An integrated study of earth resources in the State of California based on Skylab and supporting aircraft data

There are no author-identified significant results in this report

Residual value of rock phosphate fertilizers

The residual value of Christmas Island C-grade ore, 500 degrees C heated (calcined) C-grade ore (Calciphos), and superphosphate was measured in three experiments. Plant yield, and bicarbonate-soluble phosphorus extracted from the top 10 cm of soil were used to indicate the effectiveness of the four fertilizers. Using either of these indicators, superphosphate was the most effective fertilizer

Contact area of rough spheres: Large scale simulations and simple scaling laws

We use molecular simulations to study the nonadhesive and adhesive atomic-scale contact of rough spheres with radii ranging from nanometers to micrometers over more than ten orders of magnitude in applied normal load. At the lowest loads, the interfacial mechanics is governed by the contact mechanics of the first asperity that touches. The dependence of contact area on normal force becomes linear at intermediate loads and crosses over to Hertzian at the largest loads. By combining theories for the limiting cases of nominally flat rough surfaces and smooth spheres, we provide parameter-free analytical expressions for contact area over the whole range of loads. Our results establish a range of validity for common approximations that neglect curvature or roughness in modeling objects on scales from atomic force microscope tips to ball bearings.Comment: 2 figures + Supporting Materia

An integrated study of earth resources in the State of California based on ERTS-1 and supporting aircraft data

There are no author-identified significant results in this report

Lava channel formation during the 2001 eruption on Mount Etna: evidence for mechanical erosion

We report the direct observation of a peculiar lava channel that was formed near the base of a parasitic cone during the 2001 eruption on Mount Etna. Erosive processes by flowing lava are commonly attributed to thermal erosion. However, field evidence strongly suggests that models of thermal erosion cannot explain the formation of this channel. Here, we put forward the idea that the essential erosion mechanism was abrasive wear. By applying a simple model from tribology we demonstrate that the available data agree favorably with our hypothesis. Consequently, we propose that erosional processes resembling the wear phenomena in glacial erosion are possible in a volcanic environment.Comment: accepted for publication in Physical Review Letter

Integrated side-scan, sub-bottom profiler and seismic signatures of methane seepage from Omakere Ridge on New Zealand’s Hikurangi margin

Omakere Ridge is one of a series of prominent northeast-southwest orientated anticlinal ridges associated with major thrust faults on New Zealand’s Hikurangi margin. The Hikurangi margin is an extensive gas hydrate province and recent marine surveys have confirmed that the mid-slope Omakere Ridge is a zone of methane-rich seabed seepage. Acoustic flares initially observed in the area by fishermen, were imaged in the water column at Omakere Ridge during a 2006 RV Tangaroa survey (TAN06-07). Anomalous methane concentrations (up to 165 nM) were detected by a methane sensor (METS) attached to a conductivity-temperature-depth-optical backscatter device (CTD) on TAN06-07 and a 2007 RV Sonne survey (SO-191). Six seep sites have been identified at the southern end of Omakere Ridge, where it bifurcates into two parallel ridgelines. All sites are located towards the crests of the two ridgelines in approximately 1150 m water depth. The seabed seeps were identified acoustically with an EdgeTech Deep-Tow side-scan operating at 75 kHz, and are shown as high backscatter intensity areas on processed side-scan data, which are interpreted to be methane derived authigenic carbonate hardgrounds. Acoustic shadows behind hardgrounds in the side-scan far range suggest the seabed features have moderate relief. Sub-bottom profiles acquired with an EdgeTech Deep-Tow chirper system, operating at 2-10 kHz, identified numerous signatures of shallow gas in the near subsurface. These signatures include zones of acoustic turbidity and gas blanking, interpreted to mark shallow gas fronts. The evidence for shallow gas in the subsurface from the sub-bottom profiler displays a marked spatial correlation with seabed expressions of seepage. The seepage sites also correspond to potential gas indicators in multi-channel seismic data, such as interpreted amplitude anomalies. Enigmatic subsurface features in the subbottom profiler data, such as potential amplitude anomalies and gas blanking, which are below the depression that bifurcates the ridge and are not associated with surface expressions of seepage, may represent lithological and topographic features or may be a component of the gas migration pathway which feeds the seeps on the ridge crest. Underwater video and still camera images show seabed seepage sites of high backscatter intensity represent widespread authigenic carbonate concretions and chemoherms associated with biological assemblages including siboglinid tube worms, vesicomyid clams, bathymodiolin mussels, and bacterial mats. A high backscatter intensity site of similar acoustic character to, and directly adjacent to, seep sites on the southern part of the ridge does not contain seep fauna and is interpreted to be a cold-water reef. While this feature may represent a relict seep, this finding highlights the fact that present day seepage cannot be identified with acoustic techniques alone

