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Search Results: 1 - 10 of 2082 matches for " Tetsuya Hara "
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Quest for Potentials in the Quintessence Scenario  [PDF]
Tetsuya Hara
Journal of Applied Mathematics and Physics (JAMP) , 2016, DOI: 10.4236/jamp.2016.42027
Abstract:

The time evolution of the equation of state w for quintessence scenario with a scalar field as dark energy is studied up to the third derivative (d3w/da3) with respect to the scale factor a, in order to predict the future observations and specify the scalar potential parameters with the observables. The third derivative of w for general potential V is derived and applied to several types of potentials. They are the inverse power-law (V = M4 + α/Qα), the exponential ?\"\", the mixed \"\" , the cosine \"\" ?and the Gaussian types \"\" , which are prototypical potentials for the freezing and thawing models. If the parameter number for a potential form is n, it is necessary to find at least for n + 2 independent observations to identify the potential for0m and the evolution of the scalar field (Q and \"\"

Transfer of Life-Bearing Meteorites from Earth to Other Planets
Tetsuya Hara,Kazuma Takagi,Daigo Kajiura
Physics , 2012,
Abstract: The probability is investigated that the meteorites originating on Earth are transferred to other planets in our Solar System and to extra solar planets. We take the collisional Chicxulub crater event, and material that was ejected as an example of Earth-origin meteors. If we assume the appropriate size of the meteorites as 1cm in diameter, the number of meteorites to reach the exoplanet system (further than 20 ly) would be much greater than one. We have followed the ejection and capture rates estimated by Melosh (2003) and the discussion by Wallis and Wickramasinghe (2004). If we consider the possibility that the fragmented ejecta (smaller than 1cm) are accreted to comets and other icy bodies, then buried fertile material could make the interstellar journey throughout Galaxy. If life forms inside remain viable, this would be evidence of life from Earth seeding other planets. We also estimate the transfer velocity of the micro-organisms in the interstellar space. In some assumptions, it could be estimated that, if life has originated $10^{10}$\ years ago anywhere in our Galaxy as theorized by Joseph and Schild (2010a, b), it will have since propagated throughout our Galaxy and could have arrived on Earth by 4.6 billion years ago. Organisms disperse.
Adopting the Uncertainty Principle for the Entropy Estimation of Black Holes, de Sitter Space and Rindler Space
Tetsuya Hara,Keita Sakai,Daigo Kajiura
Physics , 2006,
Abstract: By a simple physical consideration and uncertain principle, we derive that temperature is proportional to the surface gravity and entropy is proportional to the surface area of the black hole. We apply the same consideration to de Sitter space and estimate the temperature and entropy of the space, then we deduce that the entropy is proportional to the boundary surface area. By the same consideration, we estimate the temperature and entropy in the uniformly accelerated system (Rindler coordinate). The cases in higher dimensions are considered.
On the Entropy Increase in the Black Hole Formation
Tetsuya Hara,Keita Sakai,Daigo Kajiura
Physics , 2005,
Abstract: The entropy increases enormously when a star collapses into a black hole. This entropy increase is interpreted as the decrease of the temperature due to the increase of the volume. Through these investigation the microscopic states of the black hole entropy is naturally understood as the statistical states of the enlarged phase space.
Comparison of Efficacy and Safety Evaluation of Latanoprost Formulations with and without Benzalkonium Chloride  [PDF]
Hiroyoshi Kasai, Yumiko Aoyama, Takashi Kurasawa, Tomoyo Imamura, Kazuhiro Tsuruma, Hideaki Hara, Haruhisa Hirata, Tetsuya Yamamoto
Pharmacology & Pharmacy (PP) , 2013, DOI: 10.4236/pp.2013.44054
Abstract:

Background: This study investigated the safety (cytotoxicity in vitro) and pharmacological effects (ocular hypotensive effects and aqueous humor concentrations in normotensive monkeys in vivo) of latanoprost formulations with benzalkonium chloride (latanoprost with BAK) and without BAK (NP). Methods: A bioequivalence study of latanoprost with BAK and NP was also conducted on human healthy volunteers. Cytotoxicity and the protective effect against H2O2 stress in vitro were evaluated using human corneal epithelial cells. The ocular hypotensive effects in normotensive monkeys were measured by pneumatonometer and the aqueous humor concentrations of latanoprost free acid were determined by liquid chromatography/mass spectrum (LC/MS) methods. The bioequivalence study of latanoprost with BAK and NP was carried out as a single eye drop, two-sequence, crossover randomized study. Results: Cytotoxicity tests in vitro revealed that NP was less toxic than latanoprost with BAK and significantly inhibited H2O2 induced cell damage while latanoprost with BAK did not. The hypotensive efficacy and the latanoprost free acid concentrations in aqueous humor of each formulation were not significantly different in monkeys. In the bioequivalence study, NP was bioequivalent to latanoprost with BAK. NP was safer than latanoprost with BAK with respect the results obtained in the in vitro cytotoxicity test. There was no difference observed between latanoprost with BAK and NP in the IOP lowering effect in monkeys and healthy volunteers.

