Large Pressure Effect Research Articles

Development of new improved plastic collapse moment equations of pressurized different angled pipe bends under bending moments

In a piping system, pipe bends are more flexible than straight pipes because of their curved geometry, supplemented by higher stress and strain concentration, leading to one of the crucial components in piping industries. Therefore, safe design of pipe bends is essential for smooth running of the piping system, and plastic collapse moment is one of its criteria. This paper utilizes three-dimensional finite element analyses to model empirical solutions for the plastic collapse moment for different angled pipe bends subjected to combined pressure and in-plane closing, in-plane opening, and out-of-plane bending moments. Plastic collapse moments for 30∘ to 180∘ pipe bends are determined for elastic perfectly plastic and strain hardening materials, employing large geometry change option and internal pressure effect. It is observed from results that pressure effect is more prominent in thinner pipe bends of larger bend angle under all bending cases. For in-plane opening and out-of-plane bending moments, collapse moment increases and then decreases with increase in pressure intensity for all sizes of pipe bend. However, for in-plane opening bending moment, collapse moments keep on decreasing for thicker ([Formula: see text] = 11.33) pipe bends. Finally, the study presents new improved plastic collapse moment solutions for different angled pipe bends under bending moment and internal pressure, derived from the finite element results of elastic perfectly plastic and strain hardening material models.

GW+EDMFT investigation of Pr1−xSrxNiO2 under pressure

Motivated by the recent experimental observation of a large pressure effect on ${T}_{c}$ in ${\mathrm{Pr}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{NiO}}_{2}$, we study the electronic properties of this compound as a function of pressure for $x=0$ and 0.2 doping using self-consistent $GW+\mathrm{EDMFT}$. Our numerical results demonstrate a nontrivial interplay between chemical doping and physical pressure, and small but systematic changes in the orbital occupations, local level energies, and interaction parameters with increasing pressure. The proper treatment of correlation effects, beyond density functional theory, is shown to play an important role in revealing these trends. While the pressure-dependent changes in the electronic structure of the undoped compound suggest a more single-band-like behavior in the high-pressure regime, a qualitatively different behavior is found in the doped system. We also point out that the fluctuations in the orbital occupations and spin states are not consistent with a single-band picture, and that at least a two-band model is necessary to reproduce the full result. This multiorbital nature manifests itself most clearly in the doped compound.

Strong effects of uniaxial pressure and short-range correlations in Cr2Ge2Te6

Cr$_2$Ge$_2$Te$_6$ is a quasi-2D semiconducting van der Waals ferromagnet down to the bilayer with great potential for technological applications. Engineering the critical temperature to achieve room temperature applications is one of the critical next steps on this path. Here, we report high-resolution capacitance dilatometry studies on Cr$_2$Ge$_2$Te$_6$ single crystals which directly prove significant magnetoelastic coupling and provide quantitative values of the large uniaxial pressure effects on long-range magnetic order (${\partial}T_{\mathrm{C}}/{\partial}p_{\mathrm{c}}$ = 24.7 K/GPa and ${\partial}T_{\mathrm{C}}/{\partial}p_{\mathrm{ab}}$ = $-$15.6 K/GPa) derived from thermodynamic relations. Moderate in-plane strain is thus sufficient to strongly enhance ferromagnetism in Cr$_2$Ge$_2$Te$_6$ up to room temperature. Moreover, unambiguous signs for short-range magnetic order up to 200~K are found.

Large Pressure Effects Caused by Internal Rotation in the s-cis-syn-Acrolein Stabilized Criegee Intermediate at Tropospheric Temperature and Pressure.

