland tropical rain forest. In this study, we estimate CDT using sap flow velocities measured by a heat‐pulse method in an emergent tree in a lowland mixed‐dipterocarp forest. Estimated CDT (ECDT) for each rain event has been defined as the time from rainfall cessation to the specific time derived from the difference between diurnal courses of sap flow velocities on a rainy day versus bright days. ECDT could be derived for 22 rain events that were grouped into two types, depending on whether rainfall ceased before or after noon. The ECDTs were distributed more widely and with greater values when rainfall ceased before noon (Type 1) than after noon (Type 2). The ECDTs of both Type 1 and Type 2 decreased with increases in net radiation (Rn) and vapour pressure deficit (VPD) after rainfall. This result shows that ECDT is determined mainly by post‐rainfall evaporation rates. The sap flow velocity as a detector of canopy wetness worked out well because of the specific rainfall characteristics at this site. The practical limitations of the method using sap flow velocities are discussed in relation to rainfall characteristics and time lags between transpirations and sap flow velocities. Copyright © 2005 John Wiley & Sons, Ltd.
A modification to the Soil Conservation Service curve number method for steep slopes in the Loess Plateau of China
Authors: Huang Mingbin , Gallichand Jacques , Wang Zhanli , Goulet Monique
Published: October 2005

The Soil Conservation Service curve number (CN) method is widely used for predicting direct runoff from rainfall. However, despite the extent of cultivation on hillslope areas, very few attempts have been made to incorporate a slope factor into the CN method. The objectives of this study were (1) to evaluate existing approaches integrating slope in the CN method, and (2) to develop an equation incorporating a slope factor into the CN method for application in the steep slope areas of the Loess Plateau of China. The dataset consisted of 11 years of rainfall and runoff measurements from two experimental sites with slopes ranging from 14 to 140%. The results indicated that the standard CN method underestimated large runoff events and overestimated small events. For our experimental conditions, the optimized and non‐optimized forms of the slope‐modified CN method of the Erosion Productivity Impact Calculator model improved runoff prediction for steep slopes, but large runoff events were still underestimated and small ones overpredicted. Based on relationships between slope and the observed and theoretical CN values, an equation was developed that better predicted runoff depths with an R2 of 0·822 and a linear regression slope of 0·807. This slope‐adjusted CN equation appears to be the most appropriate for runoff prediction in the steep areas of the Loess Plateau of China. Copyright © 2005 John Wiley & Sons, Ltd.
Depth distribution of interrill overland flow and the formation of rills
Authors: Parsons Anthony J. , Wainwright John
Published: October 2005

A Gumbel distribution for maxima is proposed as a model for the depths of interrill overland flow. The model is tested against three sets of field measurements of interrill overland flow depths obtained on shrubland and grassland hillslopes at Walnut Gulch Experimental Watershed, southern Arizona. The model is found to be a satisfactory fit to 81 of the 90 measured distributions. The shape δ and location λ parameters of all fitted distributions are strongly correlated with discharge. However, whereas a common relationship exists between discharge and δ for all depth distributions, the relationships with λ vary systematically downslope. Using the Gumbel distribution as a model for the distribution of overland flow depths, a probabilistic model for the initiation of rills is developed, drawing upon the previous work of Nearing. As an illustration of this approach, we apply this model to the shrubland and grassland hillslopes at Walnut Gulch. It is concluded that the presence of rills on the shrubland, but not on the grassland, is due to the greater runoff coefficient for the shrubland and/or the greater propensity of the shrubland for soil disturbance compared with the grassland. Finally, a generalized conceptual model for rill initiation is proposed. This model takes account of the depth distribution of overland flow, the probability of flow shear stress in excess of local soil shear strength, the spatial variability in soil shear strength and the diffusive effect of soil detachment by raindrops. Copyright © 2005 John Wiley & Sons, Ltd.
Gefitinib, a selective EGFR tyrosine kinase inhibitor, induces apoptosis through activation of Bax in human gallbladder adenocarcinoma cells
Authors: Ariyama Hiroshi , Qin Baoli , Baba Eishi , Tanaka Risa , Mitsugi Kenji , Harada Mine , Nakano Shuji
Published: October 2005

