The University of Tokyo
  • Bunkyō-ku, Tokyo, Japan
Recent publications
Local inertial equations (LIEs) proposed around 2010 have been implemented in many flood simulation models. The authors have studied, using both mathematical and numerical approaches, why LIEs present higher numerical stability over earlier flood simulation models and what explains their numerical stability. This article presents reviews of several individual publications by the authors in terms of 1) comparison between LIEs with diffusive wave equations, 2) effects of the discretization of the friction term, and 3) new discretization schemes maintaining stability and accuracy. This research note documents the research narrative that research networking has led to these research outcomes.
We establish a recursive representation that fully decouples jumps from a large class of multivariate inhomogeneous stochastic differential equations with jumps of general time-state dependent unbounded intensity, not of Lévy-driven type that essentially benefits a lot from independent and stationary increments. The recursive representation, along with a few related ones, are derived by making use of a jump time of the underlying dynamics as an information relay point in passing the past on to a previous iteration step to fill in the missing information on the unobserved trajectory ahead. We prove that the proposed recursive representations are convergent exponentially fast in the limit, and can be represented in a similar form to Picard iterates under the probability measure with its jump component suppressed. On the basis of each iterate, we construct upper and lower bounding functions that are also convergent towards the true solution as the iterations proceed. We provide numerical results to justify our theoretical findings.
Autologous costal cartilage grafts remain the gold standard method for microtia reconstruction. However, reports on its long-term outcomes are limited. We present two cases with >40-year outcomes after auricular reconstruction with autologous costal cartilage. A 56 year-old woman and a 53 year-old man presented to our institution with complaints of wire exposure. In both cases, the reconstructed ear was deformed. A computerized tomography scan revealed calcification of the reconstructed costal cartilage graft framework. To our knowledge, these cases present the longest outcomes (50 and 42 years for the 56 year-old woman and 53 year-old man, respectively) of microtia reconstruction using autologous cartilage grafts. We found that ear frameworks constructed from costal cartilage tended to calcify in the long term, as in the natural course of costal cartilage. Therefore, the possibility of calcification of costal cartilage grafts should be relayed to patients and parents, and lifelong surveillance after reconstruction should be recommended.
Sodium (Na) exclusion is vital for plants to cope with salt stress, and the plasma membrane Na⁺/H⁺ antiporter, SALT OVERLY SENSITIVE 1 (SOS1), has been known to play a central role in this process although the function of this molecule is not completely understood. In this study, we performed ²²Na⁺ radiotracer experiments to investigate the function of SOS1 in the mature root zone. Arabidopsis thaliana seedlings were placed on the gel medium, which had air gaps to separate the medium at the mature root zone from that at the root apex zone. Then, ²²Na⁺ was added to the root apex zone for 4 h, and the radioactivity in the mature root zone with 5 mm in length and in the mature root zone gel was measured. As a result, we found that knock-out of SOS1 caused ²²Na⁺ accumulation in the mature root zone and reduction of ²²Na⁺ exclusion to the gel, demonstrating that Na⁺ delivered via the xylem is excluded to the rhizosphere by SOS1 in the mature root zone.
Brk/Ptk6, Srms, and Frk constitute a Src-related but distinct family of tyrosine kinases called Brk family kinases (BFKs) in higher vertebrates. To date, however, their biological roles have remained largely unknown. In this study, we generated BFK triple-knockout (BFK/TKO) mice lacking all BFK members using CRISPR/Cas9-mediated genome editing. BFK/TKO mice exhibited impaired intestinal homeostasis, represented by a reduced stem/progenitor cell population and defective recovery from radiation-induced severe mucosal damage, specifically in the ileum, which is the most distal segment of the small intestine. RNA-seq analysis revealed that BFK/TKO ileal epithelium showed markedly elevated IL-22/STAT3 signaling, resulting in the aberrant activation of mucosal immune response and altered composition of the ileal microbiota. Since single- or double-knockout of BFK genes did not elicit such abnormalities, BFKs may redundantly confer robust homeostasis to the ileum, the most recently added intestinal segment that plays crucial roles in nutrient absorption and mucosal immunity. Given that BFK diversification preceded the appearance of the ileum in vertebrate phylogeny, the present study highlights the coevolution of genes and organs, the former of which shapes up the latter in higher vertebrates.
