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41.
Celiac disease is a condition associated with the ingestion of gluten by genetically susceptible individuals. Measurement of serum antigliadin antibodies is a diagnostic tool also used as a means of monitoring a patient's compliance to a gluten-free diet. In this work, we demonstrate the applicability of an electrochemical supramolecular platform based on cyclodextrin-modified gold surfaces to detect antigliadin antibodies in real serum samples. Several support layer-biorecognition element combinations were tested in order to maximize the electrochemical response, and the assay was optimized in terms of incubation times and resistance to nonspecific interactions. The developed supramolecular biosensor was then applied to the amperometric detection of antigliadin IgA and IgG autoantibodies in real samples of celiac disease patients under follow-up treatment; the results were compared with a commercial enzyme linked immunosorbent assay (ELISA) test, and an excellent correlation was observed between both methods. 相似文献
42.
Federico C. Buroni Jhonny E. Ortiz Andrés Sáez 《International journal for numerical methods in engineering》2011,86(9):1125-1143
In this paper we develop an alternative boundary element method (BEM) formulation for the analysis of anisotropic three‐dimensional (3D) elastic solids. Our implementation is based on the derivation of explicit expressions for the fundamental solution displacements and tractions, of general validity for any class of anisotropic materials, by means of Stroh formalism and Cauchy's residue theory. The resulting fundamental solution remains valid for mathematical degenerate cases when Stroh's eigenvalues are coincident, meanwhile it does not exhibit numerical instabilities for quasi‐degenerate cases when Stroh's eigenvalues are nearly equal. A multiple pole residue approach is followed, leading to general explicit expressions to evaluate the traction fundamental solution for poles of m‐multiplicity. Despite the existence of general displacement solutions in the literature, and for the sake of completeness, the same approach as for the traction solution is considered to derive the displacement fundamental solution as well. Based on these solutions, an explicit BEM approach for the numerical solution of 3D linear elastic problems for solids with general anisotropic behavior is presented. The analysis of cracked anisotropic solids is also considered. Details on the numerical implementation and its validation for degenerate cases are discussed. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
43.
G. Venturini J. Z. Yang M. Ortiz J. E. Marsden 《International journal for numerical methods in engineering》2011,88(6):586-611
This paper is concerned with the classical problem of wave propagation in discrete models of nonuniform spatial resolution. We develop a new class of Replica Time Integrators (RTIs) that permit the two‐way transmission of thermal phonons across mesh interfaces. This two‐way transmissibility is accomplished by representing the state of the coarse regions by means of replica ensembles, consisting of collections of identical copies of the coarse regions. In dimension d, RTIs afford an O(nd) speed‐up factor in sequential mode, and O(nd + 1) in parallel, over regions that are coarsened n‐fold. In this work, we restrict ourselves to the solution of the 3d continuous wave equation, for both linear and non‐linear materials. By a combination of phase‐error analysis and numerical testing, we show that RTIs are convergent and result in exact two‐way transmissibility at the Courant–Friedrichs–Lewy limit for any angle of incidence. In this limit, RTIs allow step waves and high‐frequency harmonics to cross mesh interfaces in both directions without internal reflections or appreciable loss or addition of energy. The possible connections of RTIs with discrete‐to‐continuum approaches and, in particular, with the transition between molecular dynamics and continuum thermodynamics are also pointed to by way of future outlook. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
44.
45.
This paper is concerned with the implementation of variational arbitrary Lagrangian–Eulerian formulations, also known as variational r‐adaption methods. These methods seek to minimize the energy function with respect to the finite‐element mesh over the reference configuration of the body. We propose a solution strategy based on a viscous regularization of the configurational forces. This procedure eliminates the ill‐posedness of the problem without changing its solutions, i.e. the minimizers of the regularized problems are also minimizers of the original functional. We also develop strategies for optimizing the triangulation, or mesh connectivity, and for allowing nodes to migrate in and out of the boundary of the domain. Selected numerical examples demonstrate the robustness of the solution procedures and their ability to produce highly anisotropic mesh refinement in regions of high energy density. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
46.
A variational h‐adaptive finite element formulation is proposed. The distinguishing feature of this method is that mesh refinement and coarsening are governed by the same minimization principle characterizing the underlying physical problem. Hence, no error estimates are invoked at any stage of the adaption procedure. As a consequence, linearity of the problem and a corresponding Hilbert‐space functional framework are not required and the proposed formulation can be applied to highly non‐linear phenomena. The basic strategy is to refine (respectively, unrefine) the spatial discretization locally if such refinement (respectively, unrefinement) results in a sufficiently large reduction (respectively, sufficiently small increase) in the energy. This strategy leads to an adaption algorithm having O(N) complexity. Local refinement is effected by edge‐bisection and local unrefinement by the deletion of terminal vertices. Dissipation is accounted for within a time‐discretized variational framework resulting in an incremental potential energy. In addition, the entire hierarchy of successive refinements is stored and the internal state of parent elements is updated so that no mesh‐transfer operator is required upon unrefinement. The versatility and robustness of the resulting variational adaptive finite element formulation is illustrated by means of selected numerical examples. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
47.
