Chemical composition and antimicrobial activity of propolis collected from some localities of Western Algeria

The chemical analysis and antibacterial activity of propolis collected from some parts of Western Algeria were investigated. The ethanolic extracts of propolis (EEP) were evaluated for further investigation. The major constituents in EEP were identified by high-performance liquid chromatography (HPLC) analysis. All EEP samples were active against Gram positive bacteria (Staphylococcus aureus, Bacillus subtilis, Bacillus cereus), but no activity was found against Gram negative bacteria (Pseudomonas aeruginosa, Escherichia coli). The mean diameters of growth inhibition of the EEP ranged between 8.05 and 21.4 mm. The propolis extract obtained from Sidi bel Abbés (SFS-SBA) was more active than other samples as well as showed unique HPLC profile. These results support the idea that propolis can be a promising natural food preservative in food industry and alternative candidate for management of bacterial infections caused by drug-resistant microorganisms

Inverse methods with fading regularization for the identification of boundary conditions in thin plate theory

Dans cette thèse, nous nous intéressons, dans une première partie, à la résolution, par la méthode de régularisation évanescente, du problème de Cauchy associé à l’équation biharmonique. Une attention particulière est consacrée à la mise en œuvre numérique de l’algorithme itératif de résolution en utilisant différentes méthodes numériques telles que la méthode des solutions fondamentales et la méthode des éléments finis et en proposant un nouveau critère d’arrêt de l’algorithme itératif. Après avoir traité le problème avec des conditions aux limites mathématiques, une généralisation de l’étude au problème de Cauchy en théorie des plaques minces, que l’on rencontre en mécanique, est proposée. En effet, la flexion des plaques minces sous les hypothèses de Kirchhoff-Love, est régie par la même équation aux dérivées partielles et du point de vue numérique, des éléments finis de type plaque de Kirchhoff sont combinés avec la technique de régularisation évanescente pour résoudre le problème. Cette approche a, en particulier, permis d’obtenir des reconstructions précises de la solution et de sa dérivée normale sur toute la frontière notamment lors des domaines non réguliers. Ces résultats ont, alors, inspirés l’utilisation des éléments finis de type plaque pour résoudre des problèmes de Cauchy associés à des équations aux dérivées partielles du second ordre. Les résultats obtenus sont très compétitifs par rapport à ceux d’études antérieures. La robustesse vis-à-vis des données très bruitées est également un atout de cette stratégie.In this thesis, the resolution of the Cauchy problem associated with the biharmonic equation using the fading regularization method is investigated. A particular attention is devoted to the numerical implementation of the iterative algorithm used for the resolution and this by using various numerical methods such as the method of fundamental solutions and the finite element method while proposing a new stopping criterion of the iterative algorithm. Once the mathematical problem, with mathematical boundary conditions, has been treated, the study thus carried out is then generalized to the study of the Cauchy problem in thin plate theory, since in mechanics, the bending of thin plates under Kirchhoff-Love’s assumptions, is governed by the same differential equation. From a numerical point of view, plate finite elements based on Kirchhoff theory known as discrete Kirchhoff finite elements are combined with the fading regularization technique to solve the problem. This strategy made it possible to obtain accurate reconstructions of the solution and of its normal derivative on the whole boundary, in particular for non-smooth geometries. The results thus obtained were an inspiration for the use of plate-type finite elements to solve Cauchy problems associated with second order partial differential equations. The obtained results are very competitive with those of previous studies. Robustness against high level noisy data is also an advantage of this strategy

Méthodes inverses à régularisation évanescente pour l'identification de conditions aux limites en théorie des plaques minces

