bluuebunny/crossref_metadata_2025_split huggingface dataset:
New super‐orthogonal space‐time trellis codes with 32QAM and two transmit antennas for five bits per signalling interval
Authors: Sterian Corneliu Eugen D. , Linga Srujan , Singh Harvinder , Pätzold Matthias 
Published: June 2006

AbstractIn this paper, we focus on the design of super‐orthogonal space‐time (ST) trellis codes with a 32‐point quadrature amplitude modulation (QAM) signal constellation, allowing wireless communication with a data rate of 5 bits per signalling interval. Considering a mobile wireless communications system with two transmit antennas, we form a four‐dimensional (4D) signal constellation as a Cartesian product of two 2D rectangular signal sets. The first antenna transmits a 4D point as two concatenated 2D points in two consecutive baud intervals. The 2D symbols transmitted by the second antenna are not independent, but so chosen as to form, together with the symbols transmitted by the first antenna, the entries of a 2 × 2 orthogonal matrix. For a rectangular constellation, as much as four sets of 2 × 2 orthogonal matrices can be built. To obtain a higher data rate, the union of two of them is used to construct a super‐orthogonal signal set. With 2 × 2 orthogonal matrices, we then label the state transitions of a trellis diagram describing the operation of the encoder. For the performance analysis, two different channel models are employed. The first channel model is based on the assumption that the paths between different pairs of transmit–receive antennas are uncorrelated, while the second model takes into account the effect of spatial antenna correlation at both the base station (BS) and at the mobile station (MS). The analysis of the frame‐error rate (FER) and the bit‐error rate (BER) demonstrates the excellent performance of the proposed high data rate super‐orthogonal ST trellis code. Copyright © 2006 AEIT.
Finite volume adaptive solutions using SIMPLE as smoother
Authors: Syrakos Alexandros , Goulas Apostolos 
Published: June 2006

AbstractThis paper describes a new multilevel procedure that can solve the discrete Navier–Stokes system arising from finite volume discretizations on composite grids, which may consist of more than one level. SIMPLE is used and tested as the smoother, but the multilevel procedure is such that it does not exclude the use of other smoothers. Local refinement is guided by a criterion based on an estimate of the truncation error. The numerical experiments presented test not only the behaviour of the multilevel algebraic solver, but also the efficiency of local refinement based on this particular criterion. Copyright © 2006 John Wiley & Sons, Ltd.
A new modification of the immersed‐boundary method for simulating flows with complex moving boundaries
Authors: Deng Jian , Shao Xue‐Ming , Ren An‐Lu 
Published: June 2006

AbstractIn this paper, a new immersed‐boundary method for simulating flows over complex immersed, moving boundaries is presented. The flow is computed on a fixed Cartesian mesh and the solid boundaries are allowed to move freely through the mesh. The present method is based on a finite‐difference approach on a staggered mesh together with a fractional‐step method. It must be noted that the immersed boundary is generally not coincident with the position of the solution variables on the grid, therefore, an appropriate strategy is needed to construct a relationship between the curved boundary and the grid points nearby. Furthermore, a momentum forcing is added on the body boundaries and also inside the body to satisfy the no‐slip boundary condition. The immersed boundary is represented by a series of interfacial markers, and the markers are also used as Lagrangian forcing points. A linear interpolation is then used to scale the Lagrangian forcing from the interfacial markers to the corresponding grid points nearby. This treatment of the immersed‐boundary is used to simulate several problems, which have been validated with previous experimental results in the open literature, verifying the accuracy of the present method. Copyright © 2006 John Wiley & Sons, Ltd.
Tracking accuracy of a semi‐Lagrangian method for advection–dispersion modelling in rivers
Authors: Néelz S. , Wallis S. G. 
Published: June 2006

