The Experts below are selected from a list of 385899 Experts worldwide ranked by ideXlab platform
Bonnie L Bassler - One of the best experts on this subject based on the ideXlab platform.
-
flow environment and Matrix Structure interact to determine spatial competition in pseudomonas aeruginosa biofilms
eLife, 2017Co-Authors: Carey D Nadell, Deirdre Ricaurte, Jing Yan, Knut Drescher, Bonnie L BasslerAbstract:Bacteria often live in biofilms, which are microbial communities surrounded by a secreted extracellular Matrix. Here, we demonstrate that hydrodynamic flow and Matrix organization interact to shape competitive dynamics in Pseudomonas aeruginosa biofilms. Irrespective of initial frequency, in competition with Matrix mutants, wild-type cells always increase in relative abundance in planar microfluidic devices under simple flow regimes. By contrast, in microenvironments with complex, irregular flow profiles - which are common in natural environments - wild-type Matrix-producing and isogenic non-producing strains can coexist. This result stems from local obstruction of flow by wild-type Matrix producers, which generates regions of near-zero shear that allow Matrix mutants to locally accumulate. Our findings connect the evolutionary stability of Matrix production with the hydrodynamics and spatial Structure of the surrounding environment, providing a potential explanation for the variation in biofilm Matrix secretion observed among bacteria in natural environments.
-
flow environment and Matrix Structure interact to determine spatial competition in pseudomonas aeruginosa biofilms
bioRxiv, 2016Co-Authors: Carey D Nadell, Deirdre Ricaurte, Jing Yan, Knut Drescher, Bonnie L BasslerAbstract:Bacteria often live in biofilms, which are dense microbial communities surrounded by a secreted extracellular Matrix. Here, we demonstrate that hydrodynamic flow and Matrix organization interact to shape competitive dynamics in Pseudomonas aeruginosa biofilms. Irrespective of initial frequency, in competition with Matrix mutants, wild type cells always increase in relative abundance in flat-surfaced, straight-tunnel microfluidic devices under simple flow regimes. By contrast, in microenvironments with complex, irregular flow profiles - which are common in natural environments - wild type Matrix-producing and isogenic non-producing strains can coexist. This result stems from local obstruction of flow by wild-type Matrix producers, which generates regions of near-zero flow speed that favor occupation by cells that do not invest in Matrix secretion. Our findings connect the evolutionary stability of Matrix production with the hydrodynamics and spatial Structure of the surrounding environment, providing a potential explanation for the variation in biofilm Matrix secretion observed among bacteria in natural environments.
-
Extracellular Matrix Structure governs invasion resistance in bacterial biofilms
The ISME Journal, 2015Co-Authors: Carey D Nadell, Knut Drescher, Ned S Wingreen, Bonnie L BasslerAbstract:Many bacteria are highly adapted for life in communities, or biofilms. A defining feature of biofilms is the production of extracellular Matrix that binds cells together. The biofilm Matrix provides numerous fitness benefits, including protection from environmental stresses and enhanced nutrient availability. Here we investigate defense against biofilm invasion using the model bacterium Vibrio cholerae . We demonstrate that immotile cells, including those identical to the biofilm resident strain, are completely excluded from entry into resident biofilms. Motile cells can colonize and grow on the biofilm exterior, but are readily removed by shear forces. Protection from invasion into the biofilm interior is mediated by the secreted protein RbmA, which binds mother–daughter cell pairs to each other and to polysaccharide components of the Matrix. RbmA, and the invasion protection it confers, strongly localize to the cell lineages that produce it.
E A Ossa - One of the best experts on this subject based on the ideXlab platform.
-
development of as cast dual Matrix Structure dms ductile iron
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2013Co-Authors: Sandra Murcia, Marco Paniagua, E A OssaAbstract:Abstract Ductile iron is widely used due to its low cost and higher ductility than other cast irons. There has been an increased interest during the last years in improving the strength of these materials by means of heat-treating to obtain dual Matrix Structures (DMS) that enhance the properties found in Austempered Ductile Irons (ADI). This work studies the fabrication of DMS ductile cast irons with martensitic and bainitic Structures in the as-cast condition, reducing costs related to heat treating processing while improving the mechanical behavior of the material. Cast irons alloyed with nickel ranging from 0% up to 7% were produced in order to evaluate the effect of Ni–Mo content on the phase transformations and mechanical properties of the material. The effect of cooling rate in phase transformations and mechanical properties were studied using molds with different wall thicknesses, finding that addition of Nickel and Molybdenum improves substantially the strength of the as-cast ductile iron, making unnecessary any further heat treating according to the level of properties desired.
