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Search Results: 1 - 10 of 1095 matches for " Takehiko Ogawa "
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Solution for Ill-Posed Inverse Kinematics of Robot Arm by Network Inversion
Takehiko Ogawa,Hajime Kanada
Journal of Robotics , 2010, DOI: 10.1155/2010/870923
Abstract: In the context of controlling a robot arm with multiple joints, the method of estimating the joint angles from the given end-effector coordinates is called inverse kinematics, which is a type of inverse problems. Network inversion has been proposed as a method for solving inverse problems by using a multilayer neural network. In this paper, network inversion is introduced as a method to solve the inverse kinematics problem of a robot arm with multiple joints, where the joint angles are estimated from the given end-effector coordinates. In general, inverse problems are affected by ill-posedness, which implies that the existence, uniqueness, and stability of their solutions are not guaranteed. In this paper, we show the effectiveness of applying network inversion with regularization, by which ill-posedness can be reduced, to the ill-posed inverse kinematics of an actual robot arm with multiple joints. 1. Introduction In the context of controlling a robot arm with multiple joints, the problem of estimating the joint angles from the given end-effector coordinates is called the inverse kinematics problem, which is a type of inverse problems [1]. Inverse problems that estimate the cause from the given results are studied in various engineering fields [2]. There are a number of methods for solving inverse kinematics problems: analytical method, iterative calculation by using an algorithm, and so forth [1]. In addition, neural-network-based inverse modeling has been proposed [3], and we can use it as a solution of inverse kinematics [4, 5]. The network inversion method has been proposed for solving inverse problems by using a multilayer neural network [6]. In this method, inverse problems are solved by using a trained multilayer neural network inversely to estimate the corresponding input from the given output [7, 8]. The advantages of this method are easiness of the direct modeling by learning and adaptive estimation of the inverse solution. It has been applied to actual problems [9, 10]. In addition, it was introduced as a method to solve the inverse kinematics problem of estimating the multiple joint angles of a robot arm from the given end-effector coordinates [11–13]. In general, inverse problems are affected by ill-posedness, which implies that the existence, uniqueness, and stability of their solutions are not guaranteed [2]. Ill-posedness also affects the solution when a problem is solved using network inversion. The regularization method to decrease ill-posedness by limiting the solution space of the inverse problem has been proposed for the ill-posed
Solution of Ill-Posed Inverse Problem of Distributed Generation Using Complex-Valued Network Inversion
Takehiko Ogawa,Kyosuke Nakamura,Hajime Kanada
Lecture Notes in Engineering and Computer Science , 2011,
Loss of Masticatory Function Affects Growth and Development of the Mandibular Condyle in Rats  [PDF]
Kei Ogawa, Yuri Kiguchi, Seiko Yamamoto-Nemoto, Norimitsu Hirai, Kanako Sawamoto, Takehiko Shimizu
Open Journal of Stomatology (OJST) , 2016, DOI: 10.4236/ojst.2016.612032
Abstract: The effects of childhood masticatory function loss and soft foods on the mandibular condyle have been the subject of much research. However, the corresponding bone turnover is not fully understood. The purpose of the present study was to clarify the effects of a lack of teeth and a soft food diet during the growth period on bone turnover in the mandibular condyle. We divided 3-week-old Wistar rats into the following three groups: 1) Extraction group: The maxillary molars were extracted at the age of 4 weeks, and animals were fed powdered standard feed. 2) Powder group: Animals were fed powdered standard feed without tooth extraction. 3) Control group: Animals were fed solid standard feed without tooth extraction. Non-decalcified thin-slice specimens of sagittal sections of the mandibular condyle were obtained at the age of 20 weeks for histological analysis. We used micro-CT analysis and bone histomorphometry to measure bone volume (BV), bone mineral content (BMC), bone mineral density (BMD), bone microstructure, bone resorption, and osteogenesis in the mandibular condyle, and we compared the results among groups. In the extraction and the powder groups, we found deformation and disruption of the arrangement of chondrocytes, coagulation of chondrocytes, and duplication of the tidemark in the cartilage. We also found an increase in multinuclear osteoclasts in the cancellous bone. We found a reduction in BV, BMC, and BMD in the extraction and powder groups compared to the control group, as well as a reduction of bone volume, a lowering of osteogenesis parameters, and an increase in bone resorption parameters in the secondary cancellous bone. These results suggest that a lack of teeth and a soft food diet during the growth period cause a decline in bone microstructure, a decrease in osteogenesis, and an increase in bone resorption.
