The aim of the present investigation was to compare the in vitro bacterial retention on saliva-coated implant materials (pure titanium grade 2 (cp-Ti) and a titanium alloy (Ti–6Al–4V) surfaces), presenting similar surface roughness, and to assess the influence of physico-chemical surface properties of bacterial strain and implant materials on in vitro bacterial adherence. Two bacterial strains (one hydrophilic strain and one hydrophobic strain) were used and the following were evaluated: bacterial cell adherence, SFE values as well as the Lifshitz-van-der Waals, the Lewis acid base components of SFE, the interfacial free energy and the non-dispersive interactions according to two complementary contact angle measurement methods: the sessile drop method and the captive bubble method.
Our results showed similar patterns of adherent bacterial cells on saliva-coated cp-Ti and saliva-coated Ti–6Al–4V. These findings could suggest that bacterial colonization (i.e. plaque formation) is similar on saliva-coated cp-Ti and Ti–6Al–4V surfaces and indicate that both materials could be suitable for use as transgingival abutment or healing implant components. The same physico-chemical properties exhibited by saliva-coated cp-Ti and TA6V, as shown by the sessile drop method and the captive bubble method, could explain this similar bacterial colonisation. Therefore, higher values of total surface free energy of saliva-coated cp-Ti and saliva-coated TA6V samples (γSV ≈65 mJ/m2) were reported using the captive bubble method indicating a less hydrophobic character of these surfaces than with the sessile drop method (γS ≈44.50 mJ/m2) and consequently possible differences in oral bacterial retention according the theory described by Absolom et al.
The number of adherent hydrophobic S. sanguinis cells was two-fold higher than that of hydrophilic S. constellatus cells. Our results confirm that physico-chemical surface properties of oral bacterial strains play a role in bacterial retention to implant materials in the presence of adsorbed salivary proteins. 相似文献
We rederive the Coulomb expansion of the electron gas average energy at finite temperature, starting from scratch, i.e., using only the framework of the grand canonical ensemble and not the finite-T Green's function formalism. We recover the analytical expressions of the exchange and correlation energy in both the high-T and theT=0 limits. We explicitly show the origin of the crossover of the correlation energy leading term frome4 lne2 at zero temperature toe3 at finiteT. We also discuss the relative importance of exchange and correlation in both limits. 相似文献
The net reaction of monomeric Cp'(2)CeH [Cp' = 1,3,4-(Me(3)C)(3)(C(5)H(2))] in C(6)D(6) with C(6)F(6) is Cp'(2)CeF, H(2), and tetrafluorobenzyne. The pentafluorophenylmetallocene, Cp'(2)Ce(C(6)F(5)), is formed as an intermediate that decomposes slowly to Cp'(2)CeF and C(6)F(4) (tetrafluorobenzyne), and the latter is trapped by the solvent C(6)D(6) as a [2+4] cycloadduct. In C(6)F(5)H, the final products are also Cp'(2)CeF and H(2), which are formed from the intermediates Cp'(2)Ce(C(6)F(5)) and Cp'(2)Ce(2,3,5,6-C(6)F(4)H) and from an unidentified metallocene of cerium and the [2+4] cycloadducts of tetra- and trifluorobenzyne with C(6)D(6). The hydride, fluoride, and pentafluorophenylmetallocenes are isolated and characterized by X-ray crystallography. DFT(B3PW91) calculations have been used to explore the pathways leading to the observed products of the exergonic reactions. A key step is a H/F exchange reaction which transforms C(6)F(6) and the cerium hydride into C(6)F(5)H and Cp'(2)CeF. This reaction starts by an eta(1)-F-C(6)F(5) interaction, which serves as a hook. The reaction proceeds via a sigma bond metathesis where the fluorine ortho to the hook migrates toward H with a relatively low activation energy. All products observed experimentally are accommodated by pathways that involve C-F and C-H bond cleavages. 相似文献
The configuration of various bicyclo[4.2.0]octanols has been established by 1H NMR spectroscopy, with Eu(dpm)3 as shift reagent. The intrinsic parameters Δ and K have been obtained and used as structural probes. Moreover, detailed data analysis showed that, contrary to the generally accepted concept, the vicinal coupling constant between trans cyclobutanic protons can be larger than that between cis protons. The chemical shifts obtained by 13C NMR spectroscopy are consistent with the proposed structures. The results have been extensively used to determine unambiguously the configuration of tricyclo[6.4.0.02,7]dodecanols and tricyclo[5.4.0.02,6]undecanol. 相似文献
The generally accepted mechanism of electrochromic phenomena into WO3 thin films involves the simultaneous injection of cations and electrons to form a tungsten bronze MxWO3, e.g. HxWO3,LixWO3. Electrochromic cells of the type ITO MO3/LiClO4(M) in propylene carbonate/Pt, where M = W or MO and MO3 is an amorphous thin film have been used. Different amounts of charges have been injected through these cells by electrochemical means at room temperature. The variations of the MO3 electrode potential with the injected charge are in good agreement with the assumption of the formation of LixMO3 compounds. The free enthalpies of formation of these bronzes have been calculated. The behavior of thin film electrodes seems to be intermediate between amorphous and crystallized bulky materials. Some measurements of electrode potential have also been carried out with crystallized thin films of sputtered WO3. 相似文献
Let G be a multigraph containing no minor isomorphic to or (where denotes without one of its edges). We show that the chromatic index of G is given by , where is the maximum valency of G and is defined as
(w(E(S)) being the number of edges in the subgraph induced by S). This result partially verifies a conjecture of Seymour [J. Combin. Theory (B) 31 (1981), pp. 82-94] and is actually a generalization
of a result proven by Seymour [Combinatorica 10 (1990), pp. 379-392] for series-parallel graphs. It is also equivalent to
the following statement: the matching polytope of a graph containing neither nor as a minor has the integer decomposition property.
Received January 10, 1997/Revised September 13, 1999
The author is also affiliated with GERAD (école des Hautes études Commerciales de Montréal). Her work was supported by Grant
OGP 0009126 from the Natural Sciences and Engineering Research Council of Canada (NSERC). 相似文献
The synthesis of new purine derivatives designed to inhibit cell cycle regulating cyclin‐dependent kinases (CDKs), is reported. These compounds, related to olomoucine and roscovitine, are characterised by the presence of apyrrolidine methanol substituent at C‐2 and a variety of ortho, meta and/or para substituents on the C‐6 arylamino group. 相似文献