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Search Results: 1 - 10 of 4421 matches for " Takashi Kawahara "
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Fundamental group of $C^{*}$-algebras with finite dimensional trace space
Takashi Kawahara
Mathematics , 2015,
Abstract: We introduce the fundamental group $F(A)$ of a unital $C^*$-algebra $A$ with finite dimensional trace space. We compute fundamental groups $F(A)$ of several $C^*$-algebras $A$ with $2$-dimensional trace space. K-theoretical obstruction and positivity enable us to compute the fundamental group easily. Moreover we show there are uncountably many mutually nonisomorphic simple $C^{*}$-algebras such that $F(A)=\{I_{n}\}$. Our study is essentially based on the computation of fundamental group by Nawata and Watatani.
Prismatic Algorithm for Discrete D.C. Programming Problems
Yoshinobu Kawahara,Takashi Washio
Computer Science , 2011,
Abstract: In this paper, we propose the first exact algorithm for minimizing the difference of two submodular functions (D.S.), i.e., the discrete version of the D.C. programming problem. The developed algorithm is a branch-and-bound-based algorithm which responds to the structure of this problem through the relationship between submodularity and convexity. The D.S. programming problem covers a broad range of applications in machine learning because this generalizes the optimization of a wide class of set functions. We empirically investigate the performance of our algorithm, and illustrate the difference between exact and approximate solutions respectively obtained by the proposed and existing algorithms in feature selection and discriminative structure learning.
Effect of Boron Addition on the Thermal Properties of Diamond-Particle-Dispersed Cu-Matrix Composites Fabricated by SPS  [PDF]
Kiyoshi Mizuuchi, Kanryu Inoue, Yasuyuki Agari, Motohiro Tanaka, Takashi Takeuchi, Jun-ichi Tani, Masakazu Kawahara, Yukio Makino, Mikio Ito
Journal of Materials Science and Chemical Engineering (MSCE) , 2016, DOI: 10.4236/msce.2016.49001
Abstract: Diamond particle dispersed copper (Cu) matrix composites were fabricated from the powder mixture composed of diamond, pure-Cu and boron (B) by spark plasma sintering (SPS). The composites were consolidated at 1173 K for 600 s by SPS. The reaction between the diamond particle and the Cu matrix in the composite was not confirmed by SEM observation and X-ray diffraction (XRD) analysis. The relative packing density of the Cu/diamond composites increased with B addition and attained 93.2% - 95.8% at the B content range between 1.8 vol.% and 13.8 vol.%. The thermal conductivity of the diamond-dispersed Cu composite drastically increased with B addition and reached the maximum value of 689 W/mK at 7.2 vol% B. Numerous transgranular fractures of diamond particles were observed on bending fracture surfaces of Cu-B/diamond composites. This indicates strong bonding between the diamond particle and the Cu matrix in the composite. The coefficient of thermal expansion of the composite falls in the upper line of Kerner’s model.
A case of infective endocarditis after transurethral prostatic resection
Kawahara Takashi,Taguchi Hiroki,Yamagishi Takuya,Udagawa Koichi
Urology Annals , 2010,
Abstract: We report a case of infective endocarditis (IE) after transurethral prostatic resection (TUR-P). A 63-year-old man who had underwent TUR-P for benign prostatic hyperplasia. After 40 days of surgery, he developed a fever. A diagnosis of IE was established by cardiography which detected large vegetation at mitral valve. After intravenous antibiotics therapy, he underwent mitral valve replacement surgery.
GroupLiNGAM: Linear non-Gaussian acyclic models for sets of variables
Yoshinobu Kawahara,Kenneth Bollen,Shohei Shimizu,Takashi Washio
Computer Science , 2010,
Abstract: Finding the structure of a graphical model has been received much attention in many fields. Recently, it is reported that the non-Gaussianity of data enables us to identify the structure of a directed acyclic graph without any prior knowledge on the structure. In this paper, we propose a novel non-Gaussianity based algorithm for more general type of models; chain graphs. The algorithm finds an ordering of the disjoint subsets of variables by iteratively evaluating the independence between the variable subset and the residuals when the remaining variables are regressed on those. However, its computational cost grows exponentially according to the number of variables. Therefore, we further discuss an efficient approximate approach for applying the algorithm to large sized graphs. We illustrate the algorithm with artificial and real-world datasets.
