Large Igneous Provinces, Their Giant Mafic Dyke Swarms, and Links to Metallogeny

NASA Astrophysics Data System (ADS)

Jowitt, S.; Ernst, R. E.

2017-12-01

The relationships between large igneous provinces (LIPs), their giant dyke swarms and differing metallogenic systems can be condensed into five distinct although partially overlapping classifications: (1) LIP magmas that directly generate mineral deposits such as orthomagmatic Ni-Cu-PGE sulfides. Many carbonatites (Nb, Ta REE deposits) and kimberlites (diamonds) are also often LIP related. On the other hand, LIP-related thermal pulses (from a mantle plume) can sometimes destroy diamond potential in the overlying lithosphere. A key locus for Ni-Cu-PGE mineralization is within a few hundred km of the plume center region and plume centers are best located using giant radiating dyke swarms. Dyke subswarms with chalcophile element depletions can also be tracked "upstream" toward the plume center to identify exploration targets. (2) LIP magmas that provide energy, fluids, and/or metals for ore types such as hydrothermal volcanogenic massive sulfide (VMS) and iron oxide-copper-gold (IOCG) deposits. Heat loss from the margins of dykes and sills can also generate local enrichments in key metals (e.g. Co) within the surrounding sedimentary rocks. (3) LIP rocks (particularly sills and dykes) can act barriers to fluid flow and/or as reaction zones that control mineralizing events, act as structural traps within hydrocarbon systems, and form impermeable barriers that control water flow and hence aquifer formation (4) surficial effects, such as the formation of Ni-Co laterites and Al bauxites from tropical weathering of LIP mafic-ultramafic rocks (including volcanics fed by radiating dykes as well as the dykes themselves). This category also includes LIP-related anoxia events that generate hydrocarbon source rocks; and (5) indirect links between LIPs and ore deposits, where continental breakup-related LIP events define a `barcode' record (usually dominated by dyke swarms) that can be used to correlate and reconstruct Precambrian supercontinents. This fifth classification type

Mangrove forest against dyke-break-induced tsunami on rapidly subsiding coasts

NASA Astrophysics Data System (ADS)

Takagi, Hiroshi; Mikami, Takahito; Fujii, Daisuke; Esteban, Miguel; Kurobe, Shota

2016-07-01

Thin coastal dykes typically found in developing countries may suddenly collapse due to rapid land subsidence, material ageing, sea-level rise, high wave attack, earthquakes, landslides, or a collision with vessels. Such a failure could trigger dam-break tsunami-type flooding, or "dyke-break-induced tsunami", a possibility which has so far been overlooked in the field of coastal disaster science and management. To analyse the potential consequences of one such flooding event caused by a dyke failure, a hydrodynamic model was constructed based on the authors' field surveys of a vulnerable coastal location in Jakarta, Indonesia. In a 2 m land subsidence scenario - which is expected to take place in the study area after only about 10-20 years - the model results show that the floodwaters rapidly rise to a height of nearly 3 m, resembling the flooding pattern of earthquake-induced tsunamis. The depth-velocity product criterion suggests that many of the narrow pedestrian paths behind the dyke could experience strong flows, which are far greater than the safe limits that would allow pedestrian evacuation. A couple of alternative scenarios were also considered to investigate how such flood impacts could be mitigated by creating a mangrove belt in front of the dyke as an additional safety measure. The dyke-break-induced tsunamis, which in many areas are far more likely than regular earthquake tsunamis, cannot be overlooked and thus should be considered in disaster management and urban planning along the coasts of many developing countries.

Has dyke development in the Vietnamese Mekong Delta shifted flood hazard downstream?

NASA Astrophysics Data System (ADS)

Van Khanh Triet, Nguyen; Viet Dung, Nguyen; Fujii, Hideto; Kummu, Matti; Merz, Bruno; Apel, Heiko

2017-08-01

In the Vietnamese part of the Mekong Delta (VMD) the areas with three rice crops per year have been expanded rapidly during the last 15 years. Paddy-rice cultivation during the flood season has been made possible by implementing high-dyke flood defenses and flood control structures. However, there are widespread claims that the high-dyke system has increased water levels in downstream areas. Our study aims at resolving this issue by attributing observed changes in flood characteristics to high-dyke construction and other possible causes. Maximum water levels and duration above the flood alarm level are analysed for gradual trends and step changes at different discharge gauges. Strong and robust increasing trends of peak water levels and duration downstream of the high-dyke areas are found with a step change in 2000/2001, i.e. immediately after the disastrous flood which initiated the high-dyke development. These changes are in contrast to the negative trends detected at stations upstream of the high-dyke areas. This spatially different behaviour of changes in flood characteristics seems to support the public claims. To separate the impact of the high-dyke development from the impact of the other drivers - i.e. changes in the flood hydrograph entering the Mekong Delta, and changes in the tidal dynamics - hydraulic model simulations of the two recent large flood events in 2000 and 2011 are performed. The hydraulic model is run for a set of scenarios whereas the different drivers are interchanged. The simulations reveal that for the central VMD an increase of 9-13 cm in flood peak and 15 days in duration can be attributed to high-dyke development. However, for this area the tidal dynamics have an even larger effect in the range of 19-32 cm. However, the relative contributions of the three drivers of change vary in space across the delta. In summary, our study confirms the claims that the high-dyke development has raised the flood hazard downstream. However, it is not

High Resolution Analysis of Dyke Tips and Segments, Using Drones

NASA Astrophysics Data System (ADS)

Dering, G.; Micklethwaite, S.; Cruden, A. R.

