21 research outputs found
Structural phase diagram of LaO1-xFxBiSSe: suppression of the structural phase transition by partial F substitutions
We have investigated low-temperature crystal structure of BiCh2-based
compounds LaO1-xFxBiSSe (x = 0, 0.01, 0.02, 0.03, and 0.5), in which anomalous
two-fold-symmetric in-plane anisotropy of superconducting states has been
observed for x = 0.5. From synchrotron X-ray diffraction experiments, a
structural transition from tetragonal to monoclinic was observed for x = 0 and
0.01 at 340 and 240 K, respectively. For x = 0.03, a structural transition and
broadening of the diffraction peak were not observed down to 100 K. These facts
suggest that the structural transition could be suppressed by 3% F substitution
in LaO1-xFxBiSSe. Furthermore, the crystal structure for x = 0.5 at 4 K was
examined by low-temperature (laboratory) X-ray diffraction, which confirmed
that the tetragonal structure is maintained at 4 K for x = 0.5. Our results
suggest that the two-fold-symmetric in-plane anisotropy of superconducting
states observed for LaO0.5F0.5BiSSe was not originated from structural symmetry
lowering.Comment: 15 pages, 5 figures + 3 supplemental figure
Three-dimensional electronic structure in ferromagnetic with breathing kagome bilayers
A large anomalous Hall effect (AHE) has been observed in ferromagnetic
with breathing kagome bilayers. To understand the
underlying mechanism for this, we investigate the electronic structure of
by angle-resolved photoemission spectroscopy
(ARPES). In particular, we use both vacuum ultraviolet light (VUV) and soft x
ray (SX), which allow surface-sensitive and relatively bulk-sensitive
measurements, respectively, and distinguish bulk states from surface states,
which should be unlikely related to the AHE. While VUV-ARPES observes
two-dimensional bands mostly due to surface states, SX-ARPES reveals
three-dimensional band dispersions with a periodicity of the rhombohedral unit
cell in the bulk. Our data show a good consistency with a theoretical
calculation based on density functional theory, suggesting a possibility that
is a magnetic Weyl semimetal.Comment: 6 pages, 4 figure
The tertiary structure of the human Xkr8–Basigin complex that scrambles phospholipids at plasma membranes
Xkr8–Basigin is a plasma membrane phospholipid scramblase activated by kinases or caspases. We combined cryo-EM and X-ray crystallography to investigate its structure at an overall resolution of 3.8 Å. Its membrane-spanning region carrying 22 charged amino acids adopts a cuboid-like structure stabilized by salt bridges between hydrophilic residues in transmembrane helices. Phosphatidylcholine binding was observed in a hydrophobic cleft on the surface exposed to the outer leaflet of the plasma membrane. Six charged residues placed from top to bottom inside the molecule were essential for scrambling phospholipids in inward and outward directions, apparently providing a pathway for their translocation. A tryptophan residue was present between the head group of phosphatidylcholine and the extracellular end of the path. Its mutation to alanine made the Xkr8–Basigin complex constitutively active, indicating that it plays a vital role in regulating its scramblase activity. The structure of Xkr8–Basigin provides insights into the molecular mechanisms underlying phospholipid scrambling
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 Neel 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 the
40-years of intense researches. 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. We moreover 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.Comment: 22 pages, 5 figure
Cell response analysis in SARS-CoV-2 infected bronchial organoids
気管支オルガノイドを用いた新型コロナウイルス研究とその創薬応用. 京都大学プレスリリース. 2022-05-30.COVID-19 Research Using Bronchial Organoids and Drug Discovery Applications. 京都大学プレスリリース. 2022-06-02.The development of an in vitro cell model that can be used to study severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) research is expected. Here we conducted infection experiments in bronchial organoids (BO) and an BO-derived air-liquid interface model (BO-ALI) using 8 SARS-CoV-2 variants. The infection efficiency in BO-ALI was more than 1, 000 times higher than that in BO. Among the bronchial epithelial cells, we found that ciliated cells were infected with the virus, but basal cells were not. Ciliated cells died 7 days after the viral infection, but basal cells survived after the viral infection and differentiated into ciliated cells. Fibroblast growth factor 10 signaling was essential for this differentiation. These results indicate that BO and BO-ALI may be used not only to evaluate the cell response to SARS-CoV-2 and coronavirus disease 2019 (COVID-19) therapeutic agents, but also for airway regeneration studies
Interpretable machine learning-based individual analysis of acute kidney injury in immune checkpoint inhibitor therapy.
BackgroundAcute kidney injury (AKI) is a critical complication of immune checkpoint inhibitor therapy. Since the etiology of AKI in patients undergoing cancer therapy varies, clarifying underlying causes in individual cases is critical for optimal cancer treatment. Although it is essential to individually analyze immune checkpoint inhibitor-treated patients for underlying pathologies for each AKI episode, these analyses have not been realized. Herein, we aimed to individually clarify the underlying causes of AKI in immune checkpoint inhibitor-treated patients using a new clustering approach with Shapley Additive exPlanations (SHAP).MethodsWe developed a gradient-boosting decision tree-based machine learning model continuously predicting AKI within 7 days, using the medical records of 616 immune checkpoint inhibitor-treated patients. The temporal changes in individual predictive reasoning in AKI prediction models represented the key features contributing to each AKI prediction and clustered AKI patients based on the features with high predictive contribution quantified in time series by SHAP. We searched for common clinical backgrounds of AKI patients in each cluster, compared with annotation by three nephrologists.ResultsOne hundred and twelve patients (18.2%) had at least one AKI episode. They were clustered per the key feature, and their SHAP value patterns, and the nephrologists assessed the clusters' clinical relevance. Receiver operating characteristic analysis revealed that the area under the curve was 0.880. Patients with AKI were categorized into four clusters with significant prognostic differences (p = 0.010). The leading causes of AKI for each cluster, such as hypovolemia, drug-related, and cancer cachexia, were all clinically interpretable, which conventional approaches cannot obtain.ConclusionOur results suggest that the clustering method of individual predictive reasoning in machine learning models can be applied to infer clinically critical factors for developing each episode of AKI among patients with multiple AKI risk factors, such as immune checkpoint inhibitor-treated patients
Strongly anisotropic high-temperature Fermi surface of the Kondo semimetal CeNiSn revealed by angle-resolved photoemission spectroscopy
The semimetallic behavior of the so-called "failed Kondo insulator" CeNiSn has been ascribed to a nodal line in the Kondo hybridization derived from a particular symmetry of the Ce 4f orbitals ground state. Here we investigate the geometry of the CeNiSn conduction band by combined angle-resolved photoemission spectroscopy (ARPES) in the high-temperature regime and Open core generalized gradient approximation plus spin-orbit coupling calculations, in order to determine how the nodal hybridization takes place. We identify the Fermi sheet involved in the semimetallic regime from its locus and its shape, respectively, in agreement with the expected nodal line and with quantum oscillations. We further extrapolate and discuss the low-temperature Fermi surface in terms of the expected nodal hybridization with a localized f-level. The obtained hypothetical low-temperature Fermi surface is compatible with the description from quantum oscillations, and with both the highly anisotropic magnetoresistance and the isotropic Nernst effect. This work offers an overview of the conduction band of CeNiSn before hybridization, and it paves the way to a definitive understanding of its low-temperature state. In addition, this work serves as a basis for more challenging low-temperature ARPES measurements.11Nsciescopu