Mustafa Tayanc - One of the best experts on this subject based on the ideXlab platform.
-
influence of Matrix Structure on the fatigue properties of an alloyed ductile iron
Materials & Design, 2008Co-Authors: Gulcan Toktas, Alaaddin Toktas, Mustafa TayancAbstract:Rotary bending fatigue tests were conducted on ductile iron containing 1.25 wt% nickel, 1.03 wt% copper and 0.18 wt% molybdenum with various Matrix Structures. Several heat treatments were applied to obtain ferritic, pearlitic/ferritic, pearlitic, tempered martensitic, lower and upper ausferritic Structures in the Matrix of a pearlitic as-cast alloyed ductile iron. The tensile properties (ultimate tensile strength, 0.2% yield strength and percent elongation), the hardness and the microStructures of the Matrixes were also investigated in addition to fatigue properties. Fractured surfaces of the fatigue specimens were examined by the scanning electron microscope. The results showed that the lowest hardness, tensile and fatigue properties were obtained for the ferritic Structure and the values of these properties seemed to increase with rising pearlite content in the Matrix. While the lower ausferritic Structure had the highest fatigue strength, the upper ausferritic one showed low fatigue and tensile properties due to the formation of the second reaction during the austempering process.
-
the effect of Matrix Structure on the fatigue behavior of austempered ductile iron
Materials & Design, 2007Co-Authors: Mustafa Tayanc, K Aztekin, Ali BayramAbstract:Abstract The primary objective of this study has been to investigate the fatigue behavior of the austempered unalloyed ductile iron. Ductile iron specimens were austenized at 900 °C for 110 min and then one group specimens were austempered at 230, 330, 430 °C for 60 min, and another one group specimens were austempered at 330 °C for 30, 60, 120 min to obtain different microStructures. Rotating bending tests (10 million cycles) were conducted on the ductile iron and the austempered specimens selecting completely reversed cycle of stress ( R = minimum stress/maximum stress = −1). The highest fatigue strength was found in the bainitic Structure (ausferritic). The presence of martensite or carbide phases in the Structure of austempered ductile iron reduces the fatigue strength.
-
effect of Matrix Structure on the impact properties of an alloyed ductile iron
Materials Characterization, 2006Co-Authors: Gulcan Toktas, Mustafa Tayanc, Alaaddin ToktasAbstract:Abstract An investigation was performed to examine the influence of the Matrix Structure on the impact properties of a 1.03% Cu, 1.25% Ni and 0.18% Mo pearlitic ductile iron. Specimens were first homogenized at 925 °C for 7 h and a fully ferritic Structure was obtained in all ductile iron samples. Then, various heat treatments were applied to the homogenized specimens in order to obtain pearlitic/ferritic, pearlitic, tempered martensitic, lower and upper ausferritic Matrix Structures. The unnotched charpy impact specimens were tested at temperatures between − 80 °C and + 100 °C; the tensile properties (ultimate tensile strength, 0.2% yield strength and elongation) and the hardnesses of the Matrix Structures were investigated at room temperature. The microStructures and the fracture surfaces of the impact specimens tested at room temperature were also investigated by optical and scanning electron microscope. The results showed that the best impact properties were obtained for the ferritic Matrix Structure that had the lowest hardness, yield and tensile strength. Ductile iron with a lower ausferritic Matrix had the best combination of ultimate tensile strength, percent elongation and impact energies of all Structures.
Shahn Majid - One of the best experts on this subject based on the ideXlab platform.
