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Cover time of graphs with bounded genus [article]

Naoki Matsumoto, Yuuki Takai
2022 arXiv   pre-print
The cover time of a finite connected graph is the expected number of steps needed for a simple random walk on the graph to visit all vertices of the graph. It is known that the cover time of any finite connected n-vertex graph is at least (1 + o(1)) n log n and at most (1 + o(1)) 4/27 n^3. By Jonasson and Schramm, the cover time of any bounded-degree finite connected n-vertex planar graph is at least c n(log n)^2 and at most 6n^2, where c is a positive constant depending only on the maximal
more » ... ee of the graph. In particular, the lower bound is established via the use of circle packing of planar graphs on the Riemann sphere. In this paper, we show that the cover time of any finite n-vertex graph G with maximum degree Δ on the compact Riemann surface S of given genus g is at least c n(log n)^2/ Δ(g + 1) and at most (6 + o(1))n^2, where c is an absolute constant, if n is sufficiently large and three sufficient conditions for S and a circle packing of G filling S.
arXiv:2205.03757v1 fatcat:5tlv3jhnxzfwvk55mo2qvwurim

Clinical characteristics of progressing stroke in acute small deep infarcts

Hiroaki Minami, Takanori Miki, Hiroaki Matsumoto, Yuuki Miyaji, Atsushi Masuda, Shogo Tominaga, Yasuhisa Yoshida, Ikuya Yamaura, Shigeo Matsumoto, Shigeatsu Natsume
2011 Nosotchu  
doi:10.3995/jstroke.33.74 fatcat:iix7d4c3krfw7fs4g7kxsadvby

Symmetrization associated with hyperbolic reflection principle

Yuuki Ida, Tsuyoshi Kinoshita, Tomohiro Matsumoto
2018 Pacific Journal of Mathematics for Industry  
In this paper, in view of application to pricing of Barrier options under a stochastic volatility model, we study a reflection principle for the hyperbolic Brownian motion, and introduce a hyperbolic version of Imamura-Ishigaki-Okumura's symmetrization. Some results of numerical experiments, which imply the efficiency of the numerical scheme based on the symmetrization, are given.
doi:10.1186/s40736-017-0035-2 fatcat:uajyt3rowra33eeao5ltcikbsq

Evaluation of diffusion-perfusion mismatch for determining indication for emergency endovascular revascularization

Atsushi Masuda, Takanori Miki, Hiroaki Matsumoto, Yuuki Miyaji, Hiroaki Minami, Shogo Tominaga, Ikuya Yamaura, Shigeo Matsumoto, Toyokazu Fukumori, Yasuhisa Yoshida, Kouzou Yoshida
2010 Nosotchu  
脳卒中の外科 30: 434-437, 2002 6) 植田敏浩:頭蓋内狭窄病変に対する抗血栓療法と 脳血管内治療.脳卒中の外科 35: 73-82, 2007 , M.D. 1) , Takanori Miki, M.D. 1) , Hiroaki Matsumoto, M.D. 1) , Yuuki Miyaji, M.D. 1) , Hiroaki Minami, M.D. 1) , Shogo  ...  Tominaga, M.D. 1) , Ikuya Yamaura, M.D. 1) , Shigeo Matsumoto, M.D. 1) , Toyokazu Fukumori, M.D. 2) , Yasuhisa Yoshida, M.D. 1) and Kouzou Yoshida, M.D.  ... 
doi:10.3995/jstroke.32.441 fatcat:6zhvbqm5mje7fafzga6zpsnzzm

Ionic Liquid-Based Electrolytes Containing Surface-Functionalized Inorganic Nanofibers for Quasisolid Lithium Batteries

