bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of experimental removal of large woody debris on spatial patterns of three‐dimensional flow in a meander bend
Authors: Daniels Melinda D. , Rhoads Bruce L. 
Published: August 2006

AbstractThis study reports the results of a large woody debris (LWD) removal experiment in a meander bend along a low‐energy stream in the Midwestern United States. The LWD obstacle was located in the center of the channel at the bend exit and consisted of a mature tree with an intact soil‐covered root wad and a large accumulation of logs, branches and pieces of lumber on top of and adjacent to the main tree. The results indicate that the LWD obstruction influenced 3D flow structure in this bend at all flow stages. The main effect of LWD is to dramatically decelerate flow throughout the majority of the bend, while locally accelerating flow where it passes through the narrow chute at the downstream end of the LWD obstruction. Results from the LWD removal experiment indicate that patterns of three‐dimensional flow structure in meander bends are sensitive to complete removal of LWD. After the removal of LWD from the bend, both downstream and secondary velocities increased and, though still weak, secondary flow intensified. Large, relatively stable, obstructions that span a significant portion of the channel may act as natural dams, effectively ponding water upstream of the LWD, thereby producing substantial convective deceleration of the flow. This research is the first to document three‐dimensional flow structure before and after a controlled removal of LWD from a meander bend. Studies of the type reported here represent a first step toward determining the ensemble of process interactions between LWD and bend dynamics. Copyright © 2006 John Wiley & Sons, Ltd.
A Sulfophenylated Polysulfone as the DMFC Electrolyte Membrane – an Evaluation of Methanol Permeability and Cell Performance
Authors: Vernersson T. , Lafitte B. , Lindbergh G. , Jannasch P. 
Published: August 2006

AbstractA sulfophenylated polysulfone (PSU‐sph), carrying 0.8 sulfonic acid units per repeating unit of the polymer, is evaluated as a membrane electrolyte for DMFC applications. The liquid uptake, methanol transport characteristics, electrolyte conductivity, and fuel cell performance are investigated. The methanol transport and DMFC performance results are compared to those of Nafion® 117. The PSU‐sph membrane investigated shows superior qualities with regard to methanol crossover, with a methanol permeability of approximately 25% compared to that of Nafion®. The conductivity was measured to be 15% compared to that of Nafion®. However, this could not fully account for the internal resistance of the cell, implying that the contact resistance between the electrodes and electrolyte is higher when PSU‐sph is used, probably because the electrodes are developed for use with Nafion® membranes. The stability of the PSU‐sph membrane seems promising, with very low degradation observed over a period of 72 hours. It was concluded that although the mass transport properties of the PSU‐sph membrane sample investigated were superior, it could not match the performance of Nafion® 117 in a DMFC application. However, a higher degree of sulfonation may have a significant positive effect on cell performance. The results also showed that a fully intergrated MEA is needed to fully assess new menbrane materials.
Start Up and Freezing Processes in PEM Fuel Cells
Authors: Oszcipok M. , Hakenjos A. , Riemann D. , Hebling C. 
Published: August 2006

AbstractThe isothermal operation of single PEM fuel cells below 0 °C is investigated by potentiostatic experiments and analyzed by physical modeling. Current decay is observed during potentiostatic operation, which is caused by the freezing of product water in the porous cathode layers.This paper describes the implementation of the ohmic losses and changes of the active cathode area as a function of the charge transfer density in a physical PEM fuel cell model. The model is comprised of a set of differential equations accounting for the electrochemical reaction and diffusion processes in the cathode of the fuel cell.The model describes the time‐resolved current decay during freezing. Thus a better understanding of freezing processes at sub‐zero conditions in PEM fuel cells is gained and mechanisms proposed from earlier experimental data and statistical based interpretations are confirmed. Furthermore, the transient water uptake behavior of the membrane is studied in situ at different temperatures.
The rise of ginkgoalean plants in the early Mesozoic: a data analysis
Authors: Zhiyan Zhou , Xiangwu Wu 
Published: August 2006

