The Experts below are selected from a list of 210 Experts worldwide ranked by ideXlab platform
Jessica Baron - One of the best experts on this subject based on the ideXlab platform.
-
real time rocks shader based Labradorite
International Conference on Computer Graphics and Interactive Techniques, 2018Co-Authors: Eric Patterson, Jessica BaronAbstract:Great assignments in computer graphics rock! Being slated to complete something concrete that engages interest and provokes solid personal development while not being completely set in stone is a monumental experience. Mining ideas for learning graphics, representing something visually complex such as Labradorite can be unearthed as a gem of an assignment, and one can learn a fragment of shading while procedurally chipping away at the assignment.
-
SIGGRAPH Educator's Forum - Real-time rocks: shader-based Labradorite
ACM SIGGRAPH 2018 Educator's Forum on - SIGGRAPH '18, 2018Co-Authors: Eric Patterson, Jessica BaronAbstract:Great assignments in computer graphics rock! Being slated to complete something concrete that engages interest and provokes solid personal development while not being completely set in stone is a monumental experience. Mining ideas for learning graphics, representing something visually complex such as Labradorite can be unearthed as a gem of an assignment, and one can learn a fragment of shading while procedurally chipping away at the assignment.
Wayne H Nesbitt - One of the best experts on this subject based on the ideXlab platform.
-
reactions of aqueous anions and cations at the Labradorite water interface coupled effects of surface processes and diffusion
Geochimica et Cosmochimica Acta, 1997Co-Authors: I J Muir, Wayne H NesbittAbstract:Abstract Incongruent dissolution of Labradorite in acidic solutions due to selective leaching of Na, Ca, and Al results in a leached surface layer enriched in Si. Preferential leaching extends several hundred angstroms below the mineral surface. SIMS profiles indicate that the depth from which Na, Ca, and Al are removed in advanced of Si depends not only on concentration but also on speciation of cations and anions in solution. Aqueous cations in acidic solution reduce leaching of Na, Ca, and Al relative to Si in the feldspar. On the other hand, certain anions in acidic solution enhance leaching of Na, Ca, and Al relative to Si. Dissolved cations can be adsorbed or complexed at Labradorite surfaces and formation of surface metal-ligand complexes facilitates detachment of cations from the surface. Increasing or decreasing dissolved cation concentrations in the vicinity of the mineral surface also affects chemical potential gradients between unleached Labradorite and the solid-solution interface, thereby either decreasing or increasing thickness of the leached layer. Labradorite surface chemistry and depth or volume of leaching reactions are discussed with reference to dissolved cations and anions in solution.
-
controls on differential leaching of calcium and aluminum from Labradorite in dilute electrolyte solutions
Geochimica et Cosmochimica Acta, 1992Co-Authors: I J Muir, Wayne H NesbittAbstract:Abstract Close inspection of SIMS (secondary ion mass spectrometry) depth profiles reveals that consistently greater amounts of Ca, relative to Al, are removed from Labradorite feldspar in response to dissolution in mildly acidic (pH 4) solutions of aqueous HCl. The result indicates that Ca and Al are removed from Labradorite at different rates and by implication, different reaction mechanisms. The cation concentration of the leachant solution affects the relative proportions of Ca and Al removed from the solid. In particular, dissolved Al decreases the relative amount of Al removed. By contrast, dissolved Ca has no observable effect on the relative release rates of Ca and Al; it is apparent that Ca is removed from the lattice in advance of Al. The explanation may be that hydrolysis of the Si-Al oxide network is dependent upon the initial exchange reaction between hydrogen ions from solution and the charge balancing cations (Na, Ca, and/or K) in the feldspar. Only after sufficient protons have penetrated the Si-Al oxide framework will the framework metals (Al and/or Si) be released in substantial quantity. From this interpretation, it follows that cations in solution which diffuse into the lattice and exchange with the charge balancing cations may affect the rate of hydrolysis of the feldspar network.
