Interrelation of the stagnant slab, Ontong Java Plateau, and intraplate volcanism as inferred from seismic tomography.

We investigated the seismological structure beneath the equatorial Melanesian region, where is tectonically unique because an immense oceanic plateau, a volcanic chain and subduction zones meet. We conducted a multi-frequency P-wave tomography using data collected from an approximately 2-year-long seismic experiment around the Ontong Java Plateau (OJP). High-velocity anomalies were revealed beneath the center of the OJP at a depth of ~ 150 km, the middle-eastern edge of the OJP at depths of 200-300 km, and in the mantle transition zone beneath and around the OJP; low-velocity anomalies were observed along the Caroline volcanic island chain above 450 km depth. These anomalies are considered to be associated with the thick lithosphere of the OJP, remnant dipping Pacific slab, stagnant Pacific slab, and a sheet-like upwelling. The broad stagnant slab was formed due to rapid trench retreat from 48 to 25 Ma until when the OJP with thick lithosphere collided with a subduction boundary of the Pacific and Australian plates. This collision triggered slab breakoff beneath the arc where the dipping slab remained. The stagnant Pacific slab in the mantle transition zone restricted the plume upwelling from the lower mantle causing sheet-like deformed upwelling in the upper mantle.

Awareness of ethical issues by nursing professionals at a general local hospital in Japan.

In recent years, various ethical issues have arisen in the field of medical practice because of the dramatic changes in medical technology and diversity among the different population. It is generally believed that nurses often find themselves in ethical dilemmas because of their closeness to their patients. In this study, we examined nursing professionals' awareness about ethical issues and examined their responses to them at a general hospital performing important roles in the Chugoku district in Japan. The subjects consisted of 335 nurses working at this hospital. An anonymous self-administrated questionnaire was given to them in 2003. As a result, 30-35% of the nurses responded that they were either worried about or were faced with ethical issues when considering specific situations as examples. About 15% of the nurses thought that they were currently worried about or were faced with some ethical issues in practice, which implied a low awareness level of the existence of ethical issues. In terms of their responses to such issues, they usually consulted medical staff members who were directly involved in the case. However, approximately 45% of the nurses reported that no official investigation such as one conducted by an ethics committee, had been conducted regarding such issues, which thus left the problem unsolved. These results suggested that the "subjectivity of nurses" and the "worries and dilemmas of nurses themselves" impacted the nurses' awareness of ethical issues. It appears that further inquiry into ethical issues is needed, with consideration by an ethics committee to better deal with many of the ethical issues.

Tearing of stagnant slab.

Subducted slabs of oceanic lithosphere below the western Pacific tend to be stagnant in the transition zone with poorly known mechanical properties. Typical examples are the Izu-Bonin and Japan slabs that meet each other to form a cusplike junction beneath southwest Japan. Here, we show that these two slabs are torn apart at their junction when they bend to flatten over the 660-kilometer discontinuity, as is expected from a simple geometric argument. We present three lines of evidence for this ongoing slab tear.