In this thesis, the resolution of the Cauchy problem associated with the biharmonic equation using the fading regularization method is investigated. A particular attention is devoted to the numerical implementation of the iterative algorithm used for the resolution and this by using various numerical methods such as the method of fundamental solutions and the finite element method while proposing a new stopping criterion of the iterative algorithm. Once the mathematical problem, with mathematical boundary conditions, has been treated, the study thus carried out is then generalized to the study of the Cauchy problem in thin plate theory, since in mechanics, the bending of thin plates under Kirchhoff-Love’s assumptions, is governed by the same differential equation. From a numerical point of view, plate finite elements based on Kirchhoff theory known as discrete Kirchhoff finite elements are combined with the fading regularization technique to solve the problem. This strategy made it possible to obtain accurate reconstructions of the solution and of its normal derivative on the whole boundary, in particular for non-smooth geometries. The results thus obtained were an inspiration for the use of plate-type finite elements to solve Cauchy problems associated with second order partial differential equations. The obtained results are very competitive with those of previous studies. Robustness against high level noisy data is also an advantage of this strategy.Dans cette thèse, nous nous intéressons, dans une première partie, à la résolution, par la méthode de régularisation évanescente, du problème de Cauchy associé à l’équation biharmonique. Une attention particulière est consacrée à la mise en œuvre numérique de l’algorithme itératif de résolution en utilisant différentes méthodes numériques telles que la méthode des solutions fondamentales et la méthode des éléments finis et en proposant un nouveau critère d’arrêt de l’algorithme itératif. Après avoir traité le problème avec des conditions aux limites mathématiques, une généralisation de l’étude au problème de Cauchy en théorie des plaques minces, que l’on rencontre en mécanique, est proposée. En effet, la flexion des plaques minces sous les hypothèses de Kirchhoff-Love, est régie par la même équation aux dérivées partielles et du point de vue numérique, des éléments finis de type plaque de Kirchhoff sont combinés avec la technique de régularisation évanescente pour résoudre le problème. Cette approche a, en particulier, permis d’obtenir des reconstructions précises de la solution et de sa dérivée normale sur toute la frontière notamment lors des domaines non réguliers. Ces résultats ont, alors, inspirés l’utilisation des éléments finis de type plaque pour résoudre des problèmes de Cauchy associés à des équations aux dérivées partielles du second ordre. Les résultats obtenus sont très compétitifs par rapport à ceux d’études antérieures. La robustesse vis-à-vis des données très bruitées est également un atout de cette stratégie

Méthodes inverses à régularisation évanescente pour l'identification de conditions aux limites en théorie des plaques minces

In this thesis, the resolution of the Cauchy problem associated with the biharmonic equation using the fading regularization method is investigated. A particular attention is devoted to the numerical implementation of the iterative algorithm used for the resolution and this by using various numerical methods such as the method of fundamental solutions and the finite element method while proposing a new stopping criterion of the iterative algorithm. Once the mathematical problem, with mathematical boundary conditions, has been treated, the study thus carried out is then generalized to the study of the Cauchy problem in thin plate theory, since in mechanics, the bending of thin plates under Kirchhoff-Love’s assumptions, is governed by the same differential equation. From a numerical point of view, plate finite elements based on Kirchhoff theory known as discrete Kirchhoff finite elements are combined with the fading regularization technique to solve the problem. This strategy made it possible to obtain accurate reconstructions of the solution and of its normal derivative on the whole boundary, in particular for non-smooth geometries. The results thus obtained were an inspiration for the use of plate-type finite elements to solve Cauchy problems associated with second order partial differential equations. The obtained results are very competitive with those of previous studies. Robustness against high level noisy data is also an advantage of this strategy.Dans cette thèse, nous nous intéressons, dans une première partie, à la résolution, par la méthode de régularisation évanescente, du problème de Cauchy associé à l’équation biharmonique. Une attention particulière est consacrée à la mise en œuvre numérique de l’algorithme itératif de résolution en utilisant différentes méthodes numériques telles que la méthode des solutions fondamentales et la méthode des éléments finis et en proposant un nouveau critère d’arrêt de l’algorithme itératif. Après avoir traité le problème avec des conditions aux limites mathématiques, une généralisation de l’étude au problème de Cauchy en théorie des plaques minces, que l’on rencontre en mécanique, est proposée. En effet, la flexion des plaques minces sous les hypothèses de Kirchhoff-Love, est régie par la même équation aux dérivées partielles et du point de vue numérique, des éléments finis de type plaque de Kirchhoff sont combinés avec la technique de régularisation évanescente pour résoudre le problème. Cette approche a, en particulier, permis d’obtenir des reconstructions précises de la solution et de sa dérivée normale sur toute la frontière notamment lors des domaines non réguliers. Ces résultats ont, alors, inspirés l’utilisation des éléments finis de type plaque pour résoudre des problèmes de Cauchy associés à des équations aux dérivées partielles du second ordre. Les résultats obtenus sont très compétitifs par rapport à ceux d’études antérieures. La robustesse vis-à-vis des données très bruitées est également un atout de cette stratégie

Fading regularization method and DKQ plate elements for the Cauchy problem associated with the biharmonic equation

