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Study on Fatigue Lifetimes and Their Variation of Mg Alloy AZ61 at Various Stress Ratios

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Materials Sciences and Applications 2018年第13期9卷 993-1007页

作者： Kenichi Masuda sotomi ishihara Minoru Ishiguro Hiroshi Shibata Department of Mechanical Engineering University of Toyama Toyama Japan National Institute of Technology Toyama College Toyama Japan

In this study, fatigue tests under different R ratios were conducted on the AZ61 Mg alloy to investigate its fatigue lifetimes and fatigue crack growth (FCG) behavior. The fracture surface of the failed specimens was investigated using a scanning electron microscope to study the size of the intermetallic compounds from which the pioneer fatigue crack initiated and led to the final failure of the specimen. To determine the maximum size of the intermetallic compounds existing within the cross section of the specimen at higher risk, Gumbel’s extreme-value statistics were utilized. In the present study, the intermetallic compounds contained within the specimen were assumed to be the initial cracks existing in the material before the fatigue tests. A modified linear elastic fracture-mechanics parameter, M, proposed by McEvily et al., was used to analyze the short FCG behavior under different stress ratios, R. The relation between the rate of FCG and M parameter was found to be useful and appropriate for predicting the fatigue lifetimes under different R ratios. Moreover, the probabilistic stress-fatigue life (P-S-N) curve of the material under different R ratios could be predicted with this method, which utilizes both the FCG law and a statistical distribution of sizes of the most dangerous intermetallic compounds. The evaluated results were in good agreement with the experimental ones. This correspondence indicates that the estimation method proposed in the present study is effective for evaluation of the probabilistic stress-fatigue life (P-S-N) curve of the material under different R ratios.

关键词： Fatigue Stress-Fatigue Life (S-N) Curve Probabilistic Stress-Fatigue Life (P-S-N) Curve Crack Growth Extruded Magnesium Alloy Intermetallic Compound Extreme-Value Statistics

Crack Growth Behavior in Cemented Carbide by Repeated Thermal Shock

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Materials Sciences and Applications 2018年第4期9卷 345-356页

作者： sotomi ishihara Hiroshi Shibata Kenichi Masuda Hiroko Mikado Minoru Ishiguro National Institute of Technology Toyama College Toyama Japan Department of Mechanical Engineering University of Toyama Toyama Japan YKK Corporation Kurobe Japan

In this study, fatigue crack growth (FCG) behavior of cemented carbide under the repeated thermal shock (RTS) was experimentally evaluated by using the thermal-shock experiment method developed by the authors. Tests were carried out using cemented carbide having two different WC crystal grain sizes. In addition, FCG behavior under rotating bending fatigue (RBF) test was investigated using the same cemented carbides. Then the FCG results obtained by the RTS test and the results of the RBF test obtained at stress ratio, R = -1, were compared with each other. Here, the stress ratio R is defined as, R = σmin/σmax;σmin and σmax are the minimum and the maximum stresses, respectively. From this comparison, it was found that the relation between the rate of fatigue crack growth (FCG) and the maximum stress intensity factor in the RTS tests was equivalent to the one obtained under the RBF tests at stress ratio of -1. From a practical point of view, this result is important as it indicates that it is not necessary to purposely perform RTS experiments. In this research, the effect of WC grain size on the short surface FCG behavior of the cemented carbide was also studied and discussed.

关键词： Fatigue Cemented Carbide Repeated Thermal Shock Fatigue Crack Growth

Algorithm Selection Method Based on Coupling Strength for Partitioned Analysis of Structure-Piezoelectric-Circuit Coupling

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Computer Modeling in Engineering & Sciences 2024年第2期138卷 1237-1258页

作者： Daisuke ishihara Naoto Takayama Department of Intelligent and Control Systems Kyushu Institute of TechnologyIizuka820-8502Japan

In this study, we propose an algorithm selection method based on coupling strength for the partitioned analysis ofstructure-piezoelectric-circuit coupling, which includes two types of coupling or inverse and direct piezoelectriccoupling and direct piezoelectric and circuit coupling. In the proposed method, implicit and explicit formulationsare used for strong and weak coupling, respectively. Three feasible partitioned algorithms are generated, namely(1) a strongly coupled algorithm that uses a fully implicit formulation for both types of coupling, (2) a weaklycoupled algorithm that uses a fully explicit formulation for both types of coupling, and (3) a partially stronglycoupled and partially weakly coupled algorithm that uses an implicit formulation and an explicit formulation forthe two types of coupling, *** examples using a piezoelectric energy harvester,which is a typicalstructure-piezoelectric-circuit coupling problem, demonstrate that the proposed method selects the most costeffectivealgorithm.

