888 research outputs found
非熱的準静的剪断下での摩擦のある粒子からなるアモルファス固体の固有値解析
京都大学新制・課程博士博士(理学)甲第24397号理博第4896号新制||理||1699(附属図書館)京都大学大学院理学研究科物理学・宇宙物理学専攻(主査)教授 早川 尚男, 教授 佐々 真一, 准教授 藤 定義学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDFA
A Novel Target of Action of Minocycline in NGF-Induced Neurite Outgrowth in PC12 Cells: Translation Initiation Factor eIF4AI
Background: Minocycline, a second-generation tetracycline antibiotic, has potential activity for the treatment of several neurodegenerative and psychiatric disorders. However, its mechanisms of action remain to be determined. Methodology/Principal Findings: We found that minocycline, but not tetracycline, significantly potentiated nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells, in a concentration dependent manner. Furthermore, we found that the endoplasmic reticulum protein inositol 1,4,5-triphosphate (IP3) receptors and several common signaling molecules (PLCc, PI3K, Akt, p38 MAPK, c-Jun N-terminal kinase (JNK), mammalian target of rapamycin (mTOR), and Ras/Raf/ERK/MAPK pathways) might be involved in the active mechanism of minocycline. Moreover, we found that a marked increase of the eukaryotic translation initiation factor eIF4AI protein by minocycline, but not tetracycline, might be involved in the active mechanism for NGF-induced neurite outgrowth. Conclusions/Significance: These findings suggest that eIF4AI might play a role in the novel mechanism of minocycline. Therefore, agents that can increase eIF4AI protein would be novel therapeutic drugs for certain neurodegenerative an
Dilatancy of frictional granular materials under oscillatory shear with constant pressure
We perform numerical simulations of a two-dimensional frictional granular
system under oscillatory shear confined by constant pressure. We found that the
system undergoes dilatancy as the strain increases. We confirmed that
compaction also takes place at an intermediate strain amplitude for a small
mutual friction coefficient between particles. We also found that compaction
depends on the confinement pressure while dilatancy little depends on the
pressure.Comment: 4 pages, 4 figure
Finite-temperature phase diagram of two-component bosons in a cubic optical lattice: Three-dimensional t-J model of hard-core bosons
We study the three-dimensional bosonic t-J model, i.e., the t-J model of
"bosonic electrons", at finite temperatures. This model describes the Heisenberg spin model with the anisotropic exchange coupling
and doped {\it bosonic} holes, which is an effective
system of the Bose-Hubbard model with strong repulsions. The bosonic "electron"
operator at the site with a two-component (pseudo-)spin
is treated as a hard-core boson operator, and represented by a
composite of two slave particles; a "spinon" described by a Schwinger boson
(CP boson) and a "holon" described by a hard-core-boson field
as . By means of Monte Carlo
simulations, we study its finite-temperature phase structure including the
dependence, the possible phenomena like appearance of checkerboard
long-range order, super-counterflow, superfluid, and phase separation, etc. The
obtained results may be taken as predictions about experiments of two-component
cold bosonic atoms in the cubic optical lattice.Comment: 8 pages, 14 figures, Size of figures has been adjuste
Eigenvalue analysis of stress-strain curve of two-dimensional amorphous solids of dispersed frictional grains with finite shear strain
The stress-strain curve of two-dimensional frictional dispersed grains
interacting with a harmonic potential without considering the dynamical slip
under a finite strain is determined by using eigenvalue analysis of the Hessian
matrix. After the configuration of grains is obtained, the stress-strain curve
based on the eigenvalue analysis is in almost perfect agreement with that
obtained by the simulation, even if there are plastic deformations caused by
stress avalanches. Unlike the naive expectation, the eigenvalues in our model
do not indicate any precursors to the stress-drop events.Comment: 22 pages, 16 figures. arXiv admin note: text overlap with
arXiv:2207.0663
Theory of rigidity and density of states of two-dimensional amorphous solids of dispersed frictional grains in the linear response regime
Using the Jacobian matrix, we theoretically determine the rigidity of
two-dimensional amorphous solids consisting of frictional grains in the linear
response to an infinitesimal strain, in which we ignore the dynamical friction
caused by the slip processes of contact points. The theoretical rigidity agrees
with that obtained by molecular dynamics simulations. We confirm that the
rigidity is smoothly connected to the value in the frictionless limit. We find
that there are two modes in the density of states for sufficiently small
, which is the ratio of the tangential to normal stiffness.
Rotational modes exist at low frequencies or small eigenvalues, whereas
translational modes exist at high frequencies or large eigenvalues. The
location of the rotational band shifts to the high-frequency region with an
increase in and becomes indistinguishable from the translational
band for large . The rigidity determined by the translational
modes agrees with that obtained by the molecular dynamics simulations, whereas
the contribution of the rotational modes is almost zero for small
.Comment: 10 pages, 15 figure
Malin and laforin are essential components of a protein complex that protects cells from thermal stress
The heat-shock response is a conserved cellular process characterized by the induction of a unique group of proteins known as heat-shock proteins. One of the primary triggers for this response, at least in mammals, is heat-shock factor 1 (HSF1) – a transcription factor that activates the transcription of heat-shock genes and confers protection against stress-induced cell death. In the present study, we investigated the role of the phosphatase laforin and the ubiquitin ligase malin in the HSF1-mediated heat-shock response. Laforin and malin are defective in Lafora disease (LD), a neurodegenerative disorder associated with epileptic seizures. Using cellular models, we demonstrate that these two proteins, as a functional complex with the co-chaperone CHIP, translocate to the nucleus upon heat shock and that all the three members of this complex are required for full protection against heat-shock-induced cell death. We show further that laforin and malin interact with HSF1 and contribute to its activation during stress by an unknown mechanism. HSF1 is also required for the heat-induced nuclear translocation of laforin and malin. This study demonstrates that laforin and malin are key regulators of HSF1 and that defects in the HSF1-mediated stress response pathway might underlie some of the pathological symptoms in LD
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