Influence of the hybrid layer thickness and resin tag length on microtensile bond strength.

The purpose of this study was to evaluate the correlation between the hybrid layer thickness/resin tag length and the microtensile bond strength of conventional two-step adhesive system, when applied to healthy dentinal tissue. After performing the restorative adhesive procedures and tooth extractions, ten specimens were sectioned in the mesiodistal direction. One section was used for microscopic analysis of the resin tag lengths and the hybrid layer thickness, while the other was used for the microtensile bond strength test (0.5 mm/min). The fractured surface was classified according to the fracture pattern, under a stereoscopic microscope at 40x magnification. Data obtained were submitted to analysis using one-way ANOVA and Pearson's Correlation test (alpha=0.05). The means corresponding to the hybrid layer thickness, resin tag lengths and the microtensile test were 2.68 microm, 6.43 microm and 16.23 MPa, respectively. There was no correlation between the means of the values obtained for the microtensile test, and those presented by the hybrid layer (r2=0.40, p>0.05) and resin tags (r2=0.21, p>0.05). The microtensile bond strength of the conventional two-step adhesive system Adper Single Bond 2 did not depend on the thickness of the hybrid layer and length of resin tags.

The production of statistical data and information in the Caribbean: proposals for increasing efficiency in this sphere

Includes bibliography

Electron reconstruction and identification efficiency measurements with the ATLAS detector using the 2011 LHC proton-proton collision data

Many of the interesting physics processes to be measured at the LHC have a signature involving one or more isolated electrons. The electron reconstruction and identification efficiencies of the ATLAS detector at the LHC have been evaluated using proton–proton collision data collected in 2011 at √s = 7 TeV and corresponding to an integrated luminosity of 4.7 fb−1. Tag-and-probe methods using events with leptonic decays of W and Z bosons and J/ψ mesons are employed to benchmark these performance parameters. The combination of all measurements results in identification efficiencies determined with an accuracy at the few per mil level for electron transverse energy greater than 30 GeV.

Strontium concentrations and isotopic compositions of anhydrites from the TAG active mound

Sr isotope analyses have been conducted on anhydrite samples from the TAG (Trans-Atlantic Geotraverse) active hydrothermal mound (26°08?N, Mid-Atlantic Ridge) that have previously been shown to exhibit two distinct patterns of REE behavior when normalized to TAG end-member hydrothermal fluid. Despite differences in REE patterns, the Sr isotope data indicate that all the anhydrites precipitated from fluids with a similar range of hydrothermal fluid and seawater components, and all but one were seawater-dominated (52%-75%). Speciation calculations using the EQ3/6 software package for geochemical modeling of aqueous systems suggest that the REE complexation behavior in different fluid mixing scenarios can explain the variations in the REE patterns. Anhydrites that exhibit relatively flat REE patterns [(La_bs)/(Yb_bs) = 0.8-2.0; subscript bs indicates normalization to end-member black smoker hydrothermal fluid] and a small or no Eu anomaly [(Eu_bs)/(Eu*_bs) = 0.8-2.0] are inferred to have precipitated from mixes of end-member hydrothermal fluid and cold seawater. REE complexes with hard ligands (e.g., fluoride and chloride) are less stable at low temperatures and trivalent Eu has an ionic radius similar to that of Ca2+ and the other REE, and so they behave coherently. In contrast, anhydrites that exhibit slight LREE-depletion [(La_bs)/(Yb_bs) = 0.4-1.4] and a distinct negative anomaly [(Eu_bs)/(Eu*_bs) = 0.2-0.8] are inferred to have precipitated from mixes of end-member hydrothermal fluid and conductively heated seawater. The LREE depletion results from the presence of very stable LREE chloro-complexes that effectively limit the availability of the LREE for partitioning into anhydrite. Above 250°C, Eu is present only in divalent form as chloride complexes, and discrimination against Eu2+ is likely due to both the mismatch in ionic radii between Eu2+ and Ca2+, and the strong chloro-complexation of divalent Eu which promotes stability in the fluid and inhibits partitioning of Eu2+ into precipitating anhydrite. These variations in REE behavior attest to rapid fluctuations in thermal regime, fluid flow and mixing in the subsurface of the TAG mound that give rise to heterogeneity in the formation conditions of individual anhydrite crystals.

Composition of particulate matter in the neutrally buoyant plumes of the TAG and Broken Spur Hydrothermal Fields

This publication considers data on aquatic anomalies (hydrothermal plumes) in the areas of 26° and 29°N of the Mid-Atlantic Ridge (MAR). Mass of hydrothermal iron supply and intensity of iron sedimentation onto the bottom were estimated by means of sediment traps. It was found that the plume of the TAG hydrothermal vent 6 km**3 in volume contained about 67 tons of particulate Fe; the plume of the Broken Spur field (up to 8.24 km**3 in volume) contained 23.5 tons of particulate Fe or less because of its lower concentration. Data on sediment matter fluxes showed that 0.3-0.5% of hydrothermal iron was precipitated immediately from the neutrally buoyant plume onto the bottom; the bulk of iron was dissipated into environment. From dimensions of the plumes, flow dynamics, iron concentrations in the plumes, and amounts of iron supplied by hydrothermal vents, it was found that resident time of the plumes considered was from 5 to 10 days.

Composition of dissolved, particulate and sinking material in hydrothermal plumes above the TAG and Broken Spur hydrothermal fields

The paper reports data on distribution of dissolved (Mn, Zn, Cu, Pb, and Cd) and particulate (Fe, Mn, Zn, Cu, Pb, Ni, and Co) species of metals in hydrothermal plumes above the active TAG and Broken Spur hydrothermal fields (26° N and 29° N in the MAR rift valley, respectively). Sediment trap data on fluxes of hydrothermal sedimentary material in the areas indicate that (i) the predominant Zn source for metalliferous sediments at the TAG field is material precipitating from the neutrally buoyant plume, and (ii) the predominant source of Fe and Co is re-deposited ore material coming from the area of extensive settling of sulfides.

Noble metals and associated trace elements in sulfides from the active TAG mound, ODP Site 158-957

Primary sulfides from cores of ODP Holes 158-957M, 158-957C, and 158-957H on the active TAG hydrothermal mound (Mid-Atlantic Ridge, 26°08'N) have been studied for concentrations of several chemical elements. Based on 262 microprobe analyses it has been found that the sulfides have extremely heterogeneous distribution of noble metals (Au, Ag, Pt, and Pd) and several associated elements (Hg, Co, and Se). Noble metals are arranged in the following order in terms of decreasing abundance, i.e. concentration level above detection limits (the number of analyses containing a specific element is given in parentheses): Au (65), Ag (46), Pt (21), and Pd (traces). The associated trace elements have the following series: Co (202), Hg (132), and Se (49). The main carriers of "invisible" portion of the noble metals are represented by pyrite (Au, Hg), marcasite and pyrite (Ag, Co), sphalerite and chalcopyrite (Pt, Pd), and chalcopyrite (Se). Noble metal distribution in sulfides reveals a lateral zonality: maximal concentrations and abundance of Au in chalcopyrite (or Pt and Ag in chalcopyrite and pyrite) increase from the periphery (Hole 957H) to the center (holes 957C and 957M) of the hydrothermal mound, while Au distribution in pyrite displays a reversed pattern. Co concentration increases with depth. Vertical zonality in distribution of the elements mentioned above and their response to evolution of ore genesis are under discussion in the paper.