Criegee intermediates are important atmospheric oxidants, and quantitative kinetics for stabilized Criegee intermediates are key parameters for atmospheric modeling but are still limited. Here we report barriers and rate constants for unimolecular reactions of s-cis-syn-acrolein oxide (scsAO), in which the vinyl group makes it a prototype for Criegee intermediates produced in the ozonolysis of isoprene. We find that the MN15-L and M06-2X density functionals have CCSD(T)/CBS accuracy for the unimolecular cyclization and stereoisomerization of scsAO. We calculated high-pressure-limit rate constants by the dual-level strategy that combines (a) high-level wave function-based conventional transition-state theory (which includes coupled-cluster calculations with quasiperturbative inclusion of quadruple excitations because of the strongly multiconfigurational character of the electronic wave function) and (b) canonical variational transition-state theory with small-curvature tunneling based on a validated density functional. We calculated pressure-dependent rate constants both by system-specific quantum Rice-Ramsperger-Kassel theory and by solving the master equation. We report rate constants for unimolecular reactions of scsAO over the full range of atmospheric temperature and pressure. We found that the unimolecular reaction rates of this larger-than-previously studied Criegee intermediate depend significantly on pressure. Particularly, we found that falloff effects decrease the effective unimolecular cyclization rate constant of scsAO by about a factor of 3, but the unimolecular reaction is still the dominant atmospheric sink for scsAO at low altitudes. The large falloff caused by the inclusion of the stereoisomerization channel in the master equation calculations has broad implications for mechanistic analysis of reactions with competitive internal rotations that can produce stable rotamers.

Vocal tract adjustments to minimize vocal fold contact pressure during phonation

This computational study aims to identify vocal tract adjustments that minimize the peak vocal fold contact pressure during phonation and thus should be targeted in voice therapy treating phonotraumatic vocal hyperfunction. The results showed that for a given subglottal pressure, the effect of vocal tract adjustments on the peak vocal fold contact pressure was generally small except when such adjustments caused noticeable changes in the glottal flow amplitude. In this study, this occurred mainly when the lip opening was reduced and at conditions of large initial glottal angles or high subglottal pressures, which decreased the peak contact pressure but also significantly reduced the output sound pressure level (SPL). On the other hand, increasing lip opening significantly increased sound radiation efficiency from the mouth and reduced the subglottal pressure required to produce a target SPL. Because of the large effect of the subglottal pressure on the peak contact pressure, increasing lip opening thus was able to significantly reduce the peak contact pressure in voice tasks targeting a specific SPL. In contrast, the effect of pharyngeal expansion alone had only a small effect on the peak contact pressure, whether controlling for the subglottal pressure or targeting a specific SPL.

A diffusion-based compositionally-extended black oil model to investigate produced gas re-injection EOR in Eagle Ford

In this study, an in-house reduced black oil simulation model is used to investigate cyclic produced gas rejection in Eagle Ford shale formation. Molecular diffusion may play a crucial role in mass transfer in tight shale formations. However, the diffusion has not been incorporated in a black-oil type model in previous studies. In this study, the diffusive term is included into the governing equation and its effect on production performance is examined by using a black oil model. Diffusion coefficients are calculated by using Sigmund correlation, which makes them a function of phase compositions, phase properties, pressure, and temperature. Considering that phase compositions are influenced by large gas-oil capillary pressure nanoconfinement effect, diffusion coefficients are also altered based on this affect. This is the first study that incorporates the large gas-oil capillary pressure effect on diffusion coefficients in nanopores, through using a reduced black oil model. The operation parameters including initial injection time, injection rate, number of cycles are examined. We found that larger injection rates and more number of cycles are efficient in improving the oil recovery. Injection rate is the most crucial parameters in cyclic gas injection approach, followed by cycle numbers. Huff-n-puff results in good efficiency at relatively tight matrix, however, it is not always more efficient for very low permeabilities, as for the very tight formation, the injection gas cannot penetrate to the deeper formation to bring out much more oil from the reservoir in the same “huff” and “soaking” time period. The molecular diffusion plays an important role in gas injection process and cannot be ignored. When nano-confinement effect is included, the diffusion coefficient in gas phase is decreased and the diffusion coefficient in oil phase is increased as pore size decreases, but the effect is not strong especially at relatively high pressures.