Takahiro Yuuki, Yuichi Konosu, Minoru Ashizawa, Takashi Iwahashi, Yukio Ouchi, Yoichi Tominaga, Rie Ooyabu, Hajime Matsumoto, Hidetoshi Matsumoto
2017 ACS Omega  
In the present study, surface amino-functionalized silica nanofibers (f-SiO2NFs, average diameter = 400 and 1000 nm) are used as one-dimensional (1-D) fillers of ionic liquid (IL)-based quasisolid electrolytes. On adding f-SiO2NFs to an IL (1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide, EMITFSA) containing lithium bis(trifluoromethanesulfonyl)-amide (LiTFSA), the well-dispersed 1-D nanofillers easily form a three-dimensional network structure in the IL, function as physical
more » ... s-linkers, and increase the viscosity of the composites, consequently providing a quasisolid state at a 3.5 wt % fraction of the NFs. Rheological measurements demonstrate that the prepared composites exhibit "gel-like" characteristics at 40-150 °C. All prepared composites show high ionic conductivities, on the order of 10-3 S cm-1, around room temperature. To investigate the additive effect of f-SiO2NFs in the composites, the lithium transference numbers are also evaluated. It is found that thinner NFs enhance the transference numbers of the composites. In addition, quasisolid lithium-ion cells containing the prepared composites demonstrate relatively high rate characteristics and good cycling performance at high temperature (125 °C).
doi:10.1021/acsomega.6b00480 pmid:31457475 pmcid:PMC6641074 fatcat:sokcsbov5fdixi53332ymwvioy

Enantioselective bromination of axially chiral cyanoarenes in the presence of bifunctional organocatalysts

Yuuki Wada, Akira Matsumoto, Keisuke Asano, Seijiro Matsubara
2019 RSC Advances  
Enantioselective bromination of axially chiral cyanoarenes bearing high intrinsic rotational barriers via dynamic kinetic resolution using bifunctional organocatalysts is reported.
doi:10.1039/c9ra05532k pmid:35527922 pmcid:PMC9072646 fatcat:5tqup4yjrjem3nrgkgoiaaw2ju

Low Overhead TCP/UDP Socket-based Tracing for Discovering Network Services Dependencies

Yuuki Tsubouchi, Masahiro Furukawa, Ryosuke Matsumoto
2022 Journal of Information Processing  
Matsumoto received his Ph.D. in informatics from Kyoto University, Kyoto, Japan, in 2017.  ...  * 1 https 1 :// Fig. 3 3 Fig. 3 CPU overhead. Fig. 4 4 Fig. 4 Latency overhead.  ... 
doi:10.2197/ipsjjip.30.260 fatcat:tspcref5avdphouhoron3scr6m

Bifunctional organocatalysts for the asymmetric synthesis of axially chiral benzamides

Ryota Miyaji, Yuuki Wada, Akira Matsumoto, Keisuke Asano, Seijiro Matsubara
2017 Beilstein Journal of Organic Chemistry  
Bifunctional organocatalysts bearing amino and urea functional groups in a chiral molecular skeleton were applied to the enantioselective synthesis of axially chiral benzamides via aromatic electrophilic bromination. The results demonstrate the versatility of bifunctional organocatalysts for the enantioselective construction of axially chiral compounds. Moderate to good enantioselectivities were afforded with a range of benzamide substrates. Mechanistic investigations were also carried out. 1518
doi:10.3762/bjoc.13.151 pmid:28845196 pmcid:PMC5550815 fatcat:z2merklrofdffkzcgwfrq3iamm

Association among (Nursery) School Absenteeism Surveillance System and Incidence of Infectious Diseases

Junko Kurita, Tamie Sugawara, Kayo Matsumoto, Yuuki Nakamura, Yasushi Ohkusa
2018 School Health  
We introduced the (Nursery) School Absenteeism Surveillance System ((N)SASSy) 1, 2) in Japan in 2009. It has been operated by the Japanese Society of School Health, recording information related to students who are absent from (nursery) school because of infectious diseases. The term "school" used in this paper means any educational institution in Japan, including kindergartens with 4 to 5-year-old students, elementary schools with 6 to 12-year-olds, junior high schools with 13 to 15-year-olds,
more » ... and high schools with 16 to 18-year-olds. Only elementary schools and junior high schools are compulsory education. However, some children younger than five years old attend nursery schools, which are welfare facilities (equivalent to "day care" in many nations) and not educational institutions. Therefore, we discriminate nursery schools from "schools." The term of (nursery) school in this paper includes both nursery schools and "schools." A s o f t h e e n d o f 2 0 1 4 , t h e s y s t e m c o v e r e d approximately 22,000 schools, which collectively account for about half of all schools in Japan. It also covers approximately 8,000 nursery schools, which collectively
doi:10.20812/jash.sh_091 fatcat:blo4qx3zwvfsldkwtkweekzf6i