A Jiménez Verdejo M Arrabal Martín J Miján Ortiz J Sánchez Tamayo F López-Carmona Pintado A Zuluaga Gómez 《Canadian Metallurgical Quarterly》1998,51(7):709-715
OBJECTIVE: To describe the efficacy of extracorporeal shock wave lithotripsy in the treatment of lithiasis in patients with solitary functioning kidney. METHODS: The study comprised 56 patients with solitary kidney that had been treated by extracorporeal shock wave lithotripsy. These patients had a solitary kidney for the following reasons: 30 had undergone nephrectomy due to lithiasis, 11 had lost renal function arising from lithiasis, 9 had undergone nephrectomy for other pathologies and 6 had renal agenesis. Nine stone variables and treatment were analyzed. The same variables were analyzed and compared for statistical significance in a representative sample of 125 lithiasic patients with two kidneys who were treated by ESWL. RESULTS: Patients with solitary kidney frequently had a single calculus of < or = 1 cm located in calyces, unobstructive and did not require complementary endourological procedures. The mean number of shock waves was 8535. The psot-lithotripsy success rate was 82.1%; 98.2% had no complications. Comparison of these variables in both groups of patients showed statistically significant differences for stone location, indication for complementary endourological procedures and the number of shock waves utilized. CONCLUSIONS: In our view, ESWL is the treatment of choice in patients with lithiasis in a solitary kidney due to its high success rate and low morbidity. Stringent criteria must be employed before indicating prior endourological procedures to preserve the patency of the excretory tract and to minimize the risk of ureteral obstruction. 相似文献
48.
Sandra Balan Mendoza Jaime Sylvio Alves Ortiz Tiago Bassani Dantas Cristiano Ferreira Damasceno 《Packaging Technology and Science》2002,15(4):225-230
The mechanical performance of lightweight glass packages produced by the NNPB (narrow neck press and blow) process was evaluated by comparison with the same glass packages (regular weight) produced by the conventional process (blow and blow). The temper number (annealing process evaluation), thickness distribution behaviour and mechanical performance (impact, vertical load and thermal shock strength) were analysed before and after line simulation, applied in optimized conditions in the laboratory. The performance of lightweight glass packages under transport simulation (truck envelope) in relation to the regular weight bottles was also evaluated. Both bottles presented residual stress values within the specified limits. The lightweight glass bottles had a more homogenous thickness distribution in comparison with the regular weight bottles and a better performance (about 33% improvement) in relation to the impact strength, especially in the heel, even when evaluated after line simulation. As to the vertical load strength, the lightweight glass bottle also indicated a superior performance to the regular weight bottle, both before and after line simulation. Both bottles withstood the temperature difference of 42°C that such packages are supposed to resist according to thermal shock specification. Due to the better thickness distribution of lightweight glass packages, they withstood a maximum temperature difference (progressive thermal shock) of 5–10°C higher than the regular weight bottles. No restrictions of the lightweight glass packages submitted to the transport simulation were found. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
49.
Susan J. Masten Kuan‐Chung Chen Jaime Graulau Subhash L. Kari Kyung‐Hyuk Lee 《工程教育杂志》2002,91(1):69-80
The use of computer‐based technology is becoming more prevalent in the classroom. As a part of an educational research project sponsored by the GE Foundation, strategies for augmenting a course, Introduction to Environmental Engineering (CE 280), were investigated including cross‐disciplinary experiences in teamwork, design, and the use of advanced teaching technologies such as the web. Interactive tools to assist student learning were developed and refined. Efforts have focused on developing an extensive website, web‐based quizzes and homework assignments, and tutorials. Base groups were used to provide both intellectual and emotional support to students. This paper summarizes the development of this course and the impact of rapid feedback on the progression of student understanding. 相似文献
50.
M. Gonzalez B. Schmidt M. Ortiz 《International journal for numerical methods in engineering》2010,82(2):205-241
We present a class of integration schemes for Lagrangian mechanics, referred to as energy‐stepping integrators, that are momentum and energy conserving, symplectic and convergent. In order to achieve these properties we replace the original potential energy by a piecewise constant, or terraced approximation at steps of uniform height. By taking steps of diminishing height, an approximating sequence of energies is generated. The trajectories of the resulting approximating Lagrangians can be characterized explicitly and consist of intervals of piecewise rectilinear motion. We show that the energy‐stepping trajectories are symplectic, exactly conserve all the momentum maps of the original system and, subject to a transversality condition, converge to trajectories of the original system when the energy step is decreased to zero. These properties, the excellent long‐term behavior of energy‐stepping and its automatic time‐step selection property, are born out by selected examples of application, including the dynamics of a frozen Argon cluster, the spinning of an elastic cube and the collision of two elastic spheres. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献