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208 results on '"Onizawa, K."'

23. International round robin test on Master Curve reference temperature evaluation utilizing Miniature C(T) specimen

Author

Yamamoto, M., Onizawa, K., Yoshimoto, K., Ogawa, T., Mabuchi, Y., Valo, M., Lambrecht, M., Viehrig, H.-W., Miura, N., Soneda, N., Yamamoto, M., Onizawa, K., Yoshimoto, K., Ogawa, T., Mabuchi, Y., Valo, M., Lambrecht, M., Viehrig, H.-W., Miura, N., and Soneda, N.

Abstract

The Master Curve (MC) method is a promising technique for evaluating the fracture toughness of ferritic steels. It enables the determination of the reference temperature, To, of a probabilistic fracture toughness curve using small specimens. The Central Research Institute of Electric Power Industry (CRIEPI) investigated this capability of the MC method using different size of C(T) specimens, and it was found that 0.16T-C(T) specimen with the dimensions of 10mm by 10mm by 4mm, hereafter called “Mini-CT specimen”, can be used to obtain valid To values. The advantage of this Mini-CT specimen technique is that multiple specimens can be machined from one of broken halves of Charpy size specimens, which are used in a standard surveillance capsule of a reactor pressure vessel (RPV). In order to ensure the robustness of this technique, a round-robin test was planned. The idea is to perform MC tests using Mini-CT specimens by different investigators to see if consistent To values can be obtained. All the specimens used were machined and pre-cracked by one fabricator from unique RPV material to avoid any possible effect of specimen preparation on To values. Seven institutes participated in this exercise, and obtained valid To values. No specific difficulty was found in the MC tests performed in accordance to the ASTM E1921 protocol. The scatter of the obtained To values was well within the uncertainty range defined in Appendix X4.2 of ASTM E1921, indicating the robustness of the Mini-CT specimen technique in terms of the testing procedure. Throughout this activity, we could obtain 182 KJc (1Teq) for a single material. We investigated the statistics of this large database, and found that there is no remarkable difference not only in the To values but also in the fracture toughness distribution between the Mini-CT specimen and the standard 1T-C(T) specimen results.

Published
2015

24. Purified Human Dental Pulp Stem Cells Promote Osteogenic Regeneration

Author

Yasui, T., primary, Mabuchi, Y., additional, Toriumi, H., additional, Ebine, T., additional, Niibe, K., additional, Houlihan, D.D., additional, Morikawa, S., additional, Onizawa, K., additional, Kawana, H., additional, Akazawa, C., additional, Suzuki, N., additional, Nakagawa, T., additional, Okano, H., additional, and Matsuzaki, Y., additional

Published
2015
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25. IAEA coordinated research project on master curve approach to monitor fracture toughness of RPV steels: final results of an analytical round robin exercise to support constraint effects

Author

Scibetta, M., Altstadt, E., Sang, L. B., Callejas, R. H., Miura, N., Onizawa, K., Paffumi, E., Serrano, M., Tatar, L., and Yin, S.

Subjects
constraint, numerical fracture mechanics, local approach, Fracture toughness, Bermin model
Abstract

There is strong interest from the nuclear industry to use the precracked Charpy single-edge notched bend, SE(B), specimen (PCVN) to enable determination of the reference temperature, T0, with reactor pressure vessel surveillance specimens. Unfortunately, for many different ferritic steels, tests with the PCVN specimen (10x10x55 mm) have resulted in T0 temperatures up to 25°C lower than T0 values obtained using data from compact, C(T), specimens. This difference in T0 reference temperature has often been designated a specimen bias effect, and the primary focus for explaining this effect is loss of constraint in the PCVN specimen. The International Atomic Energy Agency has developed a three-part coordinated research project (CRP) to evaluate various issues associated with the fracture toughness Master Curve for application to light-water reactor pressure vessels. One part of the CRP is focused on the issue of test specimen geometry effects, with emphasis on the PCVN bias. This topic area was organized in two parts, an experimental part and an analytical part with a view towards each part complementing the other. Within the analytical part, elastic plastic finite element methods are extensively used in order to access local stress and strain information that is the basic ingredient for most of the micro-models of cleavage fracture developed to date. In the framework of the international qualification and acceptance of such a tool for actual loss of constraint prediction, the validation of such tool is of prime importance. Therefore, a round robin exercise has been proposed and performed by ten laboratories from nine different countries. The round robin focuses on the modeling of realistic three-dimensional geometries containing shallow and deep crack. This round robin has been useful to qualify different finite element codes and to identify possible errors in the input file. The round robin demonstrates that errors in the input file can be easily introduced. Some remaining differences cannot be attributed to one particular finite element code or to actual errors. Those differences are attributed to the so called "user effect" which can only be reduced through in depth discussion and deep understanding of each finite element code. Independently of the used code and of relatively small user effect differences, it is found that shallow crack specimens are more sensitive to loss of constraint than deep crack specimens for a given specimen size. The difference in terms of reference temperature between the two geometries is evaluated to be about 40 °C. For a deep crack, loss of constraint is identified to appear at M values around 200. This value is larger than the one specified in current standard (M = 30). Increasing the M value to 200 will jeopardize the use of PCVN for the nuclear industry on the other hand bias introduced by M value of 30 is acceptable.