H W Nesbitt - One of the best experts on this subject based on the ideXlab platform.
-
early development of al ca and na compositional gradients in Labradorite leached in ph 2 hcl solutions
Geochimica et Cosmochimica Acta, 2001Co-Authors: H W Nesbitt, William SkinnerAbstract:Abstract Labradorite reacted with HCl solution (pH = 2.0) develops leached layers extending to about 500 A depth after 12 h leaching, and to 1500 A depth after 143 h leaching. Accurate Al, Ca, and Na compositional depth profiles were measured using x-ray photoelectron spectroscopy (XPS), with compositional accuracy of about 10% and depth resolution of about 50 A. XPS analyses of pristine K-feldspar and Labradorite surfaces yield Ca, Al, Si, and O analyses within about 5% of electron microprobe results. Alkali element analyses are inaccurate due to preferential sputtering or mobility induced by fracture. The accurate compositional depth profiles yield well constrained diffusion coefficients and moving boundary velocities for Ca and Al. Na, Ca, and Al compositional gradients change character after about 2 days of leaching, from a convex upward hyperboloid to a sigmoid shape. Thereafter, the feldspar diffusion front is clearly separated from the surface (where silica dissolution occurs), with the diffusion front migrating into the feldspar at about 4 × 10−11 cm/s. Al diffuses down the compositional gradient at about 2.5 × 10−17 cm2/s and Ca diffuses almost twice as fast (4.0 × 10−17 cm2/s). The solution–solid interface and active leaching zone are separated (after 2 days) by a Si-rich zone virtually devoid of Na, Ca, and Al. Diffusion rates through this Si-rich overlayer may be very rapid and approach rates observed in aqueous solutions. Diffusive release of Ca and Al from Labradorite cannot be modelled accurately with mathematical solutions where diffusion through homogeneous media is assumed. During leaching, Ca and Al apparently diffuse by “jumping” to, and residing on, previously vacated structural sites of the feldspar. The probability of Ca and Al migrating towards solution consequently is greater than their probability of migrating towards pristine plagioclase, primarily because there are many more “vacant” sites in the leached zone than in pristine plagioclase. Diffusion is inhomogeneous and “impeded” in the direction of the pristine feldspar.
-
effects of aqueous cations on the dissolution of Labradorite feldspar
Geochimica et Cosmochimica Acta, 1991Co-Authors: I J Muir, H W NesbittAbstract:Specimens of Labradorite feldspar (An {approx} 54) were dissolved in mildly acidic solutions containing the cations Al, Ca, and Mg at 9.3 {times} 10{sup {minus}3}, 1.9 {times} 10{sup {minus}2}, and 3.7 {times} 10{sup {minus}2} mmol {center dot} L{sup {minus}1} for 72 days at 21 {plus minus} 2C and atmospheric pressure. Depth profiles by secondary ion mass spectrometry (SIMS) show that the extent to which altered layers form on dissolving Labradorite can be influenced by the cation concentration of the leachant solutions. Silicon-enriched altered layers {approx} 1,500 {angstrom} thick form on Labradorite surfaces ((001) cleavage faces) during dissolution in aqueous HCl (pH 4). Addition of dissolved Al, Ca, and Mg to the leachant solution reduces the thickness of the altered layers. The formation of thinner altered layers may result from competition between cations and H ions for active surface sites such that the supply of H ions to the Labradorite surface is reduced. Dissolved Al in the leachant solutions also alters the release rates of Ca and Al relative to one another. On the other hand, the same is not observed for Labradorite specimens dissolved in solutions containing Ca{sub (aq)}. The results from these experiments also support a diffusion-limited processes formore » the release of Al from fresh Labradorite to solutions containing Al{sub (aq)}. Previous attention has been focused on the effects of organic ligands; however, the results demonstrate the important role dissolved cations play in the dissolution of aluminosilicates.« less
