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Available Results (available + result)
Selected AbstractsMinimally invasive surgery for esophageal cancerASIAN JOURNAL OF ENDOSCOPIC SURGERY, Issue 3 2010AJ Greenstein Abstract Background: Esophageal cancer is among the most deadly cancers worldwide, and esophagectomy remains the standard of care in trying to cure this. Efforts to decrease the incidence of complications in esophagectomy without compromising the efficacy of the procedure have stimulated interest in minimally invasive esophagectomy (MIE), and a wide variety of MIE techniques have been refined by surgeons at specialized centers worldwide. Data sources: Systematic PubMed searches identified articles related to MIE technique, complications, and outcomes. Conclusions: Several techniques have been developed for MIE, none of which has been deemed superior, but as a whole, they represent a safe alternative to open surgery. Available results from case series and comparative studies suggest trends towards improved short-term outcomes with equivalent efficacy but without definitive advantages. [source] Classical and advanced multilayered plate elements based upon PVD and RMVT.INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 3 2002Part 2: Numerical implementations Abstract This paper presents numerical evaluations related to the multilayered plate elements which were proposed in the companion paper (Part 1). Two-dimensional modellings with linear and higher-order (up to fourth order) expansion in the z -plate/layer thickness direction have been implemented for both displacements and transverse stresses. Layer-wise as well as equivalent single-layer modellings are considered on both frameworks of the principle of virtual displacements and Reissner mixed variational theorem. Such a variety has led to the implementation of 22 plate theories. As far as finite element approximation is concerned, three quadrilaters have been considered (four-, eight- and nine-noded plate elements). As a result, 22×3 different finite plate elements have been compared in the present analysis. The automatic procedure described in Part 1, which made extensive use of indicial notations, has herein been referred to in the considered computer implementations. An assessment has been made as far as convergence rates, numerical integrations and comparison to correspondent closed-form solutions are concerned. Extensive comparison to early and recently available results has been made for sample problems related to laminated and sandwich structures. Classical formulations, full mixed, hybrid, as well as three-dimensional solutions have been considered in such a comparison. Numerical substantiation of the importance of the fulfilment of zig-zag effects and interlaminar equilibria is given. The superiority of RMVT formulated finite elements over those related to PVD has been concluded. Two test cases are proposed as ,desk-beds' to establish the accuracy of the several theories. Results related to all the developed theories are presented for the first test case. The second test case, which is related to sandwich plates, restricts the comparison to the most significant implemented finite elements. It is proposed to refer to these test cases to establish the accuracy of existing or new higher-order, refined or improved finite elements for multilayered plate analyses. Copyright © 2002 John Wiley & Sons, Ltd. [source] Free vibration of sandwich plates with laminated facesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2002W. X. Yuan Description is given of the development of a spline finite strip method for predicting the natural frequencies and modes of conventional rectangular sandwich plates. The faceplates are treated as being classically thin and may be of composite laminated construction. The core is modelled as a three-dimensional body. Finite strip stiffness and mass properties are based on a displacement field which represents eight fundamental through-thickness displacements as a series of products of longitudinal B-spline functions and crosswise Lagrangian or Hermitian polynominal shape functions. The solution procedure utilizes the efficient superstrip concept in conjunction with the extended Sturm sequence-bisection approach. A variety of applications of the developed analysis capability is described which demonstrates the nature of the convergence of the finite strip predictions of natural frequencies and the close comparison of these predictions with available results in the literature, and also the use of the capability in parametric studies. Copyright © 2002 John Wiley & Sons, Ltd. [source] In-plane vibrations of shear deformable curved beamsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2001Moshe Eisenberger Abstract This paper presents the exact dynamic stiffness matrix for a circular beam with a uniform cross-section. The stiffness matrix is frequency dependent, and the natural frequencies are those that cause the matrix to become singular. Using this matrix the exact natural frequencies of circular beams with various boundary conditions are calculated and compared with available results in the