Elevating Pressure Research Articles

Elevated hydrostatic pressure enhances the potential for microbially mediated carbon sequestration at the sediment–water interface in a deep-water reservoir by modulating functional genes and metabolic pathways

Microbially mediated carbon cycling is essential for the production of refractory dissolved organic carbon and subsequent formation of stable carbon sinks at the sediment–water interface (SWI) in aquatic ecosystems, such as lakes. It remains unclear how this process is influenced by hydrostatic pressure changes due to water level fluctuation in deep-water reservoirs. Here, a microcosm simulation experiment was carried out to decipher the response of microbially mediated carbon cycling to various hydrostatic pressures (i.e., 0.1 MPa [atmospheric pressure], 0.2 MPa, 0.5 MPa, 0.7 MPa) at the SWI in Jinpen Reservoir, Shaanxi Province, China. The response mechanisms of microbial community structure, functional gene abundance, and metabolic pathway activity associated with carbon cycling were explored by metagenomics and metabolomics. Results showed that the number of microbial species in sediment samples increased with elevating pressure. The relative abundance of archaea also increased from 0.2% to 0.4% as a consequence of pressure elevation, accompanied by 0.17% and 0.03% decrease in bacteria and fungi, respectively. In contrast with low pressures, high pressures allowed the microbial communities to form a more closely connected network, which maintained more complex interspecies interactions and greater system stability. High pressures additionally improved the abundances of specific functional genes (e.g., ALDO, ACO, sdhA, and sdhC) in carbon metabolic pathways, promoted carbon fixation by the reductive pentose phosphate (Calvin) and citrate cycles, and hindered methanogenesis. Piezophilic taxa (e.g., Gammaproteobacteria, Alphaproteobacteria, Bacteroidetes) and genes (e.g., ompH, asd) were identified among carbon cycling-associated microbial communities. The piezophilic genes, which were mainly present in the Proteobacteria phylum, increased first and then decreased in abundance with elevating pressure. The findings indicate that elevated hydrostatic pressure contributes to carbon sequestration at the SWI in deep-water reservoirs by changing carbon cycling-associated microbial species, as well as relevant functional genes and metabolic pathways.Graphical

Effect of pressure on regenerative cooling process of endothermic hydrocarbon fuel at severe pyrolysis conditions

Regenerative cooling technology with supercritical aviation kerosene as coolant is the optimal thermal management method for advanced aero engines. In order to fill the gap in existing research on the pressure effects at severe pyrolysis, the influence of pressure on the flow field, pyrolysis behaviours, heat transfer, and surface coking are numerically investigated in this study. The results indicate that the velocity-temperature curves at different pressures have two intersections due to the difference in initial pyrolysis temperature, reaction rate, and product distribution. Fuel pyrolysis more easily occurs at high pressure, and elevating pressure improves the fuel heat sink. Besides, a special deterioration of heat transfer is found at high conversion rates because of the combined contribution of weakened primary endothermic reaction and enhanced secondary exothermic reaction. Heat transfer deterioration is delayed at 3.5 MPa due to the high initial pyrolysis temperature and significant flow acceleration. The primary pyrolysis reaction provides more than 80% chemical heat sink and 60% flow acceleration at fully cracked conditions at 5.0 MPa. In addition, inhibiting catalytic coking is the principal method to reduce carbon deposition, and more attention should be paid to carbon deposition under high pressure. The results obtained in this study are expected to provide insights into the selection of operating pressures for advanced aero engines.

Enhancement of electrical conductivity to metallization of Mn3-xFexO4 spinel and postspinel with elevating pressure