关键词： Multiphysics coupling strength partitioned algorithm structure-piezoelectric-circuit coupling strongly coupled algorithm weakly coupled algorithm

Hybrid Strategy of Partitioned and Monolithic Methods for Solving Strongly Coupled Analysis of Inverse and Direct Piezoelectric and Circuit Coupling

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Computer Modeling in Engineering & Sciences 2024年第8期140卷 1371-1386页

作者： Daisuke ishihara Syunnosuke Nozaki Tomoya Niho Naoto Takayama Department of Intelligent and Control Systems Kyushu Institute of TechnologyFukuokaJapan

The inverse and direct piezoelectric and circuit coupling are widely observed in advanced electro-mechanical systems such as piezoelectric energy *** strongly coupled analysis methods based on direct numerical modeling for this phenomenon can be classified into partitioned or monolithic *** formulation has its advantages and disadvantages,and the choice depends on the characteristics of each coupled *** study proposes a new option:a coupled analysis strategy that combines the best features of the existing formulations,namely,the hybrid partitioned-monolithic *** analysis of inverse piezoelectricity and the monolithic analysis of direct piezoelectric and circuit interaction are strongly coupled using a partitioned iterative hierarchical *** a typical benchmark problem of a piezoelectric energy harvester,this research compares the results from the proposed method to those from the conventional strongly coupled partitioned iterative method,discussing the accuracy,stability,and computational *** proposed hybrid concept is effective for coupled multi-physics problems,including various coupling conditions.

关键词： Structure-piezoelectric-circuit interaction energy harvesting partitioned method monolithic method hybrid method

Dynamic ultrasonography for optimizing treatment position in superior mesenteric artery syndrome:Two case reports and review of literature

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World Journal of Gastroenterology 2024年第5期30卷 499-508页

作者： Nobuaki Hasegawa Akihiko Oka Muyiwa Awoniyi Yuri Yoshida Hiroshi Tobita Norihisa Ishimura Shunji ishihara Department of Internal Medicine II Shimane University Faculty of MedicineIzumo 693-8501ShimaneJapan Department of Gastroenterology Hepatology and NutritionDigestive Disease and Surgery InstituteHepatology SectionCleveland ClinicClevelandOH 44195United States Clinical Laboratory Division Shimane University HospitalIzumo 693-8501ShimaneJapan Division of Hepatology Shimane University HospitalIzumo 693-8501Japan

BACKGROUND Superior mesenteric artery(SMA)syndrome is a rare cause of duodenal obstruction by extrinsic compression between the SMA and the aorta(SMA-Ao).Although the left lateral recumbent position is considered effective in the treatment of SMA syndrome,individual variations in the optimal patient position have been *** this report,we present two elderly cases of SMA syndrome that exhibited rapid recovery due to ultrasonographic dynamic evaluation of the optimal position for each *** SUMMARY Case 1:A 90-year-old man with nausea and *** diagnosis of SMA syndrome by computed tomography(CT),ultrasonography(US)revealed the SMA-Ao distance in the supine position(4 mm),which slightly improved in the lateral position(5.7–7.0 mm)without the passage of duodenal ***,in the sitting position,the SMA-Ao distance was increased to 15 mm accompanied by improved content ***,US indicated enhanced passage upon abdominal massage on the right *** day 2,the patient could eat comfortably with the optimal position and *** 2:An 87-year-old woman with *** the diagnosis of SMA syndrome and aspiration pneumonia by CT,dynamic US confirmed the optimal position(SMA-Ao distance was improved to 7 mm in forward-bent position,whereas it remained at 5 mm in the supine position).By day 7 when her pneumonia recovered,she could eat with the optimal *** The optimal position for SMA syndrome varies among *** US appears to be a valuable tool in improving patient outcomes.

关键词： Superior mesenteric artery syndrome Wilkie’s syndrome Cast syndrome Aorto-mesenteric compass syndrome Ultrasonography Case report

Depositional condition of Paleoproterozoic Francevillian carbonate rocks revisited from rare earth element contents

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Geoscience Frontiers 2024年第3期15卷 31-49页