Effects of Temperature and Pressure on the Magnetic Properties of La1–xPrxCoO3

For La1–xPrxCoO3 cobaltites (x = 0, 0.1, 0.2, and 0.3), the dependence of magnetic susceptibility is studied in the temperature range 5–400 K. Also, the crystal structure of these cobaltites is investigated, and the effect of pressure up to 2 kbar on their susceptibility is measured at , 150, and 300 K. The specific dependencies and the large negative pressure effect are assumed to arise from Co3+ ions contribution to the total susceptibility evaluated using La1−xPrxAlO3 as a reference system. The obtained experimental data on temperature and pressure effects in magnetism are analyzed within a two‐level model with energy gap Δ between the ground state of the system with zero spin of Co3+ ions and the excited higher‐spin state. In this model, magnetism of Co3+ ions is determined by the temperature‐induced population of the excited state, and magnitude of the pressure effect is governed by the volume dependence of Δ. The results of the analysis, supplemented by the theoretical calculations of the electronic structures of LaCoO3 and PrCoO3, indicate significant increase in Δ with decrease in the unit cell volume both under hydrostatic pressure and by substituting La with Pr having a smaller ionic radius.

A black-oil approach to model produced gas injection in both conventional and tight oil-rich reservoirs to enhance oil recovery

A robust compositionally extended black-oil simulation approach is developed, which is capable of including the effect of large gas-oil capillary pressure for first contact miscible (FCM), and immiscible gas injection. The simulation methodology is applied to gas flooding in both high and very low permeability reservoirs. For a high permeability conventional reservoir, simulations use a five-spot pattern with different reservoir pressures to mimic both FCM and immiscible displacements. The results show that the simple modified black-oil approach can model well both immiscible and miscible floods, as long as the minimum miscibility pressure (MMP) is matched. For a tight oil-rich reservoir, primary depletion and huff-n-puff gas injection are simulated including the effect of large gas-oil capillary pressure in flow and in flash calculation on recovery. Finally, a dynamic gas-oil relative permeability correlation that accounts for the compositional changes owing to the produced gas injection is introduced and applied to correct for changes in interfacial tension (IFT), and its effect on oil recovery is examined. The results show that the new black-oil approach can model these processes well and could be implemented when fully compositional simulations are computationally too time consuming. For the first time, a black-oil type reservoir simulation method is used to simulate near-miscible and immiscible produced gas injection enhanced oil recovery. It provides a fast and robust alternative for large-scale reservoir simulation with the purpose of flaring/venting reduction through reinjecting the produced gas into the reservoir for EOR.

Hydrogen isotope effect on the embrittlement and fatigue crack growth of steel

The deleterious effect of hydrogen on steel is a long-standing problem. Embrittlement in the presence of hydrogen is, in part, a consequence of the fast diffusion of hydrogen in ferritic steels. Because of the identical chemical properties but large differences in mass between hydrogen isotopes, interaction of hydrogen isotopes with steel structures are of interest as a tool to study the role of diffusion in hydrogen embrittlement under all-else-equal conditions. In this paper, we present tensile and fatigue data for steel samples measured in air, in hydrogen, and in deuterium. Tensile measurements show deuterium causes a loss of ductility comparable to the loss due to hydrogen. In fatigue, a large pressure effect on deuterium-assisted fatigue crack growth was observed, an effect which is not exhibited in uniaxial tensile measurements. With sufficient pressure to show an enhanced fatigue crack growth effect, the fatigue crack growth rate is well-predicted assuming a scaling of the diffusion coefficient by 1/2. These results suggest surface adsorption kinetics play a large role in hydrogen-assisted fatigue crack growth at low pressure. At higher pressures, hydrogen-assisted fatigue crack growth is primarily affected by the kinetics of diffusion of hydrogen within the steel lattice.