Electrical conductivity enhancement from semiconductor to metallization in Mn3-xFexO4 postspinel under extreme conditions is discussed herein. Neutron diffraction experiments have allowed precise analysis of the Mn3-xFexO4 structure by virtue of the significant difference in coherent scattering lengths between Mn (−3.73 fm) and Fe (9.54 fm). An Mn3-xFexO4 spinel solid solution transforms into an orthorhombic postspinel phase. Neutron diffraction studies have proved that cubic MnFe2O4 spinel and tetragonal Mn2FeO4 transform into a high-pressure postspinel structure (CaMn2O4-type marokite) above pressures of 18 GPa and 14 GPa, respectively. The transition pressure decreases with increasing Mn content.Synchrotron X-ray Mössbauer experiments have revealed the effects of high pressures on the distribution of Fe2+ and Fe3+ at the tetrahedral and octahedral sites in the spinel structure. MnFe2O4 and Mn2FeO4 are ferrimagnetic under ambient conditions, and they show sextet spectral features with hyperfine structure elicited by internal magnetic fields. The high-pressure postspinel polymorph shows paramagnetic character.Electron hopping persists as the charge-transport mode. The temperature dependence of resistivity indicates that the spinel phases show semiconductor properties. Electrical conduction is derived from electron hopping between cations at the tetrahedral (A) and octahedral (B) sites. A shortened B–B distance promotes higher conduction during compression and greater electron mobility between adjacent B cations. The occupancies of Fe2+ and Fe3+ at the B sites of MnFe2O4 are much higher than in the case of Mn2FeO4. The high-pressure postspinel polymorph of transforms into a phase with metallic-like character due to band conduction in the high-pressure region. Theoretical approaches have revealed the densities of state of these manganese ferrites. To verify the metallic behavior of postspinel Mn2FeO4 under high pressures, we have applied a combined approach of density functional theory and dynamical mean field theory. The spectral function clearly shows metallic character. Fe d orbitals are strongly renormalized compared to Mn d orbitals.

Study on pressurized isothermal pyrolysis characteristics of low-rank coal in a pressurized micro-fluidized bed reaction analyzer

In order to investigate the pressurized isothermal pyrolysis characteristics of coal, the effect of pressure on gas release characteristics and the kinetics of pressurized isothermal pyrolysis are explored for the first time in a pressurized micro-fluidized bed reaction analyzer (P-MFBRA). This work finds that the yields of CO2, CO, CH4, and H2 increases with temperature and pressure. The difference in the order of gas-releasing reduces as temperature and pressure rises, but that of gas-ending first decreases and then increases with pressure. The most probable mechanism functions of CO2, CO and CH4 change from shrinking core model to homogeneous model at 1 MPa, 0.8 MPa and 0.5 MPa, respectively, showing that reaction is controlled by chemistry under low pressure but affected by diffusion effect with elevating pressure. The rate constant and activation energy (Ea) of each gas appear an increasing-decreasing tendency and the difference between Ea of each gas reduces with pressure. Compared with non-isothermal experiments, the Ea (20.8–475 kJ mol−1) and pre-exponential factor in P-MFBRA are less than those (70–150 kJ mol−1) in the pressurized thermogravimetric analyzer (P-TGA), indicating P-MFBRA can effectively reduce the diffusion inhibition, and the kinetics obtained is close to the reaction in industrial fluidized bed reactor.

Programas de rastreamentos dos valores da pressão arterial no mundo: revisão integrativa

Objetivo: analisar as evidências disponí­veis na literatura sobre os programas de rastreamentos dos valores da pressão arterial no mundo. Método: revisão integrativa da literatura, realizada no mês de setembro de 2019 com artigos no perí­odo de 2015 a 2019, nas bases de dados National Library of Medicine National Institutes of Health, Literatura latino-americana e do Caribe em ciências da saúde, Web of Science, no Banco de Dados Scopus e na Biblioteca Cochrane. Resultados: Um total de 13 estudos foi selecionado para integrar esta revisão. Rastreamentos da pressão arterial realizados ressaltam a importância do mesmo para conscientização, detecção precoce, controle e prevenção de valores da pressão elevadores. Conclusão: Programa de rastreamento da pressão arterial é uma estratégia de baixo custo e elevada eficácia, para identificação do diagnóstico, tratamento e controle da hipertensão arterial, seja em paí­ses desenvolvidos e em desenvolvimento, e ao mesmo tempo contribui para diminuição de riscos para doenças cardiovasculares.

Study on Pressurized Isothermal Pyrolysis Characteristics of Low-Rank Coal in a Pressurized Micro-Fluidized Bed Reaction Analyzer

The development of clean coal technology has prompted the study of pressurized pyrolysis for coal. Most of the existing studies are non-isothermal kinetic experiments conducted in P-TGA, which cannot reflect the particle movement in actual furnace, so there is a lack of relevant data on pressurized isothermal pyrolysis characteristics. In this work, the effects of pressure on the characteristics of gas release and pressurized isothermal pyrolysis kinetics are explored in P-MBFRA. This work finds that the yields of CO2, CO, CH4, and H2 increases with temperature and pressure. The most probable mechanism function of CO2, CO and CH4 change from shrinking core model to homogeneous model at 1MPa, 0.8MPa and 0.5MPa, respectively, showing that reaction is controlled by chemistry under low pressure but affected by diffusion effect with elevating pressure. The rate constant and activation energy of each gas appear an increasing-decreasing tendency and the difference between activation energy of each gas reduces with pressure. Compared with non-isothermal experiments, the activation energy and pre-exponential factor in P-MBFRA are less than those in P-TGA, indicating P-MBFRA can effectively reduce the diffusion inhibition, and the kinetics obtained is close to the reaction in industrial fluidized bed reactor.