作者： Satoshi Yoshida Karen Bakakas Mayika Yuki ishihara Mathieu Moussavou Hisashi Asanuma Tomohiko Sato Takafumi Hirata Cédric Ligna Yusuke Sawaki Amboise Edou-Minko Department of Earth Science and Astronomy The University of Tokyo3-8-1 Komaba Meguro-kuTokyo 153-8902Japan Center for Northeast Asian Studies Tohoku University41 KawauchiAoba-kuSendai 980-8576Japan Department of Geology Universitédes Sciences et Techniques de MasukuBP:90190025 FrancevilleGabon Department of Earth and Planetary Science The University of Tokyo7-3-1 HongoBunkyo-kuTokyo 113-0033Japan Geochemical Research Center The University of Tokyo7-3-1HongoBunkyo-kuTokyo 113-0033Japan Graduate School of Human and Environmental Studies Kyoto UniversityYoshida-nihonmatsuSakyo-kuKyoto 606-8501Japan Center for Fundamental Education Okayama University of Science1-1Ridai-choKita-kuOkayama CityOkayama 700-0005Japan

The Paleoproterozoic Francevillian Group in the eastern Gabonese Republic has been recently attracting increasing attention because it includes distinctive macroscopic structures interpreted as eukaryotic ***,its depositional setting and associated redox conditions need to be clearly *** clarify these,petrological studies and rare earth element(REE)abundances of carbonate rocks of the Francevillian Group in the Lastoursville basin were determined with ICP-MS coupled with a laser ablation sampling *** microscopic observations indicate that dolostones in this basin underwent the complicated diagenetic history,including sparitization,decomposition of organic matter,reduction of ferromanganese oxides,silicification,and later *** dolostones of lower Francevillian B(FB)Formation show heterogeneous textures formed by alterations during *** the alterations,changes of REE abundances and degrees of positive Y anomalies appear to have *** indicates that REE signatures in carbonate rocks can vary during *** high Mn contents in the dolostones of upper FB Formation were derived from the reduction of ferromanganese oxides in *** signatures of REE abundance in dolostones can be explained by the mixing of seawater and ferromanganese oxide *** that sense,the dolostones inherited the trace element characteristics of precursor ferromanganese oxides even after the diagenesis.Y/Ho values of the most primary parts of each sample exceed 33,the newly determined threshold value for marine carbonate rocks based on our *** magnitude of the La anomaly values also falls within the range of that of Holocene reefal *** indicate that a precursor of the dolostone of the Francevillian Group was deposited in a marine *** addition,presence of Ce anomalies in the upper FB Formation suggests that the Paleoproterozoic ocean was oxidized to such an ex

关键词： Carbonate diagenesis Francevillian Group LA-ICP-MS Seawater composition Y/Ho fractionation

Co-infection with Neisseria mucosa in a patient with tuberculous otitis media

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Journal of Otology 2024年第1期19卷 1-4页

作者： Tatsuya Hioki Kazuaki Soejima Yuki Goto Makoto Sugiura Takumi Umemura Yoshimi ishihara Yoshikazu Mutoh Daisuke Sakanashi Hiroshige Mikamo Department of Clinical Laboratory Tosei General Hospital160 Nishioiwake-choSetoAichi489-8642Japan Department of Respiratory Medicine and Allergy Tosei General Hospital160 Nishioiwake-choSetoAichi489-8642Japan Department of Otolaryngology Tosei General Hospital160 Nishioiwake-choSetoAichi489-8642Japan Department of Infection Control Team Tosei General Hospital160 Nishioiwake-choSetoAichi489-8642Japan Department of Infectious Diseases Tosei General Hospital160 Nishioiwake-choSetoAichi489-8642Japan Department of Infection Prevention and Control Aichi Medical University Hospital1-1 YazakokarimataNagakuteAichi480-1195Japan Department of Clinical Infectious Diseases Aichi Medical University1-1 YazakokarimataNagakuteAichi480-1195Japan

Tuberculous otitis media(TOM) is a rare manifestation caused by Mycobacterium tuberculosis with low incidence rates among extrapulmonary tuberculosis cases. Diagnosis is often delayed because of the presence of several clinical manifestations and the high prevalence of secondary bacterial infections. Few reports have attributed secondary bacterial infections in patients with TOM to commensal Neisseria. Thus, understanding the pathogenic mechanisms and clinical features of commensal Neisseria is important, considering its recent presentation as an infection-causing pathogen. Neisseria mucosa is a commensal inhabitant in humans and is generally considered non-pathogenic but can cause infection in rare cases. Here, we report an atypical secondary infection caused by Neisseria mucosa in an 81-year-old woman with TOM being treated for pulmonary tuberculosis. Direct purulent otorrhea smear microscopy revealed no acid-fast bacilli using Ziehl-Neelsen staining, whereas the phagocytosis of gram-negative cocci by white blood cells was confirmed using Gram staining. Otorrhea culture revealed the growth of N. mucosa. Subsequently, M. tuberculosis infection in the otorrhea was identified using a culture-based method. Vigilance is critical for the early detection of TOM to prevent further complications. This report raises awareness regarding TOM and provides insight into the pathogenicity of N. mucosa in otitis media.