The internal consistency of the marine carbon dioxide system for high latitude shipboard and in situ monitoring

Deep convection in the Labrador Sea supplies large amounts of anthropogenic carbon to the ocean's interior. We use measurements of all four measurable CO2 system parameters made along AR7W (across Labrador Sea) between 2013 and 2015 to assess the internal consistency of the carbonate system, including, as appropriate, conversion to in situ temperature (T) and pressure (P). The best agreement between measured and calculated values was obtained through combination of T,P-dependent (pH or pCO2) and non-dependent (TA or DIC) parameters. Use of the dissociation constants of Mehrbach et al. (1973) as refit by Dickson and Millero (1987) and Lueker et al. (2000) yielded the best internal consistency irrespective of the input parameters used. A Monte Carlo simulation demonstrated that the propagated uncertainty (i.e. combined standard uncertainty) of calculated parameters of the carbonate system is (a) always larger than the analytical precision of the measurements themselves; (b) strongly dependent on the choice of input parameters and uncertainties; (c) less dependent on choice of the specific set of constants. For calculation of other parameters of the carbonate system from TA and DIC measurements made throughout the Labrador Sea time-series, the estimated combined standard uncertainty of calculated pCO2 and pH based on the Monte Carlo simulation is ~13 μatm and ~0.012 pH units respectively, with accuracy relative to laboratory-based measurement estimated to be between −3 and − 13 μatm and 0.002 and 0.007 pH units. Internal consistency especially at in situ temperature and pressure conditions is important for rapidly developing sensor-based monitoring programs in the region, including measurement of pH and/or pCO2 from gliders, profiling floats and moorings. We highlight uncertainty associated with the large pressure effect on pH and pCO2, and recommend a study of carbonate system internal consistency under deep ocean conditions that addresses pressure effects on calculations.

Magnetic properties of RCoO3 cobaltites (R = La, Pr, Nd, Sm, Eu). Effects of hydrostatic and chemical pressure

We have investigated the temperature dependence of the magnetic susceptibility χ(T) of rare-earth cobaltites RCoO3 (R = La, Pr, Nd, Sm, Eu) in the temperature range 4.2–300 K and also the influence of hydrostatic pressure up to 2 kbar on their susceptibility at fixed temperatures T = 78 and 300 K. The specific dependence χ(T) observed in LaCoO3 and the anomalously large pressure effect (dln χ/dP ∼−100 Mbar−1 for T = 78 K) are analyzed in the framework of a two-level model with energy levels difference Δ. The ground state of the system is assumed to be nonmagnetic with the zero spin of Co3+ ions, and magnetism at a finite temperature is determined by the excited magnetic spin state. The results of the analysis, supplemented by theoretical calculations of the electronic structure of LaCoO3, indicate a significant increase in Δ with a decrease in the unit cell volume under the hydrostatic pressure. In the series of RCoO3 (R = Pr, Nd, Sm, Eu) compounds, the volume of crystal cell decreases monotonically due to a decrease in the radius of R3+ ions. This leads to an increase in the relative energy Δ of the excited state (the chemical pressure effect), which manifests itself in a decrease in the contribution of cobalt ions to the magnetic susceptibility at a fixed temperature, and also in a decrease in the hydrostatic pressure effect on the susceptibility of RCoO3 compounds, which we have observed at T = 300 K.

Factors analysis of PM2.5 emission reduction in Chinese thermal power industry based on LMDI model

The Laspeyres index and its complete decomposition method are introduced to construct a complete decomposition model of PM2.5 emission reduction in power industry. Based on the scenario analysis, the main driving factors of the emission reduction in the thermal power industry from 2007 to 2030 were studied. The results show that energy-saving technologies such as the elimination of backward production capacity and the implementation of emission reduction technologies have the greatest contribution to the management of haze in power industry, followed by the structural adjustment effect of large pressure and small structure. With the change of thermal power from the main electricity supply to the main capacity supply, the scale reduction effect will gradually appear after 2020.

On the Theory of Solitons of Fluid Pressure and Solute Density in Geologic Porous Media, with Applications to Shale, Clay and Sandstone

We here analyze a new model of transients of pore pressure p and solute density ρ in geologic porous media. This model is rooted in the nonlinear wave theory, its focus is on advection and effect of large pressure jumps on strain. It takes into account nonlinear and also time-dependent versions of the Hooke law about stress, rate and strain. The model solutions strictly relate p and ρ evolving under the effect of a strong external stress. As a result, the presence of quick and sharp transients in low permeability rocks is unveiled, i.e., the nonlinear “Burgers solitons”. We, therefore, show that the actual transport process in porous rocks for large signals is not only the linear diffusion, but also a solitons presence could control the process. A test of a presence of solitons is applied to Pierre shale, Bearpaw shale, Boom clay and Oznam-Mugu silt and clay. An application about the presence of solitons for nuclear waste disposal and salt water intrusions is also discussed. Finally, in a kind of “theoretical experiment” we show that solitons could also be present in higher permeability rocks (Jordan and St. Peter sandstones), thus supporting the idea of a possible occurrence of osmosis also in sandstones.

