Cation Dimerization in a 3d1 Honeycomb Lattice System.

In one-dimensional systems with partially filled valence bands, simultaneous changes occur in the electronic states and crystal structures. This is known as the Peierls transition. The Peierls transition (cation dimerization) in VO2, which has a quasi-one-dimensional structure, is well-known, and its mechanism has been extensively discussed. Honeycomb lattices exhibit the Peierls instability owing to their low dimensionality. However, cation dimerization is rare in the 3d1 honeycomb lattice system. Here, we perform an in-depth examination of the V-V dimerization (formation of V-V direct bond) in ilmenite-type MgVO3, which is a 3d1 honeycomb lattice system. A ladderlike pattern was observed in the V-V dimers through synchrotron X-ray experiments at temperatures below 500 K. This dimerization was accompanied by a magnetic-to-nonmagnetic transition. Moreover, a valence bond liquid phase may exist at 500-600 K. Our results reveal the behavior of the valence electrons in the 3d1 honeycomb lattice system.

V-V Dimerization and Magnetic State of Cobalt Ions in Ilmenite-Type CoVO3.

The nature of chemical bonds determines the electronic and magnetic properties of compounds. A metal-metal bonding (V-V dimer) and its effect on the magnetism of ilmenite-type CoVO3 were studied. Polycrystalline CoVO3 samples were synthesized using a high-pressure synthesis method. Crystal structure refinement revealed that V-V dimers exist at temperatures below 550 K in the vanadium layers. Co2+ in CoVO3 exhibits an S = 3/2 state, whereas a Jeff = 1/2 state was reported in ilmenite-type CoTiO3. The existence of V-V dimers reduces the structural symmetry (from R3 to P1), which can change the magnetic ground state.

Metamagnetic Behavior in a Quadruple Perovskite Oxide.

A cubic quadruple perovskite oxide CeMn3Cr4O12 has been synthesized under high-pressure and high-temperature conditions of 8 GPa and 1273 K. The X-ray absorption spectroscopy reveals that the Ce ions are in a trivalent state, as represented by the ionic model of Ce3+Mn3+3Cr3+4O12. The magnetic study demonstrates three independent antiferromagnetic transitions attributed to Ce (∼10 K), Mn (46 K), and Cr (133 K) ions. Furthermore, a magnetic field-induced antiferromagnetic-to-ferromagnetic (metamagnetic) transition of Ce3+ 4f moments is observed at low temperatures below 20 K, exhibiting a rare example of metamagnetism in the Ce3+-oxides. This finding represents that the 3d-electron magnetic sublattices play a role in the metamagnetism of 4f-electron magnetic moments, demonstrating a new aspect of the 3d-4f complex electron systems.

Direct Observation of Magnetization Reversal by Electric Field at Room Temperature in Co-Substituted Bismuth Ferrite Thin Film.

Using the electric field to manipulate the magnetization of materials is a potential way of making low-power-consumption nonvolatile magnetic memory devices. Despite concentrated effort in the last 15 years on magnetic multilayers and magnetoelectric multiferroic thin films, there has been no report on the reversal of out-of-plane magnetization by an electric field at room temperature without the aid of an electric current. Here, we report direct observation of out-of-plane magnetization reversal at room temperature by magnetic force microscopy after electric polarization switching of cobalt-substituted bismuth ferrite thin film grown on (110)o-oriented GdScO3 substrate. A striped pattern of ferroelectric and weakly ferromagnetic domains was preserved after reversal of the out-of-plane electric polarization.

Stability of Polar Structure in Filling-Controlled Giant Tetragonal Perovskite Oxide PbVO3.

The crystal structure and stability of a giant tetragonal phase in electron-doped Pb1- xBi xVO3 ( x = 0.1, 0.2, and 0.3) and hole-doped Pb1- xNa xVO3 ( x = 0.1, 0.2, and 0.3) were studied. Electron doping effectively destabilized the tetragonal structure. The c/ a ratio, spontaneous polarization, and tetragonal-to-cubic phase transition pressure systematically decreased with increasing Bi3+ substitution. In contrast, hole doping hardly affected the tetragonal distortion and structural stability. We showed that electron doping is an effective way to control the stability of the tetragonal phase of PbVO3 with a 3d1 electronic configuration.

