Singer, Brad S.; Costa, Fidel; Herrin, Jason S.; Hildreth, Wes; Fierstein, Judith
2016-01-01
The June 6, 1912 eruption of more than 13 km3 of dense rock equivalent (DRE) magma at Novarupta vent, Alaska was the largest of the 20th century. It ejected >7 km3 of rhyolite, ~1.3 km3 of andesite and ~4.6 km3 of dacite. Early ideas about the origin of pyroclastic flows and magmatic differentiation (e.g., compositional zonation of reservoirs) were shaped by this eruption. Despite being well studied, the timing of events that led to the chemically and mineralogically zoned magma reservoir remain poorly known. Here we provide new insights using the textures and chemical compositions of plagioclase and orthopyroxene crystals and by reevaluating previous U-Th isotope data. Compositional zoning of the magma reservoir likely developed a few thousand years before the eruption by several additions of mafic magma below an extant silicic reservoir. Melt compositions calculated from Sr contents in plagioclase fill the compositional gap between 68 and 76% SiO2 in whole pumice clasts, consistent with uninterrupted crystal growth from a continuum of liquids. Thus, our findings support a general model in which large volumes of crystal-poor rhyolite are related to intermediate magmas through gradual separation of melt from crystal-rich mush. The rhyolite is incubated by, but not mixed with, episodic recharge pulses of mafic magma that interact thermochemically with the mush and intermediate magmas. Hot, Mg-, Ca-, and Al-rich mafic magma intruded into, and mixed with, deeper parts of the reservoir (andesite and dacite) multiple times. Modeling the relaxation of the Fe-Mg concentrations in orthopyroxene and Mg in plagioclase rims indicates that the final recharge event occurred just weeks prior to the eruption. Rapid addition of mass, volatiles, and heat from the recharge magma, perhaps aided by partial melting of cumulate mush below the andesite and dacite, pressurized the reservoir and likely propelled a ~10 km lateral dike that allowed the overlying rhyolite to reach the surface.
A compositional tipping point governing the mobilization and eruption style of rhyolitic magma
di Genova, D.; Kolzenburg, S.; Wiesmaier, S.; Dallanave, E.; Neuville, D. R.; Hess, K. U.; Dingwell, D. B.
2017-12-01
The most viscous volcanic melts and the largest explosive eruptions on our planet consist of calcalkaline rhyolites. These eruptions have the potential to influence global climate. The eruptive products are commonly very crystal-poor and highly degassed, yet the magma is mostly stored as crystal mushes containing small amounts of interstitial melt with elevated water content. It is unclear how magma mushes are mobilized to create large batches of eruptible crystal-free magma. Further, rhyolitic eruptions can switch repeatedly between effusive and explosive eruption styles and this transition is difficult to attribute to the rheological effects of water content or crystallinity. Here we measure the viscosity of a series of melts spanning the compositional range of the Yellowstone volcanic system and find that in a narrow compositional zone, melt viscosity increases by up to two orders of magnitude. These viscosity variations are not predicted by current viscosity models and result from melt structure reorganization, as confirmed by Raman spectroscopy. We identify a critical compositional tipping point, independently documented in the global geochemical record of rhyolites, at which rhyolitic melts fluidize or stiffen and that clearly separates effusive from explosive deposits worldwide. This correlation between melt structure, viscosity and eruptive behaviour holds despite the variable water content and other parameters, such as temperature, that are inherent in natural eruptions. Thermodynamic modelling demonstrates how the observed subtle compositional changes that result in fluidization or stiffening of the melt can be induced by crystal growth from the melt or variation in oxygen fugacity. However, the rheological effects of water and crystal content alone cannot explain the correlation between composition and eruptive style. We conclude that the composition of calcalkaline rhyolites is decisive in determining the mobilization and eruption dynamics of Earthā
A compositional tipping point governing the mobilization and eruption style of rhyolitic magma.
Di Genova, D; Kolzenburg, S; Wiesmaier, S; Dallanave, E; Neuville, D R; Hess, K U; Dingwell, D B
2017-12-13
The most viscous volcanic melts and the largest explosive eruptions on our planet consist of calcalkaline rhyolites. These eruptions have the potential to influence global climate. The eruptive products are commonly very crystal-poor and highly degassed, yet the magma is mostly stored as crystal mushes containing small amounts of interstitial melt with elevated water content. It is unclear how magma mushes are mobilized to create large batches of eruptible crystal-free magma. Further, rhyolitic eruptions can switch repeatedly between effusive and explosive eruption styles and this transition is difficult to attribute to the rheological effects of water content or crystallinity. Here we measure the viscosity of a series of melts spanning the compositional range of the Yellowstone volcanic system and find that in a narrow compositional zone, melt viscosity increases by up to two orders of magnitude. These viscosity variations are not predicted by current viscosity models and result from melt structure reorganization, as confirmed by Raman spectroscopy. We identify a critical compositional tipping point, independently documented in the global geochemical record of rhyolites, at which rhyolitic melts fluidize or stiffen and that clearly separates effusive from explosive deposits worldwide. This correlation between melt structure, viscosity and eruptive behaviour holds despite the variable water content and other parameters, such as temperature, that are inherent in natural eruptions. Thermodynamic modelling demonstrates how the observed subtle compositional changes that result in fluidization or stiffening of the melt can be induced by crystal growth from the melt or variation in oxygen fugacity. However, the rheological effects of water and crystal content alone cannot explain the correlation between composition and eruptive style. We conclude that the composition of calcalkaline rhyolites is decisive in determining the mobilization and eruption dynamics of Earth
Zierenberg, R.A.; Schiffman, P.; Barfod, G.H.; Lesher, C.E.; Marks, N.E.; Lowenstern, Jacob B.; Mortensen, A.K.; Pope, E.C.; Bird, D.K.; Reed, M.H.; FriĆ°leifsson, G.O.; Elders, W.A.
2013-01-01
The Iceland Deep Drilling Project Well 1 was designed as a 4- to 5-km-deep exploration well with the goal of intercepting supercritical hydrothermal fluids in the Krafla geothermal field, Iceland. The well unexpectedly drilled into a high-silica (76.5 % SiO2) rhyolite melt at approximately 2.1 km. Some of the melt vesiculated while extruding into the drill hole, but most of the recovered cuttings are quenched sparsely phyric, vesicle-poor glass. The phenocryst assemblage is comprised of titanomagnetite, plagioclase, augite, and pigeonite. Compositional zoning in plagioclase and exsolution lamellae in augite and pigeonite record changing crystallization conditions as the melt migrated to its present depth of emplacement. The in situ temperature of the melt is estimated to be between 850 and 920 Ā°C based on two-pyroxene geothermometry and modeling of the crystallization sequence. Volatile content of the glass indicated partial degassing at an in situ pressure that is above hydrostatic (~16 MPa) and below lithostatic (~55 MPa). The major element and minor element composition of the melt are consistent with an origin by partial melting of hydrothermally altered basaltic crust at depth, similar to rhyolite erupted within the Krafla Caldera. Chondrite-normalized REE concentrations show strong light REE enrichment and relative flat patterns with negative Eu anomaly. Strontium isotope values (0.70328) are consistent with mantle-derived melt, but oxygen and hydrogen isotope values are depleted (3.1 and ā118 ā°, respectively) relative to mantle values. The hydrogen isotope values overlap those of hydrothermal epidote from rocks altered by the meteoric-water-recharged Krafla geothermal system. The rhyolite melt was emplaced into and has reacted with a felsic intrusive suite that has nearly identical composition. The felsite is composed of quartz, alkali feldspar, plagioclase, titanomagnetite, and augite. Emplacement of the rhyolite magma has resulted in partial melting of
Bacon, C.R.; Kurasawa, H.; Delevaux, M.H.; Kistler, R.W.; Doe, B.R.
1984-01-01
The isotopic compositions of Pb and Sr in Pleistocene basalt, high-silica rhyolite, and andesitic inclusions in rhyolite of the Coso volcanic field indicate that these rocks were derived from different levels of compositionally zoned magmatic systems. The 2 earliest rhyolites probably were tapped from short-lived silicic reservoirs, in contrast to the other 36 rhyolite domes and lava flows which the isotopic data suggest may have been leaked from the top of a single, long-lived magmatic system. Most Coso basalts show isotopic, geochemical, and mineralogic evidence of interaction with crustal rocks, but one analyzed flow has isotopic ratios that may represent mantle values (87Sr/86Sr=0.7036,206Pb/204Pb=19.05,207Pb/204Pb=15.62,208Pb/204Pb= 38.63). The (initial) isotopic composition of typical rhyolite (87Sr/86Sr=0.7053,206Pb/204Pb=19.29,207Pb/204Pb= 15.68,208Pb/204Pb=39.00) is representative of the middle or upper crust. Andesitic inclusions in the rhyolites are evidently samples of hybrid magmas from the silicic/mafic interface in vertically zoned magma reservoirs. Silicic end-member compositions inferred for these mixed magmas, however, are not those of erupted rhyolite but reflect the zonation within the silicic part of the magma reservoir. The compositional contrast at the interface between mafic and silicic parts of these systems apparently was greater for the earlier, smaller reservoirs. ?? 1984 Springer-Verlag.
Making rhyolite in a basalt crucible
Eichelberger, John
2016-04-01
Iceland has long attracted the attention of those concerned with the origin of rhyolitic magmas and indeed of granitic continental crust, because it presents no alternative for such magmas other than deriving them from a basaltic source. Hydrothermally altered basalt has been identified as the progenitor. The fact that rhyolite erupts as pure liquid requires a process of melt-crustal separation that is highly efficient despite the high viscosity of rhyolite melt. Volcanoes in Iceland are foci of basaltic magma injection along the divergent plate boundary. Repeated injection produces remelting, digestion, and sometimes expulsion or lateral withdrawal of material resulting in a caldera, a "crucible" holding down-dropped and interlayered lava flows, tephras, and injected sills. Once melting of this charge begins, a great deal of heat is absorbed in the phase change. Just 1% change in crystallinity per degree gives a melt-present body an effective heat capacity >5 times the subsolidus case. Temperature is thus buffered at the solidus and melt composition at rhyolite. Basalt inputs are episodic ("fires") so likely the resulting generation of rhyolite by melting is too. If frequent enough to offset cooling between events, rhyolite melt extractions will accumulate as a rhyolite magma reservoir rather than as discrete crystallized sills. Evidently, such magma bodies can survive multiple firings without themselves erupting, as the 1875 eruption of Askja Caldera of 0.3 km3 of rhyolite equilibrated at 2-km depth without previous leakage over a ten-millennium period and the surprise discovery of rhyolite magma at 2-km depth in Krafla suggest. Water is required for melting; otherwise melting cannot begin at a temperature lower than that of the heat source. Because the solubility of water in melt is pressure-dependent and almost zero at surface pressure, there must be a minimum depth at which basalt-induced melting can occur and a rhyolite reservoir sustained. In practice, the
Steiner, A. R.; Streck, M. J.
2011-12-01
Rhyolitic volcanism associated with the Columbia River-Steens flood basalts of the Pacific Northwest has traditionally been viewed to be centered at McDermitt caldera near the Oregon-Nevada border starting at ~16.5 Ma. In recent years, more rhyolitic centers along this latitude with ages between 16.5-15.5 Ma have been identified and associated with the inception of the Yellowstone hotspot. However the footprint of plume-head related rhyolites becomes much larger when silicic centers of mid-Miocene age in eastern Oregon are included extending the distribution of such rhyolites to areas near the towns of Baker City and John Day ~250 km north of McDermitt. This study addresses one of these rhyolitic centers that was virtually unknown and that constitutes the northwestern extent of mid-Miocene rhyolites. Rhyolites are centered ~40 km SSW of John Day and are considered part of the Strawberry Volcanic Field (SVF), which consists of a diverse group of volcanic rocks ranging from basalt to rhyolite with abundant intermediate compositions. One existing age date of 17.3 Ma Ā± 0.36 (Robyn, 1977) - if confirmed by our ongoing study - places these rhyolites at the very onset of plume-head related rhyolites. Strawberry rhyolitic lavas are most voluminous in the southwestern portion of the SVF covering approximately 500 km2 between Bear and Logan Valley. The rhyolitic lavas tend to be phenocryst-poor (LaN/YbN values ranging from 2.5 to 8.3 and higher values correlate positively with other differentiation indices (e.g. Ba, Sr, Eu/Eu*). Furthermore, major elements (e.g. SiO2 and FeO*) and trace elements (e.g. Ba, Sr, La, Zr/Hf) display common liquid lines of decent with Eu/Eu*. This suggests that the Strawberry Rhyolites are likely products of variable degrees of differentiation. Future petrogenetic evaluations will further investigate the origin of the Strawberry Rhyolites.
Su-Yuen, Hsu
2011-01-01
Textile composite materials have good potential for constructing composite structures where the effects of three-dimensional stresses are critical or geometric complexity is a manufacturing concern. There is a recent interest in advancing competence within Langley Research Center for modeling the degradation of mechanical properties of textile composites. In an initial effort, two critical areas are identified to pursue: (1) Construction of internal geometry of textile composites, and (2) Rate-independent continuum damage mechanics. This report documents reviews on the two subjects. Various reviewed approaches are categorized, their assumptions, methods, and progress are briefed, and then critiques are presented. Each review ends with recommended research.
Stress transfer modeling in CNT reinforced composites using continuum mechanics
International Nuclear Information System (INIS)
Chaboki Khiabani, A.; Sadrnejad, S. A.; Yahyaeii, M.
2008-01-01
Because of the substantial difference in stiffness between matrix and nano tube in CNT composite, the stress transfer between them controls their mechanical properties. This paper investigates the said issue, analytically and numerically, in axial load using representative volume element. The analytical model was established based on the modified Cox's shear lag model with the use of some simplified assumptions. Some, in the developed shear lag model, the CNT assumes hollow fiber. Solving the governing differential equation. led the high shear stress, in interface especially in the CNT cap. In addition, some finite element models were performed with different aspect ratios and the shear stress pattern especially in interface was calculated numerically. Despite some simplified assumptions that were performed with these two models such as elastic behavior and full connectivity, and the comparison of their results with other numerical models show adequate agreement
Permeability of porour rhyolite
Cashman, K.; Rust, A.; Wright, H.; Roberge, J.
2003-04-01
The development of permeability in bubble-bearing magmas determines the efficiency of volatile escape during their ascent through volcanic conduits, which, in turn, controls their explosive potential. As permeability requires bubble connectivity, relationships between permeability and porosity in silicic magmas must be controlled by the formation, growth, deformation and coalescence of their constituent bubbles. Although permeability data on porous volcanic pyroclasts are limited, the database can be greatly extended by including data for ceramic and metallic foams1. Several studies indicate that a single number does not adequately describe the permeability of a foam because inertial effects, which predominate at high flow rates, cause deviations from Darcy's law. These studies suggest that permeability is best modeled using the Forschheimer equation to determine both the Darcy permeability (k1) and the non-Darcian (k2) permeability. Importantly, at the high porosities of ceramic foams (75-95%), both k1 and k2 are strongly dependent on pore size and geometry, suggesting that measurement of these parameters provides important information on foam structure. We determined both the connected porosity (by He-pycnometry) and the permeability (k1 and k2) of rhyolitic samples having a wide range in porosity (22-85%) and vesicle textures. In general, these data support previous observations of a power law relationship between connected porosity and Darcy permeability2. In detail, variations in k1 increase at higher porosities. Similarly, k2 generally increases in both mean and standard deviation with increasing porosity. Measurements made on three mutually perpendicular cores from individual pumice clasts suggest that some of the variability can be explained by anisotropy in the vesicle structure. By comparison with ceramic foams, we suggest that the remaining variability results from differences either in average vesicle size or, more likely, in the size of apertures
Directory of Open Access Journals (Sweden)
Å½mindĆ”k Milan
2018-01-01
Full Text Available It is well that a finite element method is very popular simulation method to predict the physical behavior of systems and structures. In the last years an increase of interest in a new type of numerical methods known as meshless methods was observed. The paper deals with application of radial basis functions on modelling of inelastic damage using continuum damage mechanics of layered plate composite structures reinforced with long unidirectional fibers. For numerical simulations of elastic-plastic damage of layered composite plates own computational programs were implemented in MATLAB programming language. We will use the Newton-Raphson method to solve nonlinear systems of equations. Evaluation damage during plasticity has been solved using return mapping algorithm. The results of elastic-plastic damage analysis of composite plate with unsymmetrical laminate stacking sequence are presented.
Short-circuiting magma differentiation from basalt straight to rhyolite?
Ruprecht, P.; Winslow, H.
2017-12-01
Silicic magmas are the product of varying degrees of crystal fractionation and crustal assimilation/melting. Both processes lead to differentiation that is step-wise rather than continuous for example during melt separation from a crystal mush (Dufek and Bachmann, 2010). However, differentiation is rarely efficient enough to evolve directly from a basaltic to a rhyolitic magma. At VolcĆ”n Puyehue-CordĆ³n Caulle, Chile, the magma series is dominated by crystal fractionation where mixing trends between primitive and felsic end members in the bulk rock compositions are almost absent (e.g. P, FeO, TiO2 vs. SiO2). How effective fraction is in this magmatic system is not well-known. The 2011-12 eruption at CordĆ³n Caulle provides new constraints that rhyolitic melts may be derived directly from a basaltic mush. Minor, but ubiquitous mafic, crystal-rich enclaves co-erupted with the predominantly rhyolitic near-aphyric magma. These enclaves are among the most primitive compositions erupted at Puyehue-CordĆ³n Caulle and geochemically resemble closely basaltic magmas that are >10 ka old (Singer et al. 2008) and that have been identified as a parental tholeiitic mantle-derived magma (Schmidt and Jagoutz, 2017) for the Southern Andean Volcanic Zone. The vesiculated nature, the presence of a microlite-rich groundmass, and a lack of a Eu anomaly in these encalves suggest that they represent recharge magma/mush rather than sub-solidus cumulates and therefore have potentially a direct petrogenetic link to the erupted rhyolites. Our results indicate that under some conditions crystal fractionation can be very effective and the presence of rhyolitic magmas does not require an extensive polybaric plumbing system. Instead, primitive mantle-derived magmas source directly evolved magmas. In the case, of the magma system beneath Puyehue-CordĆ³n Caulle, which had three historic rhyolitic eruptions (1921-22, 1960, 2011-12) these results raise the question whether rhyolite magma extraction
Growth of Megaspherulites In a Rhyolitic Vitrophyre
Smith, Robert K.; Tremallo, Robin L.; Lofgren, Gary E.
2000-01-01
Megaspherulites occur in the middle zone of a thick sequence of rhyolitic vitrophyre that occupies a small, late Eocene to early Oligocene volcanic-tectonic basin near Silver Cliff, Custer County, Colorado. Diameters of the megaspherulites range from 0.3 m to over 3.66 m, including a clay envelope. The megaspherulites are compound spherulites. consisting of an extremely large number (3.8 x 10(exp 9) to 9.9 x 10(exp 9)) of individual growth cones averaging 3 mm long by 1.25 mm wide at their termination. They are holocrystalline, very fine- to fine-grained, composed of disordered to ordered sanidine (orthoclase) and quartz, and surrounded by a thin K-feldspar, quartz rich rind, an inner clay layer with mordenite, and an outer clay layer composed wholly of 15 A montmorillonite. Whole rock analyses of the megaspherulites show a restricted composition from their core to their outer edge, with an average analyses of 76.3% SiO2, 0.34% CaO, 2.17% Na2O, 6.92% K2O, 0.83% H2O+ compared to the rhyolitic vitrophyre from which they crystallize with 71.07% SiO2, 0.57% CaO, 4.06% Na2O,4.l0% K2O, and 6.40% H2O+. The remaining oxides of Fe2O3 (total Fe), A12O3, MnO,MgO, TiO2, P2O5, Cr2O3, and trace elements show uniform distribution between the megaspherulites and the rhyolitic vitrophyre. Megaspherulite crystallization began soon after the rhyolitic lava ceased to flow as the result of sparse heterogeneous nucleation, under nonequilibrium conditions, due to a high degree of undercooling, delta T. The crystals grow with a fibrous habit which is favored by a large delta T ranging between 245 C and 295 C, despite lowered viscosity, and enhanced diffusion due to the high H2O content, ranging between 5% and 7%. Therefore, megaspherulite growth proceeded in a diffusion controlled manner, where the diffusion, rate lags behind the crystal growth rate at the crystal-liquid interface, restricting fibril lengths and diameters to the 10 micron to 15 micron and 3 micron and 8 micron ranges
The impact of dissolved fluorine on bubble nucleation in hydrous rhyolite melts
Gardner, James E.; Hajimirza, Sahand; Webster, James D.; Gonnermann, Helge M.
2018-04-01
Surface tension of hydrous rhyolitic melt is high enough that large degrees of supersaturation are needed to homogeneously nucleate H2O bubbles during eruptive magma ascent. This study examines whether dissolved fluorine lowers surface tension of hydrous rhyolite, and thus lowers the supersaturation required for bubble nucleation. Fluorine was targeted because it, like H2O, changes melt properties and is highly soluble, unlike all other common magmatic volatiles. Rhyolite melts were saturated at Ps = 245 MPa with H2O fluid that contained F, generating rhyolite with 6.7 Ā± 0.4 wt.% H2O and 1.1-1.3 wt.% F. When these melts were decompressed rapidly to Pf = 149-202 MPa and quenched after 60 s, bubbles nucleated at supersaturations of ĪP = Ps - Pf ā„52 MPa, and reached bubble number densities of NB = 1012-13 m-3 at ĪP = 78-101 MPa. In comparison, rhyolite saturated with 6.34 Ā± 0.09 wt.% H2O, but only 0.25 wt.% F, did not nucleate bubbles until ĪP ā„ 100-116 MPa, and even then, at significantly lower NB (<1010 m-3). Numerical modeling of bubble nucleation and growth was used to estimate the values of surface tension required to generate the observed values of NB. Slight differences in melt compositions (i.e., alkalinity and H2O content), H2O diffusivity, or melt viscosity cannot explain the observed differences in NB. Instead, surface tension of F-rich rhyolite must be lower by approximately 4% than that of F-poor rhyolite. This difference in surface tension is significant and, for example, exceeds that found between hydrous basaltic andesite and hydrous rhyolite. These results suggest that is likely that surface tension for F-rich magmas, such as topaz rhyolite, is significantly lower than for F-poor magmas.
Cerro Amarillo rhyolites, advanced AFC in the northern SVZ, Chile
International Nuclear Information System (INIS)
Godoy, E; Hildreth, W
2001-01-01
Cerro Amarillo is a Quaternary medium size (500m high, 2 km 2 ) rhyolite dome complex located close to the Chile-Argentina border, reaching a height of 4162 m, between the headwaters of the Rio Colina and the Nieves Negras Pass. It overlies a broad anticline of thick Middle Jurassic pelites (Alvarez et al., 1997). Thiele (1980) includes this complex in his 'Unidad Volcanica Antigua', a Pleistocene composite map unit made up of andesites and trachyandesites. Ramos et al. (1997), while recognizing its rhyolitic character, assigned a Tertiary age to the lava domes, most likely based on the late Pliocene age of silicic dikes outcropping eastward, in Argentina. Both the lack of younger overlying units and freshness of its components, together with preservation of the unconsolidated, easily eroded pyroclastic deposits at its base, suggest, however, that it is not older than Pleistocene (au)
Coats, Timothy William
1994-01-01
Progressive failure is a crucial concern when using laminated composites in structural design. Therefore the ability to model damage and predict the life of laminated composites is vital. The purpose of this research was to experimentally verify the application of the continuum damage model, a progressive failure theory utilizing continuum damage mechanics, to a toughened material system. Damage due to tension-tension fatigue was documented for the IM7/5260 composite laminates. Crack density and delamination surface area were used to calculate matrix cracking and delamination internal state variables, respectively, to predict stiffness loss. A damage dependent finite element code qualitatively predicted trends in transverse matrix cracking, axial splits and local stress-strain distributions for notched quasi-isotropic laminates. The predictions were similar to the experimental data and it was concluded that the continuum damage model provided a good prediction of stiffness loss while qualitatively predicting damage growth in notched laminates.
Farajpour, M. R.; Shahidi, A. R.; Farajpour, A.
2018-03-01
In this study, the buckling behavior of a three-layered composite nanoplate reinforced with shape memory alloy (SMA) nanowires is examined. Whereas the upper and lower layers are reinforced with typical nanowires, SMA nanoscale wires are used to strengthen the middle layer of the system. The composite nanoplate is assumed to be under the action of biaxial compressive loading. A scale-dependent mathematical model is presented with the consideration of size effects within the context of the Eringenās nonlocal continuum mechanics. Using the one-dimensional Brinsonās theory and the Kirchhoff theory of plates, the governing partial differential equations of SMA nanowire-reinforced hybrid nanoplates are derived. Both lateral and longitudinal deflections are taken into consideration in the theoretical formulation and method of solution. In order to reduce the governing differential equations to their corresponding algebraic equations, a discretization approach based on the differential quadrature method is employed. The critical buckling loads of the hybrid nanosystem with various boundary conditions are obtained with the use of a standard eigenvalue solver. It is found that the stability response of SMA composite nanoplates is strongly sensitive to the small scale effect.
Taylor instability in rhyolite lava flows
Baum, B. A.; Krantz, W. B.; Fink, J. H.; Dickinson, R. E.
1989-01-01
A refined Taylor instability model is developed to describe the surface morphology of rhyolite lava flows. The effect of the downslope flow of the lava on the structures resulting from the Taylor instability mechanism is considered. Squire's (1933) transformation is developed for this flow in order to extend the results to three-dimensional modes. This permits assessing why ridges thought to arise from the Taylor instability mechanism are preferentially oriented transverse to the direction of lava flow. Measured diapir and ridge spacings for the Little and Big Glass Mountain rhyolite flows in northern California are used in conjunction with the model in order to explore the implications of the Taylor instability for flow emplacement. The model suggests additional lava flow features that can be measured in order to test whether the Taylor instability mechanism has influenced the flows surface morphology.
Unified continuum damage model for matrix cracking in composite rotor blades
Energy Technology Data Exchange (ETDEWEB)
Pollayi, Hemaraju; Harursampath, Dineshkumar [Nonlinear Multifunctional Composites - Analysis and Design Lab (NMCAD Lab) Department of Aerospace Engineering Indian Institute of Science Bangalore - 560012, Karnataka (India)
2015-03-10
This paper deals with modeling of the first damage mode, matrix micro-cracking, in helicopter rotor/wind turbine blades and how this effects the overall cross-sectional stiffness. The helicopter/wind turbine rotor system operates in a highly dynamic and unsteady environment leading to severe vibratory loads present in the system. Repeated exposure to this loading condition can induce damage in the composite rotor blades. These rotor/turbine blades are generally made of fiber-reinforced laminated composites and exhibit various competing modes of damage such as matrix micro-cracking, delamination, and fiber breakage. There is a need to study the behavior of the composite rotor system under various key damage modes in composite materials for developing Structural Health Monitoring (SHM) system. Each blade is modeled as a beam based on geometrically non-linear 3-D elasticity theory. Each blade thus splits into 2-D analyzes of cross-sections and non-linear 1-D analyzes along the beam reference curves. Two different tools are used here for complete 3-D analysis: VABS for 2-D cross-sectional analysis and GEBT for 1-D beam analysis. The physically-based failure models for matrix in compression and tension loading are used in the present work. Matrix cracking is detected using two failure criterion: Matrix Failure in Compression and Matrix Failure in Tension which are based on the recovered field. A strain variable is set which drives the damage variable for matrix cracking and this damage variable is used to estimate the reduced cross-sectional stiffness. The matrix micro-cracking is performed in two different approaches: (i) Element-wise, and (ii) Node-wise. The procedure presented in this paper is implemented in VABS as matrix micro-cracking modeling module. Three examples are presented to investigate the matrix failure model which illustrate the effect of matrix cracking on cross-sectional stiffness by varying the applied cyclic load.
Unified continuum damage model for matrix cracking in composite rotor blades
International Nuclear Information System (INIS)
Pollayi, Hemaraju; Harursampath, Dineshkumar
2015-01-01
This paper deals with modeling of the first damage mode, matrix micro-cracking, in helicopter rotor/wind turbine blades and how this effects the overall cross-sectional stiffness. The helicopter/wind turbine rotor system operates in a highly dynamic and unsteady environment leading to severe vibratory loads present in the system. Repeated exposure to this loading condition can induce damage in the composite rotor blades. These rotor/turbine blades are generally made of fiber-reinforced laminated composites and exhibit various competing modes of damage such as matrix micro-cracking, delamination, and fiber breakage. There is a need to study the behavior of the composite rotor system under various key damage modes in composite materials for developing Structural Health Monitoring (SHM) system. Each blade is modeled as a beam based on geometrically non-linear 3-D elasticity theory. Each blade thus splits into 2-D analyzes of cross-sections and non-linear 1-D analyzes along the beam reference curves. Two different tools are used here for complete 3-D analysis: VABS for 2-D cross-sectional analysis and GEBT for 1-D beam analysis. The physically-based failure models for matrix in compression and tension loading are used in the present work. Matrix cracking is detected using two failure criterion: Matrix Failure in Compression and Matrix Failure in Tension which are based on the recovered field. A strain variable is set which drives the damage variable for matrix cracking and this damage variable is used to estimate the reduced cross-sectional stiffness. The matrix micro-cracking is performed in two different approaches: (i) Element-wise, and (ii) Node-wise. The procedure presented in this paper is implemented in VABS as matrix micro-cracking modeling module. Three examples are presented to investigate the matrix failure model which illustrate the effect of matrix cracking on cross-sectional stiffness by varying the applied cyclic load
Romano, Antonio
2010-01-01
This book offers a broad overview of the potential of continuum mechanics to describe a wide range of macroscopic phenomena in real-world problems. Building on the fundamentals presented in the authors' previous book, Continuum Mechanics using Mathematica(R), this new work explores interesting models of continuum mechanics, with an emphasis on exploring the flexibility of their applications in a wide variety of fields.Specific topics, which have been chosen to show the power of continuum mechanics to characterize the experimental behavior of real phenomena, include: * various aspects of nonlin
Drilling into Rhyolitic Magma at Shallow depth at Krafla Volcanic Complex, NE-Iceland
Mortensen, A. K.; MarkĆŗsson, S. H.; Gudmundsson, Ć.; PĆ”lsson, B.
2017-12-01
Krafla volcanic complex in NE-Iceland is an active volcano but the latest eruption was the Krafla Fires in 1975-1984. Though recent volcanic activity has consisted of basaltic fissure eruptions, then it is rhyolitic magma that has been intercepted on at least two occasions while drilling geothermal production wells in the geothermal field suggesting a layered magma plumbing system beneath the Krafla volcanic complex. In 2008 quenched rhyolitic glass was retrieved from the bottom of well KJ-39, which is 2865 m deep ( 2571 m true vertical depth). In 2009 magma was again encountered at an even shallower depth and in more than 2,5 km distance from the bottom of well KJ-39, but in 2009 well IDDP-1 was drilled into magma three times just below 2100 m depth. Only on the last occasion was quenched glass retrieved to confirm that magma had been encountered. In well KJ-39 the quenched glass was rhyolitic in composition. The glass contained resorbed minerals of plagioclase, clinopyroxene and titanomagnetite, but the composition of the glass resembles magma that has formed by partial melting of hydrated basalt. The melt was encountered among cuttings from impermeable, coarse basaltic intrusives at a depth, where the well was anticipated to penetrate the HĆ³lseldar volcanic fissure. In IDDP-1 the quenched glass was also rhyolitic in composition. The glass contained less than 5% of phenocrysts, but the phenocryst assemblage included andesine plagioclase, augite, pigeonite, and titanomagnetite. At IDDP-1 the melt was encountered below a permeable zone composed of fine to coarse grained felsite and granophyre. The disclosure of magma in two wells at Krafla volcanic complex verify that rhyolitic magma can be encountered at shallow depth across a larger area within the caldera. The encounter of magma at shallow depth conforms with that superheated conditions have been found at >2000 m depth in large parts of Krafla geothermal field.
Wang, John T.; Pineda, Evan J.; Ranatunga, Vipul; Smeltzer, Stanley S.
2015-01-01
A simple continuum damage mechanics (CDM) based 3D progressive damage analysis (PDA) tool for laminated composites was developed and implemented as a user defined material subroutine to link with a commercially available explicit finite element code. This PDA tool uses linear lamina properties from standard tests, predicts damage initiation with an easy-to-implement Hashin-Rotem failure criteria, and in the damage evolution phase, evaluates the degradation of material properties based on the crack band theory and traction-separation cohesive laws. It follows Matzenmiller et al.'s formulation to incorporate the degrading material properties into the damaged stiffness matrix. Since nonlinear shear and matrix stress-strain relations are not implemented, correction factors are used for slowing the reduction of the damaged shear stiffness terms to reflect the effect of these nonlinearities on the laminate strength predictions. This CDM based PDA tool is implemented as a user defined material (VUMAT) to link with the Abaqus/Explicit code. Strength predictions obtained, using this VUMAT, are correlated with test data for a set of notched specimens under tension and compression loads.
Pallister, John S.; Diefenbach, Angela K.; Burton, William C.; Munoz, Jorge; Griswold, Julia P.; Lara, Luis E.; Lowenstern, Jacob B.; Valenzuela, Carolina E.
2013-01-01
We use geologic field mapping and sampling, photogrammetric analysis of oblique aerial photographs, and digital elevation models to document the 2008-2009 eruptive sequence at ChaitĆ©n Volcano and to estimate volumes and effusion rates for the lava dome. We also present geochemical and petrologic data that contribute to understanding the source of the rhyolite and its unusually rapid effusion rates. The eruption consisted of five major phases: 1. An explosive phase (1-11 May 2008); 2. A transitional phase (11-31 May 2008) in which low-altitude tephra columns and simultaneous lava extrusion took place; 3. An exogenous lava flow phase (June-September 2008); 4. A spine extrusion and endogenous growth phase (October 2008-February 2009); and 5. A mainly endogenous growth phase that began after the collapse of a prominent PelĆ©ean spine on 19 February 2009 and continued until the end of the eruption (late 2009 or possibly earliest 2010). The 2008-2009 rhyolite lava dome has a total volume of approximately 0.8 km3. The effusion rate averaged 66 m3s-1 during the first two weeks and averaged 45 m3s-1 for the first four months of the eruption, during which 0.5 km3 of rhyolite lava was erupted. These are among the highest rates measured world-wide for historical eruptions of silicic lava. ChaitĆ©nās 2008-2009 lava is phenocryst-poor obsidian and microcrystalline rhyolite with 75.3Ā±0.3% SiO2. The lava was erupted at relatively high temperature and is remarkably similar in composition and petrography to ChaitĆ©nās pre-historic rhyolite. The rhyoliteās normative composition plots close to that of low pressure (100-200 MPa) minimum melts in the granite system, consistent with estimates of approximately 5 to 10 km source depths based on phase equilibria and geodetic studies. Calcic plagioclase, magnesian orthopyroxene and aluminous amphibole among the sparse phenocrysts suggest derivation of the rhyolite by melt extraction from a more mafic magmatic mush. High temperature
Honjo, N.; Bonnichsen, B.; Leeman, W.P.; Stormer, J.C.
1992-01-01
Voluminous mid-Miocene rhyolitic ash-flow tuffs and lava flows are exposed along the northern and southern margins of the central and western Snake River Plain. These rhyolites are essentially anhydrous with the general mineral assemblage of plagioclase ??sanidine ?? quartz + augite + pigeonite ?? hypersthene ?? fayalitic olivine + Fe-Ti oxides + apatite + zircon which provides an opportunity to compare feldspar, pyroxene, and Fe-Ti oxide equilibration temperatures for the same rocks. Estimated pyroxene equilibration temperatures (based on the geothermometers of Lindsley and coworkers) range from 850 to 1000??C, and these are well correlated with whole-rock compositions. With the exception of one sample, agreement between the two-pyroxene thermometers tested is well within 50??C. Fe-Ti oxide geothermometers applied to fresh magnetite and ilmenite generally yield temperatures about 50 to 100??C lower than the pyroxene temperatures, and erratic results are obtained if these minerals exhibit effects of subsolidus oxidation and exsolution. Results of feldspar thermometry are more complicated, and reflect uncertainties in the thermometer calibrations as well as in the degree of attainment of equilibrium between plagioclase and sanidine. In general, temperatures obtained using the Ghiorso (1984) and Green and Usdansky (1986) feldspar thermometers agree with the pyroxene temperatures within the respective uncertainties. However, uncertainties in the feldspar temperatures are the larger of the two (and exceed ??60??C for many samples). The feldspar thermometer of Fuhrman and Lindsley (1988) produces systematically lower temperatures for many of the samples studied. The estimated pyroxene temperatures are considered most representative of actual magmatic temperatures for these rhyolites. This range of temperatures is significantly higher than those for rhyolites from many other suites, and is consistent with the hypothesis that the Snake River Plain rhyolitic magmas formed
Lithium deposits hosted in intracontinental rhyolite calderas
Benson, T. R.; Coble, M. A.; Mahood, G. A.
2017-12-01
Lithium (Li) is classified as a technology-critical element due to the increasing demand for Li-ion batteries, which have a high power density and a relatively low cost that make them optimal for energy storage in mobile electronics, the electrical power grid, and hybrid and electric vehicles. Given that many projections for Li demand exceed current economic reserves and the market is dominated by Australia and Chile, discovery of new domestic Li resources will help diversify the supply chain and keep future technology costs down. Here we show that lake sediments preserved within intracontinental rhyolite calderas have the potential to host Li deposits on par with some of the largest Li brine deposits in the world. We compare Li concentrations of rhyolite magmas formed in a variety of tectonic settings using in situ SHRIMP-RG measurements of homogenized quartz-hosted melt inclusions. Rhyolite magmas that formed within thick, felsic continental crust (e.g., Yellowstone and Hideaway Park, United States) display moderate to extreme Li enrichment (1,500 - 9,000 ppm), whereas magmas formed in thin crust or crust comprised of accreted arc terranes (e.g., Pantelleria, Italy and High Rock, Nevada) contain Li concentrations less than 500 ppm. When the Li-enriched magmas erupt to form calderas, the cauldron depression serves as an ideal catchment within which meteoric water that leached Li from intracaldera ignimbrite, nearby outflow ignimbrite, and caldera-related lavas can accumulate. Additional Li is concentrated in the system through near-neutral, low-temperature hydrothermal fluids circulated along ring fractures as remnant magma solidifies and degasses. Li-bearing hectorite and illite clays form in this alteration zone, and when preserved in the geological record, can lead to a large Li deposit like the 2 Mt Kings Valley Li deposit in the McDermitt Caldera, Nevada. Because more than 100 large Cenozoic calderas occur in the western United States that formed on eruption
Characterization of the rhyolitic rocks from the Lela ore body using neutron activation analysis
International Nuclear Information System (INIS)
Rodriguez, G.C.; Fortes, B.P.; Guevara, S.R.
1998-01-01
Instrumental neutron activation analysis (INAA) is a well-known analytical method for nondestructive, sensitive and accurate determination of elemental composition of geological samples. In the present work twenty-two elements were determined by INAA in nine rhyolitic geological samples from a wolframium ore body Lela, located in the territory of Isla de la Juventud, Cuba. The obtained results are important for the preliminary geochemical evaluation of the studied rocks. (author)
Late Miocene marine tephra beds : recorders of rhyolitic volcanism in North Island, New Zealand
International Nuclear Information System (INIS)
Shane, P.; Black, T.; Eggins, S.; Westgate, J.
1998-01-01
A deep-sea sequence of 72 rhyolitic tephra beds, now exposed at Mahia Peninsula in the Hawke's Bay region of the east coast, North Island, New Zealand, provides a record of Late Miocene volcanism of the Coromandel Volcanic Zone (CVZ): the precursor to large-scale explosive volcanism of the Quaternary Taupo Volcanic Zone (TVZ). The geochemical signature of the glasses in the Miocene tephra has been protected from hydrothermal alteration and prolonged subaerial exposure that have affected proximal CVZ deposits. The tephra beds are primarily eruption-driven sediment gravity flows that have been emplaced into a trench-slope basin, some 300 km from active volcanoes. Their occurrence is consistent with long-distance fluvial transport followed by a point-source discharge into the deep-sea environment, and has no implications for the paleogeographic location of the basins relative to the volcanic arc. The tephra beds are calc-alkaline rhyolites with SiO 2 contents in the range 72-78 wt% (recalculated on a volatile-free basis), and are broadly similar to glassy rocks of the CVZ. Their major oxide, trace element, and REE compositions are indistinguishable from glasses of TVZ rhyolites. The trace element and REE compositional variability in the Late Miocene tephra beds, which were erupted over an estimated duration of c. 0.5-2.4 m.y. is no greater than that of large silicic eruptives of the last 350 ka, and is suggestive of a long-lived source and/or similar magmatic processes. However, the individual tephra beds are products of discrete homogeneous magma batches. New fission track ages of the Miocene tephra beds suggest the main period of volcaniclastic deposition occurred in the interval c. 9-7 Ma. This corresponds well with the initiation of rhyolitic volcanism in the CVZ at c. 10 Ma, and a major period of caldera formation that took place to c. 7 Ma. The ages suggest a sediment accumulation rate of between 0.23 and 1.2 m/ka (av. 0.4 m/ka), and a frequency of eruption of
Spencer, A J M
2004-01-01
The mechanics of fluids and the mechanics of solids represent the two major areas of physics and applied mathematics that meet in continuum mechanics, a field that forms the foundation of civil and mechanical engineering. This unified approach to the teaching of fluid and solid mechanics focuses on the general mechanical principles that apply to all materials. Students who have familiarized themselves with the basic principles can go on to specialize in any of the different branches of continuum mechanics. This text opens with introductory chapters on matrix algebra, vectors and Cartesian ten
Stelten, Mark; Cooper, Kari M.; Vazquez, Jorge A.; Calvert, Andrew T.; Glessner, Justin G
2015-01-01
We constrain the physical nature of the magma reservoir and the mechanisms of rhyolite generation at Yellowstone caldera via detailed characterization of zircon and sanidine crystals hosted in three rhyolites erupted during the (ca. 170 ā 70 ka) Central Plateau Member eruptive episode ā the most recent post-caldera magmatism at Yellowstone. We present 238U-230Th crystallization ages and trace-element compositions of the interiors and surfaces (i.e., unpolished rims) of individual zircon crystals from each rhyolite. We compare these zircon data to 238U- 230Th crystallization ages of bulk sanidine separates coupled with chemical and isotopic data from single sanidine crystals. Zircon age and trace-element data demonstrate that the magma reservoir that sourced the Central Plateau Member rhyolites was long-lived (150 ā 250 kyr) and genetically related to the preceding episode of magmatism, which occurred ca. 256 ka. The interiors of most zircons in each rhyolite were inherited from unerupted material related to older stages of Central Plateau Member magmatism or the preceding late Upper Basin Member magmatism (i.e., are antecrysts). Conversely, most zircon surfaces crystallized near the time of eruption from their host liquids (i.e., are autocrystic). The repeated recycling of zircon interiors from older stages of magmatism demonstrates that sequentially erupted Central Plateau Member rhyolites are genetically related. Sanidine separates from each rhyolite yield 238U-230Th crystallization ages at or near the eruption age of their host magmas, coeval with the coexisting zircon surfaces, but are younger than the coexisting zircon interiors. Chemical and isotopic data from single sanidine crystals demonstrate that the sanidines in each rhyolite are in equilibrium with their host melts, which considered along with their near-eruption crystallization ages suggests that nearly all CPM sanidines are autocrystic. The paucity of antecrystic sanidine crystals relative to
Pamukcu, A. S.; Gualda, G. A.
2013-12-01
Accurately constraining the pressure and temperature of magma residence is problematic, but it is key to understanding the structure and evolution of magmatic systems. Various thermometers exist (Fe-Ti oxides, Ti-in-zircon, Zr-in-sphene, etc.), but there are fewer barometers that can be applied to volcanic rocks. Most barometers capitalize on amphibole, a relatively common mineral whose composition is sensitive to pressure and temperature changes. Glass composition is a function of pressure for magmas saturated in quartz and feldspar, and a new thermobarometer based on rhyolite-MELTS simulations using glass (matrix glass and crystal-hosted glass inclusions) compositions has been recently proposed. We compare results from amphibole and matrix glass thermobarometry. We focus on outflow high-silica rhyolite pumice from the Peach Spring Tuff (CA-NV-AZ, USA), which are characterized by sanidine+plagioclaseĆquartz+amphibole+sphene in a high-silica rhyolite glass matrix. Compositional variations in amphibole are slight and described by edenite and Ti-Tschermak substitution, with little Al-Tschermak substitution, suggesting small changes in temperature but not in pressure. Plagioclase compositions are also nearly homogeneous. Thus, we expect thermobarometry results to cluster around a single pressure and temperature, making these samples excellent candidates for comparing thermobarometers. AmphiboleĆplagioclase thermobarometry reveals: - Amphibole-plagioclase: results vary widely depending on the calibration (e.g. 150-420 MPa, 520-730 Ā°C); combined Anderson & Smith (1995) barometer with Holland & Blundy (1990) thermometer is most consistent, suggesting crystallization at 230 MPa, 680 Ā°C. - Amphibole-only: calibrations give significantly different results (75-115 MPa, 770-960 Ā°C [Ridolfi et al. 2010]; 400-950 MPa, 800-950Ā°C [Ridolfi & Renzulli 2012]). Results suggest the recent re-calibration is particularly unreliable for these rocks, and the earlier calibration is
Kozlovsky, A. M.; Yarmolyuk, V. V.; Savatenkov, V. M.; Kudryashova, E. A.
2017-08-01
A-type rhyolites of contrasting compositions and eruption characters were revealed among two volcanic series of the Early Permian bimodal association in the Nomgon graben. Rhyolites of the lower volcanic series formed extrusions, lava domes, and tuff horizons. They had low FeOt, Zr, Hf, Nb, Ta, Y, and REE concentrations and also a moderately depleted Nd isotope composition (ÉNd( T) = 6.7-7.1). Their formation was related to anatexis of the juvenile continental crust, triggered by the thermal effect of mafic magmas. Rhyolites of the upper volcanic series formed extensive lava flows and dikes. Their composition was characterized by high FeOt, Zr, Hf, Nb, Ta, Y, and REE concentrations, and also depleted Nd isotope characteristics (ÉNd( T) = 7.7-9.0). These rhyolite melts formed under long-term crystallizational differentiation of basaltoids in the intracrustal magmatic chambers, with limited participation of crustal contamination. The source of magmas for the upper volcanic series was the sublithospheric mantle.
238U-230Th dating of chevkinite in high-silica rhyolites from La Primavera and Yellowstone calderas
Vazquez, Jorge A.; Velasco, Noel O.; Schmitt, Axel K.; Bleick, Heather A.; Stelten, Mark E.
2014-01-01
Application of 238U-230Th disequilibrium dating of accessory minerals with contrasting stabilities and compositions can provide a unique perspective on magmatic evolution by placing the thermochemical evolution of magma within the framework of absolute time. Chevkinite, a Th-rich accessory mineral that occurs in peralkaline and metaluminous rhyolites, may be particularly useful as a chronometer of crystallization and differentiation because its composition may reflect the chemical changes of its host melt. Ion microprobeĀ 128U-230Th dating of single chevkinite microphenocrysts from pre- and post-caldera La Primavera, Mexico, rhyolites yields model crystallization ages that are within 10's of k.y. of their corresponding K-Ar ages of ca. 125 ka to 85 ka, while chevkinite microphenocrysts from a post-caldera Yellowstone, USA, rhyolite yield a range of ages from ca. 110 ka to 250 ka, which is indistinguishable from the age distribution of coexisting zircon. Internal chevkinite-zircon isochrons from La Primavera yield Pleistocene ages with ~5% precision due to the nearly two order difference in Th/U between both minerals. Coupling chevkinite 238U-230Th ages and compositional analyses reveals a secular trend of Th/U and rare earth elements recorded in Yellowstone rhyolite, likely reflecting progressive compositional evolution of host magma. The relatively short timescale between chevkinite-zircon crystallization and eruption suggests that crystal-poor rhyolites at La Primavera were erupted shortly after differentiation and/or reheating. These results indicate that 238U-230Th dating of chevkinite via ion microprobe analysis may be used to date crystallization and chemical evolution of silicic magmas.
Zhang, Yuxiang; Zeng, Zhigang; Chen, Shuai; Wang, Xiaoyuan; Yin, Xuebo
2018-06-01
In the middle Okinawa Trough (MOT), rhyolites have been typically considered as products of crystallization differentiation of basaltic magma as a feature of bimodal volcanism. However, the evidence is insufficient. This paper compared chemical trends of volcanic rocks from the MOT with fractional crystallization simulation models and experimental results and utilized trace element modeling combined with Rayleigh fractionation calculations to re-examine fractional crystallization processes in generating rhyolites. Both qualitative and quantitative studies indicate that andesites, rather than rhyolites, originate by fractional crystallization from basalts in the MOT. Furthermore, we established two batch-melting models for the MOT rhyolites and proposed that type 1 rhyolites are produced by remelting of andesites with amphiboles in the residue, while type 2 rhyolites are derived from remelting of andesites without residual amphiboles. It is difficult to produce melts with a SiO2 content ranging from 62% to 68% either by magmatic differentiation from basalts or by remelting of andesites, and this difficulty might help account for the compositional gap (Daly gap) for bimodal volcanism in the Okinawa Trough.
International Nuclear Information System (INIS)
Robinson, R.D.
1985-01-01
This paper reviews the metre-wave continuum radiation which is related to similar solar emissions observed in the decimetre and centimetre spectral regions. This type of emission, known as Flare Contiuum, is related to the radio bursts of types II and IV. After summarising the history of the phenomenon and reviewing the observational work, the author discusses the various possible radiation mechanisms and their relation to the solar corona, the interplanetary medium and related regions. The theoretical topics covered include the role of high-energy particles, the trapping of such particles, gyro-synchrotron radiation, polarization and plasma interactions. (U.K.)
Hertel, Peter
2012-01-01
This smallĀ book on the properties of continuously distributed matter covers a huge field. It sets out the governing principles of continuum physics and illustrates them by carefully chosen examples. These examples comprise structural mechanics and elasticity, fluid media, electricity and optics, thermoelectricity, fluctuation phenomena and more, from Archimedes' principle via Brownian motion to white dwarfs. Metamaterials, pattern formation by reaction-diffusion and surface plasmon polaritons are dealt with as well as classical topics such as Stokes' formula, beam bending and buckling, crystal optics and electro- and magnetooptic effects, dielectric waveguides, Ohm's law, surface acoustic waves, to mention just some. Ā The set of balance equations for content, flow and production of particles, mass, charge, momentum, energy and entropy is augmented by material, or constitutive equations. They describe entire classes of materials, such asĀ viscid fluids and gases, elastic media, dielectrics or electrical con...
Collins, P. C.; Koduri, S.; Dixit, V.; Fraser, H. L.
2018-03-01
The fracture toughness of a material depends upon the material's composition and microstructure, as well as other material properties operating at the continuum level. The interrelationships between these variables are complex, and thus difficult to interpret, especially in multi-component, multi-phase ductile engineering alloys such as Ī±/Ī²-processed Ti-6Al-4V (nominal composition, wt pct). Neural networks have been used to elucidate how variables such as composition and microstructure influence the fracture toughness directly ( i.e., via a crack initiation or propagation mechanism)āand independent of the influence of the same variables influence on the yield strength and plasticity of the material. The variables included in the models and analysis include (i) alloy composition, specifically, Al, V, O, and Fe; (ii) materials microstructure, including phase fractions and average sizes of key microstructural features; (iii) the yield strength and reduction in area obtained from uniaxial tensile tests; and (iv) an assessment of the degree to which plane strain conditions were satisfied by including a factor related to the plane strain thickness. Once trained, virtual experiments have been conducted which permit the determination of each variable's functional dependency on the resulting fracture toughness. Given that the database includes both K 1 C and K Q values, as well as the in-plane component of the stress state of the crack tip, it is possible to quantitatively assess the effect of sample thickness on K Q and the degree to which the K Q and K 1 C values may vary. These interpretations drawn by comparing multiple neural networks have a significant impact on the general understanding of how the microstructure influences the fracture toughness in ductile materials, as well as an ability to predict the fracture toughness of Ī±/Ī²-processed Ti-6Al-4V.
ISOTOPIC COMPOSITION OF HIGH SILICA RHYOLITES IN THE ...
African Journals Online (AJOL)
Mgina
S Manya. Department of Geology, University of Dar es Salaam, P.O. Box 35052 Dar es Salaam ... Victoria. The geological setting for the. Tanzania Craton and its subdivision into the high-grade Dodoman ..... Calculations are based on a decay constant of 6.54 x 10-12 per year for 147Sm and DM values for .... Short Paper.
Educational utilization of outstanding spherulitic rhyolite occurred in Cheongsong, Korea
Jang, Y. D.; Woo, H.
2015-12-01
Cheongsong is located in the central eastern area of South Korea. Unique spherulitic rhyolites occur in this region as dykes formed about 48 to 50 million years ago. Composed of quartz and feldspar these spherulitic rhyolites show various flowerlike shapes, such as chrysanthemum, dandelion, rose, carnation, sunflower, dahlia and so on, so they are called 'flower stones'. The spherulite indicates that it was undercooled caused by very fast cooling at a shallow depth near the surface and the variety of shapes resulted from the difference of crystallizing conditions. According to the condition, minerals start to crystallize homogeneously or heterogeneously and develop as rounded or fibrous shapes, representing beautiful patterns when combined. These spherulitic structures are very rare not only in Korea but also globally, being valuable for research and preservation because of their rarity, beauty and diversity. Cheongsong therefore applies to the UGG (UNESCO Global Geopark) in an attempt to popularize the flower stones and use them as education materials which can also be incorporated in other valuable sites. The exhibition center provides diverse types of flower stones in which visitors could learn about rhyolitic volcanism, crystallization and spherulite and can experience the process of changing a rough stone into a flower stone. A geotrail course has also been created, showing each type of flower stone on the outcrop and providing educational programs about geological mechanisms of the stones with a trained guide.
Tesi, Tommaso; Semiletov, Igor; Hugelius, Gustaf; Dudarev, Oleg; Kuhry, Peter; Gustafsson, Ćrjan
2014-05-01
Climate warming is predicted to translocate terrigenous organic carbon (TerrOC) to the Arctic Ocean and affect the marine biogeochemistry at high latitudes. The magnitude of this translocation is currently unknown, so is the climate response. The fate of the remobilized TerrOC across the Arctic shelves represents an unconstrained component of this feedback. The present study investigated the fate of permafrost carbon along the land-ocean continuum by characterizing the TerrOC composition in three different terrestrial carbon pools from Siberian permafrost (surface organic rich horizon, mineral soil active layer, and Ice Complex deposit) and marine sediments collected on the extensive East Siberian Arctic Shelf (ESAS). High levels of lignin phenols and cutin acids were measured in all terrestrial samples analyzed indicating that these compounds can be used to trace the heterogeneous terrigenous material entering the Arctic Ocean. In ESAS sediments, comparison of these terrigenous biomarkers with other TerrOC proxies (bulk Ī“13C/Ī14C and HMW lipid biomarkers) highlighted contrasting across-shelf trends. These differences could indicate that TerrOC in the ESAS is made up of several pools that exhibit contrasting reactivity toward oxidation during the transport. In this reactive spectrum, lignin is the most reactive, decreasing up to three orders of magnitude from the inner- to the outer-shelf while the decrease of HMW wax lipid biomarkers was considerably less pronounced. Alternatively, degradation might be negligible while sediment sorting during the across-shelf transport could be the major physical forcing that redistributes different TerrOC pools characterized by different matrix-association.
Wang, Chao; Song, Shuguang; Niu, Yaoling; Allen, Mark B.; Su, Li; Wei, Chunjing; Zhang, Guibin; Fu, Bin
2017-11-01
Magmatism in eastern China in response to paleo-Pacific plate subduction during the Mesozoic was complex, and it is unclear how and when exactly the magmas formed via thinning and partial destruction of the continental lithosphere. To better understand this magmatism, we report the results of a geochronological and geochemical study of Early Cretaceous adakitic rhyolite (erupted at 125.4 Ā± 2.2 Ma) in the Xintaimen area within the eastern North China Craton (NCC). In situ zircon U-Pb dating shows that this adakitic rhyolite records a long ( 70 Myrs) and complicated period of magmatism with concordant 206Pb/238U ages from 193 Ma to 117 Ma. The enriched bulk rock Sr-Nd isotopic compositions of the Xintaimen adakitic rhyolite, as well as the enriched zircon Hf and O isotopic compositions, indicate that the magmas parental to the adakitic rhyolite were derived from partial melting of the Paleoproterozoic mafic lower crust, heated by mafic melts derived from the mantle during the paleo-Pacific plate subduction. A minor older basement component is indicated by the presence of captured Neoarchean to Early Paleoproterozoic zircons. The Mesozoic zircons have restricted Hf and O isotopic compositions irrespective of their ages, suggesting that they formed from similar sources at similar melting conditions. The Xintaimen adakitic rhyolite offers an independent line of evidence that the ancient lower crust of eastern China underwent a long period ( 70 Myrs) of destruction, melting or remelting, from 193 to 120 Ma, related to the subduction of the paleo-Pacific plate beneath eastern China.
Argon Diffusion Measured in Rhyolite Melt at 100 MPa
Weldon, N.; Edwards, P. M.; Watkins, J. M.; Lesher, C. E.
2016-12-01
Argon diffusivity (D_{Ar} ) controls the rate and length scale of argon exchange between melt and gas phases and is used as a parameter to model noble gas fractionation during magma degassing. D_{Ar} may also be useful in geochronology to estimate the distribution of excess (non-radiogenic) atmospheric argon in lavas. Our measurements of D_{Ar} in molten anhydrous rhyolite near 1000 Ā°C and 100 MPa add to the existing dataset. Using a rapid-quench cold seal pressure apparatus we exposed cylindrical charges drilled from a Miocene rhyolite flow near Buck Mtn., CA to a pure argon atmosphere resulting in a gradually lengthening argon concentration gradient between the saturated surface and the argon poor interior. Argon concentration was measured by electron microprobe along radial transects from the center to the surface of bisected samples. D_{Ar} was calculated for each transect by fitting relative argon concentration (as a function of distance from the surface) to Green's function (given each experiment's specific temperature, pressure and runtime). Variability (Ļ = 1.202{Ī¼m }^{2} /s) was smaller than in previous studies, but still greater than what is likely due to analytical or experimental uncertainty. We observed a symmetric geometric bias in the distribution of argon in our samples, possibly related to advective redistribution of argon accompanying the deformation of cylindrical charges into spheroids driven by surface tension. Average diffusivity, D_{Ar} = 4.791{Ī¼m }^{2} /s, is close to the predicted value, D_{Ar} = {Ī¼m }^{2} /s ( Ļ_{ \\bar{x} } = 1.576 {Ī¼m }^{2} /s), suggesting that Behrens and Zhang's (2001) empirical model is valid for anhydrous rhyolite melts to relatively higher temperatures and lower pressures. Behrens, H. and Y. Zhang (2001). "Ar diffusion in hydrous silicic melts: implications for volatile diffusion mechanisms and fractionation." Earth and Planetary Science Letters 192: 363-376.
Troch, Juliana; Ellis, Ben S.; Harris, Chris; Ulmer, Peter; Bachmann, Olivier
2018-01-01
Constraining the contribution of crustal lithologies to silicic magmas has important implications for understanding the dynamics of these potentially highly explosive systems. Low-Ī“18O rhyolite lavas erupted after caldera-forming events in Yellowstone have been interpreted as the products of bulk crustal melting of previously deposited and hydrothermally altered rhyolitic material in the down-dropped caldera roof. For lack of compositional data, the "self-cannibalisation bulk melting"-theory relies on the assumption that hydrothermally altered materials are near-cotectic and hydrous (>3 wt% H2O) and will therefore readily melt at temperatures below 850 Ā°C. In this study, we examine the drillcores Y2, Y9 and Y13 from a USGS drilling campaign in Yellowstone in order to characterise the hydrothermally altered material in terms of major and trace elements, oxygen isotopes and water contents. Rhyolite Ī“18O values can decrease from "normal" (+5.8 to +6.1ā°) on the surface to as low as -5ā° at depths of 100-160 m and probably lower as a function of increasing temperature with depth. While material in the drillcores is variably altered and silicified, oxygen isotope exchange in these samples is not accompanied by systematic changes in major and trace element composition and is independent of uptake of water. More than 75% of the drillcore samples have 1100 Ā°C. Therefore, large-scale bulk melting is unrealistic and low-Ī“18O rhyolite magmas more likely result from assimilation of <30% partially melted altered crust with low Ī“18O into a normal-Ī“18O rhyolite magma from the main reservoir. This mechanism is supported by isotopic mass-balance models as well as thermal and volumetric constraints, and may be similarly applicable to other low-Ī“18O settings worldwide.
McCurry, Michael
1988-12-01
The Woods Mountains Volcanic Center is a middle Miocene silicic caldera complex located at the transition from the northern to the southern Basin and Range provinces of the western United States. It consists of a trachyte-trachydacite-rhyolite-peralkaline rhyolite association of lava flows, domes, plugs, pyroclastic rocks, and epiclastic breccia. Volcanism began at about 16.4 Ma, near the end of a local resurgence of felsic to intermediate magmatism and associated crustal extension. Numerous metaluminous high-K trachyte, trachydacite, and rhyolite lava flows, domes, and pyroclastic deposits accumulated from vents scattered over an area of 200 km2 forming a broad volcanic field with an initial volume of about 10 km3. At 15.8 Ma, about 80 km3 of metaluminous to mildly peralkaline high-K rhyolite ash flows were erupted from vents in the western part of fhe field in three closely spaced pulses, resulting in the formation of a trap door caldera 10 km in diameter. The ash flows formed the Wild Horse Mesa Tuff, a compositionally zoned ash flow sheet that originally covered an area of about 600 km2 to a maximum thickness of at least 320 m. High-K trachyte pumice lapilli, some of which are intimately banded with rhyolite, were produced late in the two later eruptions, Intracaldera volcanism from widely distributed vents rapidly filled the caldera with about 10 km3 of high-K, mildly peralkaline, high-silica rhyolite lava flows and pyroclastic deposits. These are interlayered with breccia derived from the caldera scarp. They are intruded by numerous compositionally similar plugs, some of which structurally uplifted and fractured the center of the caldera. The center evolved above a high-K trachyte magma chamber about 10 km in diameter that had developed and differentiated within the upper crust at about 15.8 Ma. Petrological, geochemical, and geophysical data are consistent with the idea that a cap of peralkaline rhyolite magma formed within the trachyte chamber as a result
Continuum mechanics of single-substance bodies
Eringen, A Cemal
1975-01-01
Continuum Physics, Volume II: Continuum Mechanics of Single-Substance Bodies discusses the continuum mechanics of bodies constituted by a single substance, providing a thorough and precise presentation of exact theories that have evolved during the past years. This book consists of three parts-basic principles, constitutive equations for simple materials, and methods of solution. Part I of this publication is devoted to a discussion of basic principles irrespective of material geometry and constitution that are valid for all kinds of substances, including composites. The geometrical notions, k
Ferns, Mark L.; Streck, Martin J.; McClaughry, Jason D.
2017-08-09
The Miocene Columbia River Basalt Group (CRBG) is the youngest and best preserved continental flood basalt province on Earth, linked in space and time with a compositionally diverse succession of volcanic rocks that partially record the apparent emergence and passage of the Yellowstone plume head through eastern Oregon during the late Cenozoic. This compositionally diverse suite of volcanic rocks are considered part of the La Grande-Owyhee eruptive axis (LOEA), an approximately 300-kilometer-long (185 mile), north-northwest-trending, middle Miocene to Pliocene volcanic belt located along the eastern margin of the Columbia River flood basalt province. Volcanic rocks erupted from and preserved within the LOEA form an important regional stratigraphic link between the (1) flood basalt-dominated Columbia Plateau on the north, (2) bimodal basalt-rhyolite vent complexes of the Owyhee Plateau on the south, (3) bimodal basalt-rhyolite and time-transgressive rhyolitic volcanic fields of the Snake River Plain-Yellowstone Plateau, and (4) the High Lava Plains of central Oregon.This field-trip guide describes a 4-day geologic excursion that will explore the stratigraphic and geochemical relationships among mafic rocks of the Columbia River Basalt Group and coeval and compositionally diverse volcanic rocks associated with the early āYellowstone trackā and High Lava Plains in eastern Oregon. Beginning in Portland, the Day 1 log traverses the Columbia River gorge eastward to Baker City, focusing on prominent outcrops that reveal a distal succession of laterally extensive, large-volume tholeiitic flood lavas of the Grande Ronde, Wanapum, and Saddle Mountains Basalt formations of the CRBG. These āgreat flowsā are typical of the well-studied flood basalt-dominated Columbia Plateau, where interbedded silicic and calc-alkaline lavas are conspicuously absent. The latter part of Day 1 will highlight exposures of middle to late Miocene silicic ash-flow tuffs, rhyolite domes, and
Hildreth, W.
