Proteins in Wonderland: The Magical World of Pressure

Admitting the “Native”, “Unfolded” and “Fibril” states as the three basic generic states of proteins in nature, each of which is characterized with its partial molar volume, here we predict that the interconversion among these generic states N, U, F may be performed simply by making a temporal excursion into the so called “the high-pressure regime”, created artificially by putting the system under sufficiently high hydrostatic pressure, where we convert N to U and F to U, and then back to “the low-pressure regime” (the “Anfinsen regime”), where we convert U back to N (U→N). Provided that the solution conditions (temperature, pH, etc.) remain largely the same, the idea provides a general method for choosing N, U, or F of a protein, to a great extent at will, assisted by the proper use of the external perturbation pressure. A successful experiment is demonstrated for the case of hen lysozyme, for which the amyloid fibril state F prepared at 1 bar is turned almost fully back into its original native state N at 1 bar by going through the “the high-pressure regime”. The outstanding simplicity and effectiveness of pressure in controlling the conformational state of a protein are expected to have a wide variety of applications both in basic and applied bioscience in the future.

Pressure-induced superconductivity and structure phase transition in Pt2HgSe3

Recently monolayer jacutingaite (Pt2HgSe3), a naturally occurring exfoliable mineral, discovered in Brazil in 2008, has been theoretically predicted as a candidate quantum spin Hall system with a 0.5 eV band gap, while the bulk form is one of only a few known dual-topological insulators that may host different surface states protected by symmetries. In this work, we systematically investigate both structure and electronic evolution of bulk Pt2HgSe3 under high pressure up to 96 GPa. The nontrivial topology is theoretically stable, and persists up to the structural phase transition observed in the high-pressure regime. Interestingly, we found that this phase transition is accompanied by the appearance of superconductivity at around 55 GPa and the critical transition temperature Tc increases with applied pressure. Our results demonstrate that Pt2HgSe3 with nontrivial topology of electronic states displays a ground state upon compression and raises potentials in application to the next-generation spintronic devices.

Pressure-Assisted Development and Characterization of Al-Fe Interface for Bimetallic Composite Castings: An Experimental and Statistical Investigation for a Low-Pressure Regime

A review of the available literature indicates that the development of metal-reinforced castings present intriguing prospects but carry inherent challenges owing to differences in thermal coefficients, chemical affinities, diffusion issues and the varying nature of intermetallic compounds. It is supported that pressure application during solidification may favorably influence the dynamics of the aforementioned issues; nevertheless, not only certain limitations have been cited, but also some pressure and process regimes have not yet been investigated and optimized. This work employs the pressure-assisted approach for bimetallic steel-reinforced aluminum composite castings at a low-pressure regime and thoroughly investigates the role of three process parameters, namely pouring temperature (800–900 °C), pressure (10–20 bars) and holding time (10–20 s), for producing sound interfaces. The Taguchi L9 orthogonal array has been employed as the Design of the Experiment, while dominant factors have been determined via analysis of variance and the grey relational analysis multi-objective optimization technique. Supplementary analysis through optical micrographs, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) has been utilized to quantify interfacial layer thicknesses and to study microstructural and compositional aspects of the interface. Nano-indentation tests under static and dynamic loading have also been performed for mechanical strength characterization. It has been found that uniform interfaces with verifiable diffusion are obtainable, with the pouring temperature being the most influential parameter (percentage contribution 92.84%) in this pressure regime. The experiments performed at optimum conditions of pouring temperature, applied pressure and holding time produced a ~328% thicker interface layer, 19.42% better nano-hardness and a 19.10% improved cooling rate as compared to the minimum input values of the said parameters.

Evolution of seafloor pockmarks along the Northern Orange Basin, Offshore South Africa: Interplay between fluid flow and bottom current activities

Pockmarks are pervasive geomorphologic features identified along continental margins resulting from fluid expulsion on the seafloor. However, the understanding of the underlying geological mechanism/control in relation to their evolution, distribution, and morphology is limited, especially along data-starved continental margins such as the Northern Orange Basin. Analysis of a high-quality 3D seismic reflection data reveals at least 50 individual pockmarks, two channel-like depressions and several irregular depressions in water depth ranging between 800 m and 2400 m. Morphologically, the pockmarks are circular, elongated, comet-like and crescentic in shape, with diameters and depths ranging between ∼0.2 - 2.8 km and ∼10 - 130 m, respectively. Preferential alignment of these pockmarks on the seafloor in relation to the axis of underlying turbidite channels, erosional morphologies and mass transport complexes portray a genetic relationship. The slope architecture hints at the possibility of both deep and shallow fluid source driving pockmark formation. Under this scenario, deep thermogenic gas derived from Cretaceous source rocks migrated along fault systems associated with the Late Cretaceous Megaslide complex to the overburden. The fluids are stored/redistributed in contourite and turbidite channels and subsequently focused toward the seafloor under an increased pore pressure regime. Yet, the fluids may be either solely biogenic gas or heterogeneous, incorporating biogenic components and pore-water derived from the channels and dewatering of the contourites. Importantly, the discovery of crescentic and elongated end-member pockmark morphologies indicate post-formation sculpting of the initial pockmark morphologies by bottom currents. The discovery of these deep-water pockmarks opens the possibility that such fluid escape features may be more widespread than currently documented in the Northern Orange Basin. This has implications in understanding of the petroleum system here and their potential role in the South Atlantic marine ecosystems and global climate change in terms of the expulsion of climate forcing gases.