Thin plates find applications in several scientific and technical fields. We recall here the case of plate elements for a bridge deck. In certain situations, it may be mandatory to ensure the embedding and support of these plates for correct installation of this structure. However, direct measurements may be impossible or difficult to obtain during construction or during maintenance. An opposite problem then arises! Objectives: The aim of this study is to solve the inverse Cauchy-type problem for the bilaplacian operator, which governs the bending of thin plates, such that the boundary conditions are only available on part of the boundary. We propose to apply the fading regularization method and implement it numerically using discrete Kirchhoff (DK) plate elements

Fading regularization FEM algorithms for the Cauchy problem associated with the two‐dimensional biharmonic equation

International audienc

Preliminary report of mosquitoes survey at Tonga Lake (North-East Algeria)

peer reviewedBackground: Mosquitoes are transmitters of several human diseases including, malaria, filariasis, West Nile virus and Rift Valley fever virus. To planified and succeful any mosquito vector control, a good understanding of the occurrence of specific important vector species, their abundance and distribution are needed. Objectives: The present study aimed to identify the mosquito potential vectors distributed throughout Tonga Lake region, a part of National Park of El-Kala situated in northeastern Algeria and to discuss the epidemiological importance of these insects. Results: Thirteen species representing five genera were identified: Ae. brelandi, Ae. vexans, An. plumbeus, An. labranchiae, Cx. pipiens s. l., Cx. perexiguus, Cx. theileri, Cx. pusillus, Cx. modestus, Cx. impudicus, Cs. longiareolata, Cs. annulata, Ur. unguiculata. The dominant species was Cx. pipiens s. l. with more than 70%. Conclusion: The occurrence of Aedes, Anopheles and Culex is suggestive of the presence of a risk for vector-borne diseases such as malaria, West Nile fever, Rift Valley Fever and filariasis in the area. In this study, results on species diversity may help in the future planning of vector control measures

AHL-dependent quorum sensing inhibition: synthesis and biological evaluation of α-(N-alkyl-carboxamide)-γ-butyrolactones and α-(N-alkyl-sulfonamide)-γ-butyrolactones.

International audienceNew N-acylhomoserine lactone (AHL) analogues in which the amide function is replaced by a reverse-amide one have been studied as AHL QS modulators. The series of compounds consists of α-(N-alkyl-carboxamide)-γ-butyrolactones, α-(N-alkyl-sulfonamide)-γ-butyrolactones, and 2-(N-alkyl-carboxamide)-cyclopentanones and cyclopentanols. Most active compounds exhibited antagonist activities against LuxR reaching the 30 μM range

Heterocyclic Chemistry Applied to the Design of N-Acyl Homoserine Lactone Analogues as Bacterial Quorum Sensing Signals Mimics

International audienceN-acyl homoserine lactones (AHLs) are small signaling molecules used by many Gram-negative bacteria for coordinating their behavior as a function of their population density. This process, based on the biosynthesis and the sensing of such molecular signals, and referred to as Quorum Sensing (QS), regulates various gene expressions, including growth, virulence, biofilms formation, and toxin production. Considering the role of QS in bacterial pathogenicity, its modulation appears as a possible complementary approach in antibacterial strategies. Analogues and mimics of AHLs are therefore biologically relevant targets, including several families in which heterocyclic chemistry provides a strategic contribution in the molecular design and the synthetic approach. AHLs consist of three main sections, the homoserine lactone ring, the central amide group, and the side chain, which can vary in length and level of oxygenation. The purpose of this review is to summarize the contribution of heterocyclic chemistry in the design of AHLs analogues, insisting on the way heterocyclic building blocks can serve as replacements of the lactone moiety, as a bioisostere for the amide group, or as an additional pattern appended to the side chain. A few non-AHL-related heterocyclic compounds with AHL-like QS activity are also mentione

Synthesis and biological evaluation of new N-acyl-homoserine-lactone analogues, based on triazole and tetrazole scaffolds, acting as LuxR-dependent quorum sensing modulators.

International audienceNew analogues of N-acyl-homoserine-lactone (AHL), in which the amide was replaced by a triazole or tetrazole ring, were prepared and tested for their activity as LuxR-dependent QS modulators. Several compounds showed a level of antagonistic or agonistic activity, notably some 1,4-triazolic and 1,5-tetrazolic derivatives, whereas the 2,5-tetrazolic compounds were inactive. In 1,5-tetrazoles, substituted with butyrolactone and an alkyl chain, the activity was reversed, depending on the connection between the lactone and the tetrazole. The C-N connected compounds were agonists whereas the C-C connected ones were antagonists