AbstractIn the present article, ginkgoalean fossil records are analysed and the data are incorporated into a sketched, ‘epoch‐by‐epoch’ framework (e.g. late Triassic, early Jurassic), based on the latest biostratigraphical evidence and the recent progress made mainly on the reproductive organs. The analyses revealed that a steep increase in diversity occurred from the middle Triassic onwards and during the late Triassic ginkgoaleans were at the zenith of diversity. In the late Triassic, almost all known ginkgoalean families simultaneously occurred. The diversity of vegetative organs increased rapidly, forming a high peak in the number of genera (8 in China and 12 in the world). In the late Triassic, in marked contrast to the absence of any record in the middle Triassic, there occurred the most diversified ginkgoalean reproductive structures so far known in the geological record. The emergence of a large number of new genera also supports an early Mesozoic, notably a late Triassic radiation of ginkgoaleans. In China, Ginkgo was recorded firstly in the late Triassic, and the commonest morphogenera Ginkgoites, Baiera and Sphenobaiera drastically increased in specific (or morphotypic) diversity from the late Triassic onwards accompanied by very high origination rates of 88.8, 100 and 91.7%, respectively. The major morphological innovations of vegetative organs accomplished in the middle to late Triassic are the appearance of dwarf shoots and the differentiation of leaves into lamina and petiole. Since then, the reduction of pedicels and number of ovules, and the increase in size of ovules became dominant. Further morphological innovations and diversification of ginkgoalean ovule organs include the fused or adnate ovule/bract, and the collared or winged ovules. In China, ginkgoaleans also started expanding rapidly in geographical distribution from the middle Triassic to the late Triassic. The fossil localities of Ginkgo increased from zero to three, Ginkgoites from one to 12, Baiera zero to 27 and Sphenobaiera three to 20 counties.The replacement of the warm‐hot, nearly uniform climate with long growing season in the late Palaeozoic by the seasonal climate in the early Mesozoic of Eurasia was probably the main cause of a marked reduction of both vegetative and reproductive organs of ginkgoaleans. The latest Triassic plate movement and sea‐level change that resulted in considerable habitat heterogeneity might also facilitate an increase in taxon and morphology diversity of this present‐day relictual plant group. Copyright © 2006 John Wiley & Sons, Ltd.
Analysis of immunoglobulin heavy and light chain variable genes in post‐transplant lymphoproliferative disorders
Authors: Capello Daniela , Cerri Michaela , Muti Giuliana , Lucioni Marco , Oreste Pierluigi , Gloghini Annunziata , Berra Eva , Deambrogi Clara , Franceschetti Silvia , Rossi Davide , Alabiso Oscar , Morra Enrica , Rambaldi Alessandro , Carbone Antonino , Paulli Marco , Gaidano Gianluca 
Published: August 2006

AbstractPost‐transplant lymphoproliferative disorders (PTLD) derive from antigen‐experienced B‐cells and represent a major complication of solid organ transplantation. We characterized usage, mutation frequency and mutation pattern of immunoglobulin variable (IGV) gene rearrangements in 50 PTLD (polymorphic PTLD, n=10; diffuse large B‐cell lymphoma, n=35; and Burkitt/Burkitt‐like lymphoma, n=5). Among PTLD yielding clonal IGV amplimers, a functional IGV heavy chain (IGHV) rearrangement was found in 40/50 (80.0%) cases, whereas a potentially functional IGV light chain rearrangement was identified in 36/46 (78.3%) PTLD. By combining IGHV and IGV light chain rearrangements, 10/50 (20.0%) PTLD carried crippling mutations, precluding expression of a functional B‐cell receptor (BCR). Immunohistochemistry showed detectable expression of IG light chains in only 18/43 (41.9%) PTLD. Failure to detect a functional IGV rearrangement associated with lack of IGV expression. Our data suggest that a large fraction of PTLD arise from germinal centre (GC)‐experienced B‐cells that display impaired BCR. Since a functional BCR is required for normal B‐cell survival during GC transit, PTLD development may implicate rescue from apoptosis and expansion of B‐cells that have failed the GC reaction. The high frequency of IGV loci inactivation appears to be a peculiar feature of PTLD among immunodeficiency‐associated lymphoproliferations. Copyright © 2006 John Wiley & Sons, Ltd.
Quantum mechanical calculation of the effects of stiff and rigid constraints in the conformational equilibrium of the alanine dipeptide
Authors: Echenique Pablo , Calvo Iván , Alonso J. L. 
Published: August 2006

