- 著者
- Takeshi Miyamoto Eri Katsuyama Hiroya Kanagawa Atsuhiro Fujie Hiroya Miyamoto Shigeyuki Yoshida Tomoaki Mori Kana Miyamoto Yuiko Sato Tami Kobayashi Masaya Nakamura Morio Matsumoto Yuji Nishiwaki Hiroshi Hirose Takeshi Kanda Ikuo Saito Yoshiaki Toyama
- 出版者
- The Keio Journal of Medicine
- 雑誌
- The Keio Journal of Medicine (ISSN:00229717)
- 巻号頁・発行日
- vol.65, no.2, pp.33-38, 2016 (Released:2016-06-25)
- 参考文献数
- 24
- 被引用文献数
- 11 13
Low serum 25-hydroxyvitamin D (25(OH)D) levels are implicated as a risk factor for hip and spine fractures. Studies of the relation between 25(OH)D levels and fractures have primarily involved elderly osteoporosis patients or patients with fractures; however, the serum 25(OH)D and parathyroid hormone (PTH) status in younger adult populations remains largely unknown. We evaluated serum 25(OH)D and intact PTH levels in 411 women aged 39–64 years who were not receiving medication for osteoporosis or other bone diseases. Serum 25(OH)D levels were positively correlated with age (P = 0.019), whereas intact PTH levels were inversely correlated with 25(OH)D levels (P < 0.001). Thus, low vitamin D levels with high intact PTH levels were more common in younger than in older women. Our data show that serum 25(OH)D insufficiency could be a more serious concern in the younger population than had been previously anticipated. Because serum 25(OH)D insufficiency is reportedly a risk factor for hip and spine fracture, the number of fracture patients could increase in the future, suggesting that we may need to correct the serum vitamin D/intact PTH status to prevent future osteoporosis.
- 著者
- Takeshi KANDA Masaki SATO Toshiya KIMURA Hiroya ASAKAWA
- 出版者
- THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES
- 雑誌
- TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES (ISSN:05493811)
- 巻号頁・発行日
- vol.61, no.3, pp.106-118, 2018 (Released:2018-05-04)
- 参考文献数
- 37
- 被引用文献数
- 5 5
This paper describes the characteristics of methane-fueled rocket engines and compares these characteristics with those of hydrogen-fueled engines in terms of both expander and coolant-bleed cycles. Methane vaporizes in a cooling jacket under low-pressure operating conditions, whereas it liquefies in the turbine in the coolant-bleed cycle. The thermodynamic property of methane limits the operating range of methane-fueled engines. When the coolant-bleed cycle is used, the specific impulse degradation of methane-fueled engines becomes larger compared to that of hydrogen-fueled engines. This is due to methane having a lower specific heat and temperature after regenerative cooling. Even though the heat absorbing ability of methane is much lower than that of hydrogen, methane-fueled engines can operate with higher chamber pressures using the expander cycle. This is due to the larger density and the higher temperature after the regenerative cooling of liquid methane. Throttling of the methane-fueled engines does not have a great impact on the pump exit pressure in the expander cycle, whereas it increases the bleed ratio and degrades the specific impulse in the coolant bleed cycle of methane-fueled engines.