5,950 research outputs found
Could a United States of Europe rival the United States of America?
No full textThis is the archive of a lecture given by Timothy Garton Ash, historian, author, St. Antony's College, Oxford; Respondent: Michael Ignatieff, Director, Carr Center for Human Rights Policy, Kennedy School of Government, Harvard University. Listen to this lecture, which originally aired on WBUR's World of Ideas at http://www.bu.edu/european/2008/04/27/could-a-united-states-of-europe-rival-the-united-states-of-america>
Revision of the age and stratigraphic relationships of Hinemaiaia Tephra and Whakatane Ash, North Island, New Zealand, using distal occurrences in organic deposits
No full textThe stratigraphic and chronologic relationships of Hinemaiaia Tephra and Whakatane Ash are examined using distal tephras preserved in organic-rich deposits at five sites in eastern and northern North Island, New Zealand. A c. 10mm thick, unnamed white rhyolitic ash layer described at two of the sites (Tiniroto and Poukawa), and previously of disputed stratigraphic signillcance, also occurs at the other three sites (Kaipo, Rotomanuka, and Okoroire) as a primary airfall tephra. The tephra is derived from the Taupo Volcanic Centre and is correlated with Hinemaiaia Tephra (definition of Froggatt) using similarity of stratigraphic position, composition (ferromagnesian mineralogy and glass chemistry), and radiocarbon age. It stratigraphically overlies Whakatane Ash. The tephra underlying Whakatane Ash, and previously identified as Hinemaiaia Ash (definition of Vucetich & Pullar), is probably Motutere Tephra.
Hinemaiaia Tephra has a mean age of old (T½) c. 4500 years, Whakatane Ash c. 4800 years. New ¹⁴C dates, obtained on peat or gyttja adjacent to these tephras, are (old T1/2, years B.P.): 4220 ± 60 (NZ316OA), 4490 ± 70 (Wk541)( above Hinemaiaia Tephra); 4470 ± 70 (Wk542) (below Hinemaiaia Tephra); 4800 ± 50 (NZ3161A), 4490 ±60 (Wk496), 4530 ± 60 (Wk497), 4260 ± 140 (Wk662) (below Hinemaiaia Tephra and above Whakatane Ash); 5210 ± 80 (NZ3162A), 4860 ±70 (Wk501), 4850 ± 80 (Wk660) (below Whakatane Ash).
Based on the distal occurrences described here, the Hinemaiaia Tephra has a much more wide spread distribution than previously demonstrated, and may have been emplaced by a very powerful "above average" plinian eruption
Effects of Agricultural Waste Ash on Nutrients Concentration and Yield of Maize (Zea Mays L) in a Haplic Acrisolof Southeastern Nigeria
No full textField trials and a pot experiment were conducted during the 2005 and 2006 cropping seasons at Michael Okpara University of Agriculture, Umudike, Nigeria,to assess the effect of various agricultural wastes ash on nutrient concentration, growth and yield of maize in a Haplic Acrisol. The treatments comprised of palm bunch ash, kitchen residues ash, cocoa pod husk ash, saw dust ash, calcium carbonate, oyster shell ash and a control (without any amendment )
The density, construction and drag coefficient of electrostatic volcanic ash aggregates.
No full textRecent laboratory experiments have demonstrated that electrostatic charges generated during the fragmentation of volcanic pumice cause rapid aggregation of the silicate particles produced. Here, we present measurements of the mass and component particle size distribution of individual, electrostatically bound aggregates produced during these experiments. Particles produced by fracturing pumice aggregated as they fell ∼1.5 m within an enclosed fall chamber. Aggregate mass measurements indicate aggregate densities of ∼200 kg m−3 or less. The component particle size analysis demonstrates exponential-type cumulative distributions which are dominated (on a volume basis) by particles ∼10–40 μm in diameter and contain few particles >70 μm. By representing these particles as disks of 5 μm thickness the calculated aggregate densities are in agreement with those derived from the aggregate mass measurements and indicate a relatively constant aggregate density with size (in contrast with previous results from fall velocities). Combining the density measurements with fall velocity data allows the drag coefficient of aggregates to be determined. Empirical equations developed to describe the particle size distribution within aggregates are used to derive relative aggregation coefficients for the electrostatic aggregation process. Our results can be used within numerical models of volcanic plumes in order to improve their representation of electrostatic aggregation processes
The Faith and Reason of Michael R. Ash
No full textReview of Michael R. Ash. Of Faith and Reason: 80 Evidences Supporting the Prophet Joseph Smith
Carbon pricing, co-pollutants, and climate policy: Evidence from California.