AbstractThere is an increasing need to improve the computational efficiency of river water quality models because: (1) Monte‐Carlo‐type multi‐simulation methods, that return solutions with statistical distributions or confidence intervals, are becoming the norm, and (2) the systems modelled are increasingly large and complex. So far, most models are based on Eulerian numerical schemes for advection, but these do not meet the requirement of efficiency, being restricted to Courant numbers below unity. The alternative of using semi‐Lagrangian methods, consisting of modelling advection by the method of characteristics, is free from any inherent Courant number restriction. However, it is subject to errors of tracking that result in potential phase errors in the solutions. The aim of this article is primarily to understand and estimate these tracking errors, assuming the use of a cell‐based backward method of characteristics, and considering conditions that would prevail in practical applications in rivers. This is achieved separately for non‐uniform flows and unsteady flows, either via theoretical considerations or using numerical experiments. The main conclusion is that, tracking errors are expected to be negligible in practical applications in both unsteady flows and non‐uniform flows. Also, a very significant computational time saving compared to Eulerian schemes is achievable. Copyright © 2006 John Wiley & Sons, Ltd.
A combined pFFT‐multipole tree code, unsteady panel method with vortex particle wakes
Authors: Willis David J. , Peraire Jaime , White Jacob K. 
Published: June 2006

AbstractPotential flow solvers for 3‐D aerodynamic flows are commonly used in industrial applications. Two main difficulties preventing the even more widespread use of these codes are the limitations on the number of discretization elements and the user expertise and effort required to specify the wake location. In the paper we present an automatic wake generation strategy for a potential flow solver, and accelerate the method using a pFFT‐Fast Multipole Tree algorithm. The combined method can be used to simulate both steady and unsteady flows. The steady state solution is achieved by running an unsteady flow simulation until it reaches a steady state. Computation results are given to demonstrate that the method is fast enough to automatically simulate entire heaving and flapping wing crafts in under and hour on a desktop computer. Copyright © 2006 John Wiley & Sons, Ltd.
An eigenvector‐based linear reconstruction scheme for the shallow‐water equations on two‐dimensional unstructured meshes
Authors: Frazão Sandra Soares , Guinot Vincent 
Published: June 2006

AbstractThis paper presents a new approach to MUSCL reconstruction for solving the shallow‐water equations on two‐dimensional unstructured meshes. The approach takes advantage of the particular structure of the shallow‐water equations. Indeed, their hyperbolic nature allows the flow variables to be expressed as a linear combination of the eigenvectors of the system. The particularity of the shallow‐water equations is that the coefficients of this combination only depend upon the water depth. Reconstructing only the water depth with second‐order accuracy and using only a first‐order reconstruction for the flow velocity proves to be as accurate as the classical MUSCL approach. The method also appears to be more robust in cases with very strong depth gradients such as the propagation of a wave on a dry bed. Since only one reconstruction is needed (against three reconstructions in the MUSCL approach) the EVR method is shown to be 1.4–5 times as fast as the classical MUSCL scheme, depending on the computational application. Copyright © 2006 John Wiley & Sons, Ltd.
Application of Chimera grid to modelling cell motion and aggregation in a narrow tube
Authors: Chung B. , Johnson P. C. , Popel A. S. 
Published: June 2006

AbstractA computational scheme using the Chimera grid method is presented for simulation of three‐dimensional motion and aggregation of two red blood cells (RBCs) in a narrow tube. The cells are modelled as rigid ellipsoidal particles; the computational scheme is applicable to deformable fluid‐filled particles. Attractive energy between two RBCs is modelled by a depletion interaction theory and used for simulating aggregation of two cells. Through the simulation, we show that the Chimera grid method is applicable to the simulation of three‐dimensional motion and aggregation of multiple RBCs in a microvessel and microvascular network. Copyright © 2006 John Wiley & Sons, Ltd.
Compressible flow equations based on moving coordinates determined by the wave speed
Authors: Chen Zheng , Gao Bo , Wu Zi‐Niu 
Published: June 2006

