Quasi-2D Fermi surface in the anomalous superconductor UTe2.

The heavy fermion paramagnet UTe2 exhibits numerous characteristics of spin-triplet superconductivity. Efforts to understand the microscopic details of this exotic superconductivity have been impeded by uncertainty regarding the underlying electronic structure. Here we directly probe the Fermi surface of UTe2 by measuring magnetic quantum oscillations in pristine quality crystals. We find an angular profile of quantum oscillatory frequency and amplitude that is characteristic of a quasi-2D Fermi surface, which we find is well described by two cylindrical Fermi sheets of electron- and hole-type respectively. Additionally, we find that both cylindrical Fermi sheets possess considerable undulation but negligible small-scale corrugation, which may allow for their near-nesting and therefore promote magnetic fluctuations that enhance the triplet pairing mechanism. Importantly, we find no evidence for the presence of any 3D Fermi surface sections. Our results place strong constraints on the possible symmetry of the superconducting order parameter in UTe2.

Longitudinal Spin Fluctuations Driving Field-Reinforced Superconductivity in UTe_{2}.

Our measurements of ^{125}Te NMR relaxations reveal an enhancement of electronic spin fluctuations above µ_{0}H^{*}∼15 T, leading to their divergence in the vicinity of the metamagnetic transition at µ_{0}H_{m}≈35 T, below which field-reinforced superconductivity appears when a magnetic field (H) is applied along the crystallographic b axis. The NMR data evidence that these fluctuations are dominantly longitudinal, providing a key to understanding the peculiar superconducting phase diagram in H∥b, where such fluctuations enhance the pairing interactions.

Field Induced Multiple Superconducting Phases in UTe_{2} along Hard Magnetic Axis.

The superconducting (SC) phase diagram in uranium ditelluride is explored under magnetic fields (H) along the hard magnetic b axis using a high-quality single crystal with T_{c}=2.1 K. Simultaneous electrical resistivity and ac magnetic susceptibility measurements discern low- and high-field SC (LFSC and HFSC, respectively) phases with contrasting field-angular dependence. Crystal quality increases the upper critical field of the LFSC phase, but the H^{*} of ∼15 T, at which the HFSC phase appears, is always the same through the various crystals. A phase boundary signature is also observed inside the LFSC phase near H^{*}, indicating an intermediate SC phase characterized by small flux pinning forces.

Multipole polaron in the devil's staircase of CeSb.

Rare-earth intermetallic compounds exhibit rich phenomena induced by the interplay between localized f orbitals and conduction electrons. However, since the energy scale of the crystal-electric-field splitting is only a few millielectronvolts, the nature of the mobile electrons accompanied by collective crystal-electric-field excitations has not been unveiled. Here, we examine the low-energy electronic structures of CeSb through the anomalous magnetostructural transitions below the Néel temperature, ~17 K, termed the 'devil's staircase', using laser angle-resolved photoemission, Raman and neutron scattering spectroscopies. We report another type of electron-boson coupling between mobile electrons and quadrupole crystal-electric-field excitations of the 4f orbitals, which renormalizes the Sb 5p band prominently, yielding a kink at a very low energy (~7 meV). This coupling strength is strong and exhibits anomalous step-like enhancement during the devil's staircase transition, unveiling a new type of quasiparticle, named the 'multipole polaron', comprising a mobile electron dressed with a cloud of the quadrupole crystal-electric-field polarization.

Effect of uranium deficiency on normal and superconducting properties in unconventional superconductor UTe2.

Single crystals of the unconventional superconductor UTe2have been grown in various conditions which result in different superconducting transition temperature as well as normal state properties. Stoichiometry of the samples has been characterized by the single-crystal x-ray crystallography and electron microprobe analyses. Superconducting samples are nearly stoichiometric within an experimental error of about 1%, while non-superconducting sample significantly deviates from the ideal composition. The superconducting UTe2showed that the large density of states was partially gapped in the normal state, while the non-superconducting sample is characterized by the relatively large electronic specific heat as reported previously.

Alpha-crystallin B chains enhance cell migration in basal-like 2 triple-negative breast cancer cells.

