178,687 research outputs found
Numerical analysis of a transmission problem with Signorini contact using mixed-FEM and BEM
No full text© EDP Sciences, SMAI 2011This paper is concerned with the dual formulation of the interface problem consisting of a linear partial differential equation with variable coefficients in some bounded Lipschitz domain Ω in
Rn (n ≥ 2) and the Laplace equation with some radiation condition in the unbounded exterior domain Ωc := Rn\￣Ω. The two problems are coupled by transmission and Signorini contact conditions on the interface Γ = ∂Ω. The exterior part of the interface problem is rewritten using a Neumann to Dirichlet mapping (NtD) given in terms of boundary integral operators. The resulting variational formulation becomes a variational inequality with a linear operator. Then we treat the corresponding numerical scheme and discuss an approximation of the NtD mapping with an appropriate discretization of the inverse Poincar´e-Steklov operator. In particular, assuming some abstract approximation properties and a discrete inf-sup condition, we show unique solvability of the discrete scheme and obtain the corresponding a-priori error estimate. Next, we prove that these assumptions are satisfied with Raviart- Thomas elements and piecewise constants in Ω, and continuous piecewise linear functions on Γ. We suggest a solver based on a modified Uzawa algorithm and show convergence. Finally we present some numerical results illustrating our theory
Boundary augmented Lagrangian method for the Signorini problem
No full textsummary:An augmented Lagrangian method, based on boundary variational formulations and fixed point method, is designed and analyzed for the Signorini problem of the Laplacian. Using the equivalence between Signorini boundary conditions and a fixed-point problem, we develop a new iterative algorithm that formulates the Signorini problem as a sequence of corresponding variational equations with the Steklov-Poincaré operator. Both theoretical results and numerical experiments show that the method presented is efficient
The Impact of the Bolsa Família Programme on Beneficiaries? Fertility
No full textThe Bolsa Família programme1 provides a benefit up to maximum of three benefits2 to every pregnant woman and child up to 15 years of age and another benefit to teenagers between 16 and 17 years old, up to a maximum of two benefits, in families with less than R$140.00 per capita monthly income. This feature of the programme has led some commentators to fear that it could trigger an increase in fertility of the poor. The possible impact on fertility behaviour has drawn very little attention from researchers, despite being one of the most popular criticisms against to Conditional Cash Transfers (CCT) programmes. To our knowledge, only two papers investigate this possible relationship in Brazil: Rocha (2010) and Signorini & Queiroz (2011). The empirical evidence from other countries suggests that CCTs have no significant impact on fertility. The evidence holds for other types of programmes, including those that provide only child care, traditional cash transfer programmes, and income tax exemption policies (Stecklov et al., 2007). (?)The Impact of the Bolsa Família Programme on Beneficiaries? Fertility
Observations of a high-spin yrast cascade in Cr50Kutschera, W.a, Huber, R.B.a, Signorini, C.ab, Morinaga, H
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Pharmacologically active piperazino derivatives
No full textNew piperazino derivatives of formula ##STR1## in which R is a phenyl radical substituted with at least one sulphonamido group or a substituted nitrogenated heterocyclic ring, and A is CO, CH2, SO2, possessing inhibiting activity towards carbonic anhydrase.
The new products are prepared from compounds of formula R-A-X in which X is OH, SH, halogen, OR"" or SR"" in which R"" is methyl, ethyl, phenyl, carbomethoxy, carboethoxy, and from a piperazino derivative of formula ##STR2## The R' group can also be introduced on termination of the reaction, by removing and substituting a protective group present at the nitrogen.
R is 2-methoxy-5-sulphamoyl-phenyl, 2-sulphamoylimidazyl, 2-amino-1,3,4-thiadiazole or 2-acetamido-1,3,4-thiadiazole;
R' is H, linear or branched C.sub.1 -C.sub.6 alkyl; linear or branched C.sub.2 -C.sub.6 alkenyl; alkyl-phenyl or alkenyl-phenyl, wherein phenyl is optionally monosubstituted with halogen, trihalomethyl, C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 alkoxy, or sulphonamido; C.sub.2 -C.sub.6 aliphatic acyl; C.sub.3 -C.sub.6 alkylcarboxyalkoxy; alkyl-carboxyamino in which the alkyl is C.sub.1 -C.sub.3 and the amine is mono or disubstituted by linear or branched C.sub.1 -C.sub.6 alkyl and;
R" is H, or together with R' forms a 5 or 6 membered ring condensed with the piperazine;
provided that when R is a substituted phenyl group and A is CO, R' is other than H, C.sub.1 -C.sub.4 alkyl or benzyl
Surface Enhanced Raman Spectroscopy: Principles, Substrates, and Applications
No full textSurface-enhanced Raman spectroscopy (SERS) is a spectroscopic technique that simultaneously combines fingerprint recognition capabilities, typical of vibrational spectroscopies, and very high sensitivity (down to single molecule), owing to the enhancement provided by plasmonic effects. Its discovery dates back to the 1970s, and since then, SERS has gained a lot of interest in the scientific community, as witnessed by the quick raise in the percentage of publications involving SERS, especially in the last two decades. In this book chapter, we would like to provide the reader with an overview of SERS, going from the illustration of its basic principles to the description of a wide selection of its applications. At first, the physical phenomena responsible for the electromagnetic and chemical SERS enhancements are described; thereafter, two key features of SERS, namely, its distance dependence and the concept of hot spot, are discussed, as well as the near- vs. far-field properties in plasmonic systems. Two sections are then dedicated to the materials that are more often used in SERS and to the strategies adopted to fabricate efficient SERS substrates. The last section illustrates the applications of SERS in several fields of sensing, like the detection of chemical warfare agents, environmental pollutants, food contaminants, and illicit drugs; the use of SERS in art preservation, forensic science, and medical diagnosis is also described, with specific and relevant examples from the most recent literature
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