1983-01-01
andesite. The zoning ranges of phenocrysts in the rhyolitic and intermediate ejecta do not overlap. New chemical data show the bulk SiO2 range to be: rhyolite 77 ?? 0.6, dacite 66-64.5, and andesite 61.5-58.5%. The dacitic and andesitic ejecta contrast in color and density, and it is not certain whether they form a compositional continuum. Analyses reported by Fenner within the 66-76% SiO2 range were of banded pumice and lava and of bulk tephra that mechanically fractionated and mixed during flight. Despite the gap of 10% SiO2, Fe-Ti-oxide temperatures show a continuous range from rhyolite (805-850??C) through dacite (855-955??C) to andesite (955-990??C). Thermal continuity and isotopic and trace-element data suggest that all were derived from a single magmatic system, whether or not they were physically contiguous before eruption. If the rhyolitic liquid separated from dacitic magma, extraction was so efficient that no dacitic phenocrysts were retained and no bulk compositions in the range 66-76% SiO2 were created; if it were a partial me
The Virtuality Continuum Revisited
Nijholt, Antinus; Traum, D.; Zhai, Sh.; Kellogg, W.
2005-01-01
We survey the themes and the aims of a workshop devoted to the state-of-the-art virtuality continuum. In this continuum, ranging from fully virtual to real physical environments, allowing for mixed, augmented and desktop virtual reality, several perspectives can be taken. Originally, the emphasis
Macdonald, R.; Belkin, H.E.; Fitton, J.G.; Rogers, N.W.; Nejbert, K.; Tindle, A.G.; Marshall, A.S.
2008-01-01
The Greater Olkaria Volcanic Complex is a young (???20 ka) multi-centred lava and dome field dominated by the eruption of peralkaline rhyolites. Basaltic and trachytic magmas have been erupted peripherally to the complex and also form, with mugearites and benmoreites, an extensive suite of magmatic inclusions in the rhyolites. The eruptive rocks commonly represent mixed magmas and the magmatic inclusions are themselves two-, three- or four-component mixes. All rock types may carry xenocrysts of alkali feldspar, and less commonly plagioclase, derived from magma mixing and by remobilization of crystal mushes and/or plutonic rocks. Xenoliths in the range gabbro-syenite are common in the lavas and magmatic inclusions, the more salic varieties sometimes containing silicic glass representing partial melts and ranging in composition from anorthite ?? corundum- to acmite-normative. The peralkaline varieties are broadly similar, in major element terms, to the eruptive peralkaline rhyolites. The basalt-trachyte suite formed by a combination of fractional crystallization, magma mixing and resorption of earlier-formed crystals. Matrix glass in metaluminous trachytes has a peralkaline rhyolitic composition, indicating that the eruptive rhyolites may have formed by fractional crystallization of trachyte. Anomalous trace element enrichments (e.g. ??? 2000 ppm Y in a benmoreite) and negative Ce anomalies may have resulted from various Na- and K-enriched fluids evolving from melts of intermediate composition and either being lost from the system or enriched in other parts of the reservoirs. A small group of nepheline-normative, usually peralkaline, magmatic inclusions was formed by fluid transfer between peralkaline rhyolitic and benmoreitic magmas. The plumbing system of the complex consists of several independent reservoirs and conduits, repeatedly recharged by batches of mafic magma, with ubiquitous magma mixing. ?? The Author 2008. Published by Oxford University Press. All
Chaves, Eduardo W V
2013-01-01
This publication is aimed at students, teachers, and researchers of Continuum Mechanics and focused extensively on stating and developing Initial Boundary Value equations used to solve physical problems. With respect to notation, the tensorial, indicial and Voigt notations have been used indiscriminately. Ā The book is divided into twelve chapters with the following topics: Tensors, Continuum Kinematics, Stress, The Objectivity of Tensors, The Fundamental Equations of Continuum Mechanics, An Introduction to Constitutive Equations, Linear Elasticity, Hyperelasticity, Plasticity (small and large deformations), Thermoelasticity (small and large deformations), Damage Mechanics (small and large deformations), and An Introduction to Fluids. Moreover, the text is supplemented with over 280 figures, over 100 solved problems, and 130 references.
International Nuclear Information System (INIS)
De Almeida, M.; Zerfass, H.; De Lima, L.
1998-01-01
During at the end of Brazilian orogeny cycle (lower Paleozoic), the Camaqua basin was filled by a thick vulcanic series, named Acampamento Velho Formation , which consists of a recurrence of basaltic episodes (at the base) and the alternance of pyroclastic rocks with a rhyolitic composition TBr and Igr) in the intermediate portion and rhyolitic flows (Dr) at the top. Based on the geochemical results, especially on the trace elements such as Zr, Ti, Nb, Y, YB,Th. Ta and the REE., it is confirmed the stratigraphical succession and the depositation chronological order observed in the field. All the volcanic succession presents a behavior pattern typical of post- collisional orogenic, rocks, originated from the crustal contamination of basaltic magmas generated in an environment of the active continental margin. (author)
Computational Continuum Mechanics
Shabana, Ahmed A
2011-01-01
This text presents the theory of continuum mechanics using computational methods. Ideal for students and researchers, the second edition features a new chapter on computational geometry and finite element analysis.
U-Pb ages in meta-rhyolite zircon from Arai Group and associated granites
International Nuclear Information System (INIS)
Pimentel, M.M.; Fuck, R.A.
1991-01-01
Geochronology results by V-Pb method in zircon of granite rocks from staniferous province of Goias and rhyolite Arai groups are revealed. Two distinct episode of acid magmatism in Paleo-and Meso proterozoic are presented. V-Pb data in zircon from Sucuri and Soledade granites of the province from Parana River with ages of higher intercepted are also defined. This ages are consider mistakes, similar the V-Pb age of a rhyolite from Arai group. (author)
Fan, Jian-Jun; Li, Cai; Sun, Zhen-Ming; Xu, Wei; Wang, Ming; Xie, Chao-Ming
2018-04-01
New zircon U-Pb ages, major- and trace-element data, and Hf isotopic compositions are presented for bimodal volcanic rocks of the Zhaga Formation (ZF) in the western-middle segment of the Bangong-Nujiang suture zone (BNSZ), northern Tibet. The genesis of these rocks is described, and implications for late-stage evolution of the Bangong-Nujiang Tethyan Ocean (BNTO) are considered. Detailed studies show that the ZF bimodal rocks, which occur as layers within a typical bathyal to abyssal flysch deposit, comprise MORB-type basalt that formed at a mid-ocean ridge, and low-K calc-alkaline A-type rhyolite derived from juvenile crust. The combination of MORB-type basalt, calc-alkaline A-type rhyolite, and bathyal to abyssal flysch deposits in the ZF leads us to propose that they formed as a result of ridge subduction. The A-type ZF rhyolites yield LA-ICP-MS zircon U-Pb ages of 118-112 Ma, indicating formation during the Early Cretaceous. Data from the present study, combined with regional geological data, indicate that the BNTO underwent conversion from ocean opening to ocean closure during the Late Jurassic-Early Cretaceous. The eastern segment of the BNTO closed during this period, while the western and western-middle segments were still at least partially open and active during the Early Cretaceous, accompanied by ridge subduction within the Bangong-Nujiang Tethyan Ocean.
Introduction to continuum mechanics
Lai, W Michael; Rubin, David
1996-01-01
Introduction to Continuum Mechanics is a recently updated and revised text which is perfect for either introductory courses in an undergraduate engineering curriculum or for a beginning graduate course.Continuum Mechanics studies the response of materials to different loading conditions. The concept of tensors is introduced through the idea of linear transformation in a self-contained chapter, and the interrelation of direct notation, indicial notation, and matrix operations is clearly presented. A wide range of idealized materials are considered through simple static and dynamic problems, a
Fundamentals of continuum mechanics
Rudnicki, John W
2014-01-01
A concise introductory course text on continuum mechanics Fundamentals of Continuum Mechanics focuses on the fundamentals of the subject and provides the background for formulation of numerical methods for large deformations and a wide range of material behaviours. It aims to provide the foundations for further study, not just of these subjects, but also the formulations for much more complex material behaviour and their implementation computationally.Ā This book is divided into 5 parts, covering mathematical preliminaries, stress, motion and deformation, balance of mass, momentum and energ
Hydrothermal alteration of a rhyolitic hyaloclastite from Ponza Island, Italy
Ylagan, Robert F.; Altaner, Stephen P.; Pozzuoli, Antonio
1996-12-01
A rhyolitic hyaloclastite from Ponza island, Italy, has been hydrothermally altered producing four distinct alteration zones based on XRD and field textures: (1) non-pervasive argillic zone; (2) propylitic zone; (3) silicic zone; and (4) sericitic zone. The unaltered hyaloclastite is a volcanic breccia with clasts of vesiculated 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. Obsidian clasts, some pumice lapilli, and pyrogenic plagioclase and biotite are unaltered. Smectite has an irregular flakey morphology, although euhedral particles are occasionally observed. The propylitic zone is characterized by mixed-layer illite/smectite (I/S) with 10 to 85% illite (I), mordenite, opal-C and authigenic K-feldspar (akspar). The matrix of the hyaloclastite is completely altered and obsidian clasts are silicified; however, plagioclase and biotite phenocrysts remain unaltered. Flakey I/S replaces pumice, and mordenite, akspar and silica line and fill pores. I/S particles are composed predominantly of subequant plates and euhedral laths. The silicic zone is characterized by highly illitic I/S with ā„ 90% I, quartz, akspar and occasional albite. In this zone the matrix and clasts are completely altered, and pyrogenic plagioclase shows significant alteration. Illitic I/S has a euhedral lath-like morphology. In the sericitic zone the hyaloclastite altered primarily to illitic I/S with ā„ 66% I, quartz, and minor akspar and pyrite. Clay minerals completely replace pyrogenic feldspars and little evidence remains of the original hyaloclastite texture. Unlike other zones, illitic I/S is fibrous and pure illite samples are composed of euhedral laths and hexagonal plates. The temperatures of hydrothermal alteration likely ranged from 30 to 90 Ā°C for the argillic zone, from 110 to 160 Ā°C for the propylitic zone, from 160 to 270 Ā°C for the
Nonlocal continuum field theories
2002-01-01
Nonlocal continuum field theories are concerned with material bodies whose behavior at any interior point depends on the state of all other points in the body -- rather than only on an effective field resulting from these points -- in addition to its own state and the state of some calculable external field. Nonlocal field theory extends classical field theory by describing the responses of points within the medium by functionals rather than functions (the "constitutive relations" of classical field theory). Such considerations are already well known in solid-state physics, where the nonlocal interactions between the atoms are prevalent in determining the properties of the material. The tools developed for crystalline materials, however, do not lend themselves to analyzing amorphous materials, or materials in which imperfections are a major part of the structure. Nonlocal continuum theories, by contrast, can describe these materials faithfully at scales down to the lattice parameter. This book presents a unif...
Continuum mechanics for engineers
Mase, G Thomas; Mase, George E
2009-01-01
Continuum TheoryContinuum MechanicsStarting OverNotationEssential MathematicsScalars, Vectors and Cartesian TensorsTensor Algebra in Symbolic Notation - Summation ConventionIndicial NotationMatrices and DeterminantsTransformations of Cartesian TensorsPrincipal Values and Principal DirectionsTensor Fields, Tensor CalculusIntegral Theorems of Gauss and StokesStress PrinciplesBody and Surface Forces, Mass DensityCauchy Stress PrincipleThe Stress TensorForce and Moment Equilibrium; Stress Tensor SymmetryStress Transformation LawsPrincipal Stresses; Principal Stress DirectionsMaximum and Minimum Stress ValuesMohr's Circles For Stress Plane StressDeviator and Spherical Stress StatesOctahedral Shear StressKinematics of Deformation and MotionParticles, Configurations, Deformations and MotionMaterial and Spatial CoordinatesLangrangian and Eulerian DescriptionsThe Displacement FieldThe Material DerivativeDeformation Gradients, Finite Strain TensorsInfinitesimal Deformation TheoryCompatibility EquationsStretch RatiosRot...
Introduction to continuum mechanics
Rubin, David; Lai, W Michael
1994-01-01
Continuum mechanics studies the response of materials to different loading conditions. The concept of tensors is introduced through the idea of linear transformation in a self-contained chapter, and the interrelation of direct notation, indicial notation and matrix operations is clearly presented. A wide range of idealized materials are considered through simple static and dynamic problems, and the book contains an abundance of illustrative examples and problems, many with solutions. Through the addition of more advanced material (solution of classical elasticity problems, constitutive e
Rapid ascent of rhyolitic magma at ChaitĆ©n volcano, Chile.
Castro, Jonathan M; Dingwell, Donald B
2009-10-08
Rhyolite magma has fuelled some of the Earth's largest explosive volcanic eruptions. Our understanding of these events is incomplete, however, owing to the previous lack of directly observed eruptions. ChaitĆ©n volcano, in Chile's northern Patagonia, erupted rhyolite magma unexpectedly and explosively on 1 May 2008 (ref. 2). ChaitĆ©n residents felt earthquakes about 24 hours before ash fell in their town and the eruption escalated into a Plinian column. Although such brief seismic forewarning of a major explosive basaltic eruption has been documented, it is unprecedented for silicic magmas. As precursory volcanic unrest relates to magma migration from the storage region to the surface, the very short pre-eruptive warning at ChaitĆ©n probably reflects very rapid magma ascent through the sub-volcanic system. Here we present petrological and experimental data that indicate that the hydrous rhyolite magma at ChaitĆ©n ascended very rapidly, with velocities of the order of one metre per second. Such rapid ascent implies a transit time from storage depths greater than five kilometres to the near surface in about four hours. This result has implications for hazard mitigation because the rapidity of ascending rhyolite means that future eruptions may provide little warning.
Wilson, C. J.; Charlier, B. L.
2007-12-01
The young history of Taupo volcano captures the growth and destruction in the 26.5 ka ca. 530 km3 Oruanui eruption of a large rhyolitic magma body, together with the subsequent rejuvenation of magma sources below the volcano. Integration of field information with petrological and isotopic studies at the whole-pumice and single- crystal scales provide a picture of this history. Several important contrasts are inferred to exist between Taupo and comparably-sized, long-lived silicic foci such at Long Valley and in the Bishop Tuff. At Taupo the following are demonstrable. 1. Even in crystal-poor rhyolites like the Oruanui, many grains are inherited antecrysts or xenocrysts. The Oruanui crystal-poor rhyolite body was an open system, with influxes of crystals (plus melt) from remobilised older crystal mush, melted metasedimentary country rocks and plutonics, and crystal-poor basaltic to andesitic magmas. 2. All the Taupo rhyolites were well mixed prior to eruption, and there are no gradients in the eruption products to suggest that the holding chamber(s) were stratified to any extent. 3. Mafic magmas rose into, interacted with, and ponded on the floors of crystal-poor rhyolite in the Oruanui and Waimihia (3.5 ka) examples, again implying that the chamber floor was sharply defined, not a gradual progression down into a more crystal- rich root zone. 4. Pre-Oruanui activity involved contrasting magma types being generated simultaneously, but erupting from geographically separated vents. Post-Oruanui activity has seen (subtly) contrasting magma groups being erupted from vents in the same geographic area, but separated in time. The Oruanui and post-Oruanui magmas are different and do not appear to be related by consanguinity or by mixing - the Oruanui eruption effectively destroyed its magma body. These features are consistent with rhyolite magma generation at Taupo that is exceptionally fast, driven by high fluxes of mafic magmas into a highly heterogeneous crustal melange
Energy Technology Data Exchange (ETDEWEB)
Tilton, Evan M.; Shull, J. Michael; Danforth, Charles W. [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, 389-UCB, Boulder, CO 80309 (United States); Stevans, Matthew L., E-mail: evan.tilton@colorado.edu, E-mail: michael.shull@colorado.edu, E-mail: charles.danforth@colorado.edu, E-mail: stevans@astro.as.utexas.edu [Department of Astronomy, The University of Texas at Austin, Austin, TX 78712 (United States)
2016-01-20
The rest-frame ultraviolet (UV) spectra of active galactic nuclei (AGNs) are important diagnostics of both accretion disk physics and their contribution to the metagalactic ionizing UV background. Though the mean AGN spectrum is well characterized with composite spectra at wavelengths greater than 912 ā«, the shorter-wavelength extreme-UV (EUV) remains poorly studied. In this third paper in a series on the spectra of AGNs, we combine 11 new spectra taken with the Cosmic Origins Spectrograph on the Hubble Space Telescope with archival spectra to characterize the typical EUV spectral slope of AGNs from Ī»{sub rest}Ā ā¼Ā 850 ā« down to Ī»{sub rest}Ā ā¼Ā 425 ā«. Parameterizing this slope as a power law, we obtain F{sub Ī½}Ā āĀ Ī½{sup ā0.72Ā±0.26}, but we also discuss the limitations and systematic uncertainties of this model. We identify broad emission features in this spectral region, including emission due to ions of O, Ne, Mg, and other species, and we limit the intrinsic He i 504 ā« photoelectric absorption edge opacity to Ļ{sub He} {sub i}Ā <Ā 0.047.
ColĆ³n, Dylan P.; Bindeman, Ilya N.; Wotzlaw, JĆ¶rn-Frederik; Christiansen, Eric H.; Stern, Richard A.
2018-02-01
We present new high-precision CA-ID-TIMS and in situ U-Pb ages together with Hf and O isotopic analyses (analyses performed all on the same grains) from four tuffs from the 15-10 Ma Bruneau-Jarbidge center of the Snake River Plain and from three rhyolitic units from the Kimberly borehole in the neighboring 10-6 Ma Twin Falls volcanic center. We find significant intrasample diversity in zircon ages (ranges of up to 3 Myr) and in Ī“18O (ranges of up to 6ā°) and ÉHf (ranges of up to 24 É units) values. Zircon rims are also more homogeneous than the associated cores, and we show that zircon rim growth occurs faster than the resolution of in situ dating techniques. CA-ID-TIMS dating of a subset of zircon grains from the Twin Falls samples reveals complex crystallization histories spanning 104-106 years prior to some eruptions, suggesting that magma genesis was characterized by the cyclic remelting of buried volcanic rocks and intrusions associated with previous magmatic episodes. Age-dependent trends in zircon isotopic compositions show that rhyolite production in the Yellowstone hotspot track is driven by the mixing of mantle-derived melts (normal Ī“18O and ÉHf) and a combination of Precambrian basement rock (normal Ī“18O and ÉHf down to - 60) and shallow Mesozoic and Cenozoic age rocks, some of which are hydrothermally altered (to low Ī“18O values) by earlier stages of Snake River Plain magmatism. These crustal melts hybridize with juvenile basalts and rhyolites to produce the erupted rhyolites. We also observe that the Precambrian basement rock is only an important component in the erupted magmas in the first eruption at each caldera center, suggesting that the accumulation of new intrusions quickly builds an upper crustal intrusive body which is isolated from the Precambrian basement and evolves towards more isotopically juvenile and lower-Ī“18O compositions over time.
Dynamics of a large, restless, rhyolitic magma system at Laguna del Maule, southern Andes, Chile
Singer, Brad S.; Andersen, Nathan L.; Le MĆ©vel, HĆ©lĆØne; Feigl, Kurt L.; DeMets, Charles; Tikoff, Basil; Thurber, Clifford H.; Jicha, Brian R.; Cardonna, Carlos; CĆ³rdova, Loreto; Gil, Fernando; Unsworth, Martyn J.; Williams-Jones, Glyn; Miller, Craig W.; Fierstein, Judith; Hildreth, Edward; Vazquez, Jorge A.
2014-01-01
Explosive eruptions of large-volume rhyolitic magma systems are common in the geologic record and pose a major potential threat to society. Unlike other natural hazards, such as earthquakes and tsunamis, a large rhyolitic volcano may provide warning signs long before a caldera-forming eruption occurs. Yet, these signsāand what they imply about magma-crust dynamicsāare not well known. This is because we have learned how these systems form, grow, and erupt mainly from the study of ash flow tuffs deposited tens to hundreds of thousands of years ago or more, or from the geophysical imaging of the unerupted portions of the reservoirs beneath the associated calderas. The Laguna del Maule Volcanic Field, Chile, includes an unusually large and recent concentration of silicic eruptions. Since 2007, the crust there has been inflating at an astonishing rate of at least 25 cm/yr. This unique opportunity to investigate the dynamics of a large rhyolitic system while magma migration, reservoir growth, and crustal deformation are actively under way is stimulating a new international collaboration. Findings thus far lead to the hypothesis that the silicic vents have tapped an extensive layer of crystal-poor, rhyolitic melt that began to form atop a magmatic mush zone that was established by ca. 20 ka with a renewed phase of rhyolite eruptions during the Holocene. Modeling of surface deformation, magnetotelluric data, and gravity changes suggest that magma is currently intruding at a depth of ~5 km. The next phase of this investigation seeks to enlarge the sets of geophysical and geochemical data and to use these observations in numerical models of system dynamics.
Gualda, G. A.; Ghiorso, M. S.
2013-12-01
The thermodynamic modeling software MELTS (and its derivatives) is a powerful and much utilized tool for investigating crystallization and melting in natural magmatic systems. Rhyolite-MELTS (Gualda et al. 2012, J. Petrol. 53:875-890) is a recent recalibration of MELTS aimed at better capturing the evolution of magmas present in the upper crust (up to ~400 MPa pressure). Currently, most users of rhyolite-MELTS rely on a graphical user interface (GUI), which can be run on UNIX/LINUX and Mac OS X computers. While the interface is powerful and flexible, it can be somewhat cumbersome for the novice and the output is in the form of text files that need to be processed offline. This situation is probably the main reason why MELTS - despite great potential - has not been used more frequently for teaching purposes. We are currently developing an alternative GUI for rhyolite-MELTS using web services consumed by a VBA backend in Microsoft ExcelĀ©. The goal is to create a much more interactive tool, that is easy to use that can be made available to a widespread audience, and that will be useful for both research and teaching. The interface is contained within a macro-enabled workbook, which includes editable cells where the user can insert the model input information. Interface buttons initiate computations that are executed on a central server at OFM Research in Seattle (WA). Results of simple calculations are shown immediately within the interface itself. For instance, a user can very rapidly determine the temperature at which a magma of a given composition is completely molten (i.e. find the liquidus); or determine which phases are present, in what abundances, their compositions, and their physical properties (e.g. density, viscosity) at any given combination of temperature, pressure and oxygen fugacity. We expect that using the interface in this mode will greatly facilitate building intuition about magmas and their properties. It is also possible to combine a sequence of
International Nuclear Information System (INIS)
Stora, R.
1976-09-01
The mathematics of gauge fields and some related concepts are discussed: some corrections on the principal fiber bundles emphasize the idea that the present formulation of continuum theories is incomplete. The main ingredients used through the construction of the renormalized perturbation series are then described: the Faddeev Popov argument, and the Faddeev Popov Lagrangian; the Slavnov symmetry and the nature of the Faddeev Popov ghost fields; the Slavnov identity, with an obstruction: the Adler Bardeen anomaly, and its generalization to the local cohomology of the gauge Lie algebra. Some smooth classical configurations of gauge fields which ought to play a prominent role in the evaluation of the functional integral describing the theory are also reviewed
Alfven continuum with toroidicity
International Nuclear Information System (INIS)
Riyopoulos, S.; Mahajan, S.M.
1985-06-01
The symmetry property of the MHD wave propagation operator is utilized to express the toroidal eigenmodes as a superposition of the mutually orthogonal cylindrical modes. Because of the degeneracy among cylindrical modes with the same frequency but resonant surfaces of different helicity the toroidal perturbation produces a zeroth order mixing of the above modes. The toroidal eigenmodes of frequency Ļ 0 2 have multiple resonant surfaces, with each surface shifted relative to its cylindrical position and carrying a multispectral content. Thus a single helicity toroidal antenna of frequency Ļ 0 couples strongly to all different helicity resonant surfaces with matching local Alfven frequency. Zeroth order coupling between modes in the continuum and global Alfven modes also results from toroidicity and degeneracy. Our perturbation technique is the MHD counterpart of the quantum mechanical methods and is applicable through the entire range of the MHD spectrum
Lattice continuum and diffusional creep.
Mesarovic, Sinisa Dj
2016-04-01
Diffusional creep is characterized by growth/disappearance of lattice planes at the crystal boundaries that serve as sources/sinks of vacancies, and by diffusion of vacancies. The lattice continuum theory developed here represents a natural and intuitive framework for the analysis of diffusion in crystals and lattice growth/loss at the boundaries. The formulation includes the definition of the Lagrangian reference configuration for the newly created lattice, the transport theorem and the definition of the creep rate tensor for a polycrystal as a piecewise uniform, discontinuous field. The values associated with each crystalline grain are related to the normal diffusional flux at grain boundaries. The governing equations for Nabarro-Herring creep are derived with coupled diffusion and elasticity with compositional eigenstrain. Both, bulk diffusional dissipation and boundary dissipation accompanying vacancy nucleation and absorption, are considered, but the latter is found to be negligible. For periodic arrangements of grains, diffusion formally decouples from elasticity but at the cost of a complicated boundary condition. The equilibrium of deviatorically stressed polycrystals is impossible without inclusion of interface energies. The secondary creep rate estimates correspond to the standard Nabarro-Herring model, and the volumetric creep is small. The initial (primary) creep rate is estimated to be much larger than the secondary creep rate.
Continuum limbed robots for locomotion
Mutlu, Alper
This thesis focuses on continuum robots based on pneumatic muscle technology. We introduce a novel approach to use these muscles as limbs of lightweight legged robots. The flexibility of the continuum legs of these robots offers the potential to perform some duties that are not possible with classical rigid-link robots. Potential applications are as space robots in low gravity, and as cave explorer robots. The thesis covers the fabrication process of continuum pneumatic muscles and limbs. It also provides some new experimental data on this technology. Afterwards, the designs of two different novel continuum robots - one tripod, one quadruped - are introduced. Experimental data from tests using the robots is provided. The experimental results are the first published example of locomotion with tripod and quadruped continuum legged robots. Finally, discussion of the results and how far this technology can go forward is presented.
Continuum mechanics of anisotropic materials
Cowin, Stephen C
2013-01-01
Continuum Mechanics of Anisotropic Materials(CMAM) presents an entirely new and unique development of material anisotropy in the context of an appropriate selection and organization of continuum mechanics topics. These features will distinguish this continuum mechanics book from other books on this subject. Textbooks on continuum mechanics are widely employed in engineering education, however, none of them deal specifically with anisotropy in materials. For the audience of Biomedical, Chemical and Civil Engineering students, these materials will be dealt with more frequently and greater accuracy in their analysis will be desired. Continuum Mechanics of Anisotropic Materials' author has beenĀ a leaderĀ in the field of developing new approaches for the understanding of anisotropic materials.
Continuum robots and underactuated grasping
Directory of Open Access Journals (Sweden)
N. Giri
2011-02-01
Full Text Available We discuss the capabilities of continuum (continuous backbone robot structures in the performance of under-actuated grasping. Continuum robots offer the potential of robust grasps over a wide variety of object classes, due to their ability to adapt their shape to interact with the environment via non-local continuum contact conditions. Furthermore, this capability can be achieved with simple, low degree of freedom hardware. However, there are practical issues which currently limit the application of continuum robots to grasping. We discuss these issues and illustrate via an experimental continuum grasping case study.
This paper was presented at the IFToMM/ASME International Workshop on Underactuated Grasping (UG2010, 19 August 2010, MontrĆ©al, Canada.
Electron paramagnetic resonance of rhyolite and Ī³-irradiated trona minerals
International Nuclear Information System (INIS)
Koeksal, F.; Koeseoglu, R.; Basaran, E.
2003-01-01
Rhyolite from the ''Yellow Stone of Nevsehir'' and Ī³-irradiated trona from the Ankara Mine have been investigated by electron paramagnetic resonance at ambient temperature and at 113 K. Rhyolite was examined by X-ray powder diffraction and found to consist mainly of SiO 2 . Before Ī³-irradiation, the existing paramagnetic species in rhyolite were identified as PO 4 2- , CH 2 OH, CO 3 - , SO 2 - , CO 3 3- , and CO 2 - free radicals and Fe 3+ at ambient temperature. At 113 K SO 2 - , CO 3 3- , and CO 2 - radicals and Fe 3+ were observed. The Ī³-irradiation produced neither new species nor detectable effects on these free radicals. The disappearance of some of the radicals at 113 K is attributed to the freezing of their motions. Before Ī³-irradiation, the trona mineral shows only Mn 2+ lines, but after Ī³-irradiation it indicated the inducement of CO 3 3- and CO 2 - radicals at ambient temperature, 113 K, in addition to the Mn 2+ lines. The g and a values of the species were determined. (orig.)
The petrologic evolution and pre-eruptive conditions of the rhyolitic Kos Plateau Tuff (Aegean arc)
Bachmann, Olivier
2010-09-01
The Kos Plateau Tuff is a large (>60 km3) and young (160 k.y.) calc-alkaline, high-SiO2 rhyolitic ignimbrite from the active Kos-Nisyros volcanic center in the Aegean arc (Greece). Combined textural, petrological and geochemical information suggest that (1) the system evolved dominantly by crystal fractionation from (mostly unerupted) more mafic parents, (2) the magma chamber grew over ā„ 250 000 years at shallow depth (Ė1.5-2.5 kb) and was stored as a H2O-rich crystalline mush close to its solidus (Ė670-750Ā°C), (3) the eruption occurred after a reheating event triggered by the intrusion of hydrous mafic magma at the base of the rhyolitic mush. Rare banded pumices indicate that the mafic magma only mingled with a trivial portion of resident crystal-rich rhyolite; most of the mush was remobilized following partial melting of quartz and feldspars induced by advection of heat and volatiles from the underplated, hotter mafic influx.
The continuum of behavior guidance.
Nelson, Travis
2013-01-01
Behavior guidance is a continuum of techniques, basic and advanced, fundamental to the provision of quality dental care for pediatric patients. This practice must be individualized, pairing the correct method of behavior guidance with each child. To select the appropriate technique, the clinician must have a thorough understanding of each aspect of the continuum and anticipate parental expectations, child temperament, and the technical procedures necessary to complete care. By effectively using techniques within the continuum of behavior guidance, a healing relationship with the family is maintained while addressing dental disease and empowering the child to receive dental treatment throughout their lifetime. Copyright Ā© 2013 Elsevier Inc. All rights reserved.
Rhyolites associated to Ethiopian CFB: Clues for initial rifting at the Afar plume axis
Natali, Claudio; Beccaluva, Luigi; Bianchini, Gianluca; Siena, Franca
2011-12-01
A comprehensive tectono-magmatic model based on new geochemical and field data is discussed in order to highlight the significance of the high-TiO 2 bimodal picrite basalt/rhyolite association in the north-eastern sector of the Ethiopian Plateau, which is considered to be the axial zone of the 30 Ma Continental Flood Basalt activity related to the Afar plume (Beccaluva et al., 2009). In this area the volcanic sequence consists of approximately 1700 m of high TiO 2 (4-6.5%) picrite basalts, covered by rhyolitic ignimbrites and lavas, with an average thickness of 300 m, which discontinuously extend over an area of nearly 13,500 km 2 (ca. 3600 km 3). Petrogenetic modelling, using rock and mineral chemical data and phase equilibria calculations by PELE and MELTS, indicates that: 1) picrite basalts could generate rhyolitic, sometimes peralkaline, residual melts with persistently high titanium contents (TiO 2 0.4-1.1%; Fluorine 0.2-0.3%; H 2O 2-3%; density ca. 2.4) corresponding to liquid fractions 9-16%; 2) closed system fractional crystallisation processes developed at 0.1-0.3 GPa pressure and 1390-750 Ā°C temperature ranges, under QFM fO 2 conditions; 3) the highest crystallisation rate - involving 10-13% of Fe-Ti oxide removal - in the temperature range 1070-950 Ā°C, represents a transitory (short-lived) fractionation stage, which results in the absence of erupted silica intermediate products (Daly gap). The eruption of low aspect ratio fluorine-rich rhyolitic ignimbrites and lavas capping the basic volcanics implies a rapid change from open- to closed-system tectono-magmatic conditions, which favoured the trapping of parental picrite basalts and their fractionation in upwardly zoned magma chambers. This evolution resulted from the onset of continental rifting, which was accompanied by normal faulting and block tilting, and the formation of shallow - N-S elongated - fissural chambers parallel to the future Afar Escarpment. The eruption of large volumes of rhyolitic
Department of Housing and Urban Development ā The purpose of the Continuum of Care (CoC) Homeless Assistance Programs is to reduce the incidence of homelessness in CoC communities by assisting homeless...
Mercer, Celestine N.; Hofstra, Albert H.; Todorov, Todor I.; Roberge, Julie; Burgisser, Alain; Adams, David T.; Cosca, Michael A.
2015-01-01
The Hideaway Park tuff is the only preserved extrusive volcanic unit related to the Red Mountain intrusive complex, which produced the world-class Henderson porphyry Mo deposit. Located within the Colorado Mineral Belt, USA, Henderson is the second largest Climax-type Mo deposit in the world, and is therefore an excellent location to investigate magmatic processes leading to Climax-type Mo mineralization. We combine an extensive dataset of major element, volatile, and trace element abundances in quartz-hosted melt inclusions and pumice matrix glass with major element geochemistry from phenocrysts to reconstruct the pre-eruptive conditions and the source and evolution of metals within the magma. Melt inclusions are slightly peraluminous topaz rhyolitic in composition and are volatile-charged (ā¤6āwt % H2O, ā¤600āppm CO2, ā¼0Ā·3ā1Ā·0āwt % F, ā¼2300ā3500āppm Cl) and metal-rich (ā¼7ā24āppm Mo, ā¼4ā14āppm W, ā¼21ā52āppm Pb, ā¼28ā2700āppm Zn, shallow ascent and eruption. Filter pressing, crystal settling, magma recharge and mixing of less evolved rhyolite melt, and volatile exsolution were important processes during magma evolution; the low estimated viscosities (ā¼105ā1010āPa s) of these H2O- and F-rich melts probably enhanced these processes. A noteworthy discrepancy between the metal contents in the pumice matrix glass and in the melt inclusions suggests that after quartz crystallization ceased upon shallow magma ascent and eruption, the Hideaway Park magma exsolved an aqueous fluid into which Mo, Bi, Ag, Zn, Mn, Cs, and Y strongly partitioned. Given that the Henderson deposit contains anomalous abundances of not only Mo, but also W, Pb, Zn, Cu, Bi, Ag, and Mn, we suggest that these metals were sourced from similar fluids exsolved from unerupted portions of the same magmatic system. Trace element ratios imply that Mo was sourced deep, from either the lower crust or metasomatized mantle. The origin of sulfur remains unresolved
Topology Optimization of Continuum Structures with Local Stress Constraints
DEFF Research Database (Denmark)
Duysinx, Pierre; BendsĆøe, Martin P
1998-01-01
We introduce an extension of current technologies for topology optimization of continuum structures which allows for treating local stress criteria. We first consider relevant stress criteria for porous composite materials, initially by studying the stress states of the so-called rank 2 layered m...
Advanced dielectric continuum model of preferential solvation
Basilevsky, Mikhail; Odinokov, Alexey; Nikitina, Ekaterina; Grigoriev, Fedor; Petrov, Nikolai; Alfimov, Mikhail
2009-01-01
A continuum model for solvation effects in binary solvent mixtures is formulated in terms of the density functional theory. The presence of two variables, namely, the dimensionless solvent composition y and the dimensionless total solvent density z, is an essential feature of binary systems. Their coupling, hidden in the structure of the local dielectric permittivity function, is postulated at the phenomenological level. Local equilibrium conditions are derived by a variation in the free energy functional expressed in terms of the composition and density variables. They appear as a pair of coupled equations defining y and z as spatial distributions. We consider the simplest spherically symmetric case of the Born-type ion immersed in the benzene/dimethylsulfoxide (DMSO) solvent mixture. The profiles of y(R ) and z(R ) along the radius R, which measures the distance from the ion center, are found in molecular dynamics (MD) simulations. It is shown that for a given solute ion z(R ) does not depend significantly on the composition variable y. A simplified solution is then obtained by inserting z(R ), found in the MD simulation for the pure DMSO, in the single equation which defines y(R ). In this way composition dependences of the main solvation effects are investigated. The local density augmentation appears as a peak of z(R ) at the ion boundary. It is responsible for the fine solvation effects missing when the ordinary solvation theories, in which z =1, are applied. These phenomena, studied for negative ions, reproduce consistently the simulation results. For positive ions the simulation shows that z ā«1 (z =5-6 at the maximum of the z peak), which means that an extremely dense solvation shell is formed. In such a situation the continuum description fails to be valid within a consistent parametrization.
Characterization of the rhyolites from the ore body Lela using neutron activation analysis
International Nuclear Information System (INIS)
Capote Rodriguez, G.; Pena Fortes, B.
1996-01-01
Is the present work 22 elements were determined in nine rhyolitic geological samples from a wolframium ore body Lela located in the territory of La Isla de la Juventud. The results obtained are of great importance for the evaluation of the potentiality of the mentioned rocks as a source of uranium mineralization. The neutron activation analysis is an important analytical method used for a multi-elementary determination in geological samples, because its non-destructive character and high accuracy and precision. The irradiation of the samples was developed in the research reactor RA-6 of the Atomic Center of Bariloche, Argentina
The permeability evolution of tuffisites and outgassing from dense rhyolitic magma
Heap, M. J.; Tuffen, H.; Wadsworth, F. B.; ReuschlĆ©, T.; Castro, J. M.; Schipper, C. I.
2017-12-01
Recent observations of rhyolitic lava effusion from eruptions in Chile indicate that simultaneous pyroclastic venting facilitates outgassing. Venting from conduit-plugging lava domes is pulsatory and occurs through shallow fracture networks that deliver pyroclastic debris and exsolved gases to the surface. However, these fractures become blocked as the particulate fracture infill sinters viscously, thus drastically reducing permeability. Tuffisites, fossilized debris-filled fractures of this venting process, are abundant in pyroclastic material ejected during hybrid explosive-effusive activity. Dense tuffisite-hosting obsidian bombs ejected from VolcĆ”n ChaitĆ©n (Chile) in 2008 afford an opportunity to better understand the permeability evolution of tuffisites within low-permeability conduit plugs, wherein gas mobility is reliant upon fracture pathways. We use laboratory measurements of the permeability and porosity of tuffisites that preserve different degrees of sintering, combined with a grainsize-based sintering model and constraints on pressure-time paths from H2O diffusion, to place first-order constraints on tuffisite permeability evolution. Inferred timescales of sintering-driven tuffisite compaction and permeability loss, spanning minutes to hours, coincide with observed vent pulsations during hybrid rhyolitic activity and, more broadly, timescales of pressurization accompanying silicic lava dome extrusion. We therefore conclude that sintering exerts a first-order control on fracture-assisted outgassing from low-permeability, conduit-plugging silicic magma.
Lithium enrichment in intracontinental rhyolite magmas leads to Li deposits in caldera basins.
Benson, Thomas R; Coble, Matthew A; Rytuba, James J; Mahood, Gail A
2017-08-16
The omnipresence of lithium-ion batteries in mobile electronics, and hybrid and electric vehicles necessitates discovery of new lithium resources to meet rising demand and to diversify the global lithium supply chain. Here we demonstrate that lake sediments preserved within intracontinental rhyolitic calderas formed on eruption and weathering of lithium-enriched magmas have the potential to host large lithium clay deposits. We compare lithium concentrations of magmas formed in a variety of tectonic settings using in situ trace-element measurements of quartz-hosted melt inclusions to demonstrate that moderate to extreme lithium enrichment occurs in magmas that incorporate felsic continental crust. Cenozoic calderas in western North America and in other intracontinental settings that generated such magmas are promising new targets for lithium exploration because lithium leached from the eruptive products by meteoric and hydrothermal fluids becomes concentrated in clays within caldera lake sediments to potentially economically extractable levels.Lithium is increasingly being utilized for modern technology in the form of lithium-ion batteries. Here, using in situ measurements of quartz-hosted melt inclusions, the authors demonstrate that preserved lake sediments within rhyolitic calderas have the potential to host large lithium-rich clay deposits.
Subaqueous rhyolite block lavas in the Miocene Ushikiri Formation, Shimane Peninsula, SW Japan
Kano, Kazuhiko; Takeuchi, Keiji; Yamamoto, Takahiro; Hoshizumi, Hideo
1991-06-01
A rhyolite mass of the Miocene Ushikiri Formation in the western part of the Shimane Peninsula, SW Japan, is a small subaqueous edifice about 600 m high and 4 km wide, formed at water depths between 200 and 1000 m. It consists mainly of three relatively flat, lava-flow units 50-300 m in maximum thickness, each of which includes lobes and their polyhedral fragments. The lava lobes are poorly to well vesiculated, glassy to microcrystalline and flow-banded and -folded. Compared with mafic pillows, they are large, having thick, quenched and brecciated, glassy crusts because of their high viscosity, surface tension and thermal conductivity. Their surfaces disintegrate into polyhedral fragments and grade into massive volcanic breccia. The massive volcanic breccia composed of the lobe fragments is poorly sorted and covered with stratified volcanic breccia of the same rock type. The rhyolite lavas commonly bifurcate in a manner similar to mafic pillow lavas. However, they are highly silicic with 1-5 vol.% phenocrysts and have elongated vesicles and flow-folds, implying that they were visco-plastic during flowage. Their surface features are similar to those of subaerial block lava. With respect to rheological and morphological features, they are subaqueous equivalents of block lava.
Possible two-stage /sup 87/Sr evolution in the Stockdale Rhyolite
Energy Technology Data Exchange (ETDEWEB)
Compston, W.; McDougall, I. (Australian National Univ., Canberra. Research School of Earth Sciences); Wyborn, D. (Department of Minerals and Energy, Canberra (Australia). Bureau of Mineral Resources)
1982-12-01
The Rb-Sr total-rock data for the Stockdale Rhyolite, of significance for the Palaeozoic time scale, are more scattered about a single-stage isochron than expected from experimental error. Two-stage /sup 87/Sr evolution for several of the samples is explored to explain this, as an alternative to variation in the initial /sup 87/Sr//sup 86/Sr which is customarily used in single-stage dating models. The deletion of certain samples having very high Rb/Sr removes most of the excess scatter and leads to an estimate of 430 +- 7 m.y. for the age of extrusion. There is a younger alignment of Rb-Sr data within each sampling site at 412 +- 7 m.y. We suggest that the Stockdale Rhyolite is at least 430 m.y. old, that its original range in Rb/Sr was smaller than now observed, and that it experienced a net loss in Sr during later hydrothermal alteration at ca. 412 m.y.
Possible two-stage 87Sr evolution in the Stockdale Rhyolite
International Nuclear Information System (INIS)
Compston, W.; McDougall, I.; Wyborn, D.
1982-01-01
The Rb-Sr total-rock data for the Stockdale Rhyolite, of significance for the Palaeozoic time scale, are more scattered about a single-stage isochron than expected from experimental error. Two-stage 87 Sr evolution for several of the samples is explored to explain this, as an alternative to variation in the initial 87 Sr/ 86 Sr which is customarily used in single-stage dating models. The deletion of certain samples having very high Rb/Sr removes most of the excess scatter and leads to an estimate of 430 +- 7 m.y. for the age of extrusion. There is a younger alignment of Rb-Sr data within each sampling site at 412 +- 7 m.y. We suggest that the Stockdale Rhyolite is at least 430 m.y. old, that its original range in Rb/Sr was smaller than now observed, and that it experienced a net loss in Sr during later hydrothermal alteration at ca. 412 m.y. (orig.)
Wada, K.; Sano, K.
2016-12-01
Simultaneously explosive and effusive eruptions of silicic magmas has shed light on the vesiculation and outgassing history of ascending magmas in the conduit and emplacement model of obsidian-rhyolite lavas (Castro et al., 2014; Shipper et al, 2013). As well as the knowledge of newly erupted products such as 2008-2009 ChaitĆ©n and 2011-2012 CordĆ³n Caule eruptions, field and micro-textural evidences of well-exposed internal structure of obsidian-rhyolite lava leads to reveal eruption processes of silicic magmas. The Shirataki monogenetic volcano field, 2.2 million year age, northern Hokkaido, Japan, contains many outcrops of obsidian and vesiculated rhyolite zones (SiO2=76.7-77.4 wt.%). Among their outcrops, Akaishiyama lava shows good exposures of internal sections from the top to the bottom along the Kyukasawa valley with thickness of about 190 meters, showing the symmetrical structure comprising a upper clastic zone (UCZ; 5m thick), an upper dense obsidian zone (UDO; 15m), an upper banded obsidian zone (UBO; 70-80m), a central rhyolite zone (CR; 65m), a lower banded obsidian zone (LBO; 15m), a lower dense obsidian zone (LDO; 20m), and a lower clastic zone (LCZ; 3m). The upper banded obsidian zone is characterized by existence of spherulite concentration layers with tuffisite veins and rhyolite enclaves. Spherulites consisting of albite, cristobalaite and obsidian glass, are clustered in the dense obsidian. Tuffisite veins show brecciated obsidians in tuffaceous matrix, showing an outgassing path during the emplacement of obsidian lava. Perpendicular dip of spherulite parallel rows indicates the banded zone itself was the domain of vent area. From the observation of these occurrences in the internal section and rock texture, we show the qualitative formation model of Shirataki obsidian-rhyolite lava.
Directory of Open Access Journals (Sweden)
KovaÄeviÄ Jovan
2013-01-01
Full Text Available During investigation of the Jabal Eghei area in southern Libya and the production of geological maps at a scale of 1:250 000 (Tibesti sector, sheet Wadi Eghei NF 34-1 and NF 34-2, regional prospecting for mineral raw materials was performed. Radiometric survey of observed targets at the sites indicated two significant uranium mineralizations in rhyolites, and some smaller ones in granites that are in close contact with rhyolites. Rhyolites are located in the central part of the investigated region. They cut through granite rocks. The first mineralization is in the central part of the rhyolite region, which is mostly composed of silificated rhyolites. The second one was discovered near the granite-rhyolite contact zone, characterized by the presence of silicified breccia rocks. These findings were confirmed by laboratory measurements of more than seventy samples collected in the area, using high resolution gamma-ray spectrometry. The concentrations of uranium in these mineralizations were found to range from approx. 50 mg kg-1 to more than 600 mg kg-1. The latter value is about 240 times above the Earthās average. Besides uranium, these measurements have also given concentrations of thorium and potassium. Additional geochemical analysis was performed on samples taken from locations where uranium anomalies were discovered using ICP-MS technique, in which concentrations of more than forty elements were determined. Uranium mineralizations are accompained by increased contents of silver (up to 17 times, arsenic (up to 8 times, molybdenum (up to 50 times, mercury (up to 9 times, and lead (up to 14 times, in regard to the Clarkās values. These results warrant a continued investigation of this region because of potential interest in the discovery of nuclear mineral raw materials.
Giachetti, T.; Shea, T.; Gonnermann, H. M.; McCann, K. A.; Hoxsie, E. C.
2016-12-01
Significant explosive activity generally precedes or coexists with the large effusion of rhyolitic lava (e.g., Mono Craters; Medicine Lake Volcano; Newberry; ChaitĆ©n; CordĆ³n Caulle). Such explosive-to-effusive transitions and, ultimately, cessation of activity are commonly explained by the overall waning magma chamber pressure accompanying magma withdrawal, albeit modulated by magma outgassing. The tephra deposits of such explosive-to-effusive eruptions record the character of the transition - abrupt or gradual - as well as potential changes in eruptive conditions, such as magma composition, volatiles content, mass discharge rate, conduit size, magma outgassing. Results will be presented from a detailed study of both the gas-rich (pumice) and gas-poor (obsidian) juvenile pyroclasts produced during the Plinian phase of the 1060 CE Glass Mountain eruption of Medicine Lake Volcano, California. In the proximal deposits, a multitude of pumice-rich sections separated by layers rich in dense clasts suggests a pulsatory behavior of the explosive phase. Density measurements on 2,600 pumices show that the intermediate, most voluminous deposits have a near constant median porosity of 65%. However, rapid increase in porosity to 75-80% is observed at both the bottom and the top of the fallout deposits, suggestive of rapid variations in magma degassing. In contrast, a water content of pyroclastic obsidians of approximately 0.6 wt% does remain constant throughout the eruption, suggesting that the pyroclastic obsidians degassed up to a constant pressure of a few megapascals. Numerical modeling of eruptive magma ascent and degassing is used to provide constraints on eruption conditions.
Elementary Continuum Mechanics for Everyone
DEFF Research Database (Denmark)
Byskov, Esben
numerical method, the finite element method, including means of mending inherent problems ā¢An informal, yet precise exposition that emphasizes not just how a topic is treated, but discusses why a particular choice is made The book opens with a derivation of kinematically nonlinear 3-D continuum mechanics...
DEFF Research Database (Denmark)
Ind, Nicholas; Iglesias, Oriol; Markovic, Stefan
2017-01-01
-creation - from tactical market research tool to strategic collaborative innovation method, and shows that brands can be positioned along a continuum between these two polarities. This article also presents the implications for those that want to seize the potential of co-creation....
The geometry of continuum regularization
International Nuclear Information System (INIS)
Halpern, M.B.
1987-03-01
This lecture is primarily an introduction to coordinate-invariant regularization, a recent advance in the continuum regularization program. In this context, the program is seen as fundamentally geometric, with all regularization contained in regularized DeWitt superstructures on field deformations
Variational principles of continuum mechanics I fundamentals
Berdichevskii, V L
2009-01-01
This is a concise and understandable book about variational principles of continuum mechanics. The book is accessible to applied mathematicians, physicists and engineers who have an interest in continuum mechanics.
Variational principles of continuum mechanics II applications
Berdichevsky, Victor L
2009-01-01
This concise and understandable book about variational principles of continuum mechanics presents the classical models. The book is accessible to applied mathematicians, physicists and engineers who have an interest in continuum mechanics.
Continuum methods of physical modeling continuum mechanics, dimensional analysis, turbulence
Hutter, Kolumban
2004-01-01
The book unifies classical continuum mechanics and turbulence modeling, i.e. the same fundamental concepts are used to derive model equations for material behaviour and turbulence closure and complements these with methods of dimensional analysis. The intention is to equip the reader with the ability to understand the complex nonlinear modeling in material behaviour and turbulence closure as well as to derive or invent his own models. Examples are mostly taken from environmental physics and geophysics.
Altaner, S.P.; Ylagan, R.F.; Savin, S.M.; Aronson, J.L.; Belkin, H.E.; Pozzuoli, A.
2003-01-01
A rhyolitic hyaloclastite from Ponza Island, Italy, was hydrothermally altered, producing four distinct alteration zones based on X-ray diffraction mineralogy and field textures: (1) nonpervasive argillic zone; (2) propylitic zone; (3) silicic zone; and (4) sericitic zone. The unaltered hyaloclastite is volcanic breccia with clasts of vesiculated obsidian in a matrix of predominantly pumice lapilli. Incomplete alteration of the hyaloclastite resulted in the nonpervasive argillic zone, characterized by smectite and disordered opal-CT. The other three zones exhibit more complete alteration of the hyaloclastite. The propylitic zone is characterized by mixed-layer illite-smectite (I-S) with 10 to 85% I, mordenite, opal-C, and authigenic K-feldspar (akspar). The silicic zone is characterized by I-S with ???90% I, pure illite, quartz, akspar, and occasional albite. The sericitic zone consists primarily of I-S with ???66% I, pure illite, quartz, and minor akspar and pyrite. K/Ar dates of I-S indicate hydrothermal alteration occurred at 3.38 ?? 0.08 Ma. Oxygen isotope compositions of I-S systematically decrease from zones 1 to 4. In the argillic zone, smectite has ??18 O values of 21.7 to 22.0??? and I-S from the propylitic, silicic, and sericitic zones ranges from 14.5 to 16.3???, 12.5 to 14.0???, and 8.6 to 11.9???, respectively. ??18 O values for quartz from the silicic and sericitic zones range from 12.6 to 15.9???. By use of isotope fractionation equations and data from authigenic quartz-hosted primary fluid inclusions, alteration temperatures ranged from 50 to 65 ??C for the argillic zone, 85 to 125 ??C for the propylitic zone, 110 to 210 ??C for the silicic zone, and 145 to 225 ??C for the sericitic zone. Fluid inclusion data and calculated ??18 O water values indicate that hydrothermal fluids were seawater dominated. Mass-transfer calculations indicate that hydrothermal alteration proceeded in a relatively open chemical system and alteration in the sericitic zone
Sano, Kyohei; Toramaru, Atsushi
2017-07-01
To reveal the cooling process of a rhyolite-obsidian flow, we studied the morphology of plagioclase microlites in the Tokachi-Ishizawa lava of Shirataki, northern Hokkaido, Japan, where the structure of the lava can be observed from obsidian at the base of the flow to the innermost rhyolite. Needle-like micron-scale textures, known as "projections", occur on the short side surfaces of the plagioclase microlites. Using FE-SEM we discovered a positive correlation between the lengths and spacings of these projections. On the basis of the instability theory of an interface between melt and crystal, and to understand the length and spacing data, we developed a model that explains the positive correlation and allows us to simultaneously estimate growth rates and growth times. Applying the model to our morphological data and the estimated growth rates and growth times, we suggest that the characteristics of the projections reflect the degree of undercooling, which in turn correlates with lava structure (the obsidian at the margin of the flow experienced a higher degree of undercooling than the interior rhyolite). The newly developed method provides insights into the degree of undercooling during the final stages of crystallization of a rhyolitic lava flow.
Continuum description for jointed media
International Nuclear Information System (INIS)
Thomas, R.K.
1982-04-01
A general three-dimensional continuum description is presented for a material containing regularly spaced and approximately parallel jointing planes within a representative elementary volume. Constitutive relationships are introduced for linear behavior of the base material and nonlinear normal and shear behavior across jointing planes. Furthermore, a fracture permeability tensor is calculated so that deformation induced alterations to the in-situ values can be measured. Examples for several strain-controlled loading paths are presented
Evidence for a welded tuff in the Rhyolite of Calico Hills
International Nuclear Information System (INIS)
Dickerson, R.P.; Hunter, W.C.
1994-01-01
A welded pyroclastic deposit has been identified in the Rhyolite of Calico Hills near Yucca Mountain, Nevada, where only lava flows and nonwelded pyroclastic deposits were previously described. Field data from Fortymile Wash show that nonwelded, bedded tuff grades upward into partially welded massive ruff, and thence into densely welded vitrophyre. Petrographic data show a progressive decrease in inter- and intragranular porosity and amount of vapor-phase minerals, with increasing welding. Pumice fragments are first deformed, then develop diffuse boundaries which become increasingly obscure with progressive welding. The most densely welded rock is a perlitic vitrophyre. The origin of this welded tuff is not clear, as it could represent an ignimbrite or a tuff fused beneath a thick lava flow
International Nuclear Information System (INIS)
Hammersley, L.; DePaolo, D.J; Beate, B
2001-01-01
The mechanisms responsible for the generation of large volumes of silicic magma and the eruption of large-volume rhyolitic ignimbrites (LRI's) remain poorly understood. Of particular interest are the relative roles of crustal assimilation, fractional crystallization and magma supply and the processes by which large volumes of magma accumulate in crustal chambers rather than erupt in smaller batches. Isotope geochemistry, combined with study of major and trace element variations of lavas, can be used to infer the relative contribution of crustal material and continued magmatic supply. Timescales for the accumulation of magma can be estimated using detailed geochronology. Magma supply rates can be estimated from eruption rates of nearby volcanoes. In this study we investigate the evolution of the Chalupas LRI, a caldera system in the Ecuadorian Andes where LRI's are rare in comparison to the Southern Volcanic Zone (SVZ) of South America (au)
Frequency chirpings in Alfven continuum
Wang, Ge; Berk, Herb; Breizman, Boris; Zheng, Linjin
2017-10-01
We have used a self-consistent mapping technique to describe both the nonlinear wave-energetic particle resonant interaction and its spatial mode structure that depends upon the resonant energetic particle pressure. At the threshold for the onset of the energetic particle mode (EPM), strong chirping emerges in the lower continuum close to the TAE gap and then, driven by strong continuum damping, chirps rapidly to lower frequencies in the Alfven continuum. An adiabatic theory was developed that accurately replicated the results from the simulation where the nonlinearity was only due to the EPM resonant particles. The results show that the EPM-trapped particles have their action conserved during the time of rapid chirping. This adiabaticity enabled wave trapped particles to be confined within their separatrix, and produce even larger resonant structures, that can produce a large amplitude mode far from linearly predicted frequencies. In the present work we describe the effect of additional MHD nonlinearity to this calculation. We studied how the zonal flow component and its nonlinear feedback to the fundamental frequency and found that the MHD nonlinearity doesn't significantly alter the frequency chirping response that is predicted by the calculation that neglects the MHD nonlinearity.
International Nuclear Information System (INIS)
Abdelouas, A.
1996-01-01
The purpose of this work is to complement an experimental program on the R7T7 nuclear waste glass alteration in brines at 190 deg C in Germany by the analysis of the structure and the chemical composition of the alteration layers, and to study the alteration of rhyolitic glasses in natural brines from Bolivia as analogue for nuclear waste glasses disposed in salt formations. Alteration experiments with the R7T7 and basaltic glasses and obsidian in MgCl 2 -CaCl 2 -saturated brine at 190 deg. C were also conducted in order to study the influence of the glass composition on the nature of the secondary phases. The experiments with the R7T7 glass in three salt brines, saturated respectively in MgCl 2 , MgCl 2 -CaCl 2 and NaCl, showed that the solubilities of most radionuclides are controlled by the secondary phases. Nd, La, and Pr are trapped in powellite, Ce in cerianite, U in coffinite, and Sr is partially immobilized in barite. These phases are stable for more than one year. There is a good similarity between the secondary phases formed experimentally on volcanic glasses and the R7T7 glass altered in MgCl 2 -CaCl 2 -saturated brine. The abundance of Mg in solution permits the formation of similar magnesian clays on the glass samples independently of the nature of the initial glasses. These results support the use of volcanic glasses alteration patterns in Mg-rich solutions to understand the long-term behavior of nuclear waste glasses and to evaluate the stability of the secondary phases. The study of the sediments of Uyuni (Bolivia) showed that the corrosion rate of the rhyolitic glass in brines at 10 deg. C is 12 to 30 time lower than those of rhyolitic glasses altered in high dilute conditions. The low alteration rate of rhyolitic glasses in brines and the formation of secondary phases such as smectite, barite and cerianite (also formed during the experimental alteration of the R7T7 glass), permit us to expect the low alteration of nuclear waste glasses at long
A constitutive model of soft tissue: From nanoscale collagen to tissue continuum
Tang, Huang
2009-04-08
Soft collagenous tissue features many hierarchies of structure, starting from tropocollagen molecules that form fibrils, and proceeding to a bundle of fibrils that form fibers. Here we report the development of an atomistically informed continuum model of collagenous tissue. Results from full atomistic and molecular modeling are linked with a continuum theory of a fiber-reinforced composite, handshaking the fibril scale to the fiber and continuum scale in a hierarchical multi-scale simulation approach. Our model enables us to study the continuum-level response of the tissue as a function of cross-link density, making a link between nanoscale collagen features and material properties at larger tissue scales. The results illustrate a strong dependence of the continuum response as a function of nanoscopic structural features, providing evidence for the notion that the molecular basis for protein materials is important in defining their larger-scale mechanical properties. Ā© 2009 Biomedical Engineering Society.
International Nuclear Information System (INIS)
Kasen, M.B.
1983-01-01
This chapter discusses the roles of composite laminates and aggregates in cryogenic technology. Filamentary-reinforced composites are emphasized because they are the most widely used composite materials. Topics considered include composite systems and terminology, design and fabrication, composite failure, high-pressure reinforced plastic laminates, low-pressure reinforced plastics, reinforced metals, selectively reinforced structures, the effect of cryogenic temperatures, woven-fabric and random-mat composites, uniaxial fiber-reinforced composites, composite joints in cryogenic structures, joining techniques at room temperature, radiation effects, testing laminates at cryogenic temperatures, static and cyclic tensile testing, static and cyclic compression testing, interlaminar shear testing, secondary property tests, and concrete aggregates. It is suggested that cryogenic composite technology would benefit from the development of a fracture mechanics model for predicting the fitness-for-purpose of polymer-matrix composite structures
Continuum theory for nanotube piezoelectricity.
Michalski, P J; Sai, Na; Mele, E J
2005-09-09
We develop and solve a continuum theory for the piezoelectric response of one-dimensional nanotubes and nanowires, and apply the theory to study electromechanical effects in boron-nitride nanotubes. We find that the polarization of a nanotube depends on its aspect ratio, and a dimensionless constant specifying the ratio of the strengths of the elastic and electrostatic interactions. The solutions of the model as these two parameters are varied are discussed. The theory is applied to estimate the electric potential induced along the length of a boron-nitride nanotube in response to a uniaxial stress.
Continuum mechanics of electromagnetic solids
Maugin, GA
1988-01-01
This volume is a rigorous cross-disciplinary theoretical treatment of electromechanical and magnetomechanical interactions in elastic solids. Using the modern style of continuum thermomechanics (but without excessive formalism) it starts from basic principles of mechanics and electromagnetism, and goes on to unify these two fields in a common framework. It treats linear and nonlinear static and dynamic problems in a variety of elastic solids such as piezoelectrics, electricity conductors, ferromagnets, ferroelectrics, ionic crystals and ceramics. Chapters 1-3 are introductory, describing the e
Continuum-regularized quantum gravity
International Nuclear Information System (INIS)
Chan Huesum; Halpern, M.B.
1987-01-01
The recent continuum regularization of d-dimensional Euclidean gravity is generalized to arbitrary power-law measure and studied in some detail as a representative example of coordinate-invariant regularization. The weak-coupling expansion of the theory illustrates a generic geometrization of regularized Schwinger-Dyson rules, generalizing previous rules in flat space and flat superspace. The rules are applied in a non-trivial explicit check of Einstein invariance at one loop: the cosmological counterterm is computed and its contribution is included in a verification that the graviton mass is zero. (orig.)
BCS equations in the continuum
International Nuclear Information System (INIS)
Sandulescu, N.; Liotta, R. J.; Wyss, R.
1998-01-01
The properties of nuclei close to the drip line are significantly influenced by the continuum part of the single-particle spectrum. The main role is played by the resonant states which are largely confined in the region of nuclear potential and therefore stronger coupled with the bound states in an excitation process. Resonant states are also important in the nuclei beyond the drip line. In this case the decay properties of the nucleus can be directly related to the widths of the narrow resonances occupied by the unbound nucleons. The aim of this work is to propose an alternative for evaluating the effect of the resonant part of single-particle spectrum on the pairing correlations calculated within the BCS approximation. We estimated the role of resonances in the case of the isotope 170 Sn. The Resonant-BCS (RBCS) equations are solved for the case of a seniority force. The BCS approximation based on a seniority force cannot be applied in the case of a nucleus immersed in a box if all discrete states simulating the continuum are considered. In such a case the pairing correlations will increase with the number of states in the box. In our case one can still apply a seniority force with RBCS because the effect of the continuum appears here through a finite number of physical resonances, well defined by the given mean field. Because these resonances have a spatial distribution concentrated within the region of the nuclear potential, one expects that the localization probability of nucleons, far out from the nuclear surface, to be small. The gap obtained taking correctly the contribution of resonances, according to RBCS equations, is about 1.3 MeV, while pairing gap calculated only with the bound single-particle spectrum has the value Ī = 1.10 MeV. If we introduce also the resonant states, neglecting completely their widths, the gap will increase to the value Ī = 1.880 MeV. Therefore, one cannot estimate properly the pairing correlations by supplementing the spectrum
Bouvet de Maisonneuve, Caroline; Bachmann, Olivier; Burgisser, Alain
2009-08-01
Silicic pumices formed during explosive volcanic eruptions are faithful recorders of the state of the magma in the conduit, close to or at the fragmentation level. We have characterized four types of pumices from the non-welded rhyolitic Kos Plateau Tuff, which erupted 161,000 years ago in the East Aegean Arc, Greece. The dominant type of pumice (>90 vol.%) shows highly elongated tubular vesicles. These tube pumices occur throughout the eruption. Less common pumice types include: (1) āfrothyā pumice (highly porous with large, sub-rounded vesicles), which form 5-10 vol.% of the coarsest pyroclastic flow deposits, (2) dominantly āmicrovesicularā and systematically crystal-poor pumices, which are found in early erupted, fine-grained pyroclastic flow units, and are characterized by many small (<50 Ī¼m in diameter) vesicles and few mm-sized, irregular voids, (3) grey or banded pumices, indicating the interaction between the rhyolite and a more mafic magma, which are found throughout the eruption sequence and display highly irregular bubble shapes. Except for the grey-banded pumices, all three other types are compositionally identical and were generated synchronously as they are found in the same pyroclastic units. They, therefore, record different conditions in the volcanic conduit leading to variable bubble nucleation, growth and coalescence. A total of 74 pumice samples have been characterized using thin section observation, SEM imagery, porosimetry, and permeametry. We show that the four pumice types have distinct total and connected porosity, tortuosity and permeability. Grey-banded pumices show large variations in petrophysical characteristics as a response to mingling of two different magmas. The microvesicular, crystal-poor, pumices have a bimodal bubble size distribution, interpreted as reflecting an early heterogeneous bubble nucleation event followed by homogeneous bubble nucleation close to fragmentation. Finally, the significant differences in
Boyina, Gangadhara Rao T.; Rayavarapu, Vijaya Kumar; V. V., Subba Rao
2017-02-01
The prediction of ultimate strength remains the main challenge in the simulation of the mechanical response of composite structures. This paper examines continuum damage model to predict the strength and size effects for deformation and failure response of polymer composite laminates when subjected to complex state of stress. The paper also considers how the overall results of the exercise can be applied in design applications. The continuum damage model is described and the resulting prediction of size effects are compared against the standard benchmark solutions. The stress analysis for strength prediction of rotary wing aircraft cabin door is carried out. The goal of this study is to extend the proposed continuum damage model such that it can be accurately predict the failure around stress concentration regions. The finite element-based continuum damage mechanics model can be applied to the structures and components of arbitrary configurations where analytical solutions could not be developed.
