High-Pressure Structures and Superconductivity of Barium Iodide

Generally, pressure is a useful tool to modify the behavior of physical properties of materials due to the change in distance between atoms or molecules in the lattice. Barium iodide (BaI2), as one of the simplest and most prototypical iodine compounds, has substantial high pressure investigation value. In this work, we explored the crystal structures of BaI2 at a wide pressure range of 0–200 GPa using a global structure search methodology. A thermodynamical structure with tetragonal I4/mmm symmetry of BaI2 was predicted to be stable at 17.1 GPa. Further electronic calculations indicated that I4/mmm BaI2 exhibits the metallic feature via an indirect band gap closure under moderate pressure. We also found that the superconductivity of BaI2 at 30 GPa is much lower than that of CsI at 180 GPa based on our electron–phonon coupling simulations. Our current simulations provide a step toward the further understanding of the high-pressure behavior of iodine compounds at extreme conditions.

Formation, preservation and extinction of high-pressure minerals in meteorites: temperature effects in shock metamorphism and shock classification

The goal of classifying shock metamorphic features in meteorites is to estimate the corresponding shock pressure conditions. However, the temperature variability of shock metamorphism is equally important and can result in a diverse and heterogeneous set of shock features in samples with a common overall shock pressure. In particular, high-pressure (HP) minerals, which were previously used as a solid indicator of high shock pressure in meteorites, require complex pressure–temperature–time (P–T–t) histories to form and survive. First, parts of the sample must be heated to melting temperatures, at high pressure, to enable rapid formation of HP minerals before pressure release. Second, the HP minerals must be rapidly cooled to below a critical temperature, before the pressure returns to ambient conditions, to avoid retrograde transformation to their low-pressure polymorphs. These two constraints require the sample to contain large temperature heterogeneities, e.g. melt veins in a cooler groundmass, during shock. In this study, we calculated shock temperatures and possible P–T paths of chondritic and differentiated mafic–ultramafic rocks for various shock pressures. These P–T conditions and paths, combined with observations from shocked meteorites, are used to constrain shock conditions and P–T–t histories of HP-mineral bearing samples. The need for rapid thermal quench of HP phases requires a relatively low bulk-shock temperature and therefore moderate shock pressures below ~ 30 GPa, which matches the stabilities of these HP minerals. The low-temperature moderate-pressure host rock generally shows moderate shock-deformation features consistent with S4 and, less commonly, S5 shock stages. Shock pressures in excess of 50 GPa in meteorites result in melt breccias with high overall post-shock temperatures that anneal out HP-mineral signatures. The presence of ringwoodite, which is commonly considered an indicator of the S6 shock stage, is inconsistent with pressures in excess of 30 GPa and does not represent shock conditions different from S4 shock conditions. Indeed, ringwoodite and coexisting HP minerals should be considered as robust evidence for moderate shock pressures (S4) rather than extreme shock (S6) near whole-rock melting.

Role of Central Atom on the Pressure Response of 2D Perovskites Containing a Long Alkyl Chain (Decylammonium, DA): DA2PbI4 and DA2GeI4

The application of an external pressure on Metal Halide Perovskite (MHPs) has become a fascinating way of tuning their optical properties, achieving also novel features. Here, the pressure response of 2D MHPs including a long alkyl chain made of ten carbon atoms, namely decylammonium (DA), has been investigated as a function of the central atom in DA2PbI4 and DA2GeI4. The two systems share a common trend in the phase stability, displaying a transition from an orthorhombic to a monoclinic phase around 2 GPa, followed by a phase separation in two monoclinic phases characterized by different c-axis. The optical properties show rather different behavior due to the presence of Pb or Ge. DA2PbI4 shows a progressive red shift of the band gap from 2.28 eV at ambient conditions, to 1.64 eV at 11.5 GPa, with a narrow PL emission composed by two components, with the second one appearing in concomitance with the phase separation and significantly shifted to lower energy. On the other hand, DA2GeI4, changes from a non-PL system at ambient pressure, to a clear broadband emitter centered around 730 nm (FWHM ~ 170 nm), with a large stoke shift, and an intensity maximum at about 3.7 GPa. This work sheds light on the structural stability of 2D perovskites characterized by extended alkyl chains, to date limited to four carbon atoms, and shows the pressure-induced emergence of broad emission in a novel lead-free perovskite, DA2GeI4. The evidence of wide emission by a moderate pressure in a germanium-based 2D MHP represents a novel result which may open the design, by chemical pressure, of efficient wide or even white lead-free emitters.