-
Congruent and incongruent dissolution of Labradorite in dilute, acidic salt solutions
The Journal of Geology, 1991Co-Authors: H W Nesbitt, N. D. Macrae, William ShotykAbstract:Polished (001) cleavage faces of Nain Labradorite ($$An \approx 56$$) were leached at 20°C ($$\pm 2^{\circ}$$) for 72 days in distilled water ($$pH \approx 5.6$$), in HCl solution ($$pH \approx 4.05$$) and in four other HCl solutions containing 1 mg/l or less of Na, K, Ca, Al(aq), and $$SiO_{2}(aq)$$ ($$pH of all four solutions \approx 4.05$$). Analysis of the cleavage faces by Secondary Ion Mass Spectrometry (SIMS) revealed no residual surface layer on faces leached by distilled water. By contrast, thick Si-rich residual layers (1500 A) formed on surfaces leached by pure HCl solutions. Much thinner residual layers (700 A) were observed on Labradorite leached by HCl solutions containing 1 mg/l of Na, Ca, and K, whereas leached layers
-
congruent and incongruent dissolution of Labradorite in dilute acidic salt solutions
The Journal of Geology, 1991Co-Authors: H W Nesbitt, N. D. Macrae, William ShotykAbstract:Polished (001) cleavage faces of Nain Labradorite ($$An \approx 56$$) were leached at 20°C ($$\pm 2^{\circ}$$) for 72 days in distilled water ($$pH \approx 5.6$$), in HCl solution ($$pH \approx 4.05$$) and in four other HCl solutions containing 1 mg/l or less of Na, K, Ca, Al(aq), and $$SiO_{2}(aq)$$ ($$pH of all four solutions \approx 4.05$$). Analysis of the cleavage faces by Secondary Ion Mass Spectrometry (SIMS) revealed no residual surface layer on faces leached by distilled water. By contrast, thick Si-rich residual layers (1500 A) formed on surfaces leached by pure HCl solutions. Much thinner residual layers (700 A) were observed on Labradorite leached by HCl solutions containing 1 mg/l of Na, Ca, and K, whereas leached layers <75 A thick formed on faces leached by solutions containing 1 mg/l each of Na, K, Ca, Al(aq) and Si(aq); consequently incongruent dissolution of feldspars occurs in HCl solution, but congruent dissolution of feldspars occurs in mixed electrolyte solutions in which dissolved c...
I J Muir - One of the best experts on this subject based on the ideXlab platform.
-
reactions of aqueous anions and cations at the Labradorite water interface coupled effects of surface processes and diffusion
Geochimica et Cosmochimica Acta, 1997Co-Authors: I J Muir, Wayne H NesbittAbstract:Abstract Incongruent dissolution of Labradorite in acidic solutions due to selective leaching of Na, Ca, and Al results in a leached surface layer enriched in Si. Preferential leaching extends several hundred angstroms below the mineral surface. SIMS profiles indicate that the depth from which Na, Ca, and Al are removed in advanced of Si depends not only on concentration but also on speciation of cations and anions in solution. Aqueous cations in acidic solution reduce leaching of Na, Ca, and Al relative to Si in the feldspar. On the other hand, certain anions in acidic solution enhance leaching of Na, Ca, and Al relative to Si. Dissolved cations can be adsorbed or complexed at Labradorite surfaces and formation of surface metal-ligand complexes facilitates detachment of cations from the surface. Increasing or decreasing dissolved cation concentrations in the vicinity of the mineral surface also affects chemical potential gradients between unleached Labradorite and the solid-solution interface, thereby either decreasing or increasing thickness of the leached layer. Labradorite surface chemistry and depth or volume of leaching reactions are discussed with reference to dissolved cations and anions in solution.
