237 research outputs found
Parthenocissus tricuspidata: un modĂšle vĂ©gĂ©tal dâadhĂ©sion biologique
The Parthenocissus Tricuspidata, genus of the Vitaceae family, is a rustic plant with lianas, whose tendrils tips have organelles called adhesive discs that, set near a substrate, adhere to it.Studies of A.G. ENDRESS, W. THOMSON, S. JUNKER attribue the disc adhesion ability to an adhesive substance secretion instead of a suction mechanism.Teeth were set beneath the tendrils and in few weeks the adhesion to enamel, dentin and radicular cement was so strong as the usual adhesion to the wall, except with teeth that were set before in fluoride gel, because of the element cytotoxicity.Then the adhesion place was investigated with microanalysis and S.E.M.The microanalysis has shown calcium and phosphorus both on enamel and on adhesion place, while silicon, sulphur, chlorine and potassium were only on the adherent vegetable substance.The S.E.M. analysis was conducted on the enamel surface, after removing of the vegetable, and perpendicularly to the adhesion surface of the vegetable with the enamel, the dentin and the cementum.La Parthenocissus Tricuspidata, genre appartenant Ă la famille des AmpĂ©lidiacĂ©es, est une plante rustique, grimpante, pourvue de vrilles Ă lâextrĂ©mitĂ© desquelles se diffĂ©rencient des organes appelĂ©s disques adhĂ© ifs qui, au voisinage dâun substrat, adhĂšrent Ă celui-ci de façon tenace.Des Ă©tudes de A.G. ENDRESS, W. THOMSON, S. JUNKER nâattribuent pas tellement Ă ce disque la capacitĂ© dâadhĂ©rer au substrat avec un mĂ©canisme Ă ventouse mais plutĂŽt grĂące Ă la sĂ©crĂ©tion dâune substance adhĂ©sive.Les Ă©lĂ©ments dentaires ont Ă©tĂ© solidement fixĂ©s au-dessous des vrilles et au bout de quelques semaines lâadhĂ©sion sur lâĂ©mail, sur la dentine et sur le cĂ©ment radiculaire se rĂ©vĂšlait aussi tenace que lâadhĂ©sion qui se produit habituellement pour le cĂ©ment, Ă lâexception des Ă©lĂ©ments immergĂ©s auparavant dans un gel fluorĂ©, peut-ĂȘtre Ă cause de la cytotoxicitĂ© de lâĂ©lĂ©ment lui-mĂȘme.Le siĂšge de lâadhĂ©sion Ă lâĂ©mail a Ă©tĂ© ensuite soumis Ă deux types dâexamens: la microanalyse et la microscopie Ă©lectronique Ă balayage.La microanalyse a rĂ©vĂ©lĂ© la prĂ©sence de calcium et de phosphore aussi bien sur lâĂ©mail que sur la zone dâadhĂ©sion, alors que le silicium, le soufre, le chlore et le potassium ne se rencontrent que sur la substance vĂ©gĂ©tale adhĂ©rĂ©e.LâĂ©tude au M.E.B. a Ă©tĂ© effectuĂ©e soit sur la surface de lâĂ©mail, aprĂšs sĂ©paration du vĂ©gĂ©tal, soit sur la coupe orthogonale Ă la surface dâadhĂ©sion du vĂ©gĂ©tal Ă lâĂ©mail, Ă la dentine et au cĂ©ment radiculaire
High-temperature and high-pressure behavior of carbonates in the ternary diagram CaCO3-MgCO3-FeCO3
We report the thermal expansion and the compressibility of carbonates in the ternary compositional diagram CaCO3-MgCO3-FeCO3, determined by in situ X-ray powder and single-crystal diffraction. High-temperature experiments were performed by high-resolution X-ray synchrotron powder diffraction from ambient to decarbonation temperatures (25-850 \ub0C). Single-crystal synchrotron X ray diffraction experiments were performed in a variable pressure range (0-100 GPa), depending on the stability field of the rhombohedral structure at ambient temperature, which is a function of the carbonate composition. The thermal expansion increases from calcite, CaCO3, \u3b10 = 4.10(7)
710-5 K-1, to magnesite, MgCO3, \u3b10 = 7.04(2)
710-5 K-1. In the magnesite-siderite (FeCO3) join, the thermal expansion decreases as iron content increases, with an experimental value of \u3b10 = 6.44(4)
710-5 K-1 for siderite. The compressibility in the ternary join is higher (i.e., lower bulk modulus) in calcite and Mg-calcite [K0 = 77(3) GPa for Ca0.91Mg0.06Fe0.03(CO3)] than in magnesite, K0 = 113(1) GPa, and siderite, K0 = 125(1) GPa. The analysis of thermal expansion and compressibility variation in calcite-magnesite and calcite-iron-magnesite joins clearly shows that the structural changes associated to the order-disorder transitions [i.e., R3c calcite-type structure vs. R3 CaMg(CO3)2 dolomite-type structure] do not affect significantly the thermal expansion and compressibility of carbonate. On the contrary, the chemical compositions of carbonates play a major role on their thermo-elastic properties. Finally, we use our P-V-T equation of state data to calculate the unit-cell volume of a natural ternary carbonate, and we compare the calculated volumes to experimental observations, measured in situ at elevated pressure and temperatures, using a multi-anvil device. The experimental and calculated data are in good agreement demonstrating that the equation of state here reported can describe the volume behavior with the accuracy needed, for example, for a direct chemical estimation of carbonates based on experimental unit-cell volume data of carbonates at high pressures and temperatures
Party-group relations in new southern European democracies in the crisis era
UID/CPO/04627/2013
PTDC/IVC-CPO/1864/2014publishersversionpublishe
âEither Everyone Was Guilty or Everyone Was Innocentâ: The Italian Power Elite, Neopatrimonialism, and the Importance of Social Relations
Rarely does the Byzantine world of football administration get exposed as clearly as during the 2006 calciopoli scandal. This scandal laid bare the interpersonal relationships of football administrators at the top three Italian menâs football clubs: Juventus, Inter, and AC Milan. This article draws on the media leaks that revealed the inner workings of those working within football to argue that the football clubs are pyramids of power for club presidents that allows them to operate within the Italian power elite. This is done through interpersonal clientelistic networks that operate within a neopatrimonial system. Theoretically, this article draws on four main concepts: C. Wright Millsâs concept of the Power Elite, Lomnitzâs model of âPyramids of Power,â Eisenstadtâs notion of neopatrimonialism, and Maussâs utilization of the gift. Power is exercised through quid pro quo relationships, with certain key individuals operating as brokers to the flow of favors throughout the network
- âŠ