Evolution of superconductivity and charge order in pressurized RbV3Sb5

The kagome metals AV3Sb5 (A = K, Rb, Cs) under ambient pressure exhibit an unusual charge order, from which superconductivity emerges. In this work, by applying hydrostatic pressure using a liquid pressure medium and carrying out electrical resistance measurements for RbV3Sb5, we find the charge order becomes suppressed under a modest pressure p c (1.4 < p c < 1.6 GPa), while the superconducting transition temperature T c is maximized. T c is then gradually weakened with further increase of pressure and reaches a minimum around 14.3 GPa, before exhibiting another maximum around 22.8 GPa, signifying the presence of a second superconducting dome. Distinct behaviors in the normal state resistance are found to be associated with the second superconducting dome, similar to KV3Sb5. Our findings point to qualitatively similar temperature-pressure phase diagrams in KV3Sb5 and RbV3Sb5, and suggest a close link between the second superconducting dome and the high-pressure normal state resistance.

Testing the Modified Subchannel TEMPA-SC Code in Comparison with Experiments and Other Computer Codes

The paper describes a modified version of the TEMPA-SC computer program designed to calculate temperature fields in bundles of rods cooled by a supercritical pressure medium. This version of the program is based on the subchannel method that was used in the TEMPA-1F program, developed earlier in the OKB "GIDROPRESS" for calculating heat and mass transfer in the core of VVER-type reactors cooled by single-phase water at subcritical pressure. As the relations that close the system of equations of mass, momentum, and energy conservation, the new version of the program includes correlations for calculating heat transfer and friction resistance, taking into account the strong dependence of the properties of the coolant on temperature and pressure. In particular, the use of the universal calculation model of heat transfer, developed by the authors of this paper, allows us to perform calculations in a wide range of flow parameters of various media, including the modes of normal, improved and deteriorated heat transfer. The results of tests of the TEMPA-SC program are presented in comparison with the available experimental data for water and modeling media (carbon dioxide, freons R-12 and R-134a) at supercritical pressures, as well as with the published data of calculations by using similar subchannel programs (COBRA-SC, ASSERT-PV) and CFD codes. A satisfactory agreement between the calculated and experimental data is shown.

High-pressure thermal conductivity and compressional velocity of NaCl in B1 and B2 phase

Sodium chloride (NaCl) is an important, commonly used pressure medium and pressure calibrant in diamond-anvil cell (DAC) experiments. Its thermal conductivity at high pressure–temperature (P–T) conditions is a critical parameter to model heat conduction and temperature distribution within an NaCl-loaded DAC. Here we couple ultrafast optical pump-probe methods with the DAC to study thermal conductivity and compressional velocity of NaCl in B1 and B2 phase to 66 GPa at room temperature. Using an externally-heated DAC, we further show that thermal conductivity of NaCl-B1 phase follows a typical T−1 dependence. The high P–T thermal conductivity of NaCl enables us to confirm the validity of Leibfried-Schlömann equation, a commonly used model for the P–T dependence of thermal conductivity, over a large compression range (~ 35% volume compression in NaCl-B1 phase, followed by ~ 20% compression in the polymorphic B2 phase). The compressional velocities of NaCl-B1 and B2 phase both scale approximately linearly with density, indicating the applicability of Birch’s law to NaCl within the density range we study. Our findings offer critical insights into the dominant physical mechanism of phonon transport in NaCl, as well as important data that significantly enhance the accuracy of modeling the spatiotemporal evolution of temperature within an NaCl-loaded DAC.

Evidence for and significance of the Late Cretaceous Asteroussia event in the Gondwanan Ios basement terranes

The Late Cretaceous Asteroussia event as recorded in the Cyclades is a potential key to the tectonic evolution of Western Tethys. Microstructural analysis and 40Ar/39Ar geochronology on garnet–mica schists and the underlying granitoid basement terrane on the island of Ios demonstrates evidence of a Late Cretaceous high-pressure, medium-temperature (HP–MT) metamorphic event. This suggests that the Asteroussia crystalline nappe on Crete extended northward to include these Gondwanan tectonic slices. In this case, the northern part of the Asteroussia nappe (on Ios) is overlain by the terrane stack defined by the individual slices of the Cycladic Eclogite–Blueschist Unit, whereas in the south (in Crete) the Asteroussia slices are near the top of a nappe stack defined by the individual tectonic units of the external Hellenides. This geometry implies that accretion of the Ios basement terrane involved a significant leap of the subduction megathrust (250–300 km) southward. Accretion needs to have commenced at or about ∼38 Ma, when the already partially exhumed slices of the Cycladic Eclogite–Blueschist Unit began to thrust over the Ios basement. By ∼35–34 Ma, the subduction jump had been accomplished, and renewed rollback began the extreme extension that led to the exhumation of the Ios metamorphic core complex.