Robust Giant Tetragonal Distortion Coupled with High-Spin Co3+ in Electron-Doped BiCoO3.

BiCoO3 is a PbTiO3 type of perovskite oxide with a giant tetragonal distortion (c/a = 1.27) that shows a pressure-induced transition from tetragonal to orthorhombic phases accompanied by a large volume shrinkage at 3 GPa. In this study, we carried out electron doping of BiCoO3 by substituting Ti4+ for Co3+ in order to destabilize the tetragonal phase and observe a giant negative thermal expansion (NTE) at ambient pressure. BiCo1-xTixO3 (x = 0, 0.1, 0.2, and 0.25) was successfully obtained by using high-pressure synthesis. However, the c/a ratio of the tetragonal phase was almost constant against x (≤0.2), and NTE was not observed at any x, suggesting that the tetragonal distortion coupled with high-spin Co3+ is robust against electron doping. In x = 0.25, a metastable orthorhombic phase was obtained by the high-pressure synthetic process, while it partially transformed into a tetragonal phase after annealing at 600 K. The stability of the giant tetragonal phase is strongly connected with the spin state of Co3+.

Colossal Negative Thermal Expansion in Electron-Doped PbVO3 Perovskites.

Colossal negative thermal expansion (NTE) with a volume contraction of about 8 %, the largest value reported so far for NTE materials, was observed in an electron-doped giant tetragonal perovskite compound Pb1-x Bix VO3 (x=0.2 and 0.3). A polar tetragonal (P4mm) to non-polar cubic structural transition took place upon heating. The coefficient of thermal expansion (CTE) and the working temperature could be tuned by changing the Bi content, and La substitution decreased the transition temperature to room temperature. Pb0.76 La0.04 Bi0.20 VO3 exhibited a unit cell volume contraction of 6.7 % from 200 K to 420 K. Interestingly, further gigantic NTE of about 8.5 % was observed in a dilametric measurement of a Pb0.76 La0.04 Bi0.20 VO3 polycrystalline sample. The pronounced NTE in the sintered body should be attributed to an anisotropic lattice parameter change.

Colossal Volume Contraction in Strong Polar Perovskites of Pb(Ti,V)O3.

The unique physical property of negative thermal expansion (NTE) is not only interesting for scientific research but also important for practical applications. Chemical modification generally tends to weaken NTE. It remains a challenge to obtain enhanced NTE from currently available materials. Herein, we successfully achieve enhanced NTE in Pb(Ti1-xVx)O3 by improving its ferroelectricity. With the chemical substitution of vanadium, lattice tetragonality (c/a) is highly promoted, which is attributed to strong spontaneous polarization, evidenced by the enhanced covalent interaction in the V/Ti-O and Pb-O2 bonds from first-principles calculations. As a consequence, Pb(Ti0.9V0.1)O3 exhibits a nonlinear and much stronger NTE over a wide temperature range with a volumetric coefficient of thermal expansion αV = -3.76 × 10-5/°C (25-550 °C). Interestingly, an intrinsic giant volume contraction (∼3.7%) was obtained at the composition of Pb(Ti0.7V0.3)O3 during the ferroelectric-to-paraelectric phase transition, which represents the highest value ever reported. Such volume contraction is well correlated to the effect of spontaneous volume ferroelectrostriction. The present study extends the scope of the NTE family and provides an effective approach to explore new materials with large NTE, such as through adjusting the NTE-related ferroelectric property in the family of ferroelectrics.

A-Site and B-Site Charge Orderings in an s-d Level Controlled Perovskite Oxide PbCoO3.

Perovskite PbCoO3 synthesized at 12 GPa was found to have an unusual charge distribution of Pb2+Pb4+3Co2+2Co3+2O12 with charge orderings in both the A and B sites of perovskite ABO3. Comprehensive studies using density functional theory (DFT) calculation, electron diffraction (ED), synchrotron X-ray diffraction (SXRD), neutron powder diffraction (NPD), hard X-ray photoemission spectroscopy (HAXPES), soft X-ray absorption spectroscopy (XAS), and measurements of specific heat as well as magnetic and electrical properties provide evidence of lead ion and cobalt ion charge ordering leading to Pb2+Pb4+3Co2+2Co3+2O12 quadruple perovskite structure. It is shown that the average valence distribution of Pb3.5+Co2.5+O3 between Pb3+Cr3+O3 and Pb4+Ni2+O3 can be stabilized by tuning the energy levels of Pb 6s and transition metal 3d orbitals.