High pressure structural and magnetic studies of LaFe 12 B 6

Abstract The study of the structural and magnetic properties of LaFe 12 B 6 under high pressure has been performed by combining angle-dispersive x-ray powder diffraction at room temperature up to 14 GPa and magnetization measurements up to 1 GPa. At ambient pressure, the itinerant-electron compound LaFe 12 B 6 exhibits an antiferromagnetic ground state below T N =36 K. It is demonstrated that the antiferromagnetic state can be transformed into a ferromagnetic state via a field-induced first-order metamagnetic transition accompanied with a large magnetic hysteresis. The x-ray diffraction measurements under pressure reveal that the ambient pressure crystal structure of LaFe 12 B 6 is preserved up to 14 GPa with a decrease of the unit cell parameters. A compressibility value of κ=4.90 10 −3 GPa −1 has been determined. The application of an external pressure leads also to the progressive decrease of the Neel temperature d T N /d P =−4.5 K GPa −1 . In addition a large pressure effect on the critical field μ 0 H cr of the metamagnetic transition, dμ 0 H cr / dP =24 T GPa −1 , was discovered. This clearly indicates the crucial role of volume effect on the itinerant-electron metamagnetic transition.

Effect of large gas-oil capillary pressure on production: A compositionally-extended black oil formulation

Pore sizes are typically on the order of nanometers for many shale and tight rock oil reservoirs. Such small pores can affect the phase behavior of in situ oil and gas owing to large capillary pressure. Current black-oil simulation practice is to alter the unconfined black-oil data for a fixed mean pore size to generate confined black-oil data with a suppressed bubble-point pressure. This approach ignores compositional effects on interfacial tension and the impact of pore-size distribution (PSD) with variable phase saturations on capillary pressure and phase behavior.In this paper, we develop a compositionally-extended black-oil model where we solve the compositional equations (gas, oil, and water components) directly so that black-oil data are a function of gas content in the oleic phase and gas-oil capillary pressure. The principle unknowns in the variable bubble-point fully-implicit formulation are oil pressure, overall gas composition, and water saturation. Flash calculations in the model are non-iterative and are based on K-values calculated explicitly from the black-oil data. The advantage of solving the black-oil model using the compositional equations is to increase robustness of the simulations owing to a variable bubble-point pressure that is a function of two parameters; gas content and capillary pressure. Leverett J-functions measured for the Bakken reservoir are used to establish the effective pore size-Pc-saturation relationship, where the effective pore size depends on gas saturation, which is the non-wetting phase saturation. The input fluid data to the simulator, e.g. interfacial tension (IFT), phase densities and viscosities, are pre-calculated as functions of pressure from the Peng-Robinson equation of state (PREOS) for three fixed pore sizes. During the simulation, at any pressure and saturation, fluid properties are calculated at the effective pore radius by using linear interpolation between these three data sets. We compare the results of the compositionally-extended black oil model with those of a fully-implicit eight-component compositional model that we have also developed. The results for the Bakken reservoir show that including PSD in the model can increase estimated recoveries by nearly 10% for initially undersaturated reservoirs while the increase can be over 100% for initially saturated reservoirs. Capillary pressure significantly increases the original oil-in-place (OOIP) for reservoirs that would otherwise be initially saturated leading to larger oil production.

