yellowstone hotspot magmatism: Topics by WorldWideScience.org

Periodicity of the Phanerozoic magmatism in Mongolia from potassium-argon data

Basalt and diabase from the Cretaceous Dumisseau Formation, southern Haiti have Mg-numbers of 43-63, TiO/sub 2/ contents of 1.6-3.9% and La abundances of 3.6-15.3 ppm. LaTa ratios average 10, and indicate that the basalts are oceanic in character, distinct from the arc associations forming the northern part of Haiti. Oldest lavas have low TiO/sub 2/, (1.6%) and are LREE-depleted, similar to N-MORBs, whereas overlying lavas have higher TiO/sub 2/ (2-3.9%) and are LREE-enriched, similar to E-MORBs or hotspot basalts. /sup 87/Sr/sup 86/Sr ratios vary from 0.70280 to 0.70316, /sup 143/Nd/sup 144/Nd from 0.512929 to 0.513121, and /sup 206/Pb/sup 204/Pb from 19.00 to 19.27 LREE-depleted lavas have high /sup 143/Nd/sup 144/Nd (0.51309-0.51310) typical of MORBs, whereas /sup 143/Nd/sup 144/Nd in the LREE-enriched lavas varies widely (0.512929-0.513121). Chemical features of the Dumisseau basalts are equivalent to those of Caribbean seafloor basalts recovered on DSDP Leg ...

1988-03-01

USGS Scientists Installing Temperature Sensor

An attempt was made to set the main potassium-argon (PA) boundaries in magmatism development in the territory of Mongolia. Results were correlated with the known concepts about periodicity of magmatism. Possibility of using PA analysis for separation of magmatic rocks was evaluated. Reliable correlation of significant PA boundaries of magmatism with geological periodization of tectonomagmatic events in Mesozoic era and Late Paleozoic era was established.

1989-01-01

USGS Gallery

USGS scientists Laura Clor and Tim Moloney installing a temperature sensor under a public boardwalk in Norris Geyser Basin, Yellowstone National Park....

2010-09-29

The objectives for deep scientific drilling in Yellowstone National Park

Spatio-temporal overlap between Yellowstone bison and elk - implications of wolf restoration and other factors for brucellosis transmission risk

The western area of the United Stated contains three young silicic calderas, all of which contain attractive targets for scientific drilling. Of the three, the Yellowstone caldera complex is the largest, has the most intense geothermal anomalies, and is the most seismically active. On the basis of scientific objectives alone. it is easily the first choice for investigating active hydrothermal processes. This report briefly reviews what is known about the geology of Yellowstone National Park and highlights unique information that could be acquired by research drilling only in Yellowstone. However, it is not the purpose of this report to recommend specific drill sites or to put forth a specific drilling proposal. 175 refs., 9 figs., 2 tabs.

1987-01-01

British Library Electronic Table of Contents (United Kingdom)

Summary 1. In the Greater Yellowstone Ecosystem, bison Bison bison and elk Cervus canadensis nelsoni act as hosts for Brucella abortus. The presence of B. abortus within wildlife populations is an important conservation issue because of the risk of brucellosis transmission from wildlife to cattle. 2. We investigated conditions facilitating contact between bison (40-60% seroprevalence) and elk on a shared winter range in the Madison headwaters area of Yellowstone National Park. We evaluated the effects of snow pack, season, elk and bison population sizes, and wolf Canis lupus predation risk on the degree of spatial overlap between bison and elk from 1991 to 2006. 3. Sixty-eight per cent of 10 093 independent elk observations occurred within the known bison wintering range, 29% occurred with...

2010-01-01

Gray Wolves as Climate Change Buffers in Yellowstone

Ghosts of Yellowstone: Multi-Decadal Histories of Wildlife Populations Captured by Bones on a Modern Landscape

Understanding the mechanisms by which climate and predation patterns by top predators co-vary to affect community structure accrues added importance as humans exert growing influence over both climate...Full Text Available

2005-04-01

Trypanosoma cruzi glycosomal glyceraldehyde-3-phosphate dehydrogenase does not conform to the 'hotspot' topogenic signal model.

Natural accumulations of skeletal material (death assemblages) have the potential to provide historical data on species diversity and population structure for regions lacking decades of wildlife monitoring,...Full Text Available

Performance and Consistency of Indicator Groups in Two Biodiversity Hotspots

The genes which encode glycosomal glyceraldehyde-phosphate dehydrogenase (gGAPDH) of Trypanosoma cruzi are arranged as a tandemly repeated pair on a single chromosome and are identical at the level...Full Text Available

1990-09-01

Microsatellite-based genetic diversity and population structure of domestic sheep in northern Eurasia

BackgroundIn a world limited by data availability and limited funds for conservation, scientists and practitioners must use indicator groups to define spatial conservation priorities....Full Text Available

Mastacembelid eels support Lake Tanganyika as an evolutionary hotspot of diversification

BackgroundIdentification of global livestock diversity hotspots and their importance in diversity maintenance is essential for making global conservation efforts. We screened 52...Full Text Available

