Enhancement of charge-neutral fermionic excitation near spin-flop transition\\ in magnetic Kondo material YbIr3_3Si7_7

The new Kondo material YbIr$_3$Si$_7$, similar to other Kondo insulators, has been reported to exhibit charge-neutral fermionic excitations through measurements of specific heat and thermal conductivity at low temperatures. We performed $^{29}$Si-NMR on YbIr$_3$Si$_7$ to investigate the magnetic response of charge-neutral fermions from a microscopic perspective. In low magnetic fields parallel to the $c$ axis, a single NMR peak in the paramagnetic state splits into three peaks below $T_{\rm N}$. In contrast, only a slight shift of the single NMR peak was observed in high magnetic fields. This spectral change as a function of the $c$-axis magnetic field is interpreted as spin-flop transition, at which the magnetic moments oriented along the $c$ axis (AF-I phase) are rotated to the $ab$ plane with ferromagnetic component along the $c$-axis (AF-II phase). In the vicinity of the spin-flop magnetic field $H_{\rm M}$, nuclear spin-lattice relaxation rate $1/T_1$ was found to be proportional to temperature at low temperatures, indicating the existence of charge-neutral fermions. Furthermore, a peak of $1/T_1$ vs. the $c$-axis magnetic field suggests that the charge-neutral fermions in YbIr$_3$Si$_7$ are closely related to its magnetic properties. Our findings shed light on the origin of charge-neutral fermions in insulators.Comment: 5 pages, 3 figure

Application of precise neutron focusing mirrors for neutron reflectometry: latest results and future prospects

超精密中性子集束ミラーによる電極界面のナノ構造解析技術の実用化 --測定精度の劇的な向上に向けた大きなマイルストーン--. 京都大学プレスリリース. 2020-10-28.Neutron reflectometry (NR) is a powerful tool for providing insight into the evolution of interfacial structures, for example via operando measurements for electrode–electrolyte interfaces, with a spatial resolution of nanometres. The time resolution of NR, which ranges from seconds to minutes depending on the reflection intensity, unfortunately remains low, particularly for small samples made of state-of-the-art materials even with the latest neutron reflectometers. To overcome this problem, a large-area focusing supermirror manufactured with ultra-precision machining has been employed to enhance the neutron flux at the sample, and a gain of approximately 100% in the neutron flux was achieved. Using this mirror, a reflectivity measurement was performed on a thin cathode film on an SrTiO3 substrate in contact with an electrolyte with a small area of 15 × 15 mm. The reflectivity data obtained with the focusing mirror were consistent with those without the mirror, but the acquisition time was shortened to half that of the original, which is an important milestone for rapid measurements with a limited reciprocal space. Furthermore, a method for further upgrades that will reveal the structural evolution with a wide reciprocal space is proposed, by applying this mirror for multi-incident-angle neutron reflectometry

Associations of HIV testing and late diagnosis at a Japanese university hospital

OBJECTIVES: This study was conducted to clarify the rate of late diagnosis of HIV infection and to identify relationships between the reasons for HIV testing and a late diagnosis. METHODS: This retrospective cohort study was conducted among HIV-positive patients at the Jikei University Hospital between 2001 and 2014. Patient characteristics from medical records, including age, sex, sexuality, the reason for HIV testing and the number of CD4-positive lymphocytes at HIV diagnosis, were assessed. RESULTS: A total of 459 patients (men, n=437; 95.2%) were included in this study and the median age at HIV diagnosis was 36 years (range, 18-71 years). Late (CD4 cell coun

Gapless fermionic excitation in the antiferromagnetic state of ytterbium zigzag chain

Abstract The emergence of charge-neutral fermionic excitations in magnetic systems is one of the unresolved issues in recent condensed matter physics. This type of excitations has been observed in various systems, such as low-dimensional quantum spin liquids, Kondo insulators, and antiferromagnetic insulators. Here, we report the presence of a pronounced gapless spin excitation in the low-temperature antiferromagnetic state of YbCuS2 semiconductor, where trivalent ytterbium atoms form a zigzag chain structure. We confirm the presence of this gapless excitations by a combination of experimental probes, namely 63/65Cu-nuclear magnetic resonance and nuclear quadrupole resonance, as well as specific heat measurements, revealing a linear low-temperature behavior of both the nuclear spin-lattice relaxation rate 1/T 1 and the specific heat. This system provides a platform to investigate the origin of gapless excitations in spin chains and the relationship between emergent fermionic excitations and frustration

Non-thermal plasma induces a stress response in mesothelioma cells resulting in increased endocytosis, lysosome biogenesis and autophagy

Non-thermal plasma (NTP) is a potential new therapeutic modality for cancer. However, its mechanism of action remains unclear. Herein, we studied the effect of NTP on mesothelioma cells and fibroblasts to understand its anti-proliferative efficacy. Interestingly, NTP demonstrated greater selective anti-proliferative activity against mesothelioma cells relative to fibroblasts than cisplatin, which is used for mesothelioma treatment. The anti-proliferative effect of NTP was enhanced by pre-incubation with the cellular iron donor, ferric ammonium citrate (FAC), and inhibited by iron chelation using desferrioxamine (DFO). Three oxidative stress probes (CM-H2DCFDA, MitoSOX and C11-BODIPY) demonstrated reactive oxygen species (ROS) generation by NTP, which was inhibited by DFO. Moreover, NTP decreased transferrin receptor-1 and increased ferritin-H and -L chain expression that was correlated with decreased iron-regulatory protein expression and RNA-binding activity. This regulation was potentially due to increased intracellular iron in lysosomes, which was demonstrated via the Fe(II)-selective probe, HMRhoNox-M, and was consistent with autophagic-induction. Immunofluorescence using LysoTracker and Pepstatin A probes demonstrated increased cellular lysosome content, which was confirmed by elevated LAMP1 expression. The enhanced lysosomal biogenesis after NTP could be due to the observed increase in fluid-phase endocytosis and early endosome formation. These results suggest NTP acts as a stressor, which results in increased endocytosis, lysosome content and autophagy. In fact, NTP rapidly increased autophagosome formation, as judged by increased LC3B-II expression, which co-localized with LAMP1, indicating autophagolysosome formation. Autophagic-induction by NTP was confirmed using electron microscopy. In summary, NTP acts as a cellular stressor to rapidly induce fluid-phase endocytosis, lysosome biogenesis and autophagy

Superconducting spin reorientation in spin-triplet multiple superconducting phases of UTe 2

International audienceSuperconducting (SC) state has spin and orbital degrees of freedom, and spin-triplet superconductivity shows multiple SC phases because of the presence of these degrees of freedom. However, the observation of spin-direction rotation occurring inside the SC state (SC spin rotation) has hardly been reported. Uranium ditelluride, a recently found topological superconductor, exhibits various SC phases under pressure: SC state at ambient pressure (SC1), high-temperature SC state above 0.5 gigapascal (SC2), and low-temperature SC state above 0.5 gigapascal (SC3). We performed nuclear magnetic resonance (NMR) and ac susceptibility measurements on a single-crystal uranium ditelluride. The b axis spin susceptibility remains unchanged in SC2, unlike in SC1, and decreases below the SC2-SC3 transition with spin modulation. These unique properties in SC3 arise from the coexistence of two SC order parameters. Our NMR results confirm spin-triplet superconductivity with SC spin parallel to b axis in SC2 and unveil the remaining of spin degrees of freedom in SC uranium ditelluride