Published
2009

32. Purified Human Dental Pulp Stem Cells Promote Osteogenic Regeneration.

Author

Yasui, T., Mabuchi, Y., Toriumi, H., Ebine, T., Niibe, K., Houlihan, D. D., Morikawa, S., Onizawa, K., Kawana, H., Akazawa, C., Suzuki, N., Nakagawa, T., Okano, H., and Matsuzaki, Y.

Subjects
DENTAL pulp, STEM cells, BONE regeneration, FLOW cytometry, PROGENITOR cells, CELL proliferation, CELL differentiation, MESENCHYMAL stem cells
Abstract

Human dental pulp stem/progenitor cells (hDPSCs) are attractive candidates for regenerative therapy because they can be easily expanded to generate colony-forming unit-fibroblasts (CFU-Fs) on plastic and the large cell numbers required for transplantation. However, isolation based on adherence to plastic inevitably changes the surface marker expression and biological properties of the cells. Consequently, little is currently known about the original phenotypes of tissue precursor cells that give rise to plastic-adherent CFU-Fs. To better understand the in vivo functions and translational therapeutic potential of hDPSCs and other stem cells, selective cell markers must be identified in the progenitor cells. Here, we identified a dental pulp tissue-specific cell population based on the expression profiles of 2 cell-surface markers LNGFR (CD271) and THY-1 (CD90). Prospectively isolated, dental pulp-derived LNGFR(Low+)THY-1(High+) cells represent a highly enriched population of clonogenic cells--notably, the isolated cells exhibited long-term proliferation and multilineage differentiation potential in vitro. The cells also expressed known mesenchymal cell markers and promoted new bone formation to heal critical-size calvarial defects in vivo. These findings suggest that LNGFR(Low+)THY-1(High+) dental pulp-derived cells provide an excellent source of material for bone regenerative strategies. [ABSTRACT FROM AUTHOR]

Published
2016
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41. Dietary diacylglycerol suppresses accumulation of body fat compared to triacylglycerol in men in a double-blind controlled trial.

Author

Nagao, Tomonori, Watanabe, Hiroyuki, Nagao, T, Watanabe, H, Goto, N, Onizawa, K, Taguchi, H, Matsuo, N, Yasukawa, T, Tsushima, R, Shimasaki, H, and Itakura, H

Subjects
LIPID metabolism, OBESITY, HEALTH, LIVER, ABDOMEN, ADIPOSE tissues, CLINICAL trials, COMPARATIVE studies, DIET, GLYCERIDES, INGESTION, HUMAN constitution, RESEARCH methodology, MEDICAL cooperation, RESEARCH, TRIGLYCERIDES, EVALUATION research, RANDOMIZED controlled trials, BLIND experiment, ANATOMY
Abstract

We examined the effects of the long-term ingestion of dietary diacylglycerols (DG) in a double-blind controlled study of human lipid metabolism. Healthy men (n = 38; aged from 27 to 49 y, body mass index (BMI) ranging from 21.8 to 27.4 kg/m(2)) completed the study. To accustom the subjects to the test diets prior to the experiment, they were supplied with test diets of triacylglycerol (TG) oil for 4 wk (control period). The test oils (10 g/d) were included in bread, mayonnaise or shortbread and served for the breakfast. The target for total lipid intake was 50 g/d (15 g for breakfast, 15 g for lunch and 20 g for dinner) throughout the study. The subjects were then divided into two groups so that mean BMI and the hepatic fat content, determined by computed tomography, for each group were not different. One group (DG group) consumed test meals containing DG-rich oil (10 g/d) while the other group (TG group) consumed the same meal as during the control period. Ten grams of the DG-rich oil contained 5.5 g 1,3-DG, 2.5 g 1,2-DG and 2 g TG. The actual lipid intake during the study was 43 g/d. Body weight, BMI and waist circumference decreased in both groups at the end of the test period of 16 wk. However, the magnitudes of decreases in these variables were significantly greater in the DG group than in the TG group. Decreases of total fat, visceral fat area and subcutaneous fat area of the abdominal traverse images of computed tomography in the DG group were also significantly greater than those in the TG group. Hepatic fat content decreased significantly in the DG group while no change was observed in the TG group. Serum lipid concentrations (TG, total cholesterol, free fatty acid) and related metabolites (glucose, insulin, total ketone body) did not change significantly in either group. Thus, in contrast to TG, DG apparently suppressed accumulation of fat and possibly reduces the risk of diseases associated with visceral fat obesity. [ABSTRACT FROM AUTHOR]