DEFF Research Database (Denmark)
BergstrĆøm-Nielsen, Carl
2011-01-01
Strategies are open compositions to be realised by improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound files will in some cases only provide a few minutes' sample. Please DOWNLOAD them to hear them in full...
DEFF Research Database (Denmark)
2014-01-01
Memory Pieces are open compositions to be realised solo by an improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound files will in some cases only provide a few minutes' sample. Please DOWNLOAD them to hear them...
Continuum gamma-ray spectroscopy
International Nuclear Information System (INIS)
Diamond, R.M.
1981-06-01
When angular momentum is added to a nucleus, it is, of course, carried by the individual nucleons, but two limiting types of behavior may be distinguished: (1) a small number of high-j particles align with the rotation axis and (2) the nucleus is deformed and rotates as a whole. At high spin all nuclei seem to show a compromise utilizing both motions. The excited nuclei left as products of (HI,xn) reactions have so many pathways down that none of the Ī³-ray transitions have enough intensity to be seen individually until the population gathers near the yrast line. This occurs usually between spin 20 to 40 h-bar. All our information on the higher states comes from their continuum spectra. With the new techniques that are developing, including the use of multiplicity filters, total-energy spectrometers, energy correlation studies, crystal balls, and observation of giant dipole resonances in the continuum spectra, there is hope to learn much about the nature of the high-spin states
Continuum radiation of argon plasma
International Nuclear Information System (INIS)
D'Yachkov, L.G.
1995-01-01
A simple completely analytical method of the calculation of radiative continuum of plasmas is derived and an analysis of experimental data on continuum radiation of argon plasma is made. The method is based on the semiclassical quantum defect theory. To calculate radial matrix elements of dipole transitions the asymptotic expansion in powers of E c /Ļ 2/3 , with an accuracy to the linear term, where E, is the arithmetic mean of the initial and final energies of the transition, is used. This expansion has the same form for free-free, free-bound and bound-bound transitions. If the quantum defects are also approximated by a linear function of energy, the integration over the electron energy (the Maxwell-Boltzmann distribution is assumed) can be performed in analytical form. For Rydberg states the sum of photoionization continua can be replaced by an integral. We have calculated the absorption coefficient pf argon plasma. The photoionization cross section is calculated for all the states of 4s, 5s, 6s, 4p, 5p, 3d, 4d, 4s', 5s', 6s', 4p', 5p', 3d' and 4d' configurations taking into account P-coupling and multiplet splitting (56 states). Other excited states are allowed for by the integral formula together with free-free transitions
Furukawa, K.; Uno, K.; Kanamaru, T.; Nakai, K.
2017-12-01
We revealed structural development of the Pleistocene Sanukayama rhyolite lava of Kozushima Island, Japan. The good exposure, with about 130 m thick, provides valuable opportunity to understand the vertical structural variation. This exposure corresponds to the upper half of the lava. The paleomagnetic results show that the lava emplaced in subaerial condition at least in the exposed part. The vertical lithofacies are divided into the pumiceous (25-40 m thick), obsidian (40-60 m), spherulitic (30-50 m) layers from top to base. The pumiceous layer is characterized by massive foliated pumice. The foliation dips are gradually changed from gentle (10-30Ā°) in lower part to steep (around 90Ā°) in upper part. This shows the balloon-like morphology. The massive pumiceous layer would be generated from late stage diapiric inflation of the lava (Fink and Manley, 1987). The obsidian layer is composed of massive and welded-brecciated parts. The ductile-deformed light-colored veins, with a few mm thick, are frequently developed. In the microscopic observation, the veins are composed of broken crystals and obsidian clasts indicating fracturing of the lava followed by ductile deformation such as the RFH process (Tuffen et al., 2003). In this layer, extensive vesiculation and microlite development must have been prevented by higher load pressure and faster cooling, respectively. Consequently, they resulted in formation of the obsidian. The spherulitic layer is characterized by development of the ductile-deformed flow banding. The microscopic observation shows that the bands are formed by the spherulite trail. Furthermore, the microlites are aligned within the spherulites. In the heat-retained inner part of the lava, microlites would be developed around the healed fractures. The microlites acted as nucleation site of spherulite. In transition layer between obsidian and spherulitic layers (obsidian layer. This would be caused by high flow-induced shear arising from their rheological
Reaction of Rhyolitic Magma to its Interception by the IDDP-1 Well, Krafla, 2009
Saubin, Ć.; Kennedy, B.; Tuffen, H.; Villeneuve, M.; Watson, T.; Nichols, A. R.; Schipper, I.; Cole, J. W.; Mortensen, A. K.; Zierenberg, R. A.
2017-12-01
The unexpected encounter of rhyolitic magma during IDDP-1 geothermal borehole drilling at Krafla, Iceland in 2009, temporarily created the world's hottest geothermal well. This allowed new questions to be addressed. i) How does magma react to drilling? ii) Are the margins of a magma chamber suitable for long-term extraction of supercritical fluids? To investigate these questions, we aim to reconstruct the degassing and deformation behaviour of the enigmatic magma by looking for correlations between textures in rhyolitic material retrieved from the borehole and the recorded drilling data. During drilling, difficulties were encountered in two zones, at 2070 m and below 2093 m depth. Drilling parameters are consistent with the drill bit encountering a high permeability zone and the contact zone of a magma chamber, respectively. Magma was intercepted three times between 2101-2104.4 m depth, which culminated in an increase in standpipe pressure followed by a decrease in weight on bit interpreted as representing the ascent of magma within the borehole. Circulation returned one hour after the last interception, carrying cuttings of glassy particles, felsite with granophyre and contaminant clasts from drilling, which were sampled as a time-series for the following 9 hours. The nature of glassy particles in this time-series varied through time, with a decrease in the proportion of vesicular clasts and a commensurate increase in dense glassy clasts, transitioning from initially colourless to brown glass. Componentry data show a sporadic decrease in felsite (from 34 wt. %), an increase in glassy particles during the first two hours (from 63 wt. % to 94 wt. %) and an increase in contaminant clasts towards the end of the cutting retrieval period. These temporal variations are probably related to the magma body architecture and interactions with the borehole. Transition from vesicular to dense clasts suggests a change in the degassing process that could be related to an early
Extension versus Bending for Continuum Robots
Directory of Open Access Journals (Sweden)
George Grimes
2008-11-01
Full Text Available In this paper, we analyze the capabilities of a novel class of continuous-backbone ("continuum" robots. These robots are inspired by biological "trunks, and tentacles". However, the capabilities of established continuum robot designs, which feature controlled bending but not extension, fall short of those of their biological counterparts. In this paper, we argue that the addition of controlled extension provides dual and complementary functionality, and correspondingly enhanced performance, in continuum robots. We present an interval-based analysis to show how the inclusion of controllable extension significantly enhances the workspace and capabilities of continuum robots.
Passing waves from atomistic to continuum
Chen, Xiang; Diaz, Adrian; Xiong, Liming; McDowell, David L.; Chen, Youping
2018-02-01
Progress in the development of coupled atomistic-continuum methods for simulations of critical dynamic material behavior has been hampered by a spurious wave reflection problem at the atomistic-continuum interface. This problem is mainly caused by the difference in material descriptions between the atomistic and continuum models, which results in a mismatch in phonon dispersion relations. In this work, we introduce a new method based on atomistic dynamics of lattice coupled with a concurrent atomistic-continuum method to enable a full phonon representation in the continuum description. This permits the passage of short-wavelength, high-frequency phonon waves from the atomistic to continuum regions. The benchmark examples presented in this work demonstrate that the new scheme enables the passage of all allowable phonons through the atomistic-continuum interface; it also preserves the wave coherency and energy conservation after phonons transport across multiple atomistic-continuum interfaces. This work is the first step towards developing a concurrent atomistic-continuum simulation tool for non-equilibrium phonon-mediated thermal transport in materials with microstructural complexity.
International Nuclear Information System (INIS)
Sturchio, N.C.; Seitz, M.G.
1984-01-01
The behavior of a group of nuclear waste elements (U, Th, Sr, Zr, Sb, Cs, Ba, and Sm) during hydrothermal alteration of glassy rhyolite is investigated through detailed geochemical analyses of whole rocks, glass and mineral separates, and thermal waters. Significant mobility of U, Sr, Sb, Cs, and Ba is found, and the role of sorption processes in their observed behavior is identified. Th, Zr, and Sm are relatively immobile, except on a microscopic scale. 9 references, 2 figures, 2 tables
The melt inclusion record from the rhyolitic Kos Plateau Tuff (Aegean Arc)
Bachmann, Olivier; Wallace, Paul J.; Bourquin, Julie
2010-02-01
The >60 km3 rhyolitic Kos Plateau Tuff provides an exceptional probe into the behavior of volatile components in highly evolved arc magmas: it is crystal-rich (30-40 vol% crystals), was rapidly quenched by the explosive eruptive process, and contains abundant homogeneous melt inclusions in large quartz crystals. Several methods for measuring major, trace and volatile element concentrations (SIMS, FTIR, Raman spectroscopy, electron microprobe, LA-ICPMS) were applied to these melt inclusions. We found a ~2 wt% range of H2O contents (4.5-6.5 wt% H2O, measured independently by SIMS, FTIR, and Raman spectroscopy) and relatively low CO2 concentrations (15-140 ppm measured by FTIR, with most analyses <100 ppm). No obvious correlations between H2O, CO2, major and trace elements are observed. These observations require a complex, protracted magma evolution in the upper crust that included: (1) vapor-saturated crystallization in a chamber located between 1.5 and 2.5 kb pressure, (2) closed-system degassing (with up to 10 vol% exsolved gas) as melts percolated upwards through a vertically extensive mush zone (2-4 km thick), and (3) periodic gas fluxing from subjacent, more mafic and more CO2-rich magma, which is preserved as andesite bands in pumices. These processes can account for the range of observed H2O and CO2 values and the lack of correlation between volatiles and trace elements in the melt inclusions.
International Nuclear Information System (INIS)
Smellie, J.A.T.
1982-01-01
The Duobblon rhyolitic ignimbrites, of middle Precambrian age are 60 m thick. They consist of at least three flows with varying degrees of welding and have undergone devitrification, producing lithophysal and spherulitic textures. They are overlain by thick fluviatile red-bed-type conglomerates and sandstones, which in turn are capped by terrestrial acid volcanics. Uranium enrichments of up to 3000 ppm U occur within two or three peneconcordant tabular horizons which are mostly lithophysae-bearing. Fission-track investigations of the ignimbrites and overlying conglomerates and sandstones, which supplement earlier mineralogical studies, show that U occurs as fine pitchblende disseminations; as complex uranotitanates associated with Fe-Ti-Mn oxides; and as coatings associated with matrix sericite. Small amounts of U are present in such primary accessory minerals as sphene, apatite, and zircon. It is suggested that oxidizing U-bearing solutions, generated partly during devitrification of the ignimbrites and partly from the overlying volcano-sedimentary pile, produced the U enrichments with later sulphide deposition, along the more permeable lithophysal horizons in the ignimbrites. (author)
Fragmentation, nucleation and migration of crystals and bubbles in the Bishop Tuff rhyolitic magma
Energy Technology Data Exchange (ETDEWEB)
Gualda, G.; Cook, D.L.; Chopra, R.; Qin, L.; Anderson, A.T.; Rivers, M. (UC)
2010-12-07
The Bishop Tuff (USA) is a large-volume, high-silica pyroclastic rhyolite. Five pumice clasts from three early stratigraphic units were studied. Size distributions were obtained using three approaches: (1) crushing, sieving and winnowing (reliable for crystals >100 {micro}m); (2) microscopy of 1 mm{sup 3} fragments (preferable for crystals <100 {micro}m); and (3) computerised X-ray microtomography of {approx}1 cm{sup 3} pumice pieces. Phenocryst fragments coated with glass are common, and the size distributions for all crystals are concave-upward, indicating that crystal fragmentation is an important magmatic process. Three groups are recognised, characterised by: (1) high-density (0.759-0.902 g cm{sup -3}), high-crystal content (14.4-15.3 wt.%) and abundant large crystals (>800 {micro}m); concave-downward size distributions for whole crystals indicate late-stage growth with limited nucleation, compatible with the slow cooling of a large, gas-saturated, stably stratified magma body; (2) low-density (0.499 g cm{sup -3}), low-crystal content (6.63 wt.%) and few large crystals; the approximately linear size distribution reveals that nucleation was locally important, perhaps close to the walls; and (3) intermediate characteristics in all respects. The volumetric fraction of bubbles inversely correlates with the number of large crystals. This is incompatible with isobaric closed-system crystallisation, but can be explained by sinking of large crystals and rise of bubbles in the magma.
DEFF Research Database (Denmark)
Charreteur, Gilles; Tegner, Christian
2013-01-01
The Rauoafell composite complex is part of the Neogene Breiodalur volcano, eastern Iceland and is composed of a composite feeder dyke, a vent structure and a composite flow. The two end-members of the composite complex are rhyolite and basalt, and both are rich in plagioclase macrocrysts: bytowni...
Zielinski, Robert A.
1979-01-01
Well-characterized samples of rhyolitic obsidian, perlite and felsite from a single lava flow are leached of U by alkaline oxidizing solutions under open-system conditions. Pressure, temperature, flow rate and solution composition are held constant in order to evaluate the relative importance of differences in surface area and crystallinity. Under the experimental conditions U removal from crushed glassy samples proceeds by a mechanism of glass dissolution in which U and silica are dissolved in approximately equal weight fractions. The rate of U removal from crushed glassy samples increases with decreasing average grain size (surface area). Initial rapid loss of a small component (ā 2.5%) of the total U from crushed felsite. followed by much slower U loss, reflects variable rates of attack of numerous uranium sites. The fractions of U removed during the experiment ranged from 3.2% (felsite) to 27% (perlite). An empirical method for evaluating the relative rate of U loss from contemporaneous volcanic rocks is presented which incorporates leaching results and rock permeability data.
Physics of the continuum of borromean nuclei
Energy Technology Data Exchange (ETDEWEB)
Vaagen, J S; Rogde, T [Dept. of Physics, Univ. of Bergen (Norway); Danilin, B V [RRC The Kurchatov Inst., Kurchatov, Moscow (Russian Federation); Ershov, S N [JINR, Dubna, Moscow (Russian Federation); Thompson, I J [Dept. of Physics, Univ. of Surrey, Guildford (United Kingdom); Zhukov, M V [Chalmers Univ. of Technology and Goeteborg Univ., Goeteborg (Sweden); RNBT Collaboration
1998-06-01
The continuum states of two-neutron halo nuclei are calculated in the method of hyperspherical harmonics. Using DWIA theory appropriate for dilute halo matter we have probed the structure of the low-lying {sup 6}He continuum via calculations of charge-exchange and inelastic scattering. (orig.)
Giant resonances in the deformed continuum
International Nuclear Information System (INIS)
Nakatsukasa, T.; Yabana, K.
2004-01-01
Giant resonances in the continuum for deformed nuclei are studied with the time-dependent Hartree-Fock (TDHF) theory in real time and real space. The continuum effect is effectively taken into account by introducing a complex Absorbing Boundary Condition (ABC). (orig.)
Continuum Level Density in Complex Scaling Method
International Nuclear Information System (INIS)
Suzuki, R.; Myo, T.; Kato, K.
2005-01-01
A new calculational method of continuum level density (CLD) at unbound energies is studied in the complex scaling method (CSM). It is shown that the CLD can be calculated by employing the discretization of continuum states in the CSM without any smoothing technique
DEFF Research Database (Denmark)
BergstrĆøm-Nielsen, Carl
2014-01-01
Cue Rondo is an open composition to be realised by improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound/video files will in some cases only provide a few minutes' sample, or the visuals will not appear at all....... Please DOWNLOAD them to see/hear them in full length! This work is licensed under a Creative Commons "by-nc" License. You may for non-commercial purposes use and distribute it, performance instructions as well as specially designated recordings, as long as the author is mentioned. Please see http...
Strength and deformation mechanisms of rhyolitic glass at lower seismogenic zone conditions
Proctor, B.; Lockner, D. A.; Lowenstern, J. B.; Beeler, N. M.
2017-12-01
Although its relevance to coseismic earthquake source properties is still debated, frictional melting and the production of quenched glass called pseudotachylyte is a recurring process in some earthquake source regions. To investigate how glassy materials affect the post- and interseismic- strength and stability of faults, rhyolitic obsidian gouges were sheared under dry and wet conditions from 200 Ā°C to 300 Ā°C at effective normal stresses up to 200 MPa. Velocity-stepping and slide-hold slide tests were performed for up to three days. Dry glass gouges exhibited a brittle rheology at all conditions tested, exhibiting friction values and microstructures consistent with siliciclastic materials. Likewise, wet glass gouges at 200 Ā°C exhibited a brittle rheology. In contrast, wet gouges at 300 Ā°C transitioned from brittle sliding to linear-viscous (Newtonian) flow at strain rates < 3x10-4 s-1, indicating melt-like behavior well below the equilibrium melting temperature. The melt ranged from 2.1x1011 to 2.6x1012 Pa-s. The molten gouges transitioned back to glass when strain rates were increased, which, in some cases, promoted extreme strengthening. The molten gouges were fully welded with rod-shaped microlites rotated and boudinaged into the flow direction. There was very little evidence for nucleation of new phases within the glass or metasomatic alteration. Fourier transform infrared spectroscopy along with electron backscatter imaging demonstrate that hydration of the glass by diffusion of pore water was the dominant process reducing the viscosity and promoting melt flow. As much as 5 wt% water diffused into the nominally anhydrous glass. These results may provide insight into postseismic-slip behaviors and challenge some interpretations of fault kinematics which assume pseudotachylyte formation and flow is solely coseismic.
Parallel algorithms for continuum dynamics
International Nuclear Information System (INIS)
Hicks, D.L.; Liebrock, L.M.
1987-01-01
Simply porting existing parallel programs to a new parallel processor may not achieve the full speedup possible; to achieve the maximum efficiency may require redesigning the parallel algorithms for the specific architecture. The authors discuss here parallel algorithms that were developed first for the HEP processor and then ported to the CRAY X-MP/4, the ELXSI/10, and the Intel iPSC/32. Focus is mainly on the most recent parallel processing results produced, i.e., those on the Intel Hypercube. The applications are simulations of continuum dynamics in which the momentum and stress gradients are important. Examples of these are inertial confinement fusion experiments, severe breaks in the coolant system of a reactor, weapons physics, shock-wave physics. Speedup efficiencies on the Intel iPSC Hypercube are very sensitive to the ratio of communication to computation. Great care must be taken in designing algorithms for this machine to avoid global communication. This is much more critical on the iPSC than it was on the three previous parallel processors
Continuum mechanics elasticity, plasticity, viscoelasticity
Dill, Ellis H
2006-01-01
FUNDAMENTALS OF CONTINUUM MECHANICSMaterial ModelsClassical Space-TimeMaterial BodiesStrainRate of StrainCurvilinear Coordinate SystemsConservation of MassBalance of MomentumBalance of EnergyConstitutive EquationsThermodynamic DissipationObjectivity: Invariance for Rigid MotionsColeman-Mizel ModelFluid MechanicsProblems for Chapter 1BibliographyNONLINEAR ELASTICITYThermoelasticityMaterial SymmetriesIsotropic MaterialsIncompressible MaterialsConjugate Measures of Stress and StrainSome Symmetry GroupsRate Formulations for Elastic MaterialsEnergy PrinciplesGeometry of Small DeformationsLinear ElasticitySpecial Constitutive Models for Isotropic MaterialsMechanical Restrictions on the Constitutive RelationsProblems for Chapter 2BibliographyLINEAR ELASTICITYBasic EquationsPlane StrainPlane StressProperties of SolutionsPotential EnergySpecial Matrix NotationThe Finite Element Method of SolutionGeneral Equations for an Assembly of ElementsFinite Element Analysis for Large DeformationsProblems for Chapter 3Bibliograph...
Hybrid continuum-coarse-grained modeling of erythrocytes
Lyu, Jinming; Chen, Paul G.; Boedec, Gwenn; Leonetti, Marc; Jaeger, Marc
2018-06-01
The red blood cell (RBC) membrane is a composite structure, consisting of a phospholipid bilayer and an underlying membrane-associated cytoskeleton. Both continuum and particle-based coarse-grained RBC models make use of a set of vertices connected by edges to represent the RBC membrane, which can be seen as a triangular surface mesh for the former and a spring network for the latter. Here, we present a modeling approach combining an existing continuum vesicle model with a coarse-grained model for the cytoskeleton. Compared to other two-component approaches, our method relies on only one mesh, representing the cytoskeleton, whose velocity in the tangential direction of the membrane may be different from that of the lipid bilayer. The finitely extensible nonlinear elastic (FENE) spring force law in combination with a repulsive force defined as a power function (POW), called FENE-POW, is used to describe the elastic properties of the RBC membrane. The mechanical interaction between the lipid bilayer and the cytoskeleton is explicitly computed and incorporated into the vesicle model. Our model includes the fundamental mechanical properties of the RBC membrane, namely fluidity and bending rigidity of the lipid bilayer, and shear elasticity of the cytoskeleton while maintaining surface-area and volume conservation constraint. We present three simulation examples to demonstrate the effectiveness of this hybrid continuum-coarse-grained model for the study of RBCs in fluid flows.
Continuum spectra in light-ion reactions
Energy Technology Data Exchange (ETDEWEB)
Tamura, T.; Udagawa, T. [Texas Univ., Austin (USA). Dept. of Physics; Ikegami, H.; Muraoka, M [eds.
1980-01-01
Recent developments in the use of multi-step direct reaction method, to fit continuum cross sections of light-ion reactions, are reviewed. There has been a long-standing difficulty in reproducing sufficiently large (p, p') continuum cross section, but it has now been all but removed. It will be discussed in some detail, how this was achieved. Analyses of very recent data on analyzing powers in the continuum of (p, p') and (p, ..cap alpha..) reactions will also be discussed. Finally, analysis of the breakup of h into d and p will be presented.
Area Regge calculus and continuum limit
International Nuclear Information System (INIS)
Khatsymovsky, V.M.
2002-01-01
Encountered in the literature generalisations of general relativity to independent area variables are considered, the discrete (generalised Regge calculus) and continuum ones. The generalised Regge calculus can be either with purely area variables or, as we suggest, with area tensor-connection variables. Just for the latter, in particular, we prove that in analogy with corresponding statement in ordinary Regge calculus (by Feinberg, Friedberg, Lee and Ren), passing to the (appropriately defined) continuum limit yields the generalised continuum area tensor-connection general relativity
Clemens, J. D.; Stevens, G.; Frei, D.; Joseph, C. S. A.
2017-12-01
The Saldanha eruption centre, on the West Coast of South Africa, consists of 542 Ma, intracaldera, S-type, rhyolite ignimbrites divided into the basal Saldanha Ignimbrite and the partly overlying Jacob's Bay Ignimbrite. Depleted-mantle Nd model ages suggest magma sources younger than the Early Mesoproterozoic, and located within the Neoproterozoic Malmesbury Group and Swartland complex metasedimentary and metavolcanic rocks that form the regional basement. The Sr isotope systematics suggest that the dominant source rocks were metavolcaniclastic rocks and metagreywackes, and that the magmas formed from separate batches extracted from the same heterogeneous source. No apparent magma mixing trends relate the Saldanha to the Jacob's Bay Ignimbrites, or either of these to the magmas that formed the Plankiesbaai or Tsaarsbank Ignimbrites in the neighbouring Postberg eruption centre. The magmas were extracted from their source rocks carrying small but significant proportions of peritectic and restitic accessory minerals. Variations in the content of this entrained crystal cargo were responsible for most of the chemical variations in the magmas. Although we cannot construct a cogent crystal fractionation model to relate these groups of magmas, at least some crystal fractionation occurred, as an overlay on the primary signal due to peritectic assemblage entrainment (PAE). Thus, the causes of the cryptic chemical variation among the ignimbrite magmas of the Saldanha centre are variable, but dominated by the compositions of the parent melts and PAE. The preservation of clear, source-inherited chemical signatures, in individual samples, calls into question the common interpretation of silicic calderas as having been formed in large magma reservoirs, with magma compositions shaped by magma mingling, mixing, and fractional crystallization. The Saldanha rocks suggest a more intimate connection between source and erupted magma, and perhaps indicate that silicic magmas are too
A 3D Orthotropic Elastic Continuum Damage Material Model
Energy Technology Data Exchange (ETDEWEB)
English, Shawn Allen [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Brown, Arthur A. [Sandia National Lab. (SNL-CA), Livermore, CA (United States)
2013-08-01
A three dimensional orthotropic elastic constitutive model with continuum damage is implemented for polymer matrix composite lamina. Damage evolves based on a quadratic homogeneous function of thermodynamic forces in the orthotropic planes. A small strain formulation is used to assess damage. In order to account for large deformations, a Kirchhoff material formulation is implemented and coded for numerical simulation in Sandiaās Sierra Finite Element code suite. The theoretical formulation is described in detail. An example of material parameter determination is given and an example is presented.
Parker, Don F.; White, John C.; Ren, Minghua; Barnes, Melanie
2017-11-01
Voluminous silicic lava flows, erupted 37.4 Ma from widespread centers within the Davis Mountains Volcanic Field (DMVF), covered approximately 10,000 km2 with an initial volume as great as 1000 km3. Lava flows form three major stratigraphic units: the Star Mountain Rhyolite (minimum 220 km3) of the eastern Davis Mountains and adjacent Barilla Mountains, the Crossen Formation ( 75 km3) of the southern Davis Mountains, and the Bracks Rhyolite ( 75 km3) of the Rim Rock region west of the Davis Mountains proper. Similar extensive rhyolite lava also occurs in slightly younger units (Adobe Canyon Rhyolite, 125 km3, 37.1 Ma), Sheep Pasture Formation ( 125 km3, 36 Ma) and, less voluminously, in the Paisano central volcano ( 36.9 Ma) and younger units in the Davis Mountains. Individual lava flows from these units formed fields as extensive as 55 km and 300-m-thick. Flood rhyolite lavas of the Davis Mountains are marginally peralkaline quartz trachyte to low-silica rhyolite. Phenocrysts include alkali feldspar, clinopyroxene, FeTi oxides, and apatite, and, rarely, fayalite, as well as zircon in less peralkaline units. Many Star Mountain flows may be assigned to one of four geochemical groupings. Temperatures were moderately high, ranging from 911 to 860 Ā°C in quartz trachyte and low silica rhyolite. We suggest that flood rhyolite magma evolved from trachyte magma by filter pressing processes, and trachyte from mafic magma in deeper seated plutons. The Davis Mountains segment of Trans-Pecos Texas overlies Grenville basement and is separated from the older Southern Granite and Rhyolite Province to the north by the Grenville Front, and from the younger Coahuila terrane to the south by the Ouachita Front. We suggest that basement structure strongly influenced the timing and nature of Trans-Pecos magmatism, probably in varying degrees of impeding the ascent of mantle-derived mafic magmas, which were produced by upwelling of asthenospheric mantle above the foundered Farallon slab
Commitment to Quality throughout the Continuum.
Gillet, Pamela
1995-01-01
This editorial by the president of the Council for Exceptional Children indicates the organization's support of a continuum of special education placements for students with special needs and calls for improving transition of students from one placement to another. (JDD)
Computational Method for Atomistic-Continuum Homogenization
National Research Council Canada - National Science Library
Chung, Peter
2002-01-01
The homogenization method is used as a framework for developing a multiscale system of equations involving atoms at zero temperature at the small scale and continuum mechanics at the very large scale...
Dokuz, Abdurrahman; KĆ¼lekĆ§i, Elif; AydÄ±nĆ§akÄ±r, Emre; Kandemir, Raif; Cihat AlĆ§iĆ§ek, M.; Pecha, Mark E.; SĆ¼nnetĆ§i, Kadir
2017-05-01
The Cebre Rhyolite with an outcropping area up to 12 km2 is one of the rare extrusions in the Variscan basement of the Sakarya Zone. The unit consists of high-K calc alkaline rhyolites (SiO2 = 74-82 wt.%). Abundant phenocrysts of quartz and K-feldspar are accompanied by subordinate cordierite phenocrysts, rare muscovite microphenocrysts and biotite microcrysts set in a fine-grained groundmass. Three types of rock fragments (xenoliths) have been recognized; (i) porphyritic, (ii) equigranular hypabyssal and (iii) hypocrystalline fragments. Zircon U-Pb dating indicates that the Cebre Rhyolite was extruded at 332.8 Ā± 4.38 Ma, which post-dates the Variscan low temperature metamorphism and pre-dates the emplacement of I-type granitic intrusions (325-303 Ma).The samples are strongly peraluminous with A/CNK values ranging from 1.48 to 2.95 and A/NK from 1.49 to 2.99. They have very high K2O (3.72-7.42 wt.%) and Al2O3 (10.77-14.11 wt.%) contents, but very low CaO (0.02-0.21 wt.%), Na2O (0.05-0.78 wt.%) and MgO (0.3-0.21 wt.%) contents. The samples show geochemical affinity with the upper continental crust, e.g., enrichment of large ion lithophile elements (LILEs; K, Rb, U, Th, Pb), depletion of high field strength elements (HFSEs; Nb, Ta, Ti), Sr, P and Eu, but ŌNd(t) values (- 3.06 to - 8.75) and isotope ratios of Sr(t)(87Sr/86Sr = 0.70499-0.70915) and Pb(t) (206Pb/204Pb = 16.41-17.570, 207Pb/204Pb = 15.54-15.59, 208Pb/204Pb = 36.20-37.22) are similar to those of the lower crust. Geochemical and isotope data indicate that the Cebre Rhyolite was generated by melting of metapelitic rocks with some addition of intermediate metaigneous derived magma. As a geodynamic model, we propose that the Variscan Orogeny in Turkey was occurred by collision of Gondwana with an arc/terrane separated from the southern margin of Laurussia. This collision was followed shortly after by splitting of oceanic lithosphere into two pieces and sinking down into asthenosphere. Rapid upwelling of
Energy Technology Data Exchange (ETDEWEB)
Mothes, Patricia A; Hall, Minard L [Instituto Geofisico, Escuela Politecnica Nacional, Quito (Ecuador)], E-mail: pmothes@igepn.edu.ec
2008-10-01
In the Ecuadorian volcanic arc a cluster of scattered rhyolitic and dacitic centers within the mainly andesitic Eastern Cordillera includes large caldera structures (Chalupas, Chacana, Cosanga) as well as smaller edifices, built upon the Paleozoic-Mesozoic metamorphic basement. At the Chacana caldera magmatism dates from 2.7 Ma to historic times. These centers erupted enormous ash flows and thick pumice lapilli falls that covered the InterAndean Valley near Quito. The role of the 50-70 km-thick crust with a notable negative gravity anomaly appears to be related to the generation of this highly silicic magmatism occurring along the crest of the Andes in the NVZ.
Arakawa, Yoji; Endo, Daisuke; Ikehata, Kei; Oshika, Junya; Shinmura, Taro; Mori, Yasushi
2017-03-01
We examined the petrography, petrology, and geochemistry of two types of gabbroic xenoliths (A- and B-type xenoliths) in olivine basalt and biotite rhyolite units among the dominantly rhyolitic rocks in Niijima volcano, northern Izu-Bonin volcanic arc, central Japan. A-type gabbroic xenoliths consisting of plagioclase, clinopyroxene, and orthopyroxene with an adcumulate texture were found in both olivine basalt and biotite rhyolite units, and B-type gabbroic xenoliths consisting of plagioclase and amphibole with an orthocumulate texture were found only in biotite rhyolite units. Geothermal- and barometricmodelling based on mineral chemistry indicated that the A-type gabbro formed at higher temperatures (899-955Ā°C) and pressures (3.6-5.9 kbar) than the B-type gabbro (687-824Ā°C and 0.8-3.6 kbar). These findings and whole-rock chemistry suggest different parental magmas for the two types of gabbro. The A-type gabbro was likely formed from basaltic magma, whereas the B-type gabbro was likely formed from an intermediate (andesitic) magma. The gabbroic xenoliths in erupted products at Niijima volcano indicate the presence of mafic to intermediate cumulate bodies of different origins at relatively shallower levels beneath the dominantly rhyolitic volcano.
Directory of Open Access Journals (Sweden)
Arakawa Yoji
2017-03-01
Full Text Available We examined the petrography, petrology, and geochemistry of two types of gabbroic xenoliths (A- and B-type xenoliths in olivine basalt and biotite rhyolite units among the dominantly rhyolitic rocks in Niijima volcano, northern Izu-Bonin volcanic arc, central Japan. A-type gabbroic xenoliths consisting of plagioclase, clinopyroxene, and orthopyroxene with an adcumulate texture were found in both olivine basalt and biotite rhyolite units, and B-type gabbroic xenoliths consisting of plagioclase and amphibole with an orthocumulate texture were found only in biotite rhyolite units. Geothermal- and barometricmodelling based on mineral chemistry indicated that the A-type gabbro formed at higher temperatures (899ā955Ā°C and pressures (3.6ā5.9 kbar than the B-type gabbro (687ā824Ā°C and 0.8ā3.6 kbar. These findings and whole-rock chemistry suggest different parental magmas for the two types of gabbro. The A-type gabbro was likely formed from basaltic magma, whereas the B-type gabbro was likely formed from an intermediate (andesitic magma. The gabbroic xenoliths in erupted products at Niijima volcano indicate the presence of mafic to intermediate cumulate bodies of different origins at relatively shallower levels beneath the dominantly rhyolitic volcano.
Continuum emission from classical nova winds
International Nuclear Information System (INIS)
Harkness, R.P.
1983-01-01
The emergent continuum of a slow classical nova during outburst is considered in the quasi-steady optically thick, transonic wind model. Models are presented for various steady mass loss rates and are related to the evolution of slow novae during decline and early post-maximum. The continuum emission is found to depart radically from a blackbody spectrum and to exhibit features common to highly extended stellar atmospheres. (author)
Loop quantization as a continuum limit
International Nuclear Information System (INIS)
Manrique, Elisa; Oeckl, Robert; Weber, Axel; Zapata, Jose A
2006-01-01
We present an implementation of Wilson's renormalization group and a continuum limit tailored for loop quantization. The dynamics of loop-quantized theories is constructed as a continuum limit of the dynamics of effective theories. After presenting the general formalism we show as a first explicit example the 2D Ising field theory, an interacting relativistic quantum field theory with local degrees of freedom quantized by loop quantization techniques
Geometric continuum regularization of quantum field theory
International Nuclear Information System (INIS)
Halpern, M.B.
1989-01-01
An overview of the continuum regularization program is given. The program is traced from its roots in stochastic quantization, with emphasis on the examples of regularized gauge theory, the regularized general nonlinear sigma model and regularized quantum gravity. In its coordinate-invariant form, the regularization is seen as entirely geometric: only the supermetric on field deformations is regularized, and the prescription provides universal nonperturbative invariant continuum regularization across all quantum field theory. 54 refs
Continuum of active nuclei of galaxies
International Nuclear Information System (INIS)
Boisson, C.; Durret, F.
1987-01-01
Most of the luminosity of active galactic nuclei (NAG) is radiated in the form of a continuum extending from radio to X-ray energies. It is important to understand the origin of this continuum in order to explain the relative importance of thermal and non-thermal processes in the different classes of NAG. We present here the observational aspect. A detailed study of the mechanisms will be presented by J.L. Masnou [fr
Shear-induced Bubble Coalescence in Rhyolitic Melts with Low Vesicularity
Okumura, S.; Nakamura, M.; Tsuchiyama, A.
2006-12-01
Development of bubble structure during magma ascent controls the dynamics of volcanic eruption, because the bubble structure influences the magma rheology and permeability, and hence magma degassing. In the flowing magmas, the bubble structure is expected to be changed by shear, as pointed out by some previous studies based on geological observations. However, the development of bubble structure has been experimentally studied only in the isostatic magmas. We have experimentally demonstrated for the first time, the shear-induced development of number density, size and shape of bubbles in a rhyolitic melt. The deformation experiments were performed by using an externally heated, piston-cylinder type apparatus with a rotational piston. At 975Ā°C, natural obsidian (initial water content of 0.5 wt%) having cylindrical shape (ca. 4.7 mm in diameter and 5 mm in length) was vesiculated in the graphite container (ca. 5 and 9 mm in the inner and the outer diameters, respectively, and 5 mm in length), and the vesiculated samples were twisted at various rotational speeds up to 1 rpm. The number density, size and shape of bubbles in the quenched samples were then measured by using the X-ray computed tomography. The size distribution of bubbles shows that the number of larger bubbles increases with the rotational speed and at the outer zone of the samples at which the shear rate is high. In the high shear rate zone, the magnitude of bubble deformation is large. The 3D images of large bubbles clearly indicate that they were formed by coalescence. These results indicate that the degree of bubble coalescence is enhanced with the shear rate. The experimental results also demonstrated that the coalescence of bubbles occur even at low vesicularity (ca. 20 vol.%). Because the shear rate induced in this study (in the order of 0.01 1/s) seems to be produced for magmas ascending in a volcanic conduit, we propose the possibility that the vesiculated magmas undergo bubble coalescence at a
Hydration of Rhyolitic Glasses: Comparison Between High- and Low-Temperature Processes
Anovitz, L.; Fayek, M.; Cole, D. R.; Carter, T.
2012-12-01
While a great deal is known about the interaction between water and rhyolitic glasses and melts at temperatures above the glass transition, the nature of this interaction at lower temperatures is more obscure. Comparisons between high- and low-temperature diffusive studies suggest that several factors play an important role under lower-temperatures conditions that are not significant at higher temperatures. Surface concentrations, which equilibrate quickly at high temperature, change far more slowly as temperatures decrease, and may not equilibrate at room temperature for hundreds or thousands of years. Coupled with temperature-dependent diffusion coefficients this complicates calculation of diffusion profiles as a function of time. A key factor in this process appears to be the inability of "self-stress", caused by the in-diffusing species, to relax at lower temperatures, a result expected below the glass transition. Regions of the glass hydrated at low temperatures are strongly optically anisotropic, and preliminary calculations suggest that the magnitude of stress involved may be very high. On the microstuctural scale, extrapolations of high-temperature FTIR data to lower temperatures suggests there should be little or no hydroxyl present in glasses "hydrated" at low temperatures. Analyses of both block and powder samples suggest that this is generally true in the bulk of the hydrated glass, excluding hydroxyl groups that formed during the initial cooling of the melt. However, hydroxyl do groups appear to be present at the glass surface, where both SIMS and neutron reflectometry data suggest hydration levels may be higher than projected from the bulk of the glass. Isotopic exchange experiments also suggest that bonding is relatively weak, as hydration water exchanges readily with the enviroment. All of these observations lead to the conclusion that the observed stress is due to the presence of interstructural, rather than bonded, water. This likely explains the
Watts, Kathryn E.; John, David A.; Colgan, Joseph P.; Henry, Christopher D.; Bindeman, Ilya N.; Schmitt, Axel K.
2016-01-01
Late Cenozoic faulting and large-magnitude extension in the Great Basin of the western USA has created locally deep windows into the upper crust, permitting direct study of volcanic and plutonic rocks within individual calderas. The Caetano caldera in northācentral Nevada, formed during the mid-Tertiary ignimbrite flare-up, offers one of the best exposed and most complete records of caldera magmatism. Integrating whole-rock geochemistry, mineral chemistry, isotope geochemistry and geochronology with field studies and geologic mapping, we define the petrologic evolution of the magmatic system that sourced the >1100 km3Caetano Tuff. The intra-caldera Caetano Tuff is up to ā¼5 km thick, composed of crystal-rich (30ā45 vol. %), high-silica rhyolite, overlain by a smaller volume of comparably crystal-rich, low-silica rhyolite. It defies classification as either a monotonous intermediate or crystal-poor zoned rhyolite, as commonly ascribed to ignimbrite eruptions. Crystallization modeling based on the observed mineralogy and major and trace element geochemistry demonstrates that the compositional zonation can be explained by liquidācumulate evolution in the Caetano Tuff magma chamber, with the more evolved lower Caetano Tuff consisting of extracted liquids that continued to crystallize and mix in the upper part of the chamber following segregation from a cumulate-rich, and more heterogeneous, source mush. The latter is represented in the caldera stratigraphy by the less evolved upper Caetano Tuff. Whole-rock major, trace and rare earth element geochemistry, modal mineralogy and mineral chemistry, O, Sr, Nd and Pb isotope geochemistry, sanidine ArāAr geochronology, and zircon UāPb geochronology and trace element geochemistry provide robust evidence that the voluminous caldera intrusions (Carico Lake pluton and Redrock Canyon porphyry) are genetically equivalent to the least evolved Caetano Tuff and formed from magma that remained in the lower chamber after
Watts, Kathryn E.; John, David A.; Colgan, Joseph P.; Henry, Christopher D.; Bindeman, Ilya N.; Schmitt, Axel K.
2016-01-01
Late Cenozoic faulting and large-magnitude extension in the Great Basin of the western USA has created locally deep windows into the upper crust, permitting direct study of volcanic and plutonic rocks within individual calderas. The Caetano caldera in northācentral Nevada, formed during the mid-Tertiary ignimbrite flare-up, offers one of the best exposed and most complete records of caldera magmatism. Integrating whole-rock geochemistry, mineral chemistry, isotope geochemistry and geochronology with field studies and geologic mapping, we define the petrologic evolution of the magmatic system that sourced the >1100 km3Caetano Tuff. The intra-caldera Caetano Tuff is up to ā¼5 km thick, composed of crystal-rich (30ā45 vol. %), high-silica rhyolite, overlain by a smaller volume of comparably crystal-rich, low-silica rhyolite. It defies classification as either a monotonous intermediate or crystal-poor zoned rhyolite, as commonly ascribed to ignimbrite eruptions. Crystallization modeling based on the observed mineralogy and major and trace element geochemistry demonstrates that the compositional zonation can be explained by liquidācumulate evolution in the Caetano Tuff magma chamber, with the more evolved lower Caetano Tuff consisting of extracted liquids that continued to crystallize and mix in the upper part of the chamber following segregation from a cumulate-rich, and more heterogeneous, source mush. The latter is represented in the caldera stratigraphy by the less evolved upper Caetano Tuff. Whole-rock major, trace and rare earth element geochemistry, modal mineralogy and mineral chemistry, O, Sr, Nd and Pb isotope geochemistry, sanidine ArāAr geochronology, and zircon UāPb geochronology and trace element geochemistry provide robust evidence that the voluminous caldera intrusions (Carico Lake pluton and Redrock Canyon porphyry) are genetically equivalent to the least evolved Caetano Tuff and formed from magma that remained in the lower chamber after
Changing public stigma with continuum beliefs.
Corrigan, Patrick W; Schmidt, Annie; Bink, Andrea B; Nieweglowski, Katherine; Al-Khouja, Maya A; Qin, Sang; Discont, Steve
2017-10-01
Given the egregious effect of public stigma on the lives of people with mental illness, researchers have sought to unpack and identify effective components of anti-stigma programs. We expect to show that continuum messages have more positive effect on stigma and affirming attitudes (beliefs that people with mental illness recover and should be personally empowered) than categorical perspectives. The effect of continuum beliefs will interact with contact strategies. A total of 598 research participants were randomly assigned to online presentations representing one of the six conditions: three messages (continuum, categorical, or neutral control) by two processes (education or contact). Participants completed measures of continuum beliefs (as a manipulation check), stigma and affirming attitudes after viewing the condition. Continuum messages had significantly better effect on views that people with mental illness are "different," a finding that interacted with contact. Continuum messages also had better effects on recovery beliefs, once again an effect that interacted significantly with contact. Implications of these findings for improving anti-stigma programs are discussed.
Charreteur, Gilles; Tegner, Christian
2013-06-01
The RauĆ°afell composite complex is part of the Neogene BreiĆ°dalur volcano, eastern Iceland and is composed of a composite feeder dyke, a vent structure and a composite flow. The two end-members of the composite complex are rhyolite and basalt, and both are rich in plagioclase macrocrysts: bytownite in basalt and oligoclase in rhyolite. The rhyolite also includes ferroaugite macrocrysts. The mixed rocks are separated in three textural groups related to mixing proportions. When the basaltic end-member is dominant, a hybrid texture with a homogeneous matrix is observed and the only evidence of mixing is the presence of antecrysts of both end-members. When the basaltic end-member represents c. 65 to 30 % of the mixture, we observe emulsion textures composed of finely co-mingled basalt and rhyolite. The difference between these two textural expressions of mixing is due to effects of diffusion. The third texture shows mafic enclaves suspended in a rhyolitic matrix. In these rocks, the proportion of the basaltic end-member is inferior to 30 %, implying that the basalt froze solid in contact with the rhyolite. Zoning of plagioclase shows that the mixing processes are driven initially by highly efficient micro-mingling; the emulsification is possibly a result of compositional gradient stresses (Korteweg stress) between miscible basalt and rhyolite. This is followed by chemical diffusion (hybridisation) and tend to protect antecrysts from reaction with the primitive magmas. When antecrysts originated in the evolved magma, they undergo dissolution due to thermal disequilibrium during mingling and chemical disequilibrium during hybridisation. We argue that such mixing processes are important in producing intermediate rocks in Iceland and elsewhere that shows only the chemical attributes of an origin by mixing. The preservation of emulsion textures is rare and highly dependent on cooling history.
Ondrejka, Martin; Li, Xian-Hua; Vojtko, Rastislav; Putis, Marian; Uher, Pavel; SobockĆ½, Tomas
2018-04-01
Three representative A-type rhyolitic rock samples from the MurĆ”Å Nappe of the inferred Silicic Unit of the Inner Western Carpathians (Slovakia) were dated using the high-precision SIMS U-Pb isotope technique on zircons. The geochronological data presented in this paper is the first in-situ isotopic dating of these volcanic rocks. Oscillatory zoned zircon crystals mostly revealed concordant Permian (Guadalupian) ages: 266.6 Ā± 2.4 Ma in Tisovec-Rejkovo (TIS-1), 263.3 Ā± 1.9 Ma in TelgĆ”rt-GregovĆ” Hill (TEL-1) and 269.5 Ā± 1.8 Ma in VeÄ¾kĆ” StoÅ¾ka-Dudlavka (SD-2) rhyolites. The results indicate that the formation of A-type rhyolites and their plutonic equivalents are connected to magmatic activity during the Permian extensional tectonics and most likely related to the Pangea supercontinent break-up.
Exceptional mobility of an advancing rhyolitic obsidian flow at CordĆ³n Caulle volcano in Chile.
Tuffen, Hugh; James, Mike R; Castro, Jonathan M; Schipper, C Ian
2013-01-01
The emplacement mechanisms of rhyolitic lava flows are enigmatic and, despite high lava viscosities and low inferred effusion rates, can result in remarkably, laterally extensive (>30 km) flow fields. Here we present the first observations of an active, extensive rhyolitic lava flow field from the 2011-2012 eruption at CordĆ³n Caulle, Chile. We combine high-resolution four-dimensional flow front models, created using automated photo reconstruction techniques, with sequential satellite imagery. Late-stage evolution greatly extended the compound lava flow field, with localized extrusion from stalled, ~35 m-thick flow margins creating >80 breakout lobes. In January 2013, flow front advance continued ~3.6 km from the vent, despite detectable lava supply ceasing 6-8 months earlier. This illustrates how efficient thermal insulation by the lava carapace promotes prolonged within-flow horizontal lava transport, boosting the extent of the flow. The unexpected similarities with compound basaltic lava flow fields point towards a unifying model of lava emplacement.
Macias, J.; Arce, J.; Rueda, H.; Gardner, J.
2008-12-01
Tlaloc volcano is located at the northern tip of the Sierra Nevada Volcanic Range in Central Mexico. This Pleistocene to Recent volcanic range consists from north to south of Tlaloc-TelapĆ³n-Teyotl-IztaccĆhuatl-and- PopocatĆ©petl volcanoes. While andesitic to barely dacitic volcanism dominates the southern part of the range (i.e. PopocatĆ©petl and IztaccĆhuatl); dacitic and rare rhyolithic volcanism (i.e. TelapĆ³n, Tlaloc) dominates the northern end. The known locus of rhyolitic magmatism took place at Tlaloc volcano with a Plinian-Subplinian eruption that occurred 31 ka ago. The eruption emplaced the so-called multilayered fallout and pumiceous pyroclastic flows (~2 km3 DRE). The deposit consists of 95% vol. of juvenile particles (pumice + crystals) and minor altered lithics 5% vol. The mineral association of the pumice fragments (74-76 % wt. SiO2) consists of quartz + plagioclase + sanidine + biotite and rare oxides set in a glassy groundmass with voids. Melt inclusions in quartz phenocrysts suggest that prior to the eruption the rhyolitic contain ~7% of H2O and Nevado de Toluca volcano (~6 km) some 50 km to the southwest.
Sweetkind, Donald S.; Bova, Shiera C.
2015-01-01
Contaminants introduced into the subsurface of Pahute Mesa, Nevada National Security Site, by underground nuclear testing are of concern to the U.S. Department of Energy and regulators responsible for protecting human health and safety. The potential for contaminant movement away from the underground test areas at Pahute Mesa and into the accessible environment is greatest by groundwater transport through fractured volcanic rocks. The 12.9 Ma (mega-annums, million years) Calico Hills Formation, which consists of a mixture of rhyolite lava flows and intercalated nonwelded and bedded tuff and pyroclastic flow deposits, occurs in two areas of the Nevada National Security Site. One area is north of the Rainier Mesa caldera, buried beneath Pahute Mesa, and serves as a heterogeneous volcanic-rock aquifer but is only available to study through drilling and is not described in this report. A second accumulation of the formation is south of the Rainier Mesa caldera and is exposed in outcrop along the western boundary of the Nevada National Security Site at the Calico Hills near Yucca Mountain. These outcrops expose in three dimensions an interlayered sequence of tuff and lava flows similar to those intercepted in the subsurface beneath Pahute Mesa. Field description and geologic mapping of these exposures described lithostratigraphic variations within lava flows and assisted in, or at least corroborated, conceptualization of the rhyolite lava-bearing parts of the formation.
International Nuclear Information System (INIS)
Palin, J.M.; Epstein, S.; Stolper, E.M.
1996-01-01
Oxygen isotope partitioning between gaseous CO 2 and a natural rhyolitic glass and melt (77.7 wt% SiO 2 , 0.16 wt% H 2 O total ) has been measured at 550-950 degrees C and approximately 1 bar. Equilibrium oxygen isotope fractionation factors (Ī± CO2-rhyolite = ( 18 O/ 16 O) rhyolite ) determined in exchange experiments of 100-255 day duration. These values agree well with predictions based on experimentally determined oxygen isotope fractionation factors for CO 2 -silica glass and CO 2 -albitic glass/melt, if the rhyolitic glass is taken to be a simple mixture of normative silica and alkali feldspar components. The results indicate that oxygen isotope partitioning in felsic glasses and melts can be modeled by linear combinations of endmember silicate constituents. Rates of oxygen isotope exchange observed in the partitioning experiments are consistent with control by diffusion of molecular H 2 O dissolved in the glass/melt and are three orders of magnitude faster than predicted for rate control solely by diffusion of dissolved molecular CO 2 under the experimental conditions. Additional experiments using untreated and dehydrated (0.09 wt% H 2 O total ) rhyolitic glass quantatively support these interpretations. We conclude that diffusive oxygen isotope exchange in rhyolitic glass/melt, and probably other polymerized silicate materials, it controlled by the concentrations and diffusivities of dissolved oxygen-bearing volatile species rather than diffusion of network oxygen under all but the most volatile-poor conditions. 25 refs., 6 figs., 1 tab
Diffusion coefficients for Tl, Pb, Cd, In, Zn, Bi, As, Mo and Sb in hydrous rhyolite at 100-200 MPa
Berlo, Kim; Brooker, Richard; Wilke, Max
2014-05-01
A series of experiments have been conducted to determine the diffusivities of Tl, Pb, Cd, In, Zn, Bi, As, Mo and Sb in hydrous rhyolitic melt. Diffusion experiments used two adjoining glass cylinder of the same hydrous composition, one doped with the elements of interest at ~ 100 ppm. These couples were rapidly heated to 850, 1000 and 1150Ā°C at 100-200 MPa for a few hours. After quenching the sectioned charges were analyzed by both synchrotron XRF (The Diamond Light Source) and LA-ICP-MS (University of Oxford). The data shows excellent correlation between these two techniques. The diffusion profiles were fitted to a 1-D diffusion couple equation to determine the diffusivities and fitting to the different temperature runs defined the Arrhenius parameters. We find that for 850Ā°C the diffusion coefficients follow the trend Tl>Pb>Cd>Zn>In>Bi>As>Sb>Mo. Additional experiments were performed with either S or Cl added (to both sides of the diffusion couple). In general S increases the diffusion rate of all metals except Mo and Sb, which diffuse slower in the presence of S. Chlorine also speeds up the diffusion of metals with the exception of In, Mo and Sb. The systematic change in diffusivities of these metals and their different behaviour in the presence of the ligands that are also observed to be significant in volcanic gases, are important in determining the distribution of these metals during degassing (e.g. MacKenzie and Canil, 2008). This is particularly important in a dynamic environment such as a volcanic conduit. There are also implications for economic exploration and well as hazard mitigation.
Brugman, K. K.; Till, C. B.
2017-12-01
Eruption of the Scaup Lake Rhyolite (SCL) ended 220,000 years of dormancy at Yellowstone caldera and initiated the volcano's youngest sequence of eruptions [Christiansen et al., USGS, 2007]. SCL contains 14% phenocrysts (e.g., feldspar, quartz, pyroxene, zircon, Fe-Ti oxides) which exhibit disequilbrium textures that indicate multiple rejuvenation events occurred shortly before eruption. Our previous work using NanoSIMS elemental concentration profiles from clinopyroxene (cpx) intracrystalline zone boundaries as a diffusion dating tool supported our hypothesis that different minerals may not record the same series of pre-eruptive events, with the cpx rims recording older magmatic events (100s of years prior to eruption [Brugman et al., AGU, 2016]) relative to the sanidine rims (historical experimental data, and thus has not been included in existing cpx and cpx-liquid geothermometer calibrations. These geothermometers predict temperatures >40Ā°C in error of low-Al cpx-saturated experiments. A new regression of Putirka's [RiMG, 2008] cpx-liquid geothermometer calibrated with 64 experimentally-derived cpx of a similar composition to that of SCL increases the geothermometer's dependence on the Mg# and Na+K component of the liquid and decreases its dependence on the Ca+Si component of the liquid. This revised geothermometer reproduces experimental conditions to Ā±20Ā°C. This updated thermometer returns temperatures for SCL cpx 30Ā°C lower than the Putirka [RiMG, 2008] cpx-liquid geothermometer, thereby increasing the timescales previously reported for SCL cpx, and increasing the difference in timescales recorded by the SCL cpx and sanidine rims.
Karabinos, Michael Joseph
2015-01-01
This dissertation tests the universal suitability of the records continuum model by using two cases from the decolonization of Southeast Asia. The continuum model is a new model of records visualization invented in the 1990s that sees records as free to move throughout four ādimensionsā rather than
Defining and testing a granular continuum element
Energy Technology Data Exchange (ETDEWEB)
Rycroft, Chris H.; Kamrin, Ken; Bazant, Martin Z.
2007-12-03
Continuum mechanics relies on the fundamental notion of amesoscopic volume "element" in which properties averaged over discreteparticles obey deterministic relationships. Recent work on granularmaterials suggests a continuum law may be inapplicable, revealinginhomogeneities at the particle level, such as force chains and slow cagebreaking. Here, we analyze large-scale Discrete-Element Method (DEM)simulations of different granular flows and show that a "granularelement" can indeed be defined at the scale of dynamical correlations,roughly three to five particle diameters. Its rheology is rather subtle,combining liquid-like dependence on deformation rate and solid-likedependence on strain. Our results confirm some aspects of classicalplasticity theory (e.g., coaxiality of stress and deformation rate),while contradicting others (i.e., incipient yield), and can guide thedevelopment of more realistic continuum models.
Hyperbolic conservation laws in continuum physics
Dafermos, Constantine M
2016-01-01
This is a masterly exposition and an encyclopedic presentation of the theory of hyperbolic conservation laws. It illustrates the essential role of continuum thermodynamics in providing motivation and direction for the development of the mathematical theory while also serving as the principal source of applications. The reader is expected to have a certain mathematical sophistication and to be familiar with (at least) the rudiments of analysis and the qualitative theory of partial differential equations, whereas prior exposure to continuum physics is not required. The target group of readers would consist of (a) experts in the mathematical theory of hyperbolic systems of conservation laws who wish to learn about the connection with classical physics; (b) specialists in continuum mechanics who may need analytical tools; (c) experts in numerical analysis who wish to learn the underlying mathematical theory; and (d) analysts and graduate students who seek introduction to the theory of hyperbolic systems of conser...
Lattice gravity near the continuum limit
International Nuclear Information System (INIS)
Feinberg, G.; Friedberg, R.; Lee, T.D.; Ren, H.C.
1984-01-01
We prove that the lattice gravity always approaches the usual continuum limit when the link length l -> 0, provided that certain general boundary conditions are satisfied. This result holds for any lattice, regular or irregular. Furthermore, for a given lattice, the deviation from its continuum limit can be expressed as a power series in l 2 . General formulas for such a perturbative calculation are given, together with a number of illustrative examples, including the graviton propagator. The lattice gravity satisfies all the invariance properties of Einstein's theory of general relativity. In addition, it is symmetric under a new class of transformations that are absent in the usual continuum theory. The possibility that the lattice theory (with a nonzero l) may be more fundamental is discussed. (orig.)
Damby, David; Horwell, Claire J.; Larsen, Gudrun; Thordarson, Thorvaldur; Tomatis, Maura; Fubini, Bice; Donaldson, Ken
2017-01-01
BackgroundThe eruptions of EyjafjallajĆ¶kull (2010) and GrĆmsvĆ¶tn (2011), Iceland, triggered immediate, international consideration of the respiratory health hazard of inhaling volcanic ash, and prompted the need to estimate the potential hazard posed by future eruptions of Icelandās volcanoes to Icelandic and Northern European populations.Ā MethodsA physicochemical characterization and toxicological assessment was conducted on a suite of archived ash samples spanning the spectrum of past eruptions (basaltic to rhyolitic magmatic composition) of Icelandic volcanoes following a protocol specifically designed by the International Volcanic Health Hazard Network.Ā ResultsIcelandic ash can be of a respirable size (up to 11.3 vol.% < 4 Ī¼m), but the samples did not display physicochemical characteristics of pathogenic particulate in terms of composition or morphology. Ash particles were generally angular, being composed of fragmented glass and crystals. Few fiber-like particles were observed, but those present comprised glass or sodium oxides, and are not related to pathogenic natural fibers, like asbestos or fibrous zeolites, thereby limiting concern of associated respiratory diseases. None of the samples contained cristobalite or tridymite, and only one sample contained quartz, minerals of interest due to the potential to cause silicosis. Sample surface areas are low, ranging from 0.4 to 1.6 m2 gā1, which aligns with analyses on ash from other eruptions worldwide. All samples generated a low level of hydroxyl radicals (HOā¢), a measure of surface reactivity, through the iron-catalyzed Fenton reaction compared to concurrently analyzed comparative samples. However, radical generation increased after ārefreshingā sample surfaces, indicating that newly erupted samples may display higher reactivity. A composition-dependent range of available surface iron was measured after a 7-day incubation, from 22.5 to 315.7 Ī¼mol mā2, with mafic samples releasing more iron
Continuum gauge fields from lattice gauge fields
International Nuclear Information System (INIS)
Goeckeler, M.; Kronfeld, A.S.; Schierholz, G.; Wiese, U.J.
1993-01-01
On the lattice some of the salient features of pure gauge theories and of gauge theories with fermions in complex representations of the gauge group seem to be lost. These features can be recovered by considering part of the theory in the continuum. The prerequisite for that is the construction of continuum gauge fields from lattice gauge fields. Such a construction, which is gauge covariant and complies with geometrical constructions of the topological charge on the lattice, is given in this paper. The procedure is explicitly carried out in the U(1) theory in two dimensions, where it leads to simple results. (orig.)
Pingitore, N. E., Jr.; Clague, J. W.; Gorski, D.
2016-12-01
The technology metals Li and Be combine low mass and unique properties. Li batteries are critical in applications at scales from micro-electronics to automotive and grid storage. Low mass Be structural components are essential in aerospace/defense applications and in non-sparking BeCu alloy oilfield tools. Most Li is sourced from desert salarsin the "Lithium Triangle" of ArgentinaāBoliviaāChile. In contrast, Materion Corp mines >80% of global Be at Spor Mountain, UT. The massive peraluminous rhyolite heavy rare earth deposit at Round Top Mountain, TX is also enriched in Li, 500 ppm, and Be, 50 ppm. 2016 prices of 7000/tonne Li2CO3 (19% Li) and 1000/kg Be metal suggest favorable economics to extract Li and Be as by-products of HREE mining. Li and some Be are hosted in annite biotite that comprises up to 5% of the rhyolite. Texas Mineral Resources Corp proposes to heap leach crushed rhyolite with dilute H2SO4to release the yttrofluorite-hosted HREEs. At bench scale the annite biotite dissolves, but not quartz and feldspars (>90% of the rock). A series of 40 high-yield laboratory tests at various acid strength, particle size, and exposure time released up to 350 ppm (70%) of the Li and 14 ppm (30%) of the Be. For a 20,000 tonne/day operation, these recoveries correspond to daily production of >3 tonnes Li and 250 kg Be. Higher Li and Be recoveries also increased yields of gangue elements, Fe & Al, into solution. This complicates subsequent separation of Li, Be, and HREEs from the pregnant leach solution. Recovery of target HREEs did not increase beyond 200 ppm Li and 8 ppm Be recovery. Greater Li and Be recoveries increased acid consumption. Thus the "sweet spot" economics for heap leach is likely under conditions of acid strength, grain size, and exposure time that do not maximize by-product Li and Be recoveries. Evolving market prices for the full target element suite and additional costs to recover and purify the Li and Be must also be considered.
Bakker, L.; Lowe, D.J.; Jongmans, A.G.
1996-01-01
The influence of time as a soil forming factor was studied on an evolutionary sequence of five soils (1850 radiocarbo years BP-ca. 120,000 BP) developed in rhyolitic tephra deposits in New Zealand. New micromorphological observations were combined with existing macromorphological, chemical,
Chipera, Steve J.; Goff, Fraser; Goff, Cathy J.; Fittipaldo, Melissa
2008-12-01
Quantitative X-ray diffraction analysis of about 80 rhyolite and associated lacustrine rocks has characterized previously unrecognized zeolitic alteration throughout the Valles caldera resurgent dome. The alteration assemblage consists primarily of smectite-clinoptilolite-mordenite-silica, which replaces groundmass and fills voids, especially in the tuffs and lacustrine rocks. Original rock textures are routinely preserved. Mineralization typically extends to depths of only a few tens of meters and resembles shallow "caldera-type zeolitization" as defined by Utada et al. [Utada, M., Shimizu, M., Ito, T., Inoue, A., 1999. Alteration of caldera-forming rocks related to the Sanzugawa volcanotectonic depression, northeast Honshu, Japan ā with special reference to "caldera-type zeolitization." Resource Geol. Spec. Issue No. 20, 129-140]. Geology and 40Ar/ 39Ar dates limit the period of extensive zeolite growth to roughly the first 30 kyr after the current caldera formed (ca. 1.25 to 1.22 Ma). Zeolitic alteration was promoted by saturation of shallow rocks with alkaline lake water (a mixture of meteoric waters and degassed hydrothermal fluids) and by high thermal gradients caused by cooling of the underlying magma body and earliest post-caldera rhyolite eruptions. Zeolitic alteration of this type is not found in the later volcanic and lacustrine rocks of the caldera moat (ā¤ 0.8 Ma) suggesting that later lake waters were cooler and less alkaline. The shallow zeolitic alteration does not have characteristics resembling classic, alkaline lake zeolite deposits (no analcime, erionite, or chabazite) nor does it contain zeolites common in high-temperature hydrothermal systems (laumontite or wairakite). Although aerially extensive, the early zeolitic alteration does not form laterally continuous beds and are consequently, not of economic significance.
Continuum emission of excited sodium dimer
International Nuclear Information System (INIS)
Pardo, A.; Poyato, J.M.L.; Alonso, J.I.; Rico, F.R.
1980-01-01
A study has been made of the behaviour of excited molecular sodium using high-power Ar + laser radiation. A continuum emission was observed in the red wavelength region. This emission was thought to be caused by the formation of excited triatomic molecules. Energy transfer was observed from excited molecules to atoms. (orig.)
Discrete expansions of continuum wave functions
International Nuclear Information System (INIS)
Bang, J.; Ershov, S.N.; Gareev, F.A.; Kazacha, G.S.
1980-01-01
Different methods of expanding continuum wave functions in terms of discrete basis sets are discussed. The convergence properties of these expansions are investigated, both from a mathematical and a numerical point of view, for the case of potentials of Woods-Saxon and square well type. (orig.)
Asteroid-comet continuum objects in the solar system.
