A rock‐magnetic study of giant piston core LL44‐GPC3 from the central North Pacific and its paleoceanographic implications

Previous magnetostratigraphic studies of nonfossiliferous pre‐Pliocene age pelagic clay cores from the central north Pacific have proven unsuccessful because of the unstable behavior of the natural remanent magnetization. The inability to obtain a reliable magnetostratigraphy has severely limited the temporal resolution that can be achieved in paleoceanographic studies of these nonfossiliferous pelagic clays. We carried out a rock‐magnetic study of core LL44‐GPC3, which spans the interval 0‐70 m.y. ago, to determine whether rock‐magnetic parameters can be used to construct a high‐resolution stratigraphic framework for paleoceanographic studies of central north Pacific pelagic clays despite the instability of the natural remanence. In addition, we tested the ability of rock‐magnetic methods to detect and characterize the paleoceanographic changes that are recorded in the sediments of LL44‐GPC3. Stratigraphic variations in rapid and nondestructive rock‐magnetic parameters and related ratios reflect changes in the concentration, mineralogy, and grain size of the magnetic minerals within the sediments. Rock‐magnetic parameters exhibit coherent fluctuations within both the stable and unstable sections of LL44‐GPC3. This result suggests the potential use of these parameters for regional correlation and relative dating of the nonfossil‐bearing pelagic clays of the central north Pacific gyre. Major fluctuations in rock‐magnetic parameters plotted as accumulation rates correspond to intervals of paleoenvironmental change that have been previously detected by other paleoceanographic methods. In addition, variations in a parameter proportional to the concentration of goethite/hematite correlate remarkably well with the mass accumulation rate of the total eolian component, suggesting that in some situations it can be used as a proxy indicator for eolian activity. Copyright 1988 by the American Geophysical Union

Magnetic Fabrics and Source Implications of Chisulryoung Ignimbrites, South Korea

The anisotropy of magnetic susceptibility (AMS) of late Cretaceous ash-flow tuffs in Chisulryoung Volcanic Formation, southeastern Korea was studied to define the primary pyroclastic flow azimuth. AMS data revealed a dominant oblate fabric with a tight clustering of k3 (minimum axis of magnetic susceptibility) and shallow dispersal of k1 (maximum axis of magnetic susceptibility) and k2 (intermediate axis of magnetic susceptibility). Dominance of oblate fabrics indicates clast imbrications imposed by compaction and welding. Flow azimuth inferred from AMS data indicates the nearby intrusive welded tuff (IWT) as the source of calderas for ignimbrites. Such an inference is supported by geologic investigations, in which the IWT displays eutaxitic textures nearly parallel to its subvertical contacts. The results are compatible with a unique prolate fabric and an anomalously high inclination observed for the IWT, possibly produced by rheomorphic flows as the welded tuff is squeezed along the rough-surfaced dyke walls due to agglutination

Scheduling support for guaranteed time services in IEEE 802.15.4 low rate WPAN

We propose a real-time message scheduling algorithm which is applied to schedule periodic real-time messages in IEEE 802.15.4 for LR-WPAN(Low Rate Wireless Personal Area Network). The standard allows GTSs (Guaranteed Time Slots) in the optional use of a superframe structure in a beacon-enabled network to be used to exchange real-time messages. To utilize these features of the standard efficiently, a proper message scheduling algorithm is needed. The proposed off-line message scheduling algorithm which is based on a distance constrained scheduler generates the standard specific parameters including BO, SO, and GTS information to schedule the given message set. The algorithm is evaluated by simulation and the guaranteed time service using the schedule is implemented and evaluated on CC2420DB which is a prototyping platform including an IEEE 802.15.4 compliant transceiver of Chipcon AS

Fine Phantom Image from Laser-induced Proton Radiography with a Spatial Resolution of Several μm

The advantages of a laser-driven proton acceleration have prompted studies of laser-induced proton radiography. As the CR-39 solid-state nuclear-track detector is suitable for measuring charged particles and can be used in proton radiography, we studied laser-induced proton radiography with the CR-39 for several years, and we were able to obtain a spatial resolution of about 10 μm. For obtaining an image with a spatial resolution of a few μm, we investigated the effect of the CR-39 etching conditions on the spatial resolution and carried out imaging experiments using fine phantoms. Experiments were performed using the 100-TW titanium-sapphire laser system at the Advanced Photonics Research Institute of the Gwangju Institute of Science Technology. We have demonstrated that images with a spatial resolution of about several μm can be achieved using laser-induced proton radiography.1221sciescopuskc