Pressure generation under deformation in a large-volume press

Deformation can change the transition pathway of materials under high pressure,thus significantly affects physical and chemical properties of matters.However,accurate pressure calibration under deformation is challenging and thereby causes relatively large pressure uncertainties in deformation experiments,resulting in the synthesis of complex multiphase materials.Here,pressure generations of three types of deformation assemblies were well calibrated in a Walker-type largevolume press(LVP)by electrical resistance measurements combined with finite element simulations(FESs).Hard Al_(2)O_(3) or diamond pistons in shear and uniaxial deformation assemblies significantly increase the efficiency of pressure generation compared with the conventional quasi-hydrostatic assembly.The uniaxial deformation assembly using flat diamond pistons possesses the highest efficiency in these deformation assemblies.This finding is further confirmed by stress distribution analysis based on FESs.With this deformation assembly,we found shear can effectively promote the transformation of C60 into diamond under high pressure and realized the synthesis of phase-pure diamond at relatively moderate pressure and temperature conditions.The present developed techniques will help improve pressure efficiencies in LVP and explore the new physical and chemical properties of materials under deformation in both science and technology.

A distinctive HPHT platform with different types of large-volume press subsystems at SECUF

Large-volume presses(LVPs)providing large volumes,liquid media,deformation capability,jump compression,and in situ measurements are in great demand for high-pressure research,particularly in the fields of geoscience,condensed matter physics,material science,chemistry,and biology.A high-pressure and high-temperature(HPHT)platform with different LVP subsystems,both solid-state and liquid environments,and nonequilibrium subsystems,has been constructed at the Synergetic Extreme Condition User Facility,Jilin University.This article describes the construction of the different subsystems and provides an overview of the capabilities and characteristics of the different HPHT subsystems.A large sample volume(1000 mm^(3))at 20 GPa is achieved through the use of a belt-type apparatus in the solid-state subsystem.HPHT conditions(1.8 GPa and 1000 K)are realized in the liquid subsystem through the use of a piston-cylinder-type LVP with optical diamond windows for in situ spectroscopic measurements.A maximum pressure jump to 10.2 GPa can be reached within 20 ms in the nonequilibrium subsystem with the use of an improved bladder-pressurization jump press.Some typical results obtained with different LVPs are briefly reviewed to illustrate the applications and advantages of these presses.In summary,the platform described here has the potential to contribute greatly to high-pressure research and to innovations in high-pressure technology.

A virtual thermometer for ultrahigh-temperature-pressure experiments in a large-volume press

Ultrahigh-temperature-pressure experiments are crucial for understanding the physical and chemical properties of matter.The recent development of boron-doped diamond(BDD)heaters has made such melting experiments possible in large-volume presses.However,estimates of temperatures above 2600 K and of the temperature distributions inside BDD heaters are not well constrained,owing to the lack of a suitable thermometer.Here,we establish a three-dimensional finite element model as a virtual thermometer to estimate the temperature and temperature field above 2600 K.The advantage of this virtual thermometer over those proposed in previous studies is that it considers both alternating and direct current heating modes,the actual sizes of cell assemblies after compression,the effects of the electrode,thermocouple and anvil,and the heat dissipation by the pressure-transmitting medium.The virtual thermometer reproduces the power-temperature relationships of ultrahigh-temperature-pressure experiments below 2600 K at press loads of 2.8-7.9 MN(~19 to 28 GPa)within experimental uncertainties.The temperatures above 2600 K predicted by our virtual thermometer are within the uncertainty of those extrapolated from power-temperature relationships below 2600 K.Furthermore,our model shows that the temperature distribution inside a BDD heater(19-26 K/mm along the radial direction and<83 K/mm along the longitudinal direction)is more homogeneous than those inside conventional heaters such as graphite or LaCrO_(3) heaters(100-200 K/mm).Our study thus provides a reliable virtual thermometer for ultrahigh-temperature experiments using BDD heaters in Earth and material sciences.

A Breakthrough in Pressure Generation by a Kawai-Type Multi-Anvil Apparatus with Tungsten Carbide Anvils

Expansion of the pressure range of Kawai-type multi-anvil presses (KMAPs) with tungsten carbide (WC) anvils is called for, especially in the field of Earth science. However, no significant progress in pressure generation has been made for 40 years. Our recent studies have expanded the pressure generation of a KMAP with WC anvils to 65 GPa, which is the world record for high-pressure generation in this device and is more than 2.5 times higher than conventional pressure generation. We have also successfully generated pressures of about 50 GPa at high temperatures. This work reviews our recently developed technology for high-pressure generation. High-pressure generation at room temperature and at high temperature was attained by integration of the following techniques:① a precisely aligned guideblock system,② a high degree of hardness of the second-stage anvils,③ tapering of the second-stage anvil faces,④ a high-pressure cell consisting of materials with a high bulk modulus, and ⑤ high thermal insulation of the furnace. Our high-pressure technology will facilitate investigation of the phase stability and physical properties of materials under the conditions of the upper part of the lower mantle, and will permit the synthesis and characterization of novel materials.

