(Tables 1-3) Pb and Sr isotopic data for sediments and rocks from DSDP holes in the Mariana island-arc system

Analyses of the isotopic composition of Pb in (1) western Pacific Ocean sediments [Jurassic(?) to Pleistocene in age, including clays and biogenic oozes], (2) Pacific Ocean basaltic rocks, (3) Mariana frontal arc volcanic rocks (Eocene to Miocene), and (4) Mariana active arc volcanic rocks [Pliocene (?) to Holocene] indicate that Pacific Ocean sediments could not have been a significant component of the source material for the Mariana arc volcanic rocks. Calculations involving the average concentrations and isotopic compositions of Pb in oceanic sediments, sea-floor basaltic rocks, and the Mariana arc volcanic rocks suggest that the sediment component must have been less than 1 percent of this source material. The Pb isotopic compositions of the Mariana arc volcanic rocks lie, within experimental error, along the trend of available Pacific Ocean basalt analyses in versus 207Pb/204Pb versus 206Pb/204Pb and 208Pb/204Pb versus 206Pb/204Pb diagrams. Isotopic analyses of Pb in Pacific Ocean sediments do not lie along this trend; they have higher 207Pb/204Pb and 208Pb/204Pb values for comparable 206Pb/204Pb ratios. Clayey sediments generally have higher 208Pb/204Pb and 207Pb/204Pb ratios than biogenic oozes regardless of the age of the sediment. Comparison of combined Sr and Pb isotopic analyses for (1) mantle-derived materials erupted through oceanic crust, (2) altered ocean-floor basaltic rocks, and (3) volcanic rocks from oceanic island arcs suggests that the Mariana arc volcanic rocks were derived, at least in part, from altered Pacific lithosphere subducted beneath the Mariana arc. Unaltered basalts from the Mariana inter-arc basin (Mariana Trough) have Pb and Sr isotopic compositions that are very similar to those reported for some Hawaiian volcanic rocks but distinct from Mariana active and frontal arc compositions. These observations, in addition to existing major-and trace-element data, support a mantle origin for the interarc basin volcanic rocks. Dacites dredged from the Mariana remnant arc (South Honshu Ridge) have Pb isotopic compositions that are within experimental error of the active-arc analyses, consistent with a genetic relation.

The use of arc-erosion as a patterning technique for transparent conductive materials

Within the framework of cost-effective patterning processes a novel technique that saves photolithographic processing steps, easily scalable to wide area production, is proposed. It consists of a tip-probe, which is biased with respect to a conductive substrate and slides on it, keeping contact with the material. The sliding tip leaves an insulating path (which currently is as narrow as 30 μm) across the material, which enables the drawing of tracks and pads electrically insulated from the surroundings. This ablation method, called arc-erosion, requires an experimental set up that had to be customized for this purpose and is described. Upon instrumental monitoring, a brief proposal of the physics below this process is also presented. As a result an optimal control of the patterning process has been acquired. The system has been used on different substrates, including indium tin oxide either on glass or on polyethylene terephtalate, as well as alloys like Au/Cr, and Al. The influence of conditions such as tip speed and applied voltage is discussed

On the structure of the floating zone in melting

Floating zone melting is used in crystal growth and purification of high melting materials. The use of a reduced gravity environment will remove the constraint imposed on the length of the zone by the hydrostatic pressure. The equilibrium of the fioatmg zone may involve, (1)Hydrostatic forces, when the zone rotates as a whole. (2)Convective driving forces, when the zone is stationary but fluid property gradients appear.(3) Hydrodynamic forces, when some parts of the zone are set into motion with respect to others. The last effects are considered in this paper. The flow pattern of a floating zone held between two discs in relative motion is complicated, and thence the solution of the problem is difficult even assuming a constant property-newtonian liquid Nevertheless, when a small parameter appears m the problem, the complete flow field can be split into zones where simple solutions are found. To illustrate this approach, the spin up from rest of an initially cylindrical floating zone is considered with detail. Here the small parameter is the time elapsed from the impulsive starting of motion. Since the problem which has been considered, as well as some others which can be tackled by use of similar methods, concern the viscous layer close to either plate, they can be simulated experimentally in the ground laboratory with short floating zones. Procedures to produce these zones are indicated.