Although gefitinib, a selective inhibitor of epidermal growth factor receptor (EGFR) tyrosine kinase, has been clinically demonstrated to be effective for certain cancer cell types, the molecular mechanisms of the anti‐tumor activity have not been fully elucidated. In this study, we investigated the mechanism of gefitinib‐induced growth inhibition and apoptosis in HAG‐1 human gallbladder adenocarcinoma cells. Treatment of gefitinib at a dose of 1 µM resulted in a significant growth inhibition, and the cell number irreversibly declined after 72‐h incubation, with a progressive expansion of apoptotic cell population over 120‐h. Following 2‐h treatment, gefitinib significantly inhibited EGFR autophosphorylation and subsequent downstream signaling pathway through Erk and Akt, and induced accumulation of cells in the G0/G1 phase of the cell cycle at 24‐h, accompanied by a concomitant increase in p21 transcript and increased expression of p27. Gefitinib did not affect the amount of total and phosphorylated p53 at serine 15, but upregulated the expression of total Bax, with subsequent increase in p18 Bax, an active form of Bax. The expression of Bcl‐2 and Bad was unchanged. An increase in gefitinib‐induced expression of total Bax might be due to the decreased degradation of Bax, because the level of Bax mRNA has not been altered by gefitinib treatment. Gefitinib promoted the cleavage of full‐length p21 Bax into p18 Bax in mitochondrial‐enriched fraction, a characteristic feature of Bax activation toward apoptosis. Moreover, blockade of Bax by using anti‐Bax small interfering double stranded RNA (siRNA) significantly reduced gefitinib‐induced apoptosis. Taken together, these data suggest a critical role of p18 Bax in gefitinib‐induced apoptosis. J. Cell. Biochem. 97: 724–734, 2006. © 2005 Wiley‐Liss, Inc.
HIF‐1α has an anti‐apoptotic effect in human airway epithelium that is mediated via Mcl‐1 gene expression
Authors: Liu Xiu‐Huai , Yu Erik Z. , Li Ying‐Yue , Kagan Elliott
Published: October 2005

Hypoxia‐inducible factor‐1α (HIF‐1α) and myeloid cell leukemia‐1 (Mcl‐1) proteins have been shown to regulate apoptosis in some cell systems but have not been studied in this context in airway epithelium. Using a model of anoxia/reoxygenation (A/R), the present study employed RNA interference (RNAi) targeting HIF‐1α and Mcl‐1 to evaluate their possible anti‐apoptotic effects on HBE1 cells, an immortalized human bronchial epithelial cell line. The cells were either cultured under normoxic conditions or were transfected with small interfering RNA (siRNA) duplexes targeting HIF‐1α or Mcl‐1 mRNA and then immediately exposed to A/R. As controls, non‐transfected HBE1 cells and cells transfected with scrambled RNA duplexes were subjected to A/R. Apoptosis was evaluated by terminal deoxynucleotidyl transferase (TdT)‐mediated dUTP nick end labeling (TUNEL) assay and RNAi was assessed by knockdown of HIF‐1α and Mcl‐1 mRNA and protein expression using real‐time quantitative RT‐PCR (Q‐PCR), immunohistochemistry, and Western blots. HBE1 cells transfected with siRNA duplexes targeting either HIF‐1α or Mcl‐1 and subjected to A/R manifested considerable apoptosis, a finding not observed in either non‐transfected cells or cells transfected with scrambled RNA duplexes. Specific knockdown of mRNA and protein expression by RNAi in HBE1 cells after A/R was shown for siRNA duplexes targeting either HIF‐1α or Mcl‐1. Unexpectedly, knockdown of HIF‐1α induced parallel knockdown of Mcl‐1 mRNA and protein expression, whereas Mcl‐1 knockdown had no noticeable effect on HIF‐1α expression. Thus, although both of these proteins were shown to be anti‐apoptotic, the action of HIF‐1α appeared to be mediated in part via Mcl‐1. J. Cell. Biochem. 97: 755–765, 2006. © 2005 Wiley‐Liss, Inc.
Internet‐based robotic laser scissors and tweezers microscopy
Authors: Botvinick Elliot L. , Berns Michael W.
Published: October 2005

