558 research outputs found
Evaluation of Direct and Indirect Methods of Repairing Fractured
INTRODUCTION: The most common technology used in producing a fixed partial denture is firing porcelain to metal. The fracture of veneering material rarely occurs, although it is one of the most striking problems in daily practise.
PURPOSE: The purpose of this study was to evaluate the shear bond strength of composite to porcelain and metal by using two intraoral repair methods: direct and indirect.
MATERIAL AND METHODS: The direct method was performed by using Ceramic Repair System (Ivoclar, Lichtenstein) with and without sandblasting. The indirect method involved Co-Jet system (ESPE,Germany) and Rely X ARC (3M,USA) as luting agents. 180 specimens fabricated with feldspathic porcelain and Ni-Cr alloy
were divided into 3 groups: CR/0 (direct method of repair without sandblasting), CR/S (direct method of repair with sandblasting) and CJ (indirect method based on Co-Jet system). Each of them was divided into 3 subgroups of 20: porcelain (P), porcelain and metal (P/M) and metal (M). The 10 specimens were then subjected to a shear test in a mechanical testing machine at a crosshead speed of
0.5 mm/min. Mode of failure was recorded. Means and standart deviations of loads were calculated.
RESULTS: Tested groups exhibited the following values in megapascals: CR/0-P = 20.36 ± 3.05; CR/0-P/M = 19.45 ± 3.49; CR/0-M = 10.86 ± 4.1; CR/S-P = 18.21 ± 2.62; CR/S-P/M = 19.34 ± 1.76; CR/S-M = 9,54 ± 2.48; CJ-P = 19.85 ± 1.94; CJ-P/M = 19,78 ± 3.60; CJ-M = 13.56 ± 3.82. The mean fractured loads were significantly lower for metal subgroups than for porcelain and porcelain/ metal subgroups.
CONCLUSION: Higher shear bond strength is expected when porcelain was fractured without extensive metal exposure
Evaluation of Direct and Indirect Methods of Repairing Fractured
INTRODUCTION: The most common technology used in producing a fixed partial denture is firing porcelain to metal. The fracture of veneering material rarely occurs, although it is one of the most striking problems in daily practise.
PURPOSE: The purpose of this study was to evaluate the shear bond strength of composite to porcelain and metal by using two intraoral repair methods: direct and indirect.
MATERIAL AND METHODS: The direct method was performed by using Ceramic Repair System (Ivoclar, Lichtenstein) with and without sandblasting. The indirect method involved Co-Jet system (ESPE,Germany) and Rely X ARC (3M,USA) as luting agents. 180 specimens fabricated with feldspathic porcelain and Ni-Cr alloy
were divided into 3 groups: CR/0 (direct method of repair without sandblasting), CR/S (direct method of repair with sandblasting) and CJ (indirect method based on Co-Jet system). Each of them was divided into 3 subgroups of 20: porcelain (P), porcelain and metal (P/M) and metal (M). The 10 specimens were then subjected to a shear test in a mechanical testing machine at a crosshead speed of
0.5 mm/min. Mode of failure was recorded. Means and standart deviations of loads were calculated.
RESULTS: Tested groups exhibited the following values in megapascals: CR/0-P = 20.36 ± 3.05; CR/0-P/M = 19.45 ± 3.49; CR/0-M = 10.86 ± 4.1; CR/S-P = 18.21 ± 2.62; CR/S-P/M = 19.34 ± 1.76; CR/S-M = 9,54 ± 2.48; CJ-P = 19.85 ± 1.94; CJ-P/M = 19,78 ± 3.60; CJ-M = 13.56 ± 3.82. The mean fractured loads were significantly lower for metal subgroups than for porcelain and porcelain/ metal subgroups.
CONCLUSION: Higher shear bond strength is expected when porcelain was fractured without extensive metal exposure
Another note on Kempisty's generalized continuity
Under a fairly mild completeness condition on spaces Y and Z we show that every x-continuous function f:XĂYĂZâM has a substantial set C(f) of points of continuity. Some odds and ends concerning a related earlier result shown by the authors are presented. Further, a generalization of S. Kempisty's ideas of generalized continuity on products of finitely many spaces is offered. As a corollary from the above results, a partial answer to M. Talagrand's problem is provided
Agent-based interoperability for e-government
The provision of valuable e-government services depends upon the capacity to integrate the disperse provision of services by the public administration and thus upon the availability of interoperability platforms. These platforms are commonly built according to the principles of service oriented architectures, which raise the question of how to dynamically orchestrate services while preserving information security. Recently, it was presented an e-government interoperability model that preserves privacy during the dynamic orchestration of services. In this paper we present a prototype that implements that model using software agents. The model and the prototype are briefly described; an illustrative use case is presented; and the advantages of using software agents to implement the model are discussed. © Springer International Publishing Switzerland 2013
FVM 1.0: a nonhydrostatic finite-volume dynamical core for the IFS
We present a nonhydrostatic finite-volume global atmospheric model
formulation for numerical weather prediction with the Integrated Forecasting
System (IFS) at ECMWF and compare it to the established operational
spectral-transform formulation. The novel Finite-Volume Module of the IFS
(henceforth IFS-FVM) integrates the fully compressible equations using
semi-implicit time stepping and non-oscillatory forward-in-time (NFT)
Eulerian advection, whereas the spectral-transform IFS solves the hydrostatic
primitive equations (optionally the fully compressible equations) using a
semi-implicit semi-Lagrangian scheme. The IFS-FVM complements the
spectral-transform counterpart by means of the finite-volume discretization
with a local low-volume communication footprint, fully conservative and
monotone advective transport, all-scale deep-atmosphere fully compressible
equations in a generalized height-based vertical coordinate, and flexible
horizontal meshes. Nevertheless, both the finite-volume and
spectral-transform formulations can share the same quasi-uniform horizontal
grid with co-located arrangement of variables, geospherical
longitudeâlatitude coordinates, and physics parameterizations, thereby
facilitating their comparison, coexistence, and combination in the IFS.