关键词： Commensal neisseria Miliary tuberculosis Mycobacterium tuberculosis Neisseria mucosa Tuberculous otitis media

The neutrophil–osteogenic cell axis promotes bone destruction in periodontitis

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International Journal of Oral Science 2024年第1期16卷 154-162页

作者： Yutaro Ando Masayuki Tsukasaki Nam Cong-Nhat Huynh Shizao Zang Minglu Yan Ryunosuke Muro Kazutaka Nakamura Masatsugu Komagamine Noriko Komatsu Kazuo Okamoto Kenta Nakano Tadashi Okamura Akira Yamaguchi Kazuyuki ishihara Hiroshi Takayanagi Department of Immunology Graduate School of Medicine and Faculty of MedicineThe University of Tokyo7-3-1HongoBunkyo-kuTokyoJapan Department of Microbiology Tokyo Dental College2-1-14 Kanda-Misaki-choChiyoda-kuTokyoJapan Oral Health Science Center Tokyo Dental College2-9-18Kanda-Misaki-choChiyodakuTokyoJapan Department of Osteoimmunology Graduate School of Medicine and Faculty of MedicineThe University of Tokyo7-3-1HongoBunkyo-kuTokyoJapan Unit of Prosthodontics Laboratory of Oral-Maxillofacial Biology Faculty of Odonto-StomatologyUniversity of Medicine and Pharmacy at Ho Chi Minh CityHo Chi Minh CityVietnam Department of Oral and Maxillofacial Surgery Department of Sensory and Motor System MedicineGraduate School of MedicineThe University of TokyoTokyoJapan Division of Rheumatology Department of Internal MedicineKeio University School of MedicineTokyoJapan Department of Laboratory Animal Medicine Research InstituteNational Center for Global Health and MedicineTokyoJapan

The immune-stromal cell interactions play a key role in health and diseases. In periodontitis, the most prevalent infectious disease in humans, immune cells accumulate in the oral mucosa and promote bone destruction by inducing receptor activator of nuclear factor-κB ligand (RANKL) expression in osteogenic cells such as osteoblasts and periodontal ligament cells. However, the detailed mechanism underlying immune–bone cell interactions in periodontitis is not fully understood. Here, we performed single-cell RNAsequencing analysis on mouse periodontal lesions and showed that neutrophil–osteogenic cell crosstalk is involved in periodontitis-induced bone loss. The periodontal lesions displayed marked infiltration of neutrophils, and in silico analyses suggested that the neutrophils interacted with osteogenic cells through cytokine production. Among the cytokines expressed in the periodontal neutrophils, oncostatin M (OSM) potently induced RANKL expression in the primary osteoblasts, and deletion of the OSM receptor in osteogenic cells significantly ameliorated periodontitis-induced bone loss. Epigenomic data analyses identified the OSM-regulated RANKL enhancer region in osteogenic cells, and mice lacking this enhancer showed decreased periodontal bone loss while maintaining physiological bone metabolism. These findings shed light on the role of neutrophils in bone regulation during bacterial infection, highlighting the novel mechanism underlying osteoimmune crosstalk.

关键词： period neutrophil destruction

Ultrafast reorientation of the Néel vector in antiferromagnetic Dirac semimetals

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npj Computational Materials 2021年第1期7卷 1562-1568页

作者： Atsushi Ono Sumio ishihara Department of Physics Tohoku UniversitySendai 980-8578Japan

Antiferromagnets exhibit distinctive characteristics such as ultrafast dynamics and robustness against perturbative fields,thereby attracting considerable interest in fundamental physics and technological ***,it was revealed that the Néel vector can be switched by a current-induced staggered(Néel)spin-orbit torque in antiferromagnets with the parity-time symmetry,and furthermore,a nonsymmorphic symmetry enables the control of Dirac ***,the real-time dynamics of the magnetic and electronic structures remain largely ***,we propose a theory of the ultrafast dynamics in antiferromagnetic Dirac semimetals and show that the Néel vector is rotated in the picosecond timescale by the terahertz-pulse-induced Néel spin-orbit torque and other torques originating from magnetic *** reorientation accompanies the modulation of the mass of Dirac fermions and can be observed in real time by the magneto-optical *** results provide a theoretical basis for emerging ultrafast antiferromagnetic spintronics combined with the topological aspects of materials.

关键词： materials Dirac metals