Showing papers by "Tokyo University of Science published in 2022"

Thermodynamic evidence for a field-angle-dependent Majorana gap in a Kitaev spin liquid

Abstract: The exactly solvable Kitaev model of two-dimensional honeycomb magnets has a quantum spin liquid phase characterized by the emergence of fractionalized Majorana fermion excitations. In the paramagnetic state of α-RuCl3 at high magnetic fields, a half-integer quantization of thermal Hall conductivity has been reported as a signature of edge currents carried by Majorana fermions, but the bulk nature of this state remains unconfirmed. Here, by measuring the heat capacity for different in-plane rotations of an applied magnetic field, we find strongly angle-dependent low-energy excitations in bulk α-RuCl3. The excitation gap has a sextuple node structure, and the gap amplitude increases with the field, as expected for itinerant Majorana fermions in the Kitaev model. Our thermodynamic observations of the opening and closing of the bulk gap according to the magnetic-field direction fully correspond with changes in the edge transport. Moreover, the behaviour at higher magnetic fields where the quantum thermal Hall effect vanishes is consistent with a nematic quantum spin liquid state with two-fold rotational symmetry. α-RuCl has a quantum magnetic phase that may be a spin liquid hosting Majorana fermion excitations. Heat capacity measurements show an anisotropic dependence on magnetic-field direction, consistent with predictions for the putative spin liquid.

First gadolinium loading to Super-Kamiokande

Abstract: In order to improve Super-Kamiokande’s neutron detection efficiency and to thereby increase its sensitivity to the diffuse supernova neutrino background flux, 13 tons of Gd2(SO4)3⋅8H2O (gadolinium sulfate octahydrate) was dissolved into the detector’s otherwise ultrapure water from July 14 to August 17, 2020, marking the start of the SK-Gd phase of operations. During the loading, water was continuously recirculated at a rate of 60 m3/h, extracting water from the top of the detector and mixing it with concentrated Gd2(SO4)3⋅8H2O solution to create a 0.02% solution of the Gd compound before injecting it into the bottom of the detector. A clear boundary between the Gd-loaded and pure water was maintained through the loading, enabling monitoring of the loading itself and the spatial uniformity of the Gd concentration over the 35 days it took to reach the top of the detector. During the subsequent commissioning the recirculation rate was increased to 120 m3/h, resulting in a constant and uniform distribution of Gd throughout the detector and water transparency equivalent to that of previous pure-water operation periods. Using an Am–Be neutron calibration source the mean neutron capture time was measured to be 115±1 μs, which corresponds to a Gd concentration of 111±2 ppm, as expected for this level of Gd loading. This paper describes changes made to the water circulation system for this detector upgrade, the Gd loading procedure, detector commissioning, and the first neutron calibration measurements in SK-Gd.

A hierarchical transcriptional network activates specific CDK inhibitors that regulate G2 to control cell size and number in Arabidopsis

Abstract: How cell size and number are determined during organ development remains a fundamental question in cell biology. Here, we identified a GRAS family transcription factor, called SCARECROW-LIKE28 (SCL28), with a critical role in determining cell size in Arabidopsis. SCL28 is part of a transcriptional regulatory network downstream of the central MYB3Rs that regulate G2 to M phase cell cycle transition. We show that SCL28 forms a dimer with the AP2-type transcription factor, AtSMOS1, which defines the specificity for promoter binding and directly activates transcription of a specific set of SIAMESE-RELATED (SMR) family genes, encoding plant-specific inhibitors of cyclin-dependent kinases and thus inhibiting cell cycle progression at G2 and promoting the onset of endoreplication. Through this dose-dependent regulation of SMR transcription, SCL28 quantitatively sets the balance between cell size and number without dramatically changing final organ size. We propose that this hierarchical transcriptional network constitutes a cell cycle regulatory mechanism that allows to adjust cell size and number to attain robust organ growth.

Densification of Y2O3 by flash sintering under an AC electric field

Abstract: Frequency dependence of the densification behavior of undoped Y2O3 sintered by the AC-flash sintering was systematically investigated at 500 V·cm−1 over a frequency range from 0.05 Hz to 1 kHz. The Y2O3 bodies sintered under an AC field showed a uniform microstructure, without an asymmetric grain size distribution between the electrodes. Almost fully-densified Y2O3 body was consolidated at 1 kHz exhibited a relative density greater than 99 % and an average grain size of 1.6 μm. The almost full densification probably resulted from the high input power at the relatively high onset temperature of 1300 °C at this frequency. The temperature dependence of the power dissipation during the AC-flash sintering experiments can be ascribed to the periodic fluctuations of the specimen temperature at low frequencies and to the phase shift between the applied field and the specimen current at high frequencies.