AbstractIn this paper, we consider moving coordinates with a speed determined by the wave speed. This allows us to move the coordinates at the speed of contact discontinuities, expansion fans, or other wave structures. While recognizing that the Lagrangian coordinates, which can well resolve the sliplines, behave badly for expansion waves, we demonstrate that a coordinate system moving at the characteristic speed of the expansion fan behaves much better for expansion waves. Moreover, the new coordinate system allows one to well capture the shock wave, the slipline and the expansion waves at the same time. Copyright © 2006 John Wiley & Sons, Ltd.
Lattice Boltzmann‐based single‐phase method for free surface tracking of droplet motions
Authors: Xing Xiu Qing , Butler David Lee , Yang Chun 
Published: June 2006

AbstractA 2D single‐phase free surface tracking model, based on the lattice Boltzmann method (LBM) is developed for simulating droplet motion. In contrast to the conventional multi‐phase models, it is not necessary to simulate the motion of the gas phase using this 2D single‐phase algorithm, and thus improves the computational efficiency without sacrificing the underlying physics. A method for special treatment of the relevant boundary conditions in the single‐phase algorithm is proposed and also validated. Numerical simulations are carried out for the motion of a free falling droplet with or without considering gravity and droplet spreading under gravity. The simulations of the LBM are found to be consistent with the results obtained from commercial computational fluid dynamics (CFD) software Fluent. Copyright © 2006 John Wiley & Sons, Ltd.
Antibiotic prophylaxis in chemotherapy‐induced neutropenia: time to reconsider
Authors: Lo Nangi , Cullen Michael 
Published: June 2006

AbstractThe use of antibiotic prophylaxis in neutropenic patients remains controversial. The main arguments against prophylaxis are the lack of survival benefit and the risk of inducing antibiotic resistance. At present, clinical guidelines advise against routine use of antibiotic prophylaxis and current practice is to commence broad‐spectrum antibiotics at the onset of fever in the neutropenic patient. However hospitalization, investigations and treatment all impact on resources as well as affecting patient quality of life, often resulting in chemotherapy delays and dose reductions. The benefits of prophylactic antibiotics have been emphasized by two major double‐blind, placebo controlled trials with levofloxacin with very significant reductions in all infection‐related events. Furthermore, the meta‐analysis confirms a survival advantage and this is greatest with the use of fluoroquinolones. These benefits must be weighed against the problem of emerging antibiotic resistance. It has been shown that antibiotic prophylaxis does induce resistant organisms, but some studies have shown that the impact on clinical outcomes may not be as great as expected. Current evidence supports antibiotic prophylaxis with fluoroquinolones in acute leukaemia and high‐dose chemotherapy patients, commencing at the same time as chemotherapy. Febrile episodes are much commoner with the first cycle in patients with solid tumours or lymphoma having moderately myelosuppressive chemotherapy, and these patients should be offered prophylaxis for at least the first cycle of chemotherapy. Further work is ongoing to facilitate the selection of patients with the greatest chance of benefit so that prophylaxis can be used efficiently. Copyright © 2006 John Wiley & Sons, Ltd.
Theoretical, spectroscopic, and mechanistic studies on transition‐metal dinitrogen complexes: Implications to reactivity and relevance to the nitrogenase problem
Authors: Studt Felix , Tuczek Felix 
Published: June 2006

AbstractDinitrogen complexes of transition metals exhibit different binding geometries of N2 (end‐on terminal, end‐on bridging, side‐on bridging, side‐on end‐on bridging), which are investigated by spectroscopy and DFT calculations, analyzing their electronic structure and reactivity. For comparison, a bis(μ‐nitrido) complex, where the NN bond has been split, has been studied as well. Most of these systems are highly covalent, and have strong metal–nitrogen bonds. In the present review, particular emphasis is put on a consideration of the activation of the coordinated dinitrogen ligand, making it susceptible to protonation, reactions with electrophiles or cleavage. In this context, theoretical, structural, and spectroscopic data giving informations on the amount of charge on the N2 unit are presented. The orbital interactions leading to a charge transfer from the metals to the dinitrogen ligand and the charge distribution within the coordinated N2 group are analyzed. Correlations between the binding mode and the observed reactivity of N2 are discussed. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1278–1291, 2006
Whole‐body T1 mapping improves the definition of adipose tissue: Consequences for automated image analysis
Authors: Kullberg Joel , Angelhed Jan‐Erik , Lönn Lars , Brandberg John , Ahlström Håkan , Frimmel Hans , Johansson Lars 
Published: June 2006