Isochronal Superposition of the Structural α-Relaxation and Invariance of Its Relation to the β-Relaxation to Changes of Thermodynamic Conditions in Methyl m-Toluate.

The dielectric spectra of methyl m-toluate (MMT) in supercooled liquid and glassy states were measured over wide ranges of temperature T at ambient and elevated pressures P. We found that the frequency dispersion of the loss peak contributed by the structural α-relaxation is invariant to changes of P and T, while keeping the loss peak frequency fα(T,P) constant. This isochronal superposition property of the α-relaxation holds for different choices of fα(T,P). The invariant frequency dispersions for the same fα(T,P) are also indicated by the fractional exponent βKWW in the Fourier transform of the Kohlrausch-Williams-Watts (KWW) function. Similarly, the fragility m index of MMT keeps approximately constant on varying pressure, largely different from H-bonded glass formers. The secondary β-relaxation at a frequency higher than fα(T,P) is found to shift to lower frequencies by elevating pressure in concert with the α-relaxation. The ratio τα(T,P)/τβ(T,P) is approximately unchanged to variations of T and P while keeping τα(T,P) constant. These properties observed in MMT offer experimental evidence of the dynamic correlation between α- and β-relaxations in pure small-molecule glass-formers.

On the equivalent effect of initial temperature and pressure coupling on the flame speed of methane premixed combustion under dilution

Abstract This study was conducted with methane as fuel and CO2 as diluent gas. The equivalent effect of initial temperatures (323–423 K) and pressures (0.1–0.3 MPa) coupling on methane-air premixed combustion flame propagation speed (i.e. increasing or decreasing initial temperature and pressure simultaneously to have same flame propagation speeds when equivalence ratio and fraction of CO2 are unchanged) was investigated under a series of fractions of CO2 (0%–16%) and equivalence ratios (0.9, 1.0, and 1.1). Laminar burning velocities of different test conditions with similar flame propagation speeds were investigated and flame instability was also analyzed. The results show that similar flame speeds can be obtained when elevating initial temperature and pressure synchronously under constant equivalence ratio and the fraction of CO2. Similar flame propagation speeds can lead to close laminar burning velocities and similar flame structures. Flame speed under higher initial temperature and pressure is more sensitive to temperature and pressure, but dilution can suppress this sensitivity. Flame instability is stronger under higher initial temperature and pressure. Hydrodynamic instability dominates and it is mainly influenced by flame thickness. Differences are also shown in pressure and temperature during non-laminar stage. Dilution can enhance the difference in combustion duration.

The properties and formation mechanism of oat β-glucan mixed gels with different molecular weight composition induced by high-pressure processing.

High pressure, an emerging nonthermal technology has been widely applied in food product modifications. The effects of oat β-glucan concentration and pressure on the properties of mixed gels with the different ratios of varying molecular weight (MW) β-gulcan induced by HPP were investigated. The results showed that the lowest β-glucan concentration forming a gel was 15% at 200 MPa, while 8% β-glucan was required to form a gel at 500 MPa. The gel intensity and textural properties increased with elevating β-glucan total concentration and pressure. The characteristic compact and smooth mixed gel formed with 12% β-glucan at a ratio of 50:50 at 400 MPa for 30 min. Under this optimal parameters, the mixed solution showed a relatively lower particle size and turbidity, and the hydrogen bonding and electrostatic interaction played the main role during the gel formation process by high pressure. In addition, the core molecular structure of β-glucan was maintained in the mixed gel formed under the optimal parameters.