INVESTIGATION OF AIR INJECTION TO ENHANCED OIL RECOVERY FROM MEDIUM OIL RESERVOIR OF UPPER INDUS BASIN OF PAKISTAN

Previously, air injection is exclusively used in light oil reservoirs; however, laboratory research has shown that air injection can also be very efficient for medium and heavy oil recovery. Due to the low cost of air injection and its indefinite availability, it has an economic advantage over other Enhanced Oil Recovery methods. This study is carried out in an experiment conducted on air injection into medium oil reservoirs. To better understand the air injection procedure for enhancing oil recovery from the X field's medium oil (26.12 °API) of Pakistan reservoir, 14 runs were performed. The effects of air flux, porous media, temperature, and pressure on oxidation reaction rates were explored and measured. The consumption of oxygen at a rate of 90% was determined. At a moderate pressure of 7300 kPa, a significant oil recovery of around 81% of the original oil in place was observed. Increased air flux and low permeability can have a more significant effect on medium oil recovery. The technique produced flue gases that were exceptionally low in carbon oxides, with a typical gas composition of 12% CO2, 6% CO, and unreacted oxygen. This research will contribute to a better knowledge of the air injection method and allow for the optimum performance for a specified reservoir. In the Enhanced oil recovery, a less costly process using this method will be inspiring due to recovering oil in this region.

Acute Effects of Vibration Foam Rolling with Light and Moderate Pressure on Blood Pressure and Senior Fitness Test in Older Women

Vibration foam rolling (VR) can improve flexibility and sports performance. However, blood pressure (BP), heart rate (HR) and senior fitness test (SFT) responses induced by an acute VR session in older women are currently unknown. Fifteen healthy women (72.90 ± 4.32 years) completed three separated randomly sequenced experimental visits. During each visit, they started with a warm-up protocol (general warm up (GW): walking + static stretching (SS), SS + VR with light pressure (VRL), or SS + VR with moderate pressure (VRM)), and completed BP, HR, SFT measurements. The systolic BP increased significantly after all three warm up protocols (p < 0.05). Both VRL and VRM protocols induced statistically significant improvements (effect size range: 0.3–1.04, p < 0.05) in the senior fitness test (back scratch, 30 s chair stand, 30 s arm curl, and 8 foot up and go), as compared to the GW. In addition, the VRM showed greater improvement for the 2 min step test when comparing with the VRL. Therefore, including VR in a warm-up protocol can result in superior SFT performance enhancement than the GW does in healthy older women.

A millisecond passive micromixer with low flow rate, low sample consumption and easy fabrication

Fast mixing of small volumes of solutions in microfluidic devices is essential for an accurate control and observation of the dynamics of a reaction in biological or chemical studies. It is often, however, a challenging task, as the Reynolds number (Re) in microscopic devices is typically < 100. In this report, we detail a novel mixer based on the “staggered herring bone” (SHB) pattern and “split-recombination” strategies with an optimized geometry, the periodic rotation of the flow structure can be controlled and recombined in a way that the vortices and phase shifts of the flow induce intertwined lamellar structures, thus increasing the contact surface and enhancing mixing. The optimization improves the mixing while using a low flow rate, hence a small volume for mixing and moderate pressure drops. The performances of the patterns were first simulated using COMSOL Multiphysics under different operating conditions. The simulation indicates that at very low flow rate (1–12 µL·min−1) and Re (3.3–40), as well as a very small working volume (~ 3 nL), a very good mixing (~ 98%) can be achieved in the ms time range (4.5–78 ms). The most promising design was then visualized experimentally, showing results that are consistent with the outcomes of the simulations. Importantly, the devices were fabricated using a classical soft-lithography method, as opposed to additive manufacturing often used to generate complex mixing structures. This new device minimizes the sample consumption and could therefore be applied for studies using precious samples.