Hsieh, Henry H
2017-07-13
In this review presented at the Royal Society meeting, 'Cometary science after Rosetta', I present an overview of studies of small solar system objects that exhibit properties of both asteroids and comets (with a focus on so-called active asteroids). Sometimes referred to as 'transition objects', these bodies are perhaps more appropriately described as 'continuum objects', to reflect the notion that rather than necessarily representing actual transitional evolutionary states between asteroids and comets, they simply belong to the general population of small solar system bodies that happen to exhibit a continuous range of observational, physical and dynamical properties. Continuum objects are intriguing because they possess many of the properties that make classical comets interesting to study (e.g. relatively primitive compositions, ejection of surface and subsurface material into space where it can be more easily studied, and orbital properties that allow us to sample material from distant parts of the solar system that would otherwise be inaccessible), while allowing us to study regions of the solar system that are not sampled by classical comets.This article is part of the themed issue 'Cometary science after Rosetta'. Ā© 2017 The Author(s).
Damby, David E; Horwell, Claire J; Larsen, Gudrun; Thordarson, Thorvaldur; Tomatis, Maura; Fubini, Bice; Donaldson, Ken
2017-09-11
The eruptions of EyjafjallajĆ¶kull (2010) and GrĆmsvĆ¶tn (2011), Iceland, triggered immediate, international consideration of the respiratory health hazard of inhaling volcanic ash, and prompted the need to estimate the potential hazard posed by future eruptions of Iceland's volcanoes to Icelandic and Northern European populations. A physicochemical characterization and toxicological assessment was conducted on a suite of archived ash samples spanning the spectrum of past eruptions (basaltic to rhyolitic magmatic composition) of Icelandic volcanoes following a protocol specifically designed by the International Volcanic Health Hazard Network. Icelandic ash can be of a respirable size (up to 11.3 vol.%Ā fiber-like particles were observed, but those present comprised glass or sodium oxides, and are not related to pathogenic natural fibers, like asbestos or fibrous zeolites, thereby limiting concern of associated respiratory diseases. None of the samples contained cristobalite or tridymite, and only one sample contained quartz, minerals of interest due to the potential to cause silicosis. Sample surface areas are low, ranging from 0.4 to 1.6Ā m 2 Ā g -1 , which aligns with analyses on ash from other eruptions worldwide. All samples generated a low level of hydroxyl radicals (HO ā¢ ), a measure of surface reactivity, through the iron-catalyzed Fenton reaction compared to concurrently analyzed comparative samples. However, radical generation increased after 'refreshing' sample surfaces, indicating that newly erupted samples may display higher reactivity. A composition-dependent range of available surface iron was measured after a 7-day incubation, from 22.5 to 315.7Ā Ī¼mol m -2 , with mafic samples releasing more iron than silicic samples. All samples were non-reactive in a test of red blood cell-membrane damage. The primary particle-specific concern is the potential for future eruptions of Iceland's volcanoes to generate fine, respirable material and, thus, to
McCurry, M. O.; Pearson, D. M.; Welhan, J. A.; Kobs-Nawotniak, S. E.; Fisher, M. A.
2014-12-01
The Snake River Plain and neighboring regions are well known for their high heat flow and robust Neogene-Quaternary tectonic and magmatic activity. Interestingly, however, there are comparatively few surficial manifestations of geothermal activity. This study is part of a renewed examination of this region as a possible hidden or blind geothermal resource. We present a testable, integrated volcanological, petrogenetic, tectonic and hydrothermal conceptual model for 57 ka China Hat and cogenetic topaz rhyolite lava domes of the Blackfoot Volcanic Field. This field is well suited for analysis as a blind resource because of its distinctive combination of (1) young bimodal volcanism, petrogenetic evidence of shallow magma storage and evolution, presence of coeval extension, voluminous travertine deposits, and C- and He-isotopic evidence of active magma degassing; (2) a paucity of hot springs or other obvious indicators of a geothermal resource in the immediate vicinity of the lava domes; and (3) proximity to a region of high crustal heat flow, high-T geothermal fluids at 2.5-5 km depth and micro-seismicity characterized by its swarming nature. Eruptions of both basalt and rhyolite commonly evolve from minor phreatomagmatic to effusive. In our model, transport of both magmatic and possible deep crustal aqueous fluids may be controlled by preexisting crustal structures, including west-dipping thrust faults. Geochemical evolution of rhyolite magma is dominated by mid- to upper-crustal fractional crystallization (with pre-eruption storage and phenocryst formation at ~14 km). Approximately 1.2 km3 of topaz rhyolite have been erupted since 1.4 Ma, yielding an average eruption rate of 0.8 km3/m.y. Given reasonable assumptions of magma cumulate formation and eruption rates, and initial and final volatile concentrations, we infer average H2O and CO2 volatile fluxes from the rhyolite source region of ~2MT/year and 340 T/day, respectively. Lithium flux may be comparable to CO2.
Continuum emission in the 1980 July 1 solar flare
International Nuclear Information System (INIS)
Zirin, H.; Neidig, D.F.
1981-01-01
Comparison of continuum measurements of the 1980 July 1 flare at Big Bear Solar Observatory and Sacramento Peak Observatory show strong blue emission kernels with the ratio of Balmer continuum (Bac):lambda3862 continuum:continuum above 4275 A to be about 10:5:1. The blue continuum at 3862 A is too strong to be explained by unresolved lines. The Bac intensity was 2.5 times the photosphere and the strongest lambda3862 continuum was 2 times the photosphere. The brightest continuum kernel occurred late in the flare, after the hard X-ray peak and related in time to an isolated peak in the 2.2 MeV line, suggesting that the continuum was excited by protons above 20 MeV
A Coupling Tool for Parallel Molecular Dynamics-Continuum Simulations
Neumann, Philipp; Tchipev, Nikola
2012-01-01
We present a tool for coupling Molecular Dynamics and continuum solvers. It is written in C++ and is meant to support the developers of hybrid molecular - continuum simulations in terms of both realisation of the respective coupling algorithm
Continuum of eLearning: 2012 Project Summary Report
2012-10-01
multimedia, and Continuum of eLearning | Purpose and Vision 19 << UNCLASSIFIED>> (limited) situated learning. Future versions of the CoL self-paced...Continuum of eLearning : 2012 Project Summary Report Continuum of eLearning The Next Evolution of Joint Training on JKO October 2012 Joint...Technical Report November 2011 ā August 2012 Continuum of eLearning : 2012 Project Summary Report N00140-06-D-0060 David T. Fautua, Sae Schatz, Andrea
Elementary Continuum Mechanics for Everyone - and Some More
DEFF Research Database (Denmark)
Byskov, Esben
Quite trivially, Continuum mechanics per se deals with the description of deformations of three-dimensional continua i.e. models whose properties are independent of scale in that the continuum does not possess a structure. Thus, continuum mechanics does not try to model the atomic structure...
Elementary Continuum Mechanics for Everyone - And Some More
DEFF Research Database (Denmark)
Byskov, Esben
Quite trivially, Continuum mechanics per se deals with the description of deformations of three-dimensional continua i.e. models whose properties are independent of scale in that the continuum does not possess a structure. Thus, continuum mechanics does not try to model the atomic structure...
Bacterial Biogeography across the Amazon River-Ocean Continuum
Directory of Open Access Journals (Sweden)
Mary Doherty
2017-05-01
Full Text Available Spatial and temporal patterns in microbial biodiversity across the Amazon river-ocean continuum were investigated along ā¼675 km of the lower Amazon River mainstem, in the TapajĆ³s River tributary, and in the plume and coastal ocean during low and high river discharge using amplicon sequencing of 16S rRNA genes in whole water and size-fractionated samples (0.2ā2.0 Ī¼m and >2.0 Ī¼m. River communities varied among tributaries, but mainstem communities were spatially homogeneous and tracked seasonal changes in river discharge and co-varying factors. Co-occurrence network analysis identified strongly interconnected river assemblages during high (May and low (December discharge periods, and weakly interconnected transitional assemblages in September, suggesting that this system supports two seasonal microbial communities linked to river discharge. In contrast, plume communities showed little seasonal differences and instead varied spatially tracking salinity. However, salinity explained only a small fraction of community variability, and plume communities in blooms of diatom-diazotroph assemblages were strikingly different than those in other high salinity plume samples. This suggests that while salinity physically structures plumes through buoyancy and mixing, the composition of plume-specific communities is controlled by other factors including nutrients, phytoplankton community composition, and dissolved organic matter chemistry. Co-occurrence networks identified interconnected assemblages associated with the highly productive low salinity near-shore region, diatom-diazotroph blooms, and the plume edge region, and weakly interconnected assemblages in high salinity regions. This suggests that the plume supports a transitional community influenced by immigration of ocean bacteria from the plume edge, and by species sorting as these communities adapt to local environmental conditions. Few studies have explored patterns of microbial diversity in
Continuum analogues of contragredient Lie algebras
International Nuclear Information System (INIS)
Saveliev, M.V.; Vershik, A.M.
1989-03-01
We present an axiomatic formulation of a new class of infinite-dimensional Lie algebras - the generalizations of Z-graded Lie algebras with, generally speaking, an infinite-dimensional Cartan subalgebra and a contiguous set of roots. We call such algebras ''continuum Lie algebras''. The simple Lie algebras of constant growth are encapsulated in our formulation. We pay particular attention to the case when the local algebra is parametrized by a commutative algebra while the Cartan operator (the generalization of the Cartan matrix) is a linear operator. Special examples of these algebras are the Kac-Moody algebras, algebras of Poisson brackets, algebras of vector fields on a manifold, current algebras, and algebras with differential or integro-differential Cartan operator. The nonlinear dynamical systems associated with the continuum contragredient Lie algebras are also considered. (author). 9 refs
Mesoscopic and continuum modelling of angiogenesis
Spill, F.
2014-03-11
Angiogenesis is the formation of new blood vessels from pre-existing ones in response to chemical signals secreted by, for example, a wound or a tumour. In this paper, we propose a mesoscopic lattice-based model of angiogenesis, in which processes that include proliferation and cell movement are considered as stochastic events. By studying the dependence of the model on the lattice spacing and the number of cells involved, we are able to derive the deterministic continuum limit of our equations and compare it to similar existing models of angiogenesis. We further identify conditions under which the use of continuum models is justified, and others for which stochastic or discrete effects dominate. We also compare different stochastic models for the movement of endothelial tip cells which have the same macroscopic, deterministic behaviour, but lead to markedly different behaviour in terms of production of new vessel cells. Ā© 2014 Springer-Verlag Berlin Heidelberg.
Mesoscopic and continuum modelling of angiogenesis
Spill, F.; Guerrero, P.; Alarcon, T.; Maini, P. K.; Byrne, H. M.
2014-01-01
Angiogenesis is the formation of new blood vessels from pre-existing ones in response to chemical signals secreted by, for example, a wound or a tumour. In this paper, we propose a mesoscopic lattice-based model of angiogenesis, in which processes that include proliferation and cell movement are considered as stochastic events. By studying the dependence of the model on the lattice spacing and the number of cells involved, we are able to derive the deterministic continuum limit of our equations and compare it to similar existing models of angiogenesis. We further identify conditions under which the use of continuum models is justified, and others for which stochastic or discrete effects dominate. We also compare different stochastic models for the movement of endothelial tip cells which have the same macroscopic, deterministic behaviour, but lead to markedly different behaviour in terms of production of new vessel cells. Ā© 2014 Springer-Verlag Berlin Heidelberg.
Nonlinear continuum mechanics and large inelastic deformations
Dimitrienko, Yuriy I
2010-01-01
This book provides a rigorous axiomatic approach to continuum mechanics under large deformation. In addition to the classical nonlinear continuum mechanics - kinematics, fundamental laws, the theory of functions having jump discontinuities across singular surfaces, etc. - the book presents the theory of co-rotational derivatives, dynamic deformation compatibility equations, and the principles of material indifference and symmetry, all in systematized form. The focus of the book is a new approach to the formulation of the constitutive equations for elastic and inelastic continua under large deformation. This new approach is based on using energetic and quasi-energetic couples of stress and deformation tensors. This approach leads to a unified treatment of large, anisotropic elastic, viscoelastic, and plastic deformations. The author analyses classical problems, including some involving nonlinear wave propagation, using different models for continua under large deformation, and shows how different models lead t...
Sensitivity filtering from a continuum mechanics perspective
DEFF Research Database (Denmark)
Sigmund, Ole; Maute, Kurt
2012-01-01
In topology optimization filtering is a popular approach for preventing numerical instabilities. This short note shows that the well-known sensitivity filtering technique, that prevents checkerboards and ensures mesh-independent designs in density-based topology optimization, is equivalent to min...... to minimizing compliance for nonlocal elasticity problems known from continuum mechanics. Hence, the note resolves the long-standing quest for finding an explanation and physical motivation for the sensitivity filter....
Continuum mechanics the birthplace of mathematical models
Allen, Myron B
2015-01-01
Continuum mechanics is a standard course in many graduate programs in engineering and applied mathematics as it provides the foundations for the various differential equations and mathematical models that are encountered in fluid mechanics, solid mechanics, and heat transfer.Ā This book successfully makes the topic more accessible to advanced undergraduate mathematics majors by aligning the mathematical notation and language with related courses in multivariable calculus, linear algebra, and differential equations; making connections with other areas of applied mathematics where parial differe
International Nuclear Information System (INIS)
Cornwall, J.M.
1986-01-01
The nonperturbative aspects of continuum QCD are so complex that one can only hope to approach them through well-motivated models. The author reviews the general properties that any such model must have, based on the understanding of the gluon condensate in the QCD vacuum. A specific, practical model is proposed motivated by a picture of the condensate as made of thick vortex sheets self-consistently constructed from dynamically massive gluons. (author)
New examples of continuum graded Lie algebras
International Nuclear Information System (INIS)
Savel'ev, M.V.
1989-01-01
Several new examples of continuum graded Lie algebras which provide an additional elucidation of these algebras are given. Here, in particular, the Kac-Moody algebras, the algebra S 0 Diff T 2 of infinitesimal area-preserving diffeomorphisms of the torus T 2 , the Fairlie, Fletcher and Zachos sine-algebras, etc., are described as special cases of the cross product Lie algebras. 8 refs
Identifying health disparities across the tobacco continuum.
Fagan, Pebbles; Moolchan, Eric T; Lawrence, Deirdre; Fernander, Anita; Ponder, Paris K
2007-10-01
Few frameworks have addressed work-force diversity, inequities and inequalities as part of a comprehensive approach to eliminating tobacco-related health disparities. This paper summarizes the literature and describes the known disparities that exist along the tobacco disease continuum for minority racial and ethnic groups, those living in poverty, those with low education and blue-collar and service workers. The paper also discusses how work-force diversity, inequities in research practice and knowledge allocation and inequalities in access to and quality of health care are fundamental to addressing disparities in health. We examined the available scientific literature and existing public health reports to identify disparities across the tobacco disease continuum by minority racial/ethnic group, poverty status, education level and occupation. Results indicate that differences in risk indicators along the tobacco disease continuum do not explain fully tobacco-related cancer consequences among some minority racial/ethnic groups, particularly among the aggregate groups, blacks/African Americans and American Indians/Alaska Natives. The lack of within-race/ethnic group data and its interactions with socio-economic factors across the life-span contribute to the inconsistency we observe in the disease causal paradigm. More comprehensive models are needed to understand the relationships among disparities, social context, diversity, inequalities and inequities. A systematic approach will also help researchers, practitioners, advocates and policy makers determine critical points for interventions, the types of studies and programs needed and integrative approaches needed to eliminate tobacco-related disparities.
Continuum regularized Yang-Mills theory
International Nuclear Information System (INIS)
Sadun, L.A.
1987-01-01
Using the machinery of stochastic quantization, Z. Bern, M. B. Halpern, C. Taubes and I recently proposed a continuum regularization technique for quantum field theory. This regularization may be implemented by applying a regulator to either the (d + 1)-dimensional Parisi-Wu Langevin equation or, equivalently, to the d-dimensional second order Schwinger-Dyson (SD) equations. This technique is non-perturbative, respects all gauge and Lorentz symmetries, and is consistent with a ghost-free gauge fixing (Zwanziger's). This thesis is a detailed study of this regulator, and of regularized Yang-Mills theory, using both perturbative and non-perturbative techniques. The perturbative analysis comes first. The mechanism of stochastic quantization is reviewed, and a perturbative expansion based on second-order SD equations is developed. A diagrammatic method (SD diagrams) for evaluating terms of this expansion is developed. We apply the continuum regulator to a scalar field theory. Using SD diagrams, we show that all Green functions can be rendered finite to all orders in perturbation theory. Even non-renormalizable theories can be regularized. The continuum regulator is then applied to Yang-Mills theory, in conjunction with Zwanziger's gauge fixing. A perturbative expansion of the regulator is incorporated into the diagrammatic method. It is hoped that the techniques discussed in this thesis will contribute to the construction of a renormalized Yang-Mills theory is 3 and 4 dimensions
Integral equation hierarchy for continuum percolation
International Nuclear Information System (INIS)
Given, J.A.
1988-01-01
In this thesis a projection operator technique is presented that yields hierarchies of integral equations satisfied exactly by the n-point connectedness functions in a continuum version of the site-bond percolation problem. The n-point connectedness functions carry the same structural information for a percolation problem as then-point correlation functions do for a thermal problem. This method extends the Potts model mapping of Fortuin and Kastelyn to the continuum by exploiting an s-state generalization of the Widom-Rowlinson model, a continuum model for phase separation. The projection operator technique is used to produce an integral equation hierarchy for percolation similar to the Born-Green heirarchy. The Kirkwood superposition approximation (SA) is extended to percolation in order to close this hierarchy and yield a nonlinear integral equation for the two-point connectedness function. The fact that this function, in the SA, is the analytic continuation to negative density of the two-point correlation function in a corresponding thermal problem is discussed. The BGY equation for percolation is solved numerically, both by an expansion in powers of the density, and by an iterative technique due to Kirkwood. It is argued both analytically and numerically, that the BYG equation for percolation, unlike its thermal counterpart, shows non-classical critical behavior, with Ī· = 1 and Ī³ = 0.05 Ā± .1. Finally a sequence of refinements to the superposition approximations based in the theory of fluids by Rice and Lekner is discussed
Comet Halley: An optical continuum study
International Nuclear Information System (INIS)
Hoban, S.M.
1989-01-01
From an analysis of narrowband CCD images of Comet Halley from 1986 January, March, and April, certain dust structures which are redder than the remainder of the dust coma have become apparent. Mie calculations suggest that this reddening is due to an enhancement of particles with sizes comparable to the observing wavelengths. Although the mass range derived from the calculations presented here is somewhat uncertain as a result of the limitations of Mie theory, these values are in the expected range derived from the calculations presented here is somewhat uncertain as a result of particle sizes which would be both sensitive to radiation pressure and significantly reddened with respect to the solar spectrum at the observing wavelengths. Thus, the red envelopes are plausibly the result of size sorting by solar radiation pressure. The red jets observed on 1986 January 10, March 1 and March 9 can then be explained by the enhanced dust flux at the jet sources, and the subsequent trapping of a relative excess of intermediate mass (i.e. red) particles into the jets which are visible in the continuum images. Analysis of narrowband photometry of the optical continuum of Comet Halley reveals no correlation between the color of the dust and heliocentric distance, phase angle, strength of the continuum or gas-to-dust ratio. The photometric data are thus consistent with a post-ejection sorting mechanism. Chemical inhomogeneities of the nucleus are therefore not necessary to explain the observed structure in the color of the dust in Comet Halley
Lyman continuum observations of solar flares
Machado, M. E.; Noyes, R. W.
1978-01-01
A study is made of Lyman continuum observations of solar flares, using data obtained by the EUV spectroheliometer on the Apollo Telescope Mount. It is found that there are two main types of flare regions: an overall 'mean' flare coincident with the H-alpha flare region, and transient Lyman continuum kernels which can be identified with the H-alpha and X-ray kernels observed by other authors. It is found that the ground level hydrogen population in flares is closer to LTE than in the quiet sun and active regions, and that the level of Lyman continuum formation is lowered in the atmosphere from a mass column density .000005 g/sq cm in the quiet sun to .0003 g/sq cm in the mean flare, and to .001 g/sq cm in kernels. From these results the amount of chromospheric material 'evaporated' into the high temperature region is derived, which is found to be approximately 10 to the 15th g, in agreement with observations of X-ray emission measures.
Tuffen, H.; McGowan, E.; Castro, J. M.; Berlo, K.; James, M. R.; Owen, J.; Schipper, C. I.; Wadsworth, F. B.; Saubin, E.; Wehbe, K.
2014-12-01
The recent rhyolitic eruptions at ChaitĆ©n and CordĆ³n Caulle have provided valuable new insights into the relationship between explosive and effusive activity, and the gas escape mechanisms that permit rapid effusion of degassed lava[1,2]. Bombs ejected during mixed explosive-effusive activity host spectacular tuffisite veins cutting both dense obsidian (Fig 1a) and highly-expanded pumice. Tuffisite veins are ash-filled fracture networks that act as ephemeral permeable pathways for gas escape in shallow conduits and lava domes. Previous studies have revealed water depletion adjacent to tuffisite veins, leading to models of fracture-triggered pressure release[2] and estimates of gas escape timescales[2,3]. We have characterised water diffusion profiles from a new suite of tuffisite-bearing ChaitĆ©n bombs, using synchrotron-source FTIR at the Diamond Light Source, Oxford, UK. Unexpectedly, one exceptionally large tuffisite vein, which is 30 mm thick (Fig. 1a, b) is mantled by zones of strong water enrichment, which enclose the usual narrow depletion zones immediately adjacent to the vein (Fig. 1c). Consistent results from different branches of this vein (Fig. 1b) indicate a similar history. The plausible range of diffusion model solutions points towards ~2-4 hours of vein pressurisation, followed by a brief pre-quench period of lower pressure conditions. In our model the vein opened during a period of overpressure at the lava dome base, sustained by gas influx from a deeper catchment extending hundreds of metres into the upper conduit. Overpressure culminated in violent bomb ejection, after which vein pressure decreased due to gas leakage to the atmosphere through the incompletely welded vein, as observed in rhyolitic bombs from CordĆ³n Caulle (Fig. 1d). Commonly-seen water depletion zones[2,3] may therefore merely record post-fragmentation degassing. However, the enrichment zone points towards the type of deep pressurisation associated with cycles of tilt and
Czech Academy of Sciences Publication Activity Database
KovĆ”Ä, Daniel; NavrĆ”til, M.; MalenovskĆ½, Z.; Å troch, Michal; Å punda, VladimĆr; Urban, Otmar
2012-01-01
RoÄ. 39, Ä. 12 (2012), s. 987-998 ISSN 1445-4408 R&D Projects: GA MÅ k(CZ) ED1.1.00/02.0073; GA MÅ½P(CZ) SP/2D1/70/08 Institutional support: RVO:67179843 Keywords : diurnal course * growth chambers * photosynthetic pigments composition * Picea abies * reflectance continuum removal * xanthophyll cycle Subject RIV: EH - Ecology, Behaviour Impact factor: 2.471, year: 2012
Sheth, Hetu C.; Pande, Kanchan
2014-04-01
Post-K-Pg Boundary Deccan magmatism is well known from the Mumbai area in the Panvel flexure zone. Represented by the Salsette Subgroup, it shows characters atypical of much of the Deccan Traps, including rhyolite lavas and tuffs, mafic tuffs and breccias, spilitic pillow basalts, and "intertrappean" sedimentary or volcanosedimentary deposits, with mafic intrusions as well as trachyte intrusions containing basaltic enclaves. The intertrappean deposits have been interpreted as formed in shallow marine or lagoonal environments in small fault-bounded basins due to syn-volcanic subsidence. We report a previously unknown sedimentary deposit underlying the Dongri rhyolite flow from the upper part of the Salsette Subgroup, with a westerly tectonic dip due to the Panvel flexure. We have obtained concordant 40Ar/39Ar ages of 62.6 Ā± 0.6 Ma (2Ļ) and 62.9 Ā± 0.2 Ma (2Ļ) for samples taken from two separate outcrops of this rhyolite. The results are significant in showing that (i) Danian inter-volcanic sedimentary deposits formed throughout Mumbai, (ii) the rock units are consistent with the stratigraphy postulated earlier for Mumbai, (iii) shale fragments known in some Dongri tuffs were likely derived from the sedimentary deposit under the Dongri rhyolite, (iv) the total duration of extrusive and intrusive Deccan magmatism was at least 8-9 million years, and (v) Panvel flexure formed, or continued to form, after 63 Ma, possibly even 62 Ma, and could not have formed by 65-64 Ma as concluded in a recent study.
Non-classical continuum mechanics a dictionary
Maugin, GĆ©rard A
2017-01-01
This dictionary offers clear and reliable explanations of over 100 keywords covering the entire field of non-classical continuum mechanics and generalized mechanics, including the theory of elasticity, heat conduction, thermodynamic and electromagnetic continua, as well as applied mathematics. Every entry includes the historical background and the underlying theory, basic equations and typical applications. The reference list for each entry provides a link to the original articles and the most important in-depth theoretical works. Last but not least, every entry is followed by a cross-reference to other related subject entries in the dictionary.
Effect of couplings in the resonance continuum
International Nuclear Information System (INIS)
Royal, J; Larson, A; Orel, A E
2004-01-01
Electronic coupling of two or more resonances via the electron scattering continuum is investigated. The effect of this coupling as a function of the resonance curves and autoionization widths is investigated, and the conditions for the maximum effect are determined. The theory is applied to two physical problems, the product state distribution produced by the dissociative recombination of electrons with HeH + and a one-dimensional model for ion-pair production resulting from electron collisions with H + 3 . It is found that the coupling does not affect the product state distribution in HeH + but produces a significant effect in the H + 3 model
Discrete expansions of continuum functions. General concepts
International Nuclear Information System (INIS)
Bang, J.; Ershov, S.N.; Gareev, F.A.; Kazacha, G.S.
1979-01-01
Different discrete expansions of the continuum wave functions are considered: pole expansion (according to the Mittag-Lefler theorem), Weinberg states. The general property of these groups of states is their completeness in the finite region of space. They satisfy the Schroedinger type equations and are matched with free solutions of the Schroedinger equation at the boundary. Convergence of expansions for the S matrix, the Green functions and the continuous-spectrum wave functions is studied. A new group of states possessing the best convergence is introduced
Histidine in Continuum Electrostatics Protonation State Calculations
Couch, Vernon; Stuchebruckhov, Alexei
2014-01-01
A modification to the standard continuum electrostatics approach to calculate protein pKas which allows for the decoupling of histidine tautomers within a two state model is presented. Histidine with four intrinsically coupled protonation states cannot be easily incorporated into a two state formalism because the interaction between the two protonatable sites of the imidazole ring is not purely electrostatic. The presented treatment, based on a single approximation of the interrelation between histidineās charge states, allows for a natural separation of the two protonatable sites associated with the imidazole ring as well as the inclusion of all protonation states within the calculation. PMID:22072521
Set theory and the continuum hypothesis
Cohen, Paul J
2008-01-01
This exploration of a notorious mathematical problem is the work of the man who discovered the solution. The independence of the continuum hypothesis is the focus of this study by Paul J. Cohen. It presents not only an accessible technical explanation of the author's landmark proof but also a fine introduction to mathematical logic. An emeritus professor of mathematics at Stanford University, Dr. Cohen won two of the most prestigious awards in mathematics: in 1964, he was awarded the American Mathematical Society's BĆ“cher Prize for analysis; and in 1966, he received the Fields Medal for Logic.
On nonlocal modeling in continuum mechanics
Directory of Open Access Journals (Sweden)
Adam Martowicz
2018-01-01
Full Text Available The objective of the paper is to provide an overview of nonlocal formulations for models of elastic solids. The author presents the physical foundations for nonlocal theories of continuum mechanics, followed by various analytical and numerical techniques. The characteristics and range of practical applications for the presented approaches are discussed. The results of numerical simulations for the selected case studies are provided to demonstrate the properties of the described methods. The paper is illustrated with outcomes from peridynamic analyses. Fatigue and axial stretching were simulated to show the capabilities of the developed numerical tools.
Continuum modeling an approach through practical examples
Muntean, Adrian
2015-01-01
This book develops continuum modeling skills and approaches the topic from three sides: (1) derivation of global integral laws together with the associated local differential equations, (2) design of constitutive laws and (3) modeling boundary processes. The focus of this presentation lies on many practical examples covering aspects such as coupled flow, diffusion and reaction in porous media or microwave heating of a pizza, as well as traffic issues in bacterial colonies and energy harvesting from geothermal wells. The target audience comprises primarily graduate students in pure and applied mathematics as well as working practitioners in engineering who are faced by nonstandard rheological topics like those typically arising in the food industry.
Quasi-bound states in continuum
International Nuclear Information System (INIS)
Nakamura, Hiroaki; Hatano, Naomichi; Garmon, Sterling; Petrosky, Tomio
2007-08-01
We report the prediction of quasi-bound states (resonant states with very long lifetimes) that occur in the eigenvalue continuum of propagating states for a wide region of parameter space. These quasi-bound states are generated in a quantum wire with two channels and an adatom, when the energy bands of the two channels overlap. A would-be bound state that lays just below the upper energy band is slightly destabilized by the lower energy band and thereby becomes a resonant state with a very long lifetime (a second QBIC lays above the lower energy band). (author)
Energy Technology Data Exchange (ETDEWEB)
Self, S.; Sykes, M.L. [Hawaii Univ., Honolulu, HI (United States). Dept. of Geology and Geophysics; Wolff, J.A. [Texas Univ., Arlington, TX (United States). Dept. of Geology; Skuba, C.E. [McMaster Univ., Hamilton, ON (Canada). Dept. of Geology
1991-09-01
This report is a summary of work supported by DOE grant No. DE-FGO5-87ER13795 that was completed or is still in progress. The stated purpose of this grant was to collect geochemical information (trace element, radiogenic isotope and stable oxygen and hydrogen isotope) on samples from core holes VC-I and VC-2a in the Valles caldera in order to establish a consistent detailed intracaldera stratigraphy and relate this to extracaldera volcanic rock units of the Jemez Mountains. Careful stratigraphic control of the intracaldera units is necessary to evaluate models of caldera formation, ignimbrite deposition, and resurgence. Combined stable and radiogenic isotope and trace element data will also provide major insights to petrogenesis of the Bandelier magma system. The composition of non-hydrothermally altered samples from outflow units of the Bandelier Tuff and related volcanics must be known to assess isotopic variations of intracaldera ignimbrite samples. On detailed examination of the VC-2a core samples, it became apparent that hydrothermal alteration is so extensive that no geochemical information useful for stratigraphic fingerprinting or petrogenesis could be obtained, and that correlation with other intracaldera units and extracaldera units must be made on the basis of stratigraphic position and gross lithologic characteristics. Accordingly, we emphasize geochemical data from the extracaldera Bandelier Tuffs and related units which will be useful for comparison with proposed drill hole VC-4 and for any future studies of the region. The stable isotope, radiogenic isotope and trace element data obtained from this project, combined with existing major and trace element data for volcanic rocks from this area, provide an extensive data base essential to future Continental Scientific Drilling Program projects in the Jemez Mountains of New Mexico.
Multiple Temperature Model for Near Continuum Flows
International Nuclear Information System (INIS)
XU, Kun; Liu, Hongwei; Jiang, Jianzheng
2007-01-01
In the near continuum flow regime, the flow may have different translational temperatures in different directions. It is well known that for increasingly rarefied flow fields, the predictions from continuum formulation, such as the Navier-Stokes equations, lose accuracy. These inaccuracies may be partially due to the single temperature assumption in the Navier-Stokes equations. Here, based on the gas-kinetic Bhatnagar-Gross-Krook (BGK) equation, a multitranslational temperature model is proposed and used in the flow calculations. In order to fix all three translational temperatures, two constraints are additionally proposed to model the energy exchange in different directions. Based on the multiple temperature assumption, the Navier-Stokes relation between the stress and strain is replaced by the temperature relaxation term, and the Navier-Stokes assumption is recovered only in the limiting case when the flow is close to the equilibrium with the same temperature in different directions. In order to validate the current model, both the Couette and Poiseuille flows are studied in the transition flow regime
Continuum robot arms inspired by cephalopods
Walker, Ian D.; Dawson, Darren M.; Flash, Tamar; Grasso, Frank W.; Hanlon, Roger T.; Hochner, Binyamin; Kier, William M.; Pagano, Christopher C.; Rahn, Christopher D.; Zhang, Qiming M.
2005-05-01
In this paper, we describe our recent results in the development of a new class of soft, continuous backbone ("continuum") robot manipulators. Our work is strongly motivated by the dexterous appendages found in cephalopods, particularly the arms and suckers of octopus, and the arms and tentacles of squid. Our ongoing investigation of these animals reveals interesting and unexpected functional aspects of their structure and behavior. The arrangement and dynamic operation of muscles and connective tissue observed in the arms of a variety of octopus species motivate the underlying design approach for our soft manipulators. These artificial manipulators feature biomimetic actuators, including artificial muscles based on both electro-active polymers (EAP) and pneumatic (McKibben) muscles. They feature a "clean" continuous backbone design, redundant degrees of freedom, and exhibit significant compliance that provides novel operational capacities during environmental interaction and object manipulation. The unusual compliance and redundant degrees of freedom provide strong potential for application to delicate tasks in cluttered and/or unstructured environments. Our aim is to endow these compliant robotic mechanisms with the diverse and dexterous grasping behavior observed in octopuses. To this end, we are conducting fundamental research into the manipulation tactics, sensory biology, and neural control of octopuses. This work in turn leads to novel approaches to motion planning and operator interfaces for the robots. The paper describes the above efforts, along with the results of our development of a series of continuum tentacle-like robots, demonstrating the unique abilities of biologically-inspired design.
Continuum deformation of multi-agent systems
Rastgoftar, Hossein
2016-01-01
This monograph presents new algorithms for formation control of multi-agent systems (MAS) based on principles of continuum mechanics. Beginning with an overview of traditional methods, the author then introduces an innovative new approach whereby agents of an MAS are considered as particles in a continuum evolving in ān whose desired configuration is required to satisfy an admissible deformation function. The necessary theory and its validation on a mobile-agent-based swarm test bed are considered for two primary tasks: homogeneous transformation of the MAS and deployment of a random distribution of agents on a desired configuration. The framework for this model is based on homogeneous transformations for the evolution of an MAS under no inter-agent communication, local inter-agent communication, and intelligent perception by agents. Different communication protocols for MAS evolution, the robustness of tracking of a desired motion by an MAS evolving in ān, and the effect of communication delays in an MAS...
Knott, T.; Branney, M. J.; Christiansen, E. H.; Reichow, M. K.; McCurry, M. O.; Shervais, J. W.
2013-12-01
Project HOTSPOT seeks to understand the bimodal volcanism in the Yellowstone-Snake River large igneous province, including the magma generation and eruption history. The 1.9 km-deep Kimberly well in southern Idaho, USA, reveals a proximal mid-Miocene rhyolitic and basaltic volcanic succession marginal to the postulated Twin Falls eruptive centre. Three rhyolitic eruption-units (each we interpret to record a single eruption, based on core descriptions) are separated by basaltic lavas, palaeosols and volcaniclastic sediments, and are being dated by 40Ar-39Ar on plagioclases. Whole-rock and mineral chemical data, from each unit, has been compiled to facilitate correlation with well-studied eruption-units at more distal outcrops, where we have detailed chemical, palaeomagnetic and radiometric characterisation. Results will contribute to frequency and volume calculations for some of the most catastrophic super-eruptions in Earth history. As the volcanism is of Snake River (SR)-type and lacks typical pumice fall deposits and low-moderate grade ignimbrites, interpreting the physical origin of the units can be difficult; many SR-type rheomorphic ignimbrites are flow-banded and resemble lavas, and the distinction between these and true lavas involves interpretation of critical evidence from lower contacts (e.g., distinguishing basal lava autobreccias from peperitic contacts, which can occur at the bases of SR-type lavas and ignimbrites). The lower most eruption-unit, ';Kimberly Rhyolite 1,' is >1323 m thick (base not seen) and suggests ponding in the margin of a caldera. Few vitroclastic textures are preserved, but a rheomorphic ignimbrite origin is inferred by folded fabrics and scattered obsidian chips (2-5 mm in size) within a thick lithoidal zone, which passes sharply upwards into a 39.6 m thick vitrophyre with an autobrecciated top and it is overlain by 18 m (caldera?) lake sediments. However, lithic mesobreccia, that characterise caldera fills elsewhere, are not seen
Continuum capture in the three-body problem
International Nuclear Information System (INIS)
Sellin, I.A.
1980-01-01
The three-body problem, especially the problem of electron capture to the continuum in heavy particle collisions is reviewed. Major topics covered include: second born-induced asymmetry in electron capture to the continuum; historical context, links to other tests of atomic scattering theory; experiments characterizing the velocity distribution of ECC electrons; other atomic physics tests of high velocity Born expansions; atom capture; capture by positrons; and pion capture to the continuum
Wright, Heather M.; Vazquez, Jorge A.; Champion, Duane E.; Calvert, Andrew T.; Mangan, Margaret T.; Stelten, Mark E.; Cooper, Kari M.; Herzig, Charles; Schriener Jr., Alexander
2015-01-01
In the Salton Trough, CA, five rhyolite domes form the Salton Buttes: Mullet Island, Obsidian Butte, Rock Hill, North and South Red Hill, from oldest to youngest. Results presented here includeĀ 40Ar/39Ar anorthoclase ages, 238U-230Th zircon crystallization ages, and comparison of remanent paleomagnetic directions with the secular variation curve, which indicate that all domes are Holocene. 238U-230Th zircon crystallization ages are more precise than but within uncertainty of 40Ar/39Ar anorthoclase ages, suggesting that zircon crystallization proceeded until shortly before eruption in all cases except one. Remanent paleomagnetic directions require three eruption periods: (1) Mullet Island, (2) Obsidian Butte, and (3) Rock Hill, North Red Hill, and South Red Hill. Borehole cuttings logs document up to two shallow tephra layers. North and South Red Hills likely erupted within 100 years of each other, with a combined 238U-230Th zircon isochron age of: 2.83 Ā± 0.60 ka (2 sigma); paleomagnetic evidence suggests this age predates eruption by hundreds of years (1800 cal BP). Rock Hill erupted closely in time to these eruptions. The Obsidian Butte 238U-230Th isochron age (2.86 Ā± 0.96 ka) is nearly identical to the combined Red Hill age, but its Virtual Geomagnetic Pole position suggests a slightly older age. The age of aphyric Mullet Island dome is the least well constrained: zircon crystals are resorbed and the paleomagnetic direction is most distinct; possible Mullet Island ages include ca. 2300, 5900, 6900, and 7700 cal BP. Our results constrain the duration of Salton Buttes volcanism to between ca. 5900 and 500 years.
A continuum theory of edge dislocations
Berdichevsky, V. L.
2017-09-01
Continuum theory of dislocation aims to describe the behavior of large ensembles of dislocations. This task is far from completion, and, most likely, does not have a "universal solution", which is applicable to any dislocation ensemble. In this regards it is important to have guiding lines set by benchmark cases, where the transition from a discrete set of dislocations to a continuum description is made rigorously. Two such cases have been considered recently: equilibrium of dislocation walls and screw dislocations in beams. In this paper one more case is studied, equilibrium of a large set of 2D edge dislocations placed randomly in a 2D bounded region. The major characteristic of interest is energy of dislocation ensemble, because it determines the structure of continuum equations. The homogenized energy functional is obtained for the periodic dislocation ensembles with a random contents of the periodic cell. Parameters of the periodic structure can change slowly on distances of order of the size of periodic cells. The energy functional is obtained by the variational-asymptotic method. Equilibrium positions are local minima of energy. It is confirmed the earlier assertion that energy density of the system is the sum of elastic energy of averaged elastic strains and microstructure energy, which is elastic energy of the neutralized dislocation system, i.e. the dislocation system placed in a constant dislocation density field making the averaged dislocation density zero. The computation of energy is reduced to solution of a variational cell problem. This problem is solved analytically. The solution is used to investigate stability of simple dislocation arrays, i.e. arrays with one dislocation in the periodic cell. The relations obtained yield two outcomes: First, there is a state parameter of the system, dislocation polarization; averaged stresses affect only dislocation polarization and cannot change other characteristics of the system. Second, the structure of
Polymer quantum mechanics and its continuum limit
International Nuclear Information System (INIS)
Corichi, Alejandro; Vukasinac, Tatjana; Zapata, Jose A.
2007-01-01
A rather nonstandard quantum representation of the canonical commutation relations of quantum mechanics systems, known as the polymer representation, has gained some attention in recent years, due to its possible relation with Planck scale physics. In particular, this approach has been followed in a symmetric sector of loop quantum gravity known as loop quantum cosmology. Here we explore different aspects of the relation between the ordinary Schroedinger theory and the polymer description. The paper has two parts. In the first one, we derive the polymer quantum mechanics starting from the ordinary Schroedinger theory and show that the polymer description arises as an appropriate limit. In the second part we consider the continuum limit of this theory, namely, the reverse process in which one starts from the discrete theory and tries to recover back the ordinary Schroedinger quantum mechanics. We consider several examples of interest, including the harmonic oscillator, the free particle, and a simple cosmological model
Constraining Lyman continuum escape using Machine Learning
Giri, Sambit K.; Zackrisson, Erik; Binggeli, Christian; Pelckmans, Kristiaan; Cubo, RubĆ©n; Mellema, Garrelt
2018-05-01
The James Webb Space Telescope (JWST) will observe the rest-frame ultraviolet/optical spectra of galaxies from the epoch of reionization (EoR) in unprecedented detail. While escaping into the intergalactic medium, hydrogen-ionizing (Lyman continuum; LyC) photons from the galaxies will contribute to the bluer end of the UV slope and make nebular emission lines less prominent. We present a method to constrain leakage of the LyC photons using the spectra of high redshift (z >~ 6) galaxies. We simulate JWST/NIRSpec observations of galaxies at z =6-9 by matching the fluxes of galaxies observed in the Frontier Fields observations of galaxy cluster MACS-J0416. Our method predicts the escape fraction fesc with a mean absolute error Īfesc ~ 0.14. The method also predicts the redshifts of the galaxies with an error .
Continuum Mechanics of Beam and Plate Flexure
DEFF Research Database (Denmark)
JĆ¶nsson, Jeppe
This text has been written and used during the spring of 1995 for a course on flexural mechanics of beams and plates at Aalborg University. The idea has been to concentrate on basic principles of the theories, which are of importance to the modern structural engineer. Today's structural engineer...... must be acquainted with the classic beam and plate theories, when reading manuals and using modern software tools such as the finite element method. Each chapter includes supplementary theory and derivations enabling consultation of the notes also at a later stage of study. A preliminary chapter...... introduces the modern notation used in textbooks and in research today. It further gives an introduction to three-dimensional continuum mechanics of elastic bodies and the related principles of virtual work. The ideas to give the students a basic understanding of the stresses and strains, the equilibrium...
Embodiment design of soft continuum robots
Directory of Open Access Journals (Sweden)
Rongjie Kang
2016-04-01
Full Text Available This article presents the results of a multidisciplinary project where mechatronic engineers worked alongside biologists to develop a soft robotic arm that captures key features of octopus anatomy and neurophysiology. The concept of embodiment (the dynamic coupling between sensory-motor control, anatomy, materials and environment that allows for the animal to achieve adaptive behaviours is used as a starting point for the design process but tempered by current engineering technologies and approaches. In this article, the embodied design requirements are first discussed from a robotic viewpoint by taking into account real-life engineering limitations; then, the motor control schemes inspired by octopus nervous system are investigated. Finally, the mechanical and control design of a prototype is presented that appropriately blends bio-inspiration and engineering limitations. Simulated and experimental results show that the developed continuum robotic arm is able to reproduce octopus-like motions for bending, reaching and grasping.
Continuum Reverberation Mapping of AGN Accretion Disks
Energy Technology Data Exchange (ETDEWEB)
Fausnaugh, Michael M. [Department of Astronomy, Ohio State University, Columbus, OH (United States); MIT Kavli Institute for Astrophysics and Space Research, Cambridge, MA (United States); Peterson, Bradley M. [Department of Astronomy, Ohio State University, Columbus, OH (United States); Center for Cosmology and AstroParticle Physics, Ohio State University, Columbus, OH (United States); Space Telescope Science Institute, Baltimore, MD (United States); Starkey, David A. [SUPA Physics and Astronomy, University of St. Andrews, Scotland (United Kingdom); Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL (United States); Horne, Keith, E-mail: faus@mit.edu [SUPA Physics and Astronomy, University of St. Andrews, Scotland (United Kingdom); Collaboration: the AGN STORM Collaboration
2017-12-05
We show recent detections of inter-band continuum lags in three AGN (NGC 5548, NGC 2617, and MCG+08-11-011), which provide new constraints on the temperature profiles and absolute sizes of the accretion disks. We find lags larger than would be predicted for standard geometrically thin, optically thick accretion disks by factors of 2.3ā3.3. For NGC 5548, the data span UV through optical/near-IR wavelengths, and we are able to discern a steeper temperature profile than the T ~ R{sup ā3/4} expected for a standard thin disk. Using a physical model, we are also able to estimate the inclinations of the disks for two objects. These results are similar to those found from gravitational microlensing of strongly lensed quasars, and provide a complementary approach for investigating the accretion disk structure in local, low luminosity AGN.
Variational continuum multiphase poroelasticity theory and applications
Serpieri, Roberto
2017-01-01
This book collects the theoretical derivation of a recently presented general variational macroscopic continuum theory of multiphase poroelasticity (VMTPM), together with its applications to consolidation and stress partitioning problems of interest in several applicative engineering contexts, such as in geomechanics and biomechanics. The theory is derived based on a purely-variational deduction, rooted in the least-Action principle, by considering a minimal set of kinematic descriptors. The treatment herein considered keeps a specific focus on the derivation of most general medium-independent governing equations. It is shown that VMTPM recovers paradigms of consolidated use in multiphase poroelasticity such as Terzaghi's stress partitioning principle and Biot's equations for wave propagation. In particular, the variational treatment permits the derivation of a general medium-independent stress partitioning law, and the proposed variational theory predicts that the external stress, the fluid pressure, and the...
A Threshold Continuum for Aeolian Sand Transport
Swann, C.; Ewing, R. C.; Sherman, D. J.
2015-12-01
The threshold of motion for aeolian sand transport marks the initial entrainment of sand particles by the force of the wind. This is typically defined and modeled as a singular wind speed for a given grain size and is based on field and laboratory experimental data. However, the definition of threshold varies significantly between these empirical models, largely because the definition is based on visual-observations of initial grain movement. For example, in his seminal experiments, Bagnold defined threshold of motion when he observed that 100% of the bed was in motion. Others have used 50% and lesser values. Differences in threshold models, in turn, result is large errors in predicting the fluxes associated with sand and dust transport. Here we use a wind tunnel and novel sediment trap to capture the fractions of sand in creep, reptation and saltation at Earth and Mars pressures and show that the threshold of motion for aeolian sand transport is best defined as a continuum in which grains progress through stages defined by the proportion of grains in creep and saltation. We propose the use of scale dependent thresholds modeled by distinct probability distribution functions that differentiate the threshold based on micro to macro scale applications. For example, a geologic timescale application corresponds to a threshold when 100% of the bed in motion whereas a sub-second application corresponds to a threshold when a single particle is set in motion. We provide quantitative measurements (number and mode of particle movement) corresponding to visual observations, percent of bed in motion and degrees of transport intermittency for Earth and Mars. Understanding transport as a continuum provides a basis for revaluating sand transport thresholds on Earth, Mars and Titan.
Continuum shell-model with complicated configurations
International Nuclear Information System (INIS)
Barz, H.W.; Hoehn, J.
1977-05-01
The traditional shell model has been combined with the coupled channels method in order to describe resonance reactions. For that purpose the configuration space is divided into two subspaces (Feshbach projection method). Complicated shell-model configurations can be included into the subspace of discrete states which contains the single particle resonance states too. In the subspace of scattering states the equation of motion is solved by using the coupled channels method. Thereby the orthogonality between scattering states and discrete states is ensured. Resonance states are defined with outgoing waves in all channels. By means of simple model calculations the special role of the continuum is investigated. In this connection the energy dependence of the resonance parameters, the isospin mixture via the continuum, threshold effect, as well as the influence of the number of channels taken into account on the widths, positions and dipole strengths of the resonance are discussed. The model is mainly applied to the description of giant resonances excited by the scattering of nucleons and photo-nucleus processes (source term method) found in reactions on light nuclei. The giant resonance observed in the 15 N(p,n) reaction is explained by the inclusion of 2p-2h states. The same is true for the giant resonance in 13 C(J = 1/2, 3/2) as well as for the giant resonance built on the first 3 - state in 16 O. By means of a correlation analysis for the reduced widths amplitudes an access to the doorway conception is found. (author)
Continuum Damage Mechanics A Continuum Mechanics Approach to the Analysis of Damage and Fracture
Murakami, Sumio
2012-01-01
Recent developments in engineering and technology have brought about serious and enlarged demands for reliability, safety and economy in wide range of fields such as aeronautics, nuclear engineering, civil and structural engineering, automotive and production industry. Ā This, in turn, has caused more interest in continuum damage mechanics and its engineering applications. Ā This book aims to give a concise overview of the current state of damage mechanics, and then to show the fascinating possibility of this promising branch of mechanics, and to provide researchers, engineers and graduate students with anĀ intelligible and self-contained textbook. Ā The book consists of two parts and an appendix.Ā Part I Ā is concerned with the foundation of continuum damage mechanics. Ā Basic concepts of material damage and the mechanical representation of damage state of various kinds are described in Chapters 1 and 2.Ā In Chapters 3-5, irreversible thermodynamics, thermodynamic constitutive theory and its application ...
Teaching Continuum Mechanics in a Mechanical Engineering Program
Liu, Yucheng
2011-01-01
This paper introduces a graduate course, continuum mechanics, which is designed for and taught to graduate students in a Mechanical Engineering (ME) program. The significance of continuum mechanics in engineering education is demonstrated and the course structure is described. Methods used in teaching this course such as topics, classā¦
Stonefly (Plecoptera) Feeding Modes: Variation Along a California River Continuum
Richard L. Bottorff; Allen W. Knight
1989-01-01
The distribution of Plecoptera along a California river was used to test several predictions of the River Continuum Concept about how functional feeding groups should change along a stream's length. Stoneflies were collected from stream orders 1-6 (123 km) of the Cosumnes River continuum in the central Sierra Nevada. The 69 stonefly species collected were...
Continuum Thinking and the Contexts of Personal Information Management
Huvila, Isto; Eriksen, Jon; HĆ¤usner, Eva-Maria; Jansson, Ina-Maria
2014-01-01
Introduction: Recent personal information management literature has underlined the significance of the contextuality of personal information and its use. The present article discusses the applicability of the records continuum model and its generalisation, continuum thinking, as a theoretical framework for explicating the overlap and evolution ofā¦
Bursts and shocks in a continuum shell model
DEFF Research Database (Denmark)
Andersen, Ken Haste; Bohr, Tomas; Jensen, M.H.
1998-01-01
We study a burst event, i.e., the evolution of an initial condition having support only in a finite interval of k-space, in the continuum shell model due to Parisi. We show that the continuum equation without forcing or dissipation can be explicitly written in characteristic form and that the right...
Points-Based Safe Path Planning of Continuum Robots
Directory of Open Access Journals (Sweden)
Khuram Shahzad
2015-07-01
Full Text Available Continuum robots exhibit great potential in a number of challenging applications where traditional rigid link robots pose certain limitations, e.g., working in unstructured environments. In order to enable the usage of continuum robots in safety-critical applications, such as surgery and nuclear decontamination, it is extremely important to ensure a safe path for the robot's movement. Existing algorithms for continuum robot path planning have certain limitations that need to be addressed. These include the fact that none of the algorithms provide safety assurance parameters and control for path planning. They are computationally expensive, applicable to a specific type of continuum robots, and mostly they do not incorporate design and kinematics constraints. In this paper, we propose a points-based path planning (PoPP algorithm for continuum robots that computes the path by imposing safety constraints and improves upon the limitations of existing approaches. In the algorithm, we exploit the constant curvature-bending property of continuum robots in their path planning process. The algorithm is computationally efficient and provides a good tradeoff between accuracy and efficiency that can be implemented to enable the safety-critical application of continuum robots. This algorithm also provides information regarding path volume and flexibility in movement. Simulation results confirm that the algorithm possesses promising potential for all types of continuum robots (following the constant curvature-bending property. We believe that this effectively balances the desired safety and efficiency requirements.
A Behavioral Continuum: A Look at Personality Disorders.
Harris, George; Kirk, Nancy A.
1985-01-01
Suggests that narcissistic, borderline, and antisocial personality disorders are not discrete diagnostic categories, but that they lie along a continuum and have in common the dimensions of degree of self-centeredness and degree of differentiation. Presents evidence supporting existence of continuum of behavior rather than discrete diagnosticā¦
Continuum of Counseling Goals: A Framework for Differentiating Counseling Strategies.
Bruce, Paul
1984-01-01
Presents counseling goals in a developmental continuum similar in concept to Maslow's hierarchy of needs. Discusses ego development goals, socialization goals, developmental goals, self-esteem goals, and self-realization goals and describes characteristics and implications of the continuum. (JAC)
The Infrared Continuum Spectrum of VY Canis Majoris
Harwit, Martin; Malfait, Koen; Decin, Leen; Waelkens, Christoffel; Feuchtgruber, Helmut; Melnick, Gary J.
2001-08-01
We combine spectra of VY CMa obtained with the short- and long-wavelength spectrometers, SWS and LWS, on the Infrared Space Observatory3 to provide a first detailed continuum spectrum of this highly luminous star. The circumstellar dust cloud through which the star is observed is partially self-absorbing, which makes for complex computational modeling. We review previous work and comment on the range of uncertainties about the physical traits and mineralogical composition of the modeled disk. We show that these uncertainties significantly affect the modeling of the outflow and the estimated mass loss. In particular, we demonstrate that a variety of quite diverse models can produce good fits to the observed spectrum. If the outflow is steady, and the radiative repulsion on the dust cloud dominates the star's gravitational attraction, we show that the total dust mass loss rate is ~4Ć10-6 Msolar yr-1, assuming that the star is at a distance of 1.5 kpc. Several indications, however, suggest that the outflow from the star may be spasmodic. We discuss this and other problems facing the construction of a physically coherent model of the dust cloud and a realistic mass-loss analysis.
International Nuclear Information System (INIS)
Abdelouas, A.
1996-06-01
Alteration experiments with the R7T7 glass in three salt brines, saturated respectively in MgCl 2 , MgCl 2 -CaCl 2 and NaCl, showed that the solubilities of most radionuclides are controlled by the secondary phases. Nd, La, and Pr are trapped in powellite, Ce in cerianite, U in coffinite, and Sr is partially immobilized in barite. There is a good similarity between the secondary phases formed experimentally on volcanic glasses and the R7T7 glass altered in MgCl 2 CaCl 2 -saturated brine (formation of hydrotalcite and chlorite-serpentine at short-term and saponite at long-term). These results support the use of volcanic glasses alteration patterns in Mg-rich solutions (seawater, brines) to understand the long-term behavior of nuclear waste glasses and to evaluate the stability of the secondary phases. The study of the sediments of Uyuni (Bolivia) showed that the corrosion rate of the rhyolitic glass in brines at 10 C is 12 to 30 time lower than those of rhyolitic glasses altered in high dilute conditions. The neoformed phases in the sediments are: Smectite, alunite, pyrite, barite, celestite and cerianite. The low alteration rate of rhyolitic glasses in brines and the formation of secondary phases such as smectite, barite and cerianite (also formed during the experimental alteration of the R7T7 glass), permit us to expect the low alteration of nuclear waste glasses at long-term in brines and the trapping of certain radionuclides in secondary phases. (orig.) [de
Steigerwald, Celia H.; Mutschler, Felix E.; Ludington, Steve
1983-01-01
GRANNY is a data bank containing information on 507 chemically analyzed Laramide or younger high-silica rhyolites and granites from Colorado and north-central New Mexico. The data were compiled from both published and unpublished sources. The data bank is designed to aid in the recognition of igneous rocks with a high exploration potential for the discovery of molybdenum (and other lithophile element) deposits. Information on source reference, geographic location, age, mineralogic and petrologic characteristics, major constituent analyses, and trace element analyses for each sample are given. The data bank is available in two formats: 1) paper- or microfiche-hardcopy, and 2) fixed format computer readable magnetic tape.
Kollen, Boudewijn J.; Groenier, Klaas H.; Berendsen, Annette J.
Objective: Communication between professionals is essential because it contributes to an optimal continuum of care. Whether patients experience adequate continuum of care is uncertain. To address this, a questionnaire was developed to elucidate this care process from a patients' perspective. In this
Optical continuum generation on a silicon chip
Jalali, Bahram; Boyraz, Ozdal; Koonath, Prakash; Raghunathan, Varun; Indukuri, Tejaswi; Dimitropoulos, Dimitri
2005-08-01
Although the Raman effect is nearly two orders of magnitude stronger than the electronic Kerr nonlinearity in silicon, under pulsed operation regime where the pulse width is shorter than the phonon response time, Raman effect is suppressed and Kerr nonlinearity dominates. Continuum generation, made possible by the non-resonant Kerr nonlinearity, offers a technologically and economically appealing path to WDM communication at the inter-chip or intra-chip levels. We have studied this phenomenon experimentally and theoretically. Experimentally, a 2 fold spectral broadening is obtained by launching ~4ps optical pulses with 2.2GW/cm2 peak power into a conventional silicon waveguide. Theoretical calculations, that include the effect of two-photon-absorption, free carrier absorption and refractive index change indicate that up to >30 times spectral broadening is achievable in an optimized device. The broadening is due to self phase modulation and saturates due to two photon absorption. Additionally, we find that free carrier dynamics also contributes to the spectral broadening and cause the overall spectrum to be asymmetric with respect to the pump wavelength.
Diagnostic Reasoning across the Medical Education Continuum
Directory of Open Access Journals (Sweden)
C. Scott Smith
2014-07-01
Full Text Available We aimed to study linguistic and non-linguistic elements of diagnostic reasoning across the continuum of medical education. We performed semi-structured interviews of premedical students, first year medical students, third year medical students, second year internal medicine residents, and experienced faculty (ten each as they diagnosed three common causes of dyspnea. A second observer recorded emotional tone. All interviews were digitally recorded and blinded transcripts were created. Propositional analysis and concept mapping were performed. Grounded theory was used to identify salient categories and transcripts were scored with these categories. Transcripts were then unblinded. Systematic differences in propositional structure, number of concept connections, distribution of grounded theory categories, episodic and semantic memories, and emotional tone were identified. Summary concept maps were created and grounded theory concepts were explored for each learning level. We identified three major findings: (1 The āapprentice effectā in novices (high stress and low narrative competence; (2 logistic concept growth in intermediates; and (3 a cognitive state transition (between analytical and intuitive approaches in experts. These findings warrant further study and comparison.
Identity of Particles and Continuum Hypothesis
Berezin, Alexander A.
2001-04-01
Why all electrons are the same? Unlike other objects, particles and atoms (same isotopes) are forbidden to have individuality or personal history (or reveal their hidden variables, even if they do have them). Or at least, what we commonly call physics so far was unable to disprove particle's sameness (Berezin and Nakhmanson, Physics Essays, 1990). Consider two opposing hypotheses: (A) particles are indeed absolutely same, or (B) they do have individuality, but it is beyond our capacity to demonstrate. This dilemma sounds akin to undecidability of Continuum Hypothesis of existence (or not) of intermediate cardinalities between integers and reals (P.Cohen). Both yes and no of it are true. Thus, (alleged) sameness of electrons and atoms may be a physical translation (embodiment) of this fundamental Goedelian undecidability. Experiments unlikely to help: even if we find that all electrons are same within 30 decimal digits, could their masses (or charges) still differ in100-th digit? Within (B) personalized informationally rich (infinitely rich?) digital tails (starting at, say, 100-th decimal) may carry individual record of each particle history. Within (A) parameters (m, q) are indeed exactly same in all digits and their sameness is based on some inherent (meta)physical principle akin to Platonism or Eddington-type numerology.
Continuum Thermodynamics - Part II: Applications and Examples
Albers, Bettina; Wilmanski, Krzysztof
The intention by writing Part II of the book on continuum thermodynamics was the deepening of some issues covered in Part I as well as a development of certain skills in dealing with practical problems of oscopic processes. However, the main motivation for this part is the presentation of main facets of thermodynamics which appear when interdisciplinary problems are considered. There are many monographs on the subjects of solid mechanics and thermomechanics, on fluid mechanics and on coupled fields but most of them cover only special problems in great details which are characteristic for the chosen field. It is rather seldom that relations between these fields are discussed. This concerns, for instance, large deformations of the skeleton of porous materials with diffusion (e.g. lungs), couplings of deformable particles with the fluid motion in suspensions, couplings of adsorption processes and chemical reactions in immiscible mixtures with diffusion, various multi-component aspects of the motion, e.g. of avalanches, such as segregation processes, etc...
Multigrid treatment of implicit continuum diffusion
Francisquez, Manaure; Zhu, Ben; Rogers, Barrett
2017-10-01
Implicit treatment of diffusive terms of various differential orders common in continuum mechanics modeling, such as computational fluid dynamics, is investigated with spectral and multigrid algorithms in non-periodic 2D domains. In doubly periodic time dependent problems these terms can be efficiently and implicitly handled by spectral methods, but in non-periodic systems solved with distributed memory parallel computing and 2D domain decomposition, this efficiency is lost for large numbers of processors. We built and present here a multigrid algorithm for these types of problems which outperforms a spectral solution that employs the highly optimized FFTW library. This multigrid algorithm is not only suitable for high performance computing but may also be able to efficiently treat implicit diffusion of arbitrary order by introducing auxiliary equations of lower order. We test these solvers for fourth and sixth order diffusion with idealized harmonic test functions as well as a turbulent 2D magnetohydrodynamic simulation. It is also shown that an anisotropic operator without cross-terms can improve model accuracy and speed, and we examine the impact that the various diffusion operators have on the energy, the enstrophy, and the qualitative aspect of a simulation. This work was supported by DOE-SC-0010508. This research used resources of the National Energy Research Scientific Computing Center (NERSC).
Performance-based shape optimization of continuum structures
International Nuclear Information System (INIS)
Liang Qingquan
2010-01-01
This paper presents a performance-based optimization (PBO) method for optimal shape design of continuum structures with stiffness constraints. Performance-based design concepts are incorporated in the shape optimization theory to achieve optimal designs. In the PBO method, the traditional shape optimization problem of minimizing the weight of a continuum structure with displacement or mean compliance constraints is transformed to the problem of maximizing the performance of the structure. The optimal shape of a continuum structure is obtained by gradually eliminating inefficient finite elements from the structure until its performance is maximized. Performance indices are employed to monitor the performance of optimized shapes in an optimization process. Performance-based optimality criteria are incorporated in the PBO method to identify the optimum from the optimization process. The PBO method is used to produce optimal shapes of plane stress continuum structures and plates in bending. Benchmark numerical results are provided to demonstrate the effectiveness of the PBO method for generating the maximum stiffness shape design of continuum structures. It is shown that the PBO method developed overcomes the limitations of traditional shape optimization methods in optimal design of continuum structures. Performance-based optimality criteria presented can be incorporated in any shape and topology optimization methods to obtain optimal designs of continuum structures.
PREFACE: Continuum Models and Discrete Systems Symposia (CMDS-12)
Chakrabarti, Bikas K.
2011-09-01
of interest were: Thermodynamics, transport theory and statistical mechanics in the context of continuum modeling discrete systems; Statistical mechanics and dynamics of fluid flows; Continuum mechanics of complex fluids and deformable solids with microstructure; Fundamentals of fracture, defect dynamics, fatigue, and fracture dynamics; Statics and dynamics of dislocations, dislocation mediated phase transitions and plasticity; Granular materials: statics and dynamics; Physics and mechanics of earthquakes; Transport in composite materials; and Continuum theory of soft matter systems of biological motivation and living structures. The scientific program consisted of General Lectures and Research Communications. The four General Lectures (40 min + 5 min) introduced the most recent ideas and advances in the fields covered. The 25 Research Communications reported new results and methods in these fields and were presented orally (30 min + 5 min). In addition there were 15 posters which also presented interesting results and five of these posters were selected by a special committee chaired by David J Bergman to contribute to this proceedings. The selected five posters were presented by Moutushi D Choudhury, Morten Grova, Arya Paul, Arnab Saha and Amartya Sarkar. We were happy to note that 32 scientists from ten countries and a large number of students (both from India and other countries) participated in this symposium. The talks and poster sessions generated a lot of discussions, arguments and collaborations. The articles that appear in this proceedings are based on the invited talks and selected poster presentations. We would like to thank the Journal of Physics Conference Series (IOP Publishing) for publishing the proceedings of the conference. We would also like to thank all the contributors to this proceedings for their kind co-operation and the referees for their prompt and active support. A number of invited participants (Amit Acharya, Alexander Altland, Kamal K
AN APPARENT REDSHIFT DEPENDENCE OF QUASAR CONTINUUM: IMPLICATION FOR COSMIC DUST EXTINCTION?
Energy Technology Data Exchange (ETDEWEB)
Xie, Xiaoyi; Shen, Shiyin; Shao, Zhengyi; Yin, Jun, E-mail: ssy@shao.ac.cn [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)
2015-04-01
We investigate the luminosity and redshift dependence of the quasar continuum by means of theĀ composite spectrum using a large non-BAL radio-quiet quasar sample drawn from the Sloan Digital Sky Survey. Quasar continuum slopes in the UV-Opt band are measured at two different wavelength ranges, i.e., Ī±{sub Ī½12} (1000 ā¼ 2000 ā«) and Ī±{sub Ī½24} (2000 ā¼ 4000 ā«) derived from aĀ power-law fitting. Generally, the UV spectra slope becomes harder (higher Ī±{sub Ī½}) toward higher bolometric luminosity. On the other hand, when quasars are further grouped into luminosity bins, we find that both Ī±{sub Ī½12} and Ī±{sub Ī½24} show significant anti-correlations with redshift (i.e., the quasar continuum becomes redder toward higher redshift). We suggest that the cosmic dust extinction is very likely the cause of this observed Ī±{sub Ī½} ā z relation. We build a simple cosmic dust extinction model to quantify the observed reddening tendency and find an effective dust density nĻ{sub v} ā¼ 10{sup ā5}h Mpc{sup ā1} at z < 1.5. The other possibilities that could produce such a reddening effect have also been discussed.