Densification of agro-residues for sustainable energy generation: an overview

The global demand for sustainable energy is increasing due to urbanization, industrialization, population, and developmental growth. Transforming the large quantities of biomass resources such as agro-residues/wastes could raise the energy supply and promote energy mix. Residues of biomass instituted in the rural and industrial centers are enormous, and poor management of these residues results in several indescribable environmental threats. The energy potential of these residues can provide job opportunities and income for nations. The generation and utilization of dissimilar biomass as feedstock for energy production via densification could advance the diversity of energy crops. An increase in renewable and clean energy demand will likely increase the request for biomass residues for renewable energy generation via densification. This will reduce the environmental challenges associated with burning and dumping of these residues in an open field. Densification is the process of compacting particles together through the application of pressure to form solid fuels. Marketable densification is usually carried out using conventional pressure-driven processes such as extrusion, screw press, piston type, hydraulic piston press, roller press, and pallet press (ring and flat die). Based on compaction, densification methods can be categorized into high-pressure, medium-pressure, and low-pressure compactions. The common densification processes are briquetting, pelletizing, bailing, and cubing. They manufacture solid fuel with desirable fuel characteristics—physical, mechanical, chemical, thermal, and combustion characteristics. Fuel briquettes and pellets have numerous advantages and applications both in domestic and industrial settings. However, for biomass to be rationally and efficiently utilized as solid fuel, it must be characterized to determine its fuel properties. Herein, an overview of the densification of biomass residues as a source of sustainable energy is presented.

Evaluation of Passive Safety Injection System Performance Under Large Break LOCA for Qinshan PWR

In this work, a brand new passive safety injection system has been designed for the ocean-based Qinshan Phase I nuclear power plant to update and replace the traditional active ones. The passive safety injection system is made up of high pressure, medium pressure, lower pressure safety injection system, and a two-stage automatic depressurization system. To evaluate the safety injection system performance, double-ended cold leg large break LOCA has been analyzed by best-estimated safety analysis RELAP5 code. The main operation and safety parameters such as primary system pressure, safe injection mass flow rates, core water level, and peak cladding temperature have been presented. The results conclude that the safety injection system can act as similar to that of the AP1000, which can assure sufficient core cooling and keep the reactor covered by the cold water under the most severe LBLOCA condition.

Evaluation of Sprinkler Irrigation Evaporation Losses in Ilaro, Ogun State, South Western Nigeria

Under the prevailing climate change the world is currently facing, efficient irrigation water management is essential to ensure food security, especially in countries with similar climate to Nigeria. Hence, this study was undertaken at the Research Farm of Federal Polytechnic, Ilaro, Ogun State, Nigeria to evaluate evaporation losses during sprinkler irrigation between March and July 2019. Experiments were performed using 360 rotating sprinkler and single nozzle of diameter 3 mm, while due cognizance was taken of the prevailing climatic conditions. Three operating pressures, namely, 50 kPa, 100 kPa and 150 kPa, representing low pressure, medium pressure and high pressure, respectively, were used. The results showed that operating pressures influence droplet sizes, droplet heights and flow rate during the experiment. In addition, it was observed that at operating pressures of 50 kPa, 100 kPa and 150 kPa, mean percentage of evaporation losses were 8.88%, 13.21% and 16.46%, respectively, indicating that evaporation losses increased with increasing operating pressure. Further analysis showed that percentage evaporation losses increased at higher relative humidity, thereby emphasizing the predominance of air temperature and wind velocity as climatic variable influencing sprinkler evaporation losses. The relationship between wind velocity (Vw ) and air temperature (Ta) and to predict evaporation losses (E ) was a function of E = 7.968Vw + 0.393Ta – 19.977. Therefore, it was concluded that, both climatic factors and operating pressures influence the rate of evaporation losses during sprinkler irrigation, adequate attention should be paid to variation of climatic variables since sprinklers are sold with their specified operating pressures.

Dry Ice Self-Pressurised Rapid Freezing (DryIce SPRF): all you need to cool for cryofixation of nematodes is dry ice

Summary Cryofixation immediately arrests all biochemical, physiological and dynamic processes underway in the sample in their present state, resulting in both excellent preservation of the specimen’s ultrastructure and its antigenicity. Cryofixation involves extremely rapid cooling of specimens, creating an amorphous, or ‘non-crystalline’, state of water containing no detectable ice crystals, a process dependent on pressure, medium composition and temperature. Self-Pressurised Rapid Freezing (SPRF) employs plunge freezing of specimens in a sealed copper tube into a cryogen such as nitrogen slush (−210°C), liquid nitrogen (−196°C), ethane (−183°C) or propane (−120°C). In this study we have explored the use of SPRF with cooled acetone on dry ice (−80°C) as the cryogen, a method named DryIce SPRF. Although with this relatively high temperature amorphous water cannot be formed, we have demonstrated that the ultrastructural and antigenicity results after DryIce SPRF on Caenorhabditis elegans are perfectly comparable with those achieved using High Pressure Freezing and SPRF. Thus, with sufficient pressure optimal results, with ice crystals below the resolution of transmission electron microscopy, can be achieved even at −78°C. Furthermore, a huge advantage of DryIce SPRF over other techniques is its use of affordable, easily available and safe products.

Can quasicrystals survive in planetary collisions?

We investigated the compressional behavior of i-AlCuFe quasicrystal using diamond anvil cell under quasi-hydrostatic conditions by in situ angle-dispersive X-ray powder diffraction measurements (in both compression and decompression) up to 76 GPa at ambient temperature using neon as pressure medium. These data were compared with those collected up to 104 GPa using KCl as pressure medium available in literature. In general, both sets of data indicate that individual d-spacing shows a continuous decrease with pressure with no drastic changes associated to structural phase transformations or amorphization. The d/d0, where d0 is the d-spacing at ambient pressure, showed a general isotropic compression behavior. The zero-pressure bulk modulus and its pressure derivative were calculated fitting the volume data to both the Murnaghan- and Birch-Murnaghan equation of state models. Results from this study extend our knowledge on the stability of icosahedrite at very high pressure and reinforce the evidence that natural quasicrystals formed during a shock event in asteroidal collisions and survived for eons in the history of the Solar System.