Triple-negative breast cancer (TNBC) can be divided into six subtypes. Among these subtypes, the basal-like 2 (BL2) subtype shows the lowest five-year survival rate and highest risk of metastasis. Alpha-crystallin B chains (αB-crystallin), a small heat shock protein that is known to be involved in breast cancer metastasis, is highly expressed in the basal-like subtype but not in the other non-basal subtypes. Thus, we hypothesized that αB-crystallin may be an important factor involved in the worse prognosis of the BL2 subtype compared with those of the other TNBC subtypes. Here, we examined the role of αB-crystallin in cell motility in two TNBC cell lines: HCC1806 (BL2 subtype) and, as control, MDA-MB-436 (mesenchymal stem-like subtype). HCC1806 showed greater cell migration capacity and a higher expression level of the gene encoding αB-crystallin (CRYAB) than did MDA-MB-436. Short interfering RNA-mediated silencing of CRYAB expression significantly reduced the cell migration capacity of HCC1806 cells, whereas it had no effect in MDA-MB-436 cells, indicating that αB-crystallin is essential for the migration of HCC1806 cells. Thus, high αB-crystallin expression may be a contributing factor to the poor prognosis of BL2 TNBC.

Progesterone receptor membrane component 2 expression leads to erlotinib resistance in lung adenocarcinoma cells.

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) provide a favorable treatment outcome in patients with EGFR mutation-positive non-small cell lung cancer. However, most of such patients become resistant to EGFR-TKIs within a year. Thus, clarifying the mechanism of acquired resistance to EGFR-TKIs has been a research focus. Here, we demonstrated that the expression of progesterone receptor membrane component 2 (PGRMC2) was upregulated in an erlotinib-resistant cell line, PC9/ER, compared with the parental PC9 lung cancer cells. Our previous study showed that PGRMC1 is responsible for acquired resistance to erlotinib; however, PGRMC2 has not been discussed yet. Thus, the aim of this study was to determine the role of PGRMC2 in acquired resistance to erlotinib. Transfection with PGRMC2 siRNA significantly enhanced the sensitivity to erlotinib in PC9/ER cells. Furthermore, knockdown of PGRMC2 reduced the expression of p21, which is known as cell-cycle inhibitor and antiproliferative effector. These results suggest that PGRMC2 partially contributes to erlotinib resistance in PC9/ER cells, and that investigation into the effect of PGRMC2 on apoptosis and the cell cycle are warranted.

Devil's staircase transition of the electronic structures in CeSb.

Solids with competing interactions often undergo complex phase transitions with a variety of long-periodic modulations. Among such transition, devil's staircase is the most complex phenomenon, and for it, CeSb is the most famous material, where a number of the distinct phases with long-periodic magnetostructures sequentially appear below the Néel temperature. An evolution of the low-energy electronic structure going through the devil's staircase is of special interest, which has, however, been elusive so far despite 40 years of intense research. Here, we use bulk-sensitive angle-resolved photoemission spectroscopy and reveal the devil's staircase transition of the electronic structures. The magnetic reconstruction dramatically alters the band dispersions at each transition. Moreover, we find that the well-defined band picture largely collapses around the Fermi energy under the long-periodic modulation of the transitional phase, while it recovers at the transition into the lowest-temperature ground state. Our data provide the first direct evidence for a significant reorganization of the electronic structures and spectral functions occurring during the devil's staircase.

A PHANTOM STUDY TO DETERMINE THE OPTIMAL PLACEMENT OF EYE DOSEMETERS ON INTERVENTIONAL CARDIOLOGY STAFF.

The International Commission on Radiological Protection has substantially reduced the recommended maximum annual eye lens dose for workers. Use of a dedicated eye dosemeter is one method for accurate dose monitoring. The main aim of this study was to yield recommendations for optimal placement of eye dosemeters to estimate the eye dose to interventional cardiology physicians and nurses. A phantom measurement was conducted to simulate typical interventional cardiology procedures. Considering eight X-ray tube angulations, the left side of the head position provide good estimates for physician, and the forehead position provide good estimates for nurse.

Experimental Determination of the Topological Phase Diagram in Cerium Monopnictides.

Experimental determinations of bulk band topology in the solid states have been so far restricted to only indirect investigation through the probing of surface states predicted by electronic structure calculations. We here present an alternative approach to determine the band topology by means of bulk-sensitive soft x-ray angle-resolved photoemission spectroscopy. We investigate the bulk electronic structures of the series materials, Ce monopnictides (CeP, CeAs, CeSb, and CeBi). By performing a paradigmatic study of the band structures as a function of their spin-orbit coupling, we draw the topological phase diagram and unambiguously reveal the topological phase transition from a trivial to a nontrivial regime in going from CeP to CeBi induced by the band inversion. The underlying mechanism of the phase transition is elucidated in terms of spin-orbit coupling in concert with their semimetallic band structures. Our comprehensive observations provide a new insight into the band topology hidden in the bulk states.

