Structure Responsible for the Superconducting State in La3Ni2O7 at High-Pressure and Low-Temperature Conditions.

Very recently, a new superconductor with Tc = 80 K has been reported in nickelate (La3Ni2O7) at around 15-40 GPa conditions (Nature, 621, 493, 2023), which is the second type of unconventional superconductor, besides cuprates, with Tc above liquid nitrogen temperature. However, the phase diagram plotted in this report was mostly based on the transport measurement under low-temperature and high-pressure conditions, and the assumed corresponding X-ray diffraction (XRD) results were carried out at room temperature. This encouraged us to carry out in situ high-pressure and low-temperature synchrotron XRD experiments to determine which phase is responsible for the high Tc state. In addition to the phase transition from the orthorhombic Amam structure to the orthorhombic Fmmm structure, a tetragonal phase with the space group of I4/mmm was discovered when the sample was compressed to around 19 GPa at 40 K where the superconductivity takes place in La3Ni2O7. The calculations based on this tetragonal structure reveal that the electronic states that approached the Fermi energy were mainly dominated by the eg orbitals (3dz2 and 3dx2-y2) of Ni atoms, which are located in the oxygen octahedral crystal field. The correlation between Tc and this structural evolution, especially Ni-O octahedra regularity and the in-plane Ni-O-Ni bonding angles, is analyzed. This work sheds new light to identify what is the most likely phase responsible for superconductivity in double-layered nickelate.

Correction: 57Fe Mössbauer spectroscopy and high-pressure structural analysis for the mechanism of pressure-induced unique magnetic behaviour in (cation)[FeIIFeIII(dto)3] (cation = Ph4P and nPrPh3P; dto = 1,2-dithiooxalato).

Correction for '57Fe Mössbauer spectroscopy and high-pressure structural analysis for the mechanism of pressure-induced unique magnetic behaviour in (cation)[FeIIFeIII(dto)3] (cation = Ph4P and nPrPh3P; dto = 1,2-dithiooxalato)' by Ryosuke Taniai et al., Dalton Trans., 2023, 52, 8368-8375.

Measuring the Electrical Resistivity of Liquid Iron to 1.4 Mbar.

We determined the electrical resistivity of liquid Fe to 135 GPa and 6680 K using a four-probe method in a diamond-anvil cell combined with two novel techniques: (i) enclosing a molten Fe in a sapphire capsule, and (ii) millisecond time-resolved simultaneous measurements of the resistance, x-ray diffraction, and temperature of instantaneously melted Fe. Our results show the minimal temperature dependence of the resistivity of liquid Fe and its anomalous resistivity decrease around 50 GPa, likely associated with a gradual magnetic transition, both in agreement with previous ab initio calculations.

57Fe Mössbauer spectroscopy and high-pressure structural analysis for the mechanism of pressure-induced unique magnetic behaviour in (cation)[FeIIFeIII(dto)3] (cation = Ph4P and nPrPh3P; dto = 1,2-dithiooxalato).

A mixed-valence iron(II,III) coordination polymer, (Ph4P)[FeIIFeIII(dto)3] (2; Ph4P = tetraphenylphosphonium, dto = 1,2-dithiooxalato), exhibits a thermal hysteresis loop and a low temperature shift of the ferromagnetic phase transition temperature, with increasing pressure. The latter magnetic behaviour can also be observed in a novel compound (nPrPh3P)[FeIIFeIII(dto)3] (3; nPrPh3P = n-propyltriphenylphosphonium). To understand the structural information under pressure, we performed high-pressure powder X-ray diffraction, and the result suggests that there was no structural phase transition for either compound. Considering the 57Fe Mössbauer spectroscopy studies, both 2 and 3 may have a high transition entropy, and this finding is caused by pressure-induced unique magnetic behaviours.

Transcriptional Mechanism of the Mouse ß4-Galactosyltransferase 6 Gene in Mouse Neuroblastoma Cell Line Neuro-2a.

Lactosylceramide (Lac-Cer) constitutes the backbone structure of various gangliosides whose abnormal expression is associated with malignancy of neuroblastoma. The understanding of the regulatory mechanism of Lac-Cer contributes to the development of neuroblastoma therapy. In this study, the transcriptional mechanism of mouse ß4-galactosyltransferase (ß4GalT) 6, which is one of Lac-Cer synthase, was analyzed using mouse neuroblastoma cell line Neuro-2a. The -226 to -13 region relative to the most downstream transcriptional start site was determined to be the promoter region by luciferase assay using the 5'-deletion constructs. The mutation into the activating protein (AP) 4-binding site -110/-101 drastically decreased the promoter activity, indicating that this site is mainly implicated in the transcription. Furthermore, the mutation into the GATA-binding site -210/-201 or another AP4-binding site -202/-193 partially decreased the promoter activity. The study suggests that the mouse ß4GalT6 gene is transcriptionally regulated by AP4 in cooperation with GATA family transcription factor in neuroblastoma.