We highlight the advanced semi-implicit NFT finite-volume integration of the
fully compressible equations of IFS-FVM considering comprehensive
moist-precipitating dynamics with coupling to the IFS cloud parameterization
by means of a generic interface. These developments â including a new
horizontalâvertical split NFT MPDATA advective transport scheme, variable
time stepping, effective preconditioning of the elliptic Helmholtz solver in
the semi-implicit scheme, and a computationally efficient implementation of
the median-dual finite-volume approach â provide a basis for the efficacy of
IFS-FVM and its application in global numerical weather prediction. Here,
numerical experiments focus on relevant dry and moist-precipitating
baroclinic instability at various resolutions. We show that the presented
semi-implicit NFT finite-volume integration scheme on co-located meshes of
IFS-FVM can provide highly competitive solution quality and computational
performance to the proven semi-implicit semi-Lagrangian integration scheme of
the spectral-transform IFS.</p
GRB 080319B: A Naked-Eye Stellar Blast from the Distant Universe
Long duration gamma-ray bursts (GRBs) release copious amounts of energy
across the entire electromagnetic spectrum, and so provide a window into the
process of black hole formation from the collapse of a massive star. Over the
last forty years, our understanding of the GRB phenomenon has progressed
dramatically; nevertheless, fortuitous circumstances occasionally arise that
provide access to a regime not yet probed. GRB 080319B presented such an
opportunity, with extraordinarily bright prompt optical emission that peaked at
a visual magnitude of 5.3, making it briefly visible with the naked eye. It was
captured in exquisite detail by wide-field telescopes, imaging the burst
location from before the time of the explosion. The combination of these unique
optical data with simultaneous gamma-ray observations provides powerful
diagnostics of the detailed physics of this explosion within seconds of its
formation. Here we show that the prompt optical and gamma-ray emissions from
this event likely arise from different spectral components within the same
physical region located at a large distance from the source, implying an
extremely relativistic outflow. The chromatic behaviour of the broadband
afterglow is consistent with viewing the GRB down the very narrow inner core of
a two-component jet that is expanding into a wind-like environment consistent
with the massive star origin of long GRBs. These circumstances can explain the
extreme properties of this GRB.Comment: 43 pages, 18 figures, 3 tables, submitted to Nature May 11, 200
Reversed flow of Atlantic deep water during the Last Glacial Maximum
The meridional overturning circulation (MOC) of the Atlantic Ocean is considered to be one of the most important components of the climate system. This is because its warm surface currents, such as the Gulf Stream, redistribute huge amounts of energy from tropical to high latitudes and influence regional weather and climate patterns, whereas its lower limb ventilates the deep ocean and affects the storage of carbon in the abyss, away from the atmosphere. Despite its significance for future climate, the operation of the MOC under contrasting climates of the past remains controversial. Nutrient-based proxies1, 2 and recent model simulations3 indicate that during the Last Glacial Maximum the convective activity in the North Atlantic Ocean was much weaker than at present. In contrast, rate-sensitive radiogenic 231Pa/230Th isotope ratios from the North Atlantic have been interpreted to indicate only minor changes in MOC strength4, 5, 6. Here we show that the basin-scale abyssal circulation of the Atlantic Ocean was probably reversed during the Last Glacial Maximum and was dominated by northward water flow from the Southern Ocean. These conclusions are based on new high-resolution data from the South Atlantic Ocean that establish the basin-scale north to south gradient in 231Pa/230Th, and thus the direction of the deep ocean circulation. Our findings are consistent with nutrient-based proxies and argue that further analysis of 231Pa/230Th outside the North Atlantic basin will enhance our understanding of past ocean circulation, provided that spatial gradients are carefully considered. This broader perspective suggests that the modern pattern of the Atlantic MOCâwith a prominent southerly flow of deep waters originating in the North Atlanticâarose only during the Holocene epoch
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