Evidence for Spin Singlet Pairing with Strong Uniaxial Anisotropy in URu_{2}Si_{2} Using Nuclear Magnetic Resonance.

In order to identify the spin contribution to superconducting pairing compatible with the so-called "hidden order", ^{29}Si nuclear magnetic resonance measurements have been performed using a high-quality single crystal of URu_{2}Si_{2}. A clear reduction of the ^{29}Si Knight shift in the superconducting state has been observed under a magnetic field applied along the crystalline c axis, corresponding to the magnetic easy axis. These results provide direct evidence for the formation of spin-singlet Cooper pairs. Consequently, results indicating a very tiny change of the in-plane Knight shift reported previously demonstrate extreme uniaxial anisotropy for the spin susceptibility in the hidden order state.

Search for Nucleon and Dinucleon Decays with an Invisible Particle and a Charged Lepton in the Final State at the Super-Kamiokande Experiment.

Search results for nucleon decays p→e^{+}X, p→µ^{+}X, n→νγ (where X is an invisible, massless particle) as well as dinucleon decays np→e^{+}ν, np→µ^{+}ν, and np→τ^{+}ν in the Super-Kamiokande experiment are presented. Using single-ring data from an exposure of 273.4 kton·yr, a search for these decays yields a result consistent with no signal. Accordingly, lower limits on the partial lifetimes of τ_{p→e^{+}X}>7.9×10^{32} yr, τ_{p→µ^{+}X}>4.1×10^{32} yr, τ_{n→νγ}>5.5×10^{32} yr, τ_{np→e^{+}ν}>2.6×10^{32} yr, τ_{np→µ^{+}ν}>2.2×10^{32} yr, and τ_{np→τ^{+}ν}>2.9×10^{31} yr at a 90% confidence level are obtained. Some of these searches are novel.

Search for neutrinos from annihilation of captured low-mass dark matter particles in the sun by super-kamiokande.

Super-Kamiokande (SK) can search for weakly interacting massive particles (WIMPs) by detecting neutrinos produced from WIMP annihilations occurring inside the Sun. In this analysis, we include neutrino events with interaction vertices in the detector in addition to upward-going muons produced in the surrounding rock. Compared to the previous result, which used the upward-going muons only, the signal acceptances for light (few-GeV/c^{2}-200-GeV/c^{2}) WIMPs are significantly increased. We fit 3903 days of SK data to search for the contribution of neutrinos from WIMP annihilation in the Sun. We found no significant excess over expected atmospheric-neutrino background and the result is interpreted in terms of upper limits on WIMP-nucleon elastic scattering cross sections under different assumptions about the annihilation channel. We set the current best limits on the spin-dependent WIMP-proton cross section for WIMP masses below 200 GeV/c^{2} (at 10 GeV/c^{2}, 1.49×10^{-39} cm^{2} for χχ→bb[over ¯] and 1.31×10^{-40} cm^{2} for χχ→τ^{+}τ^{-} annihilation channels), also ruling out some fraction of WIMP candidates with spin-independent coupling in the few-GeV/c^{2} mass range.

Search for trilepton nucleon decay via p→e+νν and p→µ+νν in the Super-Kamiokande experiment.

The trilepton nucleon decay modes p→e+νν and p→µ+νν violate |Δ(B-L)| by two units. Using data from a 273.4 kt yr exposure of Super-Kamiokande a search for these decays yields a fit consistent with no signal. Accordingly, lower limits on the partial lifetimes of τp→e+νν>1.7×10(32) years and τp→µ+νν>2.2×10(32) years at a 90% confidence level are obtained. These limits can constrain Grand Unified Theories which allow for such processes.

Direct observation of lattice symmetry breaking at the hidden-order transition in URu2Si2.