AbstractPurposeTo determine whether a whole‐body T1‐mapping acquisition method improves the definition of adipose tissue (AT) and simplifies automated AT segmentation compared to an image‐based method.Materials and MethodsThe study included 10 subjects. Two whole‐body volumes were acquired from each subject using two different flip angles. Whole‐body T1 maps were calculated from each pair of whole‐body volumes. AT was automatically segmented from the T1 maps and from the original image slices. The results were evaluated using manually segmented slices as reference.ResultsThe T1‐mapping method segmented more of the reference AT than the image‐based method, with mean values (standard deviations (SDs)) of 87.7(5.1)% and 81.1(5.2)%, respectively. Compared to the image‐based method, the T1‐mapping method gives better histogram separation of AT in whole‐body volumes. The suggested method also provides an output with smaller in‐slice AT intensity variations.ConclusionThe T1‐mapping method improves the definition of AT. T1‐based analysis is superior to analysis based on the original images, and allows fully automated and accurate whole‐body AT segmentation. J. Magn. Reson. Imaging 2006. © 2006 Wiley‐Liss, Inc.
Study on the toxic mechanism of prion protein peptide 106–126 in neuronal and non neuronal cells
Authors: Dupiereux Ingrid , Zorzi Willy , Rachidi Walid , Zorzi Danièle , Pierard Olivier , Lhereux Bernard , Heinen Ernst , Elmoualij Benaïssa 
Published: June 2006

AbstractA synthetic peptide corresponding to the 106–126 amyloidogenic region of the cellular human prion protein (PrPc) is useful for in vitro study of prion‐induced neuronal cell death. The aim of the present work was to examine the implication of the cellular prion protein in the toxicity mechanism induced by PrP 106–126. The effect of PrP 106–126 was investigated both on human neuroblastoma SH‐SY5Y cells and on SH‐SY5Y overexpressing murine cellular prions (wtPrP). We show by metabolic assay tests and ATP assays that PrPc expression does not modulate the toxicity of the prion peptide. Moreover, we investigated the effect of this peptide on an established non neuronal model, rabbit kidney epithelial A74 cells that express a doxycycline‐inducible murine PrPc gene. We show for the first time that the prion peptide 106–126 does not exert any toxic effect on this cell line in the presence or absence of doxycycline. Our results show that the PrP 106–126‐induced cell alteration is independent of PrPc expression. Rather, it seems to act via an interaction with lipidic components of the plasma membrane as strengthened by our results showing the differential susceptibility of neuronal and non neuronal cell lines that significantly differ by their membrane fatty acid composition. © 2006 Wiley‐Liss, Inc.
Sugar and acid concentrations in 98 grape cultivars analyzed by principal component analysis
Authors: Liu Huai‐Feng , Wu Ben‐Hong , Fan Pei‐Ge , Li Shao‐Hua , Li Lian‐Sheng 
Published: June 2006