Aluminum solubility in bridgmanite up to 3000 K at the top lower mantle

The temperature dependence of the Al2O3 solubility in bridgmanite has been determined in the system MgSiO3–Al_(2)O_(3)at temperatures of 2750–3000 K under a constant pressure of 27 GPa using a multi-anvil apparatus.Bridgmanite becomes more aluminous with increasing temperatures.A LiNbO3-type phase with a pyrope composition(Mg_(3)Al_(2)Si_(3)O_(12))forms at 2850 K,which is regarded as to be transformed from bridgmanite upon decompression.This phase contains 30 mol%Al_(2)O_(3)at 3000 K.The MgSiO3 solubility in corundum also increases with temperatures,reaching 52 mol%at 3000 K.Molar volumes of the hypothetical Al_(2)O_(3)bridgmanite and MgSiO_(3)corundum are constrained to be 25.950.05 and 26.24±0.06 cm^(3)/mol,respectively,and interaction parameters of non-ideality for these two phases are 5.6±0.5 and 2.2±0.5 KJ/mol,respectively.The increases in Al^(2)O^(3)and MgSiO^(3)contents,respectively,in bridgmanite and corundum are caused by a larger entropy of Al_(2)O_(3)bridgmanite plus MgSiO_(3)corundum than that of MgSiO_(3)bridgmanite plus Al_(2)O_(3)corundum with temperature,in addition to the configuration entropy.Our study may help explain dynamics of the top lower mantle and constrain pressure and temperature conditions of shocked meteorites.

Expression Analysis of Heat Shock Protein 70 Gene in Rice(Oryza sativa L.)

[Objectives]This study was conducted to construct a pColdI-HSP70 recombinant prokaryotic expression vector.[Methods]With rice‘N22’as the test variety,hydroponic experiments were set up for rice seedlings with normal growth(CK),high temperature treatment(H),drought treatment(D)and drought-high temperature cross treatment(DH).The recombinant prokaryotic expression vector was constructed by the method of prokaryotic expression,and its induction expression time,IPTG concentration and temperature were optimized.[Results]The pColdI-HSP70 expression vector was successfully constructed,and the fusion protein was highly expressed in host strain BL21,and the expressed proteins were all in a soluble form.By optimizing the induction expression conditions,it was found that the optimal expression conditions were the IPTG concentration of 0.5 mmol/L and induction at 20℃for 36 h.The expression analysis of the rice HSP70 gene under different stress treatments was carried out by qRT-PCR technology,and it was found that H,D and DH stresses all could induce its expression,and its expression levels were 4.65,1.40 and 17.66 times higher than that of the CK group,respectively.[Conclusions]This study lays a solid foundation for the isolation,purification and functional study of rice HSP70 proteins.

Chinese Fetal Growth:A Multicenter Cohort Study Based on Fetal Ultrasound Measurements

Objective:To build a reference fetal growth chart for the Chinese population based on fetal ultrasound measurements.Methods:This was a multicenter,population-based retrospective cohort study.Longitudinal ultrasound measurement data were collected from 24 hospitals in 18 provinces of China from 1st September through 31st October of 2019.The estimated fetal weight(EFW)was calculated based on head circumference,abdominal circumference,and femur length using Hadlock formula 3.Fetal growth curves were estimated using a two-level linear regression model with cubic splines.All participants were divided into two groups:the northern group(n=5829)and the southern group(n=3246)based on the geographical division of China and male fetus group(n=4775)and female fetus group(n=4300)based on fetal gender.The EFW was compared by fetal gender and geographical group.All statistical models were adjusted for maternal sociodemographic characteristics.Results:A total of 9075 participants with 31,700 ultrasound measurement records were included in this study.Male fetuses demonstrated significantly larger EFW compared to female ones starting at 16 weeks of gestation and extending to delivery(global testP<0.01).The overall geographic difference in EFW was significant(global testP=0.03),and week-specific comparisons showed that the northern group had a greater EFW starting at 15 weeks of gestation and extending to 29 weeks of gestation,although this difference did not extend to the time of delivery.TheZ-score of EFW confirmed that our Chinese fetal growth charts differed from previously published standards.Conclusion:This study provides EFW and ultrasound biometric reference measurements for Chinese fetuses and reveals differences from other fetal growth charts.The chart is worth promoting in more regions of China but should be tested prudently before use.