2016-12-01

We analyse outstanding exposures of dykes from both coastal (Western Australia) and high altitude glacier-polished (Sierra Nevada, California) outcrops, representing intrusion at shallow upper-crustal and mid-crustal conditions respectively. We covered 10,000 m^2 of outcrop area sampling the ground at a scale of 3-5 mm per pixel. Using Structure-from-Motion photogrammetry from ground-based and UAV photographs lacking GPS camera positions (>500 images per study), we generated and calibrated a 3D geometry of dense point clouds by selectively using 25-30 ground control points measured by high precision GPS (40-90 mm error). Ground control points used in the photogrammetric model building process typically yielded a root mean square error (RMSE) of 5 cm. Half the ground control points were withheld from the model building process and when they were compared against the model they yielded RMSE values only 6-10% higher than the points used for georeferencing, suggesting good internal consistency of the dataset and accuracy relative to the reference frame, at least for the purposes of this study. The structural orientations of the dykes and associated fractures were then extracted digitally using the iterative Random Sample Consensus method (RANSAC) and least-squares plane fitting. Furthermore, fracture intensity relative to dykes was measured along a series of scanlines and the running average and variance calculated. All results were compared against field measurements. Results show fracture intensity increases toward the dykes in the shallow crustal examples (West Australia) but no such fractures exist around the mid-crustal (Californian) dykes. Despite this there is a remarkable uniformity of geometry, and by implication process, between the two dyke sets. In order to extract full value from the big visual data now available to us, the near-future requires dedicated research into software solutions for expert-driven, semi-automatic mapping of geology and structure.

Challenging dyke ascent models using novel laboratory experiments: Implications for reinterpreting evidence of magma ascent and volcanism

NASA Astrophysics Data System (ADS)

Kavanagh, Janine L.; Burns, Alec J.; Hilmi Hazim, Suraya; Wood, Elliot P.; Martin, Simon A.; Hignett, Sam; Dennis, David J. C.

2018-04-01

Volcanic eruptions are fed by plumbing systems that transport magma from its source to the surface, mostly fed by dykes. Here we present laboratory experiments that model dyke ascent to eruption using a tank filled with a crust analogue (gelatine, which is transparent and elastic) that is injected from below by a magma analogue (dyed water). This novel experimental setup allows, for the first time, the simultaneous measurement of fluid flow, sub-surface and surface deformation during dyke ascent. During injection, a penny-shaped fluid-filled crack is formed, intrudes, and traverses the gelatine slab vertically to then erupt at the surface. Polarised light shows the internal stress evolution as the dyke ascends, and an overhead laser scanner measures the surface elevation change in the lead-up to dyke eruption. Fluorescent passive-tracer particles that are illuminated by a laser sheet are monitored, and the intruding fluid's flow dynamics and gelatine's sub-surface strain evolution is measured using particle image velocimetry and digital image correlation, respectively. We identify 4 previously undescribed stages of dyke ascent. Stage 1, early dyke growth: the initial dyke grows from the source, and two fluid jets circulate as the penny-shaped crack is formed. Stage 2, pseudo-steady dyke growth: characterised by the development of a rapidly uprising, central, single pseudo-steady fluid jet, as the dyke grows equally in length and width, and the fluid down-wells at the dyke margin. Sub-surface host strain is localised at the head region and the tail of the dyke is largely static. Stage 3, pre-eruption unsteady dyke growth: an instability in the fluid flow appears as the central fluid jet meanders, the dyke tip accelerates towards the surface and the tail thins. Surface deformation is only detected in the immediate lead-up to eruption and is characterised by an overall topographic increase, with axis-symmetric topographic highs developed above the dyke tip. Stage 4 is

Hubbard physics in the symmetric half-filled periodic anderson-hubbard model

NASA Astrophysics Data System (ADS)

Hagymási, I.; Itai, K.; Sólyom, J.

2013-05-01

Two very different methods — exact diagonalization on finite chains and a variational method — are used to study the possibility of a metal-insulator transition in the symmetric half-filled periodic Anderson-Hubbard model. With this aim we calculate the density of doubly occupied d sites ( gn d ) as a function of various parameters. In the absence of on-site Coulomb interaction ( U f ) between f electrons, the two methods yield similar results. The double occupancy of d levels remains always finite just as in the one-dimensional Hubbard model. Exact diagonalization on finite chains gives the same result for finite U f , while the Gutzwiller method leads to a Brinkman-Rice transition at a critical value ( U {/d c }), which depends on U f and V.

L Ron Hubbard's science fiction quest against psychiatry.