Bringing the Best of Sampling While Drilling in Highly Deviated S-Profile Wells: Case Studies from a Brown Field, Sabah, Offshore Malaysia

Sampling While Drilling has undergone significant changes since its advent early this decade. The continuum of applications has primarily been due to the ability to access highly deviated wellbores, to collect PVT quality and volume of formation fluids. The increased confidence is also a result of numerous applications with varied time-on-wall without ever being stuck. This paper demonstrates the contribution of this technology for reservoir fluid mapping that proved critical to update the resource assessment in a brown field through three infill wells that were a step-out to drill unpenetrated blocks and confirm their isolation from the main block of the field. As a part of the delineation plan, the objective was to confirm the current pressure regime and reservoir fluid type when drilling the S-profile appraisal wells with 75 degrees inclination. Certain sand layers were prone to sanding as evidenced from the field's long production history. Due to the proven record of this technology in such challenges, locally and globally, pipe-conveyed wireline was ruled out. During pre-job planning, there were concerns about sanding, plugging and time-on-wall and stuck tools. Empirical modeling was performed to provide realistic estimates to secure representative fluid samples. The large surface area pad was selected, due to its suitability in highly permeable yet unconsolidated formations. For the first well operation, the cleanup for confirming formation oil began with a cautious approach considering possible sanding. An insurance sample was collected after three hours. For the next target, drawing on the results of the first sampling, the pump rate was increased early in time, and a sample was collected in half the time. Similar steps were followed for the remaining two wells, where water samples were collected. Oil, water, and gas gradients were calculated. Lessons learnt and inputs from Geomechanics were used in aligning the probe face and reference to the critical drawdown pressure (CDP). A total of 4,821 feet (1,469 meters) was drilled. 58 pressures were acquired, with six formation fluid samples and five cleanup cycles for fluid identification purpose. The pad seal efficiency was 95%. The data provided useful insights into the current pressure regime and fault connectivity, enabling timely decisions for well completion. The sampling while drilling deployment was successful in the highly deviated S-profile wells and unconsolidated sand, with no nonproductive time. Because of the continuous circulation, no event of pipe sticking occurred, thereby increasing the confidence, especially in the drilling teams. The sampling while drilling operations were subsequent, due to batch drilling, with minimal time in between the jobs for turning the tools around. The technology used the latest generation sensors, algorithms, computations and was a first in Malaysia. The campaign re-instituted the clear value of information in the given environment and saving cost.

Large-Scale Molecular Dynamics Simulations Reveal New Insights Into the Phase Transition Mechanisms in MIL-53(Al)

Soft porous crystals have the ability to undergo large structural transformations upon exposure to external stimuli while maintaining their long-range structural order, and the size of the crystal plays an important role in this flexible behavior. Computational modeling has the potential to unravel mechanistic details of these phase transitions, provided that the models are representative for experimental crystal sizes and allow for spatially disordered phenomena to occur. Here, we take a major step forward and enable simulations of metal-organic frameworks containing more than a million atoms. This is achieved by exploiting the massive parallelism of state-of-the-art GPUs using the OpenMM software package, for which we developed a new pressure control algorithm that allows for fully anisotropic unit cell fluctuations. As a proof of concept, we study the transition mechanism in MIL-53(Al) under various external pressures. In the lower pressure regime, a layer-by-layer mechanism is observed, while at higher pressures, the transition is initiated at discrete nucleation points and temporarily induces various domains in both the open and closed pore phases. The presented workflow opens the possibility to deduce transition mechanism diagrams for soft porous crystals in terms of the crystal size and the strength of the external stimulus.