We have engineered a robotic laser ablation and tweezers microscope that can be operated via the internet using most internet accessible devices, including laptops, desktop computers, and personal data assistants (PDAs). The system affords individual investigators the ability to conduct micromanipulation experiments (cell surgery or trapping) from remote locations (i.e., between the US and Australia). This system greatly expands the availability of complex and expensive research technologies via investigator‐networking over the internet. It serves as a model for other “internet‐friendly” technologies leading to large scale networking and data‐sharing between investigators, groups, and institutions on a global scale. The system offers three unique features: (1) the freedom to operate the system from any internet‐capable computer, (2) the ability to image, ablate, and/or trap cells and their organelles by “remote‐control,” and (3) the security and convenience of controlling the system in the laboratory on the user's own personal computer and not on the host machine. Four “proof of principle” experiments were conducted: (1) precise control of microscope movement and live cell visualization, (2) subcellular microsurgery on the microtubule organizing center of live cells viewed under phase contrast and fluorescence microscopy, (3) precise targeting of multiple sites within single red blood cells, and (4) optical trapping of 10 μm diameter polystyrene microspheres. Microsc. Res. Tech. 68:65–74, 2005. © 2005 Wiley‐Liss, Inc.
A novel technique for flat‐embedding cryofixed plant specimens in LR white resin
Authors: Palmieri Maria , Kiss John Z.
Published: October 2005

Acrylic LR White is used preferentially for many research applications because it possesses unique advantages over other commercially available resin types. LR White has low toxicity; its low viscosity and hydrophilic properties enable it to infiltrate specimens with comparative ease, and specimens embedded in LR White take up stains for light microscopy well and tend to retain superior antigenicity relative to other resins. These qualities make LR White a good choice for immunohistochemistry, light microscopy, and transmission electron microscopy. However, LR White does not heat‐polymerize in the presence of oxygen, which precludes its use with many commercially available embedding molds. Furthermore, flat‐embedding specimens in LR White is often an arduous task. Therefore, in this paper, we report on the development of novel flat‐embedding chambers for use with LR White. Another goal of our studies was the rapid fixation of larger specimens. Chemical fixation was inadequate because of the time required for tissue infiltration, but cryofixation quickly and effectively immobilized intracellular organelles. Mean amyloplast positions differed in vertically oriented versus control specimens after chemical fixation, whereas no significant difference was observed after cryofixation. Furthermore, cryofixation provided acceptable preservation at the light microscopy level, even though our specimens were relatively larger. This underscores the utility of cryofixation for light microscopy determination of organelle positioning within plant cells. Microsc. Res. Tech. 68:80–84, 2005. © 2005 Wiley‐Liss, Inc.
Application of photoconversion technique for correlated confocal and ultrastructural studies in organotypic slice cultures
Authors: Nikonenko Irina , Boda Bernadett , Alberi Stefano , Muller Dominique
Published: October 2005