literature. Copyright © 2001 John Wiley & Sons, Ltd. [source] Guaranteed recursive non-linear state bounding using interval analysisINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 3 2002Michel Kieffer Abstract The problem considered here is state estimation in the presence of unknown but bounded state perturbations and measurement noise. In this context, most available results are for linear models, and the purpose of the present paper is to deal with the non-linear case. Based on interval analysis and the notion of set inversion, a new state estimator is presented, which evaluates a set estimate guaranteed to contain all values of the state that are consistent with the available observations, given the perturbation and noise bounds and a set containing the initial value of the state. To the best of our knowledge, it is the first estimator for which this claim can be made. The precision of the set estimate can be improved, at the cost of more computation. Theoretical properties of the estimator are studied, and computer implementation receives special attention. A simple illustrative example is treated. Copyright © 2002 John Wiley & Sons, Ltd. [source] Performance analysis of reset control systemsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 11 2010W. H. T. M. Aangenent Abstract In this paper we present a general linear matrix inequality-based analysis method to determine the performance of a SISO reset control system in both the ,2 gain and ,2 sense. In particular, we derive convex optimization problems in terms of LMIs to compute an upperbound on the ,2 gain performance and the ,2 norm, using dissipativity theory with piecewise quadratic Lyapunov functions. The results are applicable to for all LTI plants and linear-based reset controllers, thereby generalizing the available results in the literature. Furthermore, we provide simple though convincing examples to illustrate the accuracy of our proposed ,2 gain and ,2 norm calculations and show that, for an input constrained ,2 problem, reset control can outperform a linear controller designed by a common nonlinear optimization method. Copyright © 2009 John Wiley & Sons, Ltd. [source] Reduced-order impulsive control for a class of nonlinear systemsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 8 2010Yan-Wu Wang Abstract Impulsive control of nonlinear systems is an attractive topic and a number of interesting results have been obtained in the recent years. However, most of the available results need to employ full information of the system states to achieve the desired objectives. In this paper, a reduced-order impulsive control strategy that needs only part of state components is studied for a general class of nonlinear system, which is feasible for the case when some of the system states are not available or controllable. Typical chaotic systems, such as Lorenz system, Chua's oscillator, and Chen's system, are taken as examples. A systematic design scheme is proposed to select the impulsive intervals. After some theoretical analysis, simulation results illustrate the effectiveness of the proposed control scheme. Copyright © 2009 John Wiley & Sons, Ltd. [source] Efficiency in an Economy with Fixed CostsJOURNAL OF PUBLIC ECONOMIC THEORY, Issue 2 2001Andrea Dall'olio It is by now well known that in an economy with increasing returns, first-best efficiency may be impossible to attain through an equilibrium concept based on market prices, even if firms are regulated to follow marginal cost pricing. We examine the efficiency issue in a special but important class of economies in which the only source of nonconvexities is the presence of fixed costs. Even in this context, it is possible that none of the equilibria based on marginal cost pricing are efficient (unless additional, strong assumptions are made). We argue that available results on the existence of an efficient two-part tariff equilibrium rely on very strong assumptions, and we provide a positive result using a weak surplus condition. Our approach can also be used to establish the existence of an efficient marginal cost pricing equilibrium with endogenously chosen lump-sum taxes if the initial endowment is efficient in the economy without the production technology. [source] Angle-resolved photoelectron spectroscopy study of the GaN(0001)-2×2 surfacePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010P. Lorenz Abstract GaN(0001)-2×2 surfaces were investigated by angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) as well as X-ray photoelectron spectroscopy (XPS). Contamination- and metal-free GaN thin films with a 2×2 reconstruction and a rms roughness below 1 nm were grown on 6H-SiC(0001) by plasma assisted molecular beam epitaxy (PAMBE). The valence band structure of the surface was investigated in-situ with ARUPS along the and directions of the surface Brillouin zone. Weak dispersive surface states related to the unreconstructed GaN surface or to the 2×2 superstructure as well as the dispersion of electron states of the bulk band structure are identified and compared to available results from density functional theory (DFT) calculations [Phys. Rev. B 77, 115120 (2008)] for