Identity-based threshold signature (IDTS) is a forceful primitive to protect identity and data privacy, in which parties can collaboratively sign a given message as a signer without reconstructing a signing key. Nevertheless, most IDTS schemes rely on a trusted key generation center (KGC). Recently, some IDTS schemes can achieve escrow-free security against corrupted KGC, but all of them are vulnerable to denial-of-service attacks in the dishonest majority setting, where cheaters may force the protocol to abort without providing any feedback. In this work, we present a fully decentralized IDTS scheme to resist corrupted KGC and denial-of-service attacks. To this end, we design threshold protocols to achieve distributed key generation, private key extraction, and signing generation which can withstand the collusion between KGCs and signers, and then we propose an identification mechanism that can detect the identity of cheaters during key generation, private key extraction and signing generation. Finally, we formally prove that the proposed scheme is threshold unforgeability against chosen message attacks. The experimental results show that the computation time of both key generation and signing generation is <1 s, and private key extraction is about 3 s, which is practical in the distributed environment.
There is a considerable demand for cutting force estimation without additional sensors to improve the cutting process by machine tools. Some methods of cutting force estimation based on disturbance observer have been developed. However, some problems still exist in their practical application to cutting force estimation. This study aims to clarify and resolve the problems. First, two cutting force estimation methods based on the two-inertia model of the feed system of the machine tool are compared. Because the two methods are based on disturbance observer and perform time differentiation of the encoder signal, they are vulnerable to the quantization error. Therefore, the two methods are analyzed, in terms of their robustness to the quantization error, based on the discrete Lyapunov equation. The method that is tolerant to the quantization error is chosen for further analysis. The problem of the chosen method is the lead error, which is not considered in the two-inertia model. This lead error degrades the accuracy of the cutting force estimation. Therefore, identification and compensation methods for tackling the lead error are proposed. Experiments with an actual industrial machine tool are performed, and the presented method is validated.
Self-inductance variations caused by component tolerance and aging decrease the efficiency of wireless power transfer (WPT) systems. This paper deals with this issue by compensating for the self-inductance variations using pulsewidth modulation controlled switched capacitors. Previous methods relied on wireless communication between the transmitter (Tx) and receiver (Rx) to control the variable capacitors, which is not a feasible approach when considering practical constraints. This paper proposes a control scheme in which the switched capacitors are controlled simultaneously by separate closed-loops on the Tx and Rx sides, thus eliminating wireless communication. The control scheme is based on a unique condition for perfect resonance derived by focusing on the output power of the WPT circuit. This paper also points out the necessity to compensate for the self-inductance variations of both the Tx and Rx coils to achieve maximum AC/AC efficiency in battery charging applications. Furthermore, the proposed control scheme incorporates the soft switching condition of the inverter to improve the DC/DC efficiency. Experimental results of a 1-kW prototype show that the switched capacitors can flexibly adapt to the self-inductance variations and improve the AC/AC efficiency and DC/DC efficiency by up to 3.04% and 8.63%, respectively.
This paper presents for the first time the development of a self-powered synchronous electric charge extraction (SECE) circuit for an in-plane rotational electret kinetic energy harvester (EH) with a cold start function. As an electret EH features low source current and high output impedance, its output power is sensitive to the leakage current and the parasitic capacitance. A novel dual-stage electrode design is proposed, with the control stage providing a sub-5V supply to the control circuit and triggering a synchronous switch in the high-voltage main circuit. Compared to a conventional buck converter, the power harvested on a 5V load was doubled with the present SECE prototype. Based on the circuit simulations, the achievable power increase at the generator output with the proposed circuit is mainly constrained by the impedance introduced by itself. The experimental results show that the circuit can be cold-started and directly powered by electret EHs.
This paper proposes an online method for calibrating the orientation of cameras mounted on vehicles. To calibrate the orientation of the target camera relative to the vehicle, we propose using a high-speed vision sensor, focused on the ground, in conjunction with the target camera. First, the high-speed camera's planar motion parallel to ground plane and target camera's motion are estimated by a semi-dense approach and visual odometry method, respectively. Then, the motions are used to calibrate the target camera's orientation through nonlinear optimization based on the invariance constraint of the extrinsic parameters and the nonholonomic constraint of the vehicle. Unlike traditional methods, this approach does not depend on artificial features such as lane markings and utilizes ground information more efficiently, making it applicable in broader scenarios. Simulation and field tests have demonstrated that the target camera orientation calibration errors are approximately 1°, even on a bumpy road, affirming the accuracy and robustness of the proposed method.