Continental-scale magmatic carbon dioxide seepage recorded by dawsonite in the Bowen-Gunnedah-Sydney basin system, eastern Australia

BackgroundLake Tanganyika (LT) is the oldest of the African Rift Lakes and is one of the richest freshwater ecosystems on Earth, with high levels of faunal diversity and endemism....Full Text Available

Reduced exposure to microwave radiation by rats: frequency specific effects

Dawsonite, NaAlCO{sub 3}(OH){sub 2}, is widespread as a cement, replacement, and cavity filling in Permo-Triassic sedimentary rocks of the Bowen-Gunnedah-Sydney basin system eastern Australia. The origin of dawsonite in these rocks was studied by petrographic and stable isotope analysis. Dawsonite {delta}{sup 13}C (PDB) values range from {minus}4.0 to +4.1{per_thousand} and are remarkably consistent throughout the Bowen-Gunnedah-Sydney basin system. These values indicate either a marine carbonate or magmatic source for carbon in the dawsonite. A magmatic carbon source is considered more likely on the basis that (1) evidence of and the cause for widespread marine carbonate dissolution in the sedimentary successions are not apparent, (2) dawsonite is widespread in both marine and nonmarine facies, (3) the region has been the site of major igneous activity, (4) other dawsonite deposits of similar carbon isotopic composition are linked to igneous ...

1995-07-03

What can we learn about extragalactic radio jets from X-ray data?

Previous research has shown that SAR hotspots are induced within the laboratory rat and that the resulting thermal hotspots are not entirely dissipated by bloodflow. Two experiments were conducted to determine if hotspot formation in the body and tail of the rat, which is radiation frequency specific, would have behavioral consequences. In the first experiment rats were placed in a plexiglas cage one side of which, when occupied by the rat, commenced microwave radiation exposure; occupancy of the other side terminated exposure. Groups of rats were tested during a baseline period to determine the naturally preferred side of the cage. Subsequent exposure to 360-MHz, 700-MHz or 2450-MHz microwave radiation was made contingent on preferred-side occupancy. A significant reduction in occupancy of the preferred side of the cage, and hence, microwaves subsequently occurred. Reduced exposure to 360-MHz and 2450-MHz microwaves at 1, ...

1988-01-01

CERN Document Server

We review the current status of resolved X-ray emission associated with extragalactic radio jets and hotspots. The primary question for any particular jet is to decide if the X-rays come from the synchrotron process or from inverse Compton scattering. There is considerable evidence supporting synchrotron emission for knots in the jets of FRI galaxies. For FRII terminal hotspots detected in the X-ray band, synchrotron self-Compton emission continues to provide viable models with one possible exception (so far). Inverse Compton scattering on photons of the cosmic microwave background is indicated for a few powerful jets, and is expected to be an important contributor if not the dominating mechanism for higher redshift objects. The application of a model generally yields physical parameters and in many cases, these include the Doppler boosting factor.

2003-01-01

Land use change in a biofuels hotspot: The case of Iowa, USA

British Library Electronic Table of Contents (United Kingdom)

This study looks at the land use impact of the biofuels expansion on both the intensive and extensive margin, and its environmental consequences. We link economic, geographical and environmental models by using spatially explicit common units of analysis and use remote sensing crop cover maps and digitized soils data as inputs. Land use changes are predicted via economic analysis of crop rotation choice and tillage under alternative crop prices, and the Environmental Policy Integrated Climate (EPIC) model is used to predict corresponding environmental impacts. The study focuses on Iowa, which is the leading biofuels hotspot in the U.S. due to intensive corn production and the high concentration of ethanol plants that comprise 28% of total U.S. production. We consider the impact of the biof...

2011-01-01

Land planarians (Platyhelminthes) as a model organism for fine-scale phylogeographic studies: understanding patterns of biodiversity in the Brazilian Atlantic Forest hotspot

British Library Electronic Table of Contents (United Kingdom)

Abstract The Brazilian Atlantic Forest is one of the richest biodiversity hotspots of the world. Paleoclimatic models have predicted two large stability regions in its northern and central parts, whereas southern regions might have suffered strong instability during Pleistocene glaciations. Molecular phylogeographic and endemism studies show, nevertheless, contradictory results: although some results validate these predictions, other data suggest that paleoclimatic models fail to predict stable rainforest areas in the south. Most studies, however, have surveyed species with relatively high dispersal rates whereas taxa with lower dispersion capabilities should be better predictors of habitat stability. Here, we have used two land planarian species as model organisms to analyse the patterns ...