Ureteroscopy-Assisted Retrograde Nephrostomy (UARN) after Anatrophic Nephrolithotomy
Takashi Kawahara,Hiroki Ito,Hideyuki Terao,Yoshitake Kato,Takehiko Ogawa,Hiroji Uemura,Yoshinobu Kubota,Junichi Matsuzaki
Case Reports in Medicine , 2012, DOI: 10.1155/2012/164963
Abstract: Introduction. Open surgical anatrophic nephrolithotomy (ANL) had been the standard treatment for large renal calculi prior to the development of endoscopic devices and endoscopic techniques. A previous report described the efficacy of ureteroscopy-assisted retrograde nephrostomy (UARN) and presented a case of renal calculi successfully treated with UARN during percutaneous nephrolithotomy (PCNL) in a patient after ANL. Case Presentation. A 61-year-old male with left renal calculi was referred for further treatment. The patient was placed under general and epidural anesthesia, in a Galdakao-modified Valdivia position. A flexible ureteroscope (URS) was inserted, and a Lawson retrograde nephrostomy puncture wire was advanced into the flexible URS. The puncture wire then followed the route from the renal pelvis to the exit skin. Calculus fragmentation was undertaken using a pneumatic lithotripter. Conclusions. UARN for PCNL was therefore found to be a safe, effective, and appropriate treatment for a patient presenting with renal calculi after undergoing ANL.
Encrusted Ureteral Stent Retrieval Using Flexible Ureteroscopy with a Ho: YAG Laser
Takashi Kawahara,Hiroki Ito,Hideyuki Terao,Takehiko Ogawa,Hiroji Uemura,Yoshinobu Kubota,Junichi Matsuzaki
Case Reports in Medicine , 2012, DOI: 10.1155/2012/862539
Abstract: A 23-year-old female had bilateral ureteral stents placed due to bilateral renal stones and hydronephrosis. The bilateral ureteral stents were changed every 3 months. A kidney ureter bladder (KUB) film showed left encrustation along the ureteral stent thus necessitating removal; however, the ureteral stent could not be removed cystoscopically. The ureteral stent was, therefore, extracted using flexible ureteroscopy (URS) with a holmium (Ho): yttrium aluminum garnet (YAG) laser.
Use of FDG-PET in Radiation Treatment Planning for Thoracic Cancers
Katsuyuki Shirai,Akiko Nakagawa,Takanori Abe,Masahiro Kawahara,Jun-ichi Saitoh,Tatsuya Ohno,Takashi Nakano
International Journal of Molecular Imaging , 2012, DOI: 10.1155/2012/609545
Abstract: Radiotherapy plays an important role in the treatment for thoracic cancers. Accurate diagnosis is essential to correctly perform curative radiotherapy. Tumor delineation is also important to prevent geographic misses in radiotherapy planning. Currently, planning is based on computed tomography (CT) imaging when radiation oncologists manually contour the tumor, and this practice often induces interobserver variability. F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) has been reported to enable accurate staging and detect tumor extension in several thoracic cancers, such as lung cancer and esophageal cancer. FDG-PET imaging has many potential advantages in radiotherapy planning for these cancers, because it can add biological information to conventional anatomical images and decrease the inter-observer variability. FDG-PET improves radiotherapy volume and enables dose escalation without causing severe side effects, especially in lung cancer patients. The main advantage of FDG-PET for esophageal cancer patients is the detection of unrecognized lymph node or distal metastases. However, automatic delineation by FDG-PET is still controversial in these tumors, despite the initial expectations. We will review the role of FDG-PET in radiotherapy for thoracic cancers, including lung cancer and esophageal cancer. 1. Introduction Radiotherapy plays an important role in the treatment of thoracic cancers, such as non-small-cell lung cancer (NSCLC), small-cell lung cancer (SCLC), and esophageal cancer [1, 2]. Recent advances in accurate diagnosis improve the practice of curative radiotherapy, because patients with unsuspected metastases may avoid unnecessary local therapies and receive necessary systemic treatment. Accurate delineation of tumor volume is also important to prevent geographic misses in treatment planning. Indeed, an underestimation of tumor extension will result in tumor recurrence. In contrast, overestimation of the extension may increase unnecessary side effects. Therefore, delineation of tumor volumes is a crucial factor in curative radiotherapy. Currently, treatment planning is based on computed tomography (CT) imaging to contour the tumor. Tumor delineation is manually performed by each radiation oncologist in clinical practice, which leads to interobserver variability in tumor delineation. Accurate delineation of tumor volume requires the identification of anatomic borders of tumors based on accurate diagnosis. F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) and PET/CT have been reported to enable accurate staging and