PubMed

Hirshbein, Laura

2016-12-01

Layfayette Ronald Hubbard (1911-1986) was a colourful and prolific American writer of science fiction in the 1930s and 1940s. During the time between his two decades of productivity and his return to science fiction in 1980, Hubbard founded the Church of Scientology. In addition to its controversial status as a religion and its troubling pattern of intimidation and litigation directed towards its foes, Scientology is well known as an organised opponent to psychiatry. This paper looks at Hubbard's science fiction work to help understand the evolution of Scientology's antipsychiatry stance, as well as the alternative to psychiatry offered by Hubbard. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Dyke-path formation in relation to the eruptions of Eyjafjallajökull 2010 and Bardarbunga-Holuhraun 2014

NASA Astrophysics Data System (ADS)

Gudmundsson, Agust

2015-04-01

Dykes are extension fractures and form when the magmatic overpressure is high enough to rupture (break) the host rock. Their formation is entirely analogous to that of many joints and human-made hydraulic fractures, such as are used to increase permeability in reservoirs. When generating their paths, dykes use existing weaknesses (e.g., cooling joints) in the host rock. The maximum depth of large tension fractures below the surface of a rift zone, however, is mostly less than a few hundred metres. If the fractures extend to greater depths, they must change into closed normal faults which are generally not used as magma paths. There are thus no large tension fractures or wide-open faults at great depths ready to be filled with magma to form a dyke. While magma flow in dykes, as in other fluid-driven fractures, is at any point in various directions dyke segmentation may indicate the overall large-scale flow direction. Thus, dykes composed of large-spaced disconnected segments in lateral sections are primarily formed in vertical magma flow at segmentation depth whereas those composed of large-spaced disconnected segments in vertical sections are primarily formed in lateral magma flow. The far-field displacement and stress fields of segmented dykes are similar to those generated by single, continuous dykes of similar dimensions, particularly when the distances between the nearby tips of the segments become small in comparison with segment lengths. Most dykes become arrested and never supply magma to eruptions. Feeder-dykes normally reach the surface only along parts of their lengths (strike-dimensions). The volumetric flow or effusion rate of magma through a feeder-dyke or volcanic fissure depends on the aperture (opening) of the dyke or fissure in the 3rd power. All these theoretical and observational results are here applied to the dyke emplacements associated with the eruptions of Eyjafjallajökull 2010 and Bardarbunga-Holuhraun 2014. The results make it possible to

Performance and capacity of river dykes of protection against the floods", through elaboration of performance indicators and decision aid tool in view of the patrimonial assessment of river dykes

NASA Astrophysics Data System (ADS)

Vuillet, Marc; Peyras, Laurent; Serre, Damien; Diab, Youssef

2010-05-01

France and more generally the World have to face frequent episodes of devastating floods. The human and material damages are multiplied during the failure of a protection structure. In France the length of dykes is estimated to 7500 kilometers, protecting around 15 000 to 18 000 km² and an estimated population between 1.6 to 2 millions. Regrettably, these structures are most of the time old, unidentified, badly maintained, showing signs of weaknesses on numerous occasions. The management of these dikes raises then considerable problems to the decision-makers who are in charge of guaranteeing a maximal safety to the populations at a rational and acceptable management cost. The ambition of the project "Performance and capacity in the service of river dykes of protection against the floods" is to propose to Administrator scientific methods and technical tools for the management of river dykes. These tools will be capable of estimating the capacity in the service of dykes, and to define and organize into a hierarchy the actions of inspection, maintenance and repair. Scientific objectives: • To suggest a methodology of evaluation of the performance of river dykes • To identify and to understand the causes of variability (spatial and temporal) • To analyze the relation between the quality of the data and the quality of the profile of performance • To propose a methodology of auscultation and confortation of the information The research work consists in adapting functional analysis based on safety engineering method, in order to precise the role of each rivers dyke's component in regard to the mechanisms of degradation they suffer. It will allow us to identify failure indicators and decision criteria for evaluating the performance of dykes. The criteria will be the basis to develop a multicriteria decision aid tool allowing to determine the hierarchical organization and the selection of the sections of a park of dykes of protection against the floods, according

Volcaniclastic dykes tell on fracturing, explosive eruption and lateral collapse at Stromboli volcano (Italy)

NASA Astrophysics Data System (ADS)

Vezzoli, Luigina; Corazzato, Claudia

2016-05-01

In the upper part of the Stromboli volcano, in the Le Croci and Bastimento areas, two dyke-like bodies of volcanic breccia up to two-metre thick crosscut and intrude the products of Vancori and Neostromboli volcanoes. We describe the lithofacies association of these unusual volcaniclastic dykes, interpret the setting of dyke-forming fractures and the emplacement mechanism of internal deposits, and discuss their probable relationships with the explosive eruption and major lateral collapse events that occurred at the end of the Neostromboli period. The dyke volcaniclastic deposits contain juvenile magmatic fragments (pyroclasts) suggesting a primary volcanic origin. Their petrographic characteristics are coincident with the Neostromboli products. The architecture of the infilling deposits comprises symmetrically-nested volcaniclastic units, separated by sub-vertical boundaries, which are parallel to the dyke margins. The volcanic units are composed of distinctive lithofacies. The more external facies is composed of fine and coarse ash showing sub-vertical laminations, parallel to the contact wall. The central facies comprises stratified, lithic-rich breccia and lapilli-tuff, whose stratification is sub-horizontal and convolute, discordant to the dyke margins. Only at Le Croci dyke, the final unit shows a massive tuff-breccia facies. The volcaniclastic dykes experienced a polyphasic geological evolution comprising three stages. The first phase consisted in fracturing, explosive intrusion related to magma rising and upward injection of magmatic fluids and pyroclasts. The second phase recorded the dilation of fractures and their role as pyroclastic conduits in an explosive eruption possibly coeval with the lateral collapse of the Neostromboli lava cone. Finally, in the third phase, the immediately post-eruption mass-flow remobilization of pyroclastic deposits took place on the volcano slopes.