2011-01-01

Lithology and evolution of the crust-mantle boundary region in the southwestern Basin and Range province

Signature Lipids and Stable Carbon Isotope Analyses of Octopus Spring Hyperthermophilic Communities Compared with Those of Aquificales Representatives

Seismic transects in this area show a strongly reflective Moho of generally low relief, which, in the area of modern transects, consists of a thin zone (< 2 km thick) of short reflectors. The upper mantle is transparent and has a P{sub n} of 7.8-8.0 km/s similar to much of the western US. A lower crustal zone, 2-13 km thick, has variable internal reflectivity and a relatively low velocity of 6.6-6.8 km/s. Upper mantle peridotite xenoliths show both ductile and brittle deformational features and have structures and composition affected by magmatic intrusion; intrusions form complex dike systems and extensive zones of grain boundary infiltration in peridotite xenoliths. Whereas melt infiltration preceded and followed ductile deformation, brittle deformation, represented by closely spaced joint systems and faults, followed ductile deformation and is related to the youngest magmatic episodes. Lower crustal xenoliths are dominantly ...

1990-01-10

Ingestion Pathway Consequences of a Major Release from SRTC

This journal article reports a study originally intended to examine the microbial composition of Octopus Spring and nearby vent biofilms. The article compares the lipid profiles of several genera within the Aquificales as well as measurements of the isotopic carbon fractionation associated with autotrophic and heterotrophic growth of Thermocrinis ruber. Results of the study have led to improved understanding of population structure in the Octopus Spring pink streamer community, a hyperthermophilic chemolithotrophic ecosystem in Yellowstone National Park.

Analysis on uranium resource situations and metallogenic potential of Heyuan mineralization belt of Guangdong province

The food ingestion consequences due to radioactive particulates of an accidental release, scenario 1-RD-3, are evaluated for Savannah River Technology Center. The sizes of land areas requiring the protective action of food interdiction are calculated. The consequences of the particulate portion of the release are evaluated with the HOTSPOT model and an EXCEL spreadsheet for particulates.

1999-06-08

Precious metal enrichment in the Platreef, Bushveld Complex, South Africa: evidence from homogenized magmatic sulfide melt inclusions

Heyuan mineralization belt is a structure-magmatic activities belt which is charcterized by strong plastic deformation and shearing. The squeeze (overthrust) structure is formed early. Later stretch produced slide shovel-shaped normal fault which control the red basin and uranium mineralization. Comprehensive study shows that this area is of favorable uranium metallogenic condition due to the rich uranium source and higher degree of geology work, it is a target for the new round resources exploration. (authors)

2008-03-01

1 2 3

Predatory senescence in ageing wolves

Magmatic sulfide deposits are the most significant source of platinum-group elements (PGE) in the world. Key to understanding their genesis is determining the processes and timing of sulfide saturation, metal enrichment and crustal contamination. In this study, we have identified droplets of magmatic sulfide from the Platreef, South Africa, where droplets of sulfide have been trapped in the earliest crystallising phase, chromite. Due to their early entrapment at high temperatures, metal concentrations and ratios that they display are indicative of a very early-stage sulfide liquid in the system, as they will have cooled and fractionated within an essentially closed system, unlike interstitial blebs that crystallise in an open system as the magma cools. Analysis of these droplets in an opaque mineral like chromite by LA-ICP-MS is problematic as some of the fractionated inclusion is necessarily lost during cutting and polishing to initially ...

2011-06-01

British Library Electronic Table of Contents (United Kingdom)

Abstract It is well established that ageing handicaps the ability of prey to escape predators, yet surprisingly little is known about how ageing affects the ability of predators to catch prey. Research into long-lived predators has assumed that adults have uniform impacts on prey regardless of age. Here we use longitudinal data from repeated observations of individually-known wolves (Canis lupus) hunting elk (Cervus elaphus) in Yellowstone National Park to demonstrate that adult predatory performance declines with age and that an increasing ratio of senescent individuals in the wolf population depresses the rate of prey offtake. Because this ratio fluctuates independently of population size, predatory senescence may cause wolf populations of equal size but different age structure to have d...

2009-01-01

Elk distribution and spatial overlap with livestock during the brucellosis transmission risk period

British Library Electronic Table of Contents (United Kingdom)

Summary 1.-The presence of Brucella abortus within free-ranging wildlife populations is an important conservation and management issue because of the risk of brucellosis transmission between wildlife and livestock. Predicting wildlife distributions is necessary to forecast wildlife and livestock spatial overlap and the potential for brucellosis transmission. 2.-We used Global Positioning System data collected from telemetry-collared female elk Cervus elaphus to develop resource selection function (RSF) models during the brucellosis transmission risk period (the abortion and calving periods). We validated extrapolation of predictive models at two nearby elk ranges within the Greater Yellowstone Ecosystem. Additionally, we integrated extrapolated RSF maps and domestic livestock distributions...

2011-01-01

Body size and predatory performance in wolves: is bigger better?

British Library Electronic Table of Contents (United Kingdom)

Summary Large body size hinders locomotor performance in ways that may lead to trade-offs in predator foraging ability that limit the net predatory benefit of larger size. For example, size-related improvements in handling prey may come at the expense of pursuing prey and thus negate any enhancement in overall predatory performance due to increasing size. This hypothesis was tested with longitudinal data from repeated observations of 94 individually known wolves (Canis lupus) hunting elk (Cervus elaphus) in Yellowstone National Park, USA. Wolf size was estimated from an individually based sex-specific growth model derived from body mass measurements of 304 wolves. Larger size granted individual wolves a net predatory advantage despite substantial variation in its effect on the performance ...