Gefitinib, an epidermal growth factor receptor blockade agent, shows additional or synergistic effects on the radiosensitivity of esophageal cancer cells in vitro.
Taira,Naruto,Doihara,Hiroyoshi,Oota,Tetsuya,Hara,Fumikata
Acta Medica Okayama , 2006,
Abstract: Human esophageal cancers have been shown to express high levels of epidermal growth factor receptor (EGFR) and a relationship between high EGFR expression and local advance, the number of lymph node metastases, life expectancy, and sensitivity to chemo-radiotherapy has been demonstrated. We examined the use of gefitinib, an orally active EGFR-selective tyrosine kinase inhibitor, as a new strategy for treatment of esophageal carcinoma. The effects of gefitinib were evaluated in monotherapy and in combination with radiotherapy in human esophageal carcinoma cell lines. Gefitinib produced a dose-dependent inhibition of cellular proliferation in all of the 8 esophageal carcinoma cell lines examined, with IC50 values ranging from 5.7 microM to 36.9 microM. In combination, gefitinib and radiotherapy showed a synergistic effect in 2 human esophageal carcinoma cell lines and an additive effect in 5 cell lines. Western blotting demonstrated that gefitinib blocked activation of the EGFR-extracellular signal-regulated kinase (Erk) pathway and the EGFR-phosphoinositide-3 kinase (PI3K)-Akt pathway after irradiation. These results suggest that further evaluation of EGFR blockade as a treatment for esophageal cancer should be performed, and that radiotherapy combined with EGFR blockade may enhance the response of esophageal carcinoma to therapy.
On the Formation Age of the First Planetary System
Tetsuya Hara,Shuhei Kunitomo,Masanobu Shigeyasu,Daigo Kajiura
Physics , 2012, DOI: 10.1017/S1743921308016785
Abstract: Recently, it has been observed the extreme metal-poor stars in the Galactic halo, which must be formed just after Pop III objects. On the other hand, the first gas clouds of mass $\sim 10^6 M_{\odot}$ are supposed to be formed at $ z \sim $ 10, 20, and 30 for the $1\sigma$, $2\sigma $ and $3\sigma$, where the density perturbations are assumed of the standard $\Lambda$CDM cosmology. If we could apply this gaussian distribution to the extreme small probability, the gas clouds would be formed at $ z \sim $40, 60, and 80 for the $4\sigma$, $6\sigma$, and $8\sigma$. The first gas clouds within our galaxy must be formed around $z\sim 40$. Even if the gas cloud is metal poor, there is a lot of possibility to form the planets around such stars. The first planetary systems could be formed within $\sim 6\times 10^7$ years after the Big Bang in the universe. Even in our galaxies, it could be formed within $\sim 1.7\times 10^8$ years. It is interesting to wait the observations of planets around metal-poor stars. For the panspermia theory, the origin of life could be expected in such systems.
A giant plexiform schwannoma of the brachial plexus: case report
Sho Kohyama, Yuki Hara, Yasumasa Nishiura, Tetsuya Hara, Tanefumi Nakagawa, Naoyuki Ochiai
Journal of Brachial Plexus and Peripheral Nerve Injury , 2011, DOI: 10.1186/1749-7221-6-9
Abstract: Plexiform Schwannoma is a rare variant of Schwannoma that accounts for only 5% of all Schwannomas, which typically shows a plexiform or multinodular growth pattern mimics plexiform neurofibroma. It was first described by Harkin and Reed in 1978 [1]. Plexiform Schwannoma usually develops in the dermis or subcutaneous tissue, and it is uncommon for the Schwannoma to develop in deep-seated nerves. Its histological features include Antoni A and B areas, diffuse and strong positivity with immunohistochemical markers like S-100, laminin and collagen type IV.On the other hand, plexiform neurofibroma lacks Antoni A and B areas of schwannoma and shows weak S-100 positivity. Plexiform schwannoma shows up to 5% association with neurofibromatosis-2 and schwannomatosis, but has no association with neurofibromatosis-1 like plexiform neurofibroma [2,3]. This report describes the rare case of a giant plexiform Schwannoma in the brachial plexus.The patient was a 64-year-old male. More than 30 years earlier, he had experienced numbness in his left upper extremity. By his own account, he had undergone surgery and was diagnosed with a brachial plexus tumor. He stopped visiting the hospital after the surgery, no records of the surgery remain and the details thereof are unknown. The patient was diagnosed with diabetes mellitus 2 years earlier. He had no family history of a similar tumor. The patient noticed muscle weakness in his left arm 5 years earlier, but never visited a medical facility. Thereafter, the muscle weakness worsened, and he finally visited a local doctor 2 years earlier. His upper extremity was far from functional, and so he was referred to our hospital for further examination and treatment.On examination a biloculate mass was observed in the left supraclavicular area, and Tinel's sign caused paraesthesia in his left arm. There was no evidence of the other tumor anywhere on his body. We found no café-au-lait spots or other signs of Recklinghausen disease neither.Manual m
