Quadrupole partial orders and triple-qq states on the face-centered cubic lattice

We study $\Gamma_3$ quadrupole orders in a face-centered cubic lattice. The $\Gamma_3$ quadrupole moments under cubic symmetry possess a unique cubic invariant in their free energy in the uniform ($q=0$) sector and the triple-q sector for the X points $q=(2\pi,0,0),(0,2\pi,0)$, and $(0,0,2\pi)$. Competition between this cubic anisotropy and anisotropic quadrupole-quadrupole interactions causes a drastic impact on the phase diagram both in the ground state and at finite temperatures. We show details about the model construction and its properties, the phase diagram, and the mechanism of the various triple-$q$ quadrupole orders reported in our preceding letter [J. Phys. Soc. Jpn. 90, 43701 (2021), arXiv:2102.06346]. By using a mean-field approach, we analyze a quadrupole exchange model that consists of a crystalline-electric field scheme with the ground-state $\Gamma_3$ non-Kramers doublet and the excited singlet $\Gamma_1$ state. We find various triple-$q$ orders in the four-sublattice mean-field approximation. A few partial orders of quadrupoles are stabilized in a wide range of parameter space at a higher transition temperature than single-$q$ orders. With lowering the temperature, these partial orders undergo phase transitions into further symmetry broken phases in which nonvanishing quadrupole moments emerge at previously disordered sites. The obtained phases in the mean-field approximation are investigated by a phenomenological Landau theory, which clearly shows that the cubic invariant plays an important role for stabilizing the triple-$q$ states. We also discuss its implications for recent experiments in a few f- and d-electron compounds.Comment: 28 pages, 20 figure

RB1CC1 Together with RB1 and p53 Predicts Long-Term Survival in Japanese Breast Cancer Patients

RB1-inducible coiled-coil 1 (RB1CC1) plays a significant role in the enhancement of the retinoblastoma tumor suppressor (RB1) pathway and is involved in breast cancer development. However, RB1CC1's role in clinical progression of breast cancer has not yet been evaluated, so, as a first step, it is necessary to establish its usefulness as a tool to evaluate breast cancer patients. In this report, we have analyzed the correlation between abnormalities in the RB1CC1 pathway and long-term prognosis, because disease-specific death in later periods (>5 years) of the disease is a serious problem in breast cancer. Breast cancer tissues from a large cohort in Japan were evaluated by conventional immunohistochemical methods for the presence of the molecules involved in the RB1CC1 pathway, including RB1CC1, RB1, p53, and other well-known prognostic markers for breast cancer, such as estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. The correlation between the immunohistochemical results and clinical outcomes of 323 breast cancer patients was analyzed using a Kaplan-Meier log-rank test and a multivariate Cox proportional hazards regression analysis. Absence of nuclear RB1CC1 expression was associated with the worst prognosis (Log-rank test, Chi-Square value = 17.462, p<0.0001). Dysfunction of either one of RB1CC1, RB1, or p53 was associated with the highest risk for cancer-specific death, especially related to survival lasting more than 5 years (multivariate Cox proportional hazard ratio = 3.951, 95% Confidence Interval = 1.566–9.967, p = 0.0036). Our present data demonstrate that the combined evaluation of RB1CC1, RB1 and p53 by conventional immunohistochemical analysis provides an accurate prediction of the long-term prognoses of breast cancer patients, which can be carried out as a routine clinical examination

Improved performance of direct methanol fuel cells with the porous catalyst layer using highly-active nanofiber catalyst

PtRu supported on TiO2-embedded carbon nanofibers (PtRu/TECNF), which was recently reported as a highly-active catalyst for methanol oxidation, was applied to a direct methanol fuel cell (DMFC), and the power generation performance was compared to that using the commercial PtRu/C. Before the comparison, the effect of the catalyst loading on the power density of the DMFC was investigated using PtRu(18 wt%)/TECNF. The DMFC power density showed a maximum at about a 1.5 mg cm−2 PtRu loading that corresponds to about an 80 µm layer thickness. A catalyst layer thicker than this value reduced the power density probably due to the concentration overvoltage. The PtRu content in the PtRu/TECNF was then increased to 30 wt% or more to reduce the layer thickness and to increase the power density. The DMFC performance was compared to that of different anode catalysts at a 1 mg cm−2 PtRu loading. The power density was maximized using the PtRu30 wt%/TECNF, which showed a 173 mW cm−2 at 353 K and had 66 µm layer thick, that was 26% higher than that of commercial PtRu/C. The current–voltage curve of the DMFC with the PtRu/TECNF suggested an improved mass transport overvoltage, but a little improvement in the activation one despite using the catalyst with about a 2 times higher activity compared to that of the commercial PtRu/C. This was attributed to the lower Pt utilization of the nanofiber catalyst layer. Keywords: Direct methanol fuel cell, Catalyst layer structure, PtRu catalyst, TiO2-embedded carbon nanofiber support, Methanol oxidation reaction, Power density, Precious metal loading, Concentration overvoltag