2009-01-01

Surface Topography of 'Hotspot' Regions from a Single Cell SRF Cavity

Spectrum Allocation in Two-Tier Networks

Performance of SRF cavities are limited by non-linear localized effects. The variation of local material characters between "hot" and "cold" spots is thus of intense interest. Such locations were identified in a BCP-etched large-grain single-cell cavity and removed for examination by high resolution electron microscopy (SEM), electron-back scattering diffraction microscopy (EBSD), optical microscopy, and 3D profilometry. Pits with clearly discernable crystal facets were observed in both "hotspot" and "coldspot" specimens. The pits were found in-grain, at bi-crystal boundaries, and on tri-crystal junctions. They are interpreted as etch pits induced by surface crystal defects (e.g. dislocations). All "coldspots" examined had qualitatively low density of etching pits or very shallow tri-crystal boundary junction. EBSD revealed the crystal structure surrounding the pits via crystal phase orientation mapping, while 3D profilometry gave information on the depth and size ...

2009-05-01

CERN Document Server

Two-tier networks, comprising a conventional cellular network overlaid with shorter range hotspots (e.g. femtocells, distributed antennas, or wired relays), offer an economically viable way to improve cellular system capacity. The capacity-limiting factor in such networks is interference. The cross-tier interference between macrocells and femtocells can suffocate the capacity due to the near-far problem, so in practice hotspots should use a different frequency channel than the potentially nearby high-power macrocell users. Centralized or coordinated frequency planning, which is difficult and inefficient even in conventional cellular networks, is all but impossible in a two-tier network. This paper proposes and analyzes an optimum decentralized spectrum allocation policy for two-tier networks that employ frequency division multiple access (including OFDMA). The proposed allocation is optimal in terms of Area Spectral Efficiency (ASE), and is ...

2008-01-01

Caldicellulosiruptor obsidiansis sp. nov., an anaerobic, extremely thermophilic, cellulolytic bacterium isolated from Obsidian Pool, Yellowstone National Park

Proterozoic kimberlites and lamproites and a preliminary age for the Argyle lamproite pipe, Western Australia

A novel, obligately anaerobic, extremely thermophilic, cellulolytic bacterium, designated OB47T, was isolated from Obsidian Pool, Yellowstone National Park, WY, USA. The isolate was a non-motile, non-spore forming, Gram-positive rod approximately 2 m long by 0.2 m wide and grew at temperatures between 55-85oC with the optimum at 78oC. The pH range for growth was 6.0-8.0 with values of near 7.0 being optimal. Growth on cellobiose produced the fastest specific growth rates at 0.75 hr-1. The organism also displayed fermentative growth on glucose, maltose, arabinose, fructose, starch, lactose, mannose, sucrose, galactose, xylose, arabinogalactan, Avicel, xylan, filter paper, processed cardboard, pectin, dilute acid-pretreated switchgrass and Populus. OB47T was unable to grow on mannitol, fucose, lignin, Gelrite, acetate, glycerol, ribose, sorbital, carboxymethylcellulose and casein. Yeast extract stimulated growth and thiosulfate, sulfate, nitrate, and sulfur were not ...

2010-02-01

Gas-dynamic signs of explosive eruptions of volcanoes. 2. Model of homogeneous-heterogeneous nucleation. Specific features of destruction of the cavitating magma

The Argyle pipe occurring in the East Kimberley Province of Western Australia is a unique, highly-diamondiferous lamproite. Although it resembles other lamproites located in the West Kimberley Province with respect to its setting, structure, petrography and geochemistry, it is probably Proterozoic in age and hence substantially older than Tertiary occurrences of the West Kimberley Province. Rb-Sr measurements on whole rock and phlogopite samples from magmatic olivine-phlogopite lamproite, reveals a two point model age of 1126 +- 9 Ma for the Argyle pipe. This age is consistent with ages of other, similar volcanic igneous rocks occurring in several localities worldwide. The widespread occurrence of Proterozoic kimberlites and lamproites suggests that this was an important period of worldwide alkalic intrusive activity.

British Library Electronic Table of Contents (United Kingdom)

The dynamics of state of the crystallite-containing magma is studied within the framework of the gas-dynamic model of bubble cavitation. The effect of crystallites on flow evolution is considered for two cases: where the crystallites are cavitation nuclei (homogeneous-heterogeneous nucleation model) and where large clusters of crystallites are formed in the magma in the period between eruptions. In the first case, decompression jumps are demonstrated to arise as early as in the wave precursor; the intensity of these jumps turns out to be sufficient to form a series of discrete zones of nucleation ahead of the front of the main decompression wave. Results of experimental modeling of an explosive eruption with ejection of crystallite clusters (magmatic ?bombs??) suggest that a cocurrent flow...

