Lead pre-concentration using a novel manganese dioxide resin

A novel manganese dioxide (MnO₂) resin is suitable for the determination and decontamination of lead isotopes (²⁰⁸Pb, ²⁰⁷Pb, ²⁰⁶Pb) in aqueous solutions at trace concentrations. This is desirable due to the toxic nature and high abundance of lead in the environment. Current techniques are both time consuming, expensive and not suitable for low-level lead decontamination. The MnO₂ resin has been demonstrated to pre-concentrate with extraction efficiency above 90% for a range of pH values, and with a mean extraction of 92.5% from fresh waters at a flow rate of 100?ml?min^?1. The lead distribution coefficient is 1.3?×?10⁴ (pH 7) with tolerance to calcium and sodium. Adsorption isotherms have been investigated and the resin shown to follow the Langmuir adsorption isotherm with a saturation point of 41.5?mg per g of MnO₂ resin.     

Resolution and significance assessment of precursory changes in mean earthquake magnitudes

The Loma Prieta earthquake (magnitude 7.0), which occurred in October 1989 in central California, was preceded by a period during which the mean magnitude of background seismicity in a small region near the eventual epicentre was abnormally low. This period may have begun as early as 1979, and it continued until mid-1988, after which the mean magnitude increased to a higher than normal value until the main earthquake. These changes were observed in the seismicity of an area 40  km in radius, centred on the Loma Prieta epicentre, and are consistent with the predictions of fracture mechanics studies. The 1988 change correlates with a reported change in long-term strain.
  A procedure has been developed for resolving such temporal changes in seismicity using CUSUM statistics. It demonstrates that the anomaly was highly significant, on the basis of analyses of two independent catalogues. There was also a significant anomaly before the 1994 Northridge earthquake.
  The hypothesis that large earthquakes are preceded by periods in which the mean magnitude of background activity is abnormally low, in the immediate vicinity of the eventual epicentre, is a tantalizing one. The analysis tool examined here may be useful for resolving such changes. Care needs to be taken, however, in routine surveillance of earthquake populations that contain large aftershock sequences.     

Discovery of an X-ray-selected radio-loud obscured AGN at z = 1.246

We have discovered an obscured active galaxy at redshift z  = 1.246 identified with the ROSAT X-ray source RX J1011.2+5545. We report on multiwavelength observations of this source and discuss its X-ray, optical and radio properties. This is the first X-ray-selected, obscured active galaxy at high redshift to be shown to be radio-loud, with a radio counterpart exhibiting a classical double-lobe morphology.     

A model for Type-IV emission in the solar burst of June 9, 1959 at decametric wavelengths

A major radio burst at decametric frequencies at 1638 UT on June 9, 1959 is apparently a Type-IV continuum burst of the kind that drifts from high to low frequencies. We present observations of flux variations and East-West positions of the emission at both 18 and 38 MHz. The burst moves outward at a speed of about 4700 km·sec^?1 at each frequency to a height of about 3 R _⊙ from the sun's center and then returns to the sun. This behavior is not simultaneous at 18 MHz and 38 MHz; the outward moving phase of 18 MHz emission occurs during the return phase of 38 MHz. We suspect that a solitary Alfvén wave or shock traverses the outer corona at the time of this burst. Relativistic electrons created low in the solar atmosphere travel freely along radial lines of force up to the coronal-streamer heights of the Type-IV burst. Upon encountering the shock, the electrons emit locally intense synchrotron emission, and pass through the shock on out into interplanetary space. This model appears to be consistent with other shock front phenomena in interplanetary space and the corona. Finally, the Razin effect (Boischot and Clavelier, 1967) suggests that low-frequency cut-offs in Type-IV bursts ought to be quite constant in frequency, and not higher than between 0.4 to 4 MHz.     

Investigating education,migration and development – Moving triangles in the Pacific

Is it possible that education in the Global South leads to emigration and is therefore detrimental to development prospects? For the Pacific Islands region, this issue is particularly pertinent, given the high rates of migration and the strong emphasis placed on education as a basis for development. Although our knowledge of the bilateral relations between, respectively, education and development, education and migration, and migration and development have advanced, we know very little of the complex interplay between the three. In this article, we suggest a new approach to the trilateral relationship among education, migration and development in the Pacific Islands which may have implications beyond that region.