Increased utilization and mass activity of PtRu on reduced graphene oxide by heat treatment of its aerogel followed by composite with nanomaterials

The method to increase PtRu utilization and its catalytic activity of PtRu nanoparticles supported on reduced graphene oxide (RGO) by avoiding its restacking was proposed with the aim of developing an active catalyst for a direct methanol fuel cell. The heat treatment at 200 °C of the GO aerogel (GOA) prepared by freeze drying of GO ice was introduced to weaken the attractive force of the hydrogen bonding between the GO sheets followed by the composite with the nanoparticles, i.e., ketjenblack (KB), TiO2 and Ti4O7, at different weight ratios. The catalyst supported on the heat-treated GOA (RGOA), PtRu/RGOA, improved the PtRu utilization to some extent and also increased the ECSA and mass activity compared to that of PtRu/RGO. RGOA had fewer oxygen functional groups, especially the epoxy groups. Due to the treatment and composite, the PtRu utilization was increased from 66.5% for PtRu/RGO to 128.6 % for PtRu/RGOA + Ti4O7 (4:1) and the mass activity was improved from 50.7 A/g-PtRu for PtRu/RGO to 130.5 A/g-PtRu for PtRu/RGOA + Ti4O7 (1:1). The Ti4O7 nanoparticles showed the best catalytic performance for the composite suggesting that the strong interaction between Ti4O7 and the Pt nanoparticles was effective due to its high electronic conductivity

Activity Enhancement of a Carbon Electrode Material for Vanadium Redox Flow Battery by Electron-Beam Irradiation

The effective addition of surface oxygen groups, which are active sites for redox reactions, on carbon clothes as electrodes by electron beam irradiation in normal air which contains environmental humidity, dry air, or nitrogen atmosphere was carried out. The irradiation introduced 20 at% oxygen at the carbon surface as determined by X-ray photoelectron spectroscopy and the phenol-type hydroxyl group, the carboxylic group, etc., were detected by temperature-programmed desorption. Single-cell measurements indicated the current density at 1.3 V-IR-corrected of the irradiated electrode in normal air was 28% higher than that of the as-received electrode. Since double-layer capacitance between the as-received carbon cloth and irradiated carbon cloth in normal air was similar, the improvement of current density is attributed to the increase of surface oxygen groups. In addition, the radiation in both normal air and dry air improved electrochemical activity similarly. This result suggests the radiation-chemical reaction in this study is dominated by the oxidation reaction with ozone or nitrogen oxides (NOx), while in the meantime, the contribution of the hydroxyl radical from water is considered to be negligible

Highly Active Electrode With Efficiently Added Surface Oxygen Groups for a Vanadium Redox Flow Battery

バナジウムレドックスフロー電池は、太陽光や風力などの時間変動の大きい再生可能エネルギーを利用するための電力貯蔵システムとして注目されている。しかし、電池内部抵抗（反応抵抗）が比較的大きく、反応抵抗低減による電流密度の向上が求められている。本研究では、電極材のカーボンクロスに対して、反応活性点となる酸素官能基を付与する目的に大気中熱処理を行い、電池内部抵抗の低減を目指した。実験では、熱処理温度（500℃－550℃）及び処理時間（1-6 h）をパラメータにカーボンクロスの熱処理を行った。さらに、Nafionを隔膜とする単セルに組み込み、電流-電圧測定及びオーム抵抗の測定により電池性能を評価した。その結果、550℃, 3hで熱処理した試料で最も高い発電性能が得られた。この結果から熱処理による反応面積増加及び反応活性点となる親水性の酸素官能基の付与が発電性能向上に有効であることが示された