TAS-Seq is a robust and sensitive amplification method for bead-based scRNA-seq

Abstract: Abstract Single-cell RNA-sequencing (scRNA-seq) is valuable for analyzing cellular heterogeneity. Cell composition accuracy is critical for analyzing cell–cell interaction networks from scRNA-seq data. However, droplet- and plate-based scRNA-seq techniques have cell sampling bias that could affect the cell composition of scRNA-seq datasets. Here we developed terminator-assisted solid-phase cDNA amplification and sequencing (TAS-Seq) for scRNA-seq based on a terminator, terminal transferase, and nanowell/bead-based scRNA-seq platform. TAS-Seq showed high tolerance to variations in the terminal transferase reaction, which complicate the handling of existing terminal transferase-based scRNA-seq methods. In murine and human lung samples, TAS-Seq yielded scRNA-seq data that were highly correlated with flow-cytometric data, showing higher gene-detection sensitivity and more robust detection of important cell–cell interactions and expression of growth factors/interleukins in cell subsets than 10X Chromium v2 and Smart-seq2. Expanding TAS-Seq application will improve understanding and atlas construction of lung biology at the single-cell level.

Influence of anticancer agents on sexual function: An in vivo study based on the US FDA Adverse Event Reporting System.

Abstract: Patients with cancer are treated with chemotherapeutics that cause adverse effects, including erectile dysfunction (ED).We investigated erectile function in rats after the administration of anticancer agents based on data retrieved through mining of the US Food and Drug Administration (FDA) Adverse Event Reporting System (AERS) database.The statistical signal strength for the association between anticancer drugs and ED was calculated using the reporting odds ratio (ROR). A drug-event combination was detected when the lower limit of the 95% confidence interval (CI) of the ROR exceeded 1.00. Rats were administered anticancer agents detected in the FDA AERS analysis. Erectile function was assessed using intracavernous pressure (ICP) and mean arterial pressure (MAP) analysis after electrical stimulation of the cavernous nerve. Statistical significance was determined using Welch's t-test or two-way ANOVA.Melphalan (L-PAM; ROR = 4.72, 95% CI = 2.78-8.00), vincristine (VCR; ROR = 2.47, 95% CI = 1.54-3.97), docetaxel (DTX; ROR = 2.25, 95% CI = 1.28-3.95), methotrexate (MTX; ROR = 1.96, 95% CI = 1.39-2.75), and doxorubicin (DOX; ROR = 1.82, 95% CI = 1.07-3.19) enhanced ED risk. L-PAM and MTX decreased the ICP/MAP ratio 1 week after administration. VCR and DOX decreased erectile function 4 weeks after administration. DTX decreased erectile function at all assessed time points.Certain anticancer agents should be considered risk factors for ED. Our results provide possible treatment strategies for maintaining erectile function in cancer survivors, including careful erectile function monitoring after treatment.

Blow-up in a quasilinear parabolic–elliptic Keller–Segel system with logistic source

Abstract: This paper deals with the quasilinear parabolic–elliptic Keller–Segel system with logistic source, u t = Δ ( u + 1 ) m − χ ∇ ⋅ ( u ( u + 1 ) α − 1 ∇ v ) + λ ( | x | ) u − μ ( | x | ) u κ , x ∈ Ω , t > 0 , 0 = Δ v − v + u , x ∈ Ω , t > 0 , where Ω ≔ B R ( 0 ) ⊂ R n ( n ≥ 3 ) is a ball with some R > 0 ; m > 0 , χ > 0 , α > 0 and κ ≥ 1 ; λ and μ are continuous nonnegative functions. About this problem, Winkler (2018) found the condition for κ such that solutions blow up in finite time when m = α = 1 . In the case that m = 1 and α ∈ ( 0 , 1 ) as well as λ and μ are constants, some conditions for α and κ such that blow-up occurs were obtained in a previous paper (Tanaka and Yokota, 2020). Moreover, in the case that m ≥ 1 and α = 1 Black et al. (2021) showed that there exist initial data such that the corresponding solution blows up in finite time under some conditions for m and κ . The purpose of the present paper is to give conditions for m ≥ 1 , α > 0 and κ ≥ 1 such that solutions blow up in finite time.