AbstractIf constraints are imposed on a macromolecule, two inequivalent classical models may be used: the stiff and the rigid one. This work studies the effects of such constraints on the conformational equilibrium distribution (CED) of the model dipeptide HCO‐L‐Ala‐NH2without any simplifying assumption. We use ab initio quantum mechanics calculations including electron correlation at the MP2 level to describe the system, and we measure the conformational dependence of all the correcting terms to the naive CED based in the potential energy surface that appear when the constraints are considered. These terms are related to mass‐metric tensors determinants and also occur in the Fixman's compensating potential. We show that some of the corrections are non‐negligible if one is interested in the whole Ramachandran space. On the other hand, if only the energetically lower region, containing the principal secondary structure elements, is assumed to be relevant, then, all correcting terms may be neglected up to peptides of considerable length. This is the first time, as far as we know, that the analysis of the conformational dependence of these correcting terms is performed in a relevant biomolecule with a realistic potential energy function. © 2006 Wiley Periodicals, Inc. J Comput Chem, 2006
Flooding in GROMACS: Accelerated barrier crossings in molecular dynamics
Authors: Lange Oliver F. , Schäfer Lars V. , Grubmüller Helmut 
Published: August 2006

AbstractThe major bottleneck of today's atomistic molecular dynamics (MD) simulations is that because of the enormous computational effort involved, only processes at nanoseconds to microseconds time scales or faster can be studied directly. Unfortunately, apart from a few exceptions, relevant processes, such as chemical reactions or many large scale conformational transitions in proteins, occur at slower time scales and therefore are currently far out of reach for conventional MD. The flooding technique addresses this problem by inclusion of a flooding potential into the force field. This flooding potential locally destabilizes the educt state and thereby significantly accelerates the escape from the initial energy well without affecting the reaction pathway. Here, we summarize the theory and method for the computational chemistry community and detail the implementation within the official version 3.3 of the freely available MD program package GROMACS. Two examples shall demonstrate the application of flooding to accelerate conformational transitions and chemical reactions. The second example was carried out within a QM/MM framework. © 2006 Wiley Periodicals, Inc. J Comput Chem, 2006
Second derivatives in generalized Born theory
Authors: Brown Russell A. , Case David A. 
Published: August 2006

AbstractGeneralized Born solvation models offer a popular method of including electrostatic aspects of solvation free energies within an analytical model that depends only upon atomic coordinates, charges, and dielectric radii. Here, we describe how second derivatives with respect to Cartesian coordinates can be computed in an efficient manner that can be distributed over multiple processors. This approach makes possible a variety of new methods of analysis for these implicit solvation models. We illustrate three of these methods here: the use of Newton‐Raphson optimization to obtain precise minima in solution; normal mode analysis to compute solvation effects on the mechanical properties of DNA; and the calculation of configurational entropies in the MM/GBSA model. An implementation of these ideas, using the Amber generalized Born model, is available in the nucleic acid builder (NAB) code, and we present examples for proteins with up to 45,000 atoms. The code has been implemented for parallel computers using both the OpenMP and MPI environments, and good parallel scaling is seen with as many as 144 OpenMP processing threads or MPI processing tasks. © 2006 Wiley Periodicals, Inc. J Comput Chem 2006
Lipid assessment and treatment patterns in hospitalized TIA and ischemic stroke patients
Authors: Ovbiagele Bruce , Hills Nancy K. , Saver Jeffrey L. , Johnston S. Claiborne ,   For the CASPR Investigators
Published: August 2006

