Effect of various treatment and glazing (coating) techniques on the roughness and wettability of ceramic dental restorative surfaces

Surface treatment procedures such as grinding and polishing are needed to provide the ceramic dental restorative materials with proper fitting and occlusion. The treated surfaces are customarily glazed to improve the strength and smoothness. Though smoothness and wetting of the dental surfaces are important to minimize bacterial plaque retention, influence of the surface treatment and glazing procedures on the final surface roughness and its correlation to wettability are overlooked.

In this work, effect of various treatment (diamond fraising, stoning, sanding and aluminum oxide and rubber polishing) and glazing (auto and overglazing) techniques on the final roughness and the resulting wettability of dental ceramic surfaces were investigated using scanning electron microscopy (SEM) observations and atomic force microscopy (AFM) scans, 75 scans per sample. The surfaces were characterized and assigned an average roughness measure, R_a. The wettability of the same surfaces was evaluated using micro-contact angle measurements (25 micro-bubbles placed on a grid on each surface) to correlate the final surface roughness and wettability.

The results show that overglazing prevails over surface irregularities from different treatment procedures and provides homegeneously smooth surfaces with mean R_a < 10 nm. It also produces uniformly wetted surfaces with low contact angles around 20°. The autoglazed surfaces are less smooth (mean R_a around 50 nm) and displays sporadic topographic irregularities. They display larger and less uniform contact angles ranging between 35° and 50°. The results suggest that overglazing should be preferred after surface treatment to obtain a smooth and well-wetted dental ceramic surface.     

Determination of K shell fluorescence cross-section and Kβ/Kα intensity ratios for Fe,Se, Te,FeSe, FeTe and TeSe

The fluorescence cross-sections (σ_Ki) and the intensity ratios K_β/K_α for pure Fe, Se, Te elements and FeSe, FeTe, TeSe complexes have been investigated. The samples were excited by 59.5 keV γ-rays from ²⁴¹Am annular radioactive source and emitted X-rays. They were counted by an Ultra-LEGe detector with resolution of 150 eV at 5.9 keV. For pure elements results have been compared with the theoretical calculated values. According to our results band length and mutual interaction of atoms affected the results. We claimed that these effects would help researchers who study on superconductors, especially determining which compound can be show the superconductor properties.     

QSAR based modeling on a series of α-hydroxy amides as a novel class of bradykinin B1 selective antagonists

G-protein coupled receptors like Bradykinin (BK) B₁ represent a potential treatment route for chronic pain and inflammation. Quantitative structure activity relationship has been performed on a series of α-hydroxy amides as a novel class of bradykinin B₁ selective antagonists, using different physicochemical parameters along with appropriate indicator variables. It has been found that physicochemical parameters such as connectivity indices ³χ, ⁴χ and ⁵χ, molecular weight, molar refractivity, density along with indicator variables are significantly correlated with activity. In this paper best results were obtained by using multiple regression analysis. Different models were generated with high values of R² and low values of PRESS/SSY ratio. The significant equations were statistically tested by using leave one out (LOO) technique and cross validation methods.     

Compression of CdCu3Ti4O12 perovskite to 55 GPa

Synchrotron x-ray diffraction measurements of CdCu₃Ti₄O₁₂ (CDCTO) were performed up to 55.5 GPa. There is no structural phase transformation in this pressure range. The irregular curvature shifts of the P-V curve are attributed to the grain surface effect. Analysis indicates that the grain surface of CDCTO is stiffer than the grain interior at higher pressures. We point out that the atoms on grain surfaces must be either densely packed or have a strong correlation with the gain interior in order to have a high dielectric constant, as in CaCu₃Ti₄O₁₂. The derived bulk modulus of CDCTO is approximately 235±7 GPa with K^′=5.1±0.4.     

Arithmetic Groups,Base Change,and Representation Growth

Consider an arithmetic group \({\mathbf{G}(O_S)}\), where \({\mathbf{G}}\) is an affine group scheme with connected, simply connected absolutely almost simple generic fiber, defined over the ring of S-integers O _S of a number field K with respect to a finite set of places S. For each \({n \in \mathbb{N}}\), let \({R_n(\mathbf{G}(O_S))}\) denote the number of irreducible complex representations of \({\mathbf{G}(O_S)}\) of dimension at most n. The degree of representation growth \({\alpha(\mathbf{G}(O_S)) = \lim_{n \rightarrow\infty}\log R_n(\mathbf{G}(O_S)) / \log n}\) is finite if and only if \({\mathbf{G}(O_S)}\) has the weak Congruence Subgroup Property. We establish that for every \({\mathbf{G}(O_S)}\) with the weak Congruence Subgroup Property the invariant \({\alpha(\mathbf{G}(O_S))}\) is already determined by the absolute root system of \({\mathbf{G}}\). To show this we demonstrate that the abscissae of convergence of the representation zeta functions of such groups are invariant under base extensions \({K{\subset}L}\). We deduce from our result a variant of a conjecture of Larsen and Lubotzky regarding the representation growth of irreducible lattices in higher rank semi-simple groups. In particular, this reduces Larsen and Lubotzky’s conjecture to Serre’s conjecture on the weak Congruence Subgroup Property, which it refines.     

Bounds on multiplicities of spherical spaces over finite fields

Let G be a reductive group scheme of type A acting on a spherical scheme X. We prove that there exists a number C such that the multiplicity $\dim \mathrm{Hom}(\rho ,\mathbb{C}[X(F)])$ is bounded by C, for any finite field F and any irreducible representation ρ of $G(F)$. We give an explicit bound for C. We conjecture that this result is true for any reductive group scheme and when F ranges (in addition) over all local fields of characteristic 0.Different aspects of this conjecture were studied in [3], [11], [6], [7].     

Soil radon monitoring and anomalies in East Anatolian Fault System (Turkey)

On-line monitoring of soil radon (²²²Rn) concentration system was constructed on one of the main active fault zone of East Anatolian Fault System (EAFS) in Turkey. The preliminary results, observed during the second part of 2004 and first part of 2005 is presented. During the monitoring of soil radon concentration, numerous anomalies that equal or twice standard deviation were observed. In addition, the variation of the radon concentration was examined between the mean values and plus/minus two standard deviations and any increase in radon concentration above this limit was assumed to be ²²²Rn anomalies. These anomalies usually appeared between a few days or weeks before the earthquakes occurrence. The obtained data were also compared as considered respect to the earthquakes occurred in a 100 km radius of the fault system.     

Diagnostics of microwave-induced plasmas and polymerization of gaseous hydrocarbons

The microwave plasmas of gaseous mixtures of methane-argon and propyleneargon were analyzed along the flow stream by the electrical double floating probe system, optical spectroscopy, and quadrupole mass spectrometry. The plasma variables measured and considered were current density, electric field strength, electron temperature, positive ion and electron concentrations, and concentration of pyrolyzed and polymerized species. The results indicate that an irreversible process of polymerization of the hydrocarbons takes place in the plasma. The polymerization process reaches its maximum conversion downstream beyond the microwave cavity. The extent of polymerization was correlated to the concentration of positive ions and electrons in the plasma.Presented in part at ISPC 4, Zurich, 1979, S. Veprek and J. Hertz, eds., Vol. II (University of Zurich, 1979), p. 390.