Since the 1985 discovery of the phase transition at THO=17.5 K in the heavy-fermion metal URu2Si2, neither symmetry change in the crystal structure nor large magnetic moment that can account for the entropy change has been observed, which makes this hidden order enigmatic. Recent high-field experiments have suggested electronic nematicity that breaks fourfold rotational symmetry, but direct evidence has been lacking for its ground state in the absence of magnetic field. Here we report on the observation of lattice symmetry breaking from the fourfold tetragonal to twofold orthorhombic structure by high-resolution synchrotron X-ray diffraction measurements at zero field, which pins down the space symmetry of the order. Small orthorhombic symmetry-breaking distortion sets in at THO with a jump, uncovering the weakly first-order nature of the hidden-order transition. This distortion is observed only in ultrapure samples, implying a highly unusual coupling nature between the electronic nematicity and underlying lattice.

A note on the presence of B chromosome in the small Japanese field mouse, Apodemus argenteus, in Central Honshu, Japan.

Previously, many studies have revealed the presence of B chromosomes in wild mouse taxa of the genus Apodemus (Rodentia, Muridae). In one of the Apodemus species, A. argenteus, which is endemic to Japan, it is known that B chromosomes were confirmed only in individuals (2n = 46 + B chromosome) from Hokkaido, Japan. There is no report of the presence of B chromosomes from other localities in the Japanese Islands. In this study, we analyzed the chromosomal constitutions of 43 individuals of A. argenteus from three localities in Honshu, Japan. A total of three individuals from central Honshu showed 2n = 47, and each individual carrieda dot-like B chromosome. In addition, these B chromosome features were analyzed by differential staining methods, and the C- and QM-banding patterns of the B chromosomes were identical to those of the X chromosomal heterochromatic region showing the delayed-fluorescent response. Thus, it is considered that these B chromosomes would be derived from the heterochromatin of the X chromosomes, as reported in previously published papers.

Measurement of subcutaneous biological substances using thin metal needle with micro flow channel.

Concentrations of biological substances are useful as indicators of physiological and pathological states. In order to monitor biological substances in daily life, we developed a minimally invasive needle type device with which biological substances are extracted through a microperfusion system inserted under the skin. The perfusion needle has a flow channel with perforated membrane through which biological substances from subepidermal tissue are extracted. The efficacy of the device was examined by measuring lactate concentration of exercising mice. Lactate was successfully collected from the back skin of the mice running on a treadmill using a fabricated microperfusion needle. Lactate concentration of perfused solution correlated with blood lactate concentration.

NMR study of in-plane twofold ordering in URu(2)Si(2).

We report (29)Si NMR spectra and Knight shift measurements as a function of applied field orientation in the (001) basal plane of URu(2)Si(2). Observed linewidth oscillations confirm the in-plane twofold ordered domain state observed in recent magnetic susceptibility measurements. Analysis of our linewidth data leads to estimate ∼ 0.4% for the twofold intrinsic (monodomain) susceptibility anisotropy in the basal plane, a value ∼ 15 times smaller than that obtained from recent susceptibility measurements.

Cyclotron resonance in the hidden-order phase of URu2Si2.

We report the first observation of cyclotron resonance in the hidden-order phase of ultraclean URu2Si2 crystals, which allows the full determination of angle-dependent electron-mass structure of the main Fermi-surface sheets. We find an anomalous splitting of the sharpest resonance line under in-plane magnetic-field rotation. This is most naturally explained by the domain formation, which breaks the fourfold rotational symmetry of the underlying tetragonal lattice. The results reveal the emergence of an in-plane mass anisotropy with hot spots along the [110] direction, which can account for the anisotropic in-plane magnetic susceptibility reported recently. This is consistent with the "nematic" Fermi liquid state, in which itinerant electrons have unidirectional correlations.

Twofold spontaneous symmetry breaking in the heavy-fermion superconductor UPt3.

The field-orientation dependent thermal conductivity of the heavy-fermion superconductor UPt3 was measured down to very low temperatures and under magnetic fields throughout the distinct superconducting phases: B and C phases. In the C phase, a striking twofold oscillation of the thermal conductivity within the basal plane is resolved reflecting the superconducting gap structure with a line of node along the a axis. Moreover, we find an abrupt vanishing of the oscillation across a transition to the B phase, as a clear indication of a change of gap symmetries. We also identify extra two line nodes below and above the equator in both B and C phases. From these results together with the symmetry consideration, the gap function of UPt3 is determined as a E(1u) representation characterized by a combination of two line nodes at the tropics and point nodes at the poles.