Ab Initio Calculation of Li-Sn System: Unraveling New Phases of Superconducting Materials with Increasing Compression

Stoichiometry, crystal compound, electronic attributes and superconductivity of compressed lithium-tin composites have been thoroughly studied using quantum mechanical genetic algorithm approach and the first principles computations based on density functional theory. Our simulations at moderate pressure (5-20 GPa) predict a complex convex hull diagram, with the following stable Li‑rich phases: I4/mmm-Li6Sn2, -Li7Sn2, -Li5Sn2, Ama2-Li4Sn2, -Li5Sn2, -Li6Sn2, C2/m-Li4Sn1, P21/m-Li6Sn2, -Li7Sn2 and Cmcm-Li4Sn2. Careful examination at their independent elastic parameters reveals sufficient mechanical stability in them. These phases are metallic system, with reasonably high electron concentration near to Fermi level or N(EF) that ranges from 0.6 to 2.4 states/eV cell. It is also interesting for us to observe soft modes and steep-flat energy bands at Fermi levels of Li6Sn2 structures which are stable throughout the pressure range. These features are prerequisites for superconducting behavior. Linear response function with Gaussian and tetrahedron methods reveals satisfactory superconducting transition temperature Tc (3.1 ~ 6.6 K) and Tc (2.1 ~ 2.4 K), respectively. Structural transition results for based elements Li and Sn agree well with literature thus signifying reliable prediction of intermediate phases.

The differences response of massage types with variation massage pressure on running speed in POPDA Sleman athletics

This study aims to improve the athlete's performance from the physiological aspect by knowing the differences in the response of sport massage and swedish massage with variations in pressure (light, medium, and heavy) on the hind limbs a 30 m running speed taken four times. This research is a quasi-experimental design, with the research subjects of POPDA Sleman athletic athletes with sample of 20 people. The sample was divided by matching pairs with the aim of both groups getting a balanced power. The treatments used are sports massage with movement manipulation (effleurage, tapotement, shaking/vibration) and swedish massage with movement manipulation (drainage, compression, tapotement, shaking/vibration) with pressure variation. The results showed that there were differences in the effect/good response of the type of sports massage treatment (group x) with moderate pressure. This is evidenced by the results of an increase in record time by an average of 0.36 seconds. Treatment of light pressure increased record time by an average of 0.28 seconds. Heavy pressure treatment increased record time by an average of 0.04 seconds. There is a difference in the effect/unfavorable response of the type of swedih massage treatment (group y) with all types of pressure, because it provides a decreased response time from pretest to posttest. It is proven by the decrease in the average time of 0.16 seconds on the light pressure treatment, the decrease in the average time of 0.24 seconds on the medium pressure treatment, and a decrease of 0.34 seconds on the heavy pressure treatment.

Existence of yttrium allotrope with incommensurate host-guest structure at moderate pressure: First evidence from computational approach

We predict an allotrope of yttrium with an incommensurate host-guest structure by using ab initio random structure searching technique, based on first-principles calculation. Along with, we propose a set analogous commensurate supercells, which is incommensurate ratio (c H /c G), by approximating the different the number of guest atoms in channels in along c axis of the host structure. Herein, our results show that c H /c G = 5/4 is energetically stable. Subsequently, an incommensurate host-guest structure is found to be thermodynamically and dynamically stable within harmonic level. The hybridization of spd explains the stability of the host-guest structure under high pressure conditions. The distributions of electrons between the host and guest atoms are indicated strong and weak electron localization of spd bonds. This findings suggest that the host-guest structure is more likely to be achieved experimentally in this metallic element at moderate pressure.