40Ar/39Ar age evidence for an impact-generated hydrothermal system in the Devonian Siljan crater, Sweden

ABSTRACT Crater-forming events are generally followed by the development of hydrothermal systems due to the rapid heating of the target rock. Such hydrothermal systems are a feature of nearly all large terrestrial impact structures. For the Siljan impact structure in Sweden, there is evidence for such a fossil hydrothermal system, possibly triggered by the impact event ca. 380 Ma. To investigate the thermal regime of the near-surface hydrothermal activity of the Siljan crater, biotite and amphibole grains extracted from samples collected in a transect across the high-pressure regime recorded by the central uplift, as well as from distal localities outside the central uplift of the crater, were dated using the 40Ar/39Ar laser step-heating technique. Our results show that biotite from inside the central uplift, which was strongly altered to chlorite by low-temperature (200–340 °C) hydrothermal reactions, yields strongly disturbed age spectra. The first and second (low laser power) step ages range from ca. 1300 to 190 Ma. In contrast, biotite from outside the central uplift and amphibole, irrespective of location inside or outside of the central uplift, are much less altered, which is reflected in less disturbed, near-flat age spectra. This result indicates that the hydrothermal temperatures inside the central uplift were >200 °C, sufficient to disturb the K-Ar system of biotite during its chloritization, but too low to affect the amphibole (closure temperature of 480–580 °C). In contrast, the temperature of the hydrothermal system outside of the central uplift was <200 °C, as no significant reset of the K-Ar system can be observed in either biotite or amphibole. Our results are consistent with estimated trapping temperatures from fluid inclusion studies, which show a decrease from 327–342 °C within the central uplift to 40–225 °C toward outside the central uplift. We conclude that the near-surface hydrothermal system in the Siljan impact structure was an impact-triggered system. This system was strongly active, with its highest temperature inside the central uplift and decreasing rapidly toward the outlying part of the crater.

Behavior and properties of water in silicate melts under deep mantle conditions

Water (H2O) as one of the most abundant fluids present in Earth plays crucial role in the generation and transport of magmas in the interior. Though hydrous silicate melts have been studied extensively, the experimental data are confined to relatively low pressures and the computational results are still rare. Moreover, these studies imply large differences in the way water influences the physical properties of silicate magmas, such as density and electrical conductivity. Here, we investigate the equation of state, speciation, and transport properties of water dissolved in Mg1−xFexSiO3 and Mg2(1−x)Fe2xSiO4 melts (for x = 0 and 0.25) as well as in its bulk (pure) fluid state over the entire mantle pressure regime at 2000–4000 K using first-principles molecular dynamics. The simulation results allow us to constrain the partial molar volume of the water component in melts along with the molar volume of pure water. The predicted volume of silicate melt + water solution is negative at low pressures and becomes almost zero above 15 GPa. Consequently, the hydrous component tends to lower the melt density to similar extent over much of the mantle pressure regime irrespective of composition. Our results also show that hydrogen diffuses fast in silicate melts and enhances the melt electrical conductivity in a way that differs from electrical conduction in the bulk water. The speciation of the water component varies considerably from the bulk water structure as well. Water is dissolved in melts mostly as hydroxyls at low pressure and as –O–H–O–, –O–H–O–H– and other extended species with increasing pressure. On the other hand, the pure water behaves as a molecular fluid below 15 GPa, gradually becoming a dissociated fluid with further compression. On the basis of modeled density and conductivity results, we suggest that partial melts containing a few percent of water may be gravitationally trapped both above and below the upper mantle-transition region. Moreover, such hydrous melts can give rise to detectable electrical conductance by means of electromagnetic sounding observations.

Pressure Assisted Development and Characterization of Al-Fe Interface for bi-metallic Composite Castings: An Experimental and Statistical Investigation for Low Pressure Regime

Review of the available literature indicates that development of metal reinforced castings present intriguing prospects but carry inherent challenges owing to differences in thermal coefficients, chemical affinities, diffusion issues and varying nature of intermetallic compounds. It is supported that pressure application during solidification may favorably influence the dynamics of the aforementioned issues, nevertheless, not only certain limitations have been cited but also some pressure and process regimes have not been found to be investigated and optimized. This work employs the pressure-assisted approach for bi-metallic steel reinforced aluminum composite castings at low-pressure regime and thoroughly investigates the role of three process parameters namely pouring temperature (800°C-900°C), pressure (10–20 bars) and holding time (10–20 sec) for producing sound interfaces. Taguchi L9 orthogonal array has been employed as DOE while dominant factors have been determined via ANOVA and Grey relational analysis multi-objective optimization technique. Supplementary analysis through optical micrographs, SEM and EDS has been relied upon to quantify interfacial layer thicknesses and to study microstructural and compositional aspects of the interface. Nano-indentation tests under static and dynamic loading have also been performed for mechanical strength characterization. It has been found that uniform interfaces with verifiable diffusion are obtainable with pouring temperature being the most influential parameter (PCR 92.84%) in this pressure regime. Optimum parameters determined from the work, yield ~ 328% thicker interface layer, 19.42% better nano-hardness and 19.10% improved cooling rate when compared to the process conditions with least parametric levels.