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Showing 1 to 20 of 31 for “"Pumice"”.
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Studies of modified pumice and titanomagnetite filtration media
… New Zealand media, titanomagnetite (TM) and pumice were investigated. TM was of interest because its particle size is finer than most filtration media and its magnetic properties allow the possibility of magnetic conditioning of the bed. A modified pumice, marketed as Silicon Sponge (SS), is …
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Cyclic Properties of Natural Soil Containing Pumice Particles
Sands containing pumice particles are commonly found in the Waikato Basin in the North Island of New Zealand. The pumice particles originated from a series of volcanic eruptions centred in the Taupo and Rotorua regions. As a result of flooding and erosion along the Waikato River, the pumice …
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Importance of Pumice Prophylaxis for Orthodontic Bonding with Self-etch Primer: An in vivo Study
… of this study was to assess the importance of a pumice prophylaxis prior to bonding with SEP (Transbond Plus, 3M Unitek, Monrovia, CA) in reducing bond failures. Thirty orthodontic patients volunteered to participate in this split-mouth prospective clinical trial. A pumice prophylaxis …
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Orthodontic Bracket Bond Strength Using Self-Etching Primer With or Without Pumice or Acid Etch Pretreatment
… (Pre-etch), control: SEP with prior pumicing (Pumice), and Pre-etch and SEP with prior pumicing (Both). 80 extracted bovine incisors were randomly divided into 4 groups of 20, and brackets were bonded under the different experimental conditions. Debonding force was measured with an Instron …
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Evaluation of granular media to wastewater treatment; advanced primary treatment utilising modified pumice, titanomagnetite and ceramic nozzles.
… to 0.18mm). Silicon Sponge is abraded river pumice and was available in two sizes: SS 14/24 (0.6 to 1 mm) and SS 7 /14 (0.4 to 2 mm). The surface of TM grains is smooth and that of SS is highly porous due to the vesiculated structure of pumice, while maintaining a low abrasive factor. In …
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Designing Technosols to reduce salinity and water stress of crops growing under arid conditions : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy of Applied Science in Soil Science at Massey University, Palmerston North, New Zealand
… to plants. Other porous materials, such as pumice, have not yet been considered although pumice has been reported to contribute to water retention under arid conditions. Further potential amendments include organic residues, as they can produce beneficial impacts on plant growth by improving …
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Geotechnical Characterisation of Pumiceous Soils for Liquefaction Assessment
Sands consisting of pumice particles are a common soil type found in several parts of the Waikato Basin and Bay of Plenty in the North Island of New Zealand. The pumice sands are distributed in the area due to powerful historic volcanic eruptions; with subsequent airborne transport and later …
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The oxidation of ethylene to ethylene oxide
… employed and prepared on No.7 and No.3 Valencia pumice as the carrier according to Wiseman. For the analysis of ethylene oxide the procedure employed was a modification of that suggested by Vaughan and Wiseman. The carbon dioxide content of the product gases was determined by absorption of the …
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Dredge spoil dispersion from an inner shelf dump-mound
… tidal delta. Sorting and skewness parameters and pumice content indicate that a lag surface has formed over the dump-site. Natural sediments in the onshore vicinity of the dumpsites have been altered by the deposition of fine sand and pumice after their erosion from the dredge spoil suggesting a …
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Runoff, infiltration and soil erodibility studies in the Otutira catchment
Yellow-brown pumice soils cover a large area of the central North Island of New Zealand. In the Waikato River basin these soils occupy over 7,000km². Since land development started in the mid-1930s approximately 4,000km² have been converted from the native vegetation to exotic forests (1,243km²) …
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Near-vent processes of the 273 ka Poris eruption (Tenerife)
… graded tuff. Hybrid deposition ensued, as coarse pumice fallout and ballistic material entered PDCs to become deposited as a stratified pumice-block tuff. A main phase of PDC activity then occurred, recorded by 9 m of massive lapilli tuff with evidence of widespread scour and bypass, and including …
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Geophysical and geochemical constraints on submarine volcanic processes
… models for the submarine dispersal of giant pumice clasts using observations from the 2012 Havre Volcano eruption. I show that the seafloor distribution of giant pumice is controlled by conductive cooling, the advective displacement of steam by water through highly permeable pathways, and …
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Identification of tephras from the Eastern Mediterranean using solid state techniques
… basin were composed of glass shards, vesicular pumice shards, and mineral fragments. The morphology of the glassy fragments present in the tephras from the Myrtöön and Philippi basins indicates that the eruptions that gave rise to these volcanic deposits were plinian, and that the magmas …
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Desert design : re-thinking the adobe
… and the design presented. Materials such as pumice, wood, stone and concrete are used to understand the different ways materials interact with tile landscape and how they cue experienced in relation to the landscape.
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Electric charge within volcanic plumes on Earth and Io
… 100 µm in diameter, were produced by colliding pumice samples together and were shown to have net specific charges of approximately 10-5 to 10-6 C kg-1 (similar to previous field measurements on ashfall). Most (but not all) of the experimental samples produced net negatively charged ash, and …
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Relationships between the geomechanics and petrography of ignimbrite
… through the groundmass. The size of crystals and pumice clasts controls the concentration of stresses around such inhomogeneities, and hence the initiation of microfractures. However, the proportion of such clasts is not important, so long as a sufficient number are present to initiate …
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Mineralogy and geochemistry associated with hydrothermal alteration of a rhyolitic hyaloclastite from Ponza Island, Italy
… obsidian in a matrix of predominantly pumice lapilli. Incomplete alteration of the hyaloclastite resulted in the non-pervasive argillic zone, characterized by smectite and disordered opal-CT. The other three zones exhibit more complete alteration of the hyaloclastite. The propylitic …
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Dynamics of ash eruptions at Vesuvius
… the periods between the “Avellino” and “Pompeii” Pumice eruptions (AP3, 2,710±60 years B.P.) and after the 512 A.D. eruption, (AS1a). Juvenile fragments from different ash layers throughout the studied stratigraphic sections were fully characterized in terms of external morphology, particle …
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Commonalities in the emplacement of cooling-limited lavas : insights from the 2011-2012 Cordón Caulle rhyolitic eruption
… and inflation processes. Many silicic lavas show pumice diapirs and crease structures at their surface, but such features were rarely observed at Cordón Caulle. The inferred strong surface crust of the Cordón Caulle lava flow, as well as higher viscosity than other rhyolite lava flows, may have …
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