Suppression of Pressure-Induced Phase Transitions in a Monoclinically Distorted LiNbO3-Type CuNbO3 by Preference for a CuO3 Triangular Coordination Environment.

Pressure-induced phase transitions in a monoclinically distorted LiNbO3-type CuNbO3 with triangularly coordinated Cu and octahedrally coordinated Nb were experimentally and computationally investigated. Phase transitions into GdFeO3-type or NaIO3-type structures generally observed in LiNbO3-type compounds below 30 GPa were not detected in CuNbO3 even at the maximum experimental pressure, 32.4 GPa. Our density functional theory calculations revealed that the phase transition is suppressed by the preference for the CuO3 triangular coordination environment, which reduces the total internal energy. This study clarifies that the change in the coordination environment of given ions can affect the pressure-induced phase transition.

Low-spin ferric iron in primordial bridgmanite crystallized from a deep magma ocean.

The crystallization of the magma ocean resulted in the present layered structure of the Earth's mantle. An open question is the electronic spin state of iron in bridgmanite (the most abundant mineral on Earth) crystallized from a deep magma ocean, which has been neglected in the crystallization history of the entire magma ocean. Here, we performed energy-domain synchrotron Mössbauer spectroscopy measurements on two bridgmanite samples synthesized at different pressures using the same starting material (Mg0.78Fe0.13Al0.11Si0.94O3). The obtained Mössbauer spectra showed no evidence of low-spin ferric iron (Fe3+) from the bridgmanite sample synthesized at relatively low pressure of 25 gigapascals, while that directly synthesized at a higher pressure of 80 gigapascals contained a relatively large amount. This difference ought to derive from the large kinetic barrier of Fe3+ rearranging from pseudo-dodecahedral to octahedral sites with the high-spin to low-spin transition in experiments. Our results indicate a certain amount of low-spin Fe3+ in the lower mantle bridgmanite crystallized from an ancient magma ocean. We therefore conclude that primordial bridgmanite with low-spin Fe3+ dominated the deeper part of an ancient lower mantle, which would contribute to lower mantle heterogeneity preservation and call for modification of the terrestrial mantle thermal evolution scenarios.

Superionicity, disorder, and bandgap closure in dense hydrogen chloride.

Hydrogen bond networks play a crucial role in biomolecules and molecular materials such as ices. How these networks react to pressure directs their properties at extreme conditions. We have studied one of the simplest hydrogen bond formers, hydrogen chloride, from crystallization to metallization, covering a pressure range of more than 2.5 million atmospheres. Following hydrogen bond symmetrization, we identify a previously unknown phase by the appearance of new Raman modes and changes to x-ray diffraction patterns that contradict previous predictions. On further compression, a broad Raman band supersedes the well-defined excitations of phase V, despite retaining a crystalline chlorine substructure. We propose that this mode has its origin in proton (H+) mobility and disorder. Above 100 GPa, the optical bandgap closes linearly with extrapolated metallization at 240(10) GPa. Our findings suggest that proton dynamics can drive changes in these networks even at very high densities.

High-pressure effects on superconducting properties and crystal structure of Bi-based layered superconductor La2O2Bi3Ag0.6Sn0.4S6.

The effects of pressure on the superconducting properties of a Bi-based layered superconductor La2O2Bi3Ag0.6Sn0.4S6, which possesses a four-layer-type conducting layer, have been studied through the electrical resistance and magnetic susceptibility measurements. The crystal structure under pressure was examined using synchrotron x-ray diffraction at SPring-8. In the low-pressure regime, bulk superconductivity with a transition temperatureTcof ∼4.5 K was induced by pressure, which was achieved by in-plane chemical pressure effect owing to the compression of the tetragonal structure. In the high-pressure regime above 6.4 GPa, a structural symmetry lowering was observed, and superconducting transitions with aTc∼ 8 K were observed. Our results suggest the possible commonality on the factor essential forTcin Bi-based superconductors with two-layer-type and four-layer-type conducting layers.

Equation of State of Liquid Iron under Extreme Conditions.