Ureteral Stent Retrieval Using the Crochet Hook Technique in Females
Takashi Kawahara, Hiroki Ito, Hideyuki Terao, Takuya Yamagishi, Takehiko Ogawa, Hiroji Uemura, Yoshinobu Kubota, Junichi Matsuzaki
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0029292
Abstract: Introduction We developed a method for ureteral stent removal in female patients that requires no cystoscopy or fluoroscopic guidance using a crochet hook. In addition, we also investigated the success rate, complications and pain associated with this procedure. Methods A total of 40 female patients (56 stents) underwent the removal of ureteral stents. All procedures were carried out with the patients either under anesthesia, conscious sedation, or analgesic suppositories as deemed appropriate for each procedure including Shock Wave Lithotripsy (SWL), Ureteroscopy (URS), Percutaneous Nephrolithotomy (PCNL), and ureteral stent removal. At the time of these procedures, fluoroscopy and/or cystoscopy were prepared, but they were not used unless we failed to successfully remove the ureteral stent using the crochet hook. In addition, matched controls (comprising 50 stents) which were removed by standard ureteral stent removal using cystoscopy were used for comparison purposes. Results A total of 47 of the 56 stents (83.9%) were successfully removed. In addition, 47 of 52 (90.4%) were successfully removed except for two migrated stents and two heavily encrusted stents which could not be removed using cystoscopy. Ureteral stent removal using the crochet hook technique was unsuccessful in nine patients, including two encrustations and two migrations. Concerning pain, ureteral stent removal using the crochet hook technique showed a lower visual analogue pain scale (VAPS) score than for the standard technique using cystoscopy. Conclusions Ureteral stent removal using a crochet hook is considered to be easy, safe, and cost effective. This technique is also easy to learn and is therefore considered to be suitable for use on an outpatient basis.
Simultaneous RNA-Seq Analysis of a Mixed Transcriptome of Rice and Blast Fungus Interaction
Yoshihiro Kawahara, Youko Oono, Hiroyuki Kanamori, Takashi Matsumoto, Takeshi Itoh, Eiichi Minami
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0049423
Abstract: A filamentous fungus, Magnaporthe oryzae, is a causal agent of rice blast disease, which is one of the most serious diseases affecting cultivated rice, Oryza sativa. However, the molecular mechanisms underlying both rice defense and fungal attack are not yet fully understood. Extensive past studies have characterized many infection-responsive genes in the pathogen and host plant, separately. To understand the plant-pathogen interaction comprehensively, it is valuable to monitor the gene expression profiles of both interacting organisms simultaneously in the same infected plant tissue. Although the host-pathogen interaction during the initial infection stage is important for the establishment of infection, the detection of fungal gene expression in infected leaves at the stage has been difficult because very few numbers of fungal cells are present. Using the emerging RNA-Seq technique, which has a wide dynamic range for expression analyses, we analyzed the mixed transcriptome of rice and blast fungus in infected leaves at 24 hours post-inoculation, which is the point when the primary infection hyphae penetrate leaf epidermal cells. We demonstrated that our method detected the gene expression of both the host plant and pathogen simultaneously in the same infected leaf blades in natural infection conditions without any artificial treatments. The upregulation of 240 fungal transcripts encoding putative secreted proteins was observed, suggesting that these candidates of fungal effector genes may play important roles in initial infection processes. The upregulation of transcripts encoding glycosyl hydrolases, cutinases and LysM domain-containing proteins were observed in the blast fungus, whereas pathogenesis-related and phytoalexin biosynthetic genes were upregulated in rice. Furthermore, more drastic changes in expression were observed in the incompatible interactions compared with the compatible ones in both rice and blast fungus at this stage. Our mixed transcriptome analysis is useful for the simultaneous elucidation of the tactics of host plant defense and pathogen attack.
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