Since charge injection from metals into insulating polymers leads to electrical degradation and failure of various electrical devices, it is essential to clarify the band alignment at the metal/insulating polymer interface. However, the electronic structure at the metal/insulating polymer interface has not been studied experimentally. In this contribution, band alignments at the Au/polytetrafluoroethylene (PTFE) and Au/polypropylene (PP) interfaces were determined by first principles calculations using density functional theory (DFT) and X-ray photoelectron spectroscopy (XPS) measurements. The calculated electronic properties on Au/PP interface are in agreement with the experimental results, indicating that the vacuum level shift at the interface is slight (below 0.3 eV). On the other hand, in the case of PTFE, even though the computed vacuum level shift for an ideal interface was small (-0.1 eV), the experimental results indicated that the vacuum level shift can be more than 1.7 eV. The results suggest that, in actual systems, the vacuum level shift may be caused by the impurities or defects at the interface. Our work has led us to conclude that the band alignment of the metal/polymer interface depends not only on the combination of material species but also on the way the contact is formed between them.
Fecal pellets (FPs) are generated by various species and have gained attention as contributors to the biological carbon pump. Metazoans and protozoans are known as FP and minipellet‐producers, respectively. Herein, we discovered fecal pellet‐like dinoflagellates (FLDs) in the seasonal sea ice zone in the Southern Ocean. The size and form of these FLDs were similar to those of zooplankton oval FPs. However, due to their appearance, they have been misclassified as FPs rather than dinoflagellates, leading to potential oversight of their role in the carbon cycle. Thus, we aimed to identify FLD cells at the species level and examine the impact of FLDs on flux estimation of particulate organic carbon (POC). Our findings are as follows: First, FLD cells were identified as Gyrodinium rubrum and G. heterogrammum through 18S rRNA gene sequencing. Second, FLDs can potentially excrete larger FPs than minipellets. Third, the sinking rate of FLDs is higher than that of other protozoa and dinoflagellate cysts. Finally, a maximum of 12 mgC m ‐2 d ‐1 of the POC flux can be attributed to FLDs (representing 32% of POC flux). These results suggest that FLDs are important drivers not only for the microbial loop but also for the biological carbon pump. In future projections of carbon sequestration, the contribution of metazoans to carbon export must be considered, but not that of FLDs. Their unknown physiological and ecological characteristics, especially including the responses to climate changes, must be urgently investigated for future projections of carbon sequestration in the Southern Ocean.
  • Kaiyi Jiang
    Kaiyi Jiang
  • Justin Lim
    Justin Lim
  • Samantha Sgrizzi
    Samantha Sgrizzi
  • [...]
  • Omar O. Abudayyeh
    Omar O. Abudayyeh
Programmable RNA-guided DNA nucleases perform numerous roles in prokaryotes, but the extent of their spread outside prokaryotes is unclear. Fanzors, the eukaryotic homolog of prokaryotic TnpB proteins, have been detected in genomes of eukaryotes and large viruses, but their activity and functions in eukaryotes remain unknown. Here, we characterize Fanzors as RNA-programmable DNA endonucleases, using biochemical and cellular evidence. We found diverse Fanzors that frequently associate with various eukaryotic transposases. Reconstruction of Fanzors evolution revealed multiple radiations of RuvC-containing TnpB homologs in eukaryotes. Fanzor genes captured introns and proteins acquired nuclear localization signals, indicating extensive, long-term adaptation to functioning in eukaryotic cells. Fanzor nucleases contain a rearranged catalytic site of the RuvC domain, similar to a distinct subset of TnpBs, and lack collateral cleavage activity. We demonstrate that Fanzors can be harnessed for genome editing in human cells, highlighting the potential of these widespread eukaryotic RNA-guided nucleases for biotechnology applications.
The widespread distribution of Prochlorococcus can be attributed to the extensive genetic diversity that allows them to adapt to various oligotrophic environments. We investigated the adaptation of Prochlorococcus to nutrient environments in the surface eastern Indian Ocean (EIO, 16.5°N to 20°S, 88°E) in November 2018. The growth rate of the Prochlorococcus population and its response to macronutrient enrichments (NH 4 ⁺ and PO 4 ³⁻ ) and the abundance of functional gene modules related to nutrient utilization were examined by on‐deck incubation experiments and metagenomic analysis, respectively. Although the dissolved inorganic nitrogen was depleted (∼58 nM) and the Prochlorococcus populations were dominated by the high‐light‐adapted II ecotype, Prochlorococcus populations showed distinct physiological patterns, especially the response to macronutrient enrichments, indicating their adaptation to local nutrient environments. At the northernmost station in the Bay of Bengal, the significant increase in growth rate with macronutrient enrichments and the highest abundance of the phosphate starvation response two‐component regulatory system module indicated adaptation to phosphorus‐limited environments. In the southern EIO, the insignificant increase in growth rate with macronutrient enrichment and higher abundance of the iron complex transport system module suggested adaptation to iron‐limited environments. However, genomic characteristics are not always associated with physiological characteristics. The abundance of the nitrate/nitrite transport system module was higher in the southern EIO, where the growth of Prochlorococcus relied on regenerated nitrogen sources as revealed by incubation experiments. These results reflected the complexity of Prochlorococcus adaptation especially in chronically oligotrophic environments, which was better revealed by combining physiological and genomic analyses.
