Chemical Effects on Kβ/Kα X-Ray Intensity Ratio for 97mTc and 95mTc

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Two evolutional paths of an axisymmetric gravitational instability in the dust layer of a protoplanetary disk

Nonlinear numerical simulations are performed to investigate the density evolution in the dust layer of a protoplanetary disk due to the gravitational instability and dust settling toward the midplane. We assume the region where the radial pressure gradient at equilibrium is negligible so that the shear-induced instability is avoided, and also restrict to an axisymmetric perturbation as a first step of nonlinear numerical simulations of the gravitational instability. We find that there are two different evolutional paths of the gravitational instability depending on the nondimensional gas friction time, which is defined as the product of the gas friction time and the Keplerian angular velocity. If the nondimensional gas friction time is equal to 0.01, the gravitational instability grows faster than dust settling. On the other hand, if the nondimensional gas friction time is equal to 0.1, dust aggregates settle sufficiently before the gravitational instability grows. In the latter case, an approximate analytical calculation reveals that dust settling is faster than the growth of the gravitational instability regardless of the dust density at the midplane. Thus, the dust layer becomes extremely thin and may reach a few tenth of the material density of the dust before the gravitational instability grows.Comment: 4 pages, 3 figure

Intracranial extension of adenoid cystic carcinoma: potential involvement of EphA2 expression and epithelial-mesenchymal transition in tumor metastasis: a case report

BACKGROUND: Adenoid cystic carcinoma is a malignant epithelial tumor derived from salivary glands and tends to invade the surrounding structures including nervous system. We present a case of adenoid cystic carcinoma with intracranial extension and propose a novel molecular mechanism of adenoid cystic carcinoma metastasis. CASE PRESENTATION: A 29-year-old Japanese male presented with left trigeminal nerve disturbance. Neuroimaging revealed a tumor located at the right middle cranial and infratemporal fossa. The tumor was removed via a subtemporal extradural and infratemporal fossa approach and histologically diagnosed as adenoid cystic carcinoma. Radiological and operative findings confirmed a perineural spread of the tumor along the mandibular nerve. Immunohistochemical analyses of molecular consequences in this case were performed for better understanding of the biological processes associated with adenoid cystic carcinoma metastasis. First, the neoplastic cells were not immunoreactive for E-cadherin, an epithelial marker, but for vimentin, a mesenchymal marker, suggesting changes in cell phenotype from epithelial to mesenchymal states. Correspondingly, immunoreactivity of transcriptional factors, such as Slug, Twist, matrix metalloproteinase-2 and -9, which are involved in epithelial–mesenchymal transition, were observed. Second, elevated expression of EphA2 receptor, not ephrin-A1, was notable in the neoplastic cells, suggesting morphological changes reminiscent of epithelial–mesenchymal transition and ligand-independent promotion of tumor cell migration and invasion. CONCLUSIONS: We report a case of adenoid cystic carcinoma with perineural spread and provide the first published evidence that EphA2 expression without ephrin-A1 and epithelial–mesenchymal transition might play important roles in adenoid cystic carcinoma progression

N-Body Simulation of Planetesimal Formation through Gravitational Instability of a Dust Layer in Laminar Gas Disk

We investigate the formation process of planetesimals from the dust layer by the gravitational instability in the gas disk using local $N$-body simulations. The gas is modeled as a background laminar flow. We study the formation process of planetesimals and its dependence on the strength of the gas drag. Our simulation results show that the formation process is divided into three stages qualitatively: the formation of wake-like density structures, the creation of planetesimal seeds, and their collisional growth. The linear analysis of the dissipative gravitational instability shows that the dust layer is secularly unstable although Toomre's $Q$ value is larger than unity. However, in the initial stage, the growth time of the gravitational instability is longer than that of the dust sedimentation and the decrease in the velocity dispersion. Thus, the velocity dispersion decreases and the disk shrinks vertically. As the velocity dispersion becomes sufficiently small, the gravitational instability finally becomes dominant. Then wake-like density structures are formed by the gravitational instability. These structures fragment into planetesimal seeds. The seeds grow rapidly owing to mutual collisions.Comment: 32 pages, 11 figures, accepted for publication in Ap

Processing and adsorption control in ZnO single nanowire photodetectors

ZnO single nanowire photodetectors have been measured in different ambient conditions in order to understand and control adsorption processes on the surface. A decrease in the conductivity has been observed as a function of time when the nanowires are exposed to air, due to adsorbed O2/H2O species at the nanowire surface. In order to have a device with stable characteristics in time, thermal desorption has been used to recover the original conductivity followed by PMMA coating of the exposed nanowire surface