Influence of Bubbles on Insulation Properties of LN2 for SFCL Under Lightning Impulse and DC Voltage

As one of the most effective ways for the suppression and interruption of short-circuit current in voltage source converter based high-voltage direct current (VSC-HVdc) power systems, superconducting fault current limiter (SFCL) has received more and more attention, especially the resistive SFCL. However, when the resistive SFCL is in the current limiting state or overload operation, a large amount of bubbles will be generated on the surface of superconducting tape, thereby affecting the insulation performance of the SFCL. Experiments are performed by using a heater-built-in electrode system where bubbles are generated from the surface of the ground electrode. The test can simulate the actual working condition. The effect of bubbles on breakdown voltage of liquid nitrogen (LN2) is investigated under different types of voltage (negative lightning impulse, positive dc voltage, and composite voltage of negative lightning impulse and positive dc voltage) and different pressures. The results show that the breakdown voltage of LN2 decreases with the increase of the number of bubbles regardless the type of voltage, and elevating pressure is an effective way to improve the insulation strength of LN2. All the test data can be used as the theoretical basis for insulation design of resistive SFCL.

ZnO/CuO Nanocomposite for Gas Phase Electrochemical Conversion of CO2 to CO at Elevated Pressure

Over the past few years, electrochemical reduction of CO2 (ERC) has attracted a lot of interest among researchers to convert CO2 into value added products using renewable energy.1 Thermodynamic reduction potential of ERC is close to that of hydrogen reduction potential (HER). Moreover, ERC can lead to many products i.e. CO, CH4, C2H4, C2H6, HCOOH, CH3OH etc. depending upon the catalyst and reaction conditions.2 Hence, catalysts play a crucial role in selective electroreduction of CO2. Therefore, majority of the research has been carried out on developing catalyst for selective ERC and most of the studies were conducted in aqueous phase ERC.3 The main limitation of this approach is the CO2 mass transfer limitations due to the low solubility of CO2 in water. However, sufficient studies relevant to the technological development of the direct gas phase ERC are still needed. In this presentation we will discuss our work on role of pressure in improving gas phase ERC carried out in zero gap cell. We have synthesised ZnO/CuO nanocomposite and ZnO nanoparticles by two methods (wet chemical method and hydrothermal method). We have also synthesised a polyethyleneimine (PEI) based anion exchange membrane. Setup was systematically tested at various operating conditions. Results show that CO2 adsorption on the catalyst aided by the amine functional groups on membrane can be further enhanced by increasing the pressure. As the pressure slightly elevated to 0.5 bar from ambient pressure, HER was supressed and CO faradaic efficiency (FECO) of ~30% was reached. Moreover, current density was increased to ~50mA/cm2 from 4 mA/cm2. In this presentation we will compare the FECO, conversion and current densities of the synthesised electrocatalyst and seek to describe how elevating pressure increases rate of ERC on particular catalyst. References D. Raciti and C. Wang, ACS Energy Lett., 3, 1545-1556 (2018).L.M. Aeshala, R. U. and A. Verma, Phys. Chem. Chem. Phys., 16,17588 (2014).B. Kim, F. Hillman, M. Ariyoshi, S. Fujikawa and P.J.A. Kenis, J. Power Sources, 312, 192 – 198 (2016).

β-PtO2: Phononic, thermodynamic, and elastic properties derived from first-principles calculations

Beta-PtO2 is a useful transition metal dioxide, but its fundamental thermodynamic and elastic properties remain unexplored. Using first-principles calculations, we systematically studied the structure, phonon, thermodynamic and elastic properties of beta-PtO2. The lattice dynamics and structural stability of beta-PtO2 under pressure were studied using the phonon spectra and vibrational density of states. The vibrational frequencies of the optical modes of beta-PtO2 increase with elevating pressure; this result is comparable with the available experimental data. Then, the heat capacities and their pressure responses were determined based on the phonon calculations. The pressure dependence of the Debye temperature was studied, and the results are compared in two distinct aspects. The elastic moduli of beta-PtO2 were estimated through the Voigt-Reuss-Hill approximation. The bulk modulus of beta-PtO2 increases linearly with pressure, but the shear modulus is nearly independent of pressure. Our study revealed that the elastic stiffness coefficients C44, C55 and C66 play a primary role in the slow variation of the shear modulus.