In this paper we review the academic transportation literature published between 2014 and 2018 to evaluate where the field stands regarding the use and misuse of statistical significance in empirical analysis, with a focus on discrete choice models. Our results show that 39% of studies explained model results exclusively based on the sign of the coefficient, 67% of studies did not distinguish statistical significance from economic, policy or scientific significance in their conclusions, and none of the reviewed studies considered the statistical power of the tests. Based on these results we put forth a set of recommendations aimed at shifting the focus away from statistical significance towards proper and comprehensive assessment of effect magnitudes and other policy relevant quantities.
22q11.2 deletion syndrome is a microdeletion syndrome with an estimated prevalence of 1:2000-1:6000 live births. Various comorbidities and multimorbidity in physical, neurological, and intellectual aspects occur throughout life, resulting in poor quality of life(QOL)in individuals with 22q11.2 deletion syndrome. However, the relationship between multimorbidity and QOL remains unclear. This study investigated relationship between multimorbidity and QOL in individuals with 22q11.2 deletion syndrome using the National Database of Designated Incurable Diseases of Japan. Information on comorbidities(e.g., congenital heart disease, immunodeficiency due to impaired thymic development, intellectual disability)and QOL such as social, daily, and physical function was obtained for 87 individuals with 22q11.2 deletion syndrome who were registered in the database from 2015 to 2020. The relationship between the binary variables of the total number of comorbidities(3 or less, 4 or more)and each item of QOL(with or without difficulties)was analyzed with the χ2 test.Those with 4 or more comorbidities were more likely to report difficulties with social function than those with 3 or less(87% vs. 63%, p=0.03). Those with comorbidity 4 or more were also more likely to report difficulty with daily and physical function than those with comorbidity 3 or less, while not statistically significant. To improve the daily function, which is a domain of QOL, of individuals with 22q11.2 deletion syndrome, it may be necessary to establish a support system for those with more severe comorbidities in addition to reducing multimorbidity through treatment and support for each comorbidity.
Water quality parameters influence the abundance of pathogenic bacteria. The genera Aeromonas, Arcobacter, Klebsiella, and Mycobacterium are among the representative pathogenic bacteria identified in wastewater. However, information on the correlations between water quality and the abundance of these bacteria, as well as their reduction rate in existing wastewater treatment facilities (WTFs), is lacking. Hence, this study aimed to determine the abundance and reduction rates of these bacterial groups in WTFs. Sixty-eight samples (34 influent and 34 non-disinfected, treated, effluent samples) were collected from nine WTFs in Japan and Thailand. 16S rRNA gene amplicon sequencing analysis revealed the presence of Aeromonas, Arcobacter, and Mycobacterium in all influent wastewater and treated effluent samples. Quantitative real-time polymerase chain reaction (qPCR) was used to quantify the abundance of Aeromonas, Arcobacter, Klebsiella pneumoniae species complex (KpSC), and Mycobacterium. The geometric mean abundances of Aeromonas, Arcobacter, KpSC, and Mycobacterium in the influent wastewater were 1.2 × 104–2.4 × 105, 1.0 × 105–4.5 × 106, 3.6 × 102–4.3 × 104, and 6.9 × 103–5.5 × 104 cells mL−1, respectively, and their average log reduction values were 0.77–2.57, 1.00–3.06, 1.35–3.11, and −0.67–1.57, respectively. Spearman’s rank correlation coefficients indicated significant positive or negative correlations between the abundances of the potentially pathogenic bacterial groups and Escherichia coli as well as water quality parameters, namely, chemical/biochemical oxygen demand, total nitrogen, nitrate-nitrogen, nitrite-nitrogen, ammonium-nitrogen, suspended solids, volatile suspended solids, and oxidation-reduction potential. This study provides valuable information on the development and appropriate management of WTFs to produce safe, hygienic water.
