166 research outputs found
Incident angle dependence of reactions between graphene and hydrogen atom by molecular dynamics simulation
Incident angle dependence of reactions between graphene and hydrogen atoms
are obtained qualitatively by classical molecular dynamics simulation under the
NVE condition with modified Brenner reactive empirical bond order (REBO)
potential. Chemical reaction depends on two parameters, i.e., polar angle
and azimuthal angle of the incident hydrogen. From the
simulation results, it is found that the reaction rates strongly depend on
polar angle . Reflection rate becomes larger with increasing ,
and the dependence of adsorption rate is also found. The
dependence is caused by three dimensional structure of the small potential
barrier which covers adsorption sites. dependence of penetration rate is
also found for large .Comment: 4 pages, 7 figure
Hybrid Simulation between Molecular Dynamics and Binary Collision Approximation Codes for Hydrogen injection onto Carbon Materials
Molecular dynamics (MD) simulation with modified Brenner's reactive empirical
bond order (REBO) potential is a powerful tool to investigate plasma wall
interaction on divertor plates in a nuclear fusion device. However, MD
simulation box's size is less than several nm for the performance of a
computer. To extend the size of the MD simulation, we develop a hybrid
simulation code between MD code using REBO potential and binary collision
approximation (BCA) code. Using the BCA code instead of computing all particles
with a high kinetic energy for every step in the MD simulation, considerable
computation time is saved. By demonstrating a hydrogen atom injection on a
graphite by the hybrid simulation code, it is found that the hybrid simulation
code works efficiently in a large simulation box.Comment: 5 pages, 5 figure
Highly Invasive Intracranial Malignant Schwannoma in a Rat
A highly invasive intracranial malignant schwannoma containing several masses was detected in a 28-week-old male Crl:CD(SD) rat. Macroscopically, 3 masses were noted in the cranial cavity; one was present at the bottom of the cranial cavity and involved the trigeminal nerve, and the other two were in the parietal bone. Histologically, each mass consisted of fusiform cells with interlacing fascicular, wavy and nuclear pseudopalisading arrangements and round cells with cystic lesions. The tumor cells invaded not only the brain but also the parietal bone. In the brain, the tumor cells infiltrated diffusely into the leptomeningeal and perivascular spaces and parenchyma, in which the tumor cell morphology and invasive pattern closely resembled those of malignant astrocytoma and malignant reticulosis. Immunohistochemically, the tumor cells in the masses showed positive reactions for both S-100 protein and GFAP, while those in the cerebral invasion sites were negative for GFAP and less positive for S-100 protein. Electron microscopically, a single basal lamina layer and short intricate cell processes were confirmed in the tumor cells. From these results, the present tumor was diagnosed as a malignant schwannoma arising in the cranial cavity, probably originating from the trigeminal nerve. The present tumor is considered to be a relatively unique malignant schwannoma based on its growth and invasion patterns
小特集:磁場閉じ込め核融合装置における水素原子分子輸送研究の新展開 2.要素モデルの統合が実現する壁から プラズマまでを含めた中性粒子輸送研究
非接触をはじめとするダイバータプラズマの諸現象を理解するため,壁での粒子リサイクリング,荷電粒子,中性粒子を扱うコードの統合を進めている.水素分子には,電子状態のほか,回転および振動の内部自由度があり,分子活性化再結合をはじめとするプラズマ中の水素分子の各種の反応速度係数は,水素分子の始状態の振動・回転量子数により,数桁にわたって変化する.また,低温のプラズマでは,プラズマ中の電子やプロトン衝突による水素分子の振動・回転励起がプラズマのエネルギー損失チャンネルとして重要と考えられる.このため,水素分子の振動・回転状態を中性粒子やプラズマの輸送と組み合わせて解く統合モデルを開発した
Molecular Dynamics Simulation of Chemical Vapor Deposition of Amorphous Carbon: Dependence on H/C Ratio of Source Gas
By molecular dynamics simulation, the chemical vapor deposition of amorphous
carbon onto graphite and diamond surfaces was studied. In particular, we
investigated the effect of source H/C ratio, which is the ratio of the number
of hydrogen atoms to the number of carbon atoms in a source gas, on the
deposition process. In the present simulation, the following two source gas
conditions were tested: one was that the source gas was injected as isolated
carbon and hydrogen atoms, and the other was that the source gas was injected
as hydrocarbon molecules. Under the former condition, we found that as the
source H/C ratio increases, the deposition rate of carbon atoms decreases
exponentially. This exponential decrease in the deposition rate with increasing
source H/C ratio agrees with experimental data. However, under the latter
molecular source condition, the deposition rate did not decrease exponentially
because of a chemical reaction peculiar to the type of hydrocarbon in the
source gas.Comment: accepted by Jpn. J. Appl. Phys. (2008
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