Petrogenesis of low-δ18O quartz porphyry dykes, Koegel Fontein complex, South Africa

NASA Astrophysics Data System (ADS)

Harris, Chris; Mulder, Kwenidyn; Sarkar, Saheli; Whitehead, Benjamin; Roopnarain, Sherissa

2018-04-01

This paper investigates the origin of low-δ18O quartz porphyry dykes associated with the 144-133 Ma Koegel Fontein Igneous Complex, which was intruded during the initial phase of breakup of Africa and South America. The 25-km diameter Rietpoort Granite is the largest and youngest phase of activity, and is roofed by a 10-km diameter pendant of gneiss. Quartz porphyry (QP) dykes, up to 15 m in width, strike NW-SE across the complex. The QP dykes that intruded outside the granite have similar quartz phenocryst δ18O values (average 8.0‰, ± 0.7, n = 33) to the granite (average 8.3 ± 1.0, n = 7). The QP dykes that intruded the roof pendant have quartz phenocrysts with more variable δ18O values (average 1.6‰, ± 2.1, n = 55). In some cases quartz phenocrysts have δ18O values as low as - 2.5‰. The variation in δ18O value within the quartz crystal population of individual dykes is small relative to the overall range, and core and rim material from individual quartz phenocrysts in three samples are identical within error. There is no evidence that quartz phenocryst δ18O values have been affected by fluid-rock interaction. Based on a Δquartz-magma value of 0.6‰, magma δ18O values must have been as low as - 3.1‰. Samples collected along the length of the two main QP dykes that traverse the roof pendant have quartz phenocryst δ18O values that range from + 1.1 to + 4.6‰, and - 2.3 to + 5.6‰, respectively. These δ18O values correlate negatively ( r = - 0.96) with initial 87Sr/86Sr, which can be explained by the event that lowered δ18O values of the source being older than the dykes. We suggest that the QP dykes were fed by magma produced by partial melting of gneiss, which had been variably altered at high temperature by 18O-depleted meteoric water during global glaciation at 550 Ma. The early melts had variable δ18O value but as melt pockets interconnected during melting, the δ18O values approached that of average gneiss. Variable quartz phenocryst �

Quantum simulation of the Hubbard model with dopant atoms in silicon

PubMed Central

Salfi, J.; Mol, J. A.; Rahman, R.; Klimeck, G.; Simmons, M. Y.; Hollenberg, L. C. L.; Rogge, S.

2016-01-01

In quantum simulation, many-body phenomena are probed in controllable quantum systems. Recently, simulation of Bose–Hubbard Hamiltonians using cold atoms revealed previously hidden local correlations. However, fermionic many-body Hubbard phenomena such as unconventional superconductivity and spin liquids are more difficult to simulate using cold atoms. To date the required single-site measurements and cooling remain problematic, while only ensemble measurements have been achieved. Here we simulate a two-site Hubbard Hamiltonian at low effective temperatures with single-site resolution using subsurface dopants in silicon. We measure quasi-particle tunnelling maps of spin-resolved states with atomic resolution, finding interference processes from which the entanglement entropy and Hubbard interactions are quantified. Entanglement, determined by spin and orbital degrees of freedom, increases with increasing valence bond length. We find separation-tunable Hubbard interaction strengths that are suitable for simulating strongly correlated phenomena in larger arrays of dopants, establishing dopants as a platform for quantum simulation of the Hubbard model. PMID:27094205

Enhanced pairing susceptibility in a photodoped two-orbital Hubbard model

NASA Astrophysics Data System (ADS)

Werner, Philipp; Strand, Hugo U. R.; Hoshino, Shintaro; Murakami, Yuta; Eckstein, Martin

2018-04-01

Local spin fluctuations provide the glue for orbital-singlet spin-triplet pairing in the doped Mott insulating regime of multiorbital Hubbard models. At large Hubbard repulsion U , the pairing susceptibility is nevertheless tiny because the pairing interaction cannot overcome the suppression of charge fluctuations. Using nonequilibrium dynamical mean field simulations of the two-orbital Hubbard model, we show that out of equilibrium the pairing susceptibility in this large-U regime can be strongly enhanced by creating a photoinduced population of the relevant charge states. This enhancement is supported by the long lifetime of photodoped charge carriers and a built-in cooling mechanism in multiorbital Hubbard systems.