AbstractBACKGROUNDIdentification of dyslipidemia and treatment with lipid‐lowering agents are established targets for quality performance during hospitalization for ischemic stroke and transient ischemic attack (TIA). We aimed to study the frequency and predictors of lipid assessment and discharge utilization of lipid‐lowering therapies among patients hospitalized for stroke and TIA.METHODSDemographics, clinical findings, and laboratory data were documented as part of the California Acute Stroke Prototype Registry (CASPR). Frequency of low‐density lipoprotein cholesterol (LDL‐C) testing and the frequency and appropriate use of lipid‐lowering treatment according to national cholesterol guidelines were determined. Multivariate models were generated to determine the contribution of clinical variables to LDL testing and prescription of lipid‐lowering medications at discharge.RESULTSData were collected on 764 consecutive patients with ischemic stroke or TIA treated at 11 hospitals over a 2‐year period. LDL‐C measurements were performed in only 50.1% during hospitalization. Measurement of LDL‐C was most strongly and independently associated with diagnosis of ischemic stroke (vs. TIA, P = .02) and history of dyslipidemia (P = .05). Overall, 48.4% of the CASPR cohort received lipid‐lowering medications at discharge. Independent predictors for being prescribed lipid‐lowering agents at discharge were diagnosis of ischemic stroke (P = .0009), LDL‐C testing (P = .0002), high risk of future coronary events according to national guidelines (P = .02), and history of dyslipidemia (P< .0001). Only 59% of patients at high risk for future coronary events were discharged on a lipid‐lowering medication.CONCLUSIONSSerum cholesterol testing and treatment are underutilized during hospitalization for ischemic stroke or TIA. Journal of Hospital Medicine 2006;1:214–220. © 2006 Society of Hospital Medicine.
Fatty acid composition, including isomeric profile of conjugated linoleic acid, and cholesterol in Mertolenga‐PDO beef
Authors: Alfaia Cristina MM , Quaresma Mário AG , Castro Matilde LF , Martins Susana IV , Portugal Ana PV , Fontes Carlos MGA , Bessa Rui JB , Prates José AM 
Published: August 2006

AbstractThis paper describes the fatty acid composition, including the isomeric distribution of conjugated linoleic acid (CLA), total lipids and cholesterol in longissimus dorsi (LD) and semitendinosus (ST) muscles of Mertolenga beef from young bulls reared according to Protected Designation of Origin (PDO) specifications. Mertolenga purebred young bulls (n = 30) were raised in a semi‐extensive production system, including a finishing period on concentrate feeds for the last 5 or 3 months (October and June samplings, respectively). Mertolenga‐PDO beef showed seasonal changes in the levels of some fatty acids (including the predominant 18:2n‐6), sums of trans fatty acids and n‐3 polyunsaturated fatty acids, some CLA isomers (t11,t13, t11,c13 and t10,c12), sums of geometric groups of CLA isomers and total cholesterol. In addition, significant differences were obtained between LD and ST muscles for most of the analysed parameters. From a nutritional perspective, beef‐PDO from June seems to be more healthful than that from October as a consequence of its lower n‐6/n‐3 ratio. Moreover, the results suggest that the polyunsaturated fatty acid/saturated fatty acid ratio in the ST muscle is consistently above the recommended guideline for human diets, although the values were below that guideline for the LD muscle. Taken together, the data indicate that, although the finishing period of Mertolengo young bulls on concentrate attenuates most of the beneficial grass effects on meat fat throughout the year, beef‐PDO from late spring is of greater nutritional value than that from early autumn. Copyright © 2006 Society of Chemical Industry
Photobleaching, light‐induced discolouration in red peppers
Authors: Jung Ji Won , Lee Seung Koo 
Published: August 2006

AbstractRed peppers dried in sunlight experience surface bleaching, centred near the calyx, on the face exposed to the light. In this study, bleaching mechanisms were studied under simulated irradiation conditions by placing pericarp discs in 2‐(N‐morpholino) ethane sulfonic acid (MES) and sucrose solution. The moisture content near the calyx of the pepper decreased more slowly than that on the apex side. In addition, pericarp discs incubated without MES/sucrose solution retained more carotenoids than those incubated with solution after 27 h of light treatment. Carotenoids in pericarp discs exposed to the light decreased rapidly over the incubation time, whereas in the dark they decreased slowly and remained higher in content. Changes in malondialdehyde (MDA) level and electrolyte leakage were not observed for pericarp incubation in the dark. A sharp increase in the level of MDA and a change in electrolyte leakage from discs exposed to the light occurred when carotenoids were exhausted. Carotenoid degradation was markedly suppressed by the addition of ascorbic acid. These results demonstrate that carotenoids in red pepper pericarp played a role in protecting cells and were subsequently degraded under intense light conditions. Copyright © 2006 Society of Chemical Industry
Opérateurs d'extension linéaires explicites dans des intersections de classes ultradifférentiables
Authors: Beaugendre Pascal 
Published: August 2006

