4,594 research outputs found
Holocene-Neogene volcanism in northeastern Australia: chronology and eruption history
Quaternary and late Neogene volcanism is widespread in northeastern Australia, producing at least 397 eruptions covering more than 20,000 km2, including at least 20 flows over 50 km long. Despite this abundance of young volcanism, before this study numerous eruptions had tentative ages or were undated, and the area requires a comprehensive evaluation of eruption patterns through time. To help address these issues we applied multi-collector ARGUS-V 40Ar/39Ar geochronology to determine the age of four of the younger extensive flows: Undara (160 km long, 189 ± 4/4 ka; 2Ï, with full analytical/external uncertainties), Murronga (40 km long, 153 ± 5/5 ka), Toomba (120 km long, 21 ± 3/3 ka), and Kinrara (55 km long, 7 ± 2/2 ka). Verbal traditions of the Gugu Badhun Aboriginal people contain features that may potentially describe the eruption of Kinrara. If the traditions do record this eruption, they would have been passed down for 230 ± 70 generations â a period of time exceeding the earliest written historical records. To further examine north Queensland volcanism through time we compiled a database of 337 ages, including 179 previously unpublished K-Ar and radiocarbon results. The compiled ages demonstrate that volcanic activity has occurred without major time breaks since at least 9 Ma. The greatest frequency of eruptions occurred in the last 2 Ma, with an average recurrence interval of <10â22 ka between eruptions. Activity was at times likely more frequent than these calculations indicate, as the geochronologic dataset is incomplete, with undated eruptions, and intraplate volcanism is often episodic. The duration, frequency, and youthfulness of activity indicate that north Queensland volcanism should be considered as potentially still active, and there are now two confirmed areas of Holocene volcanism in eastern Australia â one at each end of the continent. More broadly, our data provides another example of 40Ar/39Ar geochronology applied to Holocene and latest Pleistocene mafic eruptions, further demonstrating that this method has the ability to examine eruptions and hazards at the youngest volcanoes on Earth
Application of NASTRAN/COSMIC in the analysis of ship structures to underwater explosion shock
The application of NASTRAN/COSMIC in predicting the transient motion of ship structures to underwater, non-contact explosions is discussed. Examples illustrate the finite element models, mathematical formulations of loading functions and, where available, comparisons between analytical and experimental results
In Memoriam: Daniel J. Meltzer
Sedan Ă„r 2006 har den syntetiskt framstĂ€llda drogen spice existerat i Sverige, men först Ă„r 2008 blev drogen populĂ€r och tidningar började rikta uppmĂ€rksamhet mot den. Genom att drogen kan byta skepnad i uppbyggnaden kan den förbli laglig, dĂ€rför kan egentligen namnet âspiceâ inte betraktas som ett enhetligt begrepp. VĂ„rt syfte med denna studie blev att granska hur drogen spice beskrivs i tidningar och forskning. Ăven hur drogen betraktas gĂ€llande psykosociala och medicinska avseenden. Detta i förhĂ„llande till socialkonstruktivistiskt perspektiv. Den metod som vi valde att anvĂ€nda oss av i studien var kvantitativ innehĂ„llsanalys. Genom analys av 80 stycken svenska tidningsartiklar hĂ€mtade ur databasen mediearkivet, samt vetenskapliga artiklar och litteratur har vi besvarat vĂ„ra frĂ„gestĂ€llningar. De resultat vi fick frĂ„n analyser visade pĂ„ att tidningar kan vara av betydande roll för ungdomars attityder. Tidningar kan utföra bland annat skrĂ€mselpropaganda för att upplysa och förhindra brukandet av spice, dessvĂ€rre visar resultatet en motsatt effekt. Forskning visar att bruk av spice kan pĂ„verka relationer och arbete negativt. Dessutom Ă€r nĂ„gra bieffekter av spice bröstsmĂ€rtor, vanförestĂ€llningar, sjĂ€lvmordstankar och hjĂ€rtstopp
Successful treatment of a solitary skull metastasis in a child with Wilms' Tumor
This report presents the successful treatment of a child with a solitary metastatic lesion to the calvarium following treatment for Stage III anaplastic Wilmsâ Tumor
Extraordinarily high biomass benthic community on Southern Ocean seamounts
We describe a previously unknown assemblage of seamount-associated megabenthos that has by far the highest peak biomass reported in the deep-sea outside of vent communities. The assemblage was found at depths of 2-2.5 km on rocky geomorphic features off the southeast coast of Australia, in an area near the Sub-Antarctic Zone characterised by high rates of surface productivity and carbon export to the deep-ocean. These conditions, and the taxa in the assemblage, are widely distributed around the Southern mid-latitudes, suggesting the high-biomass assemblage is also likely to be widespread. The role of this assemblage in regional ecosystem and carbon dynamics and its sensitivities to anthropogenic impacts are unknown. The discovery highlights the lack of information on deep-sea biota worldwide and the potential for unanticipated impacts of deep-sea exploitation
Cooperative Localization for Autonomous Underwater Vehicles
The absence of GPS underwater makes navigation for Autonomous Underwater Vehicles (AUVs) a difficult challenge. Without an external reference in the form of acoustic beacons at known positions, the vehicle has to rely on proprioceptive information obtained through a compass, a Doppler Velocity Logger (DVL) or an Inertial Navigation System (INS). Independent of the quality of the sensors used, the error in the position estimate based on dead-reckoning information grows without bound. Typical navigation errors are 0.5% to 2% of distance traveled for vehicles traveling within a few hundred meters of the sea floor such that their DVL has a lock on the bottom. Errors as low as 0.1% can be obtained with large and expensive INS systems, but for vehicles relying only on a compass and a speed estimate can be as high as 10%. By surfacing the AUV can obtain a position update through its GPS, but this is impossible (under ice) or undesirable for many applications. The use of static beacons in the form of a Long Baseline (LBL) array limits the operation area to a few km2 and requires a substantial deployment effort before operations, especially in deep water. As underwater vehicles become more reliable and affordable the simultaneous use of several AUVs recently became a viable option and multi-vehicle deployments will become standard in the upcoming years. This will not only make entirely new types of missions which rely on cooperation possible, but will also allow each individual member of the group to benefit from navigation information obtained from other members. For optimal cooperative localization a few dedicated Communication and Navigation Aid-AUVs (CNAs), which maintain an accurate estimate of their position through sophisticated DVL and INS sensors, can enable a much larger group of vehicles with less sophisticated navigation suites to maintain an accurate position
Spin-rotor Interpretation of Identical Bands and Quantized Alignment in Superdeformed A 190 Nuclei
The ``identical'' bands in superdeformed mercury, thallium, and lead nuclei
are interpreted as examples of orbital angular momentum rotors with the weak
spin-orbit coupling of pseudo- symmetries and supersymmetries.Comment: 15 pages, revtex 3.0, 7 figures available upon request from
[email protected]
Relative spins and excitation energies of superdeformed bands in 190Hg: Further evidence for octupole vibration
An experiment using the Eurogam Phase II gamma-ray spectrometer confirms the
existence of an excited superdeformed (SD) band in 190Hg and its very unusual
decay into the lowest SD band over 3-4 transitions. The energies and dipole
character of the transitions linking the two SD bands have been firmly
established. Comparisons with RPA calculations indicate that the excited SD
band can be interpreted as an octupole-vibrational structure.Comment: 12 pages, latex, 4 figures available via WWW at
http://www.phy.anl.gov/bgo/bc/hg190_nucl_ex.htm
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