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.     

ON APPROXIMATION PROPERTIES OF NON-CONVOLUTION TYPE NONLINEAR INTEGRAL OPERATORS-Dedicated to Professor Paul L. Butzer on his 80th Birthday

In the present paper we state some approximation theorems concerning point- wise convergence and its rate for a class of non-convolution type nonlinear integral opera- tors of the form：Tλ（f;x）=B∫AKλ（t,x,f（t））dr,x∈〈a,b〉λλA.In particular, we obtain the pointwise convergence and its rate at some characteristic points x0 off as （x,λ） → （x0, λ0） in LI 〈A,B 〉, where 〈 a,b 〉 and 〈A,B 〉 are is an arbitrary intervals in R, A is a non-empty set of indices with a topology and X0 an accumulation point of A in this topology. The results of the present paper generalize several ones obtained previously in the papers [191-[23]     

17-channels S band multiwavelength Brillouin/Erbium Fiber Laser co-pump with Raman source

In this paper, we propose and demonstrate a stable Brillouin-Erbium Fibre Laser (BEFL) capable of generating up to 17 lasing wavelengths in the Short-Wave length (S-band) region. The proposed setup uses a 7.7 km Dispersion Compensating Fibre (DCF) to act as a non-linear gain medium and a 30 m long Depressed-Cladding Erbium Doped Fibre (DC-EDF) as an optical amplifier for amplification in the S-band region. The proposed BEFL has an optimum tuning range of 1499 to 1502 nm and is capable of generating 17 lasing wavelengths with peak powers of between −20 to −15 dBm when injected with a Brillouin Pump (BP) of 5 dBm at 1499 nm and a Raman Pump (RP) of 300 mW at 1420 nm.     

Retract-collapsible graphs and invariant subgraph properties

A (finite or infinite) graph G is retract-collapsible if it can be dismantled by deleting systematically at each step every vertex that is strictly dominated, in such a way that the remaining subgraph is a retract of G, and so as to get a simplex at the end. A graph is subretract-collapsible if some graph obtained by planting some rayless tree at each of its vertices is retract-collapsible. It is shown that the subretract-colapsible graphs are cop-win; and that a ball-Helly graph is subretract-collapsible if and only if it has no isometric infinite paths (thus in particular if it has no infinite paths, or if it is bounded). Several fixed subgraph properties are proved. In particular, if G is a subretract-collapsible graph, and f a contraction from G into G, then (i) if G has no infinite simplices, then f(S) = S for some simplex S of G; and (ii) if the dismantling of G can be achieved in a finite number of steps and if some family of simplices of G has a compacity property, then there is a simplex S of G such that f(S) ? S. This last result generalizes a property of bounded ball-Helly graphs. © 1995 John Wiley & Sons, Inc.     

Enhancement of Gain in L-Band Bismuth-Based Erbium-Doped Fibre Amplifier Using an Un-pumped EDF and Midway Isolator

A hybrid L-band erbium-doped fibre amplifier (EDFA) with enhanced gain characteristic is demonstrated without a significant noise figure penalty. It uses a backward C-band amplified stimulated emission from both the ends of a bismuth-based EDFA system to pump an unpumped erbium-doped fibre (EDF) for gain enhancing. The maximum gain enhancement of 4.0dB is obtained at wavelength 1604nm with EDF length of 20m. The gain spectrum is reasonably fiat in this amplifier compared with the amplifier without an EDF. The gain varies from 27.4 dB to 30.2 dB at wavelength region 1564-1608 nm with incorporation of 20 m EDF. Noise figure also varies from 6.0 to 7.TdB at this wavelength region.     

A Partial Double-Pass S-Band Erbium-Doped Fibre Amplifier

An efficient and low noise short wavelength band erbium-doped fibre amplifier （S-band EDFA） is proposed and demonstrated using double-pass configuration. This amplifier provides a gain of 1500 nm signal as high as 26.9 dB, which is 9.6 dB higher than the two-stage single-pass amplifier. The corresponding noise figure obtained is 7.5 dB, which is of the same level as in the single-pass amplifier and more than 2 dB lower than the previously reported double-pass amplifier [IEIOE Electron. Express 2 （2005） 182]. The gain enhancement is due to the double pass-propagation of the test signal in the second stage, which increases the effective erbium-doped fibre （EDF） length. The low noise is attributed to the optical circulator between EDFs, which prevents the backward amplified spontaneous emission from propagating into the input part of the amplifier. The proposed amplifier is expected to play an important role in the development of a practical S-band EDFA.     

An efficient S-band brillouin erbium fiber laser with additional EDFA

A short wavelength band brillouin–erbium fiber laser (S-band BEFL) with enhanced characteristics is demonstrated using an additional erbium-doped fiber amplifier (EDFA) in the sub-loop of the laser system. Compared with the conventional BEFL without the additional EDFA, the enhanced BEFL has improved the number of channels as well as the flatness of the brillouin Stoke's peak power. By incorporating a double-pass EDFA, a stable output laser comb up to 8 channels was obtained at 1503 nm wavelength region with peak power variation for the first three Stokes is reduced from 30.9 to 5.4 dB. The incorporation of additional EDFA also increases the tuning range of the BEFL, which the maximum tuning range of 1.8 nm was obtained with the single-pass scheme. The S-band BEFL has constant spacing of 0.09 nm or 11 GHz, which has a potential application in dense wavelength division multiplexed system.     

Couplages et transversaux généralisés d'un hypergraphe infini

Let $\text{A}$ be a hypergraph possibly infinite but whose edges are finite sets. An s-transversal of $\text{A}$ is a set of vertices of $\text{A}$ whose intersection with each edge A has a power greater than or equal to some cardinal s(A). Three successively stronger kinds of matchings of $\text{A}$ are defined: the s-maximal, the strongly s-maximal, and the s-perfect matchings. The first two generalize matchings of maximal cardinality, whereas a matching $\text{C}$ is s-perfect iff $\text{A}$ has an s-transversal T with T ? ∪ $\text{C}$ and |T ∩ C| = s(C) for every C ∈ $\text{C}$. Several classes of hypergraphs having strongly s-maximal or s-perfect matchings are characterized.