CaS: A key medium for C-O-S-Ca cycles in Earth

Oldhamite (CaS) is a rare mineral, which is only observed naturally in enstatite meteorites.No occurrence of CaS has been documented from other groups of meteorites and terrestrial samples. However, in experiments at 1.5 GPa/1510 K and 0.5 GPa/1320 K, when the lgfo2 is lower than -10.57 (FMQ-0.52), CaS was produced in this study by a two-melt mechanism involving the reaction between molten pyrrhotite-pentlandite-bearing orthopyroxenite and molten CaCO3. CaS can be easily oxidized to form CaSO4 or hydrolyzed to produce calcium hydroxide, which may explain why it has never been found in geological samples from Earth. We speculate that part of the anhydrite and gypsum in black smokers along mid-ocean ridges are related to the oxidation or hydrolysis of CaS in the underlying mantle. CaS can be produced when the Siberian mantle plume intruded into the lithosphere.Comment: The third versio

Benchmarking computational fluid dynamics models of lava flow simulation for hazard assessment, forecasting, and risk management

Abstract Numerical simulations of lava flow emplacement are valuable for assessing lava flow hazards, forecasting active flows, designing flow mitigation measures, interpreting past eruptions, and understanding the controls on lava flow behavior. Existing lava flow models vary in simplifying assumptions, physics, dimensionality, and the degree to which they have been validated against analytical solutions, experiments, and natural observations. In order to assess existing models and guide the development of new codes, we conduct a benchmarking study of computational fluid dynamics (CFD) models for lava flow emplacement, including VolcFlow, OpenFOAM, FLOW-3D, COMSOL, and MOLASSES. We model viscous, cooling, and solidifying flows over horizontal planes, sloping surfaces, and into topographic obstacles. We compare model results to physical observations made during well-controlled analogue and molten basalt experiments, and to analytical theory when available. Overall, the models accurately simulate viscous flow with some variability in flow thickness where flows intersect obstacles. OpenFOAM, COMSOL, and FLOW-3D can each reproduce experimental measurements of cooling viscous flows, and OpenFOAM and FLOW-3D simulations with temperature-dependent rheology match results from molten basalt experiments. We assess the goodness-of-fit of the simulation results and the computational cost. Our results guide the selection of numerical simulation codes for different applications, including inferring emplacement conditions of past lava flows, modeling the temporal evolution of ongoing flows during eruption, and probabilistic assessment of lava flow hazard prior to eruption. Finally, we outline potential experiments and desired key observational data from future flows that would extend existing benchmarking data sets

Evolution of Fault Strength from Microscopic Asperity Scale to Macroscopic Fault Zone Scale

Fault strength is of key importance to geological and geophysical processes over a vast range of scales, from the microscopic interactions at asperities to the macroscopic behavior of plates. In this dissertation, I present my work on the evolution of fault strength. I first use a micromechanical model of flash heating that describes how shear resistance evolves at the asperity scale as a result of distributed deformation over a weak layer that grows during the brief lifetime of each asperity contact. The model predicts that after the initial rate-weakening stage, the friction becomes rate-strengthening. A comparison with published experimental data from a range of mineral systems shows good agreement with the model predictions. The parameter choices that ensure good model fits to the laboratory friction data are consistent with a priori estimates for the onset of asperity melting at high contact normal stresses. Next, considering the role of friction in fluid-saturated gouge, a linear stability analysis shows that rate-strengthening friction favors broader shear zone widths that lower strain rate for a given total slip rate. However, geologic and laboratory observations suggest that finite shear zones can persist even with rate-weakening friction. I describe a model that incorporates the interactions between variations in pore pressure of saturated porous media and the localization-pressurization phenomenon. During co-seismic slip in a plane-strain configuration, the stress variation caused by poroelasticity promotes the mechanical instability of previously undeformed regions. The frictional strength varies throughout the mechanically unstable region. To maintain momentum balance during slip, I argue that multiple transient slip events must take place to accommodate the overall macroscopic shear. I introduce a strain-rate function that describes the overall influence on energy dissipation and fault strength as the model shear zone thickness expands. The model is used to predict the evolution of shear zone thickness, temperature, pore pressure, and fault strength during model earthquakes along a mature fault. These two components of my dissertation build from the very small scale of asperities, to granules, and finally to the finite shear zones that are observed in the fields. This dissertation includes previously published and unpublished co-authored material.2015-10-1

A Monte Carlo Approach to Approximating the Effects of Pore Geometry on the Phase Behavior of Soil Freezing

Abstract Freezing in porous media is associated with a host of dynamic phenomena that stem from the presence and mobility of premelted liquid at subzero temperatures. Accurate assessments of the progressive liquid‐ice phase transition is required for predictive models of frost damage, glacier‐till coupling, and many other cold regions processes, as well as for evaluating the capacity for water storage in near‐surface extraterrestrial environments. We use a Monte Carlo approach to sample the pore space in a synthetic 3D packing of poly‐dispersed spherical particles and evaluate local geometrical constraints that allow us to assess changes in the relative proportions of pore fluid and ice. By approximating the phase boundary geometry in fine‐grained pores while considering both the curvature of the liquid‐ice interface and wetting interactions with matrix particles, our model predicts changes in phase equilibrium in granular media over a broad temperature range, where present accounting for the colligative effects of chloride and perchlorate solutes. In addition to formulating the constitutive behavior needed to better understand properties and processes in frozen soils, our results also provide insight into other aspects of phase equilibria in porous media, including the formation of methane hydrates in permafrost and marine sediments, and the partitioning between liquid water and vapor in the vadose zone