No full textIn a Perspective, James Boyce and Michael Ash discuss Lara Cushing and colleagues' research study on the implications of California's policy on carbon trading
The age of quaternary surfaces at Waihi Beach
No full textThe Waihi Beach surfaces were originally mapped and correlated with European surfaces of similar altitude by Kear and Waterhouse (1961). Exposures along the edges of the surfaces indicate that they are covered with volcanic ashes, the younger of which are of known age. It is the sub-ash surface which should be used for height correlations, and it is the most seaward ash-covered part of the surface which is preferred as the reference point for altitude studies. The heights of the surfaces may not correlate with positions of sea-level at the ages indicated by the ash beds
Surface studies of pulverized fuel ash
No full textThe tendency for pulverized fuel ash (PFA) to be retained on heat transfer surfaces located within coal-fired power station boilers is responsible for several operational difficulties experienced in electricity generation. The mechanisms of ash formation and transport are quite well understood but the factors which lead to ash retention are not. It is believed that the surface composition of ash particles must play a major role in determining their ability to adhere to heat transfer tubes. In order to investigate the outermost regions of ash particles, a series of surface spectroscopic analyses have been carried out, the results and interpretation of which constitute the bulk of the work presented in this thesis. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and secondary ion mass spectrometry (SIMS) have been used in conjunction with energy dispersive X-ray (EDX) analysis to provide information about the distribution and chemical nature of elements within a range of PFA samples. In addition, both AES and SIMS were employed to analyze individual particles, thereby establishing that single particles may have a very different composition from the average obtained for a particular ash. Mossbauer spectroscopy has been used to examine the nature of iron within PFA and a preliminary investigation, using XPS, has also been undertaken into the oxidation in air of heated pyrite, a mineral which has long been implicated in the process of boiler fouling. As a result of these investigations, significant chemical information on a number of elements and trends in their distribution profiles within PFA have been obtained. The findings have been used to examine some fundamental aspects of ash formation and the tendency of ash to adhere to heat transfer surfaces.</p
From Dome to Disease: The Respiratory Toxicity of Volcanic Cristobalite
No full textExposure to fine-grained volcanic ash can potentially cause acute and chronic respiratory disease. The toxicity of ash is likely to vary depending on the type and style of eruption; eruptions at dome-forming volcanoes, in particular, can produce ash containing substantial quantities of respirable crystalline silica, a recognised human carcinogen and causative agent of silicosis. Volcanic domes crystallise crystalline silica as cristobalite, which is metastable at dome-forming temperatures (ca. 850 °C), through deposition from silica-saturated vapours and through devitrification of volcanic glass.
Five dome-forming volcanoes are studied to constrain the hazard posed by volcanic cristobalite, including: Colima, Mexico; Merapi, Indonesia; Mount St. Helens, USA; Santiaguito, Guatemala; and Unzen, Japan. The evolution of the cristobalite hazard is investigated from crystallisation in volcanic settings to its potential effect on biological systems, through a series of petrological, physicochemical and toxicological studies.
We rationalise the presence of metastable cristobalite below its stability field in all domes studied by way of a textural investigation, and conclude that the incorporation of aluminium and sodium into the silica structure facilitates crystallisation. Since particle toxicology is dependent on composition and structure, the observation of cation substitutions is expanded in a geochemical and thermodynamic investigation of volcanic cristobalite to constrain its mineralogy. We find that incorporation of 1-4 wt. % aluminium leads to a poorly-ordered cristobalite structure. This investigation facilitates a mineralogical comparison of the cristobalite hazard among volcanic locations and provides the framework for assessing volcanic cristobalite toxicity. We investigate the ability of volcanic ash to elicit an in vitro pro-inflammatory response, focusing on silica-mediated experiments, and relate the influence of structure and composition to the potential physiological burden. We find that volcanic cristobalite can be mineralogically considered as a single entity among locations, and that cristobalite-bearing ash is less toxic than expected. Nonetheless, we recommend that eruptions be considered on a case-by-case basis to most effectively aid the risk mitigation work of disaster managers globally
An advanced adjustable switch hybrid (Ash) concept for high power automotive converters
No full textIn this paper, we introduce an Adjustable Switch Hybrid (ASH) converter concept. The ASH targets the optimization of the electrical performance of high-powered automotive drive-trains depending on the different load conditions during drive cycles. The new concept employs in principle the previously reported Cross Switch (XS) Hybrid having a parallel arrangement of bipolar Silicon IGBTs and unipolar SiC MOSFETs for benefiting from the different electrical characteristics of each paralleled device. However, the ASH relies on a computational approach for the continuous and dynamic adjustments of the Si-IGBT to the SiC MOSFET area ratio through the gate units depending on the load conditions. In practical terms, changes in the loading conditions can be sensed and data will then be sent back to the ASH gate drive unit for the optimum device ratio selection. In other words, the ASH provides the drivetrain with an Electronic Transmission System or Gear type functionality.Accepted Author ManuscriptDC systems, Energy conversion & Storag
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