Continuum-kinetic-microscopic model of lung clearance due to core-annular fluid entrainment
International Nuclear Information System (INIS)
Mitran, Sorin
2013-01-01
The human lung is protected against aspirated infectious and toxic agents by a thin liquid layer lining the interior of the airways. This airway surface liquid is a bilayer composed of a viscoelastic mucus layer supported by a fluid film known as the periciliary liquid. The viscoelastic behavior of the mucus layer is principally due to long-chain polymers known as mucins. The airway surface liquid is cleared from the lung by ciliary transport, surface tension gradients, and airflow shear forces. This work presents a multiscale model of the effect of airflow shear forces, as exerted by tidal breathing and cough, upon clearance. The composition of the mucus layer is complex and variable in time. To avoid the restrictions imposed by adopting a viscoelastic flow model of limited validity, a multiscale computational model is introduced in which the continuum-level properties of the airway surface liquid are determined by microscopic simulation of long-chain polymers. A bridge between microscopic and continuum levels is constructed through a kinetic-level probability density function describing polymer chain configurations. The overall multiscale framework is especially suited to biological problems due to the flexibility afforded in specifying microscopic constituents, and examining the effects of various constituents upon overall mucus transport at the continuum scale
Understanding Nutrient Processing Under Similar Hydrologic Conditions Along a River Continuum
Garayburu-Caruso, V. A.; Mortensen, J.; Van Horn, D. J.; Gonzalez-Pinzon, R.
2015-12-01
Eutrophication is one of the main causes of water impairment across the US. The fate of nutrients in streams is typically described by the dynamic coupling of physical processes and biochemical processes. However, isolating each of these processes and determining its contribution to the whole system is challenging due to the complexity of the physical, chemical and biological domains. We conducted column experiments seeking to understand nutrient processing in shallow sediment-water interactions along representative sites of the Jemez River-Rio Grande continuum (eight stream orders), in New Mexico (USA). For each stream order, we used a set of 6 columns packed with 3 different sediments, i.e., Silica Cone Density Sand ASTM D 1556 (0.075-2.00 mm), gravel (> 2mm) and native sediments from each site. We incubated the sediments for three months and performed tracer experiments in the laboratory under identical flow conditions, seeking to normalize the physical processes along the river continuum. We added a short-term pulse injection of NO3, resazurin and NaCl to each column and determined metabolism and NO3 processing using the Tracer Additions for Spiraling Curve Characterization method (TASCC). Our methods allowed us to study how changes in bacterial communities and sediment composition along the river continuum define nutrient processing.
AN APPARENT REDSHIFT DEPENDENCE OF QUASAR CONTINUUM: IMPLICATION FOR COSMIC DUST EXTINCTION?
International Nuclear Information System (INIS)
Xie, Xiaoyi; Shen, Shiyin; Shao, Zhengyi; Yin, Jun
2015-01-01
We investigate the luminosity and redshift dependence of the quasar continuum by means of theĀ composite spectrum using a large non-BAL radio-quiet quasar sample drawn from the Sloan Digital Sky Survey. Quasar continuum slopes in the UV-Opt band are measured at two different wavelength ranges, i.e., Ī± Ī½12 (1000 ā¼ 2000 ā«) and Ī± Ī½24 (2000 ā¼ 4000 ā«) derived from aĀ power-law fitting. Generally, the UV spectra slope becomes harder (higher Ī± Ī½ ) toward higher bolometric luminosity. On the other hand, when quasars are further grouped into luminosity bins, we find that both Ī± Ī½12 and Ī± Ī½24 show significant anti-correlations with redshift (i.e., the quasar continuum becomes redder toward higher redshift). We suggest that the cosmic dust extinction is very likely the cause of this observed Ī± Ī½ ā z relation. We build a simple cosmic dust extinction model to quantify the observed reddening tendency and find an effective dust density nĻ v ā¼ 10 ā5 h Mpc ā1 at z < 1.5. The other possibilities that could produce such a reddening effect have also been discussed
Pankavich, S; Ortoleva, P
2010-06-01
The multiscale approach to N-body systems is generalized to address the broad continuum of long time and length scales associated with collective behaviors. A technique is developed based on the concept of an uncountable set of time variables and of order parameters (OPs) specifying major features of the system. We adopt this perspective as a natural extension of the commonly used discrete set of time scales and OPs which is practical when only a few, widely separated scales exist. The existence of a gap in the spectrum of time scales for such a system (under quasiequilibrium conditions) is used to introduce a continuous scaling and perform a multiscale analysis of the Liouville equation. A functional-differential Smoluchowski equation is derived for the stochastic dynamics of the continuum of Fourier component OPs. A continuum of spatially nonlocal Langevin equations for the OPs is also derived. The theory is demonstrated via the analysis of structural transitions in a composite material, as occurs for viral capsids and molecular circuits.
SEACAS Theory Manuals: Part II. Nonlinear Continuum Mechanics
Energy Technology Data Exchange (ETDEWEB)
Attaway, S.W.; Laursen, T.A.; Zadoks, R.I.
1998-09-01
This report summarizes the key continuum mechanics concepts required for the systematic prescription and numerical solution of finite deformation solid mechanics problems. Topics surveyed include measures of deformation appropriate for media undergoing large deformations, stress measures appropriate for such problems, balance laws and their role in nonlinear continuum mechanics, the role of frame indifference in description of large deformation response, and the extension of these theories to encompass two dimensional idealizations, structural idealizations, and rigid body behavior. There are three companion reports that describe the problem formulation, constitutive modeling, and finite element technology for nonlinear continuum mechanics systems.
Continuum simulations of water flow past fullerene molecules
DEFF Research Database (Denmark)
Popadic, A.; Praprotnik, M.; Koumoutsakos, P.
2015-01-01
We present continuum simulations of water flow past fullerene molecules. The governing Navier-Stokes equations are complemented with the Navier slip boundary condition with a slip length that is extracted from related molecular dynamics simulations. We find that several quantities of interest...... as computed by the present model are in good agreement with results from atomistic and atomistic-continuum simulations at a fraction of the cost. We simulate the flow past a single fullerene and an array of fullerenes and demonstrate that such nanoscale flows can be computed efficiently by continuum flow...
Expansion of continuum functions on resonance wave functions and amplitudes
International Nuclear Information System (INIS)
Bang, J.; Gareev, F.A.; Gizzatkulov, M.H.; Goncharov, S.A.
1978-01-01
To overcome difficulties encountered with wave functions of continuum spectrum (for example, in a shell model with continuum) the pole expansion (by the Mittag-Leffler theorem) of wave functions, scattering amplitudes and the Green functions with positive energies are considered. It is shown that resonance functions (the Gamov functions) form a complete set over which the continuum functions could be expanded. The general view of these expansions for final potentials and for the Coulomb repulsion potential are obtained and discussed. It is shown that the application of the method to nuclear structure calculations leads to simple algebraic equations
Institute of Scientific and Technical Information of China (English)
ę“å¤©ę°
2003-01-01
The purpose is to reestablish the balance laws of momentum, angular momentumand energy and to derive the corresponding local and nonlocal balance equations formicromorphic continuum mechanics and couple stress theory. The desired results formicromorphic continuum mechanics and couple stress theory are naturally obtained via directtransitions and reductions from the coupled conservation law of energy for micropolarcontinuum theory, respectively. The basic balance laws and equation s for micromorphiccontinuum mechanics and couple stress theory are constituted by combining these resultsderived here and the traditional conservation laws and equations of mass and microinertiaand the entropy inequality. The incomplete degrees of the former related continuum theoriesare clarified. Finally, some special cases are conveniently derived.
1968-01-01
5 The symposium was held in Freudenstadt from 28\\h to 31 \\ ofAugust st nd 1967 and in Stuttgart from 1 to 2 of September 1967. The proposal to hold this symposium originated with the German Society of Applied Mathematics and Mechanics (GAMM) late in 1964 and was examined by a committee of IUTAM especially appointed for this purpose. The basis of this examination was a report in which the present situation in the field and the possible aims of the symposium were surveyed. Briefly, the aims of the symposium were stated to be 1. the unification of the various approaches developed in recent years with the aim of penetrating into the microscopic world of matter by means of continuum theories; 2. the bridging of the gap between microscopic (or atomic) research on mechanics on one hand, and the phenomenological (or continuum mechanical) approach on the other hand; 3. the physical interpretation and the relation to actual material behaviour of the quantities and laws introduced into the new theories, together with ap...
Continuum approximation of the Fermi-Pasta-Ulam lattice
International Nuclear Information System (INIS)
Martina, L.
1979-01-01
A continuum approximation method is applied in order to discuss the connection between some properties of the infinite Fermi-Pasta-Ulam lattice and the ones displayed by the Korteweg-de Vries equation
Static and dynamic continuum theory liquid crystals a mathematical introduction
Stewart, Iain W
2004-01-01
Providing a rigorous, clear and accessible text for graduate students regardless of scientific background, this text introduces the basic continuum theory for nematic liquid crystals in equilibria, and details its various simple applications.
Asymmetric continuum extreme processes in solids and fluids
Teisseyre, Roman
2014-01-01
This book deals with a class of basic deformations in asymmetric continuum theory. It describes molecular deformations and transport velocities in fluids, strain deformations in solids as well as the molecular transport, important in fracture processes.
Gamma-ray continuum spectra from heavy ion reactions
International Nuclear Information System (INIS)
Beene, J.R.; Halbert, M.L.; Hensley, D.C.; Sarantites, D.G.; Westerberg, L.W.; Geoffroy, K.; Woodward, R.
1979-01-01
A detailed quantitative analysis of the yrast continuum was attempted by subtracting the underlying statistical continnuum in a way that makes allowance for ignorance of its detailed shape. This procedure makes it possible to obtain the moment of inertia as a function of spin over a wide range of spins. The results of this continuum spectra shape analysis can be used to calculate the first and second moments of the continuum multiplicity distribution. Continuum spectra were taken during the bombardment of 150 Nd by 115- and 130-MeV beams of 20 Ne, also the first and second moments of the Ī³-ray multiplicity distribution as a function of the gamma energy. The moment of inertia versus spin and the deduced Yrast continuua are shown. 10 references
Coupling of nonlocal and local continuum models by the Arlequinapproach
Han, Fei; Lubineau, Gilles
2011-01-01
for the 'fine scale' description in which nonlocal interactions are considered to have non-negligible effects. Classical continuum mechanics only involving local contact forces is introduced for the rest of the structure where these nonlocal effects can
Hybrid molecularācontinuum methods: From prototypes to coupling software
Neumann, Philipp; Eckhardt, Wolfgang; Bungartz, Hans-Joachim
2014-01-01
In this contribution, we review software requirements in hybrid molecular-continuum simulations. For this purpose, we analyze a prototype implementation which combines two frameworks-the Molecular Dynamics framework MarDyn and the framework Peano
Evaluation the Effectiveness of the US Navy Leadership Continuum Curricula
National Research Council Canada - National Science Library
Duncan-White, Delores
1997-01-01
.... A Leadership Continuum Survey Questionnaire was developed to identified and analyze the student's attitudes concerning the effectiveness of the knowledge and skills taught in the course and how these...
Dynamic Modelling for Planar Extensible Continuum Robot Manipulators
2006-01-01
to the OCTARM continuum ma- nipulator. The OCTARM manipulator is a biologically inspired soft robot manipulator resembling an elephant trunk or an... octopus arm [18]. The OCTARM, shown in Figure 1, is a three-section robot with nine degrees of freedom. Aside from two axis bending with constant...increasing interest in designing ļæ½biologically inspired ļæ½ continuum robots . Some of these designs are mimicking trunks [8], [25], tentacles [17], [21], [24
Identification of a transcriptional signature for the wound healing continuum
Peake, Matthew A; Caley, Mathew; Giles, Peter J; Wall, Ivan; Enoch, Stuart; Davies, Lindsay C; Kipling, David; Thomas, David W; Stephens, Phil
2014-01-01
There is a spectrum/continuum of adult human wound healing outcomes ranging from the enhanced (nearly scarless) healing observed in oral mucosa to scarring within skin and the nonhealing of chronic skin wounds. Central to these outcomes is the role of the fibroblast. Global gene expression profiling utilizing microarrays is starting to give insight into the role of such cells during the healing process, but no studies to date have produced a gene signature for this wound healing continuum. Mi...
On deformation of complex continuum immersed in a plane space
Kovalev, V. A.; Murashkin, E. V.; Radayev, Y. N.
2018-05-01
The present paper is devoted to mathematical modelling of complex continua deformations considered as immersed in an external plane space. The complex continuum is defined as a differential manifold supplied with metrics induced by the external space. A systematic derivation of strain tensors by notion of isometric immersion of the complex continuum into a plane space of a higher dimension is proposed. Problem of establishing complete systems of irreducible objective strain and extrastrain tensors for complex continuum immersed in an external plane space is resolved. The solution to the problem is obtained by methods of the field theory and the theory of rational algebraic invariants. Strain tensors of the complex continuum are derived as irreducible algebraic invariants of contravariant vectors of the external space emerging as functional arguments in the complex continuum action density. Present analysis is restricted to rational algebraic invariants. Completeness of the considered systems of rational algebraic invariants is established for micropolar elastic continua. Rational syzygies for non-quadratic invariants are discussed. Objective strain tensors (indifferent to frame rotations in the external plane space) for micropolar continuum are alternatively obtained by properly combining multipliers of polar decompositions of deformation and extra-deformation gradients. The latter is realized only for continua immersed in a plane space of the equal mathematical dimension.
Effects of continuum breakdown on hypersonic aerothermodynamics for reacting flow
Holman, Timothy D.; Boyd, Iain D.
2011-02-01
This study investigates the effects of continuum breakdown on the surface aerothermodynamic properties (pressure, stress, and heat transfer rate) of a sphere in a Mach 25 flow of reacting air in regimes varying from continuum to a rarefied gas. Results are generated using both continuum [computational fluid dynamics (CFD)] and particle [direct simulation Monte Carlo (DSMC)] approaches. The DSMC method utilizes a chemistry model that calculates the backward rates from an equilibrium constant. A preferential dissociation model is modified in the CFD method to better compare with the vibrationally favored dissociation model that is utilized in the DSMC method. Tests of these models are performed to confirm their validity and to compare the chemistry models in both numerical methods. This study examines the effect of reacting air flow on continuum breakdown and the surface properties of the sphere. As the global Knudsen number increases, the amount of continuum breakdown in the flow and on the surface increases. This increase in continuum breakdown significantly affects the surface properties, causing an increase in the differences between CFD and DSMC. Explanations are provided for the trends observed.
Directory of Open Access Journals (Sweden)
C. H. A. von Savigny
1999-11-01
Full Text Available Vertical profiles of nitric oxide in the altitude range 90 to 105 km are derived from 553 nm nightglow continuum measurements made with the Wind Imaging Interferometer (WINDII on the Upper Atmosphere Research Satellite (UARS. The profiles are derived under the assumption that the continuum emission is due entirely to the NO+O air afterglow reaction. Vertical profiles of the atomic oxygen density, which are required to determine the nitric oxide concentrations, are derived from coordinated WINDII measurements of the atomic oxygen OI 557.7 nm nightglow emission. Data coverage for local solar times ranging from 20 h to 04 h, and latitudes ranging from 42Ā°S to 42Ā°N, is achieved by zonally averaging and binning data obtained on 18 nights during a two-month period extending from mid-November 1992 until mid-January 1993. The derived nitric oxide concentrations are significantly smaller than those obtained from rocket measurements of the airglow continuum but they do compare well with model expectations and nitric oxide densities measured using the resonance fluorescence technique on the Solar Mesosphere Explorer satellite. The near-global coverage of the WINDII observations and the similarities to the nitric oxide global morphology established from other satellite measurements strongly suggests that the NO+O reaction is the major source of the continuum near 553 nm and that there is no compelling reason to invoke additional sources of continuum emission in this immediate spectral region.Key words. Atmospheric composition and structure (airglow and aurora; thermosphere ā composition and chemistry; instruments and techniques
Integrated radio continuum spectra of galaxies
Energy Technology Data Exchange (ETDEWEB)
Marvil, Joshua; Owen, Frazer [National Radio Astronomy Observatory, 1003 Lopezville Rd, Socorro, NM 87801 (United States); Eilek, Jean, E-mail: josh.marvil@csiro.au [New Mexico Tech, Socorro, NM 87801 (United States)
2015-01-01
We investigate the spectral shape of the total continuum radiation, between 74 MHz and 5 GHz (400-6 cm in wavelength), for a large sample of bright galaxies. We take advantage of the overlapping survey coverage of the VLA Low-Frequency Sky Survey, the Westerbork Northern Sky Survey, the NRAO VLA Sky Survey, and the Green Bank 6 cm Survey to achieve significantly better resolution, sensitivity, and sample size compared to prior efforts of this nature. For our sample of 250 bright galaxies we measure a mean spectral index, Ī±, of ā0.69 between 1.4 and 4.85 GHz, ā0.55 between 325 MHz and 1.4 GHz, and ā0.45 between 74 and 325 MHz, which amounts to a detection of curvature in the mean spectrum. The magnitude of this curvature is approximately ĪĪ± = ā0.2 per logarithmic frequency decade when fit with a generalized function having constant curvature. No trend in low-frequency spectral flattening versus galaxy inclination is evident in our data, suggesting that free-free absorption is not a satisfying explanation for the observed curvature. The ratio of thermal to non-thermal emission is estimated through two independent methods: (1) using the IRAS far-IR fluxes and (2) with the value of the total spectral index. Method (1) results in a distribution of 1.4 GHz thermal fractions of 9% Ā± 3%, which is consistent with previous studies, while method (2) produces a mean 1.4 GHz thermal fraction of 51% with dispersion 26%. The highly implausible values produced by method (2) indicate that the sum of typical power-law thermal and non-thermal components is not a viable model for the total spectral index between 325 and 1.4 GHz. An investigation into relationships between spectral index, infrared-derived quantities, and additional source properties reveals that galaxies with high radio luminosity in our sample are found to have, on average, a flatter radio spectral index, and early types tend to have excess radio emission when compared to the radio-infrared ratio of later
Directory of Open Access Journals (Sweden)
Elodie eSaubin
2016-05-01
Full Text Available The mechanisms of hazardous silicic eruptions are controlled by complex, poorly-understood conduit processes. Observations of recent Chilean rhyolite eruptions have revealed the importance of hybrid activity, involving simultaneous explosive and effusive emissions from a common vent. Such behaviour hinges upon the ability of gas to decouple from magma in the shallow conduit. Tuffisite veins are increasingly suspected to be a key facilitator of outgassing, as they repeatedly provide a transient permeable escape route for volcanic gases. Intersection of foam domains by tuffisite veins appears critical to efficient outgassing. However, knowledge is currently lacking into textural heterogeneities within shallow conduits, their relationship with tuffisite vein propagation, and the implications for fragmentation and degassing processes. Similarly, the magmatic vesiculation response to upper conduit pressure perturbations, such as those related to the slip of dense magma plugs, remains largely undefined. Here we provide a detailed characterization of an exceptionally large tuffisite vein within a rhyolitic obsidian bomb ejected during transitional explosive-effusive activity at ChaitĆ©n, Chile in May 2008. Vein textures and chemistry provide a time-integrated record of the invasion of a dense upper conduit plug by deeper fragmented magma. Quantitative textural analysis reveals diverse vesiculation histories of various juvenile clast types.Using vesicle size distributions, bubble number densities, zones of diffusive water depletion, and glass H2O concentrations, we propose a multi-step degassing/fragmentation history, spanning deep degassing to explosive bomb ejection. Rapid decompression events of ~3-4 MPa are associated with fragmentation of foam and dense magma at ~200-350 metres depth in the conduit, permitting vertical gas and pyroclast mobility over hundreds of metres. Permeable pathway occlusion in the dense conduit plug by pyroclast accumulation
Pingitore, N. E., Jr.; Clague, J. W.; Gorski, D.
2014-12-01
The Round Top Mountain peraluminous rhyolite, exposed at the surface in Sierra Blanca, Hudspeth County, west Texas, USA, is enriched in yttrium and heavy rare earth elements (YHREEs). Other potentially valuable elements in the deposit include Be, Li, U, Th, Sn, F, Nb, and Ta. Texas Rare Earth Resources Corp. proposes to extract the YHREEs from the host mineral variety yttrofluorite by inexpensive heap leaching with dilute sulfuric acid, which also releases some of the Be, Li, U, F, and Th from other soluble minor minerals. Data: Feldspars and quartz comprise 90-95% of the rhyolite, with pheonocrysts of up to 250 microns set in an aphanitic matrix that hosts the typically sub-micron target yttrofluorite. Reverse circulation cuttings from some 100 drill holes, two drill cores, and outcrop and trench observations suggest striking physical homogeneity through this billion-plus ton surface-exposed laccolith, about 1200 feet high and a mile in diameter (375 x 1600 m). Gray to pink, and other minor hues, color variation derives from magnetiteāhematite redox reaction. Plots of Y, 13 REEs, U, Th, and Nb analyses from over 1500 samples collected from 64 drill holes (color codes in figure) exhibit remarkably little variation in the concentration of these elements with geographic position or depth within the laccolith. Importance: Uniform mineralization grades help insure against the mining production surprises often associated with vein deposits and heterogeneous open pit deposits. At Round Top, mine feedstock can be relatively constant over the life of the mine (multiple decades), so the mechanical mining process can be optimized early on and not need expensive alterations later. Likewise, the chemical and physical parameters of the heap leach can be perfected. The sensitive and expensive process of extraction of elements and element groups from the pregnant leach solution and purification also can be optimized. Origin: The remarkable homogeneity of the YHREE distribution
Directory of Open Access Journals (Sweden)
MilaÅ”inoviÄ Dragan D.
2015-01-01
Full Text Available A new analytical model for the prediction of concrete response under uniaxial compression and its experimental verification is presented in this paper. The proposed approach, referred to as the rheological-dynamical continuum damage model, combines rheological-dynamical analogy and damage mechanics. Within the framework of this approach the key continuum parameters such as the creep coefficient, Poissonās ratio and damage variable are functionally related. The critical values of the creep coefficient and damage variable under peak stress are used to describe the failure mode of the concrete cylinder. The ultimate strain is determined in the post-peak regime only, using the secant stress-strain relation from damage mechanics. The post-peak branch is used for the energy analysis. Experimental data for five concrete compositions were obtained during the examination presented herein. The principal difference between compressive failure and tensile fracture is that there is a residual stress in the specimens, which is a consequence of uniformly accelerated motion of load during the examination of compressive strength. The critical interpenetration displacements and crushing energy are obtained theoretically based on the concept of global failure analysis. [Projekat Ministarstva nauke Republike Srbije, br. ON 174027: Computational Mechanics in Structural Engineering i br. TR 36017: Utilization of by-products and recycled waste materials in concrete composites for sustainable construction development in Serbia: Investigation and environmental assessment of possible applications
Singer, B. S.
2014-12-01
The Laguna del Maule Volcanic Field, Chile, includes an unusually large and recent concentration of silicic eruptions. Since 2007 the crust here has been inflating at an astonishing rate of 25 cm/yr. Findings thus far lead to the hypothesis that the silicic vents have tapped an extensive layer of crystal-poor, rhyolitic melt that began to form atop a magmatic mush zone that was established by ~20 ka with a renewed phase of rhyolite eruptions during the Holocene. Modeling of surface deformation, magnetotelluric data, and gravity changes suggest that magma is currently intruding at a depth of ~5 km. Swarms of volcano-tectonic and long period earthquakes, mostly of M San Juan-Argentina, Nanyang Technological University-Singapore, SERNAGEOMIN, OVDAS, USGS, and SEGEMAR-Argentina. Team members will be introduced in this presentation. Our approach includes augmenting the OVDAS array of 6 permanent seisic stations with 40 additional instruments to conduct tomographic, receiver function and ambient noise studies. We continue to collect 4-D gravity data from 37 stations. Surface deformation is monitored via cGPS at 5 permanent receivers and InSAR data. A magnetotelluric survey across the Andes at 36o S is planned. Geochemical studies include mineral zoning and U-Th disequilibrium of zircons to constrain the timing of magma intrusion and mixing events prior to the current unrest. The overall aim is to integrate these observations and to construct numerical models of system dynamics. We are developing communications protocols and a web site to facilitate sharing of findings among the team members and with the public.
Theoretical Calculation and Validation of the Water Vapor Continuum Absorption
Ma, Qiancheng; Tipping, Richard H.
1998-01-01
The primary objective of this investigation is the development of an improved parameterization of the water vapor continuum absorption through the refinement and validation of our existing theoretical formalism. The chief advantage of our approach is the self-consistent, first principles, basis of the formalism which allows us to predict the frequency, temperature and pressure dependence of the continuum absorption as well as provide insights into the physical mechanisms responsible for the continuum absorption. Moreover, our approach is such that the calculated continuum absorption can be easily incorporated into satellite retrieval algorithms and climate models. Accurate determination of the water vapor continuum is essential for the next generation of retrieval algorithms which propose to use the combined constraints of multi-spectral measurements such as those under development for EOS data analysis (e.g., retrieval algorithms based on MODIS and AIRS measurements); current Pathfinder activities which seek to use the combined constraints of infrared and microwave (e.g., HIRS and MSU) measurements to improve temperature and water profile retrievals, and field campaigns which seek to reconcile spectrally-resolved and broad-band measurements such as those obtained as part of FIRE. Current widely used continuum treatments have been shown to produce spectrally dependent errors, with the magnitude of the error dependent on temperature and abundance which produces errors with a seasonal and latitude dependence. Translated into flux, current water vapor continuum parameterizations produce flux errors of order 10 W/ml, which compared to the 4 W/m' magnitude of the greenhouse gas forcing and the 1-2 W/m' estimated aerosol forcing is certainly climatologically significant and unacceptably large. While it is possible to tune the empirical formalisms, the paucity of laboratory measurements, especially at temperatures of interest for atmospheric applications, preclude tuning
ALMA BAND 8 CONTINUUM EMISSION FROM ORION SOURCE I
Energy Technology Data Exchange (ETDEWEB)
Hirota, Tomoya; Matsumoto, Naoko [Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka-shi, Tokyo 181-8588 (Japan); Machida, Masahiro N.; Matsushita, Yuko [Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, Motooka 744, Nishi-ku, Fukuoka-shi, Fukuoka 819-0395 (Japan); Motogi, Kazuhito; Honma, Mareki [Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Hoshigaoka2-12, Mizusawa-ku, Oshu-shi, Iwate 023-0861 (Japan); Kim, Mi Kyoung [Korea Astronomy and Space Science Institute, Hwaam-dong 61-1, Yuseong-gu, Daejeon, 305-348 (Korea, Republic of); Burns, Ross A., E-mail: tomoya.hirota@nao.ac.jp [Joint Institute for VLBI in Europe, Postbus 2, 7990 AA, Dwingeloo (Netherlands)
2016-12-20
We have measured continuum flux densities of a high-mass protostar candidate, a radio sourceĀ I in the OrionĀ KL region (Orion Source I) using the Atacama Large Millimeter/Submillimeter Array (ALMA) at bandĀ 8 with an angular resolution of 0.ā³1. The continuum emission at 430, 460, and 490 GHz associated with SourceĀ I shows an elongated structure along the northwestāsoutheast direction perpendicular to the so-called low-velocity bipolar outflow. The deconvolved size of the continuum source, 90Ā auĀ ĆĀ 20Ā au, is consistent with those reported previously at other millimeter/submillimeter wavelengths. The flux density can be well fitted to the optically thick blackbody spectral energy distribution, and the brightness temperature is evaluated to be 700ā800Ā K. It is much lower than that in the case of protonāelectron or H{sup ā} freeāfree radiations. Our data are consistent with the latest ALMA results by Plambeck and Wright, in which the continuum emission was proposed to arise from the edge-on circumstellar disk via thermal dust emission, unless the continuum source consists of an unresolved structure with a smaller beam filling factor.
Reducing Actuator Requirements in Continuum Robots Through Optimized Cable Routing.
Case, Jennifer C; White, Edward L; SunSpiral, Vytas; Kramer-Bottiglio, Rebecca
2018-02-01
Continuum manipulators offer many advantages compared to their rigid-linked counterparts, such as increased degrees of freedom and workspace volume. Inspired by biological systems, such as elephant trunks and octopus tentacles, many continuum manipulators are made of multiple segments that allow large-scale deformations to be distributed throughout the body. Most continuum manipulators currently control each segment individually. For example, a planar cable-driven system is typically controlled by a pair of cables for each segment, which implies two actuators per segment. In this article, we demonstrate how highly coupled crossing cable configurations can reduce both actuator count and actuator torque requirements in a planar continuum manipulator, while maintaining workspace reachability and manipulability. We achieve highly coupled actuation by allowing cables to cross through the manipulator to create new cable configurations. We further derive an analytical model to predict the underactuated manipulator workspace and experimentally verify the model accuracy with a physical system. We use this model to compare crossing cable configurations to the traditional cable configuration using workspace performance metrics. Our work here focuses on a simplified planar robot, both in simulation and in hardware, with the goal of extending this to spiraling-cable configurations on full 3D continuum robots in future work.
An advanced kinetic theory for morphing continuum with inner structures
Chen, James
2017-12-01
Advanced kinetic theory with the Boltzmann-Curtiss equation provides a promising tool for polyatomic gas flows, especially for fluid flows containing inner structures, such as turbulence, polyatomic gas flows and others. Although a Hamiltonian-based distribution function was proposed for diatomic gas flow, a general distribution function for the generalized Boltzmann-Curtiss equations and polyatomic gas flow is still out of reach. With assistance from Boltzmann's entropy principle, a generalized Boltzmann-Curtiss distribution for polyatomic gas flow is introduced. The corresponding governing equations at equilibrium state are derived and compared with Eringen's morphing (micropolar) continuum theory derived under the framework of rational continuum thermomechanics. Although rational continuum thermomechanics has the advantages of mathematical rigor and simplicity, the presented statistical kinetic theory approach provides a clear physical picture for what the governing equations represent.
Unexpected strong attraction in the presence of continuum bound state
International Nuclear Information System (INIS)
Delfino, A.; Frederico, T.
1992-06-01
The result of few-particle ground-state calculation employing a two-particle non-local potential supporting a continuum bound state in addition to a negative-energy bound state has occasionally revealed unexpected large attraction in producing a very strongly bound ground state. In the presence of the continuum bound state the difference of phase shift between zero and infinite energies has an extra jump of Ļ as in the presence of an additional bound state. The wave function of the continuum bound state is identical with that of a strongly bound negative-energy state, which leads us to postulate a pseudo bound state in the two-particle system in order to explain the unexpected attraction. The role of the Pauli forbidden states is expected to be similar to these pseudo states. (author)
Alfven continuum and high-frequency eigenmodes in optimized stellarators
International Nuclear Information System (INIS)
Kolesnichenko, Ya.I.; Lutsenko, V.V.; Wobig, H.; Yakovenko, Yu.V.; Fesenyuk, O.P.
2001-01-01
An equation of shear Alfven eigenmodes (AE) in optimized stellarators of Wendelstein line (Helias configurations) is derived. The metric tensor coefficients, which are contained in this equation, are calculated analytically. Two numerical codes are developed: the first one, COBRA (COntinuum BRanches of Alfven waves), is intended for the investigation of the structure of Alfven continuum; the second, BOA (Branches Of Alfven modes), solves the eigenvalue problem. The family of possible gaps in Alfven continuum of a Helias configuration is obtained. It is predicted that there exist gaps which arise due to or are strongly affected by the variation of the shape of the plasma cross section along the large azimuth of the torus. In such gaps, discrete eigenmodes, namely, helicity-induced eigenmodes (HAE 21 ) and mirror-induced eigenmodes (MAE) are found. It is shown that plasma inhomogeneity may suppress the AEs with a wide region of localization
Continuum mechanics using Mathematica fundamentals, methods, and applications
Romano, Antonio
2014-01-01
This textbook's methodological approach familiarizes readers with the mathematical tools required to correctly define and solve problems in continuum mechanics. Covering essential principles and fundamental applications, this second edition of Continuum Mechanics using MathematicaĀ® provides a solid basis for a deeper study of more challenging and specialized problems related to nonlinear elasticity, polar continua, mixtures, piezoelectricity, ferroelectricity, magneto-fluid mechanics, and state changes (see A. Romano, A. Marasco, Continuum Mechanics: Advanced Topics and Research Trends, Springer (BirkhĆ¤user), 2010, ISBN 978-0-8176-4869-5). Key topics and features: * Concise presentation strikes a balance between fundamentals and applications * Requisite mathematical background carefully collected in two introductory chapters and one appendix * Recent developments highlighted through coverage of more significant applications to areas such as wave propagation, fluid mechanics, porous media, linear elasticity....
ICMS Workshop on Differential Geometry and Continuum Mechanics
Grinfeld, Michael; Knops, R
2015-01-01
This book examines the exciting interface between differential geometry and continuum mechanics, now recognised as being of increasing technological significance. Topics discussed include isometric embeddings in differential geometry and the relation with microstructure in nonlinear elasticity, the use of manifolds in the description of microstructure in continuum mechanics, experimental measurement of microstructure, defects, dislocations, surface energies, and nematic liquid crystals. Compensated compactness in partial differential equations is also treated. The volume is intended for specialists and non-specialists in pure and applied geometry, continuum mechanics, theoretical physics, materials and engineering sciences, and partial differential equations. It will also be of interest to postdoctoral scientists and advanced postgraduate research students. These proceedings include revised written versions of the majority of papers presented by leading experts at the ICMS Edinburgh Workshop on Differential G...
Transport of optical excitations on dendrimers in the continuum approximation
International Nuclear Information System (INIS)
Vlaming, S.M.; Heijs, D.J.; Knoester, J.
2005-01-01
We study the incoherent transport of optical excitations created at the rim of a dendritic molecule to a trap occurring at the core. The corresponding discrete random walk is treated in a continuum approximation, resulting in a diffusion-like process which admits semi-analytical solutions. The thus obtained arrival time distribution for the excitation at the trap is compared with the one for the original, discrete problem. In the case of an inward bias or even a weak outward one, the agreement is very good and the continuum approximation provides a good alternative description of the energy transfer process, even for small dendrimers. In the case of a strong outward bias, the mean trapping time, which sets the time scale for the entire distribution, depends exponentially on the number of generations in both approaches, but with a different base. The failure of the continuum approximation for this case is explained from the peaked behavior of the excitation density near the rim
Lattice fluid dynamics from perfect discretizations of continuum flows
International Nuclear Information System (INIS)
Katz, E.; Wiese, U.
1998-01-01
We use renormalization group methods to derive equations of motion for large scale variables in fluid dynamics. The large scale variables are averages of the underlying continuum variables over cubic volumes and naturally exist on a lattice. The resulting lattice dynamics represents a perfect discretization of continuum physics, i.e., grid artifacts are completely eliminated. Perfect equations of motion are derived for static, slow flows of incompressible, viscous fluids. For Hagen-Poiseuille flow in a channel with a square cross section the equations reduce to a perfect discretization of the Poisson equation for the velocity field with Dirichlet boundary conditions. The perfect large scale Poisson equation is used in a numerical simulation and is shown to represent the continuum flow exactly. For nonsquare cross sections one can use a numerical iterative procedure to derive flow equations that are approximately perfect. copyright 1998 The American Physical Society
Continuum solutions of the Klein-Gordon equation
International Nuclear Information System (INIS)
Jansen, G.; Pusch, M.; Soff, G.
1987-10-01
We construct explicit solutions of the Klein-Gordon equation for continuum states. The role of the energy in the single-particle Klein-Gordon theory is elucidated. Special emphasis is laid on the determination of resonance states in the continuum for overcritical potentials. As examples for long-range interaction we depict solutions for the Coulomb potential of a point-like nucleus as an extended nucleus. The square-well potential and the exponential potential are treated to exemplify pecularities of short-range interactions. We also derive continuum solutions for a scalar interaction of square-well type. Finally we discuss the behaviour of a spin-0 particle in an external homogeneous magnetic field. (orig.)
HIV continuum of care in Europe and Central Asia.
Drew, R S; Rice, B; RĆ¼Ć¼tel, K; Delpech, V; Attawell, K A; Hales, D K; Velasco, C; Amato-Gauci, A J; Pharris, A; Tavoschi, L; Noori, T
2017-08-01
The European Centre for Disease Prevention and Control (ECDC) supports countries to monitor progress in their response to the HIV epidemic. In line with these monitoring responsibilities, we assess how, and to what extent, the continuum of care is being measured across countries. The ECDC sent out questionnaires to 55 countries in Europe and Central Asia in 2014. Nominated country representatives were questioned on how they defined and measured six elements of the continuum. We present our results using three previously described frameworks [breakpoints; Joint United Nations Programme on HIV/AIDS (UNAIDS) 90-90-90 targets; diagnosis and treatment quadrant]. Forty countries provided data for at least one element of the continuum. Countries reported most frequently on the number of people diagnosed with HIV infection (37; 93%), and on the number in receipt of antiretroviral therapy (ART) (35; 88%). There was little consensus across countries in their approach to defining linkage to, and retention in, care. The most common breakpoint (>19% reduction between two adjacent elements) related to the estimated number of people living with HIV who were diagnosed (18 of 23; 78%). We present continuum data from multiple countries that provide both a snapshot of care provision and a baseline against which changes over time in care provision across Europe and Central Asia may be measured. To better inform HIV testing and treatment programmes, standard data collection approaches and definitions across the HIV continuum of care are needed. If countries wish to ensure an unbroken HIV continuum of care, people living with HIV need to be diagnosed promptly, and ART needs to be offered to all those diagnosed. Ā© 2017 The Authors. HIV Medicine published by John Wiley & Sons Ltd on behalf of British HIV Association.
Bound states in continuum: Quantum dots in a quantum well
Energy Technology Data Exchange (ETDEWEB)
ProdanoviÄ, Nikola, E-mail: elnpr@leeds.ac.uk [Institute of Microwaves and Photonics, School of Electronic and Electrical Engineering, University of Leeds, Woodhouse Lane, Leeds LS2 9JT (United Kingdom); MilanoviÄ, Vitomir [School of Electrical Engineering, University of Belgrade, Bulevar Kralja Aleksandra 73, 11000 Belgrade (Serbia); IkoniÄ, Zoran; Indjin, Dragan; Harrison, Paul [Institute of Microwaves and Photonics, School of Electronic and Electrical Engineering, University of Leeds, Woodhouse Lane, Leeds LS2 9JT (United Kingdom)
2013-11-01
We report on the existence of a bound state in the continuum (BIC) of quantum rods (QR). QRs are novel elongated InGaAs quantum dot nanostructures embedded in the shallower InGaAs quantum well. BIC appears as an excited confined dot state and energetically above the bottom of a well subband continuum. We prove that high height-to-diameter QR aspect ratio and the presence of a quantum well are indispensable conditions for accommodating the BIC. QRs are unique semiconductor nanostructures, exhibiting this mathematical curiosity predicted 83 years ago by Wigner and von Neumann.
Relativistic continuum physics for the description of heavy ion collisions
International Nuclear Information System (INIS)
Lukacs, Bela
1986-01-01
The application of relativistic continuum physics to the description of the nuclear fireball evolution from the start of expansion to the breaking is discussed. The basic formalism and basic assumptions of relativistic hydrodynamics and thermodynamics are analyzed in detail. The four basic assumptions are not valid in the case of nuclear fireball produced in heavy ion collisions, but thermodynamics can be extended in different ways to incorporate anisotropy, fluctuations, gradients and the lack of the local equilibrium. The extended continuum formalism is applicable to the description of the nuclear fireball dynamics, including the nuclear - quark matter phase transition. (D.Gy.)
Continuum damage mechanics method for fatigue growth of surface cracks
International Nuclear Information System (INIS)
Feng Xiqiao; He Shuyan
1997-01-01
With the background of leak-before-break (LBB) analysis of pressurized vessels and pipes in nuclear plants, the fatigue growth problem of either circumferential or longitudinal semi-elliptical surface cracks subjected to cyclic loading is studied by using a continuum damage mechanics method. The fatigue damage is described by a scalar damage variable. From the damage evolution equation at the crack tip, a crack growth equation similar to famous Paris' formula is derived, which shows the physical meaning of Paris' formula. Thereby, a continuum damage mechanics approach is developed to analyze the configuration evolution of surface cracks during fatigue growth
Fractional Quantum Field Theory: From Lattice to Continuum
Directory of Open Access Journals (Sweden)
Vasily E. Tarasov
2014-01-01
Full Text Available An approach to formulate fractional field theories on unbounded lattice space-time is suggested. A fractional-order analog of the lattice quantum field theories is considered. Lattice analogs of the fractional-order 4-dimensional differential operators are proposed. We prove that continuum limit of the suggested lattice field theory gives a fractional field theory for the continuum 4-dimensional space-time. The fractional field equations, which are derived from equations for lattice space-time with long-range properties of power-law type, contain the Riesz type derivatives on noninteger orders with respect to space-time coordinates.
Shape Modeling of a Concentric-tube Continuum Robot
DEFF Research Database (Denmark)
Bai, Shaoping; Xing, Charles Chuhao
2012-01-01
Concentric-tube continuum robots feature with simple and compact structures and have a great potential in medical applications. The paper is concerned with the shape modeling of a type of concentric-tube continuum robot built with a collection of super-elastic NiTiNol tubes. The mechanics...... is modeled on the basis of energy approach for both the in-plane and out-plane cases. The torsional influences on the shape of the concentric-tube robots are considered. An experimental device was build for the model validation. The results of simulation and experiments are included and analyzed....
Towards an improved continuum theory for phase transformations
International Nuclear Information System (INIS)
Tijssens, M.G.A.; James, R.D.
2003-01-01
We develop a continuum theory for martensitic phase transformations in which explicit use is made of atomistic calculations based on density functional theory. Following the work of Rabe and coworkers, branches of the phonon-dispersion relation with imaginary frequencies are selected to construct a localized basis tailored to the symmetry of the crystal lattice. This so-called Wannier basis helps to construct an effective Hamiltonian of a particularly simple form. We extend the methodology by incorporating finite deformations and passing the effective Hamiltonian fully to continuum level. The developments so far are implemented on the shape memory material NiTi
A Coupling Tool for Parallel Molecular Dynamics-Continuum Simulations
Neumann, Philipp
2012-06-01
We present a tool for coupling Molecular Dynamics and continuum solvers. It is written in C++ and is meant to support the developers of hybrid molecular - continuum simulations in terms of both realisation of the respective coupling algorithm as well as parallel execution of the hybrid simulation. We describe the implementational concept of the tool and its parallel extensions. We particularly focus on the parallel execution of particle insertions into dense molecular systems and propose a respective parallel algorithm. Our implementations are validated for serial and parallel setups in two and three dimensions. Ā© 2012 IEEE.
The continuum of spreading depolarizations in acute cortical lesion development
DEFF Research Database (Denmark)
Hartings, Jed A; Shuttleworth, C William; Kirov, Sergei A
2017-01-01
A modern understanding of how cerebral cortical lesions develop after acute brain injury is based on Aristides LeĆ£o's historic discoveries of spreading depression and asphyxial/anoxic depolarization. Treated as separate entities for decades, we now appreciate that these events define a continuum....... The causal role of these waves in lesion development has been proven by real-time monitoring of electrophysiology, blood flow, and cytotoxic edema. The spreading depolarization continuum further applies to other models of acute cortical lesions, suggesting that it is a universal principle of cortical lesion...
Continuum limit and improved action in lattice theories. Pt. 1
International Nuclear Information System (INIS)
Symanzik, K.
1983-03-01
Corrections to continuum theory results stemming from finite lattice-spacing can be diminished systematically by use of lattice actions that include also suitable irrelevant terms. We describe in detail the principles of such constructions at the example of PHI 4 theory. (orig.)
Proposed higher order continuum-based models for an elastic ...
African Journals Online (AJOL)
Three new variants of continuum-based models for an elastic subgrade are proposed. The subgrade is idealized as a homogenous, isotropic elastic layer of thickness H overlying a firm stratum. All components of the stress tensor in the subgrade are taken into account. Reasonable assumptions are made regarding theĀ ...
On the continuum limit of a classical compressible Heisenberg chain
International Nuclear Information System (INIS)
Fivez, J.
1982-01-01
The equations of motion are derived for the classical compressible Heisenberg chain in the continuum limit to lowest non-trivial order in the derivatives. It is possible to eliminate the translations from the equation for the spins. The resulting equation does not admit of simple magnetic solitary wave solutions, in contradiction to the results of other authors. (author)
From discrete particles to continuum fields in mixtures
Weinhart, Thomas; Thornton, Anthony Richard; Yu, A; Dong, K; Yang, R; Luding, S; Luding, Stefan
2013-01-01
We present a novel way to extract continuum fields from discrete particle systems that is applicable to flowing mixtures as well as boundaries and interfaces. The mass and momentum balance equations for mixed flows are expressed in terms of the partial densities, velocities, stresses and interaction
Modeling of Continuum Manipulators Using Pythagorean Hodograph Curves.
Singh, Inderjeet; Amara, Yacine; Melingui, Achille; Mani Pathak, Pushparaj; Merzouki, Rochdi
2018-05-10
Research on continuum manipulators is increasingly developing in the context of bionic robotics because of their many advantages over conventional rigid manipulators. Due to their soft structure, they have inherent flexibility, which makes it a huge challenge to control them with high performances. Before elaborating a control strategy of such robots, it is essential to reconstruct first the behavior of the robot through development of an approximate behavioral model. This can be kinematic or dynamic depending on the conditions of operation of the robot itself. Kinematically, two types of modeling methods exist to describe the robot behavior; quantitative methods describe a model-based method, and qualitative methods describe a learning-based method. In kinematic modeling of continuum manipulator, the assumption of constant curvature is often considered to simplify the model formulation. In this work, a quantitative modeling method is proposed, based on the Pythagorean hodograph (PH) curves. The aim is to obtain a three-dimensional reconstruction of the shape of the continuum manipulator with variable curvature, allowing the calculation of its inverse kinematic model (IKM). It is noticed that the performances of the PH-based kinematic modeling of continuum manipulators are considerable regarding position accuracy, shape reconstruction, and time/cost of the model calculation, than other kinematic modeling methods, for two cases: free load manipulation and variable load manipulation. This modeling method is applied to the compact bionic handling assistant (CBHA) manipulator for validation. The results are compared with other IKMs developed in case of CBHA manipulator.
Assessing continuum postulates in simulations of granular flow
Energy Technology Data Exchange (ETDEWEB)
Rycroft, Chris; Kamrin, Ken; Bazant, Martin
2008-08-26
Continuum mechanics relies on the fundamental notion of a mesoscopic volume"element" in which properties averaged over discrete particles obey deterministic relationships. Recent work on granular materials suggests a continuum law may be inapplicable, revealing inhomogeneities at the particle level, such as force chains and slow cage breaking. Here, we analyze large-scale three-dimensional Discrete-Element Method (DEM) simulations of different granular flows and show that an approximate"granular element" defined at the scale of observed dynamical correlations (roughly three to five particle diameters) has a reasonable continuum interpretation. By viewing all the simulations as an ensemble of granular elements which deform and move with the flow, we can track material evolution at a local level. Our results confirm some of the hypotheses of classical plasticity theory while contradicting others and suggest a subtle physical picture of granular failure, combining liquid-like dependence on deformation rate and solid-like dependence on strain. Our computational methods and results can be used to guide the development of more realistic continuum models, based on observed local relationships betweenaverage variables.
Fundamentals of continuum mechanics ā classical approaches and new trends
Altenbach, H.
2018-04-01
Continuum mechanics is a branch of mechanics that deals with the analysis of the mechanical behavior of materials modeled as a continuous manifold. Continuum mechanics models begin mostly by introducing of three-dimensional Euclidean space. The points within this region are defined as material points with prescribed properties. Each material point is characterized by a position vector which is continuous in time. Thus, the body changes in a way which is realistic, globally invertible at all times and orientation-preserving, so that the body cannot intersect itself and as transformations which produce mirror reflections are not possible in nature. For the mathematical formulation of the model it is also assumed to be twice continuously differentiable, so that differential equations describing the motion may be formulated. Finally, the kinematical relations, the balance equations, the constitutive and evolution equations and the boundary and/or initial conditions should be defined. If the physical fields are non-smooth jump conditions must be taken into account. The basic equations of continuum mechanics are presented following a short introduction. Additionally, some examples of solid deformable continua will be discussed within the presentation. Finally, advanced models of continuum mechanics will be introduced. The paper is dedicated to Alexander Manzhirovās 60th birthday.
Absorption of continuum radiation in a resonant expanding gaseous sphere
International Nuclear Information System (INIS)
Shaparev, N Y
2014-01-01
The paper deals with absorption of external continuum radiation in a self-similarly expanding gaseous sphere. Frequency probability and integral probability of radiation absorption in the resonance frequency range are determined depending on the expansion velocity gradient and thickness of the optical medium. It is shown that expansion results in a reduced optical thickness of the medium and enhanced integral absorption. (paper)
Relativistic continuum random phase approximation in spherical nuclei
International Nuclear Information System (INIS)
Daoutidis, Ioannis
2009-01-01
Covariant density functional theory is used to analyze the nuclear response in the external multipole fields. The investigations are based on modern functionals with zero range and density dependent coupling constants. After a self-consistent solution of the Relativistic Mean Field (RMF) equations for the nuclear ground states multipole giant resonances are studied within the Relativistic Random Phase Approximation (RRPA), the small amplitude limit of the time-dependent RMF. The coupling to the continuum is treated precisely by calculating the single particle Greens-function of the corresponding Dirac equation. In conventional methods based on a discretization of the continuum this was not possible. The residual interaction is derived from the same RMF Lagrangian. This guarantees current conservation and a precise decoupling of the Goldstone modes. For nuclei with open shells pairing correlations are taken into account in the framework of BCS theory and relativistic quasiparticle RPA. Continuum RPA (CRPA) presents a robust method connected with an astonishing reduction of the numerical effort as compared to conventional methods. Modes of various multipolarities and isospin are investigated, in particular also the newly discovered Pygmy modes in the vicinity of the neutron evaporation threshold. The results are compared with conventional discrete RPA calculations as well as with experimental data. We find that the full treatment of the continuum is essential for light nuclei and the study of resonances in the neighborhood of the threshold. (orig.)
The Continuum of Literacy in American Indian Communities.
Zepeda, Ofelia
1995-01-01
Describes the O'odham language and oral tradition of the Tohono O'odham Indians of southern Arizona, relating it to the development of O'odham children's English literacy. Oral tradition and school literacy constitute opposite ends of a literacy continuum, in which English literacy is often isolated from and in conflict with O'odham literacy. (10ā¦
Self-Assessment Exercises in Continuum Mechanics with Autonomous Learning
MarcĆ©-NoguĆ©, Jordi; Gil, LLuĆs; PĆ©rez, Marco A.; SĆ”nchez, Montserrat
2013-01-01
The main objective of this work is to generate a set of exercises to improve the autonomous learning in "Continuum Mechanics" through a virtual platform. Students will have to resolve four exercises autonomously related to the subject developed in class and they will post the solutions on the virtual platform within a deadline. Studentsā¦
The Eating Disorders Continuum, Self-Esteem, and Perfectionism
Peck, Lisa D.; Lightsey, Owen Richard
2008-01-01
Among 261 undergraduate women, increased severity of eating disorders along a continuum was associated with decreased self-esteem, increased perfectionism, and increased scores on 7 subscales of the Eating Disorders Inventory-2. Women with eating disorders differed from both symptomatic women and asymptomatic women on all variables, whereasā¦
Shouldering the blame for impingement: the rotator cuff continuum ...
African Journals Online (AJOL)
The aim of this article was to summarise recent research on shoulder impingement and rotator cuff pathology. A continuum model of rotator cuff pathology is described, and the challenges of accurate clinical diagnosis, imaging and best management discussed. Keywords: shoulder impingement syndrome, subacromialĀ ...
One millimeter continuum observations of high redshift quasars
International Nuclear Information System (INIS)
Ennis, D.J.; Soifer, B.T.
1981-01-01
Upper limits to the one-millimeter continuum flux densities of the high redshift quasars B2 1225 + 31, Ton 490, and PHL 957 are presented. The upper limit to the power observed from these quasars at 1 mm is, on the average, one half of the observed power in the continuum at L-alpha. These observations are used to constrain the temperature of a hypothetical dust shell which reddens the quasar line and continuum emission by an extinction optical depth sufficient to account for the anomalously low L-alpha/H-alpha emission line ratio observed in each of these quasars. For the quasars studied, dust shell temperatures between 25 K and 50 to 95 K are prohibited by the present data. A dust shell at a temperature within this span reradiating all the power absorbed from the quasar ultraviolet continuum would produce a one-millimeter flux density greater than the measured upper limit. The average radius of the model dust shell cannot be between 70 kpc and 1 Mpc
Nuclear structure investigations with inclusion of continuum states
International Nuclear Information System (INIS)
Rotter, I.
1983-09-01
The influence of the continuum on the properties of discrete nuclear states is reviewed. It is described on the basis of a continuum shell model. The coupling of the discrete states to the continuum results in an additional term to the Hamiltonian, commonly used in the study of nuclear structure, and an additional term to the wavefunction of the discrete state. These additional terms characterise finite nuclei in contrast to nuclear matter. They result in some symmetry violation of the residual nuclear interaction such as charge symmetry violation, and describe the nuclear surface, respectively. The energies and widths of resonance states result from the complex eigenvalues of the Hamiltonian. The partial widths are shown to be factorisable into a spectroscopic factor and into a penetration factor if the spectroscopic factor is large. An expression for the S-matrix is derived in which instead of the so-called resonance parameters, functions appear which are calculated in the framework of the model. The line shape of resonances is also influenced by these functions. As an extreme case, a resonance may have the appearance of a cusp. The conclusions drawn are supported by the results of numerical calculations performed in the continuum shell model for light nuclei with realistic shell model wavefunctions. (author)
Photon pairs: Quantum chromodynamics continuum and the Higgs ...
Indian Academy of Sciences (India)
Resummation is needed to obtain reliable predictions in the range of transverse momentum where the cross-section is the largest. Results are compared with data from the Fermilab Tevatron and predictions are made for the large hadron collider. The QCD continuum is shown to have a softer spectrum than the Higgs bosonĀ ...
Continuum limit of discrete Sommerfeld problems on square lattice
Indian Academy of Sciences (India)
BASANT LAL SHARMA
Sommerfeld half-plane; crack; rigid ribbon; continuum limit; WienerāHopf; Toeplitz ... case of which, when it approaches zero, is called 'contin- .... etc, denote constants in expressions, inequalities, etc. The ..... The latter holds on a possibly weighted space, depending ..... where jj Ų” jj refers to the corresponding operator norm.
Some aspects of continuum physics used in fuel pin modeling
International Nuclear Information System (INIS)
Bard, F.E.
1975-06-01
The mathematical formulation used in fuel pin modeling is described. Fuel pin modeling is not a simple extension of the experimental and interpretative methods used in classical mechanics. New concepts are needed to describe materials in a reactor environment. Some aspects of continuum physics used to develop these new constitutive equations for fuel pins are presented. (U.S.)
Relativistic continuum random phase approximation in spherical nuclei
Energy Technology Data Exchange (ETDEWEB)
Daoutidis, Ioannis
2009-10-01
Covariant density functional theory is used to analyze the nuclear response in the external multipole fields. The investigations are based on modern functionals with zero range and density dependent coupling constants. After a self-consistent solution of the Relativistic Mean Field (RMF) equations for the nuclear ground states multipole giant resonances are studied within the Relativistic Random Phase Approximation (RRPA), the small amplitude limit of the time-dependent RMF. The coupling to the continuum is treated precisely by calculating the single particle Greens-function of the corresponding Dirac equation. In conventional methods based on a discretization of the continuum this was not possible. The residual interaction is derived from the same RMF Lagrangian. This guarantees current conservation and a precise decoupling of the Goldstone modes. For nuclei with open shells pairing correlations are taken into account in the framework of BCS theory and relativistic quasiparticle RPA. Continuum RPA (CRPA) presents a robust method connected with an astonishing reduction of the numerical effort as compared to conventional methods. Modes of various multipolarities and isospin are investigated, in particular also the newly discovered Pygmy modes in the vicinity of the neutron evaporation threshold. The results are compared with conventional discrete RPA calculations as well as with experimental data. We find that the full treatment of the continuum is essential for light nuclei and the study of resonances in the neighborhood of the threshold. (orig.)
Cellular Automata in Topology Optimization of Continuum Structures ...
African Journals Online (AJOL)
In this paper, an optimization algorithm based on cellular automata (CA) is developed for topology optimization of continuum structures with shear and flexural behavior. The design domain is divided into small triangle elements and each cell is considered as a finite element. The stress analysis is performed by the ConstantĀ ...
Photon pairs: Quantum chromodynamics continuum and the Higgs ...
Indian Academy of Sciences (India)
is the largest. Results are compared with data from the Fermilab Tevatron and predictions are made for the large hadron collider. The QCD continuum is shown to have a softer spectrum than the Higgs boson signal at the LHC. Keywords. Higgs; photon pairs; quantum chromodynamics. PACS Nos 12.15.Ji; 12.38.Cy; 13.85.
A radio continuum and infrared study of Galactic HII regions
Martin-Hernandez, NL; van der Hulst, JM; Tielens, AGGM
We present observations of the 4.8 and 8.6 GHz continuum emission towards 11 southern H II regions made with the Australian Telescope Compact Array. The observed objects were selected from the Infrared Space Observatory (ISO) spectral catalogue of compact H II regions (Peeters et al. 2002b). The
Reverberation Mapping of the Continuum Source in Active Galactic Nuclei
Fausnaugh, Michael Martin
I present results from a monitoring campaign of 11 active galactic nuclei (AGN) conducted in Spring of 2014. I use the reverberation mapping method to probe the interior structures of the AGN, specifically the broad line regions (BLRs) and accretion disks. One of these AGN, NGC 5548, was also subject to multi-wavelength (X-ray, UV, optical, and near-IR) monitoring using 25 ground-based telescopes and four space-based facilities. For NGC 5548, I detect lags between the continuum emission at different wavelengths that follow a trend consistent with the prediction for continuum reprocessing by an accretion disk with temperature profile T ā R -3/4. However, the lags imply a disk radius that is 3 times larger than the prediction from standard thin-disk models. The lags at wavelengths longer than the Vband are also equal to or greater than the lags of high-ionization-state emission lines (such as HeII lambda1640 and lambda4686), suggesting that the continuum-emitting source is of a physical size comparable to the inner broad-line region. Using optical spectra from the Large Binocular Telescope, I estimate the bias of the interband continuum lags due to BLR emission observed in the filters, and I find that the bias for filters with high levels of BLR contamination (Ė20%) can be important for the shortest continuum lags. This likely has a significant impact on the u and U bands owing to Balmer continuum emission. I then develop a new procedure for the internal (night-to-night) calibration of time series spectra that can reach precisions of Ė1 millimagnitude and improves traditional techniques by up to a factor of 5. At this level, other systematic issues (e.g., the nightly sensitivity functions and Fe II contamination) limit the final precision of the observed light curves. Using the new calibration method, I next present the data and first results from the optical spectroscopic monitoring component of the reverberation mapping campaign. Five AGN were sufficiently
Gatti, E.; Kitchen, N.; Newman, S.; Guan, Y.; Westgate, J.; Pearce, N. J. G.; Nikolic, D.; Eiler, J. M.
2016-12-01
The hydrogen-isotope value of water of hydration (or secondary water) preserved in rhyolitic glasses may provide significant insights regarding the climate at the time of their deposition and the impact of super-eruptions upon the environment. However, the ability of the glass to retain the environmental D/H isotopic signal after hydration needs to be tested, since modifications to the D/H systematics may result from the continuous exchange of D/H with the atmosphere or condensed water after initial glass hydration. Ideal geological archives to test whether the glass retains its original hydrogen signal are sediments in natural waters and ice cores, which preserve tephra in constrained horizons that can be independently isotopically characterised. However, tephra in marine and fresh water sediments and ice cores are often present in concentrations of the order of 1000 grains/cm3 (IRMS methods require much more material ( 100-500 mg) and therefore cannot be applied. We present here a new integrated nanoSIMS and continuous flow IRMS approach to understand how water is distributed within single glass grains (diffusion profiles), quantify the time of hydration of young (Holocene) and old (Miocene) already well-characterised rhyolitic glasses, and measure the D/H ratio of the hydration water on single grains and bulk material consisting of only approximately 0.1-1 mg. The IRMS method measures the absolute abundance of hydrogen released from the sample by continuous-flow mass spectrometry. Current data indicates that the method can accurately measure a hydrogen signal from a rock sample containing at least 400 nanomoles of H2, corresponding to 70 Āµg of water, which translates to 1 mg of hydrous glass (>3 wt%) or 15 mg of dry ( 0.5 wt%) obsidian chips. The method can be improved by reducing the blank to IRMS method will be compared to sub-micron mapping of single-grains using a high-resolution ion microprobe, the CAMECA NanoSIMS 50L, in the Microanalysis Center for
International Nuclear Information System (INIS)
Kobayashi, T.; Nairn, I.; Smith, V.; Shane, P.
2005-01-01
The c. 5600 cal. yr BP Whakatane eruption episode consisted of a sequence of intracaldera rhyolite eruptions from at least five vents spread over 11 km of the Haroharo linear vent zone within Okataina Volcanic Centre. Initial vent-opening eruptions from the Haroharo vent produced coarse lithic clast 'blast beds' and pyroclastic density currents surges). These were immediately followed by eruption of very mobile pumiceous pyroclastic surges from the Makatiti vent 6 km to the southwest. Major plinian eruptions from the Makatiti vent then dispersed Whakatane Tephra pumice fall deposits (bulk volume c. 6 km 3 ) across the northeastern North Island while smaller explosive eruptions produced pyroclastic flows and falls from the Haroharo-Rotokohu vents and at the Pararoa vent on the caldera rim 11 km northeast from Makatiti. The pyroclastic eruptions at all vents were followed by the extrusion of lava flows and domes; extruded lava volumes ranged from 0.03 km 3 for the Pararoa dome to 7.5 km 3 for the Makatiti-Tapahoro lava flows and domes. Minor variations in whole rock and glass chemistry show that the three main vent areas each tapped a slightly different high-silica rhyolite magma. About 10 km 3 of M-type magma was erupted from the Makatiti-Tapahoro vents; c. 1.3 km 3 of H-type magma from the Haroharo-Rotokohu vents, and 0.04 km 3 of P-type magma from the Pararoa vent. There are no significant weathering or erosional breaks within the Whakatane eruptive sequence, which suggests that all Whakatane eruptions occurred within a short time interval. However, extrusion of the Haroharo dome within the Makatiti pyroclastic eruption sequence suggests a duration of c. 2 yr for the main pyroclastic eruption phase. Emplacement of the following voluminous (7.5 km 3 ) lavas from the Makatiti-Tapahoro vents would have occurred over >10 yr at the c. 10-20 m 3 /s inferred extrusion rates. (author). 19 refs., 16 figs., 7 tabs
Drew, Dana L.; Bindeman, Ilya N.; Watts, Kathryn E.; Schmitt, Axel K.; Fu, Bin; McCurry, Michael
2013-01-01
Rhyolites of the Picabo volcanic field (10.4ā6.6 Ma) in eastern Idaho are preserved as thick ignimbrites and lavas along the margins of the Snake River Plain (SRP), and within a deep (>3 km) borehole near the central axis of the Yellowstone hotspot track. In this study we present new O and Hf isotope data and UāPb geochronology for individual zircons, O isotope data for major phenocrysts (quartz, plagioclase, and pyroxene), whole rock Sr and Nd isotope ratios, and whole rock geochemistry for a suite of Picabo rhyolites. We synthesize our new datasets with published ArāAr geochronology to establish the eruptive framework of the Picabo volcanic field, and interpret its petrogenetic history in the context of other well-studied caldera complexes in the SRP. Caldera complex evolution at Picabo began with eruption of the 10.44Ā±0.27 Ma (UāPb) Tuff of Arbon Valley (TAV), a chemically zoned and normal-Ī“18O (Ī“18O magma=7.9ā°) unit with high, zoned 87Sr/86Sri (0.71488ā0.72520), and low-ĪµNd(0) (ā18) and ĪµHf(0) (ā28). The TAV and an associated post caldera lava flow possess the lowest ĪµNd(0) (ā23), indicating ā¼40ā60% derivation from the Archean upper crust. Normal-Ī“18O rhyolites were followed by a series of lower-Ī“18O eruptions with more typical (lower crustal) SrāNdāHf isotope ratios and whole rock chemistry. The voluminous 8.25Ā±0.26 Ma West Pocatello rhyolite has the lowest Ī“18O value (Ī“18Omelt=3.3ā°), and we correlate it to a 1,000 m thick intracaldera tuff present in the INEL-1 borehole (with published zircon ages 8.04ā8.35 Ma, and similarly low-Ī“18O zircon values). The significant (4ā5ā°) decrease in magmatic-Ī“18O values in Picabo rhyolites is accompanied by an increase in zircon Ī“18O heterogeneity from ā¼1ā° variation in the TAV to >5ā° variation in the late-stage low-Ī“18O rhyolites, a trend similar to what is characteristic of Heise and Yellowstone, and which indicates remelting of variably hydrothermally altered tuffs
Energy Technology Data Exchange (ETDEWEB)
Haneke, J; Gaede, C W [Gewerkschaft Brunhilde, Uetze (Germany, F.R.); Lorenz, V [Mainz Univ. (Germany, F.R.). Inst. fuer Geowissenschaften
1979-01-01
The lithostratigraphic sequence of the Upper Rotliegende rocks of the SE-flank of the Palatinate anticline (Saar-Nahe-basin, SW Germany) is described using as index horizons six principal rhyolitic tuff layers (1-VI) and several basic to intermediate lava flows. Coal and bentonite beds are developed at the base of rhyolite tuff III at the Kornkiste near Schallodenbach. In this basal sequence anomalous U/sub 3/O/sub 8/, Cu, Pb, Zn contents have been detected. Cu occurs in part as azurite and malachite. The major amount of the investigated elements appears to occur in form of organic complexes or compounds in the coals. In addition these elements seem to have been absorbed by the bentonite clay minerals. The elements U, Cu, Pb show a clear positive correlation between each other wheres Zn correlators negatively with these elements. The U-Cu-Pb-Zn-enrichment is believed to have been caused by descending aqueous solutions.