The density of liquid iron has been determined up to 116 GPa and 4350 K via static compression experiments following an innovative analysis of diffuse scattering from liquid. The longitudinal sound velocity was also obtained to 45 GPa and 2700 K based on inelastic x-ray scattering measurements. Combining these results with previous shock-wave data, we determine a thermal equation of state for liquid iron. It indicates that Earth's outer core exhibits 7.5%-7.6% density deficit, 3.7%-4.4% velocity excess, and an almost identical adiabatic bulk modulus, with respect to liquid iron.

Sequential Spin State Transition and Intermetallic Charge Transfer in PbCoO3.

Spin state transitions and intermetallic charge transfers can essentially change material structural and physical properties while excluding external chemical doping. However, these two effects have rarely been found to occur sequentially in a specific material. In this article, we show the realization of these two phenomena in a perovskite oxide PbCoO3 with a simple ABO3 composition under high pressure. PbCoO3 possesses a peculiar A- and B-site ordered charge distribution Pb2+Pb4+3Co2+2Co3+2O12 with insulating behavior at ambient conditions. The high spin Co2+ gradually changes to low spin with increasing pressure up to about 15 GPa, leading to an anomalous increase of resistance magnitude. Between 15 and 30 GPa, the intermetallic charge transfer occurs between Pb4+ and Co2+ cations. The accumulated charge-transfer effect triggers a metal-insulator transition as well as a first-order structural phase transition toward a Tetra.-I phase at the onset of ∼20 GPa near room temperature. On further compression over 30 GPa, the charge transfer completes, giving rise to another first-order structural transformation toward a Tetra.-II phase and the reentrant electrical insulating behavior.

Colossal barocaloric effects in plastic crystals.

Refrigeration is of vital importance for modern society-for example, for food storage and air conditioning-and 25 to 30 per cent of the world's electricity is consumed for refrigeration1. Current refrigeration technology mostly involves the conventional vapour compression cycle, but the materials used in this technology are of growing environmental concern because of their large global warming potential2. As a promising alternative, refrigeration technologies based on solid-state caloric effects have been attracting attention in recent decades3-5. However, their application is restricted by the limited performance of current caloric materials, owing to small isothermal entropy changes and large driving magnetic fields. Here we report colossal barocaloric effects (CBCEs) (barocaloric effects are cooling effects of pressure-induced phase transitions) in a class of disordered solids called plastic crystals. The obtained entropy changes in a representative plastic crystal, neopentylglycol, are about 389 joules per kilogram per kelvin near room temperature. Pressure-dependent neutron scattering measurements reveal that CBCEs in plastic crystals can be attributed to the combination of extensive molecular orientational disorder, giant compressibility and highly anharmonic lattice dynamics of these materials. Our study establishes the microscopic mechanism of CBCEs in plastic crystals and paves the way to next-generation solid-state refrigeration technologies.

Unexpected Semimetallic BiS2 at High Pressure and High Temperature.

In the past decade, the group V-VI compounds have been widely investigated due to their excellent properties and applications. It is now accepted that diverse stoichiometry can yield new compounds with unanticipated properties, uncovering potentially new physicochemical mechanisms. However, in this group, aside from the conventional A2B3-type, no other energetically stable stoichiometry has been reported yet. Here, we report that Bi2S3 is unstable and decomposes into stoichiometric BiS2 and BiS with different Bi valence states upon compression. Encouragingly, we successfully synthesized the predicted BiS2 phase and thus, confirmed its existence. Our current calculations reveal that the found BiS2 phase is a semimetal, associated with the increased concentration of nonmetallic S. The present results represent the first counterintuitive stable stoichiometry of group V-VI and provide a good example in designing and synthesizing new compounds under compression.

Lepidocrocite-Type Titanate Formation from Isostructural Prestructures under Hydrothermal Reactions: Observation by Synchrotron X-ray Total Scattering Analyses.

The formation of titanium dioxides, such as rutile and anatase, is known to proceed through the formation of a lepidocrocite-type layered structure under hydrothermal conditions, but the nucleation of this intermediate is still not understood well. Here, the nucleation of lepidocrocite-type layered titanates under hydrothermal conditions is observed by tracking the structural changes by in situ time-resolved pair distribution function analyses. We found that titanate clusters or corrugated layered prestructures having <1 nm domains with lepidocrocite-type connectivity were formed even before thermal treatment in alkaline aqueous solution. Upon thermal treatment, a two-dimensional layered structure grew directly from the prestructure, not from the amorphous polymeric hydroxide dissolved in the solution. Thus, we conclude that the formation of the lepidocrocite-like prestructure is the key for forming a layered titanate under hydrothermal conditions.

The Room-Temperature Superionic Conductivity of Silver Iodide Nanoparticles under Pressure.

