Kentaro Nakamura

Indian Ocean hydrothermal vents are believed to represent a novel biogeographic province, and are host to many novel genera and families of animals, potentially indigenous to Indian Ocean hydrothermal systems. In particular, since its discovery in 2001, much attention has been paid to a so-called 'scaly-foot' gastropod because of its unique iron-sulfide-coated dermal sclerites and the chemosynthetic symbioses in its various tissues. Despite increasing interest in the faunal assemblages at Indian

A finite-element method for the analysis of eigenstates in a quantum well, which is based on the Galerkin procedure, is discussed. A general boundary condition of the envelope function at the heterointerface is introduced by using the transfer matrix. The validity of the method is confirmed by calculating the eigenstates of GaAs/AlGaAs and InAs/GaSb rectangular quantum wells. Numerical examples of voltage-applied quantum wells are presented.

In the past few decades, chemosynthetic ecosystems at deep-sea hydrothermal vents have received attention as plausible analogues to the early ecosystems of Earth, as well as to extraterrestrial ecosystems. These ecosystems are sustained by chemical energy obtained from inorganic redox substances (e.g., H 2 S, CO 2 , H 2 , CH 4 , and O 2 ) in hydrothermal fluids and ambient seawater. The chemical and isotope compositions of the hydrothermal fluid are, in turn, controlled by subseafloor physical a

Polymetallic sulfides deposited in seafloor hydrothermal vents have recently attracted attention as potential deep-sea mineral resources for base, rare, and precious metals such as Cu, Zn, Pb, In, Ga, Ge, Au, and Ag. For future exploitation of this type of deep-sea mineral resources, development of effective methods for exploring seafloor hydrothermal activity is a key to provide the most promising list of fields. However, conventional exploration methods are likely laborious and time-consuming,

Deep-sea sediments containing high concentrations of rare-earth elements and yttrium (REY), termed REY-rich mud, are widely distributed in the Pacific and Indian oceans. Mud layers with very high total REY (ΣREY) concentrations (>5000 ppm of ΣREY with ~1000 ppm of heavy rare-earth elements) have been discovered within the Japanese exclusive economic zone surrounding Minamitorishima Island, western North Pacific. The number of highly REY-enriched layers in the sediment column, the depths at which