Photocatalytic Overall Water Splitting Under Visible Light Enabled by a Particulate Conjugated Polymer Loaded with Palladium and Iridium**

Abstract: Polymer photocatalysts have received growing attention in recent years for photocatalytic hydrogen production from water. Most studies report hydrogen production with sacrificial electron donors, which is unsuitable for large-scale hydrogen energy production. Here we show that the palladium/iridium oxide-loaded homopolymer of dibenzo[b,d]thiophene sulfone (P10) facilitates overall water splitting to produce stoichiometric amounts of H2 and O2 for an extended period (>60 hours) after the system stabilized. These results demonstrate that conjugated polymers can act as single component photocatalytic systems for overall water splitting when loaded with suitable co-catalysts, albeit currently with low activities. Transient spectroscopy shows that the IrO2 co-catalyst plays an important role in the generation of the charge separated state required for water splitting, with evidence for fast hole transfer to the co-catalyst.

Impact of RNF213 founder polymorphism (p.R4810K) on the postoperative development of indirect pial synangiosis after direct/indirect combined revascularization surgery for adult Moyamoya disease

Abstract: Direct superficial temporal artery (STA) to middle cerebral artery (MCA) anastomosis combined with indirect pial synangiosis provides favorable surgical collaterals for Moyamoya disease (MMD), especially in adults; however, factors leading to the development of each direct and indirect collateral are not well documented.We aimed to investigate the association between RNF213 founder polymorphism (p.R4810K) and each direct and indirect collateral development. By qualitative and quantitative evaluations of direct and indirect surgical collaterals using time-of-flight MR angiography, postoperative development of each type of bypass was evaluated independently into two categories. Multivariate logistic regression analysis was performed to study the contributing factors for the development of each surgical collateral. Excellent development of postoperative direct and indirect bypass was observed in 65 hemispheres (70%) by qualitative evaluation, which was confirmed by quantitative evaluation. Multivariate logistic regression analysis of excellent indirect bypass development revealed a significant positive correlation with the p.R4810K (odds ratio, OR4.0; 95%-confidence interval, CI 1.2-16), advanced MR angiographic stage (OR9.5; 95%CI 1.7-73), and preoperative middle meningeal artery caliber (OR6.8; 95%CI 1.8-35), but a significant negative correlation was found with the excellent direct bypass development (OR0.17; 95%CI 0.03-0.75). No significant correlation was observed between excellent direct bypass development and the p.R4810K (OR0.95; 95%CI 0.37-2.4).In conclusion, excellent development of indirect collaterals after STA-MCA anastomosis combined with indirect pial synangiosis occurs more frequently in adult MMD with the RNF213 founder polymorphism, suggesting a role of the p.R4810K variant for marked in-growth of indirect collaterals and the utility of preoperative genetic analysis.

Effects of hydrophilic/hydrophobic blocks ratio of PEG-b-PLGA on emission intensity and stability of over-1000 nm near-infrared (NIR-II) fluorescence dye-loaded polymeric micellar nanoparticles

Abstract: Polymeric micellar nanoparticles (PNPs) composed of an amphiphilic block copolymer formed from hydrophilic and hydrophobic blocks and over-thousand-nanometer (OTN) near-infrared (NIR) fluorescent dye are promising fluorophores for the dynamic imaging of deep tissue. In this study, we examined the effect of the ratio of hydrophilic/hydrophobic blocks of a block copolymer, poly(ethylene glycol) (PEG)-b-poly(lactide-co-glycolide) (PLGA), on the properties of OTN-PNPs encapsulating IR-1061. OTN-PNPs with a higher molecular weight of PLGA cores showed higher emission and stabilities under physiological conditions. The PEG ratio to PLGA in the block copolymer decreased the stability of OTN-PNPs probably due to the invasion of water molecules into the polymer core. The results show that the in vivo stability and fluorescence properties can be tuned by adjusting the chain lengths of block copolymers and estimated using in vitro assays, which evaluates the brightness retention rate of the OTN-PNPs under physiological conditions.