-
controls on differential leaching of calcium and aluminum from Labradorite in dilute electrolyte solutions
Geochimica et Cosmochimica Acta, 1992Co-Authors: I J Muir, Wayne H NesbittAbstract:Abstract Close inspection of SIMS (secondary ion mass spectrometry) depth profiles reveals that consistently greater amounts of Ca, relative to Al, are removed from Labradorite feldspar in response to dissolution in mildly acidic (pH 4) solutions of aqueous HCl. The result indicates that Ca and Al are removed from Labradorite at different rates and by implication, different reaction mechanisms. The cation concentration of the leachant solution affects the relative proportions of Ca and Al removed from the solid. In particular, dissolved Al decreases the relative amount of Al removed. By contrast, dissolved Ca has no observable effect on the relative release rates of Ca and Al; it is apparent that Ca is removed from the lattice in advance of Al. The explanation may be that hydrolysis of the Si-Al oxide network is dependent upon the initial exchange reaction between hydrogen ions from solution and the charge balancing cations (Na, Ca, and/or K) in the feldspar. Only after sufficient protons have penetrated the Si-Al oxide framework will the framework metals (Al and/or Si) be released in substantial quantity. From this interpretation, it follows that cations in solution which diffuse into the lattice and exchange with the charge balancing cations may affect the rate of hydrolysis of the feldspar network.
-
effects of aqueous cations on the dissolution of Labradorite feldspar
Geochimica et Cosmochimica Acta, 1991Co-Authors: I J Muir, H W NesbittAbstract:Specimens of Labradorite feldspar (An {approx} 54) were dissolved in mildly acidic solutions containing the cations Al, Ca, and Mg at 9.3 {times} 10{sup {minus}3}, 1.9 {times} 10{sup {minus}2}, and 3.7 {times} 10{sup {minus}2} mmol {center dot} L{sup {minus}1} for 72 days at 21 {plus minus} 2C and atmospheric pressure. Depth profiles by secondary ion mass spectrometry (SIMS) show that the extent to which altered layers form on dissolving Labradorite can be influenced by the cation concentration of the leachant solutions. Silicon-enriched altered layers {approx} 1,500 {angstrom} thick form on Labradorite surfaces ((001) cleavage faces) during dissolution in aqueous HCl (pH 4). Addition of dissolved Al, Ca, and Mg to the leachant solution reduces the thickness of the altered layers. The formation of thinner altered layers may result from competition between cations and H ions for active surface sites such that the supply of H ions to the Labradorite surface is reduced. Dissolved Al in the leachant solutions also alters the release rates of Ca and Al relative to one another. On the other hand, the same is not observed for Labradorite specimens dissolved in solutions containing Ca{sub (aq)}. The results from these experiments also support a diffusion-limited processes formore » the release of Al from fresh Labradorite to solutions containing Al{sub (aq)}. Previous attention has been focused on the effects of organic ligands; however, the results demonstrate the important role dissolved cations play in the dissolution of aluminosilicates.« less
Eric Patterson - One of the best experts on this subject based on the ideXlab platform.
-
real time rocks shader based Labradorite
International Conference on Computer Graphics and Interactive Techniques, 2018Co-Authors: Eric Patterson, Jessica BaronAbstract:Great assignments in computer graphics rock! Being slated to complete something concrete that engages interest and provokes solid personal development while not being completely set in stone is a monumental experience. Mining ideas for learning graphics, representing something visually complex such as Labradorite can be unearthed as a gem of an assignment, and one can learn a fragment of shading while procedurally chipping away at the assignment.
-
SIGGRAPH Educator's Forum - Real-time rocks: shader-based Labradorite
ACM SIGGRAPH 2018 Educator's Forum on - SIGGRAPH '18, 2018Co-Authors: Eric Patterson, Jessica BaronAbstract:Great assignments in computer graphics rock! Being slated to complete something concrete that engages interest and provokes solid personal development while not being completely set in stone is a monumental experience. Mining ideas for learning graphics, representing something visually complex such as Labradorite can be unearthed as a gem of an assignment, and one can learn a fragment of shading while procedurally chipping away at the assignment.