Detachment mechanisms of turbulent non-premixed jet flames at atmospheric and elevated pressures

The stability limits of a turbulent flame in a practical combustor are important characteristics that influence its performance. The mechanisms controlling the stability limits of turbulent non-premixed flames are examined here in the canonical configuration of a fuel jet in co-flow air. This study focuses on the conditions leading to the detachment of flames from the injector nozzle by means of an experimental parametric study in which pressure (1 ≤ P ≤ 10 bar), fuel (methane and ethane), nozzle wall thickness (t = 0.20 mm, 0.58 mm, and 0.89 mm), jet velocity (0.5 ≤ Uj ≤ 16.5 m s−1), and co-flow velocity (Uc = 0.3 m s−1, 0.6 m s−1, and 0.9 m s−1) are varied. It is shown that the mechanism leading to detachment depends on the ratio of the nozzle wall thickness to the laminar flame thickness. If this ratio is smaller than 3, the nozzle is “thin” and type I detachment occurs (flame base stability lifting). In this case, the detachment velocity decreases with pressure and is proportional to the laminar burning velocity. If the ratio is larger than 3, the nozzle is “thick” and type II detachment occurs (local flame extinction lifting). Then, the detachment velocity is controlled by the extinction strain rate. Experiments also show that the Kolmogorov scale of turbulence regulates local flame extinction and type II detachment and a model is proposed to predict detachment for any fuel, pressure, and nozzle wall thickness using the computed extinction strain rate and the Kolmogorov time scale. Finally, the data show that elevating pressure allows stabilizing attached non-premixed jet flames with high Reynolds numbers without the need for complex stabilization strategies such as pilot flames, swirl, or oxygen/hydrogen enrichment. Pressure allows studying flame/turbulence interactions at Reynolds numbers relevant to practical applications while conserving simple configurations amenable to diagnostics and modeling.

In-situ observation of the structural change in MgO-B2O3-SiO2 glass at high pressure and the permanent structural change

A 41.6MgO-27.1B2O3-31.2SiO2 glass was synthesized by container-less levitation method. B K-edge X-ray absorption near edge structure (XANES) spectroscopy was used to quantify the coordination of boron in the as-made glass, resulting in ~72% of boron in 3-fold coordination. Raman spectroscopy indicated that the glass structure includes depolymerized borate units, which are pyroborate (B2O54−) and ring and/or chain-type metaborate (B3O63−, (BO2O−)∞) groups. The structural changes in the glass under hydrostatic condition were investigated by high-pressure Raman spectroscopy within a diamond anvil cell at pressures up to 8.5 GPa. On the borate structure, metaborate groups decreased with pressure. In contrast, triborate groups, which include tetrahedrally coordinated boron and have a fully polymerized borate network, increased; suggesting that the coordination transformation of B and polymerization were induced via compression. However, the modification of the borate structure units seems to be reversible at least up to 8.5 GPa. As for the silicate network, Q0 and Q1 structures were responsible to compression. Specifically, Q0 could be replaced by Q1 with elevating pressure, which means that the silicate network becomes polymerized with pressure. Whereas, structure of glass samples recovered from the pressure higher than 5 GPa displayed depolymerized silicate network, as dissociation of Q2 to Q1. The observed structural changes in the silicate network implied a partial change of the coordination number of Si4+ ions, which can be enhanced by the presence of a modifier cation with high field strength such as Mg2+.

Direct Evidence of Relaxation Anisotropy Resolved by High Pressure in a Rigid and Planar Glass Former.

Rigid molecular glass-formers with no internal degrees of freedom nonetheless have a single secondary β-relaxation. For a rigid and planar molecule, 1-methylindole (1MID), although a secondary relaxation is resolved at ambient pressure, its properties do not conform to the rules established for rigid molecules reported in early studies. By applying pressure to the dielectric spectra of 1MID, we find the single secondary relaxation splits into two. The slower one is pressure sensitive showing connections to the α-relaxation as observed in other rigid molecules, while the faster one is almost pressure insensitive and dominate the loss at ambient pressure. The two secondary relaxations, identified to associate with the out-of-plane and in-plane rotations of the rigid and planar 1MID, are resolved and observed for the first time by increasing density via elevating pressure.

Water-rock interaction during the diagenesis of mud and its prospect in hydrogeology

Mud is a fine, saturated and unconsolidated sediment with high moisture and abundant organic matter, mineral and microbe. As the burial diagenesis of mud proceeds, the water - rock - gas - organic matter - microbe in mud interact and co-evolve, forming mudstone or shale finally. During mud diagenesis, pore water not only changes over its own properties, but also participates in diagenetic reactions actively, and involves in the production of some mineral resources (hydrocarbon, biogenic gas, methane hydrate, etc) directly or indirectly. Researching water-rock interaction during mud diagenesis will be of great theoretical and practical significance to further understanding the genesis of natural groundwater, diagenetic reactions and mineralization, and has broad prospects in hydrogeology. With diverse high temperature and high pressure devices emerging, and the rapid expansion of in-situ detecting technology, simulating forwardly diagenetic processes of mud using indoor elevating temperature and pressure technology provides a new perspective for further researching water-rock interaction during the diagenesis of mud.