AbstractB. S. Mityagin a montré que les polynômes de Tchebyshev forment une base de Schauder de l'espace des fonctions de classe C ∞ sur l'intervalle [–1,1]. Il en déduit un opérateur linéaire continu d'extension explicite. Ces résultats ont été étendus, par A. Goncharov, à des compacts ne satisfaisant pas la propriété de Markov. A contrario, M. Tidten a donné des exemples de compacts pour lesquels il n'y a pas d'opérateur linéaire continu d'extension. Dans cet article, on généralise ces travaux à des classes de fonctions ultradifférentiables construites sur le modèle de l'intersection des classes de Gevrey non quasi‐analytiques. On obtient notamment un théorème d'extension linéaire dans des classes de Beurling assez grandes. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Weakly Nehari functions, hyperbolic convexity and John disks
Authors: Chuaqui Martin , Herreros Pilar 
Published: August 2006

AbstractIn this paper, we extend some recent results by K. Hag and P. Hag regarding a generalized Nehari class. In particular, we give a description of this new class in terms of the hyperbolic metric, and characterize the unbounded functions in an analogue of a theorem of Gehring and Pommerenke. We also derive several sharp distortion theorems and estimates on the pre‐Schwarzian that are used to study John disks. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A connection between Schur multiplication and Fourier interpolation. II
Authors: McCloud N. , McEachin R. 
Published: August 2006

AbstractGiven m × n matrices A = [ajk ] and B = [bjk ], their Schur product is the m × n matrix A ○ B = [ajkbjk ]. For any matrix T, define ‖T‖ S = maxX ≠O ‖T ○ X ‖/‖X ‖ (where ‖·‖ denotes the usual matrix norm). For any complex (2n – 1)‐tuple μ = (μ –n +1, μ –n +2, …, μ n –1), let Tμ be the Hankel matrix [μ –n +j +k –1]j,k and define𝔅μ = {f ∈ L 1[–π, π] : f̂ (2j ) = μj for –n + 1 ≤ j ≤ n – 1} .It is known that ‖Tμ‖ S ≤ inf ‖f ‖1. When equality holds, we say Tμ is distinguished. Suppose now that μ j ∈ ℝ for all j and hence that Tμ is hermitian. Then there is a real n × n hermitian unitary X and a real unit vector y such that 〈(Tμ ○ X )y, y 〉 = ‖Tμ ‖S . We call such a pair a norming pair for Tμ . In this paper, we study norming pairs for real Hankel matrices. Specifically, we characterize the pairs that norm some distinguished Schur multiplier Tμ . We do this by giving necessary and suf.cient conditions for (X, y ) to be a norming pair in the n ‐dimensional case. We then consider the 2‐ and 3‐dimensional cases and obtain further results. These include a new and simpler proof that all real 2 × 2 Hankel matrices are distinguished, and the identi.cation of new classes of 3 × 3 distinguished matrices. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of set‐valued conditional expectation
Authors: Zohry M. 
Published: August 2006

AbstractFor an essentially bounded closed‐convex‐nonempty set‐valued random variable, it is shown that the conditional expectation is characterized by its integrals over the sets of the associated σ ‐field. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical analysis of dissolution processes in cementitious materials using discontinuous and continuous Galerkin time integration schemes
Authors: Kuhl Detlef , Meschke Günther 
Published: August 2006

AbstractThe present paper is concerned with the numerical integration of non‐linear reaction–diffusion problems by means of discontinuous and continuous Galerkin methods. The first‐order semidiscrete initial value problem of calcium leaching of cementitious materials, based on a phenomenological dissolution model, an electrolyte diffusion model and the spatial p‐finite element discretization, is used as a highly non‐linear model problem. A p‐finite element method is used for the spatial discretization. In the context of discontinuous Galerkin methods the semidiscrete mass balance and the continuity of the primary variables are weakly formulated within time steps and between time steps, respectively. Continuous Galerkin methods are obtained by the strong enforcement of the continuity condition as special cases. The introduction of a natural time co‐ordinate allows for the application of standard higher order temporal shape functions of the p‐Lagrange type and the well‐known Gauss–Legendre quadrature of associated time integrals. It is shown, that arbitrary order accurate integration schemes can be developed within the framework of the proposed temporal p‐Galerkin methods. Selected benchmark analyses of calcium dissolution demonstrate the robustness of these methods with respect to pronounced changes of the reaction term and non‐smooth changes of Dirichlet boundary conditions. Copyright © 2006 John Wiley & Sons, Ltd.