We performed variable-temperature synchrotron powder X-ray diffraction measurements and impedance spectroscopy under pressure for silver iodide (AgI) nanoparticles with a diameter of 11 nm. The superionic conducting α-phase of AgI nanoparticles was successfully stabilized down to at least 20 °C by applying a pressure of 0.18 GPa, whereas the transition temperature was 147 °C in bulk AgI at ambient pressure. To our knowledge, this is the first example of the α-phase of AgI existing stably at room temperature.

Intrarater reliabilities of shoulder joint horizontal adductor muscle strength measurements using a handheld dynamometer for geriatric and stroke patients.

[Purpose] This study aimed to verify the appropriate number of measurements and the intrarater reliabilities of shoulder joint horizontal adductor muscle strength measurements using a handheld dynamometer (HHD) for geriatric and stroke patients. [Subjects and Methods] The subjects were 40 inpatients, who were divided into two groups: 20 stroke patients in the stroke group (SG), and 20 geriatric patients in the no-stroke group (N-SG). Measurements were performed three times using an HHD with a belt. The reliability was verified using Bland-Altman analysis and the intraclass correlation coefficient (ICC). [Results] ICC (1, 1) was >0.9. A systematic bias was not observed between the first and second measurement values except for the right side in N-SG. A systematic bias between the maximum value obtained during the first and second measurements and third measurement value was observed on the left side in N-SG, and on the non-paralyzed side in SG: the third measurement values were small in both cases. [Conclusion] Intrarater reliabilities were high for shoulder horizontal adductor strength measurements using an HHD with a belt for geriatric and stroke patients. Taking the systematic bias into consideration, these findings suggest that the required number of measurements is two.

[The Effect of Preoperative Oral Rehydration on Hemodynamic Changes during Induction of Anesthesia and Intraoperative Fluid Management].

BACKGROUND: Preoperative oral rehydration solution (ORS) prevents dehydration before surgery. Therefore taking enough ORS possibly reduces the hemodynamic changes during induction of anesthesia, and reduces the amount of fluid needed during anesthesia. METHODS: Forty patients undergoing elective surgery were randomly assigned to two groups: drinking 1,500 ml ORS 6 to 2 hours before anesthesia (ORS group) and nothing by mouth from 6 hours before anesthesia (Control group). Anesthesia induction was performed using propofol and remifentanil. To evaluate the hemodynamic changes, hemodynamic parameters including heart rate, blood pressure, cardiac index (CI), and stroke volume variation (SVV) were recorded before induction, after propofol administration, and after remifentanil administration. Total urine volume and the amount of fluid were also recorded at the end of the anesthesia. RESULTS: In ORS group, CI showed a significantly higher value after propofol administration (P = 0.046). SVV was significantly lower (P < 0.0001) and total amount of fluid during anesthesia was significantly reduced (P < 0.0001) in ORS group. CONCLUSIONS: Preoperative oral rehydration increases circulating blood volume, it keeps high CI during induction of anesthesia, and reduces the amount of intraoperative fluid.

Effects of peripheral sensory nerve stimulation plus task-oriented training on upper extremity function in patients with subacute stroke: a pilot randomized crossover trial.

OBJECTIVE: To investigate the feasibility of peripheral sensory nerve stimulation combined with task-oriented training in patients with stroke during inpatient rehabilitation. DESIGN: A pilot randomized crossover trial. SETTING: Two rehabilitation hospitals. SUBJECTS: Twenty-two patients with subacute stroke. INTERVENTIONS: Participants were randomly assigned to two groups and underwent two weeks of training in addition to conventional inpatient rehabilitation. The immediate group underwent peripheral sensory nerve stimulation combined with task-oriented training in the first week, followed by another week with task-oriented training alone. The delayed group underwent the same training in reverse order. MAIN MEASURES: Outcome measures were the level of fatigue and Wolf Motor Function Test. Patients were assessed at baseline, one and two weeks. RESULTS: All participants completed the study with no adverse events. There was no significant difference in level of fatigue between each treatment. From baseline to one week, the immediate group showed larger improvements than the delayed groups in the Wolf Motor Function Test (decrease in mean time (± SD) from 41.9 ± 16.2 seconds to 30.6 ± 11.4 seconds versus from 46.8 ± 19.4 seconds to 42.9 ± 14.7 seconds, respectively) but the difference did not reach significance after Bonferroni correction (P = 0.041). Within-group comparison showed significant improvements in the Wolf Motor Function Test mean time after the peripheral sensory nerve stimulation combined with task-oriented training periods in each group (P < 0.01). CONCLUSION: Peripheral sensory nerve stimulation is feasible in clinical settings and may enhance the effects of task-oriented training in patients with subacute stroke.