Photoconversion of fluorescent staining into stable diaminobenzidine (DAB) precipitate is widely used for neuroanatomical and developmental studies. An important advantage of the approach is to make correlations between light and electron microscopy analyses possible, the DAB reaction product formed during photoconversion being electron dense. By combining a photoconversion approach with biolistic transfection of neurons in organotypic hippocampal slice cultures, we describe here a methodology that allowed us to study at the electron microscopy level the fine details of cells expressing specific genes of interest. The same approach has also been used to analyze the ultrastructural characteristics of specific cells such as neurons recorded with patch clamp techniques. This approach revealed particularly useful for studies of dendritic arborisation, dendritic spines, and axon varicosities of identified cells, as precise morphometric parameters of these structures can only be obtained by electron microscopy. The techniques used for fluorescent staining and photoconversion of these different cell structures and the results obtained by electron microscopic analyses are described. Microsc. Res. Tech. 68:90–96, 2005. © 2005 Wiley‐Liss, Inc.
Reversible Photo‐Mechanical Switching Behavior of Azobenzene‐Containing Semi‐Interpenetrating Network under UV and Visible Light Irradiation
Authors: Kim Hyun‐Kyoung , Wang Xiao‐Shui , Fujita Yukihiro , Sudo Atsushi , Nishida Haruo , Fujii Masayuki , Endo Takeshi
Published: October 2005

Summary: Light‐induced reversible changes in elasticity of semi‐interpenetrating network (semi‐IPN) films bearing azobenzene moieties were achieved under both ultraviolet (UV) and visible light irradiation. The semi‐IPN film was prepared by a cationic copolymerization of azobenzene‐containing vinyl ethers in a linear polycarbonate (PC) film as a matrix. When the irradiation was switched on and off, the semi‐IPN film showed rapid reversible deformation with the same behavior occurring over a range of wavelengths, including both the UV and visible regions. The observed reversible deformation of the film was attributed to the decrease in the film's elasticity, which was assumed to be caused by the frequent trans‐cis cycling isomerization of azobenzene moieties taking place during the UV and visible light irradiation. This cycling makes it difficult for the azobenzene groups to aggregate, thus hindering their ability to function as pseudo‐crosslinking points.

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Robust Poly(allylamine)‐graft‐poly(N‐isopropylacrylamide) Particles Prepared by Physical Crosslinking with Poly(styrene sulfonate)
Authors: Chen Bo , Gao Changyou
Published: October 2005

Summary: Robust thermosensitive PAH‐g‐PNIPAAm/PSS particles were prepared by addition of a poly(allylamine)‐graft‐poly(N‐isopropylacrylamide) particle suspension into poly(styrene sulfonate) solution above the LCST of PAH‐g‐PNIPAAm. Scanning force microscopy revealed stable and well‐separated particles in water at room temperature. The zeta‐potential showed a negative surface charge of the particles. Their thermosensitive behavior was demonstrated by dynamic light scattering. The release of rhodamine 6G loaded particles could respond to the incubation temperature.

Fabrication of thermosensitive and robust particle by suspension of in situ formed PAH‐g‐PNIPAAm particle above the LCST in PSS solution.

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Fabrication of thermosensitive and robust particle by suspension of in situ formed PAH‐g‐PNIPAAm particle above the LCST in PSS solution.
Effect of amantadine in essential tremor: A randomized, placebo‐controlled trial
Authors: Gironell Alexandre , Kulisevsky Jaime , Pascual‐Sedano Berta , Flamarich David
Published: October 2005

There is a need for new medication for essential tremor (ET). Preliminary evidence suggests that amantadine may be effective in the treatment of ET. We studied the effects of amantadine in a double‐blind, cross‐over, placebo‐controlled trial in ET patients. Sixteen patients with ET received amantadine 100 mg b.i.d. and placebo for 15 days, with a 1‐week wash‐out period between treatments. Major evaluation outcomes consisted of a tremor clinical rating scale, accelerometric recordings, and a self‐reported disability scale obtained before drug intake and on study days 1 and 15 of each treatment period. A two‐way repeated measures analysis of variance (treatment, time) was applied. Any P value < 0.05 was considered significant. On day 15, amantadine did not demonstrate any significant efficacy in reducing tremor with respect to baseline in any tremor measures. An increase in postural tremor as an adverse effect of amantadine was referred by 37.5% of patients. Results from the present trial indicate amantadine at 100 mg b.i.d. is not effective as a treatment for ET. © 2005 Movement Disorder Society
Long‐term benefits of rivastigmine in dementia associated with Parkinson's disease: An active treatment extension study
Authors: Poewe Werner , Wolters Erik , Emre Murat , Onofrj Marco , Hsu Chuanchieh , Tekin Sibel , Lane Roger
Published: October 2005