International Nuclear Information System (INIS)
Haneke, J.; Gaede, C.W.; Lorenz, V.
1979-01-01
The lithostratigraphic sequence of the Upper Rotliegende rocks of the SE-flank of the Palatinate anticline (Saar-Nahe-basin, SW Germany) is described using as index horizons six principal rhyolitic tuff layers (1-VI) and several basic to intermediate lava flows. Coal and bentonite beds are developed at the base of rhyolite tuff III at the Kornkiste near Schallodenbach. In this basal sequence anomalous U 3 O 8 , Cu, Pb, Zn contents have been detected. Cu occurs in part as azurite and malachite. The major amount of the investigated elements appears to occur in form of organic complexes or compounds in the coals. In addition these elements seem to have been absorbed by the bentonite clay minerals. The elements U, Cu, Pb show a clear positive correlation between each other wheres Zn correlators negatively with these elements. The U-Cu-Pb-Zn-enrichment is believed to have been caused by descending aqueous solutions. (orig.) [de
Blanco, Celia; RibĆ³, Josep M; Hochberg, David
2015-02-01
We derive the class of population balance equations (PBE), recently applied to model the Viedma deracemization experiment, from an underlying microreversible kinetic reaction scheme. The continuum limit establishing the relationship between the micro- and macroscopic processes and the associated particle fluxes erases the microreversible nature of the molecular interactions in the population growth rate functions and limits the scope of such PBE models to strict kinetic control. The irreversible binary agglomeration processes modeled in those PBEs contribute an additional source of kinetic control. These limitations are crucial regarding the question of the origin of biological homochirality, where the interest in any model lies precisely in its ability for absolute asymmetric synthesis and the amplification of the tiny inherent statistical chiral fluctuations about the ideal racemic composition up to observable enantiometric excess levels.
DEFF Research Database (Denmark)
Rivera, Tiffany; Storey, Michael; Schmitz, M. D.
2013-01-01
, and have less pronounced positive Ce and negative Eu anomalies, lower incompatible trace element contents, higher TiZR temperatures that range up to 840 Ā°C, and significantly younger dates. The youngest Group A dates yield a weighted mean of 1.1978 Ā± 0.0046 Ma (2Ļ, including systematic uncertainties...... with the astronomical age estimate for the Cobb Mountain subchron determined by correlating the oxygen isotope record of the giant piston core MD972143 to the La93(1,1) orbital solution. On the basis of independent radio-isotopic and orbital forcing results, we propose the refined age of 1.1850 Ā± 0.0016 Ma (2Ļ external......We report results from a 40Ar/39Ar sanidine and CA-TIMS 238U/206Pb zircon dating study of eruption and crystal residence timescales of the Alder Creek Rhyolite (ACR), California, extruded during the Cobb Mountain normal-polarity subchron (C1r.2n). A 40Ar/39Ar ACR sanidine date of 1.1850 Ā± 0.0016 Ma...
2012-07-31
... which service providers are familiar. The following highlights key definitions used in the Continuum of... Continuum of Care in 1995. Local grantees and stakeholders are familiar with the Continuum of Care as the... violence, dating violence, sexual assault, and stalking. In developing the baseline requirements for a...
Antieigenvalue analysis for continuum mechanics, economics, and number theory
Directory of Open Access Journals (Sweden)
Gustafson Karl
2016-01-01
Full Text Available My recent book Antieigenvalue Analysis, World-Scientific, 2012, presented the theory of antieigenvalues from its inception in 1966 up to 2010, and its applications within those forty-five years to Numerical Analysis, Wavelets, Statistics, Quantum Mechanics, Finance, and Optimization. Here I am able to offer three further areas of application: Continuum Mechanics, Economics, and Number Theory. In particular, the critical angle of repose in a continuum model of granular materials is shown to be exactly my matrix maximum turning angle of the stress tensor of the material. The important Sharpe ratio of the Capital Asset Pricing Model is now seen in terms of my antieigenvalue theory. Euclidās Formula for Pythagorean triples becomes a special case of my operator trigonometry.
Topology and layout optimization of discrete and continuum structures
Bendsoe, Martin P.; Kikuchi, Noboru
1993-01-01
The basic features of the ground structure method for truss structure an continuum problems are described. Problems with a large number of potential structural elements are considered using the compliance of the structure as the objective function. The design problem is the minimization of compliance for a given structural weight, and the design variables for truss problems are the cross-sectional areas of the individual truss members, while for continuum problems they are the variable densities of material in each of the elements of the FEM discretization. It is shown how homogenization theory can be applied to provide a relation between material density and the effective material properties of a periodic medium with a known microstructure of material and voids.
Three-body continuum states on a Lagrange mesh
International Nuclear Information System (INIS)
Descouvemont, P.; Tursunov, E.; Baye, D.
2006-01-01
Three-body continuum states are investigated with the hyperspherical method on a Lagrange mesh. The R-matrix theory is used to treat the asymptotic behaviour of scattering wave functions. The formalism is developed for neutral as well as for charged systems. We point out some specificities of continuum states in the hyperspherical method. The collision matrix can be determined with a good accuracy by using propagation techniques. The method is applied to the 6 He (=Ī±+n+n) and 6 Be (=Ī±+p+p) systems, as well as to 14 Be (=Be12+n+n). For 6 He, we essentially recover results of the literature. Application to 14 Be suggests the existence of an excited 2 + state below threshold. The calculated B(E2) value should make this state observable with Coulomb excitation experiments
Continuum modelling for carbon and boron nitride nanostructures
International Nuclear Information System (INIS)
Thamwattana, Ngamta; Hill, James M
2007-01-01
Continuum based models are presented here for certain boron nitride and carbon nanostructures. In particular, certain fullerene interactions, C 60 -C 60 , B 36 N 36 -B 36 N 36 and C 60 -B 36 N 36 , and fullerene-nanotube oscillator interactions, C 60 -boron nitride nanotube, C 60 -carbon nanotube, B 36 N 36 -boron nitride nanotube and B 36 N 36 -carbon nanotube, are studied using the Lennard-Jones potential and the continuum approach, which assumes a uniform distribution of atoms on the surface of each molecule. Issues regarding the encapsulation of a fullerene into a nanotube are also addressed, including acceptance and suction energies of the fullerenes, preferred position of the fullerenes inside the nanotube and the gigahertz frequency oscillation of the inner molecule inside the outer nanotube. Our primary purpose here is to extend a number of established results for carbon to the boron nitride nanostructures
Continuum-mediated dark matterābaryon scattering
Katz, Andrey; Sajjad, Aqil
2016-01-01
Many models of dark matter scattering with baryons may be treated either as a simple contact interaction or as the exchange of a light mediator particle. We study an alternative, in which a continuum of light mediator states may be exchanged. This could arise, for instance, from coupling to a sector which is approximately conformal at the relevant momentum transfer scale. In the non-relativistic effective theory of dark matter-baryon scattering, which is useful for parametrizing direct detection signals, the effect of such continuum mediators is to multiply the amplitude by a function of the momentum transfer q, which in the simplest case is just a power law. We develop the basic framework and study two examples: the case where the mediator is a scalar operator coupling to the Higgs portal (which turns out to be highly constrained) and the case of an antisymmetric tensor operator ${\\cal O}_{\\mu \
Derivation of Electromagnetism from the Elastodynamics of the Spacetime Continuum
Directory of Open Access Journals (Sweden)
Millette P. A.
2013-04-01
Full Text Available We derive Electromagnetism from the Elastodynamics of the Spacetime Continuum based on the identification of the theoryās antisymmetric rotation tensor with the elec- tromagnetic field-strength tensor. The theory provides a physical explanation of the electromagnetic potential, which arises from transverse ( shearing displacements of the spacetime continuum, in contrast to mass which arises from longitudinal (dilatational displacements. In addition, the theory provides a physical explanation of the current density four-vector, as the 4-gradient of the volume dilatation of the spacetime con- tinuum. The Lorentz condition is obtained directly from the theory. In addition, we obtain a generalization of Electromagnetism for the situation where a volume force is present, in the general non-macroscopic case. Maxwellās equations are found to remain unchanged, but the current density has an additional term proportional to the volume force.
PCE: web tools to compute protein continuum electrostatics
Miteva, Maria A.; TuffĆ©ry, Pierre; Villoutreix, Bruno O.
2005-01-01
PCE (protein continuum electrostatics) is an online service for protein electrostatic computations presently based on the MEAD (macroscopic electrostatics with atomic detail) package initially developed by D. Bashford [(2004) Front Biosci., 9, 1082ā1099]. This computer method uses a macroscopic electrostatic model for the calculation of protein electrostatic properties, such as pKa values of titratable groups and electrostatic potentials. The MEAD package generates electrostatic energies via finite difference solution to the PoissonāBoltzmann equation. Users submit a PDB file and PCE returns potentials and pKa values as well as color (static or animated) figures displaying electrostatic potentials mapped on the molecular surface. This service is intended to facilitate electrostatics analyses of proteins and thereby broaden the accessibility to continuum electrostatics to the biological community. PCE can be accessed at . PMID:15980492
Global spiral structure of M81 - radio continuum maps
International Nuclear Information System (INIS)
Bash, F.N.; Kaufman, M.; Ohio State Univ., Columbus)
1986-01-01
VLA observations of the radio continuum emission from M81 at 6 and 20 cm are presented and used to check the predictions of density-wave theories. Both thermal and nonthermal radiation from the spiral arms are detected. Most of the bright knots along the radio arms are giant radio H II regions. The nonthermal emission defines spiral arms that are patchy and well-resolved, with a width of 1-2 kpc. The observed nonthermal arms are too broad to agree with the continuum gasdynamical calculations of Roberts (1969), Shu et al. (1972), and Visser (1978, 1980) for a classical density wave model. The observed arm widths appear consistent with the predictions of density-wave models that emphasize the clumpy nature of the ISM. The 20 cm arms appear to spiral outward from a faint inner H I ring, suggesting that the ring is produced by the inner Lindblad resonance. 36 references
Continuum effects in the scattering of exotic nuclei
Energy Technology Data Exchange (ETDEWEB)
Druet, T. [Universite Libre de Bruxelles (ULB), Physique Quantique, C.P. 165/82, Brussels (Belgium); Universite Libre de Bruxelles (ULB), Physique Nucleaire Theorique et Physique Mathematique, Brussels (Belgium); Descouvemont, P. [Universite Libre de Bruxelles (ULB), Physique Nucleaire Theorique et Physique Mathematique, Brussels (Belgium)
2012-10-15
We discuss continuum effects in the scattering of exotic nuclei, and more specifically on the {sup 11}Be + {sup 64}Zn scattering. {sup 11}Be is a typical example of an exotic nucleus, with a low binding energy. Elastic, inelastic and breakup cross-sections of the {sup 11}Be + {sup 64}Zn system are computed in the Continuum Discretized Coupled Channel formalism, at energies near the Coulomb barrier. We show that converged cross-sections need high angular momenta as well as as large excitation energies in the wave functions of the projectile. Extensions to other systems are simulated by different collision energies, and by varying the binding energy of {sup 11}Be. (orig.)
Continuum mechanical and computational aspects of material behavior
Energy Technology Data Exchange (ETDEWEB)
Fried, Eliot; Gurtin, Morton E.
2000-02-10
The focus of the work is the application of continuum mechanics to materials science, specifically to the macroscopic characterization of material behavior at small length scales. The long-term goals are a continuum-mechanical framework for the study of materials that provides a basis for general theories and leads to boundary-value problems of physical relevance, and computational methods appropriate to these problems supplemented by physically meaningful regularizations to aid in their solution. Specific studies include the following: the development of a theory of polycrystalline plasticity that incorporates free energy associated with lattice mismatch between grains; the development of a theory of geometrically necessary dislocations within the context of finite-strain plasticity; the development of a gradient theory for single-crystal plasticity with geometrically necessary dislocations; simulations of dynamical fracture using a theory that allows for the kinking and branching of cracks; computation of segregation and compaction in flowing granular materials.
The Glymphatic-Lymphatic Continuum: Opportunities for Osteopathic Manipulative Medicine.
Hitscherich, Kyle; Smith, Kyle; Cuoco, Joshua A; Ruvolo, Kathryn E; Mancini, Jayme D; Leheste, Joerg R; Torres, German
2016-03-01
The brain has long been thought to lack a lymphatic drainage system. Recent studies, however, show the presence of a brain-wide paravascular system appropriately named the glymphatic system based on its similarity to the lymphatic system in function and its dependence on astroglial water flux. Besides the clearance of cerebrospinal fluid and interstitial fluid, the glymphatic system also facilitates the clearance of interstitial solutes such as amyloid-Ī² and tau from the brain. As cerebrospinal fluid and interstitial fluid are cleared through the glymphatic system, eventually draining into the lymphatic vessels of the neck, this continuous fluid circuit offers a paradigm shift in osteopathic manipulative medicine. For instance, manipulation of the glymphatic-lymphatic continuum could be used to promote experimental initiatives for nonpharmacologic, noninvasive management of neurologic disorders. In the present review, the authors describe what is known about the glymphatic system and identify several osteopathic experimental strategies rooted in a mechanistic understanding of the glymphatic-lymphatic continuum.
Non compact continuum limit of two coupled Potts models
International Nuclear Information System (INIS)
Vernier, Ćric; Jacobsen, Jesper Lykke; Saleur, Hubert
2014-01-01
We study two Q-state Potts models coupled by the product of their energy operators, in the regime 2Ā 3 (2) vertex model. It corresponds to a selfdual system of two antiferromagnetic Potts models, coupled ferromagnetically. We derive the Bethe ansatz equations and study them numerically for two arbitrary twist angles. The continuum limit is shown to involve two compact bosons and one non compact boson, with discrete states emerging from the continuum at appropriate twists. The non compact boson entails strong logarithmic corrections to the finite-size behaviour of the scaling levels, an understanding of which allows us to correct an earlier proposal for some of the critical exponents. In particular, we infer the full set of magnetic scaling dimensions (watermelon operators) of the Potts model. (paper)
Elucidating a Goal-Setting Continuum in Brain Injury Rehabilitation.
Hunt, Anne W; Le Dorze, Guylaine; Trentham, Barry; Polatajko, Helene J; Dawson, Deirdre R
2015-08-01
For individuals with brain injury, active participation in goal setting is associated with better rehabilitation outcomes. However, clinicians report difficulty engaging these clients in goal setting due to perceived or real deficits (e.g., lack of awareness). We conducted a study using grounded theory methods to understand how clinicians from occupational therapy facilitate client engagement and manage challenges inherent in goal setting with this population. Through constant comparative analysis, a goal-setting continuum emerged. At one end of the continuum, therapists embrace client-determined goals and enable clients to decide their own goals. At the other, therapists accept preset organization-determined goals (e.g., "the goal is discharge") and pay little attention to client input. Although all participants aspired to embrace client-determined goal setting, most felt powerless to do so within perceived organizational constraints. Views of advocacy and empowerment help to explain our findings and inform more inclusive practice. Ā© The Author(s) 2015.
Radio continuum emission from young stellar objects in L1641
International Nuclear Information System (INIS)
Morgan, J.A.; Snell, R.L.; Strom, K.M.
1990-01-01
The results of a 6 and 20 cm radio continuum survey of young stellar objects in the L1641 region located south of the Orion Nebula are presented. Four are identified as low-luminosity young stellar objects in L1641 and three more as Herbig-Haro or Herbig-Haro-like objects. These objects have bolometric luminosities between 80 and 300 solar, and their 6-20 cm spectral index suggests optically thick, free-free emission. They are characterized by a rising spectrum between 2.2 and 25 microns, have no optical counterparts, and are associated with stellar wind activity. Thus, detectable radio continuum emission may be produced only by the youngest and most luminous objects in L1641. 34 refs
Plastic dislocation motion via nonequilibrium molecular and continuum dynamics
International Nuclear Information System (INIS)
Hoover, W.G.; Ladd, A.J.C.; Hoover, N.E.
1980-01-01
The classical two-dimensional close-packed triangular lattice, with nearest-neighbor spring forces, is a convenient standard material for the investigation of dislocation motion and plastic flow. Two kinds of calculations, based on this standard material, are described here: (1) Molecular Dynamics simulations, incorporating adiabatic strains described with the help of Doll's Tensor, and (2) Continuum Dynamics simulations, incorporating periodic boundaries and dislocation interaction through stress-field superposition
Haro 11: Where is the Lyman Continuum Source?
Energy Technology Data Exchange (ETDEWEB)
Keenan, Ryan P.; Oey, M. S. [Department of Astronomy, University of Michigan, 1085 South University Avenue, Ann Arbor, MI 48109 (United States); Jaskot, Anne E. [Department of Astronomy, Smith College, Northampton, MA 01063 (United States); James, Bethan L. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
2017-10-10
Identifying the mechanism by which high-energy Lyman continuum (LyC) photons escaped from early galaxies is one of the most pressing questions in cosmic evolution. Haro 11 is the best known local LyC-leaking galaxy, providing an important opportunity to test our understanding of LyC escape. The observed LyC emission in this galaxy presumably originates from one of the three bright, photoionizing knots known as A, B, and C. It is known that Knot C has strong Ly Ī± emission, and Knot B hosts an unusually bright ultraluminous X-ray source, which may be a low-luminosity active galactic nucleus. To clarify the LyC source, we carry out ionization-parameter mapping (IPM) by obtaining narrow-band imaging from the Hubble Space Telescope WFC3 and ACS cameras to construct spatially resolved ratio maps of [O iii]/[O ii] emission from the galaxy. IPM traces the ionization structure of the interstellar medium and allows us to identify optically thin regions. To optimize the continuum subtraction, we introduce a new method for determining the best continuum scale factor derived from the mode of the continuum-subtracted, image flux distribution. We find no conclusive evidence of LyC escape from Knots B or C, but instead we identify a high-ionization region extending over at least 1 kpc from Knot A. This knot shows evidence of an extremely young age (ā²1 Myr), perhaps containing very massive stars (>100 M {sub ā}). It is weak in Ly Ī± , so if it is confirmed as the LyC source, our results imply that LyC emission may be independent of Ly Ī± emission.
Continuum-limit scaling of overlap fermions as valence quarks
International Nuclear Information System (INIS)
Cichy, Krzysztof; Herdoiza, Gregorio; Jansen, Karl
2009-10-01
We present the results of a mixed action approach, employing dynamical twisted mass fermions in the sea sector and overlap valence fermions, with the aim of testing the continuum limit scaling behaviour of physical quantities, taking the pion decay constant as an example. To render the computations practical, we impose for this purpose a fixed finite volume with lattice size Lā¼1.3 fm. We also briefly review the techniques we have used to deal with overlap fermions. (orig.)
Continuum symmetry restoration in lattice models with staggered fermions
International Nuclear Information System (INIS)
Morel, A.
1986-09-01
This talk is a report on results obtained by T. Jolicoeur, R. Lacaze, B. Petersson and the author: staggered fermions can be consistently interpreted as flavoured quarks in the continuum limit of asymptotically free theories on the lattice. This statement is supported by analytical results for the Gross-Neveu model at large N and for a QCD two point function, and by a numerical simulation of SU(2) quenched QCD
Large mass limit of the continuum theories in Kaplan's formulation
International Nuclear Information System (INIS)
Kawano, T.; Kikukawa, Y.
1994-01-01
Being inspired by Kaplan's proposal for simulating chiral fermions on a lattice, we examine the continuum analogue of his domain-wall construction for two-dimensional chiral Schwinger models. Adopting a slightly unusual dimensional regularization, we explicitly evaluate the one-loop effective action in the limit that the domain-wall mass goes to infinity. For anomaly-free cases, the effective action turns out to be gauge invariant in the two-dimensional sense
Perturbative matching of continuum and lattice quasi-distributions
Directory of Open Access Journals (Sweden)
Ishikawa Tomomi
2018-01-01
Full Text Available Matching of the quasi parton distribution functions between continuum and lattice is addressed using lattice perturbation theory specifically withWilson-type fermions. The matching is done for nonlocal quark bilinear operators with a straightWilson line in a spatial direction. We also investigate operator mixing in the renormalization and possible O(a operators for the nonlocal operators based on a symmetry argument on lattice.
Constitutive relationships and models in continuum theories of multiphase flows
International Nuclear Information System (INIS)
Decker, R.
1989-09-01
In April, 1989, a workshop on constitutive relationships and models in continuum theories of multiphase flows was held at NASA's Marshall Space Flight Center. Topics of constitutive relationships for the partial or per phase stresses, including the concept of solid phase pressure are discussed. Models used for the exchange of mass, momentum, and energy between the phases in a multiphase flow are also discussed. The program, abstracts, and texts of the presentations from the workshop are included
New numerical methods for quantum field theories on the continuum
Energy Technology Data Exchange (ETDEWEB)
Emirdag, P.; Easter, R.; Guralnik, G.S.; Hahn, S.C
2000-03-01
The Source Galerkin Method is a new numerical technique that is being developed to solve Quantum Field Theories on the continuum. It is not based on Monte Carlo techniques and has a measure to evaluate relative errors. It promises to increase the accuracy and speed of calculations, and takes full advantage of symmetries of the theory. The application of this method to the non-linear {sigma} model is outlined.
Properties of warm nuclei in the quasi-continuum
Directory of Open Access Journals (Sweden)
Voinov A.
2010-03-01
Full Text Available Nuclear thermodynamic quantities are extracted from nuclear level densities measured with the CACTUS detector array at the Oslo Cyclotron Laboratory. The experiments are performed with light-particle inelastic or transfer reactions. A simple combinatorial model is used to describe the underlying mechanisms responsible for the exponential increasing level density as function of excitation energy. The calculated number of broken Cooper pairs and the parity distribution in continuum are discussed.
A Geometry Deformation Model for Braided Continuum Manipulators
Directory of Open Access Journals (Sweden)
S. M. Hadi Sadati
2017-06-01
Full Text Available Continuum manipulators have gained significant attention in the robotic community due to their high dexterity, deformability, and reachability. Modeling of such manipulators has been shown to be very complex and challenging. Despite many research attempts, a general and comprehensive modeling method is yet to be established. In this paper, for the first time, we introduce the bending effect in the model of a braided extensile pneumatic actuator with both stiff and bendable threads. Then, the effect of the manipulator cross-section deformation on the constant curvature and variable curvature models is investigated using simple analytical results from a novel geometry deformation method and is compared to experimental results. We achieve 38% mean reference error simulation accuracy using our constant curvature model for a braided continuum manipulator in presence of body load and 10% using our variable curvature model in presence of extensive external loads. With proper model assumptions and taking to account the cross-section deformation, a 7ā13% increase in the simulation mean error accuracy is achieved compared to a fixed cross-section model. The presented models can be used for the exact modeling and design optimization of compound continuum manipulators by providing an analytical tool for the sensitivity analysis of the manipulator performance. Our main aim is the application in minimal invasive manipulation with limited workspaces and manipulators with regional tunable stiffness in their cross section.
The quantum and the continuum : Einstein's dichotomous legacies
International Nuclear Information System (INIS)
Majumdar, Parthasarathi
2015-01-01
This talk begins with a summary of some of Einstein's seminal contributions in the quantum domain, like Brownian motion and the Light Quantum Hypothesis, as well as on the spacetime continuum enshrined in the theories of special and general relativity. Following up on Einstein's rationale for postulating the Light Quantum Hypothesis, we attempt to point to a possible dichotomy in his thinking about these two legacies of his, which may have been noticed by him, but was not much discussed by him in the public domain. One may speculate that this may have had something to do with his well-known distaste for the probability interpretation of quantum mechanics as a fundamental interpretation. We argue that Einstein's general relativity theory itself contains the seeds of a dramatic modification of our ideas of the Einsteinian spacetime continuum, thus underlining the dichotomy even more strongly. We then survey one modern attempt to resolve the dichotomy, at least partly, by bringing into the spacetime continuum, aspects of quantum mechanics with its underlying statistical interpretation, an approach which Einstein may not have whole-heartedly endorsed, but which seems to work so far, with good prospects for the future. (author)
Variational principles of continuum mechanics. Vol. 1. Fundamentals
Energy Technology Data Exchange (ETDEWEB)
Berdichevsky, Victor L. [Wayne State Univ., Detroit, MI (United States). Dept. of Mechanical Engineering
2009-07-01
The book reviews the two features of the variational approach: its use as a universal tool to describe physical phenomena and as a source for qualitative and quantitative methods of studying particular problems. Berdichevsky's work differs from other books on the subject in focusing mostly on the physical origin of variational principles as well as establishing their interrelations. For example, the Gibbs principles appear as a consequence of the Einstein formula for thermodynamic fluctuations rather than as the first principles of the theory of thermodynamic equilibrium. Mathematical issues are considered as long as they shed light on the physical outcomes and/or provide a useful technique for the direct study of variational problems. In addition, a thorough account of variational principles discovered in various branches of continuum mechanics is given. In this book, the first volume, the author covers the variational principles for systems with a finite number of degrees of freedom; the variational principles of thermodynamics; the basics of continuum mechanics; the variational principles for classical models of continuum mechanics, such as elastic and plastic bodies, and ideal and viscous fluids; and direct methods of calculus of variations. (orig.)
Identification of a transcriptional signature for the wound healing continuum
Peake, Matthew A; Caley, Mathew; Giles, Peter J; Wall, Ivan; Enoch, Stuart; Davies, Lindsay C; Kipling, David; Thomas, David W; Stephens, Phil
2014-01-01
There is a spectrum/continuum of adult human wound healing outcomes ranging from the enhanced (nearly scarless) healing observed in oral mucosa to scarring within skin and the nonhealing of chronic skin wounds. Central to these outcomes is the role of the fibroblast. Global gene expression profiling utilizing microarrays is starting to give insight into the role of such cells during the healing process, but no studies to date have produced a gene signature for this wound healing continuum. Microarray analysis of adult oral mucosal fibroblast (OMF), normal skin fibroblast (NF), and chronic wound fibroblast (CWF) at 0 and 6 hours post-serum stimulation was performed. Genes whose expression increases following serum exposure in the order OMF healing phenotype (the dysfunctional healing group), whereas genes with the converse pattern are potentially associated with a positive/preferential healing phenotype (the enhanced healing group). Sixty-six genes in the enhanced healing group and 38 genes in the dysfunctional healing group were identified. Overrepresentation analysis revealed pathways directly and indirectly associated with wound healing and aging and additional categories associated with differentiation, development, and morphogenesis. Knowledge of this wound healing continuum gene signature may in turn assist in the therapeutic assessment/treatment of a patient's wounds. PMID:24844339
Additive manufacturing of patient-specific tubular continuum manipulators
Amanov, Ernar; Nguyen, Thien-Dang; Burgner-Kahrs, Jessica
2015-03-01
Tubular continuum robots, which are composed of multiple concentric, precurved, elastic tubes, provide more dexterity than traditional surgical instruments at the same diameter. The tubes can be precurved such that the resulting manipulator fulfills surgical task requirements. Up to now the only material used for the component tubes of those manipulators is NiTi, a super-elastic shape-memory alloy of nickel and titan. NiTi is a cost-intensive material and fabrication processes are complex, requiring (proprietary) technology, e.g. for shape setting. In this paper, we evaluate component tubes made of 3 different thermoplastic materials (PLA, PCL and nylon) using fused filament fabrication technology (3D printing). This enables quick and cost-effective production of custom, patient-specific continuum manipulators, produced on site on demand. Stress-strain and deformation characteristics are evaluated experimentally for 16 fabricated tubes of each thermoplastic with diameters and shapes equivalent to those of NiTi tubes. Tubes made of PCL and nylon exhibit properties comparable to those made of NiTi. We further demonstrate a tubular continuum manipulator composed of 3 nylon tubes in a transnasal, transsphenoidal skull base surgery scenario in vitro.
Spatial stochasticity and non-continuum effects in gas flows
Energy Technology Data Exchange (ETDEWEB)
Dadzie, S. Kokou, E-mail: k.dadzie@glyndwr.ac.uk [Mechanical and Aeronautical Engineering, Glyndwr University, Mold Road, Wrexham LL11 2AW (United Kingdom); Reese, Jason M., E-mail: jason.reese@strath.ac.uk [Department of Mechanical and Aerospace Engineering, University of Strathclyde, Glasgow G1 1XJ (United Kingdom)
2012-02-06
We investigate the relationship between spatial stochasticity and non-continuum effects in gas flows. A kinetic model for a dilute gas is developed using strictly a stochastic molecular model reasoning, without primarily referring to either the Liouville or the Boltzmann equations for dilute gases. The kinetic equation, a stochastic version of the well-known deterministic Boltzmann equation for dilute gas, is then associated with a set of macroscopic equations for the case of a monatomic gas. Tests based on a heat conduction configuration and sound wave dispersion show that spatial stochasticity can explain some non-continuum effects seen in gases. -- Highlights: āŗ We investigate effects of molecular spatial stochasticity in non-continuum regime. āŗ Present a simplify spatial stochastic kinetic equation. āŗ Present a spatial stochastic macroscopic flow equations. āŗ Show effects of the new model on sound wave dispersion prediction. āŗ Show effects of the new approach in density profiles in a heat conduction.
Continuum-Kinetic Models and Numerical Methods for Multiphase Applications
Nault, Isaac Michael
This thesis presents a continuum-kinetic approach for modeling general problems in multiphase solid mechanics. In this context, a continuum model refers to any model, typically on the macro-scale, in which continuous state variables are used to capture the most important physics: conservation of mass, momentum, and energy. A kinetic model refers to any model, typically on the meso-scale, which captures the statistical motion and evolution of microscopic entitites. Multiphase phenomena usually involve non-negligible micro or meso-scopic effects at the interfaces between phases. The approach developed in the thesis attempts to combine the computational performance benefits of a continuum model with the physical accuracy of a kinetic model when applied to a multiphase problem. The approach is applied to modeling a single particle impact in Cold Spray, an engineering process that intimately involves the interaction of crystal grains with high-magnitude elastic waves. Such a situation could be classified a multiphase application due to the discrete nature of grains on the spatial scale of the problem. For this application, a hyper elasto-plastic model is solved by a finite volume method with approximate Riemann solver. The results of this model are compared for two types of plastic closure: a phenomenological macro-scale constitutive law, and a physics-based meso-scale Crystal Plasticity model.
YM2: Continuum expectations, lattice convergence, and lassos
International Nuclear Information System (INIS)
Driver, B.K.
1989-01-01
The two dimensional Yang-Mills theory (YM 2 ) is analyzed in both the continuum and the lattice. In the complete axial gauge the continuum theory may be defined in terms of a Lie algebra valued white noise, and parallel translation may be defined by stochastic differential equations. This machinery is used to compute the expectations of gauge invariant functions of the parallel translation operators along a collection of curves C. The expectation values are expressed as finite dimensional integrals with densities that are products of the heat kernel on the structure group. The time parameters of the heat kernels are determined by the areas enclosed by the collection C, and the arguments are determined by the crossing topologies of the curves in C. The expectations for the Wilson lattice models have a similar structure, and from this it follows that in the limit of small lattice spacing the lattice expectations converge to the continuum expectations. It is also shown that the lasso variables advocated by L. Gross exist and are sufficient to generate all the measurable functions on the YM 2 -measure space. (orig.)
Criminal justice continuum for opioid users at risk of overdose.
Brinkley-Rubinstein, Lauren; Zaller, Nickolas; Martino, Sarah; Cloud, David H; McCauley, Erin; Heise, Andrew; Seal, David
2018-02-24
The United States (US) is in the midst of an epidemic of opioid use; however, overdose mortality disproportionately affects certain subgroups. For example, more than half of state prisoners and approximately two-thirds of county jail detainees report issues with substance use. Overdose is one of the leading causes of mortality among individuals released from correctional settings. Even though the criminal justice (CJ) system interacts with a disproportionately high number of individuals at risk of opioid use and overdose, few CJ agencies screen for opioid use disorder (OUD). Even less provide access to medication assisted treatment (e.g. methadone, buprenorphine, and depot naltrexone), which is one of the most effective tools to combat addiction and lower overdose risk. However, there is an opportunity to implement programs across the CJ continuum in collaboration with law enforcement, courts, correctional facilities, community service providers, and probation and parole. In the current paper, we introduce the concept of a "CJ Continuum of Care for Opioid Users at Risk of Overdose", grounded by the Sequential Intercept Model. We present each step on the CJ Continuum and include a general overview and highlight opportunities for: 1) screening for OUD and overdose risk, 2) treatment and/or diversion, and 3) overdose prevention and naloxone provision. Copyright Ā© 2018 Elsevier Ltd. All rights reserved.
Identification of a transcriptional signature for the wound healing continuum.
Peake, Matthew A; Caley, Mathew; Giles, Peter J; Wall, Ivan; Enoch, Stuart; Davies, Lindsay C; Kipling, David; Thomas, David W; Stephens, Phil
2014-01-01
There is a spectrum/continuum of adult human wound healing outcomes ranging from the enhanced (nearly scarless) healing observed in oral mucosa to scarring within skin and the nonhealing of chronic skin wounds. Central to these outcomes is the role of the fibroblast. Global gene expression profiling utilizing microarrays is starting to give insight into the role of such cells during the healing process, but no studies to date have produced a gene signature for this wound healing continuum. Microarray analysis of adult oral mucosal fibroblast (OMF), normal skin fibroblast (NF), and chronic wound fibroblast (CWF) at 0 and 6 hours post-serum stimulation was performed. Genes whose expression increases following serum exposure in the order OMFāhealing phenotype (the dysfunctional healing group), whereas genes with the converse pattern are potentially associated with a positive/preferential healing phenotype (the enhanced healing group). Sixty-six genes in the enhanced healing group and 38 genes in the dysfunctional healing group were identified. Overrepresentation analysis revealed pathways directly and indirectly associated with wound healing and aging and additional categories associated with differentiation, development, and morphogenesis. Knowledge of this wound healing continuum gene signature may in turn assist in the therapeutic assessment/treatment of a patient's wounds. Ā© 2014 The Authors. Wound Repair and Regeneration published by Wiley Periodicals, Inc. on behalf of Wound Healing Society.
Compositeness condition in the renormalization group equation
International Nuclear Information System (INIS)
Bando, Masako; Kugo, Taichiro; Maekawa, Nobuhiro; Sasakura, Naoki; Watabiki, Yoshiyuki; Suehiro, Kazuhiko
1990-01-01
The problems in imposing compositeness conditions as boundary conditions in renormalization group equations are discussed. It is pointed out that one has to use the renormalization group equation directly in cutoff theory. In some cases, however, it can be approximated by the renormalization group equation in continuum theory if the mass dependent renormalization scheme is adopted. (orig.)
Map of fluid flow in fractal porous medium into fractal continuum flow.
Balankin, Alexander S; Elizarraraz, Benjamin Espinoza
2012-05-01
This paper is devoted to fractal continuum hydrodynamics and its application to model fluid flows in fractally permeable reservoirs. Hydrodynamics of fractal continuum flow is developed on the basis of a self-consistent model of fractal continuum employing vector local fractional differential operators allied with the Hausdorff derivative. The generalized forms of Green-Gauss and Kelvin-Stokes theorems for fractional calculus are proved. The Hausdorff material derivative is defined and the form of Reynolds transport theorem for fractal continuum flow is obtained. The fundamental conservation laws for a fractal continuum flow are established. The Stokes law and the analog of Darcy's law for fractal continuum flow are suggested. The pressure-transient equation accounting the fractal metric of fractal continuum flow is derived. The generalization of the pressure-transient equation accounting the fractal topology of fractal continuum flow is proposed. The mapping of fluid flow in a fractally permeable medium into a fractal continuum flow is discussed. It is stated that the spectral dimension of the fractal continuum flow d(s) is equal to its mass fractal dimension D, even when the spectral dimension of the fractally porous or fissured medium is less than D. A comparison of the fractal continuum flow approach with other models of fluid flow in fractally permeable media and the experimental field data for reservoir tests are provided.
International Nuclear Information System (INIS)
Pimentel, M.M.; Heaman, L.; Fuck, R.A.
1992-01-01
U-Pb isotopic analyses in eight zircon fractions separated from a meta-rhyolite sample of the Marata sequence (Araxa Group, Goias) are presented. Two morphologically distinct zircon populations were identified: stubby prismatic crystals (width:length of 1:2 to 1:3) in which core-overgrowth relationships are observed; long prismatic crystals (needles) with width:length ratios of ca. 1:10. Analyses performed on group zircons indicated the presence of a ca. 2.0 Ga. old inherited component. Analyses of group zircons plot very close to the concordia and yield an upper intercepts age of 794 Ā± 10 Ma for the crystallization of the volcanic protolith. The study was complemented with whole-rock isotopic analyses by the Rb-Sr and Sm-Nd methods. Rb-Sr isochron obtained with samples from two different outcrops gave data of 829 Ā± 82 Ma (initial 87 Sr/ 86 Sr of 0.7057 Ā± 0.0157) and 691 Ā± 30 Ma (initial 87 Sr/ 86 Sr of 0.7337 Ā± 0.0034). The latter reflects a later Sr-isotopic re-homogenization episode, possibly associated with the intense deformation and metamorphism suffered by these rocks. Sm-Nd isotopic analyses on three samples reveal EN d (T) (T =794 Ma) values in the range of -6.1 to -9.5 which indicate the presence of older (early Proterozoic) crustal Nd. This is consistent with the inheritance pattern shown in the U-Pb isotopic results. (author)
Scaling laws, renormalization group flow and the continuum limit in non-compact lattice QED
International Nuclear Information System (INIS)
Goeckeler, M.; Horsley, R.; Rakow, P.; Schierholz, G.; Sommer, R.
1992-01-01
We investigate the ultra-violet behavior of non-compact lattice QED with light staggered fermions. The main question is whether QED is a non-trivial theory in the continuum limit, and if not, what is its range of validity as a low-energy theory. Perhaps the limited range of validity could offer an explanation of why the fine-structure constant is so small. Non-compact QED undergoes a second-order chiral phase transition at strong coupling, at which the continuum limit can be taken. We examine the phase diagram and the critical behavior of the theory in detail. Moreover, we address the question as to whether QED confines in the chirally broken phase. This is done by investigating the potential between static external charges. We then compute the renormalized charge and derive the Callan-Symanzik Ī²-function in the critical region. No ultra-violet stable zero is found. Instead, we find that the evolution of charge is well described by renormalized perturbation theory, and that the renormalized charge vanishes at the critical point. The consequence is that QED can only be regarded as a cut-off theory. We evaluate the maximum value of the cut-off as a function of the renormalized charge. Next, we compute the masses of fermion-antifermion composite states. The scaling behavior of these masses is well described by an effective action with mean-field critical exponents plus logarithmic corrections. This indicates that also the matter sector of the theory is non-interacting. Finally, we investigate and compare the renormalization group flow of different quantities. Altogether, we find that QED is a valid theory only for samll renormalized charges. (orig.)
Characteristic dynamics near two coalescing eigenvalues incorporating continuum threshold effects
Garmon, Savannah; Ordonez, Gonzalo
2017-06-01
It has been reported in the literature that the survival probability P(t) near an exceptional point where two eigenstates coalesce should generally exhibit an evolution P (t ) Ėt2e-Ī t, in which Ī is the decay rate of the coalesced eigenstate; this has been verified in a microwave billiard experiment [B. Dietz et al., Phys. Rev. E 75, 027201 (2007)]. However, the heuristic effective Hamiltonian that is usually employed to obtain this result ignores the possible influence of the continuum threshold on the dynamics. By contrast, in this work we employ an analytical approach starting from the microscopic Hamiltonian representing two simple models in order to show that the continuum threshold has a strong influence on the dynamics near exceptional points in a variety of circumstances. To report our results, we divide the exceptional points in Hermitian open quantum systems into two cases: at an EP2A two virtual bound states coalesce before forming a resonance, anti-resonance pair with complex conjugate eigenvalues, while at an EP2B two resonances coalesce before forming two different resonances. For the EP2B, which is the case studied in the microwave billiard experiment, we verify that the survival probability exhibits the previously reported modified exponential decay on intermediate time scales, but this is replaced with an inverse power law on very long time scales. Meanwhile, for the EP2A the influence from the continuum threshold is so strong that the evolution is non-exponential on all time scales and the heuristic approach fails completely. When the EP2A appears very near the threshold, we obtain the novel evolution P (t ) Ė1 -C1ā{t } on intermediate time scales, while further away the parabolic decay (Zeno dynamics) on short time scales is enhanced.
Some topics in continuum theory of liquid crystals
Energy Technology Data Exchange (ETDEWEB)
Anderson, Claire
2000-07-01
Since advancements by Ericksen and Leslie in the 1960's, interest in the continuum theory for liquid crystals has escalated. In this thesis, we present the well established continuum theory for nematics, and apply it to the simple Tsvetkov experiment. This analysis is further extended by studying a similar geometric setup which allows additional degrees of freedom. Steady state solutions are studied, and stable/unstable solutions discussed. The bulk of this thesis however, is concerned with the smectic continuum theory. The theory presented allows variable layer spacing, and hence goes beyond the scope of that proposed by Leslie, Stewart and Nakagawa in 1991. With this theory, we initially study a sample of SmA liquid crystal in the bookshelf geometry between two parallel plates, and subject to a strongly anchored pretilt at the boundaries. Weakly anchored solutions are also briefly discussed at the end of this chapter. This work is extended by considering the same problem with a SmC sample, and the distinct differences between the SmA and SmC solutions are highlighted. Symmetric chevron solutions of C1 and C2 type are discussed fully, and energy considerations are made to find the physically realistic configurations. Again, the last part of this chapter is dedicated to solutions subject to weak anchoring. Finally, we take a brief look at Freedericksz transitions when a magnetic field is applied across a cell containing a SmA sample in the bookshelf geometry. The Freedericksz thresholds for two possible deformations are obtained by linearising the appropriate equation, and solving the resulting eigenvalue problem. Numerical calculations finally show where the transitions occur, and confirm the accuracy of the threshold values obtained analytically. (author)
Some topics in continuum theory of liquid crystals
International Nuclear Information System (INIS)
Anderson, Claire
2000-01-01
Since advancements by Ericksen and Leslie in the 1960's, interest in the continuum theory for liquid crystals has escalated. In this thesis, we present the well established continuum theory for nematics, and apply it to the simple Tsvetkov experiment. This analysis is further extended by studying a similar geometric setup which allows additional degrees of freedom. Steady state solutions are studied, and stable/unstable solutions discussed. The bulk of this thesis however, is concerned with the smectic continuum theory. The theory presented allows variable layer spacing, and hence goes beyond the scope of that proposed by Leslie, Stewart and Nakagawa in 1991. With this theory, we initially study a sample of SmA liquid crystal in the bookshelf geometry between two parallel plates, and subject to a strongly anchored pretilt at the boundaries. Weakly anchored solutions are also briefly discussed at the end of this chapter. This work is extended by considering the same problem with a SmC sample, and the distinct differences between the SmA and SmC solutions are highlighted. Symmetric chevron solutions of C1 and C2 type are discussed fully, and energy considerations are made to find the physically realistic configurations. Again, the last part of this chapter is dedicated to solutions subject to weak anchoring. Finally, we take a brief look at Freedericksz transitions when a magnetic field is applied across a cell containing a SmA sample in the bookshelf geometry. The Freedericksz thresholds for two possible deformations are obtained by linearising the appropriate equation, and solving the resulting eigenvalue problem. Numerical calculations finally show where the transitions occur, and confirm the accuracy of the threshold values obtained analytically. (author)
Schizophrenia and the neurodevelopmental continuum:evidence from genomics.
Owen, Michael J; O'Donovan, Michael C
2017-10-01
The idea that disturbances occurring early in brain development contribute to the pathogenesis of schizophrenia, often referred to as the neurodevelopmental hypothesis, has become widely accepted. Despite this, the disorder is viewed as being distinct nosologically, and by implication pathophysiologically and clinically, from syndromes such as autism spectrum disorders, attention-deficit/hyperactivity disorder (ADHD) and intellectual disability, which typically present in childhood and are grouped together as "neurodevelopmental disorders". An alternative view is that neurodevelopmental disorders, including schizophrenia, rather than being etiologically discrete entities, are better conceptualized as lying on an etiological and neurodevelopmental continuum, with the major clinical syndromes reflecting the severity, timing and predominant pattern of abnormal brain development and resulting functional abnormalities. It has also been suggested that, within the neurodevelopmental continuum, severe mental illnesses occupy a gradient of decreasing neurodevelopmental impairment as follows: intellectual disability, autism spectrum disorders, ADHD, schizophrenia and bipolar disorder. Recent genomic studies have identified large numbers of specific risk DNA changes and offer a direct and robust test of the predictions of the neurodevelopmental continuum model and gradient hypothesis. These findings are reviewed in detail. They not only support the view that schizophrenia is a disorder whose origins lie in disturbances of brain development, but also that it shares genetic risk and pathogenic mechanisms with the early onset neurodevelopmental disorders (intellectual disability, autism spectrum disorders and ADHD). They also support the idea that these disorders lie on a gradient of severity, implying that they differ to some extent quantitatively as well as qualitatively. These findings have important implications for nosology, clinical practice and research. Ā© 2017 World
[Continuum based fast Fourier transform processing of infrared spectrum].
Liu, Qing-Jie; Lin, Qi-Zhong; Wang, Qin-Jun; Li, Hui; Li, Shuai
2009-12-01
To recognize ground objects with infrared spectrum, high frequency noise removing is one of the most important phases in spectrum feature analysis and extraction. A new method for infrared spectrum preprocessing was given combining spectrum continuum processing and Fast Fourier Transform (CFFT). Continuum was firstly removed from the noise polluted infrared spectrum to standardize hyper-spectra. Then the spectrum was transformed into frequency domain (FD) with fast Fourier transform (FFT), separating noise information from target information After noise eliminating from useful information with a low-pass filter, the filtered FD spectrum was transformed into time domain (TD) with fast Fourier inverse transform. Finally the continuum was recovered to the spectrum, and the filtered infrared spectrum was achieved. Experiment was performed for chlorite spectrum in USGS polluted with two kinds of simulated white noise to validate the filtering ability of CFFT by contrast with cubic function of five point (CFFP) in time domain and traditional FFT in frequency domain. A circle of CFFP has limited filtering effect, so it should work much with more circles and consume more time to achieve better filtering result. As for conventional FFT, Gibbs phenomenon has great effect on preprocessing result at edge bands because of special character of rock or mineral spectra, while works well at middle bands. Mean squared error of CFFT is 0. 000 012 336 with cut-off frequency of 150, while that of FFT and CFFP is 0. 000 061 074 with cut-off frequency of 150 and 0.000 022 963 with 150 working circles respectively. Besides the filtering result of CFFT can be improved by adjusting the filter cut-off frequency, and has little effect on working time. The CFFT method overcomes the Gibbs problem of FFT in spectrum filtering, and can be more convenient, dependable, and effective than traditional TD filter methods.
Hybrid molecularācontinuum methods: From prototypes to coupling software
Neumann, Philipp
2014-02-01
In this contribution, we review software requirements in hybrid molecular-continuum simulations. For this purpose, we analyze a prototype implementation which combines two frameworks-the Molecular Dynamics framework MarDyn and the framework Peano for spatially adaptive mesh-based simulations-and point out particular challenges of a general coupling software. Based on this analysis, we discuss the software design of our recently published coupling tool. We explain details on its overall structure and show how the challenges that arise in respective couplings are resolved by the software. Ā© 2013 Elsevier Ltd. All rights reserved.
Predicted continuum spectra of type II supernovae - LTE results
Shaviv, G.; Wehrse, R.; Wagoner, R. V.
1985-01-01
The continuum spectral energy distribution of the flux emerging from type II supernovae is calculated from quasi-static radiative transfer through a power-law density gradient, assuming radiative equilibrium and LTE. It is found that the Balmer jump disappears at high effective temperatures and low densities, while the spectrum resembles that of a dilute blackbody but is flatter with a sharper cutoff at the short-wavelength end. A significant UV excess is found in all models calculated. The calculation should be considered exploratory because of significant effects which are anticipated to arise from departure from LTE.
Ipertensione arteriosa, continuum cardiovascolare e ruolo clinico dei sartanii
Directory of Open Access Journals (Sweden)
Maurizio Destro
2011-03-01
Full Text Available The cardiovascular and cardiorenal continuum comprises the transition from cardiovascular risk factors to endothelial dysfunction and atherosclerosis, to chronic congestive heart failure, and-stage renal disease or premature death. RAAS (renin-angiotensin-aldosterone system is involved in all steps along this pathway. Data from clinical studies involving valsartan and other ARBs provide evidence of the reduction of risk of cardiovascular events, and end-organ damage in the heart, kidneys and brain. This paper summarizes the status on research of ARBs based on clinical trials and regulatory approval.
Phase-shift calculation using continuum-discretized states
International Nuclear Information System (INIS)
Suzuki, Y.; Horiuchi, W.; Arai, K.
2009-01-01
We present a method for calculating scattering phase shifts which utilizes continuum-discretized states obtained in a bound-state type calculation. The wrong asymptotic behavior of the discretized state is remedied by means of the Green's function formalism. Test examples confirm the accuracy of the method. The Ī±+n scattering is described using realistic nucleon-nucleon potentials. The 3/2 - and 1/2 - phase shifts obtained in a single-channel calculation are too small in comparison with experiment. The 1/2 + phase shifts are in reasonable agreement with experiment, and gain contributions both from the tensor and central components of the nucleon-nucleon potential.
Evidence for continuum absorption above the quiet sun transition region
International Nuclear Information System (INIS)
Schmahl, E.J.; Orrall, F.Q.
1979-01-01
We report new evidence for continuum absorption in the solar transition zone in EUV spectra obtained from OSO 4, OSO 6, ATM, and full Sun measurements. This absorption shortward of 912 A is manifest everywhere on the Sun's disk. It is present within network cells and boundaries of the quiet Sun, in coronal holes, in active regions, above the limb, and in solar prominences. Models of the upper chromosphere and the transition zone must be modified to include an admixture of neutral hydrogen (or possibly singly ionized helium) with the hotter plasma
From cells to tissue: A continuum model of epithelial mechanics
Ishihara, Shuji; Marcq, Philippe; Sugimura, Kaoru
2017-08-01
A two-dimensional continuum model of epithelial tissue mechanics was formulated using cellular-level mechanical ingredients and cell morphogenetic processes, including cellular shape changes and cellular rearrangements. This model incorporates stress and deformation tensors, which can be compared with experimental data. Focusing on the interplay between cell shape changes and cell rearrangements, we elucidated dynamical behavior underlying passive relaxation, active contraction-elongation, and tissue shear flow, including a mechanism for contraction-elongation, whereby tissue flows perpendicularly to the axis of cell elongation. This study provides an integrated scheme for the understanding of the orchestration of morphogenetic processes in individual cells to achieve epithelial tissue morphogenesis.
NREL Leads Energy Systems Integration, Continuum Magazine: Issue 4 (Book)
Energy Technology Data Exchange (ETDEWEB)
2013-04-01
Continuum Magazine showcases NREL's latest and most impactful clean energy innovations. This issue, 'NREL Leads Energy Systems Integration' explores the discipline of energy systems integration, in particular the role of the laboratory's new, one-of-a-kind Energy System Integration Facility. NREL scientists, engineers, and analysts deeply understand the fundamental science and technologies underpinning major energy producing and consuming systems, as well as the transmission infrastructure and communications and data networks required to integrate energy systems at all scales.
Angular correlation in the two-electron continuum
International Nuclear Information System (INIS)
Kheifets, A. S.; Bray, I.
2006-01-01
Following absorption of a single photon, angles of simultaneous emission of two electrons from a He(n 1 S) atom become more correlated with increasing n. We find that the strength of this correlation is due to the two-electron continuum of the electron-impact ionization of the He + (ns) ion. The strength is determined by the width of the momentum profile of the ionic ns state but not the strength of the electron correlation in the He initial state. This can explain the increasing (over He) angular correlation strength found in double photoionization of targets such as Be, Ne, and H 2
Perturbative approach to continuum generation in a fiber Bragg grating.
Westbrook, P S; Nicholson, J W
2006-08-21
We derive a perturbative solution to the nonlinear SchrĆ¶dinger equation to include the effect of a fiber Bragg grating whose bandgap is much smaller than the pulse bandwidth. The grating generates a slow dispersive wave which may be computed from an integral over the unperturbed solution if nonlinear interaction between the grating and unperturbed waves is negligible. Our approach allows rapid estimation of large grating continuum enhancement peaks from a single nonlinear simulation of the waveguide without grating. We apply our method to uniform and sampled gratings, finding good agreement with full nonlinear simulations, and qualitatively reproducing experimental results.
Submillimeter (Lambda < 1 mm) Continuum Imaging at CSO: A Retrospective
Dowell, C. Darren
2009-01-01
This contribution is submitted on behalf of all students, postdocs, and staff inspired and supported by Tom Phillips to build an instrument and then wait for low precipitable water vapor. Over the 20 plus years of its existence, the Caltech Submillimeter Observatory (CSO) has seen a succession of ever more powerful detectors to measure continuum emission in the shortest submillimeter bands available from Mauna Kea. These instruments have been trained on the nearest solar systems, the most distant galaxies, and objects in between. I show several images collected over the 5 plus year history of the SHARC II camera and anecdotal comparison with past work.
Continuum damage mechanics: Present state and future trends
International Nuclear Information System (INIS)
Chaboche, J.L.
1987-01-01
Continuum Damage Mechanics (CDM) has developed since the initial works of Kachanov and Rabotnov. The paper gives a review of its main features, of the present possibilities and of further developments. Several aspects are considered successively: damage definitions and measures, damage growth equations and anisotropy effects, and use of CDM for local approaches of fracture. Various materials, loading conditions and damaging processes are incorporated in the same general framework. Particular attention is given to the possible connections between different definitions of damage, especially between the CDM definition and the information obtained from material science. (orig.)
Creed, Irena F.; McKnight, Diane M.; Pellerin, Brian; Green, Mark B.; Bergamaschi, Brian; Aiken, George R.; Burns, Douglas A.; Findlay, Stuart E G; Shanley, James B.; Striegl, Robert G.; Aulenbach, Brent T.; Clow, David W.; Laudon, Hjalmar; McGlynn, Brian L.; McGuire, Kevin J.; Smith, Richard A.; Stackpoole, Sarah M.
2015-01-01
A better understanding is needed of how hydrological and biogeochemical processes control dissolved organic carbon (DOC) concentrations and dissolved organic matter (DOM) composition from headwaters downstream to large rivers. We examined a large DOM dataset from the National Water Information System of the US Geological Survey, which represents approximately 100ā000 measurements of DOC concentration and DOM composition at many sites along rivers across the United States. Application of quantile regression revealed a tendency towards downstream spatial and temporal homogenization of DOC concentrations and a shift from dominance of aromatic DOM in headwaters to more aliphatic DOM downstream. The DOC concentrationādischarge (C-Q) relationships at each site revealed a downstream tendency towards a slope of zero. We propose that despite complexities in river networks that have driven many revisions to the River Continuum Concept, rivers show a tendency towards chemostasis (C-Q slope of zero) because of a downstream shift from a dominance of hydrologic drivers that connect terrestrial DOM sources to streams in the headwaters towards a dominance of instream and near-stream biogeochemical processes that result in preferential losses of aromatic DOM and preferential gains of aliphatic DOM.
THE PHILOSOPHY - TOOL CONTINUUM: PROVIDING STRUCTURE TO INDUSTRIAL ENGINEERING CONCEPTS
Directory of Open Access Journals (Sweden)
L. Van Dyk
2012-01-01
Full Text Available
ENGLISH ABSTRACT: Industrial Engineering concepts are often referred to as either a tool, technique, method, approach or philosophy. These terminologies can be positioned on a continuum according to their meaning as defined by the Oxford English dictionary (tools B techniques Bmethods B approaches B philosophies. The philosophy of Total Quality Management is used as example to show how the appropriate naming of Industrial Engineering concepts can enhance the understanding and application thereof. This continuum is used to show that although the philosophies of TQM and Scientific Management may differ, the same pool of tools and techniques are used by both of these philosophies.
AFRIKAANSE OPSOMMING: Bedryfsingenieurs verwys dikwels na filosofiee, benaderings, metodes, tegnieke en gereedskap. Hierdie terminologiee kan kan op 'n kontinuum geposisioneer word na aanleiding van hulle woordeboekbetekenis (gereedskap f-t tegniek f-t metode f-t benadering f-t filosofie. Die filosofie .van Totale Kwaliteitsbeheer (TQM word as voorbeeld gebruik om te wys dat die gepaste benaming van Bedryfsingenieurskonsepte die begrip en toepassing daarvan verhoog . Hierdie kontinuum word gebruik om te wys dat, alhoewel die filosofie van TQM en Wetenskaplike Bestuur ("Scientific Management" verskil, dieselfde versameling vail gereedskap en tegnieke deur beide gebruik word.
Coupling of nonlocal and local continuum models by the Arlequinapproach
Han, Fei
2011-08-09
The objective of this work is to develop and apply the Arlequin framework to couple nonlocal and local continuum mechanical models. A mechanically-based model of nonlocal elasticity, which involves both contact and long-range forces, is used for the \\'fine scale\\' description in which nonlocal interactions are considered to have non-negligible effects. Classical continuum mechanics only involving local contact forces is introduced for the rest of the structure where these nonlocal effects can be neglected. Both models overlap in a coupling subdomain called the \\'gluing area\\' in which the total energy is separated into nonlocal and local contributions by complementary weight functions. A weak compatibility is ensured between kinematics of both models using Lagrange multipliers over the gluing area. The discrete formulation of this specific Arlequin coupling framework is derived and fully described. The validity and limits of the technique are demonstrated through two-dimensional numerical applications and results are compared against those of the fully nonlocal elasticity method. Ā© 2011 John Wiley & Sons, Ltd.
State stability analysis for the fermionic projector in the continuum
Energy Technology Data Exchange (ETDEWEB)
Hoch, Stefan Ludwig
2008-07-01
The principle of the fermionic projector in the continuum gives an indication that there might be a deeper reason why elementary particles only appear with a few definite masses. In this thesis the existence of approximately state-stable configurations is shown. In order to achieve that, we make use of a variational principle for the fermionic projector in the continuum which contains certain contributions supported on the light cone. In a certain sense, these extra terms contain the structure of the underlying discrete spacetime. Lorentz invariant distributions and their convolutions are studied. Some of these are well-defined because the convolution integrals have compactly supported integrands. Other convolutions can be regularized such that the property of being ill-defined only plays a role on the light cone. These results are used to analyze the variational principle and to give criteria for state stability, which can be numerically analyzed. Some plots are presented to allow a decision about state stability and to show how possible configurations could look like. (orig.)
Continuum Vlasov Simulation in Four Phase-space Dimensions
Cohen, B. I.; Banks, J. W.; Berger, R. L.; Hittinger, J. A.; Brunner, S.
2010-11-01
In the VALHALLA project, we are developing scalable algorithms for the continuum solution of the Vlasov-Maxwell equations in two spatial and two velocity dimensions. We use fourth-order temporal and spatial discretizations of the conservative form of the equations and a finite-volume representation to enable adaptive mesh refinement and nonlinear oscillation control [1]. The code has been implemented with and without adaptive mesh refinement, and with electromagnetic and electrostatic field solvers. A goal is to study the efficacy of continuum Vlasov simulations in four phase-space dimensions for laser-plasma interactions. We have verified the code in examples such as the two-stream instability, the weak beam-plasma instability, Landau damping, electron plasma waves with electron trapping and nonlinear frequency shifts [2]^ extended from 1D to 2D propagation, and light wave propagation.^ We will report progress on code development, computational methods, and physics applications. This work was performed under the auspices of the U.S. DOE by LLNL under contract no. DE-AC52-07NA27344. This work was funded by the Lab. Dir. Res. and Dev. Prog. at LLNL under project tracking code 08-ERD-031. [1] J.W. Banks and J.A.F. Hittinger, to appear in IEEE Trans. Plas. Sci. (Sept., 2010). [2] G.J. Morales and T.M. O'Neil, Phys. Rev. Lett. 28,417 (1972); R. L. Dewar, Phys. Fluids 15,712 (1972).
Typology of nonlinear activity waves in a layered neural continuum.
Koch, Paul; Leisman, Gerry
2006-04-01
Neural tissue, a medium containing electro-chemical energy, can amplify small increments in cellular activity. The growing disturbance, measured as the fraction of active cells, manifests as propagating waves. In a layered geometry with a time delay in synaptic signals between the layers, the delay is instrumental in determining the amplified wavelengths. The growth of the waves is limited by the finite number of neural cells in a given region of the continuum. As wave growth saturates, the resulting activity patterns in space and time show a variety of forms, ranging from regular monochromatic waves to highly irregular mixtures of different spatial frequencies. The type of wave configuration is determined by a number of parameters, including alertness and synaptic conditioning as well as delay. For all cases studied, using numerical solution of the nonlinear Wilson-Cowan (1973) equations, there is an interval in delay in which the wave mixing occurs. As delay increases through this interval, during a series of consecutive waves propagating through a continuum region, the activity within that region changes from a single-frequency to a multiple-frequency pattern and back again. The diverse spatio-temporal patterns give a more concrete form to several metaphors advanced over the years to attempt an explanation of cognitive phenomena: Activity waves embody the "holographic memory" (Pribram, 1991); wave mixing provides a plausible cause of the competition called "neural Darwinism" (Edelman, 1988); finally the consecutive generation of growing neural waves can explain the discontinuousness of "psychological time" (Stroud, 1955).
State stability analysis for the fermionic projector in the continuum
International Nuclear Information System (INIS)
Hoch, Stefan Ludwig
2008-01-01
The principle of the fermionic projector in the continuum gives an indication that there might be a deeper reason why elementary particles only appear with a few definite masses. In this thesis the existence of approximately state-stable configurations is shown. In order to achieve that, we make use of a variational principle for the fermionic projector in the continuum which contains certain contributions supported on the light cone. In a certain sense, these extra terms contain the structure of the underlying discrete spacetime. Lorentz invariant distributions and their convolutions are studied. Some of these are well-defined because the convolution integrals have compactly supported integrands. Other convolutions can be regularized such that the property of being ill-defined only plays a role on the light cone. These results are used to analyze the variational principle and to give criteria for state stability, which can be numerically analyzed. Some plots are presented to allow a decision about state stability and to show how possible configurations could look like. (orig.)
Nebular Continuum and Line Emission in Stellar Population Synthesis Models
Energy Technology Data Exchange (ETDEWEB)
Byler, Nell; Dalcanton, Julianne J. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Conroy, Charlie; Johnson, Benjamin D., E-mail: ebyler@astro.washington.edu [Department of Astronomy, Harvard University, Cambridge, MA 02138 (United States)
2017-05-01
Accounting for nebular emission when modeling galaxy spectral energy distributions (SEDs) is important, as both line and continuum emissions can contribute significantly to the total observed flux. In this work, we present a new nebular emission model integrated within the Flexible Stellar Population Synthesis code that computes the line and continuum emission for complex stellar populations using the photoionization code Cloudy. The self-consistent coupling of the nebular emission to the matched ionizing spectrum produces emission line intensities that correctly scale with the stellar population as a function of age and metallicity. This more complete model of galaxy SEDs will improve estimates of global gas properties derived with diagnostic diagrams, star formation rates based on H Ī± , and physical properties derived from broadband photometry. Our models agree well with results from other photoionization models and are able to reproduce observed emission from H ii regions and star-forming galaxies. Our models show improved agreement with the observed H ii regions in the Ne iii/O ii plane and show satisfactory agreement with He ii emission from z = 2 galaxies, when including rotating stellar models. Models including post-asymptotic giant branch stars are able to reproduce line ratios consistent with low-ionization emission regions. The models are integrated into current versions of FSPS and include self-consistent nebular emission predictions for MIST and Padova+Geneva evolutionary tracks.
Continuum radiation emitted from transition metals under ion bombardment
International Nuclear Information System (INIS)
El Boujlaidi, A.; Kaddouri, A.; Ait El Fqih, M.; Hammoum, K.; Aouchiche, H.