-
braided Matrix Structure of the sklyanin algebra and of the quantum lorentz group
Communications in Mathematical Physics, 1993Co-Authors: Shahn MajidAbstract:Braided groups and braided matrices are novel algebraic Structures living in braided or quasitensor categories. As such they are a generalization of super-groups and super-matrices to the case of braid statistics. Here we construct braided group versions of the standard quantum groupsUq(g). They have the same FRT generatorsl± but a Matrix braided-coproductΔL=L⊗L, whereL=l+Sl−, and are self-dual. As an application, the degenerate Sklyanin algebra is shown to be isomorphic to the braided matricesBMq(2); it is a braided-commutative bialgebra in a braided category. As a second application, we show that the quantum doubleD(Uq(sl2)) (also known as the “quantum Lorentz group”) is the semidirect product as an algebra of two copies ofUq(sl2), and also a semidirect product as a coalgebra if we use braid statistics. We find various results of this type for the doubles of general quantum groups and their semi-classical limits as doubles of the Lie algebras of Poisson Lie groups.
-
braided Matrix Structure of the sklyanin algebra and of the quantum lorentz group
arXiv: High Energy Physics - Theory, 1992Co-Authors: Shahn MajidAbstract:Braided groups and braided matrices are novel algebraic Structures living in braided or quasitensor categories. As such they are a generalization of super-groups and super-matrices to the case of braid statistics. Here we construct braided group versions of the standard quantum groups $U_q(g)$. They have the same FRT generators $l^\pm$ but a Matrix braided-coproduct $\und\Delta L=L\und\tens L$ where $L=l^+Sl^-$, and are self-dual. As an application, the degenerate Sklyanin algebra is shown to be isomorphic to the braided matrices $BM_q(2)$; it is a braided-commutative bialgebra in a braided category. As a second application, we show that the quantum double $D(\usl)$ (also known as the `quantum Lorentz group') is the semidirect product as an algebra of two copies of $\usl$, and also a semidirect product as a coalgebra if we use braid statistics. We find various results of this type for the doubles of general quantum groups and their semi-classical limits as doubles of the Lie algebras of Poisson Lie groups.
Francisco Jose Alves Lemos - One of the best experts on this subject based on the ideXlab platform.
-
derris lonchocarpus urucu leguminosae extract modifies the peritrophic Matrix Structure of aedes aegypti diptera culicidae
Memorias Do Instituto Oswaldo Cruz, 2002Co-Authors: Desiely Silva Gusmao, Raimundo Brazfilho, Valeria Pascoa, Leda Mathias, Ivo Jose Curcino Vieira, Francisco Jose Alves LemosAbstract:Aqueous suspension of ethanol extracts of Derris (Lonchocarpus) urucu (Leguminosae), collected in the state ofAmazonas, Brazil, were tested for larvicidal activity against the mosquito Aedes aegypti (Diptera:Culicidae). Theaim of this study was to observe the alterations of peritrophic Matrix in Ae. aegypti larvae treated with an aqueoussuspension of D. urucu extract. Different concentrations of D. urucu root extract were tested against fourth instarlarvae. One hundred percent mortality was observed at 150 µg/ml (LC
-
derris lonchocarpus urucu leguminosae extract modifies the peritrophic Matrix Structure of aedes aegypti diptera culicidae
Memorias Do Instituto Oswaldo Cruz, 2002Co-Authors: Desiely Silva Gusmao, Raimundo Brazfilho, Valeria Pascoa, Leda Mathias, Ivo Jose Curcino Vieira, Francisco Jose Alves LemosAbstract:Aqueous suspension of ethanol extracts of Derris (Lonchocarpus) urucu (Leguminosae), collected in the state of Amazonas, Brazil, were tested for larvicidal activity against the mosquito Aedes aegypti (Diptera:Culicidae). The aim of this study was to observe the alterations of peritrophic Matrix in Ae. aegypti larvae treated with an aqueous suspension of D. urucu extract. Different concentrations of D. urucu root extract were tested against fourth instar larvae. One hundred percent mortality was observed at 150 microg/ml (LC(50) 17.6 microg/ml) 24 h following treatment. In response to D. urucu feeding, larvae excreted a large amount of amorphous feces, while control larvae did not produce feces during the assay period. Ultrastructural studies showed tha larvae fed with 150 microg/ml of D. urucu extract for 4 h have an imperfect peritrophic Matrix and extensive damage of the midgut epithelium. Data indicate a protective role for the peritrophic Matrix. The structural modification of the peritrophic Matrix is intrinsically associated with larval mortality.