Electric-Field-Induced Reorientation of the Magnetic Easy Plane in a Co-Substituted BiFeO3 Single Crystal.

Single crystals of BiFe0.9Co0.1O3 and BiFe0.892Mn0.008Co0.1O3, room temperature ferroelectric ferromagnets, were successfully grown by a flux method at a high pressure of 3 GPa. Remanent magnetization measurements along 18 crystallographic directions revealed the existence of a magnetic easy plane perpendicular to the electric polarization. Reorientation of the magnetic easy plane occurred in connection with 71° ferroelectric switching by applying an electric field. This is the first demonstration of an electric field affecting the local magnetic moment of Co-substituted BiFeO3.

High-Temperature Monoclinic Cc Phase with Reduced c/a Ratio in Bi-based Perovskite Compound Bi2ZnTi1-xMnxO6.

Monoclinic phases with Cm, Pm, and Cc space groups are indispensable to understand the high performance of electromechanical properties at the morphotropic phase boundary (MPB) of lead-based perovskite oxides Pb(ZrxTi1-x)O3 (PZT), [Pb(Mg1/3Nb2/3)O3]1-x-(PbTiO3)x (PMN-PT), and [Pb(Zn1/3Nb2/3)O3]1-x-(PbTiO3)x (PZN-PT). Here, a nearly single monoclinic phase with space group Cc was observed in the Bi-based lead-free perovskite compound Bi2ZnTi1-xMnxO6 at x = 0.4. This phase was the same as the low-temperature phase of the MPB composition of PZT but existed at a much higher temperature. Despite the reduced pseudo c/a ratio of 1.065, which is the same as that of PbTiO3 at room temperature, ionic model calculation based on the Rietveld refinement data indicated the polarization of Bi2ZnTi0.6Mn0.4O6 is 95.8 µC/cm(2). The tilting and significant anisotropic distortion of the octahedron were found to cause the c/a ratio to reduce. Accordingly, the effective piezoelectric constant d33 of Bi2ZnTi0.6Mn0.4O6 thin film was found to be 12 pm/V.

Giant Polarization and High Temperature Monoclinic Phase in a Lead-Free Perovskite of Bi(Zn0.5Ti0.5)O3-BiFeO3.

Lead-free piezoelectrics have attracted increasing attention because of the awareness of lead toxicity to the environment. Here, a new bismuth-based lead-free perovskite, (1 - x)Bi(Zn0.5Ti0.5)O3-xBiFeO3, has been synthesized via a high-pressure and high-temperature method. It exhibits interesting properties of giant polarization, morphotropic phase boundary (MPB), and monoclinic phase. In particular, large tetragonality (c/a = 1.228) and giant spontaneous polarization of 110 µC/cm2 has been obtained in 0.6 Bi(Zn0.5Ti0.5)O3-0.4BiFeO3, which is much higher than most available lead-free materials and conventional Pb(Zr,Ti)O3. MPB is clearly identified to be constituted of tetragonal and monoclinic phases at x = 0.5. Notably, a single monoclinic phase has been observed at x = 0.6, which exhibits an intriguing high-temperature property. The present results are helpful to explore new lead-free MPB systems in bismuth-based compounds.

Radiotherapy for patients with unresectable advanced hepatocellular carcinoma with invasion to intrahepatic large vessels: efficacy and outcomes.