  • Hayri Alper Arslan
    Hayri Alper Arslan
  • Yang Song
    Yang Song
  • Tong Wang
    Tong Wang
This paper studies the effects of reducing information uncertainty on matching outcomes in a college choice setting. Turkey reformed its college admissions in 1999, changing the preference submission process for 4-year programs from pre-exam to post-exam submission, both under the constrained Deferred Acceptance mechanism. A conceptual framework illustrates that the reform changed matching outcomes in two ways: (i) fewer programs with unfilled seats, (ii) more assortative matching between students and programs, i.e., higher cutoff ranks for more highly ranked programs. Results from a difference-in-differences strategy confirm such predictions and find that the reform led to less under-capacity among lower-ranked programs and stronger assortative matching between high-achieving students and highly ranked programs. Moreover, we find some suggestive evidence that the post-exam submission may have led to fewer enrolled students overall but more female students in 4-year programs.
  • Minh X. Nguyen
    Minh X. Nguyen
  • Chunyan Li
    Chunyan Li
  • Kate Muessig
    Kate Muessig
  • [...]
  • Vivian F. Go
    Vivian F. Go
Young men who have sex with men (YMSM) and young transgender women (YTGW) have unique challenges to HIV care. We conducted a systematic review to summarize behavioral and structural interventions exclusively targeting YMSM and YTGW living with HIV. We screened 6546 records published through August 19th, 2022 from six databases. For eligibility, studies needed to involve structural or behavioral interventions exclusively targeting YMSM and/or YTGW living with HIV or presenting disaggregated data in this group. Quality assessment was performed using the ICROMS checklist. Twenty studies from 18 interventions were included in the review. There was considerable heterogeneity in intervention characteristics, including population, location, content and format of the interventions and targeted outcomes. Half of the interventions were described as pilot studies, and all but one study was conducted in the United States. The most common outcomes included the HIV care continuum, followed by HIV knowledge and self-efficacy, HIV-risk behaviors and mental health. The evidence base remained sparse, and the results on effectiveness were inconsistent, with some interventions reporting improved outcomes among participants after receiving treatment and others not reporting any meaningful changes. Although there has been some progress in the development of interventions targeting this group, we highlighted several directions for future research. Interventions expanding to low-resource settings, addressing structural barriers, and targeting different aspects of health among participants are warranted. Rigorous studies with larger sample sizes that follow participants over longer periods are necessary to increase the strength of the evidence.
  • Tomohiro Tsuda
    Tomohiro Tsuda
  • Min Sheng
    Min Sheng
  • Hiroya Ishikawa
    Hiroya Ishikawa
  • [...]
  • Takato Mitsudome
    Takato Mitsudome
Iron-based heterogeneous catalysts are ideal metal catalysts owing to their abundance and low-toxicity. However, conventional iron nanoparticle catalysts exhibit extremely low activity in liquid-phase reactions and lack air stability. Previous attempts to encapsulate iron nanoparticles in shell materials toward air stability improvement were offset by the low activity of the iron nanoparticles. To overcome the trade-off between activity and stability in conventional iron nanoparticle catalysts, we developed air-stable iron phosphide nanocrystal catalysts. The iron phosphide nanocrystal exhibits high activity for liquid-phase nitrile hydrogenation, whereas the conventional iron nanoparticles demonstrate no activity. Furthermore, the air stability of the iron phosphide nanocrystal allows facile immobilization on appropriate supports, wherein TiO2 enhances the activity. The resulting TiO2-supported iron phosphide nanocrystal successfully converts various nitriles to primary amines and demonstrates high reusability. The development of air-stable and active iron phosphide nanocrystal catalysts significantly expands the application scope of iron catalysts.
Institution pages aggregate content on ResearchGate related to an institution. The members listed on this page have self-identified as being affiliated with this institution. Publications listed on this page were identified by our algorithms as relating to this institution. This page was not created or approved by the institution. If you represent an institution and have questions about these pages or wish to report inaccurate content, you can contact us here.
12,800 members
Takuya Umedachi
  • Graduate School of Information Science and Technology
Masayuki Hirafuji
  • International Field Phenomics Research laboratory
Yasuyuki Kawahigashi
  • Graduate School of Mathematical Sciences
Nashir Uddin
  • Department of Applied Biological Chemistry
Richard P. Shefferson
  • Organization for Programs on Environmental Science
Hongo 7-3-1, 1130033, Bunkyō-ku, Tokyo, Japan
Head of institution
Teruo Fujii