Modelling of surface stresses and fracturing during dyke emplacement: Application to the 2009 episode at Harrat Lunayyir, Saudi Arabia

NASA Astrophysics Data System (ADS)

Al Shehri, Azizah; Gudmundsson, Agust

2018-05-01

Correct interpretation of surface stresses and deformation or displacement during volcanotectonic episodes is of fundamental importance for hazard assessment and dyke-path forecasting. Here we present new general numerical models on the local stresses induced by arrested dykes. In the models, the crustal segments hosting the dyke vary greatly in mechanical properties, from uniform or non-layered (elastic half-spaces) to highly anisotropic (layers with strong contrast in Young's modulus). The shallow parts of active volcanoes and volcanic zones are normally highly anisotropic and some with open contacts. The numerical results show that, for a given surface deformation, non-layered (half-space) models underestimate the dyke overpressure/thickness needed and overestimate the likely depth to the tip of the dyke. Also, as the mechanical contrast between the layers increases, so does the stress dissipation and associated reduction in surface stresses (and associated fracturing). In the absence of open contacts, the distance between the two dyke-induced tensile and shear stress peaks (and fractures, if any) at the surface is roughly twice the depth to the tip of the dyke. The width of a graben, if it forms, should therefore be roughly twice the depth to the tip of the associated arrested dyke. When applied to the 2009 episode at Harrat Lunayyir, the main results are as follows. The entire 3-7 km wide fracture zone/graben formed during the episode is far too wide to have been generated by induced stresses of a single, arrested dyke. The eastern part of the zone/graben may have been generated by the inferred, arrested dyke, but the western zone primarily by regional extensional loading. The dyke tip was arrested at only a few hundred metres below the surface, the estimated thickness of the uppermost part of the dyke being between about 6 and 12 m. For the inferred dyke length (strike dimension) of about 14 km, this yields a dyke length/thickness ratio between 2400 and 1200

Organisms of the Hubbard Brook Valley, New Hampshire

Treesearch

Richard T. Holmes; Gene E. Likens

1999-01-01

Lists the organisms, both plant and animal, that have been identified by scientists engaged in multidisciplinary ecological research in the Hubbard Brook Valley, New Hampshire, during the past three decades. The Valley encompasses the Hubbard Brook Experimental Forest, Mirror Lake, and nearby areas within the White Mountain region of Grafton County. The species lists...

Giant radiating dyke swarms on Earth and Venus

NASA Technical Reports Server (NTRS)

Ernst, Richard E.; Head, James W.; Parfitt, Elisabeth; Wilson, Lionel; Grosfils, Eric

1993-01-01

On Earth, giant radiating dyke swarms are usually preserved as fan-shaped fragments which have been dismembered from their original configuration by subsequent plate tectonic rifting events. Analysis of the largest fragments and consideration of their original configuration has led to the idea that many swarms are plume related, and that dyke swarms radiate away from plume centers. Magellan radar data reveal abundant intact giant radiating swarms on Venus which are similar in scale and pattern to those on Earth. The absence of intense weathering and plate tectonic processes on Venus accounts for the preservation of the primary radiating patterns. It is characteristic of both Earth and Venus that giant radiating dikes are emplaced laterally for distances of at least 2000 km away from plume centers. At distances beyond the influence of the plume on both Earth and Venus, the radiating dyke pattern is often swept into a linear pattern aligned with the regional stress field. There is tremendous potential synergism between the characterization and analysis of terrestrial dyke swarms (where significant erosion has revealed their structure and emplacement directions at depth) and the giant swarms of Venus (where the complete circumferential structure is preserved, and the surface fracture systems above near surface dikes and the nature of the central source regions are revealed). In this study, we report on the characteristics of radial dyke swarms on Earth and Venus and draw some preliminary comparisons from the two perspectives. In summary, on both planets there is evidence for plume-related magmatic centers associated with vertical and lateral injection of magma over considerable distances (up to at least 2000 km). The abundance of very broadly radiating swarms on Venus supports the notion that the swarms on Earth were radiating over broad sectors at the time of intrusion but were dissected by later events. The Venus data show that a swarm can change from radiating

Strong coupling diagram technique for the three-band Hubbard model

NASA Astrophysics Data System (ADS)

Sherman, A.

2016-03-01

Strong coupling diagram technique equations are derived for hole Green’s functions of the three-band Hubbard model, which describes Cu-O planes of high-Tc cuprates. The equations are self-consistently solved in the approximation, in which the series for the irreducible part in powers of the oxygen-copper hopping constant is truncated to two lowest-order terms. For parameters used for hole-doped cuprates, the calculated energy spectrum consists of lower and upper Hubbard subbands of predominantly copper nature, oxygen bands with a small admixture of copper states and the Zhang-Rice states of mixed nature, which are located between the lower Hubbard subband and oxygen bands. The spectrum contains also pseudogaps near transition frequencies of Hubbard atoms on copper sites.

Geological, geochemical and isotope diversity of 134 Ma dykes from the Florianópolis Dyke Swarm, Paraná Magmatic Province: Geodynamic controls on petrogenesis

NASA Astrophysics Data System (ADS)

Florisbal, L. M.; Janasi, V. A.; Bitencourt, M. F.; Nardi, L. V. S.; Marteleto, N. S.

