The Conch Fisheries of the Bahamas

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Soil-Saprolite Profiles Derived from Mafic Rocks in the North Carolina Piedmont: II. Association of Free Iron Oxides with Soils and Clays

The association of free Fe oxides with soils and clays from two Enon sandy loam (Ultic Hapludalfs, fine, mixed, thermic) soilsaprolite profiles was studied. Goethite was the dominant Fe oxide identified. Lepidocrocite was detected in trace amounts in some samples. FeCBD/clay ratios were highest in the epipedons of these soils suggesting the concentrating of Fe oxides as a result of aluminosilicate mineral weathering. External (BET-N2) surface area measurements of non-deferrated and deferrated clays were analyzed in conjunction with electron micrographs of selected clay fractions to determine the association of free Fe oxides with aluminosilicate clays as a function of depth in the profile. Free Fe oxides were found to exist mainly as small, discrete clusters in the A and B horizons of both profiles and specific of the clay surface decreased as a result of treatment for Fe removal. However, external surface areas increased for the saprolite (Cr) horizon clays after deferration. One subfraction identified as having an increase in surface area after deferration was fine clay from the Cr2 horizon, Enon (metagabbro) profile. Chemical data and electron micrographs suggest that either partial dissolution of small, poorly crystalline aluminosilicate clays or removal of some Fe or non-Fe oxide aggregating agent results in breakdown of the fine clays into smaller particles of higher net specific surface

A Rapid Technique for Counting Cracks in Rocks

Using a scanning electron microscope (SEM) and an image analyzer, we have developed a technique for counting and measuring cracks in rocks which is more efficient than traditional techniques in which an operator performs all image analysis functions. The key aspect of the technique is that black-on-white tracings of fresh cracks, which can be made rather rapidly by an operator, are measured and digitized by an image analyzer. The most time-consuming step in the process has now become the generation of SEM micrographs and pertinent chemical (mineralogical) information, not the quantification of crack structure. The technique has been applied to two studies involving nuclear waste isolation in a granitic rock, Climax Stock (Nevada Test Site) quartz monzonite, a Cretaceous age rock which is structurally very inhomogeneous. One study detected a relationship between crack structure and distance from a hammer-drilled borehole; the other study was unable to detect a relationship between crack structure and gamma irradiation treatment in rocks loaded to near failure

Soil-Saprolite Profiles Derived from Mafic Rocks in the North Carolina Piedmont: I. Chemical, Morphological, and Mineralogical Characteristics and Transformations

The chemical, morphological and mineralogical properties of two Enon sandy loam (fine, mixed, thermic Ultic Hapludalfs) soilsaprolite profiles, one formed on gabbro and the other on metagabbro, are compared. Clay skins are scarce and stress cutans common in the argillic horizons of these soils. Iron-manganese concretions are concentrated in soil horizons immediately above the argillic horizons. The high shrink-swell capacities and slow permeabilities of the argillic horizons result in relatively shallow depths to paralithic contact with saprolite. The parent rock from the Enon profile near Albemarle, Stanly County, North Carolina is a medium-grained metagabbro with chlorite, hornblende, quartz, and calcic plagioclase feldspar as the dominant primary minerals. Chlorite weathers to regularly interstratified chlorite-vermiculite, which alters to randomly interstratified chlorite-vermiculite and smectite. Particle size decreases with each mineral alteration. Hornblende weathers to smectite and goethite. Calcic plagioclase feldspar transforms to kaolinite in the saprolite and soil horizons. Quartz is relatively resistant to chemical weathering. The parent rock of the Enon profile near Concord, Cabarrus County, North Carolina is a coarse-grained gabbro with hornblende and calcic plagioclase feldspar as the dominant primary minerals. Hornblende transforms to smectite and goethite. Calcic plagioclase feldspar alters to kaolinite in the saprolite and soil horizon

Nano-porosity in GaSb induced by swift heavy ion irradiation

Nano-porous structures form in GaSb after ion irradiation with 185 MeV Au ions. The porous layer formation is governed by the dominant electronic energy loss at this energy regime. The porous layer morphology differs significantly from that previously reported for low-energy, ion-irradiated GaSb. Prior to the onset of porosity, positron annihilation lifetime spectroscopy indicates the formation of small vacancy clusters in single ion impacts, while transmission electron microscopy reveals fragmentation of the GaSb into nanocrystallites embedded in an amorphous matrix. Following this fragmentation process, macroscopic porosity forms, presumably within the amorphous phase.The authors thank the Australian Research Council for support and the staff at the ANU Heavy Ion Accelerator Facility for their continued technical assistance. R.C.E. acknowledges the support from the Office of Basic Energy Sciences of the U.S. DOE (Grant No. DE-FG02-97ER45656)

Radioisotope Positron Propulsion

Producing antimatter is straight forward, but antimatter trapping is challenging. Our concept uses a radioisotope to generate antimatter via beta-decay. These antimatter particles are collected, and their density tailored to generate fusion reactions which provides high performance thrust. The neutrons produced in the fusion reaction are used to generate more radioisotope via neutron capture. This constitutes the first dosed-closed cycle antimatter rocket engine of its kind.Why Positrons? The positron, or anti-electron, is the antimatter counterpart of the electron. It has the same mass as an electron but opposite charge. Positrons are produced by several readily available radioisotopes (e.g. Na-22, Co-58, Kr-79) in large number and with a broad energy spread. By creating long-lived radioisotopes that emit positrons, we can essentially 'store' the positrons in the nuclei of the radioisotope, eliminating the need for high magnetic field storage techniques. In light of these high delta-V mission opportunities and Positron Dynamics' technology developments, we propose a means of antimatter-based propulsion that does not require gamma ray reflection, long-term storage of antiprotons or positrons, and can be integrated into a medium sized (< 1000kg) spacecraft. In this Phase I effort, we have analyzed the feasibility of this radioisotope positron propulsion (RPP) concept. In addition, we have applied the concept to a specific mission, the capture/redirect of asteroid 2009BD, comparing the performance of RPP with the original electric propulsion ARM concept