Awareness, Attitudes, and Concerns Regarding Heated Tobacco Products among Physicians in Japan

Yuichiro Otsuka, Yoshitaka Kaneita, Osamu Itani, Yuuki Matsumoto, Yutaka Hatori, Satoshi Imamura
2022 Journal of Epidemiology  
New tobacco products, particularly heated tobacco products (HTPs), have been introduced across several international markets as alternatives to combustible products, such as cigarettes. However, there are limited studies on physicians' perceptions of HTPs. This study analyzes the awareness of HTPs among physicians and assesses their concerns and attitudes toward patients using HTPs. A self-administered questionnaire was sent to a sample of 7,500 member physicians (6,000 male and 1,500 female)
more » ... om the Japan Medical Association (JMA). The smoking status of physicians was categorized as never smokers, ever HTP smokers, current HTP smokers, and ever and current smokers of other products. Physicians' awareness and attitudes toward patients using HTPs were analyzed using descriptive statistics. The correlation between the outcomes was examined using logistic regression models, whereas physicians' concerns about HTPs were analyzed using descriptive statistics. Data were obtained from 5,492 physicians (21.9% women; aged 60.4±12.1 years) with a response rate of 74.6%. Overall, 76.7% of the physicians had awareness of HTP, and about half of whom asked patients about using HTPs. Physicians who took longer to discuss cessation were more likely to discourage patient use. Smoking status was associated with discouraging HTP use in patients. Physicians who had experience with HTP use were primarily concerned about the products' long-term safety and less about product regulation. Japanese physicians do not have sufficient information and knowledge about HTPs. Therefore, evidence-based guidelines are required to support physicians in advising patients against HTP use.
doi:10.2188/jea.je20210470 pmid:35370227 fatcat:ctetcqg5xzeynpnn6doptztrii

Telmisartan Exacerbates Cisplatin-Induced Nephrotoxicity in a Mouse Model

Atsuki Hosoda, Yoshio Matsumoto, Yuuki Toriyama, Takumi Tsuji, Yuya Yoshida, Shuji Masamichi, Takeyuki Kohno
2020 Biological and Pharmaceutical Bulletin  
Cisplatin (CDDP; cis-diamine dichloroplatinum)-induced nephrotoxicity is the main reason for dose limitations, which can reduce the efficacy of cancer treatment. Lower blood pressure and administration of renin angiotensin system (RAS) inhibitors have been reported as factors that exacerbate CDDP-induced nephrotoxicity; however, the detailed mechanisms remain unknown and the results of previous studies are conflicting. In this study, we examined the influence of various hypotensive drugs,
more » ... ing RAS inhibitors and calcium channel blockers, on CDDP-induced nephrotoxicity in BALB/c mice. The mice were divided into nine groups: (1) CDDP group (15 mg/kg CDDP), (2) AML group (5 mg/kg amlodipine), (3) ENA group (2.5 mg/kg enalapril), (4) telmisartan (TEL) group (10 mg/kg telmisartan), (5) LOS group (10 mg/kg losartan), (6) CDDP + AML group, (7) CDDP + ENA group, (8) CDDP + TEL group, and (9) CDDP + LOS group. Nephrotoxicity was evaluated by measuring serum creatinine (CRE) and blood urea nitrogen (BUN) levels. In addition, the kidney sections were stained with Masson's trichrome and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) to assess the renal fibrosis area and apoptotic area. Serum CRE and BUN levels were increased in the CDDP + ENA, CDDP + LOS, and CDDP + TEL groups compared to those in the CDDP alone group, and the CDDP + AML group showed an increasing trend. However, there was no correlation between ∆CRE or ∆BUN levels and ∆ systolic blood pressure. The CDDP + TEL group showed a significant increase in the renal fibrosis area. These results suggest that exacerbation of CDDP-induced nephrotoxicity is not correlated with systolic blood pressure but is associated with administration of RAS inhibitors, particularly TEL.
doi:10.1248/bpb.b20-00174 pmid:32879207 fatcat:nwilcuhkgff57azjklr4g2edzm