In patients with dementia associated with Parkinson's disease (PD), the efficacy and safety of rivastigmine, an inhibitor of acetylcholinesterase and butyrylcholinesterase, were previously demonstrated in a 24‐week double‐blind placebo‐controlled trial. Our objective was to determine whether benefits were sustained over the long term. Following the double‐blind trial, all patients were permitted to enter an active treatment extension study, during which they received rivastigmine 3–12 mg/day. Standard safety assessments were performed. Efficacy assessments included the Alzheimer's Disease Assessment Scale cognitive subscale (ADAS‐cog) and other measures of cognition, daily function, neuropsychiatric symptoms, and executive function. Of 433 patients who completed the double‐blind trial, 334 entered and 273 completed the active treatment extension. At 48 weeks, the mean ADAS‐cog score for the whole group improved by 2 points above baseline. Placebo patients switching to rivastigmine for the active treatment extension experienced a mean cognitive improvement similar to that of the original rivastigmine group during the double‐blind trial. The adverse event profile was comparable to that seen in the double‐blind trial. Long‐term rivastigmine treatment appeared well tolerated and may provide sustained benefits in dementia associated with PD patients who remain on treatment for up to 48 weeks. © 2005 Movement Disorder Society
A two‐species plasma in the limit of large ion mass
Authors: Rein Gerhard
Published: October 2005

Classical solutions of the relativistic Vlasov–Maxwell system are considered, describing a collisionless plasma with two species of particles. ions and electrons. It is shown that as the ion mass m tends to infinity, the corresponding solution of the relativistic Vlasov–Maxwell system tends to the solution of a system, in which the ions are given by a fixed ion background and only the electrons move. The convergence is uniform on compact time intervals, with an asymptotic convergence rate of m−1.
On a contact problem for a system of parabolic equations in the thermal conductivity of electric machines: II
Authors: Małecki Romuald , Olszewski Paweł , Urbanowicz Jacek , Urbański Wojciech
Published: October 2005

The non‐linear contact problem for the parabolic system of second order in the sense of Pietrovski, which is the generalization of the problem considered in Part I (preceding paper), is formulated. The matrix of fundamental solutions for parabolic systems of second order with coefficients containing unknown functions and their first‐order derivatives is constructed and used to reduce the problem to the equivalent system of integral equations which is then reduced to a system of Volterra type of the second kind. The existence of the solution of the system obtained is proved by using the Schauder fixed‐point theorem.
The kinetics equations in a multiplying medium with free boundaries
Authors: Belleni‐Morante A. , Lauro G.
Published: October 2005

We study a mathematical model of neutron multiplication in a slab 𝒮, by taking into account temperature feedback effects and considering one group of delayed neutrons. The thickness 2a of 𝒮 is time dependent because of temperature variations due to the energy released by fissions.

Starting from a quite detailed picture of the physical phenomena occurring in 𝒮, we derive a system of three coupled ordinary differential equations for the total number of neutrons F̂ = F̂(t), for the total number of precursors Ĉ = Ĉ(t), and for the half‐thickness of 𝒮, a = a(t).

We finally examine some stability properties of such a system of ordinary differential equations.
Modelling of dynamic networks of thin thermoelastic beams
Authors: Lagnese J. E. , Leugering G. , Schmidt E. J. P. G.
Published: October 2005

We derive a distributed‐parameter model of a thin non‐linear thermoelastic beam in three dimensions. The beam can also be initially curved and twisted. Our main task is to formulate the non‐homogeneous initial, boundary and node value problem associated with the dynamics of a network of a finite number of such beams. The emphasis here is on a distributed‐parameter modelling of the geometric and kinematic node conditions. The forces and couples appearing in the boundary and node conditions can then be viewed as control variables. The analysis of the resulting control systems and their controllability and stabilizability properties is the subject of [25] and of forthcoming papers.