Age structure and dynamics of Cercidiphyllum japonicum sprouts based on growth ring analysis

ArticleFOREST ECOLOGY AND MANAGEMENT. 213(1-3): 253-260 (2005)journal articl

Optical Hall Effect in the Integer Quantum Hall Regime

Optical Hall conductivity $\sigma_{xy}(\omega)$ is measured from the Faraday rotation for a GaAs/AlGaAs heterojunction quantum Hall system in the terahertz frequency regime. The Faraday rotation angle ($\sim$ fine structure constant $\sim$ mrad) is found to significantly deviate from the Drude-like behavior to exhibit a plateau-like structure around the Landau-level filling $\nu=2$. The result, which fits with the behavior expected from the carrier localization effect in the ac regime, indicates that the plateau structure, although not quantized, still exists in the terahertz regime.Comment: 4 pages, 4 figure

Modelling of platelet aggregation in aneurysm

Thrombi are often found in aneurysms and are considered to play an important role in rupture. It is crucial to scrutinise any correlation between the probability of rupture and the extent to which thrombi are generated in the aneurysm. Numerical techniques such as computational fluid dynamics (CFD) are promising tools in the biomedical field. However, there are, at present, no models that allow us to evaluate thrombus generation. The authors aim at the proposal of such a model. In the present study, the process of platelet aggregation is considered. In blood flow near the entry to an aneurysm, red blood cells are haemolysed due to high shear stress or high pressure. The ensuing release of adenosine diphosphate (ADP) induces the aggregation. Making reference to actual aggregation curves of human plasma for various ADP concentrations, the authors have modelled the rate at which the density of aggregated platelets continues to increase in the aggregation process. A combination of CFD and the present model enables us to obtain the distribution of platelets clotting in an aneurysm

Similarity and contrasts between thermodynamic properties at the critical point of liquid alkali metals and of electron-hole droplets

The recent experimental study by means of time-resolved luminescence measurements of an electron-hole liquid (EHL) in diamond by Shimano et al. [Phys. Rev. Lett. 88 (2002) 057404] prompts us to compare and contrast critical temperature T_c and critical density n_c relations in liquid alkali metals with those in electron-hole liquids. The conclusion drawn is that these systems have similarities with regard to critical properties. In both cases the critical temperature is related to the cube root of the critical density. The existence of this relation is traced to Coulomb interactions and to systematic trends in the dielectric constant of the electron-hole systems. Finally a brief comparison between the alkalis and EHLs of the critical values for the compressibility ratio Z_c is also given

Study of ortho-to-paraexciton conversion in Cu2_2O by excitonic Lyman spectroscopy

Using time-resolved $1s$-$2p$ excitonic Lyman spectroscopy, we study the orthoexciton-to-paraexcitons transfer, following the creation of a high density population of ultracold $1s$ orthoexcitons by resonant two-photon excitation with femtosecond pulses. An observed fast exciton-density dependent conversion rate is attributed to spin exchange between pairs of orthoexcitons. Implication of these results on the feasibility of BEC of paraexcitons in Cu$_2$O is discussed

Observation of the spin-charge thermal isolation of ferromagnetic Ga_{0.94}Mn_{0.06}As by time-resolved magneto-optical measurement

The dynamics of magnetization under femtosecond optical excitation is studied in a ferromagnetic semiconductor Ga_{0.94}Mn_{0.06}As with a time-resolved magneto-optical Kerr effect measurement with two color probe beams. The transient reflectivity change indicates the rapid rise of the carrier temperature and relaxation to a quasi-thermal equilibrium within 1 ps, while a very slow rise of the spin temperature of the order of 500ps is observed. This anomalous behavior originates from the thermal isolation between the charge and spin systems due to the spin polarization of carriers (holes) contributing to ferromagnetism. This constitutes experimental proof of the half-metallic nature of ferromagnetic Ga_{0.94}Mn_{0.06}As arising from double exchange type mechanism originates from the d-band character of holes

Food and Habitat Selection of Lepus brachyurus lyoni

We determined the environmental requirements for Lepus brachyurus lyoni on Sado Island, Japan. during the winter when food resources are low Flare track survey sites were classified by vegetation type. The movement distances of hares, which indicated habitat preference, were evaluated as the relative length of tracks in a I-ha area In addition, we examined browse marks on plants and the protein content of plants to determine the preferred plant species. Movement distances of hares decreased significantly with increasing tree stand height, mean tree diameter. basal area of the tree stand, and forest canopy closure, but increased with branch-and-stem density. The percentage of browse marks Oil the branches of tree/shrub species decreased significantly with increasing branch-and-stem diameter The rate of feeding increased significantly with increased protein content in the branches These findings suggest that hares prefer shrub stands with high branch-and-stem density to mature forests. which have lower branch-and-stem densities Hares also prefer branches and stems containing large amounts of protein Young stands offering many shrub species as food resources and shelter constitute preferable environments for hare

Homogenization of weakly coupled systems of Hamilton--Jacobi equations with fast switching rates

We consider homogenization for weakly coupled systems of Hamilton--Jacobi equations with fast switching rates. The fast switching rate terms force the solutions converge to the same limit, which is a solution of the effective equation. We discover the appearance of the initial layers, which appear naturally when we consider the systems with different initial data and analyze them rigorously. In particular, we obtain matched asymptotic solutions of the systems and rate of convergence. We also investigate properties of the effective Hamiltonian of weakly coupled systems and show some examples which do not appear in the context of single equations.Comment: final version, to appear in Arch. Ration. Mech. Ana