Structure and Symmetrization of Hydrogen Bonding in Ices VIII and X at High Pressure: A Density Functional Theory Approach

We study the change in structural properties of ice by taking initial structure of “ice VIII”, with space group symmetry I41/amd, as a function of elevating pressure up to 120 GPa in density-functional theory (DFT) level of calculations implemented by Quantum ESPRESSO package. Consistent with the standard laws of thermodynamics, our calculations show that the physical size (volume and cell parameters) of the unit cell compresses monotonically on increasing pressure. We also compare our DFT results of these parameters with the available experimental values performed at finite temperature. The comparison shows good agreement between the quantities, within 5%, with slightly higher experimental values. At 100 GPa of pressure, hydrogen atom comes exactly at the midpoint of two boneded oxygens, called hydrogen-bonded symmetrization, which at low pressure remains nearby one of the oxygens. This symmmetrized structure is characterized by a new phase of the system known as “ice X” and the boundary pressure, 100 GPa, defines the transition pressure (P0) for changing phase from “ice VIII” to “ice X”. The transition pressure (P0) of the present work agrees well within 2% of previously reported results.Journal of Institute of Science and Technology, 2014, 19(2): 14-19Journal of Institute of Science and Technology, 2014, 19(2): 14-18

Superconductivity emerging from a suppressed large magnetoresistant state in tungsten ditelluride.

The recent discovery of large magnetoresistance in tungsten ditelluride provides a unique playground to find new phenomena and significant perspective for potential applications. The large magnetoresistance effect originates from a perfect balance of hole and electron carriers, which is sensitive to external pressure. Here we report the suppression of the large magnetoresistance and emergence of superconductivity in pressurized tungsten ditelluride via high-pressure synchrotron X-ray diffraction, electrical resistance, magnetoresistance and alternating current magnetic susceptibility measurements. Upon increasing pressure, the positive large magnetoresistance effect is gradually suppressed and turned off at a critical pressure of 10.5 GPa, where superconductivity accordingly emerges. No structural phase transition is observed under the pressure investigated. In situ high-pressure Hall coefficient measurements at low temperatures demonstrate that elevating pressure decreases the population of hole carriers but increases that of the electron ones. Significantly, at the critical pressure, a sign change of the Hall coefficient is observed.

Enhancing the sintering ability of TiNx by introduction of nitrogen vacancy defects

Highly nitrogen-deficient non-stoichiometric TiNx powders within nitrogen vacancy defects (0.3<x<0.5) were prepared by mechanical alloying and consolidated by high pressure sintering. The effects of nitrogen vacancy defects, sintering temperature and pressure on densification and grain growth of TiNx were investigated for improving sintering ability and mechanical properties. Increasing nitrogen vacancy defects promoted densification and grain growth of TiNx. Nitrogen vacancies accelerated material transport and diffusion during sintering and altered strong covalent bonding nature was believed to result in enhanced sintering ability. Densification of TiNx was enhanced by increasing temperature and elevating pressure, grain growth was promoted by increasing temperature, whereas restrained by elevating pressure. TiNx (x=0.32) ceramic with relative density of 99.4% and average grain size of 21nm was obtained at 1200°C, 5GPa and 10min. Vickers hardness of 22.6GPa and fracture toughness of 5.0MPam1/2 were achieved.

Pressure effect on the superconductivity of Ca1−xLaxFeAs2 (x = 0.18) single crystal

Two steps of resistance decreases were observed in cooling Ca1−xLaxFeAs2 (x = 0.18) single crystal under high-pressure condition. The temperature T1 at which the high-T decrease takes place shows little pressure dependence. On the other hand, the low-T decrease was ascribed to a superconducting transition for the zero resistance. With elevating pressure P, both the onset and zero-resistance transition Tc's first increase and then decrease continuously, showing a dome-shape pressure phase diagram with an optimal pressure around 1.19 GPa. The positive-pressure effect of the superconducting transition demonstrates the possibility of exploring higher Tc's in the present material.