Secular Gravitational Instability of a Dust Layer in Shear Turbulence

We perform a linear stability analysis of a dust layer in a turbulent gas disk. Youdin (2011) investigated the secular gravitational instability of a dust layer using hydrodynamic equations with a turbulent diffusion term. We obtain essentially the same result independently of Youdin (2011). In the present analysis, we restrict the area of interest to small dust particles, while investigating the secular gravitational instability in a more rigorous manner. We discuss the time evolution of the dust surface density distribution using a stochastic model and derive the advection-diffusion equation. The validity of the analysis by Youdin (2011) is confirmed in the strong drag limit. We demonstrate quantitatively that the finite thickness of a dust layer weakens the secular gravitational instability and that the density-dependent diffusion coefficient changes the growth rate. We apply the obtained results to the turbulence driven by the shear instability and find that the secular gravitational instability is faster than the radial drift when the gas density is three times as large as that in the minimum-mass disk model. If the dust particles are larger than chondrules, the secular gravitational instability grows within the lifetime of a protoplanetary disk.Comment: 32 pages, 6 figures, accepted for publication in Ap

海外の大学が提供する遠隔授業への日本人学生の参加に関する成果と課題

This paper is a report on the online student exchange program between Osaka University and University of Hawai'i at Manoa in the USA, and Osaka University and Ateneo de Manila University in the Philippines. Specifically, it focuses on the achievements and challenges on the participation of the Osaka University students enrolled in the said online student exchange program. Evaluation of the exchange program is based on questionnaires submitted by the students, final presentation containing narratives of students about the program, and experiences of professors involved. The OU students expressed that the program mainly helped in the following points: it let them have an opportunity to exchange with the students in other countries and have a wider view on things, and it helped and motivated them to study English, Filipino and the other classes in OU. The program showed accomplishment and results not only in the learning of the students but also the significance and benefits of international exchange between the faculty members of Ateneo de Manila University, University of Hawai'i at Mānoa and Osaka University.本稿は大阪大学と、フィリピン共和国のアテネオ・デ・マニラ大学およびアメリカ合衆国のハワイ大学マノア校との間で実施されたオンライン交流プログラムについて報告したものである。具体的には、大阪大学の学生の参加に関する成呆と課題に焦点を当て、アンケートヘの学生の同答、プログラムの体験談を含む学生の最終報告、プログラムに携わった教員らの経験に基づいて評価を実施した。本プログラムが役立ったと学生が考えている主な点は、他国の学生と交流する機会が得られ、視野を広げられたこと、および、大阪大学における英語やフィリピン語、その他の授業の学習の動機付けとなったことである。学生の学習に関する成果や効果のみならず、アテネオ・デ・マニラ大学およびハワイ大学マノア校と大阪大学の教員間交流に関する意義や有益性も明らかとなった。教育実践報

High Velocity Dust Collisions: Forming Planetesimals in a Fragmentation Cascade with Final Accretion

In laboratory experiments we determine the mass gain and loss in central collisions between cm to dm-size SiO2 dust targets and sub-mm to cm-size SiO2 dust projectiles of varying mass, size, shape, and at different collision velocities up to ~56.5 m/s. Dust projectiles much larger than 1 mm lead to a small amount of erosion of the target but decimetre targets do not break up. Collisions produce ejecta which are smaller than the incoming projectile. Projectiles smaller than 1 mm are accreted by a target even at the highest collision velocities. This implies that net accretion of decimetre and larger bodies is possible. Independent of the original size of a projectile considered, after several collisions all fragments will be of sub-mm size which might then be (re)-accreted in the next collision with a larger body. The experimental data suggest that collisional growth through fragmentation and reaccretion is a viable mechanism to form planetesimals

フィリピンゴ ガクシュウヨウ オンライン コンテンツ ノ ガイカン オンライン ジショ E ラーニング キョウザイ デンシ ショセキ サイト ニ チャクモク シテ

This article aims to survey free online contents used for Filipino language learning to be able to give an overview on what are provided in each of them. As printed materials that are explained in Japanese are limited, these online contents are of great value for both teachers and learners involved in Filipino language education in Japan. This article examines four online dictionaries, five e-learning materials and three e-book contents. The contents are analyzed from the point of view of what learners are able to study by using these contents in accordance with framework that is appropriate for textbook analysis. If learners are able to utilize them in an effective way, they may also be able to learn Philippine history, social issues, values and so on in addition to the language elements like correct pronunciation, vocabulary, expressions, structures of sentences and writing styles. On the other hand, there are also some issues noted which are as follows: 1) As some contents have limited information, it is necessary to make up for this limitation by, for example, using them in combination with other contents or printed materials and dictionaries. 2) It is seen important for learners to be aware of the system of the contents or for teachers to guide learners appropriately because it may be difficult for learners to overview the contents as a whole unlike in the case of printed materials. 3) Improving the contents for Japanese speakers is also necessary.教材研