Experimental study on the competition between carbon dioxide hydrate and ice below the freezing point

As climate change and industrial requirements intensify, the potential of CO2 hydrates for carbon storage has attracted increasing attention. However, despite continuous progress, the subzero phase behavior of the CO2-H2O system is not well understood and merits further research. To investigate the competing and coexisting growth mechanisms of CO2 gas hydrate and ice below the quadruple point, we conducted experiments at both the micrometer-scale and mesoscale scales. The growth morphology of hydrate and ice at large and small subcooling temperatures was observed in situ in a high-pressure optical cell, and the thermodynamic behavior of the competitive process after hydrate formation was investigated in a high-pressure reactor with sands. When hydrates and ice are formed together at small subcooling temperatures, preferential hydrate formation leads to ice dissolution or even disappearance. At large subcooling temperatures, ice forms first, and the hydrate mainly forms a fibrous envelope. A small decrease in the subzero temperature after hydrate formation partially decomposes the hydrates owing to ice formation, followed by more rapid hydrate production. This study provides a thorough and expanded understanding of the competition between ice and hydrates by connecting the evolution of crystal frameworks with the thermodynamic features of the process. (c) 2022 Elsevier Ltd. All rights reserved

RER1 enhances carcinogenesis and stemness of pancreatic cancer under hypoxic environment

Abstract Background Increasing incidence and mortality rates of pancreatic cancer (PC) highlight an urgent need for novel and efficient drugs. Retention in endoplasmic reticulum 1 (RER1) is an important retention factor in the endoplasmic reticulum (ER). However, it remains elusive whether RER1 is involved in the retention of disease-related proteins. Methods We analyzed the expression level of RER1 in PC and adjacent tissues, and also employed Kaplan–Meier’s analysis to identify the correlation between RER1 expression and overall survival rate. Cell proliferation, colony formation, tumor formation, scratch test, and transwell invasion assays were performed in RER1 knockdown cells and negative control cells. Results We hereby reported the important functions of RER1 in tumorigenesis and metastasis of PC, evidenced by inhibitory effects of RER1 knockdown on PC cell proliferation, migration and aggressiveness. Tumor formation was also significantly repressed in RER1 knockdown cells compared to control. Hypoxia-inducible factor (HIF)-1α was found to be an upstream regulator of RER1. Knockdown HIF-1α cells exhibited similar repressive impact on cell proliferation as RER1, and showed diminished migratory and invasive abilities under hypoxic condition. Conclusion The present study has demonstrated that RER1 enhances the progression of PC through promoting cell proliferation, migration and aggressiveness

In Situ Raman Spectroscopy and DFT Studies of the Phase Transition from Zircon to Reidite at High P–T Conditions

Zircon (ZrSiO4) provides a good pressure-holding environment for ultra-high-pressure metamorphic minerals during crust exhumation due to its high incompressibility and chemical stability. At high pressure, the zircon can transform to reidite. Previous studies show much higher phase-transition pressures at room temperature than those at high temperature (>1000 K) due to kinetic hindrance. To further investigate the kinetics of the zircon–reidite phase transition at relatively low temperatures, the phase boundary at 298–800 K was determined using a diamond anvil cell combined with in situ Raman spectra. The results show that reidite becomes thermodynamically more stable compared with zircon at 8 GPa at room temperature, and the slope of the phase boundary at 298–800 K abruptly differs from that of previous studies at 1100–1900 K. Compared with the equilibrium phase boundary calculated by the density functional theory, it indicates that the kinetic effect of the zircon–reidite phase transition is obvious, and there exists a sufficiently large energy driving force provided by an overpressure to overcome the activation energy barrier below a critical temperature of approximately 880 K. The temperature dependence of overpressure is about 0.023 GPa/K

Targeting the MCP‐GPX4/HMGB1 Axis for Effectively Triggering Immunogenic Ferroptosis in Pancreatic Ductal Adenocarcinoma

Abstract Induction of ferroptosis can inhibit cancer cells in vitro, however, the role of ferroptosis in treatment in vivo is controversial. The immunosuppressive cells activated by the ferroptotic tumor cells can promote the growth of residual tumor cells, hindering the application of ferroptosis stimulation in tumor treatment. In this study, a new strategy is aimed to be identified for effectively triggering immunogenic ferroptosis in pancreatic ductal adenocarcinoma (PDAC) and simultaneously stimulating antitumor immune responses. Toward this, several molecular and biochemical experiments are performed using patient‐derived organoid models and a KPC mouse model (LSL‐KrasG12D/+, LSL‐Trp53R172H/+, Pdx‐1‐Cre). It is observed that the inhibition of macrophage‐capping protein (MCP) suppressed the ubiquitin fold modifier (UFM)ylation of pirin (PIR), a newly identified substrate of UFM1, thereby decreasing the transcription of GPX4, a marker of ferroptosis, and promoting the cytoplasmic transportation of HMGB1, a damage‐associated molecular pattern. GPX4 deficiency triggered ferroptosis, and the pre‐accumulated cytosolic HMGB1 is released rapidly. This altered release pattern of HMGB1 facilitated the pro‐inflammatory M1‐like polarization of macrophages. Thus, therapeutic inhibition of MCP yielded dual antitumor effects by stimulating ferroptosis and activating antitumor pro‐inflammatory M1‐like macrophages. The nanosystem developed for specifically silencing MCP is a promising tool for treating PDAC