2009-01-01

Evaluation of minderal resource potential, Caldera geology, and volcano-tectonic framework at and near Yucca Mountain, Task 3

A Late Holocene explosive mafic eruption of Villarrica volcano, Southern Andes: The Chaimilla deposit

This report summarizes the results of Task 3 work that was initially discussed in our monthly reports for the period October 1, 1992 through September 30, 1993, and contained in our various papers and abstracts, both published and currently in press or in review. Our work during this period was involved (a) the continuation of studies begun prior to October, 1992, focussed mainly on aspects of the caldera geology, volcanic stratigraphy, magmatic activity, hydrothermal mineralization and extensional tectonics of the western and northwestern parts of the southwestern and Nevada volcanic field (SWNVF), studies of the subsurface rocks of Yucca Mountain utilizing drill hole samples obtained in 1991 and 1992, and (b) new studies of veins and siliceous rocks cropping out in northwestern Yucca Mountain that provide evidence for previously unrecognized hydrothermal activity during the Crater Flat Tuff period of volcanism.

1993-09-30

British Library Electronic Table of Contents (United Kingdom)

Villarrica (Chile) is one of the most active volcanoes in South America having erupted about 60 times in the last 460years. Although its historical eruptive activity has been mainly effusive and weakly explosive, it had strong explosive behaviour in postglacial times. Chaimilla (<3.1ka) is one of the best exposed and widely dispersed pyroclastic deposits, related to both fall and flow activity. The deposit is dispersed over an area of 250km^2 and consists of 8 units (A-H) which were grouped into four sequences. Stratigraphic data suggest that the eruption had a relatively short duration and evolved from i) an Opening phase, dispersing ash, lapilli clasts, accretionary lapilli, blocks and bombs, to ii) a Pulsatory phase, originating a series of magmatic explosions, to iii) a Collapsing phas...

2011-01-01

Thermal-hydraulic performance of the GETR emergency cooling system: experimental and analytical considerations

Avian gut-passage effects on seed germination of shrubland species in Mediterranean central Chile

The General Electric Test Reactor emergency cooling system performance was tested by intentionally scramming the reactor and then terminating the power to the primary pump. Certain transient thermal-hydraulic data were obtained preceding and during the established natural convection cooling loop composed of the upward flow through the core and the downward flow through the pool. An analysis was performed to permit the data to be extrapolated to obtain distributed fuel element flow rates and bulk temperature rises during the established cooling loop. The earliest time for the quasi-steady natural cooling loop to develop is about 2.5 min following scram. The cladding hot-spot temperature does not exceed the local saturation temperature after quasi-steady flow is established. Data are presented to assist in the modeling of the GETR natural convection loop. Semi-empirical relationships for friction factor and Nusselt number are also presented.

British Library Electronic Table of Contents (United Kingdom)

Effects of avian gut-passage on seed germination are important to assess the effectiveness of frugivores in woodland regeneration, particularly in biodiversity hotspots that have a high incidence of avian frugivory. We examined the effect of avian gut-passage on seed germination in contrast to seeds that remain uneaten in five shrub species in Mediterranean central Chile and sought to determine the physiological mechanism(s) by which seed germinability is modified. Germination assays were conducted in a glasshouse for five common shrub species of the sub-Andean matorral: Azara dentata (Flacourtiaceae), Schinus polygamus and Schinus molle (Anacardiaceae), Cestrum parqui (Solanaceae), and Maytenus boaria (Celastraceae). We estimated germinability (final percent germination), dormancy length ...

2011-01-01

The platinum group elements and gold: analysis by radiochemical and instrumental neutron activation analysis and relevance to geological exploration and related problems

Evaluation of a process for the decontamination of radioactive hotspots due to activated stellite particles

This paper presents an overview of research conducted with the support of the Australian Institute of Nuclear Science and Engineering, at the University of Melbourne, School of Earth Sciences, Radiochemical Neutron Activation Laboratory. The primary objective of this research is to realize the high potential of the platinum group elements (PGE) and gold to the solution of petrogenetic problems, the study of magma generation and magmatic processes in mafic/ultramafic rock suites, as tracers in hydrothermal ore formation. The PGEs (Os, Ru, Ir, Pt, Pd and Rh) are among the least abundant of all elements on earth with unique properties such as high melting points, high electrical and thermal conductivity, high density, strength and toughness as alloys. They exhibit both siderophile and chalcophile characteristics and are valuable tools in providing information about magmatic processes, in particular S-saturation, as well as crystal fractionation ...

1996-12-31

Geothermal energy in Italy and abroad; La geotermia in Italia e all'estero

Some of the Indian pressurized heavy water reactors (PHWRs) which use Stellite balls in the ball and screw mechanism of the adjustor rod drive mechanism in the moderator circuit have encountered high radiation fields in the moderator system due to "6"0Co. Release of particulate Stellite is responsible for the hotspots in addition to the general uniform contamination of internal surfaces with "6"0Co. Extensive laboratory studies have shown that it is possible to dissolve these Stellite particles by adopting a three-step redox process with permanganic acid as the oxidizing agent. These investigations with inactive Stellite in powder form helped to optimize the process conditions. Permanganic acid was found to have the highest dissolution efficiency as compared to alkaline and nitric acid permanganate. The susceptibility of Stellite to corrode or dissolve was found to depend on the concentration of the permanganate, pH and temperature of the process and microstructure ...