Improvement of Bone and Dental Phenotype of Murine Hypophosphatasia Mediated by a Single Injection of Lentiviral Gene Therapy  [PDF]
Seiko Yamamoto-Nemoto, Kei Ogawa, Eri Yokoi, Kanako Sawamoto, Akane Yamaguchi, Elif Bahar Tuna, Takehiko Shimizu
Open Journal of Stomatology (OJST) , 2017, DOI: 10.4236/ojst.2017.71005
Abstract: Background: Alkaline phosphatase has 4 isozymes, tissue non-specific alkaline phosphatase (TNAP), placental alkaline phosphatase (PLAP), intestinal alkaline phosphatase and germ-cell alkaline phosphatase. Hypophosphatasia (HPP) is an inherited skeletal disease caused by mutations of the gene encoding TNAP. Although TNAP is expressed in various tissues, the primary HPP symptoms appear in bones and teeth. The clinical severity of HPP varies widely from the most severe (perinatal, infantile and childhood) to the mildest forms (adult, and odonto-hypophosphatasia). We reported that gene therapy using a single injection of lentiviral vector expressing bone-targeted TNAP (TNAP-D10) is effective in preventing all the skeletal of HPP in TNAP knockout (Alpl/) mice as the model of infantile HPP. Objective: In this study we focus on evaluating the efficacy of treatment with gene therapy on the bone and teeth using TNAP-D10 and also we investigate the feasibility of gene therapy using bone-targeted PLAP (PLAP-D10). Methods and Findings: We used Alpl/mice that develop skeletal disease at postnatal days 6-8 mimicking the infantile form of human HPP. We injected 100 μl of lentiviral vectors harboring TNALP-D10 (5.0 × 107 TU) or PLAP-D10 (5.0 × 107 TU) to 1-day-old Alpl/–?mice via the jugular vein. We performed histological analysis and micro-CT evaluation on bone and mandible of Alpl/?mice. The alveolar bone, enamel and dentin defects were corrected on treated Alpl/?mice by this treatment. Additionally the long bone growth rates (LGR) of long bones were encouraged on treated Alpl/?mice compared with untreated mice. Conclusions: These results indicate that the bone-targeted TNAP treatment mediated by lentivirus can correct not only the bone disorder but also the dental symptoms in Alpl/
Oral Symptoms and Bone Observations in Odonto-Hypophosphatasia  [PDF]
Seiko Yamamoto-Nemoto, Rina Shimada, Hanako Tajima, Emiko Iwasawa, Yoko Shimizu, Elif Bahar Tuna, Kei Ogawa, Atsushi Watanabe, Takehiko Shimizu
Open Journal of Stomatology (OJST) , 2016, DOI: 10.4236/ojst.2016.612030
Abstract: Hypophosphatasia (HPP) is an inherited skeletal disease caused by mutation of the gene encoding tissue non-specific alkaline phosphatase (TNSALP). Odonto-HPP is well known as the mildest of HPP. The manifestations involve only the teeth, such as premature primary teeth exfoliation caused by reduction of alveolar bone, enlarged dental pulp chamber, and dental defects. We report a case of a 9-years-old boy who developed HPP. He was observed from the primary dentition to the mixed dentition period. At initial presentation at our hospital, he had multiple premature exfoliation of primary teeth and reduction of the alveolar bone. HPP was suspected due to the low level of ALP activity in serum, his oral manifestation, and dental history. He was referred to a physician for the final diagnosis. Therefore his compound heterozygote mutations, c.1559 delT (T/delT) and c.407G > A (G/A), were found in TNSALP and he diagnosed with odonto-HPP. Even though these mutations were reported as being involved in odonto-HPP, his mineral densities tended to be lower than that of his age. It is therefore necessary to investigate the bone mineralization level in odonto-HPP without other bone symptoms. Moreover, ongoing enzyme-replacement therapy in odonto-HPP might improve dental abnormality and bone disorders.
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.
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.
Ureteroscopy-assisted retrograde nephrostomy for lower calyx calculi in horseshoe kidney: two case reports
Takashi Kawahara, Hiroki Ito, Hideyuki Terao, Katsuyuki Tanaka, Takehiko Ogawa, Hiroji Uemura, Yoshinobu Kubota, Junichi Matsuzaki
Journal of Medical Case Reports , 2012, DOI: 10.1186/1752-1947-6-194
Abstract: Case 1 was a 68-year-old man who was shown on radiography to have left lower calyx calculi (19?×?15mm, 7?×?5mm, and 7?×?3mm) in horseshoe kidney. Case 2 was a 36-year-old woman shown on radiography to have a left lower calyx calculus (10?×?8mm) in horseshoe kidney.Both patients were stone-free after ureteroscopy-assisted retrograde nephrostomy during percutaneous nephrolithotomy. Ureteroscopy-assisted retrograde nephrostomy is a promising procedure for safely and effectively treating lower calyx stones in horseshoe kidney.
Utility and Limitation of Cumulative Stone Diameter in Predicting Urinary Stone Burden at Flexible Ureteroscopy with Holmium Laser Lithotripsy: A Single-Center Experience
Hiroki Ito, Takashi Kawahara, Hideyuki Terao, Takehiko Ogawa, Masahiro Yao, Yoshinobu Kubota, Junichi Matsuzaki
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0065060
Abstract: Purpose To retrospectively assess the clinical utility in ureteroscopy (URS) planning of cumulative stone diameter (CSD), which does not account for stone width or depth, as a predictor of URS outcome and compare it with stone volume. Materials and Methods Patients with renal stones treated at a single institute by flexible URS were retrospectively evaluated. To assess the clinical utility of CSD, relationships between stone-free (SF) status and stone burden (CSD and volume) were analyzed using the area under the receiver operating characteristics (AUROC) curve. To identify stone number impact on CSD, the AUROC of CSD divided by stone number was evaluated. Correlation coefficients of CSD and stone volume were also calculated for groups by stone number. Results In cases with CSD <20.0 mm, CSD and stone volume revealed equal ability to predict SF status. In cases with CSD ≥20.0 mm, stone volume showed higher predictive ability. The ROC curves for cases with ≥4 stones showed that CSD was less predictive of SF status than stone volume. The correlation coefficients of CSD and stone volume by stone number were 0.922 for 1 stone, 0.900 for 2–3 stones, and 0.661 for ≥4 stones. Conclusions In cases with CSD ≥20.0 mm or ≥4 stones, we should evaluate stone volume for a more predictive stone burden, and pretreatment non-contrast CT seems sufficient. In cases with CSD <20.0 mm or 1–3 stones, CSD was as valid a predictor of preoperative stone burden as stone volume, so preoperative kidney-ureter-bladder (KUB) films may be sufficient.
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