2012-01-01
Optical emission of transition metals has been studied during 5 keV Kr + ions bombardment within and without oxygen atmosphere in the colliding chamber. The observed spectra consist of a series of discrete lines superimposed on a broad continuum. Generally, the emission intensity was influenced by the presence of oxygen giving rise to transient effects as well as to an increase in the line intensity. The behaviours of spectral lines were successfully explained in term of electron-transfer process between the excited sputtered atom and the solid surface. In this work, we have focused our study on the continuous radiation emitted during ion bombardment. The experimental results suggest that the continuum emission depends on the nature of metal and very probably related to its electronic structure. The collective deactivation of 3d-shell electrons appears to play a role in the emission of this radiation. The observed enhancement in the presence of oxygen is probably due to a significant contribution of the oxide molecules. (authors)
Anisotropic creep damage in the framework of continuum damage mechanics
International Nuclear Information System (INIS)
Caboche, J.L.
1983-01-01
For some years, various works have shown the possibility of applying continuum mechanics to model the evolution of the damage variable, initially introduced by Kachanov. Of interest here are the complex problems posed by the anisotropy which affects both the elastic behaviour and the viscoplastic one, and also the rupture phenomenon. The main concepts of the Continuum Damage Mechanics are briefly reviewed together with some classical ways to introduce anisotropy of damage in the particular case of proportional loadings. Based on previous works, two generalizations are presented and discussed, which use different kinds of tensors to describe the anisotropy of creep damage: - The first one, by Murakami and Ohno introduces a second rank damage tensor and a net stress tensor through a net area definition. The effective stress-strain behaviour is then obtained by a fourth rank tensor. - The second theory, by the author, uses one effective stress tensor only, defined in terms of the macroscopic strain behaviour, through a fourth-order non-symmetrical damage tensor. The two theories are compared at several levels: difference and similarities are pointed out for the damage evolution during tensile creep as well as for anisotropy effects. The possibilities are discussed and compared on the basis of some existing experimental results, which leads to a partial validation of the two approaches. (orig.)
Anomalous vibrational properties in the continuum limit of glasses
Shimada, Masanari; Mizuno, Hideyuki; Ikeda, Atsushi
2018-02-01
The low-temperature thermal properties of glasses are anomalous with respect to those of crystals. These thermal anomalies indicate that the low-frequency vibrational properties of glasses differ from those of crystals. Recent studies revealed that, in the simplest model of glasses, i.e., the harmonic potential system, phonon modes coexist with soft localized modes in the low-frequency (continuum) limit. However, the nature of low-frequency vibrational modes of more realistic models is still controversial. In the present work, we study the Lennard-Jones (LJ) system using large-scale molecular-dynamics (MD) simulation and establish that the vibrational property of the LJ glass converges to coexistence of the phonon modes and the soft localized modes in the continuum limit as in the case of the harmonic potential system. Importantly, we find that the low-frequency vibrations are rather sensitive to the numerical scheme of potential truncation, which is usually implemented in the MD simulation, and this is the reason why contradictory arguments have been reported by previous works. We also discuss the physical origin of this sensitiveness by means of a linear stability analysis.
Multi Texture Analysis of Colorectal Cancer Continuum Using Multispectral Imagery.
Directory of Open Access Journals (Sweden)
Ahmad Chaddad
Full Text Available This paper proposes to characterize the continuum of colorectal cancer (CRC using multiple texture features extracted from multispectral optical microscopy images. Three types of pathological tissues (PT are considered: benign hyperplasia, intraepithelial neoplasia and carcinoma.In the proposed approach, the region of interest containing PT is first extracted from multispectral images using active contour segmentation. This region is then encoded using texture features based on the Laplacian-of-Gaussian (LoG filter, discrete wavelets (DW and gray level co-occurrence matrices (GLCM. To assess the significance of textural differences between PT types, a statistical analysis based on the Kruskal-Wallis test is performed. The usefulness of texture features is then evaluated quantitatively in terms of their ability to predict PT types using various classifier models.Preliminary results show significant texture differences between PT types, for all texture features (p-value < 0.01. Individually, GLCM texture features outperform LoG and DW features in terms of PT type prediction. However, a higher performance can be achieved by combining all texture features, resulting in a mean classification accuracy of 98.92%, sensitivity of 98.12%, and specificity of 99.67%.These results demonstrate the efficiency and effectiveness of combining multiple texture features for characterizing the continuum of CRC and discriminating between pathological tissues in multispectral images.
Vibrational quasi-continuum in unimolecular multiphoton dissociation
Energy Technology Data Exchange (ETDEWEB)
Garcia Fernandez, P.; Gonzalez-Diaz, P.F.
1987-04-01
The vibrational quasi-continuum of the boron trifluoride molecule has been qualitatively studied and the formalism extended to treat N-normal-mode molecules. The anharmonic potential curves for the BF/sub 3/ normal modes have been calculated, and the computed anharmonicity constants have been tested against the fundamental frequencies. The potential curve of the wagging mode has been simulated by an internal rotation of one of the fluoride atoms. The vibrational-energy levels and wave functions have been calculated applying second-order perturbation theory. The quasi-continuum energy levels of BF/sub 3/ have been obtained by means of a method based in forming adequate linear combinations of wave functions belonging to the N-1 modes resulting from removing the i.r.-active mode;the associated energies have been minimized using a constrained minimization procedure. It has been found that the energy pattern of the N-1 vibrational modes possesses an energy density high enough for constituting a vibrational heat bath and, finally, it has been verified that the ''fictitious'' pattern of the active mode is included in the pattern of the N-1 modes.
Morphing continuum theory for turbulence: Theory, computation, and visualization
Chen, James
2017-10-01
A high order morphing continuum theory (MCT) is introduced to model highly compressible turbulence. The theory is formulated under the rigorous framework of rational continuum mechanics. A set of linear constitutive equations and balance laws are deduced and presented from the Coleman-Noll procedure and Onsager's reciprocal relations. The governing equations are then arranged in conservation form and solved through the finite volume method with a second-order Lax-Friedrichs scheme for shock preservation. A numerical example of transonic flow over a three-dimensional bump is presented using MCT and the finite volume method. The comparison shows that MCT-based direct numerical simulation (DNS) provides a better prediction than Navier-Stokes (NS)-based DNS with less than 10% of the mesh number when compared with experiments. A MCT-based and frame-indifferent Q criterion is also derived to show the coherent eddy structure of the downstream turbulence in the numerical example. It should be emphasized that unlike the NS-based Q criterion, the MCT-based Q criterion is objective without the limitation of Galilean invariance.
Missing links in the root-soil organic matter continuum
Energy Technology Data Exchange (ETDEWEB)
O' Brien, Sarah L. [Argonne National Laboratory (ANL); Iversen, Colleen M [ORNL
2009-01-01
The soil environment remains one of the most complex and poorly understood research frontiers in ecology. Soil organic matter (SOM), which spans a continuum from fresh detritus to highly processed, mineral-associated organic matter, is the foundation of sustainable terrestrial ecosystems. Heterogeneous SOM pools are fueled by inputs from living and dead plants, driven by the activity of micro- and mesofauna, and are shaped by a multitude of abiotic factors. The specialization required to measure unseen processes that occur on a wide range of spatial and temporal scales has led to the partitioning of soil ecology research across several disciplines. In the organized oral session 'Missing links in the root-soil organic matter continuum' at the annual Ecological Society of America meeting in Albuquerque, NM, USA, we joined the call for greater communication and collaboration among ecologists who work at the root-soil interface (e.g. Coleman, 2008). Our goal was to bridge the gap between scientific disciplines and to synthesize disconnected pieces of knowledge from root-centric and soil-centric studies into an integrated understanding of belowground ecosystem processes. We focused this report around three compelling themes that arose from the session: (1) the influence of the rhizosphere on SOM cycling, (2) the role of soil heterotrophs in driving the transformation of root detritus to SOM, and (3) the controlling influence of the soil environment on SOM dynamics. We conclude with a discussion of new approaches for gathering data to bridge gaps in the root-SOM continuum and to inform the next generation of ecosystem models. Although leaf litter has often been considered to be the main source of organic inputs to soil, Ann Russell synthesized a convincing body of work demonstrating that roots, rather than surface residues, control the accumulation of SOM in a variety of ecosystems. Living roots, which are chemically diverse and highly dynamic, also influence a
Waters, L.; Lange, R. A.
2011-12-01
The extent to which degassing affects the oxidation state of arc magmas is widely debated. Several researchers have examined how degassing of mixed H-C-O-S-Cl fluids may change the Fe3+/FeT ratio of magmas, and it has been proposed that degassing may induce either oxidation or reduction depending on the initial oxidation state. A commonly proposed oxidation reaction is related to H2O degassing: H2O (melt) + 2FeO (melt) = H2 (fluid) + Fe2O3 (melt). Another mechanism by which H2O degassing can affect the iron redox state is if dissolved water affects the activity of ferrous and/or ferric iron in the melt. Although Moore et al. (1995) presented experiments showing no evidence of an affect of dissolved water on the activity of the ferric-ferrous ratio in silicate melts, other experimental results (e.g., Baker and Rutherford, 1996; Gaillard et al., 2001; 2003) indicate that there may be such an effect in rhyolite liquids. It has long been understood that rhyolites, owing to their low total iron concentrations, are more sensitive than other magma types to degassing-induced change in redox state. Therefore, a rigorous test of whether H2O degassing affects the redox state of arc magmas is best evaluated on rhyolites. In this study, a comparison is made between the pre-eruptive (pre-degassing) Fe2+ concentrations in six, phenocryst-poor (volatiles, as indicated by the low loss on ignition values (LOI ā¤ 0.7 wt%). In order to test how much oxidation of ferrous iron occurred as a consequence of that degassing, we measured the ferrous iron concentration in the bulk samples by titration, using the Wilson (1960) method, which was successfully tested again three USGS and one Canadian Geological Survey standards. Our results indicate no detectable change within analytical error between pre- and post-eruptive FeO concentrations, with an average deviation of 0.09 wt% and a maximum deviation of 0.15 wt%. Our results show that H2O degassing has no effect on the redox state of
Composite fermion theory for bosonic quantum Hall states on lattices.
MĆ¶ller, G; Cooper, N R
2009-09-04
We study the ground states of the Bose-Hubbard model in a uniform magnetic field, motivated by the physics of cold atomic gases on lattices at high vortex density. Mapping the bosons to composite fermions (CF) leads to the prediction of quantum Hall fluids that have no counterpart in the continuum. We construct trial states for these phases and test numerically the predictions of the CF model. We establish the existence of strongly correlated phases beyond those in the continuum limit and provide evidence for a wider scope of the composite fermion approach beyond its application to the lowest Landau level.
Exploring the HIV continuum of care among young black MSM.
Directory of Open Access Journals (Sweden)
Lisa Hightow-Weidman
Full Text Available HIV disproportionately impacts young, black men who have sex with men (YBMSM who experience disparities across the HIV care continuum. A more nuanced understanding of facilitators and barriers to engagement in care, missed visits, antiretroviral uptake, adherence and viral suppression could improve care and intervention design.A randomized controlled trial of an online intervention, healthMpowerment, enrolled 465 YBMSM (18-30 years; 193 identified as HIV-positive. Bivariable and multivariable analyses of baseline data explored predictors of: engagement in care, missed visits, antiretroviral uptake, self-reported adherence, and viral suppression.Mean age was 24.9 years; most identified as gay (71.0% and were receiving HIV care (89.1%. Among those in care, 52.1% reported no missed visits in the past 12 months, 41 (24.6% reported one missed visit, and 39 (23.4% reported two or more. Having insurance (prevalence odds ratio [POR] 4.5; 95% CI: 1.3, 15.8 and provider self-efficacy (POR 20.1; 95% CI: 6.1, 64.1 were associated with being in care. Those with a college degree (POR 9.1; 95% CI: 1.9, 45.2 and no recent marijuana (POR 2.6; 95% CI: 1.2, 5.6 or methamphetamine use (POR 5.4; 95% CI: 1.0, 28.5 were less likely to miss visits. Most (n = 153, 84.1% had been prescribed antiretroviral therapy. A majority of participants (70.8% reported ā„90% adherence; those with depressive symptoms had 4.7 times the odds of reporting adherence <90% (95% CI: 1.65, 13.37. Of participants who reported viral load testing in the past six months, 65% (n = 102 reported an undetectable viral load. Disclosure to sex partners was associated with viral suppression (POR 6.0; 95% CI: 1.6, 22.4.Multi-level facilitators and barriers to engagement across the continuum of care were identified in this sample of YBMSM. Understanding the distinct needs of YBMSM at each stage of the continuum and addressing them through tailored approaches is critical for long term success in care.
Han, Fei; Azdoud, Yan; Lubineau, Gilles
2014-01-01
We present two modeling approaches for predicting the macroscopic elastic properties of carbon nanotubes/polymer composites with thick interphase regions at the nanotube/matrix frontier. The first model is based on local continuum mechanics
Continuum mechanics simulations of NiO/Ni-YSZ composites during reduction and re-oxidation
DEFF Research Database (Denmark)
Pihlatie, Mikko; Frandsen, Henrik Lund; Kaiser, Andreas
2010-01-01
for the dimensional change arises from the volumetric change related to the phase change NiO ā Ni. The measurable change in bulk length is given by the ceramic YSZ backbone as a response to the stress created by the chemical strain. The different subprocesses described in the model for YSZ were elastic and anelastic...... expansion, diffusional creep, grain boundary sliding (GBS) and microcracking due to excessive stress. In the Ni/NiO phase, nonelastic strains in terms of diffusional and power law creep were implemented, and additionally for NiO deformation due to microcracking and/or pseudoplasticity. Semi...
The arbitrary l continuum states of the hyperbolic molecular potential
Energy Technology Data Exchange (ETDEWEB)
Wei, Gao-Feng, E-mail: fgwei_2000@163.com [School of Physics and Mechatronics Engineering, Xi' an University of Arts and Science, Xi' an 710065 (China); Chen, Wen-Li, E-mail: physwlchen@163.com [Department of Basic Science, Xi' an Peihua University, Xi' an 710065 (China); Dong, Shi-Hai, E-mail: dongsh2@yahoo.com [Escuela Superior de FĆsica y MatemĆ”ticas, Instituto PolitĆ©cnico Nacional, Edificio 9, Unidad Profesional Adolfo LĆ³pez Mateos, Mexico D.F. 07738 (Mexico); Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States)
2014-06-27
Within the framework of partial-wave method, we study in this Letter the arbitrary l continuum states of the SchrĆ¶dinger equation with the hyperbolic molecular potential in terms of an improved approximation to the centrifugal term. We present the normalized radial wave functions and obtain analytical formula of phase shifts. In addition, the corresponding bound states are also discussed by studying the analytical properties of the scattering amplitude. We calculate the energy spectra and scattering phase shifts by the improved, previous approximations and the accurate methods, respectively and find that the improved approximation is better than the previous one since the present results are in better agreement with the accurate ones. - Highlights: ā¢ The hyperbolic potential with arbitrary l state is solved. ā¢ Improved approximation to centrifugal term is used. ā¢ Phase shift formula is derived analytically. ā¢ Accurate results are compared with the present results.
Continuum variational and diffusion quantum Monte Carlo calculations
International Nuclear Information System (INIS)
Needs, R J; Towler, M D; Drummond, N D; Lopez RIos, P
2010-01-01
This topical review describes the methodology of continuum variational and diffusion quantum Monte Carlo calculations. These stochastic methods are based on many-body wavefunctions and are capable of achieving very high accuracy. The algorithms are intrinsically parallel and well suited to implementation on petascale computers, and the computational cost scales as a polynomial in the number of particles. A guide to the systems and topics which have been investigated using these methods is given. The bulk of the article is devoted to an overview of the basic quantum Monte Carlo methods, the forms and optimization of wavefunctions, performing calculations under periodic boundary conditions, using pseudopotentials, excited-state calculations, sources of calculational inaccuracy, and calculating energy differences and forces. (topical review)
Kinematic Analysis of Continuum Robot Consisted of Driven Flexible Rods
Directory of Open Access Journals (Sweden)
Yingzhong Tian
2016-01-01
Full Text Available This paper presents the kinematic analysis of a continuum bionic robot with three flexible actuation rods. Since the motion of the end-effector is actuated by the deformation of the rods, the robot structure is with high elasticity and good compliance and the kinematic analysis of the robot requires special treatment. We propose a kinematic model based on the geometry with constant curvature. The analysis consists of two independent mappings: a general mapping for the kinematics of all robots and a specific mapping for this kind of robots. Both of those mappings are developed for the single section and for the multisections. We aim at providing a guide for kinematic analysis of the similar manipulators through this paper.
Traveling waves in a continuum model of 1D schools
Oza, Anand; Kanso, Eva; Shelley, Michael
2017-11-01
We construct and analyze a continuum model of a 1D school of flapping swimmers. Our starting point is a delay differential equation that models the interaction between a swimmer and its upstream neighbors' wakes, which is motivated by recent experiments in the Applied Math Lab at NYU. We coarse-grain the evolution equations and derive PDEs for the swimmer density and variables describing the upstream wake. We study the equations both analytically and numerically, and find that a uniform density of swimmers destabilizes into a traveling wave. Our model makes a number of predictions about the properties of such traveling waves, and sheds light on the role of hydrodynamics in mediating the structure of swimming schools.
Adhesive contact: from atomistic model to continuum model
International Nuclear Information System (INIS)
Fan Kang-Qi; Jia Jian-Yuan; Zhu Ying-Min; Zhang Xiu-Yan
2011-01-01
Two types of Lennard-Jones potential are widely used in modeling adhesive contacts. However, the relationships between the parameters of the two types of Lennard-Jones potential are not well defined. This paper employs a self-consistent method to derive the Lennard-Jones surface force law from the interatomic Lennard-Jones potential with emphasis on the relationships between the parameters. The effect of using correct parameters in the adhesion models is demonstrated in single sphere-flat contact via continuum models and an atomistic model. Furthermore, the adhesion hysteresis behaviour is investigated, and the S-shaped force-distance relation is revealed by the atomistic model. It shows that the adhesion hysteresis loop is generated by the jump-to-contact and jump-off-contact, which are illustrated by the S-shaped force-distance curve. (atomic and molecular physics)
On the equivalence of continuum and lattice models for fluids
International Nuclear Information System (INIS)
Panagiotopoulos, Athanassios Z.
2000-01-01
It was demonstrated that finely discretized lattice models for fluids with particles interacting via Lennard-Jones or exponential-6 potentials have essentially identical thermodynamic and structural properties to their continuum counterparts. Grand canonical histogram reweighting Monte Carlo calculations were performed for systems with repulsion exponents between 11 and 22. Critical parameters were determined from mixed-field finite-size scaling methods. Numerical equivalence of lattice and continuous space models, within simulation uncertainties, was observed for lattices with ratio of particle diameter Ļ to grid spacing of 10. The lattice model calculations were more efficient computationally by factors between 10 and 20. It was also shown that Lennard-Jones and exponential-6 based models with identical critical properties can be constructed by appropriate choice of the repulsion exponent. (c) 2000 American Institute of Physics
Continuum analysis of biological systems conserved quantities, fluxes and forces
Suraishkumar, G K
2014-01-01
This book addresses the analysis, in the continuum regime, of biological systems at various scales, from the cellular level to the industrial one. It presents both fundamental conservation principles (mass, charge, momentum and energy) and relevant fluxes resulting from appropriate driving forces, which are important for the analysis, design and operation of biological systems. It includes the concept of charge conservation, an important principle for biological systems that is not explicitly covered in any other book of this kind. The book is organized in five parts: mass conservation; charge conservation; momentum conservation; energy conservation; and multiple conservations simultaneously applied. All mathematical aspects are presented step by step, allowing any reader with a basic mathematical background (calculus, differential equations, linear algebra, etc.) to follow the text with ease. The book promotes an intuitive understanding of all the relevant principles and in so doing facilitates their applica...
Imaging of continuum states of the He22+ quasimolecule
International Nuclear Information System (INIS)
Schmidt, L. Ph. H.; Schoeffler, M. S.; Stiebing, K. E.; Schmidt-Boecking, H.; Doerner, R.; Afaneh, F.; Weber, Th.
2007-01-01
Using cold target recoil ion momentum spectroscopy (COLTRIMS) we have investigated the production of one free electron in slow He 2+ +He(1s 2 ) collisions. At projectile velocities between 0.6 and 1.06 a.u. (9-28 keV/u), the fully differential cross section was measured state selective with respect to the second electron, which is bound either at the target or the projectile. We provide a comprehensive data set comprising state selective total cross section, scattering angle dependent single differential cross sections, and fully differential cross section. We show that the momentum distribution of the electron in the continuum image the relevant molecular orbitals for the reaction channel under consideration. By choosing the bound electron final state at the target or projectile and the impact parameter we can select these orbitals and manipulate their relative phase
Calculation of gas migration in fractured rock - a continuum approach
International Nuclear Information System (INIS)
Braester, C.
1987-09-01
A study of gas migration from low level radioactive repositories in which the fractured rock mass was conceptualized as a continuum, was carried out by the aid of a computer program based on a finite difference numerical method of solution to the equations of flow. The calculations are intended to correspond to the prevailing in the Forsmark low level repository area where radioactive waste repository caverns are planned to be located at a depth of about 50 metres below the sea level. Calculations were worked out for a constant gas flow rate equivalent to a gas production of 20 000 normal cubic metres per year. The investigated flow domain was a vertical cross-section passing through the repository. The results show that in the empty cavern the gas formed in the cavern moves almost instantaneously upward amd accumulates below the roof of the cavern. (orig./DG)
Cancer Patient Navigator Tasks across the Cancer Care Continuum
Braun, Kathryn L.; Kagawa-Singer, Marjorie; Holden, Alan E. C.; Burhansstipanov, Linda; Tran, Jacqueline H.; Seals, Brenda F.; Corbie-Smith, Giselle; Tsark, JoAnn U.; Harjo, Lisa; Foo, Mary Anne; Ramirez, Amelie G.
2011-01-01
Cancer patient navigation (PN) programs have been shown to increase access to and utilization of cancer care for poor and underserved individuals. Despite mounting evidence of its value, cancer patient navigation is not universally understood or provided. We describe five PN programs and the range of tasks their navigators provide across the cancer care continuum (education and outreach, screening, diagnosis and staging, treatment, survivorship, and end-of-life). Tasks are organized by their potential to make cancer services understandable, available, accessible, affordable, appropriate, and accountable. Although navigators perform similar tasks across the five programs, their specific approaches reflect differences in community culture, context, program setting, and funding. Task lists can inform the development of programs, job descriptions, training, and evaluation. They also may be useful in the move to certify navigators and establish mechanisms for reimbursement for navigation services. PMID:22423178
Scissors strength in the quasi-continuum of actinides
Directory of Open Access Journals (Sweden)
Guttormsen M.
2014-03-01
Full Text Available The M1-scissors resonance has been measured for the first time in the quasi-continuum of actinides. The strength and position of the resonances in 231,232,233Th were determined by particle-Ī³ coincidences using deuteron induced reactions on a 232Th target. The residual nuclei show a strong integrated strength of BM1 = 9Ā āĀ 11Ā Āµn2 in the EĪ³ = 1.0Ā āĀ 3.5Ā MeV region. The presence of the scissors resonance modifies significantly the (n,Ī³ cross section, which has impact on fuel-cycle simulations of fast nuclear reactors and nucleosynthesis in explosive stellar environments.
Continuum damage mechanics analysis of crack tip zone
International Nuclear Information System (INIS)
Yinchu, L.; Jianping, Z.
1989-01-01
The crack tip field and its intensity factor play an important role in fracture mechanics. Generally, the damage such as microcracks, microvoids etc. will initiate and grow in materials as the cracked body is subjected to external loadings, especially in the crack tip zone. The damage evolution will load to the crack tip damage field and the change of the stress, strain and displacement fields of cracks tip zone. In this paper, on the basis of continuum damage mechanics, the authors have derived the equations which the crack tip field and its intensity factor must satisfy in a loading process, calculated the angle distribution curves of stress, strain and displacement fields in a crack tip zone and have compared them with the corresponding curves of HRR field and linear elastic field in undamaged materials. The equations of crack tip field intensity factors have been solved and its solutions give the variation of the field intensity factors with the loading parameter
Breast cancer prevention across the cancer care continuum.
Klemp, Jennifer R
2015-05-01
To review the current state of breast cancer prevention from primary prevention through survivorship, highlight cross-cuttingĀ issues, and discuss strategies for clinical integration and future research. Published articles between 1985 and 2015 and original research. Cancer risk persists across the lifespan. Interprofessional strategies to reduce morbidity and mortality from cancer include primary, secondary, and tertiary prevention (survivorship). Prevention strategies across the cancer care continuum are cross-cutting and focus on measures to: prevent the onset of disease, identify and treat asymptomatic persons who have already developed risk factors or preclinical disease, and restore function, minimize the negative effects of disease, and prevent disease-related complications. Oncology nurses and advanced practice nurses are vital in the delivery of breast cancer prevention strategies. Published by Elsevier Inc.
The relationship between continuum homogeneity and statistical homogeneity in cosmology
International Nuclear Information System (INIS)
Stoeger, W.R.; Ellis, G.F.R.; Hellaby, C.
1987-01-01
Although the standard Friedmann-Lemaitre-Robertson-Walker (FLRW) Universe models are based on the concept that the Universe is spatially homogeneous, up to the present time no definition of this concept has been proposed that could in principle be tested by observation. Such a definition is here proposed, based on a simple spatial averaging procedure, which relates observable properties of the Universe to the continuum homogeneity idea that underlies the FLRW models. It turns out that the statistical homogeneity often used to describe the distribution of matter on a large scale does not imply spatial homogeneity according to this definition, and so cannot be simply related to a FLRW Universe model. Values are proposed for the homogeneity parameter and length scale of homogeneity of the Universe. (author)
Electron capture to the continuum from atomic hydrogen
International Nuclear Information System (INIS)
Glass, G.A.; Engar, P.; Berry, S.D.; Breinig, M.; Deserio, R.; Elston, S.B.; Sellin, I.A.
1984-01-01
The first known measurement of the differential cross section for electron capture to the continuum(ECC) from atomic hydrogen is presented. A 12 MeV beam of C 6+ ions traversed a static target of atomic hydrogen produced by an electron impact heated dissociation oven. The resulting ECC spectrum was obtained with a channel electron multiplier detector mounted at the exit of a 160 0 spherical sector electrostatic spectrometer with an angular acceptance of 2 0 . The ECC spectrum clearly shows the asymmetry generally associated with ECC spectra from gaseous targets. The ratio of the singly differential cross section of H to that of H 2 was found to be 0.80. 16 references, 3 figures
Parsimonious evaluation of concentric-tube continuum robot equilibrium conformation.
Rucker, Daniel Caleb; Webster Iii, Robert J
2009-09-01
Dexterous at small diameters, continuum robots consisting of precurved concentric tubes are well-suited for minimally invasive surgery. These active cannulas are actuated by relative translations and rotations applied at the tube bases, which create bending via elastic tube interaction. An accurate kinematic model of cannula shape is required for applications in surgical and other settings. Previous models are limited to circular tube precurvatures, and neglect torsional deformation in curved sections. Recent generalizations account for arbitrary tube preshaping and bending and torsion throughout the cannula, providing differential equations that define cannula shape. In this paper, we show how to simplify these equations using Frenet-Serret frames. An advantage of this approach is the interpretation of torsional components of the preset tube shapes as "forcing functions" on the cannula's differential equations. We also elucidate a process for numerically solving the differential equations, and use it to produce simulations illustrating the implications of torsional deformation and helical tube shapes.
Maintaining bone health in prostate cancer throughout the disease continuum.
Saad, Fred; Eastham, James
2010-06-01
Prostate cancer (PC) is the most prevalent malignancy in men, with 604,506 new cases diagnosed yearly worldwide. Maintaining bone health is important during all stages of PC, including patients who experience bone loss from androgen-deprivation therapy and patients who develop bone metastases. Patients with bone metastases often experience severe bone pain and are at increased risk for potentially debilitating skeletal-related events. Bisphosphonates are a well-established treatment option for patients with bone metastases from solid tumors and bone lesions from multiple myeloma. Zoledronic acid (ZOL) is the only bisphosphonate (BP) that has been extensively studied in patients with castration-recurrent PC and is indicated for treating patients with bone metastases from PC in conjunction with standard antineoplastic therapy. This review will examine the breadth of evidence supporting a role for ZOL and emerging therapies in managing patients with PC throughout the disease continuum. 2010 Elsevier Inc. All rights reserved.
Radio-continuum emission from quasar host galaxies
International Nuclear Information System (INIS)
Condon, J. J.; Gower, A. C.; Hutchings, J. B.; Victoria Univ., Canada; Dominion Astrophysical Observatory, Victoria)
1987-01-01
Seven low-redshift quasars that are likely to be in spiral galaxies have been observed in a search for radio-continuum emission from the host galaxies of quasars. The properties of the individual quasars are listed, and 1.49 GHz contour maps of the seven quasar fields are presented. Map parameters and radio source parameters are given along with optical images of three of the objects. The results indicate that these quasars probably do reside in spiral galaxies. The radio luminosities, sizes, orientations, and u values all indicate that relativistic beaming alone cannot be used to explain the differences between the present sources and the far stronger radio sources seen in blazars or larger optically selected quasar samples. However, an apparent correlation between the radio luminosity and the ratio of the optical nuclear to host-galaxy luminosity is consistent with some beaming of nuclear radiation. 26 references
Jumping to conclusions and the continuum of delusional beliefs.
Warman, Debbie M; Lysaker, Paul H; Martin, Joel M; Davis, Louanne; Haudenschield, Samantha L
2007-06-01
The present study examined the jumping to conclusions reasoning bias across the continuum of delusional ideation by investigating individuals with active delusions, delusion prone individuals, and non-delusion prone individuals. Neutral and highly self-referent probabilistic reasoning tasks were employed. Results indicated that individuals with delusions gathered significantly less information than delusion prone and non-delusion prone participants on both the neutral and self-referent tasks, (preferent task (p=.002). Those with delusions and those who were delusion prone reported higher confidence in their performance on the self-referent task than they did the neutral task (p=.02), indicating that high self-reference impacted information processing for individuals in both of these groups. The results are discussed in relation to previous research in the area of probabilistic reasoning and delusions.
Wave propagation in nanostructures nonlocal continuum mechanics formulations
Gopalakrishnan, Srinivasan
2013-01-01
Wave Propagation in Nanostructures describes the fundamental and advanced concepts of waves propagating in structures that have dimensions of the order of nanometers. The book is fundamentally based on non-local elasticity theory, which includes scale effects in the continuum model. The book predominantly addresses wave behavior in carbon nanotubes and graphene structures, although the methods of analysis provided in this text are equally applicable to other nanostructures. The book takes the reader from the fundamentals of wave propagation in nanotubes to more advanced topics such as rotating nanotubes, coupled nanotubes, and nanotubes with magnetic field and surface effects. The first few chapters cover the basics of wave propagation, different modeling schemes for nanostructures and introduce non-local elasticity theories, which form the building blocks for understanding the material provided in later chapters. A number of interesting examples are provided to illustrate the important features of wave behav...
Growth limit of carbon onions ā A continuum mechanical study
DEFF Research Database (Denmark)
Todt, Melanie; Bitsche, Robert; Hartmann, Markus A.
2014-01-01
of carbon onions and, thus, can be a reason for the limited size of such particles. The loss of stability is mainly evoked by van der Waals interactions between misfitting neighboring layers leading to self-equilibrating stress states in the layers due to mutual accommodation. The influence of the curvature......The growth of carbon onions is simulated using continuum mechanical shell models. With this models it is shown that, if a carbon onion has grown to a critical size, the formation of an additional layer leads to the occurrence of a structural instability. This instability inhibits further growth...... induced surface energy and its consequential stress state is investigated and found to be rather negligible. Furthermore, it is shown that the nonlinear character of the van der Waals interactions has to be considered to obtain maximum layer numbers comparable to experimental observations. The proposed...
Accuracy of local exchange in the calculation of continuum wavefunctions
International Nuclear Information System (INIS)
Biava, D A; Bartschat, K; Saha, H P; Madison, D H
2002-01-01
It is well known that electron exchange can play an important role in electron-impact elastic, inelastic and ionization scattering from atoms and molecules. The proper theoretical treatment of exchange yields an inhomogeneous differential equation with a non-local exchange operator. To simplify the calculation, a local approximation is often made for this non-local operator. In this paper, we examine the accuracy of this approximation for the calculation of elastic scattering continuum waves in the presence of an argon ion with a single vacancy in the p-shell. It is found that one can reliably use the local exchange approximation for ionization leading to s-state vacancies but not p-state vacancies
International Nuclear Information System (INIS)
Fujimaki, Hirokazu; Xu Hong; Aoki, Ken-ichiro
1991-01-01
Fifty-three volcanic rocks from Dogo island, Oki, Shimane Prefecture, southwestern Japan were analyzed for Sr isotopic compositions with two basement rocks. The rock samples consist of calc-alkali rock suite, Nagaoda shoshonite-banakite suite, Oki trachyte-rhyolite suite, Dogo mugearite suite, Hei trachyte and Tsuzurao rhyolite series, and Daimanjiyama, Ohmine, Kuroshima, Shiroshimazaki, Saigo, and Misaki alkali basalt groups in the order of probable eruption sequence. The volcanic rocks of calc-alkali suite and shoshonite-banakite suite were produced before Japan Sea opening (ca. 15 Ma), and both have 87 Sr/ 86 Sr ratios higher than 0.7068. Long after Japan Sea opening Oki-trachyte-rhyolite suite was erupted (ca. 6.6 Ma); they have rather low 87 Sr/ 86 Sr ratios (0.7066-0.7081). Mugearites followed and have similar Sr isotopic composition, whereas 4.6 Ma old Daimanjiyama basalts have clearly low 87 Sr/ 86 Sr ratios (0.7050-0.7051). The rocks erupted 3-4 Ma seem to have the lowest 87 Sr/ 86 Sr ratios; they are Ohmine, Kuroshima, Shiroshimazaki alkali basalt suites (0.7044-0.7048). The 87 Sr/ 86 Sr ratios of the Saigo basalts erupted 0.84 Ma are higher than those erupted 3-4 Ma. The latest volcanic products in Dogo island, Misaki basalt suite has even higher 87 Sr/ 86 Sr ratios (0.7054-0.7057) than the Saigo basalt suite. Thus, temporal and systematic variation of Sr isotopic compositions of the volcanic rocks from Dogo can be recognized. The 87 Sr/ 86 Sr ratios of the rocks were once as high as 0.7066 or even higher than 0.708, but they started decreasing down to ca. 0.7044-0.7048 4-3 Ma ago. Since then the ratios rebounded to 0.7049-0.7055. The Hei trachyte and Tsuzurao rhyolite series are not included in this temporal and systematic change. The mantle diapir associated with Japan Sea spreading might have caused the decrease in the ratios, and either Pacific Ocean plate or Philippine Sea plate subduction may be responsible for this rebound. (author)
The structure of protostellar dense cores: a millimeter continuum study
International Nuclear Information System (INIS)
Motte, Frederique
1998-01-01
A comprehensive theoretical scenario explains low-mass star formation and describes the gravitational collapse of an isolated 'ideal' dense core. The major aim of this thesis is to check the standard model predictions on the structure of protostellar dense cores (or envelopes). The earliest stages of star formation remain poorly known because the protostars are still deeply embedded in massive, opaque circumstellar cocoons. On the one hand, sensitive bolometer arrays very recently allow us to measure the millimeter continuum emission arising from dense cores. Such observations are a powerful tool to constrain the density structure of proto-stellar dense cores (on large length scale). In particular, we studied the structure of isolated proto-stellar envelopes in Taurus and protostars in the Ļ Ophiuchi cluster. In order to accurately derive their envelope density power law, we simulated the observation of several envelope models. Then we show that most of the Taurus protostars present a density structure consistent with the standard model predictions. In contrast, dense cores in Ļ Ophiuchi main cloud are highly fragmented and protostellar envelope have finite size. Moreover fragmentation appears to be essential in determining the final stellar mass of Ļ Oph forming stars. In clusters, fragmentation may thus be at the origin of the stellar initial mass function (IMF). On the other hand, our interferometric millimeter continuum observations are tracing (with higher angular resolution) the inner part of protostellar envelopes. Our study show that disks during protostellar stages are not yet massive and thus do not perturb the analysis of envelope density structure. (author) [fr
On the design of the NIF Continuum Spectrometer
Thorn, D. B.; MacPhee, A.; Ayers, J.; Galbraith, J.; Hardy, C. M.; Izumi, N.; Bradley, D. K.; Pickworth, L. A.; Bachmann, B.; Kozioziemski, B.; Landen, O.; Clark, D.; Schneider, M. B.; Hill, K. W.; Bitter, M.; Nagel, S.; Bell, P. M.; Person, S.; Khater, H. Y.; Smith, C.; Kilkenny, J.
2017-08-01
In inertial confinement fusion (ICF) experiments on the National Ignition Facility (NIF), measurements of average ion temperature using DT neutron time of flight broadening and of DD neutrons do not show the same apparent temperature. Some of this may be due to time and space dependent temperature profiles in the imploding capsule which are not taken into account in the analysis. As such, we are attempting to measure the electron temperature by recording the free-free electron-ion scattering-spectrum from the tail of the Maxwellian temperature distribution. This will be accomplished with the new NIF Continuum Spectrometer (ConSpec) which spans the x-ray range of 20 keV to 30 keV (where any opacity corrections from the remaining mass of the ablator shell are negligible) and will be sensitive to temperatures between Ė 3 keV and 6 keV. The optical design of the ConSpec is designed to be adaptable to an x-ray streak camera to record time resolved free-free electron continuum spectra for direct measurement of the dT/dt evolution across the burn width of a DT plasma. The spectrometer is a conically bent Bragg crystal in a focusing geometry that allows for the dispersion plane to be perpendicular to the spectrometer axis. Additionally, to address the spatial temperature dependence, both time integrated and time resolved pinhole and penumbral imaging will be provided along the same polar angle. The optical and mechanical design of the instrument is presented along with estimates for the dispersion, solid angle, photometric sensitivity, and performance.
Benchmarking Continuum Solvent Models for Keto-Enol Tautomerizations.
McCann, Billy W; McFarland, Stuart; Acevedo, Orlando
2015-08-13
Experimental free energies of tautomerization, ĪGT, were used to benchmark the gas-phase predictions of 17 different quantum mechanical methods and eight basis sets for seven keto-enol tautomer pairs dominated by their enolic form. The G4 method and M06/6-31+G(d,p) yielded the most accurate results, with mean absolute errors (MAE's) of 0.95 and 0.71 kcal/mol, respectively. Using these two theory levels, the solution-phase ĪGT values for 23 unique tautomer pairs composed of aliphatic ketones, Ī²-dicarbonyls, and heterocycles were computed in multiple protic and aprotic solvents. The continuum solvation models, namely, polarizable continuum model (PCM), polarizable conductor calculation model (CPCM), and universal solvation model (SMD), gave relatively similar MAE's of ā¼1.6-1.7 kcal/mol for G4 and ā¼1.9-2.0 kcal/mol with M06/6-31+G(d,p). Partitioning the tautomer pairs into their respective molecular types, that is, aliphatic ketones, Ī²-dicarbonyls, and heterocycles, and separating out the aqueous versus nonaqueous results finds G4/PCM utilizing the UA0 cavity to be the overall most accurate combination. Free energies of activation, ĪG(ā”), for the base-catalyzed keto-enol interconversion of 2-nitrocyclohexanone were also computed using six bases and five solvents. The M06/6-31+G(d,p) reproduced the ĪG(ā”) with MAE's of 1.5 and 1.8 kcal/mol using CPCM and SMD, respectively, for all combinations of base and solvent. That specific enolization was previously proposed to proceed via a concerted mechanism in less polar solvents but shift to a stepwise mechanism in more polar solvents. However, the current calculations suggest that the stepwise mechanism operates in all solvents.
Equations of motion for anisotropic nonlinear elastic continuum in gravitational field
International Nuclear Information System (INIS)
Sokolov, S.N.
1994-01-01
Equations of motion for anisotropic nonlinear elastic continuum in the gravitational field are written in the form convenient for numerical calculations. The energy-stress tensor is expressed through scalar and tensor products of three vectors frozen in the continuum. Examples of expansion of the energy-stress tensor into scalar and tensor invariants corresponding to some crystal classes are given. 47 refs
An improved particle population balance equation in the continuum-slip regime
Directory of Open Access Journals (Sweden)
Xie Mingliang
2016-01-01
Full Text Available An improved moment model is proposed to solve the population balance equation for Brownian coagulation in the continuum-slip regime, and it reduces to a known one in open literature when the non-linear terms in the slip correction factor are ignored. The present model shows same asymptotic behavior as that in the continuum regime.
Directory of Open Access Journals (Sweden)
Himanshu Sharma
2016-07-01
Full Text Available Due to its roots in fundamental thermodynamic framework, continuum damage approach is popular for modeling asphalt concrete behavior. Currently used continuum damage models use mixture averaged values for model parameters and assume deterministic damage process. On the other hand, significant scatter is found in fatigue data generated even under extremely controlled laboratory testing conditions. Thus, currently used continuum damage models fail to account the scatter observed in fatigue data. This paper illustrates a novel approach for probabilistic fatigue life prediction based on viscoelastic continuum damage approach. Several specimens were tested for their viscoelastic properties and damage properties under uniaxial mode of loading. The data thus generated were analyzed using viscoelastic continuum damage mechanics principles to predict fatigue life. Weibull (2 parameter, 3 parameter and lognormal distributions were fit to fatigue life predicted using viscoelastic continuum damage approach. It was observed that fatigue damage could be best-described using Weibull distribution when compared to lognormal distribution. Due to its flexibility, 3-parameter Weibull distribution was found to fit better than 2-parameter Weibull distribution. Further, significant differences were found between probabilistic fatigue curves developed in this research and traditional deterministic fatigue curve. The proposed methodology combines advantages of continuum damage mechanics as well as probabilistic approaches. These probabilistic fatigue curves can be conveniently used for reliability based pavement design. Keywords: Probabilistic fatigue curve, Continuum damage mechanics, Weibull distribution, Lognormal distribution
A continuum model for flow induced by metachronal coordination between beating cilia
Hussong, J.; Breugem, W.P.; Westerweel, J.
2011-01-01
In this numerical study we investigate the flow induced by metachronal coordination between beating cilia arranged in a densely packed layer by means of a continuum model. The continuum approach allows us to treat the problem as two-dimensional as well as stationary, in a reference frame moving with
International Nuclear Information System (INIS)
Rabidoux, Katie; Pisano, D. J.; Kepley, Amanda A.; Johnson, Kelsey E.; Balser, Dana S.
2014-01-01
We observed radio continuum emission in 27 local (D < 70 Mpc) star-forming galaxies with the Robert C. Byrd Green Bank Telescope between 26 GHz and 40 GHz using the Caltech Continuum Backend. We obtained detections for 22 of these galaxies at all four sub-bands and four more marginal detections by taking the average flux across the entire bandwidth. This is the first detection (full or marginal) at these frequencies for 22 of these galaxies. We fit spectral energy distributions (SEDs) for all of the four sub-band detections. For 14 of the galaxies, SEDs were best fit by a combination of thermal free-free and nonthermal synchrotron components. Eight galaxies with four sub-band detections had steep spectra that were only fit by a single nonthermal component. Using these fits, we calculated supernova rates, total number of equivalent O stars, and star formation rates within each ā¼23'' beam. For unresolved galaxies, these physical properties characterize the galaxies' recent star formation on a global scale. We confirm that the radio-far-infrared correlation holds for the unresolved galaxies' total 33 GHz flux regardless of their thermal fractions, though the scatter on this correlation is larger than that at 1.4 GHz. In addition, we found that for the unresolved galaxies, there is an inverse relationship between the ratio of 33 GHz flux to total far-infrared flux and the steepness of the galaxy's spectral index between 1.4 GHz and 33 GHz. This relationship could be an indicator of the timescale of the observed episode of star formation.
Generalized Continuum: from Voigt to the Modeling of Quasi-Brittle Materials
Directory of Open Access Journals (Sweden)
Jamile Salim Fuina
2010-12-01
Full Text Available This article discusses the use of the generalized continuum theories to incorporate the effects of the microstructure in the nonlinear finite element analysis of quasi-brittle materials and, thus, to solve mesh dependency problems. A description of the problem called numerically induced strain localization, often found in Finite Element Method material non-linear analysis, is presented. A brief historic about the Generalized Continuum Mechanics based models is presented, since the initial work of Voigt (1887 until the more recent studies. By analyzing these models, it is observed that the Cosserat and microstretch approaches are particular cases of a general formulation that describes the micromorphic continuum. After reporting attempts to incorporate the material microstructure in Classical Continuum Mechanics based models, the article shows the recent tendency of doing it according to assumptions of the Generalized Continuum Mechanics. Finally, it presents numerical results which enable to characterize this tendency as a promising way to solve the problem.
Solar radio continuum storms and a breathing magnetic field model. Final report
International Nuclear Information System (INIS)
1975-01-01
Radio noise continuum emissions observed in metric and decametric wave frequencies are, in general, associated with actively varying sunspot groups accompanied by the S-component of microwave radio emissions. These continuum emission sources, often called type I storm sources, are often associated with type III burst storm activity from metric to hectometric wave frequencies. This storm activity is, therefore, closely connected with the development of these continuum emission sources. It is shown that the S-component emission in microwave frequencies generally precedes, by several days, the emission of these noise continuum storms of lower frequencies. In order for these storms to develop, the growth of sunspot groups into complex types is very important in addition to the increase of the average magnetic field intensity and area of these groups. After giving a review on the theory of these noise continuum storm emissions, a model is briefly considered to explain the relation of the emissions to the storms
Chemolli, Emanuela; GagnĆ©, MarylĆØne
2014-06-01
Self-determination theory (SDT) proposes a multidimensional conceptualization of motivation in which the different regulations are said to fall along a continuum of self-determination. The continuum has been used as a basis for using a relative autonomy index as a means to create motivational scores. Rasch analysis was used to verify the continuum structure of the Multidimensional Work Motivation Scale and of the Academic Motivation Scale. We discuss the concept of continuum against SDT's conceptualization of motivation and argue against the use of the relative autonomy index on the grounds that evidence for a continuum structure underlying the regulations is weak and because the index is statistically problematic. We suggest exploiting the full richness of SDT's multidimensional conceptualization of motivation through the use of alternative scoring methods when investigating motivational dynamics across life domains.
The Continuum of Aging and Age-Related Diseases: Common Mechanisms but Different Rates
Directory of Open Access Journals (Sweden)
Claudio Franceschi
2018-03-01
Full Text Available Geroscience, the new interdisciplinary field that aims to understand the relationship between aging and chronic age-related diseases (ARDs and geriatric syndromes (GSs, is based on epidemiological evidence and experimental data that aging is the major risk factor for such pathologies and assumes that aging and ARDs/GSs share a common set of basic biological mechanisms. A consequence is that the primary target of medicine is to combat aging instead of any single ARD/GSs one by one, as favored by the fragmentation into hundreds of specialties and sub-specialties. If the same molecular and cellular mechanisms underpin both aging and ARDs/GSs, a major question emerges: which is the difference, if any, between aging and ARDs/GSs? The hypothesis that ARDs and GSs such as frailty can be conceptualized as accelerated aging will be discussed by analyzing in particular frailty, sarcopenia, chronic obstructive pulmonary disease, cancer, neurodegenerative diseases such as Alzheimer and Parkinson as well as Down syndrome as an example of progeroid syndrome. According to this integrated view, aging and ARDs/GSs become part of a continuum where precise boundaries do not exist and the two extremes are represented by centenarians, who largely avoided or postponed most ARDs/GSs and are characterized by decelerated aging, and patients who suffered one or more severe ARDs in their 60s, 70s, and 80s and show signs of accelerated aging, respectively. In between these two extremes, there is a continuum of intermediate trajectories representing a sort of gray area. Thus, clinically different, classical ARDs/GSs are, indeed, the result of peculiar combinations of alterations regarding the same, limited set of basic mechanisms shared with the aging process. Whether an individual will follow a trajectory of accelerated or decelerated aging will depend on his/her genetic background interacting lifelong with environmental and lifestyle factors. If ARDs and GSs are
Shapes of Venusian 'pancake' domes imply episodic emplacement and silicic composition
Fink, Jonathan H.; Bridges, Nathan T.; Grimm, Robert E.
1993-01-01
The main evidence available for constraining the composition of the large circular 'pancake' domes on Venus is their gross morphology. Laboratory simulations using polyethylene glycol show that the height to diameter (aspect) ratios of domes of a given total volume depend critically on whether their extrusion was continuous or episodic, with more episodes leading to greater cooling and taller domes. Thus without observations of their emplacement, the compositions of Venusian domes cannot be uniquely constrained by their morphology. However, by considering a population of 51 Venusian domes to represent a sampling of many stages during the growth of domes with comparable histories, and by plotting aspect ratio versus total volume, we find that the shapes of the domes are most consistent with episodic emplacement. On Earth this mode of dome growth is found almost exclusively in lavas of dacite to rhyolite composition, strengthening earlier inferences about the presence of evolved magmas on Venus.
Swarm robotics and complex behaviour of continuum material
dell'Erba, Ramiro
2018-05-01
In swarm robotics, just as for an animal swarm in nature, one of the aims is to reach and maintain a desired configuration. One of the possibilities for the team, to reach this aim, is to see what its neighbours are doing. This approach generates a rules system governing the movement of the single robot just by reference to neighbour's motion. The same approach is used in position-based dynamics to simulate behaviour of complex continuum materials under deformation. Therefore, in some previous works, we have considered a two-dimensional lattice of particles and calculated its time evolution by using a rules system derived from our experience in swarm robotics. The new position of a particle, like the element of a swarm, is determined by the spatial position of the other particles. No dynamic is considered, but it can be thought as being hidden in the behaviour rules. This method has given good results in some simple situations reproducing the behaviour of deformable bodies under imposed strain. In this paper we try to stress our model to highlight its limits and how they can be improved. Some other, more complex, examples are computed and discussed. Shear test, different lattices, different fracture mechanisms and ASTM shape sample behaviour have been investigated by the software tool we have developed.
Verification of continuum drift kinetic equation solvers in NIMROD
Energy Technology Data Exchange (ETDEWEB)
Held, E. D.; Ji, J.-Y. [Utah State University, Logan, Utah 84322-4415 (United States); Kruger, S. E. [Tech-X Corporation, Boulder, Colorado 80303 (United States); Belli, E. A. [General Atomics, San Diego, California 92186-5608 (United States); Lyons, B. C. [Program in Plasma Physics, Princeton University, Princeton, New Jersey 08543-0451 (United States)
2015-03-15
Verification of continuum solutions to the electron and ion drift kinetic equations (DKEs) in NIMROD [C. R. Sovinec et al., J. Comp. Phys. 195, 355 (2004)] is demonstrated through comparison with several neoclassical transport codes, most notably NEO [E. A. Belli and J. Candy, Plasma Phys. Controlled Fusion 54, 015015 (2012)]. The DKE solutions use NIMROD's spatial representation, 2D finite-elements in the poloidal plane and a 1D Fourier expansion in toroidal angle. For 2D velocity space, a novel 1D expansion in finite elements is applied for the pitch angle dependence and a collocation grid is used for the normalized speed coordinate. The full, linearized Coulomb collision operator is kept and shown to be important for obtaining quantitative results. Bootstrap currents, parallel ion flows, and radial particle and heat fluxes show quantitative agreement between NIMROD and NEO for a variety of tokamak equilibria. In addition, velocity space distribution function contours for ions and electrons show nearly identical detailed structure and agree quantitatively. A Ī-centered, implicit time discretization and a block-preconditioned, iterative linear algebra solver provide efficient electron and ion DKE solutions that ultimately will be used to obtain closures for NIMROD's evolving fluid model.
Continuum-Coupling in Electron-Atom scattering
International Nuclear Information System (INIS)
Ballance, C.P.; Griffin, D.C.; Badnell, N.R.; Loch, S.D.; Pindzola, M.S.
2004-01-01
High quality fundamental atomic data provide the foundation of accurate collisional-radiative models of laboratory and astrophysical plasmas. In the SciDAC (Scientific Discovery through Advanced Computing) project entitled 'Terascale Computational Atomic Physics for the Edge Region in Controlled Fusion Plasmas', we employ an integrated approach from the calculation of basic atomic data to the modeling necessary for the interpretation of controlled nuclear fusion experiments. For example, helium electron-impact excitation results support helium puff experiments on the MAST (Mega Ampere Spherical Tokamak) at Culham to diagnose the radial variation in plasma density and temperature. Similarly, electron-impact excitation/ionization work for isonuclear beryllium will prove vital if beryllium is adopted as a surface material for the plasma-facing walls for ITER. Here we will discuss some examples of electron-impact excitation and ionization, where the effects of coupling to and between the target continuum states are large, and advanced close-coupling methods are required in order to generate data of sufficient accuracy
Extrapolation of lattice gauge theories to the continuum limit
International Nuclear Information System (INIS)
Duncan, A.; Vaidya, H.
1978-01-01
The problem of extrapolating lattice gauge theories from the strong-coupling phase to the continuum critical point is studied for the Abelian (U(1)) and non-Abelian (SU(2)) theories in three (space--time) dimensions. A method is described for obtaining the asymptotic behavior, for large Ī², of such thermodynamic quantities and correlation functions as the free energy and Wilson loop function. Certain general analyticity and positivity properties (in the complex Ī²-plane) are shown to lead, after appropriate analytic remappings, to a Stieltjes property of these functions. Rigorous theorems then guarantee uniform and monotone convergence of the Pade approximants, with exact pointwise upper and lower bounds. The first three Pade's are computed for both the free energy and the Wilson function. For the free energy, satisfactory agreement is with the asymptotic behavior computed by an explicit lattice calculation. The strong-coupling series for the Wilson function is found to be considerably more unstable in the lower order terms - correspondingly, convergence of the Pade's is found to be slower than in the free-energy case. It is suggested that higher-order calculations may allow a reasonably accurate determination of the string constant for the SU(2) theory. 14 references
Some remarks on recent developments in micropolar continuum theory
Vilchevskaya, E. N.; MĆ¼ller, W. H.
2018-04-01
This paper considers micropolar media that can undergo structural changes and do not a priori consist of indestructible material particles. Initially the pertinent literature is reviewed. Then the necessary theoretical framework for a continuum of that type is presented. The standard macroscopic equations for mass, linear and angular momentum are complemented by a recently proposed balance for the moment of inertia tensor, which contains a production term. Two examples illustrate the effect of the production. In the first example, we study a continuous stream of matter on a conveyor belt going through a crusher so that the total number of particles will change. In context with this example, it is also clear that the traditional Lagrangian way of describing the motion of solids is no longer adequate and must be replaced by the Eulerian point of view known from fluid mechanics. The second example deals with hollow particles which rotate because of the presence of body couples. Now a transient temperature field is superimposed such that the moment of inertia field changes due to the thermal expansion of particles. This in turn results in rotational motion that is no longer constant but varies in space and time.
A SUBMILLIMETER CONTINUUM SURVEY OF LOCAL DUST-OBSCURED GALAXIES
Energy Technology Data Exchange (ETDEWEB)
Lee, Jong Chul [Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055 (Korea, Republic of); Hwang, Ho Seong [School of Physics, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 02455 (Korea, Republic of); Lee, Gwang-Ho, E-mail: jclee@kasi.re.kr [Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of)
2016-12-20
We conduct a 350 Ī¼ m dust continuum emission survey of 17 dust-obscured galaxies (DOGs) at z = 0.05ā0.08 with the Caltech Submillimeter Observatory (CSO). We detect 14 DOGs with S{sub 350Ī¼m} = 114ā650 mJy and signal-to-noise > 3. By including two additional DOGs with submillimeter data in the literature, we are able to study dust content for a sample of 16 local DOGs, which consist of 12 bump and four power-law types. We determine their physical parameters with a two-component modified blackbody function model. The derived dust temperatures are in the range 57ā122 K and 22ā35 K for the warm and cold dust components, respectively. The total dust mass and the mass fraction of the warm dust component are 3ā34Ā ĆĀ 10{sup 7} M {sub ā} and 0.03%ā2.52%, respectively. We compare these results with those of other submillimeter-detected infrared luminous galaxies. The bump DOGs, the majority of the DOG sample, show similar distributions of dust temperatures and total dust mass to the comparison sample. The power-law DOGs show a hint of smaller dust masses than other samples, but need to be tested with a larger sample. These findings support that the reason DOGs show heavy dust obscuration is not an overall amount of dust content, but probably the spatial distribution of dust therein.
On a Continuum Limit for Loop Quantum Cosmology
International Nuclear Information System (INIS)
Corichi, Alejandro; Vukasinac, Tatjana; Zapata, Jose Antonio
2008-01-01
The use of non-regular representations of the Heisenberg-Weyl commutation relations has proved to be useful for studying conceptual and technical issues in quantum gravity. Of particular relevance is the study of Loop Quantum Cosmology (LQC), symmetry reduced theory that is related to Loop Quantum Gravity, and that is based on a non-regular, polymeric representation. Recently, a soluble model was used by Ashtekar, Corichi and Singh to study the relation between Loop Quantum Cosmology and the standard Wheeler-DeWitt theory and, in particular, the passage to the limit in which the auxiliary parameter (interpreted as ''quantum geometry discreetness'') is sent to zero in hope to get rid of this 'regulator' that dictates the LQC dynamics at each 'scale'. In this note we outline the first steps toward reformulating this question within the program developed by the authors for studying the continuum limit of polymeric theories, which was successfully applied to simple systems such as a Simple Harmonic Oscillator
Neoclassical Simulation of Tokamak Plasmas using Continuum Gyrokinetc Code TEMPEST
International Nuclear Information System (INIS)
Xu, X Q
2007-01-01
We present gyrokinetic neoclassical simulations of tokamak plasmas with self-consistent electric field for the first time using a fully nonlinear (full-f) continuum code TEMPEST in a circular geometry. A set of gyrokinetic equations are discretized on a five dimensional computational grid in phase space. The present implementation is a Method of Lines approach where the phase-space derivatives are discretized with finite differences and implicit backwards differencing formulas are used to advance the system in time. The fully nonlinear Boltzmann model is used for electrons. The neoclassical electric field is obtained by solving gyrokinetic Poisson equation with self-consistent poloidal variation. With our 4D (Ļ, Īø, Īµ, Ī¼) version of the TEMPEST code we compute radial particle and heat flux, the Geodesic-Acoustic Mode (GAM), and the development of neoclassical electric field, which we compare with neoclassical theory with a Lorentz collision model. The present work provides a numerical scheme and a new capability for self-consistently studying important aspects of neoclassical transport and rotations in toroidal magnetic fusion devices
Aggregation patterns from nonlocal interactions: Discrete stochastic and continuum modeling
Hackett-Jones, Emily J.
2012-04-17
Conservation equations governed by a nonlocal interaction potential generate aggregates from an initial uniform distribution of particles. We address the evolution and formation of these aggregating steady states when the interaction potential has both attractive and repulsive singularities. Currently, no existence theory for such potentials is available. We develop and compare two complementary solution methods, a continuous pseudoinverse method and a discrete stochastic lattice approach, and formally show a connection between the two. Interesting aggregation patterns involving multiple peaks for a simple doubly singular attractive-repulsive potential are determined. For a swarming Morse potential, characteristic slow-fast dynamics in the scaled inverse energy is observed in the evolution to steady state in both the continuous and discrete approaches. The discrete approach is found to be remarkably robust to modifications in movement rules, related to the potential function. The comparable evolution dynamics and steady states of the discrete model with the continuum model suggest that the discrete stochastic approach is a promising way of probing aggregation patterns arising from two- and three-dimensional nonlocal interaction conservation equations. Ā© 2012 American Physical Society.
Continuum model for chiral induced spin selectivity in helical molecules
Energy Technology Data Exchange (ETDEWEB)
Medina, Ernesto [Centro de FĆsica, Instituto Venezolano de Investigaciones CientĆficas, 21827, Caracas 1020 A (Venezuela, Bolivarian Republic of); Groupe de Physique Statistique, Institut Jean Lamour, UniversitĆ© de Lorraine, 54506 Vandoeuvre-les-Nancy Cedex (France); Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287 (United States); GonzĆ”lez-Arraga, Luis A. [IMDEA Nanoscience, Cantoblanco, 28049 Madrid (Spain); Finkelstein-Shapiro, Daniel; Mujica, Vladimiro [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287 (United States); Berche, Bertrand [Centro de FĆsica, Instituto Venezolano de Investigaciones CientĆficas, 21827, Caracas 1020 A (Venezuela, Bolivarian Republic of); Groupe de Physique Statistique, Institut Jean Lamour, UniversitĆ© de Lorraine, 54506 Vandoeuvre-les-Nancy Cedex (France)
2015-05-21
A minimal model is exactly solved for electron spin transport on a helix. Electron transport is assumed to be supported by well oriented p{sub z} type orbitals on base molecules forming a staircase of definite chirality. In a tight binding interpretation, the spin-orbit coupling (SOC) opens up an effective Ļ{sub z} ā Ļ{sub z} coupling via interbase p{sub x,y} ā p{sub z} hopping, introducing spin coupled transport. The resulting continuum model spectrum shows two Kramers doublet transport channels with a gap proportional to the SOC. Each doubly degenerate channel satisfies time reversal symmetry; nevertheless, a bias chooses a transport direction and thus selects for spin orientation. The model predicts (i) which spin orientation is selected depending on chirality and bias, (ii) changes in spin preference as a function of input Fermi level and (iii) back-scattering suppression protected by the SO gap. We compute the spin current with a definite helicity and find it to be proportional to the torsion of the chiral structure and the non-adiabatic Aharonov-Anandan phase. To describe room temperature transport, we assume that the total transmission is the result of a product of coherent steps.
HIV seroprevalence across the rural/urban continuum.
McCoy, C B; Metsch, L R; McCoy, H V; Weatherby, N L
1999-01-01
While the first decade of the AIDS epidemic was characterized by high prevalence rates of AIDS infection in urban areas, there is increasing recognition of the spread of HIV into rural communities in the United States. Data from the Miami CARES cohort collected on 3,555 chronic drug users from 1988 to 1994 provide a unique opportunity to assess sociodemographic characteristics, drug-using behaviors and HIV risk behaviors related to HIV seropositivity in three communities across the rural-urban continuum: Miami, Florida; Belle Glade, Florida and Immokalee, Florida. The three very different communities studied demonstrate that HIV is no respecter of ecological site. The spread of HIV between areas and within areas is specifically correlated with the risk factors including injection drug use, use of crack cocaine, exchange of sex for money, and the rates for sexually transmitted diseases. All of these factors are shown to increase the risk of HIV so that the constellation of these practices helps determine the differential rates and spread of HIV in the three different areas.
Continuum modelling of segregating tridisperse granular chute flow
Deng, Zhekai; Umbanhowar, Paul B.; Ottino, Julio M.; Lueptow, Richard M.
2018-03-01
Segregation and mixing of size multidisperse granular materials remain challenging problems in many industrial applications. In this paper, we apply a continuum-based model that captures the effects of segregation, diffusion and advection for size tridisperse granular flow in quasi-two-dimensional chute flow. The model uses the kinematics of the flow and other physical parameters such as the diffusion coefficient and the percolation length scale, quantities that can be determined directly from experiment, simulation or theory and that are not arbitrarily adjustable. The predictions from the model are consistent with experimentally validated discrete element method (DEM) simulations over a wide range of flow conditions and particle sizes. The degree of segregation depends on the PĆ©clet number, Pe, defined as the ratio of the segregation rate to the diffusion rate, the relative segregation strength Īŗij between particle species i and j, and a characteristic length L, which is determined by the strength of segregation between smallest and largest particles. A parametric study of particle size, Īŗij, Pe and L demonstrates how particle segregation patterns depend on the interplay of advection, segregation and diffusion. Finally, the segregation pattern is also affected by the velocity profile and the degree of basal slip at the chute surface. The model is applicable to different flow geometries, and should be easily adapted to segregation driven by other particle properties such as density and shape.
Gyrokinetic continuum simulations of turbulence in the Texas Helimak
Bernard, T. N.; Shi, E. L.; Hammett, G. W.; Hakim, A.; Taylor, E. I.
2017-10-01
We have used the Gkeyll code to perform 3x-2v full-f gyrokinetic continuum simulations of electrostatic plasma turbulence in the Texas Helimak. The Helimak is an open field-line experiment with magnetic curvature and shear. It is useful for validating numerical codes due to its extensive diagnostics and simple, helical geometry, which is similar to the scrape-off layer region of tokamaks. Interchange and drift-wave modes are the main turbulence mechanisms in the device, and potential biasing is applied to study the effect of velocity shear on turbulence reduction. With Gkeyll, we varied field-line pitch angle and simulated biased and unbiased cases to study different turbulent regimes and turbulence reduction. These are the first kinetic simulations of the Helimak and resulting plasma profiles agree fairly well with experimental data. This research demonstrates Gkeyll's progress towards 5D simulations of the SOL region of fusion devices. Supported by the U.S. DOE SCGSR program under contract DE-SC0014664, the Max-Planck/Princeton Center for Plasma Physics, the SciDAC Center for the Study of Plasma Microturbulence, and DOE contract DE-AC02-09CH11466.
A continuum mechanics constitutive framework for transverse isotropic soft tissues
Garcia-Gonzalez, D.; JĆ©rusalem, A.; Garzon-Hernandez, S.; Zaera, R.; Arias, A.