2011-06-01

Geological evolution of the center-southern portion of the Guyana shield based on the geochemical, geochronological and isotopic studies of paleoproterozoic granitoids from southeastern Roraima, Brazil; Evolucao geologica da porcao centro-sul do escudo das Guianas com base no estudo geoquimico, geocronologico e isotopico dos granitoides paleoproterozoicos do sudeste de Roraima, Brasil

Geothermal systems and fields are analysed giving particular evidence to the value of the geothermal source as an important natural source of energy. The paper analyses hydrothermal systems and describes the international experimental studies on the use of geothermal reservoirs in hot rocks with geopressured and magmatic systems. Experts are optimistic as far as the use of this innovative source of energy is possible in the medium-short term. [Italian] Si analizzano i sistemi e i campi geotermici, sottolineando il valore della fonte geotermica come risorsa naturale ragguardevole d'energia. Vengono descritti i sistemi idrotermali e gli esperimenti condotti a livello internazionale sull'utilizzo di serbatoi geotermici in rocce calde con sistemi geopressurizzati e magmatici. L'ottimismo degli esperti sull'utilizzo di questa innovativa sorgente d'energia in tempi medio-brevi.

2001-04-01

Early cretaceous age of orthogneiss from the Charleston Metamorphic Group, New Zealand

This study focuses the granitoids of center-southern portion of Guyana Shield, southeastern Roraima, Brazil. The region is characterized by two tectonic-stratigraphic domains, named as Central Guyana (GCD) and Uatuma-Anaua (UAD) and located probably in the limits of geochronological provinces (e.g. Ventuari-Tapajos or Tapajos-Parima, Central Amazonian and Maroni-Itacaiunas or Transamazon). The aim this doctoral thesis is to provide new petrological and lithostratigraphic constraints on the granitoid rocks and contribute to a better understanding of the origin and geo dynamic evolution of Guyana Shield. The GCD is only locally studied near to the UAD boundary, and new geological data and two single zircon Pb-evaporation ages in mylonitic biotite granodiorite (1.89 Ga) and foliated hastingsite-biotite granite (1.72 Ga) are presented. These ages of the protholiths contrast with the lithostratigraphic picture in the other areas of Cd (1.96-1.93 Ga). Regional mapping, petrography, ...

2006-07-01

Uranium-lead zircon ages from the Median Tectonic Zone, New Zealand

Discordant U-Pb zircon isotopic data from amphibolite facies orthogneisses of the Charleston Metamorphic Group, western South Island, New Zealand, define a lower intercept age of 114#+-#18 m.y. that is interpreted as the crystallization age of the orthogneiss magmas. The upper intercept age of 1026#+-#97 m.y. reflects inherited components of Precambrian zircon derived from the source region of the magmas. The age, and whole rock chemical characteristics, indicate that the orthogneisses are part of the same phase of Early cretaceous magmatic activity that produced voluminous arc-related calc-alkaline plutonic rocks throughout western South Island. Previously published K-Ar and Rb-Sr mineral ages indicate uplift and cooling of the Charleston Metamorphic Group to less than 400deg C by 110-90 m.y. This uplift occurred as a consequence of low-angle normal faulting related to the Late Cretaceous breakup of Gondwana, and suggests that regional continental lithospheric ...

Analysis of forward mutations induced by N-methyl-N'-nitro-N-nitrosoguanidine in the bacteriophage P22 mnt repressor gene

The Median Tectonic Zone (MTZ) of New Zealand is a generally north trending belt of Mesozoic subduction related I-type plutonic, volcanic, and sedimentary rocks in South Island and Stewart Island that separates Permian strata of the Eastern Province Brook Street Terrane from lower to mid Gondwana margin assemblages of the Western Province. High precision isotope dilution U/Pb ages of zircons from 30 rocks are reported. Pre-digestion leaching of zircon in hydrofluoric acid yielded significantly more concordant residues by removing common Pb and dissolving more soluble high-U domains that have been more affected by relatively recent Pb loss. The results show that MTZ magmatism ranges in age from at least Early Triassic to Early Cretaceous (247-131 Ma), with a pronounced gap in the Middle Jurassic. Triassic plutons tend to occur on the eastern side of the MTZ, and they intrude volcanic/sedimentary sequences of the MTZ in Nelson and eastern Fiordland. These sequences ...