Finite element analysis of deformation characteristics in cold helical rolling of bearing steel-balls

Due to the complexity of investigating deformation mechanisms in helical rolling (HR) process with traditional analytical method, it is significant to develop a 3D finite element (FE) model of HR process. The key forming conditions of cold HR of bearing steel-balls were detailedly described. Then, by taking steel-ball rolling elements of the B7008C angular contact ball bearing as an example, a completed 3D elastic-plastic FE model of cold HR forming process was established under SIMUFACT software environment. Furthermore, the deformation characteristics in HR process were discovered, including the forming process, evolution and distribution laws of strain, stress and damage based on Lemaitre relative damage model. The results reveal that the central loosening and cavity defects in HR process may have a combined effect of large negative hydrostatic pressure (positive mean stress) caused by multi-dimensional tensile stresses, high level transverse tensile stress, and circular-alternating shear stress in cross section.

Collapse of ferromagnetism in itinerant-electron system: A magnetic, transport properties, and high pressure study of (Hf,Ta)Fe2 compounds

The magnetism and transport properties were studied for Laves (Hf,Ta)Fe2 itinerant-electron compounds, which exhibit a temperature-induced first-order transition from the ferromagnetic (FM) to the antiferromagnetic (AFM) state upon heating. At finite temperatures, the field-induced metamagnetic phase transition between the AFM and FM has considerable effects on the transport properties of these model metamagnetic compounds. A large negative magnetoresistance of about 14% is observed in accordance with the metamagnetic transition. The magnetic phase diagram is determined for the Laves Hf1−xTaxFe2 series and its Ta concentration dependence discussed. An unusual behavior is revealed in the paramagnetic state of intermediate compositions, it gives rise to the rapid increase and saturation of the local spin fluctuations of the 3d electrons. This new result is analysed in the frame of the theory of Moriya. For a chosen composition Hf0.825Ta0.175Fe2, exhibiting such remarkable features, a detailed investigation is carried out under hydrostatic pressure up to 1 GPa in order to investigate the volume effect on the magnetic properties. With increasing pressure, the magnetic transition temperature TFM-AFM from ferromagnetic to antiferromagnetic order decreases strongly non-linearly and disappears at a critical pressure of 0.75 GPa. In the pressure-induced AFM state, the field-induced first-order AFM-FM transition appears and the complex temperature dependence of the AFM-FM transition field is explained by the contribution from both the magnetic and elastic energies caused by the significant temperature variation of the amplitude of the local Fe magnetic moment. The application of an external pressure leads also to the progressive decrease of the Néel temperature TN. In addition, a large pressure effect on the spontaneous magnetization MS for pressures below 0.45 GPa, dln(Ms)/dP = −6.3 × 10−2 GPa−1 was discovered. The presented results are consistent with Moriya's theoretical predictions and can significantly help to better understand the underlying physics of itinerant electron magnetic systems nowadays widely investigated for both fundamental and applications purposes.

Study on theory model of hydro-thermal–mechanical interaction process in saturated freezing silty soil

Abstract The freezing of frost susceptible soils is a dynamic hydro-thermal–mechanical (THM) interacting process. One-side freezing experiments of saturated soil in an open system with no-pressure water supplement are carried out. In these experiments, we analyzed the influence of temperature gradients, overburden pressures and cooling temperatures on moisture migration and frost heave. Based on these experiments, a mathematical model of frost heave is proposed with the variables of temperature, porosity and displacement, in which Clapeyron equation is employed as the phase equilibrium condition of water and ice in soil. Ice lens is one of the major aspects of the frost heave for frost susceptible soils. According to the mechanical and physical characteristics, a comprehensive criterion for the formation and end of new ice lens is presented. To solve the nonlinear equations, the finite element algorithm is applied to solve the general form of governing equations. Finally, numerical simulations are implemented with the assistance of COMSOL. Validation of the model is illustrated by comparisons between the simulation and experimental results. From this study, it is found that, (1) cooling temperature is the necessary condition for moisture migration and frost heave since pore water phases into ice under cooling temperature. Then negative pore water pressure occurs in soil. Pore water pressure gradient is the direct driving force for water migration in saturated soil. However, temperature gradient and overburden pressure have important influence on the pore water pressure gradient. The response of soil sample to the variation of water content lags behind the response to the change of temperature. (2) Discontinuously distributed ice lenses form near the cold front when the accumulated water phases to ice. Temperature gradient, overburden pressure and cooling temperature are key factors to determine the frost heave and moisture migration. (3) Freezing and migration of unfrozen water cause the change of porosity in soil. Ice lens will block the migration of unfrozen water. The discrete ice lenses result in the oscillation in the distributions of water content. (4) Unsaturated phenomenon occurs in the unfrozen zone under the frozen fringe which might be related to the suction effect of large negative pressure in this zone.