2018-04-01

The Florianópolis Dyke Swarm (FDS), one of the major dyke swarms belonging to the Early cretaceous (135-131 Ma) Paraná Magmatic Province, is largely dominated by high Sr-Ti-P basalts that are confirmed here as feeders of the unique Urubici (= Khumib) lavas of the Paraná and Edendeka lava piles on the basis of their age and geochemistry. Our study integrates field, petrographic, whole-rock geochemistry, and Sr-Nd-Pb isotope geochemistry of representative samples from three main areas of exposition (Santa Catarina Island, Garopaba and Pinheira beaches), thus encompassing the whole extension of the FDS. Compared to the Urubici lavas, the dykes have usually higher contents of LILE and LREE, more radiogenic Sr and Pb, and more unradiogenic Nd, features attributed to a more pronounced interaction with melts derived from the country rocks registered in the basic magmas that remained in the conduits. Some of these dykes show strongly interactive contacts that must be part of a wider zone of crustal melting, probably more developed at greater depths. Small volumes of intermediate to acidic rocks form the cores of some composite dykes, and correspond to products of fractional crystallization from Urubici basalts contaminated with high Rb/Sr, and U/Th crustal melts (probably derived from Neoproterozoic granites), as indicated by geochemical and Sr-Nd-Pb isotope data. The chemical and isotope signatures of the less contaminated FDS basalts and related Urubici lavas do not show clear evidence of inputs from primitive mantle, and seem heavily influenced by enriched mantle. This suggests that the mantle wedge that was affected by subduction during the Neoproterozoic may have been frozen and coupled to the base of the lithospheric plate where the Early cretaceous magmatism occurred. A control of previous tectonic limits on the sources of the Urubici basalts seems evident, since they seem to be related to the younger lithosphere from the South Domain, related to the Florian

Quartz Crystal Microbalance Studies Of Dimethyl Methylphosphonate Sorption Into Trisilanolphenyl-Poss Films

DTIC Science & Technology

2006-11-06

Transverse shear wave of a quartz crystal with an applied thin film�..�.31 Figure 2.4 Butterworth van - Dyke model for a quartz crystal near...resonance��..�.32 Figure 2.5 Butterworth van - Dyke model for a loaded quartz crystal at resonance...�.34 Figure 2.6 Butterworth van - Dyke model for a...surface chemistry . A thorough understanding of the reaction pathways of CWAs will aid in the development of CWA sensors, environmentally friendly

Dyke-sill relationships in Karoo dolerites as indicators of propagation and emplacement processes of mafic magmas in the shallow crust

NASA Astrophysics Data System (ADS)

Coetzee, A.; Kisters, A. F. M.

2017-04-01

This paper describes the spatial and temporal relationships between Karoo-age (ca. 180 Ma) dolerite dykes and a regional-scale saucer-sill complex from the Secunda (coal mine) Complex in the northeastern parts of the Karoo Basin of South Africa. Unlike parallel dyke swarms of regional extensional settings, mafic dykes commonly show curved geometries and highly variable orientations, short strike extents and complex cross-cutting and intersecting relationships. Importantly, the dyke networks originate from the upper contacts of the first-order dolerite sill-saucer structure and are not the feeders of the saucer complex. Cross-cutting relationships indicate the largely contemporaneous formation of dykes and the inner sill and inclined sheets of the underlying saucer. Systematic dykes form a distinct boxwork-type pattern of two high-angle, interconnected dyke sets. The formation and orientation of this dyke set is interpreted to be related to the stretching of roof strata above elongated magma lobes that facilitated the propagation of the inner sill, similar to the "cracked lid" model described for large saucer complexes in Antarctica. Dyke patterns generally reflect the saucer emplacement process and the associated deformation of wall rocks rather than far-field regional stresses.

An exact sum-rule for the Hubbard model: an historical/pedagogical approach

NASA Astrophysics Data System (ADS)

Di Matteo, S.; Claveau, Y.

2017-07-01

The aim of the present article is to derive an exact integral equation for the Green function of the Hubbard model through an equation-of-motion procedure, like in the original Hubbard papers. Though our exact integral equation does not allow to solve the Hubbard model, it represents a strong constraint on its approximate solutions. An analogous sum rule has been already obtained in the literature, through the use of a spectral moment technique. We think however that our equation-of-motion procedure can be more easily related to the historical procedure of the original Hubbard papers. We also discuss examples of possible applications of the sum rule and propose and analyse a solution, fulfilling it, that can be used for a pedagogical introduction to the Mott-Hubbard metal-insulator transition.

Early Detection of Eruptive Dykes Revealed by Normalized Difference Vegetation Index (NDVI) on Nyiragongo and Etna Volcanoes: Implications for Dyke Wedge Emplacement, Monitoring, and Risk Assessment.

NASA Astrophysics Data System (ADS)

Komorowski, J.; Houlié, N.; Kasereka, C. M.; Ciraba, H.