Clinical and immunohistochemical study of eight cases with thymic carcinoma
Masaki Tomita, Yasunori Matsuzaki, Masao Edagawa, Masayuki Maeda, Tetsuya Shimizu, Masaki Hara, Toshio Onitsuka
BMC Surgery , 2002, DOI: 10.1186/1471-2482-2-3
Abstract: There were 2 men and 6 women: ages ranged from 19 to 67 years old (mean 54.8 years). None of these patients had concomitant myasthenia gravis and pure red cell aplasia. No patient had stage I disease, 1 stage II, 5 stage III, and 2 stage IV. The pathologic subtypes of thymic carcinoma included 5 squamous cell carcinomas, 1 adenosquamous cell carcinomas, 1 clear cell carcinoma, and 1 small cell carcinoma. Immunohistochemical study was performed using antibodies against p53, bcl-2, Ki-67, carcinoembryonic antigen (CEA), epithelial membrane antigen (EMA), nm23-H1, vascular endothelial growth factor (VEGF), basic fibroblast growth factor (FGF-2) and factor VIII.Curative resection could be done in 4 patients (50%). Our data indicates a trend toward an association between complete resection and patient survival. Expression of p53, bcl-2, CEA, EMA, nm23-H1, VEGF and FGF-2 was detected in 5/8, 3/8, 4/8, 5/8, 6/8, 5/8 and 3/8, respectively. Mean Ki-67 labeling index and microvessel density was 7.01 and 34.36 (per 200× field), respectively. When compared with our previous studies, immunohistochemical staining of these proteins in thymomas, the expression rates of these proteins in thymic carcinomas were higher than those in thymomas.In this small series, it is suggested that a complete resection suggests a favorable result. Immunohistochemical results reveal that the expression of these proteins might indicate the aggressiveness of thymic carcinoma.Thymic carcinoma is a rare type of malignant tumor [1,2]. It is more invasive and with a poorer prognosis than ordinary thymoma [3-8]. At diagnosis, it is usually invasive or metastatic and complete curative resection is sometimes not possible to achieve. There are no uniform management protocols and thymic carcinoma is treated by the same guidelines used for thymomas, despite having a more aggressive histologic appearance and clinical outcome [6-8].In addition, in spite of numerous previous studies about expression of oncogene pro
Hyperglycemia raises the threshold of levosimendan- but not milrinone-induced postconditioning in rat hearts
Shuhei Matsumoto, Sungsam Cho, Shinya Tosaka, Ushio Higashijima, Takuji Maekawa, Tetsuya Hara, Koji Sumikawa
Cardiovascular Diabetology , 2012, DOI: 10.1186/1475-2840-11-4
Abstract: Wistar rats underwent 30-min coronary artery occlusion followed by 2-h reperfusion. The rats received milrinone or levosimendan just before reperfusion under normoglycemic or hyperglycemic conditions with or without atractyloside, an mPTP opener.Under normoglycemia, both 30 μg/kg milrinone (29 ± 12%) and 10 μg/kg levosimendan (33 ± 13%) reduced infarct size compared with that in the control (58 ± 7%). Under hyperglycemia, milrinone (34 ± 13%) reduced infarct size at the same dose as under normoglycemia. In contrast, neither 10 nor 30 μg/kg levosimendan protected hyperglycemic hearts, and only 100 μg/kg levosimendan (32 ± 9%) reduced infarct size compared with that in the hyperglycemic control (58 ± 13%). All of these cardioprotective effects under normoglycemia and hyperglycemia are abolished by atractyloside.Milrinone and levosimendan exert postconditioning effects via inhibition of mPTP opening. Hyperglycemia raises the threshold of levosimendan-induced postconditioning, while milrinone-induced postconditioning is not influenced by hyperglycemia.Hyperglycemia (HG) is frequently observed in patients with acute myocardial ischemic events such as myocardial infarction or the usage of cardiopulmonary bypass in cardiac surgery. Many studies have demonstrated the association between HG and increased mortality after acute myocardial infarction [1]. One possible cause of high mortality may be poor cardioprotective strategies under HG. HG was shown to abolish cardioprotection induced by ischemic and pharmacological preconditioning (PreC) [2,3]. Postconditioning (PostC) is more likely than PreC to be feasible as a clinical application, and may be useful in unpredictable myocardial ischemia-reperfusion injury. It was also reported that HG abolished both ischemic and pharmacological PostC [4-6]. To save the ischemic myocardium exposed to HG environment, it is essential to investigate the effective PostC maneuver under HG.Milrinone, a phosphodiesterase 3 inhibitor (PDE-I), and
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