GaN(0001). (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Superparasitism in gregarious hymenopteran parasitoids: ecological, behavioural and physiological perspectivesPHYSIOLOGICAL ENTOMOLOGY, Issue 3 2007SILVIA DORN Abstract Superparasitism in gregarious wasps occurs with the deposition of a clutch of eggs by a female into a host already parasitized by itself or a conspecific female. This review synthesizes and interprets the available results in the literature reported from field studies, and from behavioural and physiological investigations. To study superparasitism at the ecosystem level, methodological issues have to be solved to determine threshold values beyond which multiple offspring can be indisputably classified as originating from superparasitism. This life strategy is then discussed from the parasitoid's perspective, considering time and egg limitation, host discrimination, clutch size, offspring body size and sex ratio, as well as development time and survival rate of offspring, with special emphasis on physiological facilitation and constraints. Then, superparasitism in gregarious species is evaluated from the host's angle, addressing host survivorship and development, host food consumption and growth. Although superparasitism may be beneficial for either the first or the superparasitizing female, depending on the system, it is detrimental for both of them under conditions of extreme superparasitism. Recent methodological and experimental advances encourage further studies on the adaptive host choice under field and laboratory conditions, as well as on mechanisms underlying success of the first or the superparasitizing female and their progeny. [source] Electron Transfer to Sulfides and Disulfides: Intrinsic Barriers and Relationship between Heterogeneous and Homogeneous Electron-Transfer KineticsCHEMISTRY - A EUROPEAN JOURNAL, Issue 28 2007Belèn Meneses Abstract The electron-acceptor properties of series of related sulfides and disulfides were investigated in N,N -dimethylformamide with homogeneous (redox catalysis) and/or heterogeneous (cyclic voltammetry and convolution analysis) electrochemical techniques. The electron-transfer rate constants were determined as a function of the reaction free energy and the corresponding intrinsic barriers were determined. The dependence of relevant thermodynamic and kinetic parameters on substituents was assessed. The kinetic data were also analyzed in relation to corresponding data pertaining to reduction of diaryl disulfides. All investigated reductions take place by stepwise dissociative electron transfer (DET) which causes cleavage of the CalkylS or SS bond. A generalized picture of how the intrinsic electron-transfer barrier depends on molecular features, ring substituents, and the presence of spacers between the frangible bond and aromatic groups was established. The reduction mechanism was found to undergo a progressive (and now predictable) transition between common stepwise DET and DET proceeding through formation of loose radical anions. The intrinsic barriers were compared with available results for ET to several classes of dissociative- and nondissociative-type acceptors, and this led to verification that the heterogeneous and the homogeneous data correlate as predicted by the Hush theory. [source] Probiotics for the treatment of women with bacterial vaginosisCLINICAL MICROBIOLOGY AND INFECTION, Issue 7 2007M. E. Falagas Abstract This review considers whether probiotics are effective agents for the treatment and/or prevention of bacterial vaginosis (BV). There seems to be an association between the absence of, or low concentrations of, vaginal lactobacilli and the development of BV. Many studies have suggested that the presence of H2O2 -producing vaginal lactobacilli may protect against BV, although some studies do not support this hypothesis. In-vitro studies have suggested that certain specific strains of lactobacilli are able to inhibit the adherence of Gardnerella vaginalis to the vaginal epithelium and/or produce H2O2, lactic acid and/or bacteriocins, which inhibit the growth of bacteria causing BV. Clinical trials showed that intra-vaginal administration of Lactobacillus acidophilus for 6,12 days, or oral administration of L. acidophilus or Lactobacillus rhamnosus GR-1 and Lactobacillus fermentum RC-14 for 2 months, resulted in the cure of BV (defined as a 0,1 positive score according to Amsel's criteria), and/or reduced the recurrences of BV, and/or caused an increase in vaginal lactobacilli and restoration of a normal vaginal microbiota, significantly more frequently than did a placebo, acetic acid or no treatment. However, several trials have found no significant difference in the cure rate of BV and in the number of vaginal lactobacilli after intra-vaginal instillation of lactobacilli when compared with the effect of a placebo or oestrogen. Thus, although the available results concerning the effectiveness of the administration of lactobacilli for the treatment of BV are mostly positive, it cannot yet be concluded definitively that probiotics are useful for this purpose. 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