12,542 research outputs found
Slowly modulated oscillations in nonlinear diffusion processes
It is shown here that certain systems of nonlinear (parabolic) reaction-diffusion equations have solutions which are approximated by oscillatory functions in the form R(ξ - cτ)P(t^*) where P(t^*) represents a sinusoidal oscillation on a fast time scale t* and R(ξ - cτ) represents a slowly-varying modulating amplitude on slow space (ξ) and slow time (τ) scales. Such solutions describe phenomena in chemical reactors, chemical and biological reactions, and in other media where a stable oscillation at each point (or site) undergoes a slow amplitude change due to diffusion
Structural Transition of Li2RuO3 Induced by Molecular-Orbit Formation
A pseudo honeycomb system Li2RuO3 exhibits a second-order-like transition at
temperature T=Tc=540 K to a low-T nonmagnetic phase with a significant lattice
distortion forming Ru-Ru pairs. For this system, we have calculated the band
structure, using the generalized gradient approximation (GGA) in both the high-
and low- T phases, and found that the results of the calculation can naturally
explain the insulating behavior observed in the low-T phase. The detailed
characters of the Ru 4d t2g bands obtained by the tight-binding fit to the
calculated dispersion curves show clear evidence that the structural transition
is driven by the formation of the Ru-Ru molecular-orbits, as proposed in our
previous experimental studies.Comment: 5 pages, 5 figures, 4 tables, submitted to J. Phys. Soc. Jp
Bi-maximal mixing at GUT, the low energy data and the leptogenesis
In the framework of the minimum supersymmetric model with right-handed
neutrinos, we consider the Bi-maximal mixing which is realized at the GUT scale
and discuss a question that this model can reproduce the low energy phenomena
and the leptogenesis.Comment: Talk given by E. Takasugi at NuFact04, Osaka, Japan, July 26 - August
1,2004 - 3 pages, 4 figure
Mediators of mechanotransduction between bone cells
Mechanical forces are known to regulate the function of tissues in the body, including bone. Bone adapts to its mechanical environment by altering its shape and increasing its size in response to increases in mechanical load associated with exercise, and by decreasing its size in response to decreases in mechanical load associated with microgravity or prolonged bed rest. Changes in bone size and shape are produced by a cooperative action of two main types of the bone cells - osteoclasts that destroy bone and osteoblasts that build bone. These cell types come from different developmental origins, and vary greatly in their characteristics, such as size, shape, and expression of receptor subtypes, which potentially may affect their responses to mechanical stimuli. The objective of this study is to compare the responses of osteoclasts and osteoblasts to mechanical stimulation.
This study has allowed us to conclude the following:
1. A mediator is released from a single source cell.
2. The response to the mediator changes with distance.
3. The value of the apparent diffusion coeficient increases with distance.
4. A plausible proposed mechanism is that ATP is released and degrades to ADP.
5. Future experiments are required to confim that ATP is the mediator as suggested
Capture of free-flying payloads with flexible space manipulators
A recently developed control system for capturing free-flying payloads with flexible manipulators is discussed. Three essential points in this control system are, calculating optimal path, using a vision sensor for an external sensor, and controlling active vibration. Experimental results are shown using a planar flexible manipulator
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