2018-03-01
In this work, a continuum constitutive framework for the mechanical modelling of soft tissues that incorporates strain rate and temperature dependencies as well as the transverse isotropy arising from fibres embedded into a soft matrix is developed. The constitutive formulation is based on a Helmholtz free energy function decoupled into the contribution of a viscous-hyperelastic matrix and the contribution of fibres introducing dispersion dependent transverse isotropy. The proposed framework considers finite deformation kinematics, is thermodynamically consistent and allows for the particularisation of the energy potentials and flow equations of each constitutive branch. In this regard, the approach developed herein provides the basis on which specific constitutive models can be potentially formulated for a wide variety of soft tissues. To illustrate this versatility, the constitutive framework is particularised here for animal and human white matter and skin, for which constitutive models are provided. In both cases, different energy functions are considered: Neo-Hookean, Gent and Ogden. Finally, the ability of the approach at capturing the experimental behaviour of the two soft tissues is confirmed.
Ovarian dysfunction, stress, and disease: a primate continuum.
Kaplan, Jay R; Manuck, Stephen B
2004-01-01
Menopause is recognized as a period of increased risk for coronary heart disease (CHD) and osteoporosis. Vulnerability to these conditions is often attributed to the naturally occurring estrogen deficiency characteristic of this part of the life cycle. Premenopausal reductions in endogenous estrogen occasioned by functional ovarian abnormalities or failure are hypothesized to be similarly pathogenic and to accelerate development of CHD and osteoporosis prematurely, thereby increasing the health burden of older women. These functional abnormalities, which occur along a continuum from mild, luteal phase progesterone deficiency to amenorrhea, are relatively common and are often attributed to psychogenic factors (stress, anxiety, depression, or other emotional disturbance), exercise, or energy imbalance. Although numerous investigators have commented on these functional deficits, the abnormalities can be difficult to diagnose and are generally unappreciated for the contribution they may make to postmenopausal disease. Studies in nonhuman primates confirm that these deficits are easily induced by psychological stress and exercise, and that they accelerate the development of cardiovascular disease and perhaps bone loss in the presence of a typical North American diet. However, functional reproductive deficits are also reversible and are thus potentially amenable to environmental or behavioral intervention. Data from both women and nonhuman primates support the hypothesis that functional reproductive deficits are adaptive when triggered appropriately but are detrimental when activated in an environment (e.g., sedentary lifestyle, high-fat diet) permissive to the development of chronic disease.
Microvasular and macrovascular complications in diabetes mellitus: Distinct or continuum?
Directory of Open Access Journals (Sweden)
Aastha Chawla
2016-01-01
Full Text Available Diabetes and related complications are associated with long-term damage and failure of various organ systems. The line of demarcation between the pathogenic mechanisms of microvascular and macrovascular complications of diabetes and differing responses to therapeutic interventions is blurred. Diabetes induces changes in the microvasculature, causing extracellular matrix protein synthesis, and capillary basement membrane thickening which are the pathognomic features of diabetic microangiopathy. These changes in conjunction with advanced glycation end products, oxidative stress, low grade inflammation, and neovascularization of vasa vasorum can lead to macrovascular complications. Hyperglycemia is the principal cause of microvasculopathy but also appears to play an important role in causation of macrovasculopathy. There is thought to be an intersection between micro and macro vascular complications, but the two disorders seem to be strongly interconnected, with micro vascular diseases promoting atherosclerosis through processes such as hypoxia and changes in vasa vasorum. It is thus imperative to understand whether microvascular complications distinctly precede macrovascular complications or do both of them progress simultaneously as a continuum. This will allow re-focusing on the clinical issues with a unifying perspective which can improve type 2 diabetes mellitus outcomes.
Morphing continuum analysis of energy transfer in compressible turbulence
Cheikh, Mohamad Ibrahim; Wonnell, Louis B.; Chen, James
2018-02-01
A shock-preserving finite volume solver with the generalized Lax-Friedrichs splitting flux for morphing continuum theory (MCT) is presented and verified. The numerical MCT solver is showcased in a supersonic turbulent flow with Mach 2.93 over an 8ā compression ramp. The simulation results validated MCT with experiments as an alternative for modeling compressible turbulence. The required size of the smallest mesh cell for the MCT simulation is shown to be almost an order larger than that in a similar direct numerical simulation study. The comparison shows MCT is a much more computationally friendly theory than the classical Navier-Stokes equations. The dynamics of energy cascade at the length scale of individual eddies is illuminated through the subscale rotation introduced by MCT. In this regard, MCT provides a statistical averaging procedure for capturing energy transfer in compressible turbulence, not found in classical fluid theories. Analysis of the MCT results show the existence of a statistical coupling of the internal and translational kinetic energy fluctuations with the corresponding eddy rotational energy fluctuations, indicating a multiscale transfer of energy. In conclusion, MCT gives a new characterization of the energy cascade within compressible turbulence without the use of excessive computational resources.
6d holographic anomaly match as a continuum limit
Energy Technology Data Exchange (ETDEWEB)
Cremonesi, Stefano [Department of Mathematics, Kingās College London, The Strand, London WC2R 2LS (United Kingdom); Tomasiello, Alessandro [Dipartimento di Fisica, UniversitĆ di Milano-Bicocca, and INFN, sezione di Milano-Bicocca,Piazza della Scienza 3, I-20126 Milano (Italy)
2016-05-05
An infinite class of analytic AdS{sub 7}ĆS{sup 3} solutions has recently been found. The S{sup 3} is distorted into a ācrescent rollā shape by the presence of D8-branes. These solutions are conjectured to be dual to a class of ālinear quiversā, with a large number of gauge groups coupled to (bi-)fundamental matter and tensor fields. In this paper we perform a precise quantitative check of this correspondence, showing that the a Weyl anomalies computed in field theory and gravity agree. In the holographic limit, where the number of gauge groups is large, the field theory result is a quadratic form in the gauge group ranks involving the inverse of the A{sub N} Cartan matrix C. The agreement can be understood as a continuum limit, using the fact that C is a lattice analogue of a second derivative. The discrete data of the field theory, summarized by two partitions, become in this limit the continuous functions in the geometry. Conversely, the geometry of the internal space gets discretized at the quantum level to the discrete data of the two partitions.
A SUBMILLIMETER CONTINUUM SURVEY OF LOCAL DUST-OBSCURED GALAXIES
International Nuclear Information System (INIS)
Lee, Jong Chul; Hwang, Ho Seong; Lee, Gwang-Ho
2016-01-01
We conduct a 350 Ī¼ m dust continuum emission survey of 17 dust-obscured galaxies (DOGs) at z = 0.05ā0.08 with the Caltech Submillimeter Observatory (CSO). We detect 14 DOGs with S 350Ī¼m = 114ā650 mJy and signal-to-noise > 3. By including two additional DOGs with submillimeter data in the literature, we are able to study dust content for a sample of 16 local DOGs, which consist of 12 bump and four power-law types. We determine their physical parameters with a two-component modified blackbody function model. The derived dust temperatures are in the range 57ā122 K and 22ā35 K for the warm and cold dust components, respectively. The total dust mass and the mass fraction of the warm dust component are 3ā34Ā ĆĀ 10 7 M ā and 0.03%ā2.52%, respectively. We compare these results with those of other submillimeter-detected infrared luminous galaxies. The bump DOGs, the majority of the DOG sample, show similar distributions of dust temperatures and total dust mass to the comparison sample. The power-law DOGs show a hint of smaller dust masses than other samples, but need to be tested with a larger sample. These findings support that the reason DOGs show heavy dust obscuration is not an overall amount of dust content, but probably the spatial distribution of dust therein.
A framework of teaching competencies across the medical education continuum.
Molenaar, W M; Zanting, A; van Beukelen, P; de Grave, W; Baane, J A; Bustraan, J A; Engbers, R; Fick, Th E; Jacobs, J C G; Vervoorn, J M
2009-05-01
The quality of teachers in higher education is subject of increasing attention, as exemplified by the development and implementation of guidelines for teacher qualifications at Universities in The Netherlands. Because medical education takes a special position in higher education the Council of Deans of Medical Schools in The Netherlands installed a national task force to explore a method to weigh criteria for teacher qualifications of medical teachers. A framework was developed covering competencies of teachers throughout the medical education continuum and including medicine, dentistry and veterinary medicine. The framework distinguishes 3 dimensions: (a) six domains of teaching (development - organization - execution - coaching - assessment - evaluation); (b) three levels in the organization at which teachers perform (micro, meso and macro level) and (c) competencies as integration of knowledge, skills and attitude and described as behaviour in specific context. The current framework is the result of several cycles of descriptions, feedback from the field and adaptations. It is meant as a guideline, leaving room for local detailing. The framework provides a common language that may be used not only by teachers and teacher trainers, but also by quality assurance committees, human resource managers and institutional boards.
STATCONT: A statistical continuum level determination method for line-rich sources
SĆ”nchez-Monge, Ć.; Schilke, P.; Ginsburg, A.; Cesaroni, R.; Schmiedeke, A.
2018-01-01
STATCONT is a python-based tool designed to determine the continuum emission level in spectral data, in particular for sources with a line-rich spectrum. The tool inspects the intensity distribution of a given spectrum and automatically determines the continuum level by using different statistical approaches. The different methods included in STATCONT are tested against synthetic data. We conclude that the sigma-clipping algorithm provides the most accurate continuum level determination, together with information on the uncertainty in its determination. This uncertainty can be used to correct the final continuum emission level, resulting in the here called `corrected sigma-clipping method' or c-SCM. The c-SCM has been tested against more than 750 different synthetic spectra reproducing typical conditions found towards astronomical sources. The continuum level is determined with a discrepancy of less than 1% in 50% of the cases, and less than 5% in 90% of the cases, provided at least 10% of the channels are line free. The main products of STATCONT are the continuum emission level, together with a conservative value of its uncertainty, and datacubes containing only spectral line emission, i.e., continuum-subtracted datacubes. STATCONT also includes the option to estimate the spectral index, when different files covering different frequency ranges are provided.
Energy Technology Data Exchange (ETDEWEB)
Hoogenboom, J.E. (Technische Hogeschool Delft (Netherlands))
1983-01-01
From the collision mechanics of inelastic discrete-level scattering several properties are derived for the secondary-neutron energy distribution (SNED) for inelastic continuum scattering, when conceived as scattering with continuously-distributed inelastic levels. Using assumptions about the level density and neutron cross section the SNED can be calculated and some examples are shown. A formula is derived to calculate from a given inelastic continuum SNED a function, which is proportional to the level density and the neutron cross section. From this relation further conditions follow for the SNED. Representations for the inelastic continuum SNED currently in use do not, in general, satisfy most of the derived conditions.
International Nuclear Information System (INIS)
Hoogenboom, J.E.
1983-01-01
From the collision mechanics of inelastic discrete-level scattering several properties are derived for the secondary-neutron energy distribution (SNED) for inelastic continuum scattering, when conceived as scattering with continuously-distributed inelastic levels. Using assumptions about the level density and neutron cross section the SNED can be calculated and some examples are shown. A formula is derived to calculate from a given inelastic continuum SNED a function, which is proportional to the level density and the neutron cross section. From this relation further conditions follow for the SNED. Representations for the inelastic continuum SNED currently in use do not, in general, satisfy most of the derived conditions. (author)
International Nuclear Information System (INIS)
Brus, V V
2013-01-01
A quantitative analysis of the impedance spectroscopy of semiconductor heterojunctions was carried out in the presence of interface state continuum at the heterojunction interface. A comparison of the impedance spectroscopy of semiconductor heterojunctions simulated in the context of the interface state continuum model with that simulated in the scope of the single-level state model was carried and possible misinterpretations were considered. The previously proposed approaches for the determination of the interface-state-related parameters and for the calculation of the actual barrier capacitance (the single-level state model) were modified in order to take into account the effect of interface state continuum. (paper)
Treatment of continuum in weakly bound systems in structure and reactions
Energy Technology Data Exchange (ETDEWEB)
Vitturi, Andrea [Dipartimento di Fisica and INFN, Padova (Italy); Perez-Bernal, Francisco [Facultad de Ciencias Experimentales, Departamento de Fisica Aplicada, Universidad de Huelva, Huelva (Spain)
2010-03-01
We investigate different treatments of continuum states in a simple structure case: two particles moving in a one-dimensional mean field and interacting via a density-dependent short range residual interaction. We find that in procedures that involve continuum discretization a rather large basis has to be used in order to get convergence to the exact results, in particular for the radial dependence of the two-particle wave function. This may lead to unpracticable situations in the case of many interacting particles in the continuum.
Accidental bound states in the continuum in an open Sinai billiard
Energy Technology Data Exchange (ETDEWEB)
Pilipchuk, A.S. [Kirensky Institute of Physics, Federal Research Center KSC SB RAS, 660036 Krasnoyarsk (Russian Federation); Siberian Federal University, 660080 Krasnoyarsk (Russian Federation); Sadreev, A.F., E-mail: almas@tnp.krasn.ru [Kirensky Institute of Physics, Federal Research Center KSC SB RAS, 660036 Krasnoyarsk (Russian Federation)
2017-02-19
The fundamental mechanism of the bound states in the continuum is the full destructive interference of two resonances when two eigenlevels of the closed system are crossing. There is, however, a wide class of quantum chaotic systems which display only avoided crossings of eigenlevels. As an example of such a system we consider the Sinai billiard coupled with two semi-infinite waveguides. We show that notwithstanding the absence of degeneracy bound states in the continuum occur due to accidental decoupling of the eigenstates of the billiard from the waveguides. - Highlights: ā¢ Bound states in the continuum in open chaotic billiards occur to accidental vanishing of coupling of eigenstate of billiard with waveguides.
Non-classical solutions of a continuum model for rock descriptions
Directory of Open Access Journals (Sweden)
Mikhail A. Guzev
2014-06-01
Full Text Available The strain-gradient and non-Euclidean continuum theories are employed for construction of non-classical solutions of continuum models. The linear approximation of both models' results in identical structures in terms of their kinematic and stress characteristics. The solutions obtained in this study exhibit a critical behaviour with respect to the external loading parameter. The conclusions are obtained based on an investigation of the solution for the scalar curvature in the non-Euclidean continuum theory. The proposed analysis enables us to use different theoretical approaches for description of rock critical behaviour under different loading conditions.
Fierstein, J.; Wilson, C.J.N.
2005-01-01
The 1912 Valley of Ten Thousand Smokes (VTTS) ignimbrite was constructed from 9 compositionally distinct, sequentially emplaced packages, each with distinct proportions of rhyolite (R), dacite (D), and andesite (A) pumices that permit us to map package boundaries and flow paths from vent to distal extents. Changing pumice proportions and interbedding relationships link ignimbrite formation to coeval fall deposition during the first ???16 h (Episode I) of the eruption. Pumice compositional proportions in the ignimbrite were estimated by counts on ???100 lapilli at multiple levels in vertical sections wherever accessible and more widely over most of the ignimbrite surface in the VTTS. The initial, 100% rhyolite ignimbrite package (equivalent to regional fall Layer A and occupying ???3.5 h) was followed by packages with increasing proportions of andesite, then dacite, emplaced over ???12.5 h and equivalent to regional fall Layers B1-B3. Coeval fall deposits are locally intercalated with the ignimbrite and show parallel changes in R:D (rhyolite:dacite) proportions, but lack significant amounts of andesite. Andesite was thus dominantly a low-fountaining component in the eruption column and is preferentially represented in packages filling the VTTS north of the vent. The most extensive packages (3 and 4) occur in B1 and early B2 times where flow mobility and volume were optimized; earlier all-rhyolite flows (Package 1) were highly energetic but less voluminous, while later packages (5-9) were both less voluminous and emplaced at lower velocities. Package boundaries are expressed as one or more of the following: sharp color changes corresponding to compositional variations; persistent finer-grained basal parts of flow units; compaction swales filled by later packages; erosional channels cut by the flows that fill them; lobate accumulations of one package; and (mostly south of the vent) intercalated fall deposit layers. Clear flow-unit boundaries are best developed between
Phosphorus Dynamics along River Continuum during Typhoon Storm Events
Directory of Open Access Journals (Sweden)
Ming Fai Chow
2017-07-01
Full Text Available Information on riverine phosphorus (P dynamics during typhoon storm events remains scarce in subtropical regions. Thus, this study investigates the spatial and temporal dynamics of riverine phosphorus in a headwater catchment during three typhoon events. Continuous sampling (3 h intervals of stormwater samples and discharge data were conducted at five locations, which represent the upstream, transitional zone, and downstream areas of the main inflow river. The results revealed that the average event mean concentrations (EMCs for total dissolved phosphorus (TDP and particulate phosphorus (PP in the upstream catchment of Fei-Tsui reservoir were 15.66 Ī¼g/L and 11.94 Ī¼g/L, respectively. There was at least a 1.3-fold increase in flow-weighted concentrations of TDP and PP from the upper to lower reaches of the main stream. PP and TDP were transported either in clockwise or anticlockwise directions, depending on storm intensity and source. The transport of TDP was primarily regulated by the subsurface flow during the storm event. Soluble reactive phosphorus (SRP contributes more than 50% of the TDP load in moderate storms, while extreme storms supply a greater dissolved organic phosphorus (DOP load into the stream. TDP accounted for approximately 50% of TP load during typhoon storms. Mobilization of all P forms was observed from upstream to downstream of the river, except for DOP. A decrease of DOP load on passing downstream may reflect the change in phosphorus form along the river continuum. Peak discharge and antecedent dry days are correlated positively with P fluxes, indicating that river bank erosion and re-suspension of within-channel sediment are the dominant pathways of P during typhoon storm periods.
Understanding Stoichiometric Controls in Nutrient Processing Along the River Continuum
Garayburu-Caruso, V. A.; Gonzalez-Pinzon, R.; Van Horn, D. J.; Covino, T. P.
2016-12-01
Eutrophication is the second most common cause of water impairment across the U.S. Nutrient retention in streams is controlled by physical and biochemical processes, including biomass availability and stoichiometric limitations. Decoupling the interactions between hydrology, nutrient supply and biogeochemical processes remains challenging for the scientific community due to lack of mechanistic understanding. Consequently, more knowledge regarding optimal controls for nutrient retention is needed to implement better management and restoration practices. We conducted column experiments to investigate how stoichiometric limitations influence nutrient spiraling in shallow sediment-water interactions along representative sites of the Jemez River-Rio Grande continuum (which spans eight stream orders), in New Mexico, USA. In each stream order we incubated six columns packed with different sediments (i.e., Silica Cone Density Sand ASTM D 1556 (0.075-2.00 mm), gravel (>2mm) and native sediments) from each site for three months. We performed two laboratory tracer experiments using columns of each substrate under identical flow conditions. In the first experiment we added a short-term pulse of reactive and conservative tracers (i.e. NaNO3 and NaBr). In the second experiment we added a short-term pulse of NaBr and nutrients following Redfield's ratio (106C:16N:1P). We estimated uptake kinetics using the Tracer Additions for Spiraling Curve Characterization (TASCC) method and evaluated how ideal stoichiometric conditions controlled efficient nutrient retention along fluvial networks. Our results suggest that biological uptake of nitrate is limited by nitrogen in headwater streams and by phosphorus and carbon in larger stream orders.
SR 97. Alternative models project. Stochastic continuum modelling of Aberg
International Nuclear Information System (INIS)
Widen, H.; Walker, D.
1999-08-01
As part of studies into the siting of a deep repository for nuclear waste, Swedish Nuclear Fuel and Waste Management Company (SKB) has commissioned the Alternative Models Project (AMP). The AMP is a comparison of three alternative modelling approaches to bedrock performance assessment for a single hypothetical repository, arbitrarily named Aberg. The Aberg repository will adopt input parameters from the Aespoe Hard Rock Laboratory in southern Sweden. The models are restricted to an explicit domain, boundary conditions and canister location to facilitate the comparison. The boundary conditions are based on the regional groundwater model provided in digital format. This study is the application of HYDRASTAR, a stochastic continuum groundwater flow and transport-modelling program. The study uses 34 realisations of 945 canister locations in the hypothetical repository to evaluate the uncertainty of the advective travel time, canister flux (Darcy velocity at a canister) and F-ratio. Several comparisons of variability are constructed between individual canister locations and individual realisations. For the ensemble of all realisations with all canister locations, the study found a median travel time of 27 years, a median canister flux of 7.1 x 10 -4 m/yr and a median F-ratio of 3.3 x 10 5 yr/m. The overall pattern of regional flow is preserved in the site-scale model, as is reflected in flow paths and exit locations. The site-scale model slightly over-predicts the boundary fluxes from the single realisation of the regional model. The explicitly prescribed domain was seen to be slightly restrictive, with 6% of the stream tubes failing to exit the upper surface of the model. Sensitivity analysis and calibration are suggested as possible extensions of the modelling study
RESOLUTION OF THE COMPACT RADIO CONTINUUM SOURCES IN Arp220
International Nuclear Information System (INIS)
Batejat, Fabien; Conway, John E.; Hurley, Rossa; Parra, Rodrigo; Diamond, Philip J.; Lonsdale, Colin J.; Lonsdale, Carol J.
2011-01-01
We present 2 cm and 3.6 cm wavelength very long baseline interferometry images of the compact radio continuum sources in the nearby ultra-luminous infrared galaxy Arp220. Based on their radio spectra and variability properties, we confirm these sources to be a mixture of supernovae (SNe) and supernova remnants (SNRs). Of the 17 detected sources we resolve 7 at both wavelengths. The SNe generally only have upper size limits. In contrast all the SNRs are resolved with diameters ā„0.27 pc. This size limit is consistent with them having just entered their Sedov phase while embedded in an interstellar medium (ISM) of density 10 4 cm -3 . These objects lie on the diameter-luminosity correlation for SNRs (and so also on the diameter-surface brightness relation) and extend these correlations to very small sources. The data are consistent with the relation LāD -9/4 . Revised equipartition arguments adjusted to a magnetic field to a relativistic particle energy density ratio of 1% combined with a reasonable synchrotron-emitting volume filling factor of 10% give estimated magnetic field strengths in the SNR shells of ā¼15-50 mG. The SNR shell magnetic fields are unlikely to come from compression of ambient ISM fields and must instead be internally generated. We set an upper limit of 7 mG for the ISM magnetic field. The estimated energy in relativistic particles, 2%-20% of the explosion kinetic energy, is consistent with estimates from models that fit the IR-radio correlation in compact starburst galaxies.
A comparison of approaches in fitting continuum SEDs
International Nuclear Information System (INIS)
Liu Yao; Wang Hong-Chi; Madlener David; Wolf Sebastian
2013-01-01
We present a detailed comparison of two approaches, the use of a pre-calculated database and simulated annealing (SA), for fitting the continuum spectral energy distribution (SED) of astrophysical objects whose appearance is dominated by surrounding dust. While pre-calculated databases are commonly used to model SED data, only a few studies to date employed SA due to its unclear accuracy and convergence time for this specific problem. From a methodological point of view, different approaches lead to different fitting quality, demand on computational resources and calculation time. We compare the fitting quality and computational costs of these two approaches for the task of SED fitting to provide a guide to the practitioner to find a compromise between desired accuracy and available resources. To reduce uncertainties inherent to real datasets, we introduce a reference model resembling a typical circumstellar system with 10 free parameters. We derive the SED of the reference model with our code MC3 D at 78 logarithmically distributed wavelengths in the range [0.3 Ī¼m, 1.3 mm] and use this setup to simulate SEDs for the database and SA. Our result directly demonstrates the applicability of SA in the field of SED modeling, since the algorithm regularly finds better solutions to the optimization problem than a pre-calculated database. As both methods have advantages and shortcomings, a hybrid approach is preferable. While the database provides an approximate fit and overall probability distributions for all parameters deduced using Bayesian analysis, SA can be used to improve upon the results returned by the model grid.
A continuum mathematical model of endothelial layer maintenance and senescence
Directory of Open Access Journals (Sweden)
Friedman Avner
2007-08-01
Full Text Available Abstract Background The monolayer of endothelial cells (ECs lining the inner wall of blood vessels deteriorates as a person ages due to a complex interplay of a variety of causes including cell death arising from shear stress of blood flow and cellular oxidative stress, cellular senescence, and decreased rate of replacement of dead ECs by progenitor stem cells. Results A continuum mathematical model is developed to describe the dynamics of large EC populations of the endothelium using a system of differential equations for the number densities of cells of different generations starting from endothelial progenitors to senescent cells, as well as the densities of dead cells and the holes created upon clearing dead cells. Aging of cells is manifested in three ways, namely, losing the ability to divide when the Hayflick limit of 50 generations is reached, decreasing replication rate parameters and increasing death rate parameters as cells divide; due to the dependence of these rate parameters on cell generation, the model predicts a narrow distribution of cell densities peaking at a particular cell generation. As the chronological age of a person advances, the peak of the distribution ā corresponding to the age of the endothelium ā moves towards senescence correspondingly. However, computer simulations also demonstrate that sustained and enhanced stem cell homing can halt the aging process of the endothelium by maintaining a stationary cell density distribution that peaks well before the Hayflick limit. The healing rates of damaged endothelia for young, middle-aged, and old persons are compared and are found to be particularly sensitive to the stem cell homing parameter. Conclusion The proposed model describes the aging of the endothelium as being driven by cellular senescence, with a rate that does not necessarily correspond to the chronological aging of a person. It is shown that the age of the endothelium depends sensitively on the homing
A continuum mathematical model of endothelial layer maintenance and senescence.
Wang, Ying; Aguda, Baltazar D; Friedman, Avner
2007-08-10
The monolayer of endothelial cells (ECs) lining the inner wall of blood vessels deteriorates as a person ages due to a complex interplay of a variety of causes including cell death arising from shear stress of blood flow and cellular oxidative stress, cellular senescence, and decreased rate of replacement of dead ECs by progenitor stem cells. A continuum mathematical model is developed to describe the dynamics of large EC populations of the endothelium using a system of differential equations for the number densities of cells of different generations starting from endothelial progenitors to senescent cells, as well as the densities of dead cells and the holes created upon clearing dead cells. Aging of cells is manifested in three ways, namely, losing the ability to divide when the Hayflick limit of 50 generations is reached, decreasing replication rate parameters and increasing death rate parameters as cells divide; due to the dependence of these rate parameters on cell generation, the model predicts a narrow distribution of cell densities peaking at a particular cell generation. As the chronological age of a person advances, the peak of the distribution - corresponding to the age of the endothelium - moves towards senescence correspondingly. However, computer simulations also demonstrate that sustained and enhanced stem cell homing can halt the aging process of the endothelium by maintaining a stationary cell density distribution that peaks well before the Hayflick limit. The healing rates of damaged endothelia for young, middle-aged, and old persons are compared and are found to be particularly sensitive to the stem cell homing parameter. The proposed model describes the aging of the endothelium as being driven by cellular senescence, with a rate that does not necessarily correspond to the chronological aging of a person. It is shown that the age of the endothelium depends sensitively on the homing rates of EC progenitor cells.
The Q Continuum: Encounter with the Cloud Mask
Ackerman, S. A.; Frey, R.; Holz, R.; Philips, C.; Dutcher, S.
2017-12-01
We are developing a common cloud mask for MODIS and VIIRS observations, referred to as the MODIS VIIRS Continuity Mask (MVCM). Our focus is on extending the MODIS-heritage cloud detection approach in order to generate appropriate climate data records for clouds and climate studies. The MVCM is based on heritage from the MODIS cloud mask (MOD35 and MYD35) and employs a series of tests on MODIS reflectances and brightness temperatures. Cloud detection is based on contrasts (i.e., cloud versus background surface) at pixel resolution. The MVCM follows the same approach. These cloud masks use multiple cloud detection tests to indicate the confidence level that the observation is of a clear-sky scene. The outcome of a test ranges from 0 (cloudy) to 1 (clear-sky scene). Because of overlap in the sensitivities of the various spectral tests to the type of cloud, each test is considered in one of several groups. The final cloud mask is determined from the product of the minimum confidence of each group and is referred to as the Q value as defined in Ackerman et al (1998). In MOD35 and MYD35 processing, the Q value is not output, rather predetermined Q values determine the result: If Q ā„ .99 the scene is clear; .95 ā¤ Q laws of physics are followed, at least according to normal human notions. Using CALIOP as representing truth, a receiver operating characteristic curve (ROC) will be analyzed to determine the optimum Q for various scenes and seasons, thus providing a continuum of discriminating thresholds.
The Novice-Expert Continuum in Astronomy Knowledge
Bryce, T. G. K.; Blown, E. J.
2012-03-01
The nature of expertise in astronomy was investigated across a broad spectrum of ages and experience in China and New Zealand. Five hypotheses (capable of quantification and statistical analysis) were used to probe types of expertise identified by previous researchers: (a) domain-specific knowledge-skill in the use of scientific vocabulary and language and recognising relationships between concepts in linguistic and schematic forms; (b) higher-order theory in terms of conceptual structure and enriched scientific knowledge and reasoning; with an expectation of cultural similarity. There were 993 participants in all, age 3-80 years, including 68 junior school pupils; 68 pre-school pupils; 112 middle-school students; 109 high-school students; 79 physics undergraduates; 60 parents; 136 pre-service primary teachers; 131 pre-service secondary teachers; 72 primary teachers; 78 secondary teachers; 50 amateur astronomers and astronomy educators; and 30 astronomers and physicists; with approximately equal numbers of each group in both cultures; and of boys and girls in the case of children. For them, the methodology utilised Piagetian interviews with three media (verbal language, drawing, play-dough modelling), and for adults a questionnaire inviting responses in writing and drawing was used. The data from each group were categorised into ordinal scales and then analysed by means of Kolmogorov-Smirnov two-sample tests. The findings supported the hypotheses with evidence of all forms of expertise increasing with experience in both cultures (Ī± level 0.05). The relative gains, overlaps and deficits in expertise across the novice-expert continuum are explored in detail.
Modeling biological tissue growth: discrete to continuum representations.
Hywood, Jack D; Hackett-Jones, Emily J; Landman, Kerry A
2013-09-01
There is much interest in building deterministic continuum models from discrete agent-based models governed by local stochastic rules where an agent represents a biological cell. In developmental biology, cells are able to move and undergo cell division on and within growing tissues. A growing tissue is itself made up of cells which undergo cell division, thereby providing a significant transport mechanism for other cells within it. We develop a discrete agent-based model where domain agents represent tissue cells. Each agent has the ability to undergo a proliferation event whereby an additional domain agent is incorporated into the lattice. If a probability distribution describes the waiting times between proliferation events for an individual agent, then the total length of the domain is a random variable. The average behavior of these stochastically proliferating agents defining the growing lattice is determined in terms of a Fokker-Planck equation, with an advection and diffusion term. The diffusion term differs from the one obtained Landman and Binder [J. Theor. Biol. 259, 541 (2009)] when the rate of growth of the domain is specified, but the choice of agents is random. This discrepancy is reconciled by determining a discrete-time master equation for this process and an associated asymmetric nonexclusion random walk, together with consideration of synchronous and asynchronous updating schemes. All theoretical results are confirmed with numerical simulations. This study furthers our understanding of the relationship between agent-based rules, their implementation, and their associated partial differential equations. Since tissue growth is a significant cellular transport mechanism during embryonic growth, it is important to use the correct partial differential equation description when combining with other cellular functions.
Integrated Information Systems Across the Weather-Climate Continuum
Pulwarty, R. S.; Higgins, W.; Nierenberg, C.; Trtanj, J.
2015-12-01
The increasing demand for well-organized (integrated) end-to-end research-based information has been highlighted in several National Academy studies, in IPCC Reports (such as the SREX and Fifth Assessment) and by public and private constituents. Such information constitutes a significant component of the "environmental intelligence" needed to address myriad societal needs for early warning and resilience across the weather-climate continuum. The next generation of climate research in service to the nation requires an even more visible, authoritative and robust commitment to scientific integration in support of adaptive information systems that address emergent risks and inform longer-term resilience strategies. A proven mechanism for resourcing such requirements is to demonstrate vision, purpose, support, connection to constituencies, and prototypes of desired capabilities. In this presentation we will discuss efforts at NOAA, and elsewhere, that: Improve information on how changes in extremes in key phenomena such as drought, floods, and heat stress impact management decisions for resource planning and disaster risk reduction Develop regional integrated information systems to address these emergent challenges, that integrate observations, monitoring and prediction, impacts assessments and scenarios, preparedness and adaptation, and coordination and capacity-building. Such systems, as illustrated through efforts such as NIDIS, have strengthened the integration across the foundational research enterprise (through for instance, RISAs, Modeling Analysis Predictions and Projections) by increasing agility for responding to emergent risks. The recently- initiated Climate Services Information System, in support of the WMO Global Framework for Climate Services draws on the above models and will be introduced during the presentation.
A constitutive model of soft tissue: From nanoscale collagen to tissue continuum
Tang, Huang; Buehler, Markus J.; Moran, Brian
2009-01-01
dependence of the continuum response as a function of nanoscopic structural features, providing evidence for the notion that the molecular basis for protein materials is important in defining their larger-scale mechanical properties. Ā© 2009 Biomedical
Discrimination between discrete and continuum scattering from the sub-seafloor.
Holland, Charles W; Steininger, Gavin; Dosso, Stan E
2015-08-01
There is growing evidence that seabed scattering is often dominated by heterogeneities within the sediment volume as opposed to seafloor roughness. From a theoretical viewpoint, sediment volume heterogeneities can be described either by a fluctuation continuum or by discrete particles. In at-sea experiments, heterogeneity characteristics generally are not known a priori. Thus, an uninformed model selection is generally made, i.e., the researcher must arbitrarily select either a discrete or continuum model. It is shown here that it is possible to (acoustically) discriminate between continuum and discrete heterogeneities in some instances. For example, when the spectral exponent Ī³3>4, the volume scattering cannot be described by discrete particles. Conversely, when Ī³3ā¤2, the heterogeneities likely arise from discrete particles. Furthermore, in the range 2discrete vs continuum heterogeneities via acoustic remote sensing may lead to improved observations and concomitant increased understanding of the marine benthic environment.
International Nuclear Information System (INIS)
Murata, Toru
2003-01-01
The level density parameters are determined to reproduce level structure and/or resonance level spacing of the nucleus. In the statistical compound nucleus model, cross sections to discrete levels decrease abruptly, and continuum level cross section increase strongly above the energy point where the continuum levels switched on. In the present study, for the nucleus which level scheme were well determined up to higher excitation energy more than 10 MeV, discrete level cross sections were calculated and summed up and compared with the cross section to the assumed continuum level corresponding to the discrete levels above several MeV excitation energy. Calculation of the (n, n') cross sections were made with CASTHY code of Moldauer model option using level density parameters determined with former method. It is shown that the assumed continuum cross section is fairly large compared with the summed up cross section. Origins of the discrepancy were discussed. (J.P.N.)
Mirrored continuum and molecular scale simulations of the ignition of gamma phase RDX
Stewart, D. Scott; Chaudhuri, Santanu; Joshi, Kaushik; Lee, Kibaek
2017-01-01
We describe the ignition of an explosive crystal of gamma-phase RDX due to a thermal hot spot with reactive molecular dynamics (RMD), with first-principles trained, reactive force field based molecular potentials that represents an extremely complex reaction network. The RMD simulation is analyzed by sorting molecular product fragments into high and low molecular weight groups, to represent identifiable components that can be interpreted by a continuum model. A continuum model based on a Gibbs formulation has a single temperature and stress state for the mixture. The continuum simulation that mirrors the atomistic simulation allows us to study the atomistic simulation in the familiar physical chemistry framework and provides an essential, continuum/atomistic link.
Beyond R & D: Market Impact, Continuum Magazine, Summer 2016 / Issue 9
Energy Technology Data Exchange (ETDEWEB)
2016-07-01
This issue of NREL's Continuum Magazine covers the depth and breadth of the laboratory's work to bridge scientific discovery and market adoption by helping technologies move from research through development, demonstration, and deployment.
Photofragmentation of water and hydrogen sulphide in the first continuum: A critical survey
International Nuclear Information System (INIS)
Mohamed, K.A.
1987-06-01
Photofragmentation of H 2 O and H 2 S in the first absorption continuum has been investigated experimentally and theoretically by several authors. The fragmentation dynamics of both molecules are reviewed in this article. While the excited 1 B 1 state in H 2 O is responsible for the first continuum, ambiguity exists in the true nature of the upper state of the first continuum in H 2 S. From the evidence available so far, it is proposed that both in water and hydrogen sulphide, a single state of B 1 symmetry, which is of Rydberg type for short internuclear distances and of valence type for large internuclear distances, is the possible upper state which dissociates to produce the absorption continuum. (author). Refs
3D continuum phonon model for group-IV 2D materials
Willatzen, Morten; Lew Yan Voon, Lok C; Gandi, Appala; Schwingenschlö gl, Udo
2017-01-01
A general three-dimensional continuum model of phonons in two-dimensional materials is developed. Our first-principles derivation includes full consideration of the lattice anisotropy and flexural modes perpendicular to the layers and can thus
Temperature Dependences of Mechanisms Responsible for the Water-Vapor Continuum Absorption
Ma, Qiancheng
2014-01-01
The water-vapor continuum absorption plays an important role in the radiative balance in the Earth's atmosphere. It has been experimentally shown that for ambient atmospheric conditions, the continuum absorption scales quadratically with the H2O number density and has a strong, negative temperature dependence (T dependence). Over the years, there have been three different theoretical mechanisms postulated: far-wings of allowed transition lines, water dimers, and collision-induced absorption. The first mechanism proposed was the accumulation of absorptions from the far-wings of the strong allowed transition lines. Later, absorption by water dimers was proposed, and this mechanism provides a qualitative explanation for the continuum characters mentioned above. Despite the improvements in experimental data, at present there is no consensus on which mechanism is primarily responsible for the continuum absorption.
Surface green function matching for a three-dimensional non-local continuum
International Nuclear Information System (INIS)
Idiodi, J.O.A.
1985-07-01
With a view toward helping to bridge the gap, from the continuum side, between discrete and continuum models of crystalline, elastic solids, explicit results are presented for non-local stress tensors that describe exactly some lattice dynamical models that have been widely used in the literature for cubic lattices. The Surface Green Function Matching (SGFM) method, which has been used successfully for a variety of surface problems, is then extended, within a continuum approach, to a non-local continuum that models a three-dimensional discrete lattice. The practical use of the method is demonstrated by performing a fairly complete analytical study of the vibrational surface modes of the SCC semi-infinite medium. Some results are presented for the [100] direction of the (001) surface of the SCC lattice. (author)
Cui, Quan; Chen, Zhongyun; Liu, Qian; Zhang, Zhihong; Luo, Qingming; Fu, Ling
2017-09-01
In this study, we demonstrate endogenous fluorescence imaging using visible continuum pulses based on 100-fs Ti:sapphire oscillator and a nonlinear photonic crystal fiber. Broadband (500-700 nm) and high-power (150 mW) continuum pulses are generated through enhanced dispersive wave generation by pumping femtosecond pulses at the anomalous dispersion region near zero-dispersion wavelength of high-nonlinear photonic crystal fibers. We also minimize the continuum pulse width by determining the proper fiber length. The visible-wavelength two-photon microscopy produces NADH and tryptophan images of mice tissues simultaneously. Our 500-700 nm continuum pulses support extending nonlinear microscopy to visible wavelength range that is inaccessible to 100-fs Ti:sapphire oscillators and other applications requiring visible laser pulses.
Zakhama, R.
2009-01-01
Topology optimisation of continuum structures has become mature enough to be often applied in industry and continues to attract the attention of researchers and software companies in various engineering fields. Traditionally, most available algorithms for solving topology optimisation problems are
Schomerus, G; Angermeyer, M C; Baumeister, S E; Stolzenburg, S; Link, B G; Phelan, J C
2016-02-01
A core component of stigma is being set apart as a distinct, dichotomously different kind of person. We examine whether information on a continuum from mental health to mental illness reduces stigma. Online survey experiment in a quota sample matching the German population for age, gender and region (n=1679). Participants randomly received information on either (1) a continuum, (2) a strict dichotomy of mental health and mental illness, or (3) no information. We elicited continuity beliefs and stigma toward a person with schizophrenia or depression. The continuum intervention decreased perceived difference by 0.19 standard deviations (SD, Pmental illness can be improved by providing information on a mental health-mental illness continuum. Copyright Ā© 2015 Elsevier Masson SAS. All rights reserved.
A continuum model for pressure-flow relationship in human pulmonary circulation.
Huang, Wei; Zhou, Qinlian; Gao, Jian; Yen, R T
2011-06-01
A continuum model was introduced to analyze the pressure-flow relationship for steady flow in human pulmonary circulation. The continuum approach was based on the principles of continuum mechanics in conjunction with detailed measurement of vascular geometry, vascular elasticity and blood rheology. The pulmonary arteries and veins were considered as elastic tubes and the "fifth-power law" was used to describe the pressure-flow relationship. For pulmonary capillaries, the "sheet-flow" theory was employed and the pressure-flow relationship was represented by the "fourth-power law". In this paper, the pressure-flow relationship for the whole pulmonary circulation and the longitudinal pressure distribution along the streamlines were studied. Our computed data showed general agreement with the experimental data for the normal subjects and the patients with mitral stenosis and chronic bronchitis in the literature. In conclusion, our continuum model can be used to predict the changes of steady flow in human pulmonary circulation.
Continuum contributions to dipole oscillator-strength sum rules for hydrogen in finite basis sets
DEFF Research Database (Denmark)
Oddershede, Jens; Ogilvie, John F.; Sauer, Stephan P. A.
2017-01-01
Calculations of the continuum contributions to dipole oscillator sum rules for hydrogen are performed using both exact and basis-set representations of the stick spectra of the continuum wave function. We show that the same results are obtained for the sum rules in both cases, but that the conver......Calculations of the continuum contributions to dipole oscillator sum rules for hydrogen are performed using both exact and basis-set representations of the stick spectra of the continuum wave function. We show that the same results are obtained for the sum rules in both cases......, but that the convergence towards the final results with increasing excitation energies included in the sum over states is slower in the basis-set cases when we use the best basis. We argue also that this conclusion most likely holds also for larger atoms or molecules....
There is a continuum ambiguity for elastic ĻN amplitudes
International Nuclear Information System (INIS)
Atkinson, D.; Roo, M. de; Polman, T.J.T.M.
1984-01-01
The implicit-function method of constructing phase-factor continuum ambiguities in phase-shift analysis is briefly reviewed, and new numerical examples are given of ambiguities in ĻN phase shifts at 1997 MeV. Since the ambiguous amplitudes differ by more than 5%, while the corresponding cross sections and polarizations are equal, to better than a computational accuracy of 0.007%, numerical credence is given to the theoretical claim that the continuum ambiguity exists. (orig.)
Breakdown of the 1/N expansion in the continuum limit of strong coupling lattice QCD
International Nuclear Information System (INIS)
Bralic, N.; Pontificia Universidade Catolica de Chile, Santiago. Facultad de Fisica); Loewe, M.
1983-08-01
The restoration of lorentz covariance in the continuum limit of strong coupling lattice QCD is shown to require the breakdown of the 1/N expansion. With the leading 1/N appoximation becoming irrelevant in that limit. To leading order in 1/N lorentz convariance can be restored only as an approximate long distance symmetry a non conventional continuum limit with a non hermitian hamiltonian. (Author) [pt
Nano-Continuum Modeling of a Nuclear Glass Specimen Altered for 25 Years
Energy Technology Data Exchange (ETDEWEB)
Steefel, Carl
2014-01-06
The purpose of this contribution is to report on preliminary nano-continuum scale modeling of nuclear waste glass corrosion. The focus of the modeling is an experiment involving a French glass SON68 specimen leached for 25 years in a granitic environment. In this report, we focus on capturing the nano-scale concentration profiles. We use a high resolution continuum model with a constant grid spacing of 1 nanometer to investigate the glass corrosion mechanisms.
A Concentric Tube Continuum Robot with Piezoelectric Actuation for MRI-Guided Closed-Loop Targeting
Su, Hao; Li, Gang; Rucker, D. Caleb; Webster, Robert J.; Fischer, Gregory S.
2016-01-01
This paper presents the design, modeling and experimental evaluation of a magnetic resonance imaging (MRI)-compatible concentric tube continuum robotic system. This system enables MRI-guided deployment of a precurved and steerable concentric tube continuum mechanism, and is suitable for clinical applications where a curved trajectory is needed. This compact 6 degree-of-freedom (DOF) robotic system is piezoelectrically-actuated, and allows simultaneous robot motion and imaging with no visually...
Systematic classical continuum limits of integrable spin chains and emerging novel dualities
International Nuclear Information System (INIS)
Avan, Jean; Doikou, Anastasia; Sfetsos, Konstadinos
2010-01-01
We examine certain classical continuum long wave-length limits of prototype integrable quantum spin chains. We define the corresponding construction of classical continuum Lax operators. Our discussion starts with the XXX chain, the anisotropic Heisenberg model and their generalizations and extends to the generic isotropic and anisotropic gl n magnets. Certain classical and quantum integrable models emerging from special 'dualities' of quantum spin chains, parametrized by c-number matrices, are also presented.
A continuum of research projects to improve extraction of oil and proteins in oilseed plants
Directory of Open Access Journals (Sweden)
Miquel Martine
2011-05-01
Full Text Available A key challenge in the actual context of fossil sources rarefaction, global warming, and of increase of the world global population, is to promote the use of molecules derived from renewable sources such as plants. Among these molecules, lipids and proteins are targets of interest. Plant lipids from oilseeds are attractive substitutes to the use of fossil oil. Till the beginning of the 20th century, numerous products used in the daily life were derived from natural renewable products. For instance, plant oil was commonly used as fuel for vehicles and was entering in the composition of paintings, lubricants etc. Unfortunately, natural oils have been progressively replaced by cheaper fossil oil in the fabrication of these products. Nowadays, fossil oils are becoming increasingly expensive being a finite comodity. It is thus important to reduce our dependence from fossil oil and develop substitution industries. Oilseeds contain important amounts of proteins which are mainly used in feed. As several kilograms of plant protein are needed to obtain one kilogram of animal protein, the interest toward using plant protein in food is reinforced. The developments of the use of plant lipids, as well as proteins are a major stakes for the competitiveness of European agriculture and industry, as well as for sustainable development. Extraction of oil and proteins from rapeseed has a significant cost, in term of energy and solvent uses, and finally affects the ultimate quality of the products (protein digestibility. In order to quantitatively extract seed reserves under mild conditions, it will be necessary to limit the amount of energy needed, and avoid any use of solvents. Ideally, seeds should be processed in a bio refinery. In this paper, we will describe how oilseeds store their reserves, and roadblocks for improving actual oilseed extraction processes. A continuum of research projects aimed at answering targeted questions will be presented, with selected
Directory of Open Access Journals (Sweden)
Carissa Nadia Kuswanto
2013-12-01
Full Text Available The Kraepelinian dichotomy posits that patients with schizophrenia (SCZ and bipolar disorder (BD present as two separate psychotic entities such that they differ in terms of clinical severity including neurocognitive functioning. Our study aimed to specifically compare and contrast the level of neurocognitive functioning between SCZ and BD patients and identify predictors of their poor neurocognitive functioning. We hypothesized that patients with SCZ had a similar level of neurcognitive impairment compared with BD. Forty-nine healthy controls (HC, 72 SCZ and 42 BD patients who were matched for age, gender, and premorbid IQ were administered the Brief Assessment of Cognition battery (BAC. Severity of psychopathology and socio-occupational functioning were assessed for both patients groups. Both BD and SCZ groups demonstrated similar patterns of neurocognitive deficits across several domains (verbal memory, working memory, semantic fluency, processing speed compared with HC subjects. However, no significant difference was found in neurocognitive functioning between BD and SCZ patients, suggesting that both patient groups suffer the same degree of neurocognitive impairment. Patients with lower level of psychosocial functioning (F(1,112 = 2.661, p = 0.009 and older age (F(1,112 = -2.625, p = 0.010, not diagnosis or doses of psychotropic medications, predicted poorer overall neurocognitive functioning as measured by the lower BAC composite score. Our findings of comparable neurocognitive impairments between SCZ and BD affirm our hypothesis and support less the Kraepelinian concept of dichotomy but more of a continuum of psychotic spectrum conditions. This should urge clinicians to investigate further the underlying neural basis of these neurocognitive deficits, and be attentive to the associated socio-demographic and clinical profile in order to recognize and optimize early the management of the widespread neurocognitive deficits in patients with
Reactivity continuum modeling of leaf, root, and wood decomposition across biomes
Koehler, Birgit; Tranvik, Lars J.
2015-07-01
Large carbon dioxide amounts are released to the atmosphere during organic matter decomposition. Yet the large-scale and long-term regulation of this critical process in global carbon cycling by litter chemistry and climate remains poorly understood. We used reactivity continuum (RC) modeling to analyze the decadal data set of the "Long-term Intersite Decomposition Experiment," in which fine litter and wood decomposition was studied in eight biome types (224 time series). In 32 and 46% of all sites the litter content of the acid-unhydrolyzable residue (AUR, formerly referred to as lignin) and the AUR/nitrogen ratio, respectively, retarded initial decomposition rates. This initial rate-retarding effect generally disappeared within the first year of decomposition, and rate-stimulating effects of nutrients and a rate-retarding effect of the carbon/nitrogen ratio became more prevalent. For needles and leaves/grasses, the influence of climate on decomposition decreased over time. For fine roots, the climatic influence was initially smaller but increased toward later-stage decomposition. The climate decomposition index was the strongest climatic predictor of decomposition. The similar variability in initial decomposition rates across litter categories as across biome types suggested that future changes in decomposition may be dominated by warming-induced changes in plant community composition. In general, the RC model parameters successfully predicted independent decomposition data for the different litter-biome combinations (196 time series). We argue that parameterization of large-scale decomposition models with RC model parameters, as opposed to the currently common discrete multiexponential models, could significantly improve their mechanistic foundation and predictive accuracy across climate zones and litter categories.
Lattice Boltzmann method for multi-component, non-continuum mass diffusion
International Nuclear Information System (INIS)
Joshi, Abhijit S; Peracchio, Aldo A; Grew, Kyle N; Chiu, Wilson K S
2007-01-01
Recently, there has been a great deal of interest in extending the lattice Boltzmann method (LBM) to model transport phenomena in the non-continuum regime. Most of these studies have focused on single-component flows through simple geometries. This work examines an ad hoc extension of a recently developed LBM model for multi-component mass diffusion (Joshi et al 2007 J. Phys. D: Appl. Phys. 40 2961) to model mass diffusion in the non-continuum regime. In order to validate the method, LBM results for ternary diffusion in a two-dimensional channel are compared with predictions of the dusty gas model (DGM) over a range of Knudsen numbers. A calibration factor based on the DGM is used in the LBM to correlate Knudsen diffusivity to pore size. Results indicate that the LBM can be a useful tool for predicting non-continuum mass diffusion (Kn > 0.001), but additional research is needed to extend the range of applicability of the algorithm for a larger parameter space. Guidelines are given on using the methodology described in this work to model non-continuum mass transport in more complex geometries where the DGM is not easily applicable. In addition, the non-continuum LBM methodology can be extended to three-dimensions. An envisioned application of this technique is to model non-continuum mass transport in porous solid oxide fuel cell electrodes
Hannan, Michael W.; Walker, Ian D.
2003-01-01
Traditionally, robot manipulators have been a simple arrangement of a small number of serially connected links and actuated joints. Though these manipulators prove to be very effective for many tasks, they are not without their limitations, due mainly to their lack of maneuverability or total degrees of freedom. Continuum style (i.e., continuous "back-bone") robots, on the other hand, exhibit a wide range of maneuverability, and can have a large number of degrees of freedom. The motion of continuum style robots is generated through the bending of the robot over a given section; unlike traditional robots where the motion occurs in discrete locations, i.e., joints. The motion of continuum manipulators is often compared to that of biological manipulators such as trunks and tentacles. These continuum style robots can achieve motions that could only be obtainable by a conventionally designed robot with many more degrees of freedom. In this paper we present a detailed formulation and explanation of a novel kinematic model for continuum style robots. The design, construction, and implementation of our continuum style robot called the elephant trunk manipulator is presented. Experimental results are then provided to verify the legitimacy of our model when applied to our physical manipulator. We also provide a set of obstacle avoidance experiments that help to exhibit the practical implementation of both our manipulator and our kinematic model. c2003 Wiley Periodicals, Inc.
Qi, Fei; Ju, Feng; Bai, Dong Ming; Chen, Bai
2018-02-01
For the outstanding compliance and dexterity of continuum robot, it is increasingly used in minimally invasive surgery. The wide workspace, high dexterity and strong payload capacity are essential to the continuum robot. In this article, we investigate the workspace of a cable-driven continuum robot that we proposed. The influence of section number on the workspace is discussed when robot is operated in narrow environment. Meanwhile, the structural parameters of this continuum robot are optimized to achieve better kinematic performance. Moreover, an indicator based on the dexterous solid angle for evaluating the dexterity of robot is introduced and the distal end dexterity is compared for the three-section continuum robot with different range of variables. Results imply that the wider range of variables achieve the better dexterity. Finally, the static model of robot based on the principle of virtual work is derived to analyze the relationship between the bending shape deformation and the driven force. The simulations and experiments for plane and spatial motions are conducted to validate the feasibility of model, respectively. Results of this article can contribute to the real-time control and movement and can be a design reference for cable-driven continuum robot.
Use of a finite range nucleon-nucleon interaction in the continuum shell model
International Nuclear Information System (INIS)
Faes, Jean-Baptiste
2007-01-01
The unification of nuclear structure and nuclear reactions was always a great challenge of nuclear physics. The extreme complexity of finite quantum systems lead in the past to a separate development of the nuclear structure and the nuclear reactions. A unified description of structure and reactions is possible within the continuum shell model. All previous applications of this model used the zero-range residual interaction and the finite depth local potential to generate the single-particle basis. In the thesis, we have presented an extension of the continuum shell model for finite-range nucleon-nucleon interaction and an arbitrary number of nucleons in the scattering continuum. The great advantage of the present formulation is the same two-body interaction used both to generate the single-particle basis and to describe couplings to the continuum states. This formulation opens a possibility for an ab initio continuum shell model studies with the same nucleon-nucleon interaction generating the nuclear mean field, the configuration mixing and the coupling to the scattering continuum. First realistic applications of the above model has been shown for spectra of "1"7F and "1"7O, and elastic phase-shifts in the reaction "1"6O(p, p)"1"6O. (author)
Influence of gyroradius and dissipation on the Alfven-wave continuum
International Nuclear Information System (INIS)
Connor, J.W.; Tang, W.M.; Taylor, J.B.
1982-01-01
It is well known that in ideal magnetohydrodynamics there is a continuous spectrum of real frequencies associated with a singularity of the shear Alfven waves on the surface k/sub parallel to/v/sub A/ = omega. It is also known that the introduction of first-order gyroradius effects eliminates the continuum. In the present work we examine the influence of the full gyroradius response and of dissipation on the continuum. In the absence of dissipation we first confirm that if only first-order gyroradius effects are incorporated, the continuum disappears. However, when the full gyroradius response is included, this discrete spectrum vanishes, and a new continuum (associated with singularities at k/sub parallel to/v/sub A/ = 0) appears. The introduction of collisional dissipation removes the original MHD continuum leaving discrete modes whose frequency tends to zero with the collision rate as Ī½/sup 1/3/. collisions also remove the new continuum of the full gyroradius model leaving discrete modes whose frequency tends to zero as (log Ī½) -1 . Collisionless Landau damping has a similar effect
Amplification of non-Markovian decay due to bound state absorption into continuum
International Nuclear Information System (INIS)
Garmon, S.; Simine, L.; Segal, D.; Petrosky, T.
2013-01-01
It is known that quantum systems yield non-exponential (power law) decay on long time scales, associated with continuum threshold effects contributing to the survival probability for a prepared initial state. For an open quantum system consisting of a discrete state coupled to continuum, we study the case in which a discrete bound state of the full Hamiltonian approaches the energy continuum as the system parameters are varied. We find in this case that at least two regions exist yielding qualitatively different power law decay behaviors; we term these the long time 'near zone' and long time 'far zone'. In the near zone the survival probability falls off according to a t -1 power law, and in the far zone i t falls off as t -3 . We show that the timescale T Q separating these two regions is inversely related to the gap between the discrete bound state energy and the continuum threshold. In the case that the bound state is absorbed into the continuum and vanishes, then the time scale T Q diverges and the survival probability follows the t -1 power law even on asymptotic scales. Conversely, one could study the case of an anti-bound state approaching the threshold before being ejected from the continuum to form a bound state. Again the t -1 power law dominates precisely at the point of ejection. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
A Cyclical Approach to Continuum Modeling: A Conceptual Model of Diabetic Foot Care
Directory of Open Access Journals (Sweden)
Martha L. Carvour
2017-12-01
Full Text Available āCascadeā or ācontinuumā models have been developed for a number of diseases and conditions. These models define the desired, successive steps in care for that disease or condition and depict the proportion of the population that has completed each step. These models may be used to compare care across subgroups or populations and to identify and evaluate interventions intended to improve outcomes on the population level. Previous cascade or continuum models have been limited by several factors. These models are best suited to processes with stepwise outcomesāsuch as screening, diagnosis, and treatmentāwith a single defined outcome (e.g., treatment or cure for each member of the population. However, continuum modeling is not well developed for complex processes with non-sequential or recurring steps or those without singular outcomes. As shown here using the example of diabetic foot care, the concept of continuum modeling may be re-envisioned with a cyclical approach. Cyclical continuum modeling may permit incorporation of non-sequential and recurring steps into a single continuum, while recognizing the presence of multiple desirable outcomes within the population. Cyclical models may simultaneously represent the distribution of clinical severity and clinical resource use across a population, thereby extending the benefits of traditional continuum models to complex processes for which population-based monitoring is desired. The models may also support communication with other stakeholders in the process of care, including health care providers and patients.
The Effect of Volcanic Ash Composition on Ice Nucleation Affinity
Genareau, K. D.; Cloer, S.; Primm, K.; Woods, T.; Tolbert, M. A.
2017-12-01
Understanding the role that volcanic ash plays in ice nucleation is important for knowledge of lightning generation in both volcanic plumes and in clouds developing downwind from active volcanoes. Volcanic ash has long been suggested to influence heterogeneous ice nucleation following explosive eruptions, but determining precisely how composition and mineralogy affects ice nucleation affinity (INA) is poorly constrained. For the study presented here, volcanic ash samples with different compositions and mineral/glass contents were tested in both the deposition and immersion modes, following the methods presented in Schill et al. (2015). Bulk composition was determined with X-ray fluorescence (XRF), grain size distribution was determined with laser diffraction particle size analysis (LDPSA), and mineralogy was determined with X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results of the deposition-mode experiments reveal that there is no relationship between ice saturation ratios (Sice) and either mineralogy or bulk ash composition, as all samples have similar Sice ratios. In the immersion-mode experiments, frozen fractions were determined from -20 Ā°C to -50 Ā°C using three different amounts of ash (0.5, 1.0, and 2.0 wt% of slurry). Results from the immersion freezing reveal that the rhyolitic samples (73 wt% SiO2) nucleate ice at higher temperatures compared to the basaltic samples (49 wt% SiO2). There is no observed correlation between frozen fractions and mineral content of ash samples, but the two most efficient ice nuclei are rhyolites that contain the greatest proportion of amorphous glass (> 90 %), and are enriched in K2O relative to transition metals (MnO and TiO2), the latter of which show a negative correlation with frozen fraction. Higher ash abundance in water droplets increases the frozen fraction at all temperatures, indicating that ash amount plays the biggest role in ice nucleation. If volcanic ash can reach sufficient abundance (ā
Carbon Fluxes and Transport Along the Terrestrial Aquatic Continuum
Butman, D. E.; Kolka, R.; Fennel, K.; Stackpoole, S. M.; Trettin, C.; Windham-Myers, L.
2017-12-01
terrestrial-aquatic continuum.
Near-infrared water vapour self-continuum at close to room temperature
International Nuclear Information System (INIS)
Ptashnik, I.V.; Petrova, T.M.; Ponomarev, Yu.N.; Shine, K.P.; Solodov, A.A.; Solodov, A.M.
2013-01-01
The gaseous absorption of solar radiation within near-infrared atmospheric windows in the Earth's atmosphere is dominated by the water vapour continuum. Recent measurements by Baranov et al. (2011) [17] in 2500 cm ā1 (4 Ī¼m) window and by Ptashnik et al. (2011) [18] in a few near-infrared windows revealed that the self-continuum absorption is typically an order of magnitude stronger than given by the MT C KD continuum model prior to version 2.5. Most of these measurements, however, were made at elevated temperatures, which makes their application to atmospheric conditions difficult. Here we report new laboratory measurements of the self-continuum absorption at 289 and 318 K in the near-infrared spectral region 1300ā8000 cm ā1 , using a multipass 30 m base cell with total optical path 612 m. Our results confirm the main conclusions of the previous measurements both within bands and in windows. Of particular note is that we present what we believe to be the first near-room temperature measurement using Fourier Transform Spectrometry of the self-continuum in the 6200 cm ā1 (1.6 Ī¼m) window, which provides tentative evidence that, at such temperatures, the water vapour continuum absorption may be as strong as it is in 2.1 Ī¼m and 4 Ī¼m windows and up to 2 orders of magnitude stronger than the MT C KD-2.5 continuum. We note that alternative methods of measuring the continuum in this window have yielded widely differing assessment of its strength, which emphasises the need for further measurements. -- Highlights: āŗ New lab measurements of the near-infrared water vapour self-continuum absorption. āŗ First room-temperature data on the self-continuum in the 1.6 Ī¼m window. āŗ In the 1.6 Ī¼m window the new data exceed MT C KD-2.5 model by 2 orders of magnitude
Tsukanov, N. V.; Skolotnev, S. G.
2018-02-01
This work presents new data on the composition of volcanics, developed within the Alazeya Plateau of the Kolyma-Indigirka fold area (Northeast Russia), which indicate essential differences in their composition and, accordingly, different geodynamic settings of the formation of rocks. The studied igneous rocks are subdivided into two groups. Volcanics of the first group of the Late Cretaceous age, which are represented by differentiated volcanic rock series (from andesitobasalts to dacites and rhyolites), were formed under island arc conditions in the continent-ocean transition zone. Volcanics of the second group are ascribed to the tholeiitic series and were formed under the other geodynamic setting, which is associated with the regime of extension and riftogenesis, manifested in the studied area probably at the later stage.
On the Nature of Off-limb Flare Continuum Sources Detected by SDO /HMI
Energy Technology Data Exchange (ETDEWEB)
Heinzel, P.; KaÅ”parovĆ”, J. [Astronomical Institute, Czech Academy of Sciences, 25165 OndrĢejov (Czech Republic); Kleint, L.; Krucker, S., E-mail: pheinzel@asu.cas.cz [University of Applied Sciences and Arts Northwestern Switzerland, Bahnhofstrasse 6, 5210 Windisch (Switzerland)
2017-09-20
The Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory has provided unique observations of off-limb flare emission. White-light continuum enhancements were detected in the ācontinuumā channel of the Fe 6173 ā« line during the impulsive phase of the observed flares. In this paper we aim to determine which radiation mechanism is responsible for such enhancement being seen above the limb, at chromospheric heights around or below 1000 km. Using a simple analytical approach, we compare two candidate mechanisms, the hydrogen recombination continuum (Paschen) and the Thomson continuum due to scattering of disk radiation on flare electrons. Both mechanisms depend on the electron density, which is typically enhanced during the impulsive phase of a flare as the result of collisional ionization (both thermal and also non-thermal due to electron beams). We conclude that for electron densities higher than 10{sup 12} cm{sup ā3}, the Paschen recombination continuum significantly dominates the Thomson scattering continuum and there is some contribution from the hydrogen freeāfree emission. This is further supported by detailed radiation-hydrodynamical (RHD) simulations of the flare chromosphere heated by the electron beams. We use the RHD code FLARIX to compute the temporal evolution of the flare-heating in a semi-circular loop. The synthesized continuum structure above the limb resembles the off-limb flare structures detected by HMI, namely their height above the limb, as well as the radiation intensity. These results are consistent with recent findings related to hydrogen Balmer continuum enhancements, which were clearly detected in disk flares by the IRIS near-ultraviolet spectrometer.
Monitoring the HIV continuum of care in key populations across Europe and Central Asia.
Brown, A E; Attawell, K; Hales, D; Rice, B D; Pharris, A; Supervie, V; Van Beckhoven, D; Delpech, V C; An der Heiden, M; Marcus, U; Maly, M; Noori, T
2018-05-08
The aim of the study was to measure and compare national continuum of HIV care estimates in Europe and Central Asia in three key subpopulations: men who have sex with men (MSM), people who inject drugs (PWID) and migrants. Responses to a 2016 European Centre for Disease Prevention and Control (ECDC) survey of 55 European and Central Asian countries were used to describe continuums of HIV care for the subpopulations. Data were analysed using three frameworks: Joint United Nations Programme on HIV/AIDS (UNAIDS) 90-90-90 targets; breakpoint analysis identifying reductions between adjacent continuum stages; quadrant analysis categorizing countries using 90% cut-offs for continuum stages. Overall, 29 of 48 countries reported national data for all HIV continuum stages (numbers living with HIV, diagnosed, receiving treatment and virally suppressed). Six countries reported all stages for MSM, seven for PWID and two for migrants. Thirty-one countries did not report data for MSM (34 for PWID and 41 for migrants). In countries that provided key-population data, overall, 63%, 40% and 41% of MSM, PWID and migrants living with HIV were virally suppressed, respectively (compared with 68%, 65% and 68% nationally, for countries reporting key-population data). Variation was observed between countries, with higher outcomes in subpopulations in Western Europe compared with Eastern Europe and Central Asia. Few reporting countries can produce the continuum of HIV care for the three key populations. Where data are available, differences exist in outcomes between the general and key populations. While MSM broadly mirror national outcomes (in the West), PWID and migrants experience poorer treatment and viral suppression. Countries must develop continuum measures for key populations to identify and address inequalities. Ā© 2018 British HIV Association.