Analysis of dose rate build-up in Tarapur Atomic Power Station unit-4

We describe the isolation and genetic characterization of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced mutations in the phage P22 mnt repressor gene cloned in plasmid pBR322. Mutations in the mnt repressor gene or its operator on this plasmid, pPY98, confer a tetracycline resistance phenotype, whereas the wild-type plasmid confers tetracycline sensitivity. Cells carrying pPY98 were briefly exposed to MNNG to give 20 to 40% survival and a 50- to 100-fold increase in tetracycline-resistant cells. DNA sequence analysis showed that 29 to 30 MNNG-induced mutations were GC-to-AT transitions and one was an AT-to-GC transition. About 80% of the mutations are in three hotspots. This mutation spectrum is consistent with the proposed mechanism of mutagenic action of MNNG, which involves mispairing of an alkylated base, O/sup 6/-methylguanine. The mnt gene may be a useful target for determining mutagenic specificity at the nucleotide level because (i) forward ...

1986-04-01

1 2 3

Resource Management in Broadband Communication Networks

Tarapur Atomic Power Station Unit-4 was made critical on 6th March 2005. Since radiation field builds up with the power level due to formation of fission products and activation products in different systems. Radiation dose rates were recorded from different areas using Area Radiation Monitors (ARMs) installed at different areas. These monitors are connected to Radiation Data Acquisition System (RADAS). The trend of radiation field build-up was also analyzed by making survey of different plant areas at various power levels and comparison was made with RADAS readings. The results obtained were compared with 220 MWe dose rates. This study discusses about the dose rates observed at accessible area, shut down accessible area and hotspots observed during the early stage of operation of the reactor. The attempt was also made to find the contributing factors of the high dose rates. It was found that the finding of the study was utilized for the shielding augmentation. ...

2005-11-23

DEFF Research Database (Denmark)

This thesis - Resource Management in Broadband Communication Networks - deals with different ways of optimizing the available resources of data- or telecommunication networks. Especially topics like optimal routing, load balancing and fast recovery of routes in case of link failures are covered. The first part gives a brief description of some of the existing protocols for routing and controlling resources, such as RSVP, OSPF, BGP, PNNI, etc. The remaining part concerns the following two fundamentally different approaches to resource management etc.: - Software agents - Simulated ants In the beginning of the part concerning software agents a description of what exactly constitutes software agents, according to the scientists and according to the organization, FIPA is given. After this, the main results from the IMPACT project are presented. The IMPACT project is an EU-project that aimed at developing a demonstration platform, where software agents handled virtually all aspects of ...

2003-01-01

Thermal and tectonic history of the Ordos Basin, China: Evidence from apatite fission track analysis, vitrinite reflectance, and K-Ar dating

Granitoid formation is ineffective in isotopically homogenizing continental crust: Evidence from archean rocks of the Wind River Mountains, Wyoming

Apatite fission track analysis, vitrinite reflectance data, and K-Ar dating of Permian-Carboniferous and Mesozoic core samples have been successfully integrated to reconstruct the thermal and tectonic history of the Ordos basin, China. Apatite fission track ages of Carboniferous-Jurassic sedimentary rocks range between 3 and 137 Ma, and are significantly younger than the stratigraphic ages. Confined fission track lengths demonstrate exclusively mixed length distribution, indicating complex thermal history. The data suggest that the samples must have all experienced higher paleotemperatures in the past. Mean virtinite reflectance values (R{sub o}) of the Triassic rocks range from 0.61 to 1.06%, giving a high coalification gradient of 0.36%/km and suggesting a high paleothermal gradient of 57{degrees}C/km. Permian-Carboniferous rocks have R{sub o} values on the order of 1.0-3.0%, and locally up to 4.0-6.0%. Some high R{sub o} values coincide with positive gravity and magnetic anomalies. ...

1996-07-01

The Archean core of the Laramide Wind River uplift records evidence of at least three major granitoid-forming episodes. The oldest, the Dry Creek gneiss (DCG), was emplaced by 2.8 Ga and occupies the northeastern part of the range. Mafic, pelitic and ultramafic inclusions occur in the DCG. Elsewhere in the Wind River Mountains there is evidence for crustal components as old as 3.8 Ga. The Bridger batholith (BB), intruded at 2.67 Ga, is found in the west-central Wind River Mountains. The Wind River batholith (WRB) refers to the youngest Late Archean granodiorites and granites which are found throughout the range and includes granitoids previously name the Louis Lake, Bears Ears, Popo Agie, and Middle Mountain intrusions. Although granitoids of the Wind River batholith have been dated at 2.63 and 2.55 Ga, they are considered together here because there is a complete gradation in rock type and because definite intrusive contacts are scarce. The DCG, BB, and WRB each span the ...

1992-01-01

On the Utility of Antiprotons as Drivers for Inertial Confinement Fusion

Earth`s history has been witness to recurrently alternating phases of catastrophic evolution and dominant tectonic deformations, contractions and extension of rifting and spreading leading to quasi-cyclic changes in sedimentary environment and various earth processes. Recent studies have shown quasi-periodicities of 32{+-}2 Million years (Myr) in various endogenic (geomagnetic reversals, magmatic events, mantle convection, various tectonic activities, climate change and biological extinctions) and exogenic (impact catering) processes indicating a remarkable kinship. A time series analysis is presented of the available CO{sub 2} record over the past 250 Myr decoded from global CaCO{sub 3} accumulation rates in sedimentary environment. The time series analysis reveals an intriguing evidence of a dominant periodicity of 33{+-}2 Myr which matches closely with a `common catastrophic periodicity` of 32 Myr identified in various terrestrial and extra-terrestrial records. ...