BACKGROUND AND AIM: To examine the efficacy and outcomes of radiotherapy (RT) in patients who have hepatocellular carcinoma with invasion to intrahepatic large vessels (IHLVs). METHODS: Sixty-seven patients who had advanced hepatocellular carcinoma with invasion to IHLVs received three-dimensional conformal RT. IHLV invasion was associated with portal venous tumor thrombosis in 40 patients, tumor thrombosis involving the hepatic vein in 17, and both findings in 10. A daily radiation dose of 1.8-2 Gy was administered using 6 or 10 MV X-rays to deliver a total dose of 30-56 Gy. RESULTS: The overall objective response rate (complete response plus partial response) was 45% (n = 30). The median survival time was 13.7 months in the responder group and 5.9 months in the nonresponder group. An objective response was observed in 28 (56%) of 50 patients with Child-Pugh (C-P) class A and in 2 (12%) of 17 patients with C-P class B. Hepatic function of C-P class A was an independent factor for both RT responder and overall survival on Cox regression analysis (hazard ratio = 9.5, 95% confidence interval = 1.97-46.2, P = 0.005; and hazard ratio = 0.39, 95% confidence interval = 0.2-0.77, P = 0.007, respectively). CONCLUSION: RT is an effective treatment option without serious adverse events. RT should be considered for the patients with better hepatic function who have invasion to IHLVs.

ZnVO3: an ilmenite-type vanadium oxide hosting robust V-V dimers.

Ilmenite-type vanadium oxides exhibit a distinctive cation-dimerization behavior. Here, we report a novel ilmenite-type compound, ZnVO3. Polycrystalline ZnVO3 samples are synthesized under conditions of 10 GPa and 1573 K. The obtained sample crystallizes in the triclinic P1̄ space group. Both V-V and Zn-Zn dimers (dimer-like displacement) are present in the structure, arranged in a ladder-like pattern on each honeycomb lattice. Notably, the V-V dimer persists up to 625 K, surpassing the stability of the V-V dimer state in other ilmenite-type vanadium oxides. Magnetic susceptibility measurements corroborate the formation of direct V-V bond in the dimer. The off-centered position of the Zn2+ ion at the octahedral site, driven by Zn-O covalency and its sp3 nature, promotes the Zn-Zn dimer-like displacement. Cooperative distortions between honeycomb layers further reinforce the V-V dimers. This finding offers insights into controlling cation-dimer strength in crystalline compounds via crystal structure distortions.

Protocol for viral vector-mediated measurement of transcription factor activity of mouse brain.

Here, we provide a step-by-step protocol to measure the activities of multiple transcription factors (TFs) in the same mouse brain. This protocol includes a procedure to construct a virus-based TF activity reporter, in utero transfection, and PCR-based measurement of TF activity to obtain the transcription factor activity profile (TFAP). Our protocol facilitates a systematic analysis of TF activity of the brain in vivo and will aid trans-omics understanding of the molecular mechanism underlying the brain functions. For complete details on the use and execution of this protocol, please refer to Abe and Abe, (2022).

Polarization Rotation at Morphotropic Phase Boundary in New Lead-Free Na1/2Bi1/2V1-xTixO3 Piezoceramics.

In this work, we show that polarization rotation enhances the piezoresponse in a high-performance lead-free piezoelectric material, Na1/2Bi1/2V1-xTixO3, a solid solution between tetragonal Na1/2Bi1/2VO3 and rhombohedral Na1/2Bi1/2TiO3, obtained by high-pressure synthesis. The system forms a pure perovskite structure with a favorable morphotropic phase boundary (MPB) located around x = 0.90, which separates the tetragonal and rhombohedral phases. In addition, a distinct monoclinic phase with polarization rotation as functions of composition and temperature is observed. XRD measurements revealed the moderately high Curie temperature of 523 K at x = 0.95 in the MPB. The piezoelectric coefficient d33 of the monoclinic x = 0.95 sample, 42 pC/N, is higher than those of the tetragonal and rhombohedral phases. Even though the present lead-free Na1/2Bi1/2V1-xTixO3 ceramics feature smaller d33 values compared to many currently available lead-free piezoelectric materials as a result of insufficient poling and low density, we expect our findings open up opportunities for exploring promising lead-free piezoelectric materials in Na1/2Bi1/2VO3-based perovskites.

Metallurgical Characterization of Penetration Shape Change in Workpiece Vibration-Assisted Tandem-Pulsed Gas Metal Arc Welding.