Published
2000
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42. Dietary diacylglycerol suppresses high fat and high sucrose diet-induced body fat accumulation in C57BL/6J mice.

Author

Murase, T, Mizuno, T, Omachi, T, Onizawa, K, Komine, Y, Kondo, H, Hase, T, and Tokimitsu, I

Abstract

Diacylglycerol (DG) comprises up to approximately 10% of various edible oils. In the present study, we examined the effects of dietary DG consisting mainly of 1,3-species on body weight, body fat accumulation, and mRNA levels of various genes involved in energy homeostasis in obesity-prone C57BL/6J mice. Five-month feeding with the high triacylglycerol (TG) diet (30% TG + 13% sucrose) resulted in significant increases in body weight, visceral fat accumulation, and circulating insulin and leptin levels compared with mice fed the control diet (5% TG). Compared with mice fed the high TG diet, body weight gain and visceral fat weight were reduced by 70% and 79%, respectively, in those fed the high DG diet (30% DG + 13% sucrose). In addition, circulating leptin and insulin levels were reduced to the respective control levels. Compared with high TG feeding, high DG feeding suppressed the elevation of leptin mRNA expression in adipose tissue, and up-regulated acyl-coenzyme (Co)A oxidase and acyl-CoA synthase mRNA expression in the liver. These results indicate that dietary DG is beneficial for suppression of high fat diet-induced body fat accumulation. Furthermore, it is suggested that structural differences in DG and TG, but not the composition of fatty acid, markedly affect nutritional behavior of lipids. -- Murase, T., T. Mizuno, T. Omachi, K. Onizawa, Y. Komine, H. Kondo, T. Hase, and I. Tokimitsu. Dietary diacylglycerol suppresses high fat and high sucrose diet-induced body fat accumulation in C57BL/6J mice. J. Lipid Res. 2001. 42: 372--378.

Published
2001

44. Chromatic analysis of autofluorescence emitted from squamous cell carcinomas arising in the oral cavity: a preliminary study

Author

Onizawa, K., Yoshida, H., and Saginoya, H.

Abstract

Chromatic analysis was carried out to characterize the color quality of autofluorescence emitted from oral squamous cell carcinomas (SCC) and to objectively compare autofluorescence among various tissues. The following specimens were studied: 33 SCC, 3 epithelial dysplasias, 39 benign lesions, 31 dorsa of the tongue and 18 dental plaques. Autofluorescence depicted on fluorescence photographs was measured with a chroma meter. Chromatic values of autofluorescence differed significantly between SCC and non-cancerous tissues and between different stages of SCC. Autofluorescence of SCC tended to shift from orange to reddish orange with advancement of stage. These results suggest that autofluorescence of oral SCC chromatically differs from that of other tissues and depends on the stage of cancer.

Published
2000
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47. Flexure deformation of the temporomandibular joint disk in pseudodynamic magnetic resonance images

Author

Yoshida, H., Hirohata, H., Onizawa, K., Niitsu, M., and Itai, Y.

Abstract

Objective.: The purpose of this study was to determine correlation of flexure disk deformation during jaw movement with other findings on magnetic resonance images and with clinical signs and symptoms in patients with anterior displacement of the temporomandibular joint disk. Study design.: T"1-weighted magnetic resonance images and gradient recalled acquisition in steady state magnetic resonance images were obtained in 62 subjects with flexure deformed disk in the jaw opening phase. Each disk deformation observed on a pseudodynamic image during jaw opening was classified as an upward or downward flexure deformation. The relationships between type of disk deformation, clinical signs and symptoms, and other findings on the magnetic resonance images were statistically analyzed by x^2 test. Results.: Of 80 delineated joints, 30 showed upward deformation and 50 showed downward deformation. There were significant differences between the upward and downward deformations in TMJ sound, TMJ pain, restricted jaw opening, extent of anterior displacement, and presence of disk reduction. Conclusions.: The type of disk deformation appeared to correlate with the clinical signs and symptoms and with the progress of internal derangement.

Published
2000
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