2006-12-01

Flank-fissure eruptions involve lateral injection and propagation of magma in a volcanic edifice along pre- existing fractures in the direction of a volcanic rift zone (VRZ) where magma intrusion and lava flow production are concentrated over time. Gradual dyke wedge emplacement on volcano flanks and in VRZ's does not necessarily trigger large amplitude deformation signals susceptible to be recorded months or even years before the actual eruption. We show that active and potentially eruptive areas in a VRZ can be detected up to 2 years before the arrival to the surface of the final eruptive dyke and venting of lava flows by processing satellite images applying a Normalized Difference Vegetation Index (NDVI) algorithm. A positive NDVI anomaly is indicative of excessive photosynthetic plant activity. A posteriori analysis of satellite images reveal that a high- NDVI linear anomaly was apparent in vegetated areas of VRZ's on Etna from 2000 to 2002 and on Nyiragongo in June 2001, several months to years before eruptive fractures formed directly above the NDVI anomaly. We propose that the observed NDVI linear anomalies are the signature of the integrated physico-chemical effects (increased heat and CO2 flux, H2O condensation) caused by the structurally-controlled progressive injection and propagation, in a VRZ and a few months to years before the eruption, of a series of dykes (dyke wedge) that did not reach the surface. We focus of Nyiragongo volcano where historical flank-fissure eruptions from lava lake drainage in 1977 and 2002 show a link with tectonics of the Kivu rift (western branch of the East African Rift System). In 2002, dykes were injected in the southern VRZ bounded by Kivu rift normal faults and propagated over 14 km producing lava flows that caused widespread destruction in the city of Goma. Data from Nyiragongo suggest that as a dyke wedge is formed and repeatedly reactivated, final eruptive dykes can be injected easily and can propagate rapidly further

Early Jurassic mafic dykes from the Xiazhuang ore district (South China): Implications for tectonic evolution and uranium metallogenesis

NASA Astrophysics Data System (ADS)

Wang, Lian-Xun; Ma, Chang-Qian; Lai, Zhong-Xin; Marks, Michael A. W.; Zhang, Chao; Zhong, Yu-Fang

2015-12-01

A comprehensive study on zircon U-Pb age dating, whole-rock geochemistry and Sr-Nd isotope data has been conducted on the mafic rocks of the Xiazhuang uranium ore district and adjacent regions in South China. Based on field work and petrographic features, three rock types (the Kuzhukeng gabbro, the WNW-trending dolerite dykes and the NNE-trending lamprophyre dykes) are distinguished. Early Jurassic SHRIMP and LA-ICPMS ages of zircon for the Kuzhukeng gabbro (198 ± 1 Ma) and WNW-trending dolerite dykes (193 ± 4 Ma) have been obtained, which are 50 Ma older than previously thought (being Cretaceous). These geochronologic data provide new evidence for the rarely identified Early Jurassic magmatisms in South China. Whole-rock geochemical data for the Kuzhukeng gabbro and WNW-trending dolerite dykes are similar, both of which being higher in FeO and TiO2 but lower in SiO2 and K2O than the NNE-trending lamprophyre dykes. Trace element characteristics and Sr-Nd isotope data indicate arc-like signatures similar to the Cretaceous southeast coast basalts of China for the lamprophyre dykes, but an OIB-like geochemical affinity for the high-TiO2 mafic rocks similar to the Permo/Triassic Emeishan flood basalts and the Middle Jurassic Ningyuan alkaline basalts. We propose that the lamprophyre dykes formed in an arc volcanic system driven by the subduction of the paleo-Pacific plate. In contrast, the Kuzhukeng gabbro and associated dolerite dykes record the post-orogenic (Indosinian) extension event in the Tethyan tectonic regime. This further implies that the Indosinian extension may have lasted until the Early Jurassic, and therefore, the subduction of the paleo-Pacific plate in south China was probably later than this period. Most U deposits of the Xiazhuang area are located at the intersection between the WNW-trending dolerite dykes and the NNE-trending faults within the Triassic granites of eastern Guidong complex, South China. Previous metallogenesis studies assumed that

Seismic footprints of shallow dyke propagation at Etna, Italy.

PubMed

Falsaperla, Susanna; Neri, Marco

2015-07-15

One of the key issues in forecasting volcanic eruptions is to detect signals that can track the propagation of dykes towards the surface. Continuous monitoring of active volcanoes helps significantly in achieving this goal. The seismic data presented here are unique, as they document surface faulting processes close (tens to a few hundred meters) to their source, namely the dyke tip. They originated nearby - and under - a seismic station that was subsequently destroyed by lava flows during eruptive activity at Etna volcano, Italy, in 2013. On February 20, a ~600 m-long and ~120 m wide NW-SE fracture field opened at an altitude between 2750 and 2900 m. The consequent rock dislocation caused the station to tilt and offset the seismic signal temporarily. Data acquisition continued until the arrival of the lava flow that led to the breakdown of the transmission system. Shallow ground fracturing and repeated low-frequency oscillations occurred during two stages in which the seismic signal underwent a maximum offset ~2.57 × 10(4) nm/s. Bridging instrumental recordings, fieldwork and conceptual modelling, these data are interpreted as the seismic footprints of a magmatic dyke intrusion that moved at speed ~0.02 m/s (first stage) and 0.46 m/s (second stage).

Ultramafic lavas and high-Mg basaltic dykes from the Othris ophiolite complex, Greece

NASA Astrophysics Data System (ADS)

Baziotis, Ioannis; Economou-Eliopoulos, Maria; Asimow, Paul D.