Opening the Black Box of CSR Decision Making: A Policy-Capturing Study of Charitable Donation Decisions in China

This policy-capturing study, conducted in China, investigated the cognitive basis of managerial decisions to make a corporate charitable donation, a global issue in the context of corporate social responsibility (CSR) research and practice. Participants (N = 376) responded to a series of scenarios manipulating pressure from the five stakeholders (government, customers, competitors, employees, and shareholders) most commonly addressed by CSR research. The independent variables examined included organizational factors (industry, ownership, previous company donation, firm size, firm age, and perceived CEO attitudes toward charity) and the participants’ personal values. Results indicate a large positive effect of shareholder and governmental pressure on the decision with lesser positive effects from customers and competitors. Surprisingly, employee pressure had a negative effect on the decision to make a charitable donation. Further, personal values and perceived CEO attitudes toward charity were significantly related to the decisions participants made. In line with our theorizing, the findings indicate that a combination of personal, organizational, and institutional factors was salient in the minds of decision makers.

Partitioning of platinum-group elements and Au between sulfide liquid and basalt and the origins of mantle-crust fractionation of the chalcophile elements

The partitioning of platinum-group elements (PGE; Os, Ir, Ru, Rh, Pt, and Pd) and Au between sulfide melt and silicate melt (i.e., DPGEsul) exerts a critical control on the PGE composition of the Earth’s crust and mantle, but previous estimates have been plagued by experimental uncertainties and vary through several orders of magnitude. Here we present direct experimental measurements of DPGEsul, based on in situ microanalysis of the sulfide and silicate melt, with values ranging from ∼4×105 (Ru) to ∼2–3×106 (Ir, Pt). Our measurements of DPGEsul are >100 times larger than previous results but smaller than anticipated based on comparison of alloy solubilities in sulfide melts and S-free silicate melts. The presence of S in the silicate melt greatly increases alloy solubility. We use our new set of partition coefficients to develop a fully constrained model of PGE behavior during melting which accurately predicts the abundances of PGE in mantle-derived magmas and their restites, including mid-ocean ridge basalts, continental picrites, and the parental magmas of the Bushveld Complex of South Africa. Our model constrains mid-ocean ridge basalt (MORB) to be the products of pooled low and high degree fractional melts. Within-plate picrites are pooled products of larger degrees of fractional melting in columnar melting regimes. A significant control on PGE fractionation in mantle-derived magmas is exerted by residual alloy or platinum group minerals in their source. At low pressures (e.g., MORB genesis) the mantle residual to partial melting retains primitive mantle inter-element ratios and abundances of PGE until sulfide has been completely dissolved but then evolves to extremely high Pt/Pd and low Pd/Ir because Pt and Ir alloys form in the restite. During melting at high pressure to form picrites or komatiites Ir alloy appears as a restite phase but Pt alloy is not stable due to the large effect of pressure on fS2, and of temperature on fO2 along an internal oxygen buffer, which causes large increases in alloy solubility. The magmas parental to the Bushveld Complex of South Africa appear, at least in part, to be partial melts of mantle that has previously been melted to the point of total sulfide exhaustion at low pressure, closely resembling mantle xenoliths of the Kaapvaal craton. Using the new extremely large DPGEsul the world-class Merensky Reef and UG2 Pt deposits of the Bushveld Complex can readily be modeled as the result of sulfide saturation due to mixing of magmas with unremarkable PGE contents, obviating the need to postulate anomalously PGE-rich parent magmas or hydrothermal inputs to the deposits.