Plate-impact loading of cellular structures formed by selective laser melting

Porous materials are of great interest because of improved energy absorption over their solid counterparts. Their properties, however, have been difficult to optimize. Additive manufacturing has emerged as a potential technique to closely define the structure and properties of porous components, i.e. density, strut width and pore size; however, the behaviour of these materials at very high impact energies remains largely unexplored. We describe an initial study of the dynamic compression response of lattice materials fabricated through additive manufacturing. Lattices consisting of an array of intersecting stainless steel rods were fabricated into discs using selective laser melting. The resulting discs were impacted against solid stainless steel targets at velocities ranging from 300 to 700 m s-1 using a gas gun. Continuum CTH simulations were performed to identify key features in the measured wave profiles, while 3D simulations, in which the individual cells were modelled, revealed details of microscale deformation during collapse of the lattice structure. The validated computer models have been used to provide an understanding of the deformation processes in the cellular samples. The study supports the optimization of cellular structures for application as energy absorbers. © 2014 IOP Publishing Ltd

Sugar-sweetened beverage consumption, correlates and interventions among Australian Aboriginal and Torres Strait Islander communities: a scoping review protocol

Introduction: Aboriginal and Torres Strait Islander communities of Australia experience poorer health outcomes in the areas of overweight and obesity, diabetes and cardiovascular disease. Contributing to this burden of disease in the Australian community generally and in Aboriginal and Torres Strait Islander communities, is the consumption of sugar-sweetened beverages (SSBs). We have described a protocol for a review to systematically scope articles that document use of SSBs and interventions to reduce their consumption with Aboriginal and Torres Strait Islander people. These results will inform future work that investigates interventions aimed at reducing harm associated with SSB consumption. Methods and analysis: This scoping review draws on a methodology that uses a six-step approach to search databases including PubMed, SCOPUS, CINAHL, Informit (including Informit: Indigenous Peoples), Joanna Briggs Institute EBP Database and Mura, between January 1980 and February 2017. Two reviewers will be engaged to search for and screen studies independently, using formulated selection criteria, for inclusion in our review. We will include primary research studies, systematic reviews including meta-analysis or meta-synthesis, reports and unpublished grey literature. Results will be entered into a table identifying study details and characteristics, summarised using a Preferred Reporting Items for Systematic Reviews and Meta-Analysis chart and then critically analysed. Ethics and dissemination: This review will not require ethics committee review. Results will be disseminated at appropriate scientific meetings, as well as through the Aboriginal and Torres Strait Islander community.Jodie C Avery, Jacqueline A Bowden, Joanne Dono, Odette R Gibson, Aimee Brownbill, Wendy Keech, David Roder, Caroline L Mille

Brownian motion with dry friction: Fokker-Planck approach

We solve a Langevin equation, first studied by de Gennes, in which there is a solid-solid or dry friction force acting on a Brownian particle in addition to the viscous friction usually considered in the study of Brownian motion. We obtain both the time-dependent propagator of this equation and the velocity correlation function by solving the associated time-dependent Fokker-Planck equation. Exact results are found for the case where only dry friction acts on the particle. For the case where both dry and viscous friction forces are present, series representations of the propagator and correlation function are obtained in terms of parabolic cylinder functions. Similar series representations are also obtained for the case where an external constant force is added to the Langevin equation.Comment: 18 pages, 13 figures (in color