AbstractA total of 98 grape cultivars were studied for content and composition of organic acids and sugars in grape juice during two consecutive years. Glucose and fructose were the predominant sugars in grape berries and ranged from 45.86 to 122.89 mg mL−1, and 47.64 to 131.04 mg mL−1, respectively, in two years. Sucrose was present at trace amounts in most cultivars, but two cultivars of hybrids between Vitis labrusca and V. vinifera contained large amounts of sucrose. Tartaric acid content in berries, varying from 1.57 to 9.09 and 1.54 to 9.05 mg mL−1, respectively, in two years, was significantly higher than malic acid, which ranged from 0.38 to 6.05 and 0.36 to 7.06 mg mL−1, respectively, in two years. Moreover, significantly higher total soluble sugars and fructose and lower total acids and malic acid were found in cultivars from hybrids between V. labrusca and V. vinifera than those in V. vinifera cultivars, and wine grapes had higher total sugars and acids than table grapes from V. vinifera. Principal component analysis (PCA) indicated that genotypic correlations among sugar and acid contents were stable and the first three PCs accounted for about 82% of total variance in both years. PC1 was highly connected with glucose and fructose contents, and sucrose was an important contributor to the variance for PC2, as well as for PC3. PC2 and PC3 were highly connected also with organic acids, but the contributor to variance differed from one year to the next. Tartaric acid was the main contributor to variance in 2003, and malic acid was important in 2004 for PC2 and PC3. In a scatter plot of the score values of all genotypes projected to the PC1 and PC2 plane, three groups of cultivars tend to cluster based on their genetic background or purpose of use. The cultivars of hybrid V. labrusca and V. vinifera were represented by high sugars, especially sucrose, and low acids. Among the cultivars of V. vinifera, wine grapes were found in general to have more sugars and acids than table grapes. The composition of sugars was stable in grape berries between the two years, while acids were sensitive to climate changes. Finally, the different responses of malic and tartaric acids to climate change is discussed. Copyright © 2006 Society of Chemical Industry
Effect of drying conditions on bioactive compounds and antioxidant activity of broccoli (Brassica oleracea L.)
Authors: Mrkìc Vlatka , Cocci Emiliano , Rosa Marco Dalla , Sacchetti Giampiero 
Published: June 2006

AbstractThe effect of air‐drying parameters on antioxidant activity and changes in antioxidant compounds of broccoli (Brassica oleracea L.) were studied. Broccoli samples were dried to 70 g kg−1 moisture content using temperatures ranging from 50 to 100 °C and air flow‐rates from 1.20 to 2.25 m s−1, resulting in drying times from 25 to 90 min. Temperature, owing to its positive effect on the oxidation kinetics, was negatively correlated with ascorbic acid and free and total polyphenol contents but not with kaempferol, even though the sample dried at the highest temperature showed the lowest kaempferol content. The air flow‐rate was positively correlated with the total (TPP) and free (FPP) polyphenol contents because it led to a reduction in the drying time. No correlation was found between air flow‐rate and kaempferol content. Air flow‐rate and temperature positively affected the antioxidant activity by reducing the drying time. High‐temperature, short‐time processes maximised the antioxidant activity of broccoli owing to the negative effect of drying time on antioxidant activity. The antioxidant activity of broccoli was positively and significantly correlated with the FPP content but not with TPP and kaempferol. The evaluation of hydroxymethylfurfural content as an indicator of the occurrence of a Maillard reaction in dried broccoli did not support the hypothesis of a contribution of MRPs to the antioxidant activity of dried broccoli. Copyright © 2006 Society of Chemical Industry
Discrete duality finite volume schemes for Leray−Lions−type elliptic problems on general 2D meshes
Authors: Andreianov Boris , Boyer Franck , Hubert Florence 
Published: June 2006

AbstractDiscrete duality finite volume schemes on general meshes, introduced by Hermeline and Domelevo and Omnès for the Laplace equation, are proposed for nonlinear diffusion problems in 2D with nonhomogeneous Dirichlet boundary condition. This approach allows the discretization of non linear fluxes in such a way that the discrete operator inherits the key properties of the continuous one. Furthermore, it is well adapted to very general meshes including the case of nonconformal locally refined meshes. We show that the approximate solution exists and is unique, which is not obvious since the scheme is nonlinear. We prove that, for general W−1,p′(Ω) source term and W1‐(1/p),p(∂Ω) boundary data, the approximate solution and its discrete gradient converge strongly towards the exact solution and its gradient, respectively, in appropriate Lebesgue spaces. Finally, error estimates are given in the case where the solution is assumed to be in W2,p(Ω). Numerical examples are given, including those on locally refined meshes. © 2006 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007