Tandem-pulsed gas metal arc welding (TP-GMAW) simultaneously uses two wire-electrodes to enhance the material deposition rate, leading to the generation of a finger-shaped penetration as one of the arcs penetrates deeper than the other. On the other hand, workpiece vibration is one of the techniques used to control the microstructure of weld metal and a heat-affected zone. It is incidentally found that a specific vibration condition changes the finger-shaped penetration into pan-bottom shaped penetration in the TP-GMAW even though the vibration energy is much lower than the arc energy. Microstructure observation and elemental analysis are carried out for the welds fabricated without vibration and with three kinds of vibration modes, namely sine, random, and shock. The specific sine-mode vibration exhibits pan-bottom. The other modes of vibration in the same welding conditions exhibited invariable finger-shaped penetration. The Si atoms as a tracer distribute uniformly in the sine-mode. However, Si atoms segregate at the bottom of the finger-shaped weld metal with the random-mode and shock-mode workpiece vibrations. The weld pool shape change is prominent at a specific frequency. A resonance phenomenon between the droplet flow pattern and the molten material flow in the weld pool is likely to play a vital role in the change.

Plant Enzymes Decrease Prostate Cancer Cell Numbers and Increase TNF-α In Vivo: A Possible Role in Immunostimulatory Activity.

Increased caloric intake and Westernized dietary choices may be contributing toward a recent rising trend of incidences of chronic lifestyle-related diseases. In this study, we evaluated the anticancer properties of Plant Enzyme Validux (PEV) using a mouse model. Five-week-old male C3H mice were randomly distributed into four experimental groups: Control, PEV only, 6Gy irradiation only, and PEV + 6Gy. PEV was orally administered daily at 500 mg/kg for 14 days prior to three rounds of 2Gy irradiation. We focused on the anticancer action and immunostimulatory effects of PEV with and without irradiation. Oncogene suppression was observed after PEV treatment as was an increase in TNF-α, suggesting an antitumor effect. PEV administration also appeared to reduce oxidative stress as evidenced by a decrease in lipid peroxidation. In addition, PEV confirmed radioprotective effect by radical blocking ability by radiation irradiation. Immunological responses to PEV administration were evidenced by an increase in number of total white blood cells and T lymphocytes. Immunotherapy is drawing more and more attention as a treatment for prostate cancer, suggesting that there will be a need for the identification of specific targets for prostate cancer and for more basic research on the genetic aspects of immunotherapy. Thus, PEV may be of use as a radioprotective supplement during radiotherapy for tumor treatment.

Large Negative Thermal Expansion Induced by Synergistic Effects of Ferroelectrostriction and Spin Crossover in PbTiO3-Based Perovskites.

The discovery of unusual negative thermal expansion (NTE) provides the opportunity to control the common but much desired property of thermal expansion, which is valuable not only in scientific interests but also in practical applications. However, most of the available NTE materials are limited to a narrow temperature range, and the NTE effect is generally weakened by various modifications. Here, we report an enhanced NTE effect that occurs over a wide temperature range α‾V=-5.24×10-5∘C-1,25-575∘C, and this NTE effect is accompanied by an abnormal enhanced tetragonality, a large spontaneous polarization, and a G-type antiferromagnetic ordering in the present perovskite-type ferroelectric of (1-x)PbTiO3-xBiCoO3. Specifically, for the composition of 0.5PbTiO3-0.5BiCoO3, an extensive volumetric contraction of ~4.8 % has been observed near the Curie temperature of 700 °C, which represents the highest level in PbTiO3-based ferroelectrics. According to our experimental and theoretical results, the large NTE originates from a synergistic effect of the ferroelectrostriction and spin crossover of cobalt on the crystal lattice. The actual NTE mechanism is contrasted with previous functional NTE materials, in which the NTE is simply coupled with one ordering such as electronic, magnetic, or ferroelectric ordering. The present study sheds light on the understanding of NTE mechanisms, and it attests that NTE could be simultaneously coupled with different orderings, which will pave a new way toward the design of large NTE materials.

Development of Bismuth Ferrite as a Piezoelectric and Multiferroic Material by Cobalt Substitution.

Bismuth ferrite (BiFeO3 ) is the most widely studied multiferroic material with robust ferroelectricity and antiferromagnetic ordering at room temperature. One of the possible device applications of this material is one that utilizes the ferroelectric/piezoelectric property itself such as ferroelectric memory components, actuators, and so on. Other applications are more challenging and make full use of its multiferroic property to realize novel spintronics and magnetic memory devices, which can be addressed electrically as well as magnetically. This progress report summarizes the recent attempt to control the piezoelectric and magnetic properties of BiFeO3 by cobalt substitution.