Nakano positivity of singular Hermitian metrics and vanishing theorems \n of Demailly–Nadel–Nakano type

Abstract: In this article, we propose a definition of Nakano semi-positivity of singular Hermitian metrics on holomorphic vector bundles. By using this positivity notion, we establish $L^2$-estimates for holomorphic vector bundles with Nakano positive singular Hermitian metrics. We also show vanishing theorems, which generalize both Nakano type and Demailly-Nadel type vanishing theorems. As applications, we specifically construct globally Nakano semi-positive singular Hermitian metrics for several bundles, and prove vanishing theorems associated with them.

Numerical simulation of ultrasonic welding for CFRP using energy director

Abstract: For ultrasonic welding of carbon fiber-reinforced plastics (CFRPs), a sharp shaped resin called the energy director (ED), is usually inserted between them. In this study, finite element analyses for ultrasonic welding of CFRPs were performed using a two-dimensional model. The effects of the shape of the ED on the temperature increase, deformation history, and dissipated energy behaviors are discussed. Flat and triangular ED shapes are considered. From the results, it is easier for a triangular ED to increase the temperature than for a flat ED, and hence, the consumed energy and time are less for a triangular ED than for a flat ED. However, in the triangular ED, the temperature is distributed significantly, that is, there is a very high temperature at some point and a very low temperature at other points. Thus, unexpected chemical reactions, such as oxidation, may occur. This study concludes that a triangular ED is not always better than a flat ED. In any case, it was found that an abrupt temperature increase was caused by a synergistic effect. That is, the increase in temperature causes the viscoelastic and frictional dissipated energy to be remarkable, and the increase in the dissipated energy increases the temperature.

Influence of the difference in refractive index on the interface of an object and the surroundings in near-infrared fluorescence tomography

Abstract: The refraction of fluorescence from the inside of a sample at the surface results in fluctuations in fluorescence computed tomography (CT). We evaluated the influence of the difference in refractive index (RI) between the sample body and the surroundings on fluorescence CT results. The brightest fluorescent point is away from the correct point on the tomograms owing to the refraction. The speculated position is determined as the exact point if the RI ratio ranges between 0.97 and 1.03 by immersing the body in an RI matching liquid. The results can help in experimental settings of fluorescence CT for acquiring three-dimensional positional information.

Outcomes and risk factors for mortality in <i>Pneumocystis</i> pneumonia patients with rheumatoid arthritis: A multicentre retrospective cohort study

Abstract: The aim is to evaluate outcomes and risk factors for death in patients with rheumatoid arthritis (RA) who developed Pneumocystis pneumonia (PCP).We included RA patients who were diagnosed with PCP at seven participating community hospitals between July 2005 and October 2020. Clinical features were compared between survivors and non-survivors. Disease-modifying antirheumatic drugs (DMARDs) before PCP onset and after PCP recovery were also examined.Seventy RA patients developed PCP, and among them, 60 (85.7%) received methotrexate (MTX) monotherapy (40%) or MTX combination therapy with other DMARDs (45.7%). PCP was more likely to occur after 12 months of MTX monotherapy and within 3 months of MTX combination therapy. Thirteen patients (18.6%) died despite PCP treatment. Multivariable logistic regression analysis revealed that coexisting RA-associated interstitial lung disease (odds ratio, 6.18; 95% confidence interval, 1.17-32.63) and delayed PCP treatment with anti-Pneumocystis drugs (odds ratio, 15.29; 95% confidence interval, 1.50-156.15) are significant risk factors for PCP mortality in RA patients. Most survivors successfully resumed DMARD therapy without PCP prophylaxis; one recurrent PCP case was observed during follow-up (median, 4.1 years).To avoid a treatment delay, RA patients should be followed up for signs and symptoms of PCP development, especially those with RA-associated interstitial lung disease.

Ambiguity and self-protection: evidence from social distancing under the COVID-19 pandemic

Abstract: This paper studies how people make decisions over preventive behaviors under ambiguity (i.e., Knightian uncertainty) where they do not even know the probability of a loss. In the context of the current COVID-19 pandemic, scientific uncertainty makes it hard to evaluate not only whether one will be infected, but also probabilities such as the infection rate. We constructed a simple model and demonstrated how its effect was heterogeneous depending on ambiguity-attitudes. Motivated by the model, we further conducted a survey experiment in Japan where we manipulated the information regarding scientific uncertainty on COVID-19. We found that higher ambiguity induced by scientific uncertainty increased the level of social distancing among ambiguity-loving people, but such evidence was nonexistent for ambiguity-averse counterparts.