1998-12-31

Missense mutations in the growth hormone receptor dimerization region in Laron syndrome

By contrast to the large mass, complexity and recirculating power of conventional drivers for inertial confinement fusion (ICF), antiproton annihilation offers a specific energy of 90MJ/{micro}g and thus a unique form of energy packaging and delivery. In principle, antiproton drivers could provide a profound reduction in system mass for advanced space propulsion by ICF. We examine the physics underlying the use of antiprotons ({bar p}) to drive various classes of high-yield ICF targets by the methods of volumetric ignition, hotspot ignition and fast ignition. The useable fraction of annihilation deposition energy is determined for both {bar p}-driven ablative compression and {bar p}-driven fast ignition, in association with 0-D and 1-D target burn models. Thereby, we deduce scaling laws for the number of injected antiprotons required per capsule, together with timing and focal spot requirements. The kinetic energy of the injected antiproton beam required to ...

2003-10-20

Gene expression profiles deciphering rice phenotypic variation between Nipponbare (Japonica) and 93-11 (Indica) during oxidative stress.

Laron syndrome (LS) is an autosomal recessively inherited condition characterized by insensitivity to endogenous and exogenous GH. Affected individuals have severe episodes and other characteristic features. GH receptor gene mutations are present in all affected individuals in whom molecular studies have been reported. The GH receptor is a plasma membrane-spanning protein in which the extracellular domain binds circulating GH and the intracellular domain interacts with the JAK-2 kinase and possibly other intracellular signaling molecules. GH receptor dimerization occurs on GH binding and is thought to be required for normal signal transduction. We have studied the GH receptor genes of four unrelated individuals affected with LS from the United States, Italy, Saudi Arabia, and India. We have identified four different missense mutations that alter consecutive amino acids 152 to 155 in or near the dimerization domain of the GH receptor. One of these mutations, D152H, has been reported ...

1994-09-01

CAV2: A PC-based computer program for predicting incident solar flux distributions inside dish cavity receivers

Rice is a very important food staple that feeds more than half the world's population. Two major Asian cultivated rice (Oryza sativa L.) subspecies, japonica and indica, show significant phenotypic variation in their stress responses. However, the molecular mechanisms underlying this phenotypic variation are still largely unknown. A common link among different stresses is that they produce an oxidative burst and result in an increase of reactive oxygen species (ROS). In this study, methyl viologen (MV) as a ROS agent was applied to investigate the rice oxidative stress response. We observed that 93-11 (indica) seedlings exhibited leaf senescence with severe lesions under MV treatment compared to Nipponbare (japonica). Whole-genome microarray experiments were conducted, and 1,062 probe sets were identified with gene expression level polymorphisms between the two rice cultivars in addition to differential expression under MV treatment, which were assigned as Core Intersectional Probesets ...

2010-01-08

A review of initiatives to reduce energy-related CO_2 emissions from the city of Oxford: past, present and future

The energy flux distribution at the aperture of cavity receivers is an important parameter that characterizes the performance of point-focusing solar concentrators. Together with simplifying assumptions about cavity absorptance, emittance, and convective losses, good estimates of the dish-receiver collection efficiency as a function of incident flux and effective cavity temperature can be obtained. For detailed design of cavity receivers, however, it is necessary to determine the incident flux distribution on the interior surfaces. This information is needed ultimately to determine the resulting energy fluxes to the working fluid, temperature distributions within the cavity, and receiver performance. Knowing the incident flux distributions provides the designer with insights such as where hot-spots are likely to occur, where heat exchange surfaces are needed, and where more detailed analysis might be warranted. Solar receivers are heat exchangers and incident flux ...

1987-02-01

Mineralogical Data of Shocked Quartz Materials from K/T Boundary and Impact Crater

This paper reviews three key initiatives undertaken in the historical city of Oxford to bring about reductions in energy-related CO_2 emissions on a city-wide scale. The author has been part of all the three initiatives. In 2002, a collaborative partnership between academia, industry and city council started the Oxford Solar Initiative (OSI) which uses a community-based approach to help households and organisations in Oxford, financially and technically, to install solar energy systems and energy efficiency measures in buildings. So far OSI has facilitated the installation of 80 active solar systems, over 450 energy efficiency measures and 3,000 low energy bulbs. The scientific basis of OSI is a GIS-based DECoRuM model which estimates and maps baseline energy use and CO_2 emissions on a house-by house level, identifies 'pollution' hotspots, predicts the potential for reductions in CO_2 emissions and monitors reductions achieved as a result of deploying energy ...

2007-06-04