Thundercloud Project: Exploring high-energy phenomena in thundercloud and lightning [article]

Takayuki Yuasa, Yuuki Wada, Teruaki Enoto, Yoshihiro Furuta, Harufumi Tsuchiya, Shohei Hisadomi, Yuna Tsuji, Kazufumi Okuda, Takahiro Matsumoto, Kazuhiro Nakazawa, Kazuo Makishima, Shoko Miyake (+1 others)
2020 arXiv   pre-print
We designed, developed, and deployed a distributed sensor network aiming at observing high-energy ionizing radiation, primarily gamma rays, from winter thunderclouds and lightning in coastal areas of Japan. Starting in 2015, we have installed, in total, more than 15 units of ground-based detector system in Ishikawa Prefecture and Niigata Prefecture, and accumulated 551 days of observation time in four winter seasons from late 2015 to early 2019. In this period, our system recorded 51 gamma-ray
more » ... adiation events from thundercloud and lightning. Highlights of science results obtained from this unprecedented amount of data include the discovery of photonuclear reaction in lightning which produces neutrons and positrons along with gamma rays, and deeper insights into the life cycle of a particle-acceleration and gamma-ray-emitting region in a thundercloud. The present paper reviews objective, methodology, and results of our experiment, with a stress on its instrumentation.
arXiv:2007.13618v1 fatcat:3qu7fqwv6bg7pivn4qr2v3s5uu

Microwave-assisted Acid Hydrolysis of Konjac Products for Determining the Konjac Powder Content

2013 Analytical Sciences  
doi:10.2116/analsci.29.1049 pmid:24212730 fatcat:ufr6p4nnjnhfzi6jnb5vzsu7pe

Structural phase transitions of methane+ethane mixed-gas hydrate induced by 1,1-dimethylcyclohexane

Yuuki Matsumoto, Hiroshi Miyauchi, Takashi Makino, Takeshi Sugahara, Kazunari Ohgaki
2011 Chemical Engineering Science  
Methane+ethane+1,1-dimethylcyclohexane+water system was investigated by using Raman spectroscopy and isothermal phase equilibrium measurements under four-phase (gas+aqueous+ large guest species+hydrate phases) equilibrium conditions at 288.15 K. The results suggest that three kinds of hydrate structures emerge at 288.15 K in the methane+ethane+1,1-dimethyl-cyclohexane+water system. The hydrate structure for this system changed from structure-H to structure-I via structure-II with increase in
more » ... mole ratio of ethane to methane. NOMENCLATURE f CH4 Fugacity of methane [Pa] k 12 Binary parameter of methane+ethane mixed-gas in ordinary mixing rule [-] p Equilibrium pressure [Pa] y CH4 Mole fraction of methane in gas phase (water and 1,1-dimethylcyclohexane free) [-] y C2H6 Mole fraction of ethane in gas phase (water and 1,1-dimethylcyclohexane free) [-]  CH4 Fugacity coefficient of methane [-]
doi:10.1016/j.ces.2011.03.020 fatcat:4iwkm5zrcvgwnhk5sepbnuo3c4

Assessment of Physical and Mental Health in Male University Students with Varying Sleep Habits

2011 The Kurume Medical Journal  
doi:10.2739/kurumemedj.58.105 pmid:23047140 fatcat:pyujf7nh7vhafk2us4uegvnoau
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