504 research outputs found
Nucleon mean free path in nuclear matter based on nuclear Schwinger-Dyson formalism
A mean free path of nucleon moving through nuclear matter with kinetic energy
of more than 100MeV is formulated based on the bare vertex nuclear
Schwinger-Dyson (BNSD) method in the Walecka model. The self-energy which is
derived from the higher order diagrams more than the forth order includes the
Feynman part of propagator of energetic nucleon and grows up rapidly as an
increase of kinetic energy. To avoid too large growth of these diagrams, meson
propagators are modified by introducing some form factors to take account of a
internal structure of hadron. It is confirmed that the mean free path
calculated by the BNSD method agrees good with experimental data if a
reasonable form factor is chosen, i.e., a dipole (quadrupole) type of form
factor with a cut-off parameter about 750 MeV 1000 MeV (1200 MeV
1500 MeV)
Vacuum Effects and Compressional Properties of Nuclear Matter in Cutoff Field Theory
Including the vacuum effects, the compressional properties of nuclear matter
are studied in the cutoff field theory. Under the Hartree approximation, the
low-energy effective Lagrangian is derived in the framework of the
renormalization group methods. The coefficients are determined in a way where
the physical results hardly depend on the value of the cutoff which is
conveniently introduced into the theory. It is shown that, to reproduce the
empirical data of the nucleus incompressibility, the compressibility of the
nuclear matter is favorable to be 250350MeV.Comment: PACS numbers, 21.65.+
Intersubband absorption linewidth in GaAs quantum wells due to scattering by interface roughness, phonons, alloy disorder, and impurities
We calculate the intersubband absorption linewidth in quantum wells (QWs) due
to scattering by interface roughness, LO phonons, LA phonons, alloy disorder,
and ionized impurities, and compare it with the transport energy broadening
that corresponds to the transport relaxation time related to electron mobility.
Numerical calculations for GaAs QWs clarify the different contributions of each
individual scattering mechanism to absorption linewidth and transport
broadening. Interface roughness scattering contributes about an order of
magnitude more to linewidth than to transport broadening, because the
contribution from the intrasubband scattering in the first excited subband is
much larger than that in the ground subband. On the other hand, LO phonon
scattering (at room temperature) and ionized impurity scattering contribute
much less to linewidth than to transport broadening. LA phonon scattering makes
comparable contributions to linewidth and transport broadening, and so does
alloy disorder scattering. The combination of these contributions with
significantly different characteristics makes the absolute values of linewidth
and transport broadening very different, and leads to the apparent lack of
correlation between them when a parameter, such as temperature or alloy
composition, is changed. Our numerical calculations can quantitatively explain
the previously reported experimental results.Comment: 17 pages, including 15 figure
Presenilin-2 Mutation Causes Early Amyloid Accumulation and Memory Impairment in a Transgenic Mouse Model of Alzheimer's Disease
In order to clarify the pathophysiological role of presenilin-2 (PS2) carrying the Volga German Kindred mutation (N141I) in a conventional mouse model of Alzheimer's disease (AD) expressing amyloid precursor protein (APP) with the Swedish mutation (Tg2576 line), we generated a double transgenic mouse (PS2Tg2576) by crossbreeding the PS2 mutant with Tg2576 mice. Here, we demonstrate that the PS2 mutation induced the early deposition of amyloid β-protein (Aβ) at 2-3 months of age and progressive accumulation at 4-5 months of age in the brains of the mutant mice. The PS2 mutation also accelerated learning and memory impairment associated with Aβ accumulation at 4-5 months of age in Tg2576 mice. These results suggest that the PS2 mutation causes early cerebral amyloid accumulation and memory dysfunction. PS2Tg2576 mice are a suitable mouse model for studying amyloid-lowering therapies
On-demand transfer of trapped photons on a chip
チップ上の微小点に保存した光の瞬時転送. 京都大学プレスリリース. 2016-05-26.Photonic crystal nanocavities, which have modal volumes of the order of a cubic wavelength in the material, are of great interest as flexible platforms for manipulating photons. Recent developments in ultra-high quality factor nanocavities with long photon lifetimes have encouraged us to develop an ultra-compact and flexible photon manipulation technology where photons are trapped in networks of such nanocavities. The most fundamental requirement is the on-demand transfer of photons to and from the trapped states of arbitrary nanocavities. We experimentally demonstrate photon transfer between two nearly resonant nanocavities at arbitrary positions on a chip, triggered by the irradiation of a third nonresonant nanocavity using an optical control pulse. We obtain a high transfer efficiency of ~90% with a photon lifetime of ~200 ps
定量的解析および時系列解析を用いた静止立位姿勢時における重心動揺に関する研究
取得学位:博士(学術),学位授与番号:博甲第850号,学位授与年月日:平成18年9月28
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