2017-09-01

We evaluate the petrography and geochemistry of an unusual suite of subduction-related Phanerozoic high-MgO rocks from the Othris ophiolite complex in Greece, some of which have previously been described as komatiitic lavas. In particular, we study ultramafic, olivine-phyric lavas from the Agrilia area and high-Mg basaltic dykes from the Pournari area. We seek to define primary magmatic MgO contents and initial liquidus temperatures as well as the differentiation sequence and cooling rates experienced by the lavas and dykes. One of our goals is to relate the Othris case to known komatiite and boninite occurrences and to address whether Othris documents an important new constraint on the temporal evolution of ambient mantle temperature, plume-related magmatism, and subduction of oceanic lithosphere. We conclude that, despite whole-rock MgO contents of 31-33 wt%, the olivine-phyric lavas at Agrilia had an upper limit liquid MgO content of 17 wt% and are therefore picrites, not komatiites. The Agrilia lavas contain the unusual Ti-rich pyroxenoid rhönite; we discuss the significance of this occurrence. In the case of the Pournari high-Mg dykes, the distinctive dendritic or plumose clinopyroxene texture, though it resembles in some ways the classic spinifex texture of komatiites, is simply evidence of rapid cooling at the dyke margin and not evidence of extraordinarily high liquidus temperatures. We correlate the dendritic texture with disequilibrium mineral chemistry in clinopyroxene to constrain the cooling rate of the dyke margins.

Magmatic dyke swarms of the south shetland islands volcanic arc, west-antarctica - tracers of geodynamic history

NASA Astrophysics Data System (ADS)

Kraus, St.; Miller, H.

2003-04-01

Magmatic dykes are essential components of volcanic arcs, following joint systems and fracture zones. This work aims to reconstruct the deformational and intrusive history of the northern part of the Antarctic Peninsula by combining structural information with the geochemistry, isotopy and age of the dykes. On the South Shetland Islands volcanic activity began about 130 Ma ago. From Mid to Late Eocene (49-34 Ma) the northern Antarctic Peninsula and southern South America underwent extensional tectonics, which led to sea-floor spreading in the Drake Passage 28 Ma ago. Subsequent slab-rollback caused arc-extension and the opening of the Bransfield Rift as a backarc-basin between 4 and 1.3 Ma ago. Very slow subduction (1mm/a) at the South Shetland trench continues until the present day. Several changes of subduction direction caused crucial variations regarding the tectonic regime in the overlying South Shetland block, being the reason for the shifting strike of the dykes. Several dyke systems were mapped in areas of up to 100000m2, with the outcrop situation being good enough to observe plenty of relative age relationships. ICP-MS geochemical analysis on 132 dykes shows, as expected, that the majority of them correspond to a typical subduction-related calcalcalic suite, ranging from basalts to rhyolites. Nevertheless, some dykes show shoshonitic characteristics and are maybe related to an early stage extensional crustal regime. This is supported by the relative ages observed in the field, indicating, that these dykes belong to the oldest ones outcropping in the investigated area. In one case, the geochemical behaviour of the dyke corresponds clearly to adacitic conditions, being a hint on partially molten subducted oceanic crust. In several areas (e.g. Potter Peninsula, King George Island, and Hurd Peninsula, Livingston Island) a strong correlation between chemism and strike of the dykes - and therefore the tectonic regime at the time of intrusion - is observed. Ce

Eocene slab breakoff of Neotethys as suggested by dioritic dykes in the Gangdese magmatic belt, southern Tibet

NASA Astrophysics Data System (ADS)

Ma, Xuxuan; Xu, Zhiqin; Meert, Joseph G.

2016-04-01

The Gangdese magmatic belt in southern Tibet demarcates an important boundary between the Indian and Eurasian plates. Due to its location and magmatic evolutionary history, it is key to understanding both the history of Neotethys closure and the Indo-Asian collisional process. This study presents new geochronological and geochemical data for dioritic dykes in the southern Gangdese magmatic belt in southern Tibet. U-Pb geochronological results reveal that the dykes were emplaced at ca. 41 Ma and thus broadly coeval with the 40-38 Ma Dazi volcanics and the 42-40 Ma Gaoligong-Tengliang basaltic dykes. Geochemically, these dykes are characterized by alkaline signature, high Mg# (57-63) and low TiO2 contents ( 0.9-1.0), showing notable enrichment of light rare earth elements relative to the heavy rare earth elements, enrichment of incompatible elements (i.e. Cs, Rb, Ba, Th and U), and depletion of high field strength elements (i.e. Nb, Ta and Ti). In addition, a large variation of zircon εHf(t) values (- 10 to + 13) was shown, implying heterogeneity of magma sources. A heterogeneous source is also suggested by the occurrence of xenocrysts in the dykes. These observations suggest that the magma source of the dykes was dominated by partial melting of lithospheric mantle and then subsequently contaminated by crustal material during ascent. In combination with other geological data in the region, we suspect that the slab slicing of the Neotethys played a key role in the formation of the lithospheric mantle-derived dioritic dykes and adakitic granite, asthenosphere-derived volcanics, basaltic dykes, as well as the recently reported strongly fractionated granites.

Earth's magnetic field strength in the Early Cambrian: Thellier paleointensity estimates of Itabaiana mafic dykes, Northeast Brazil

NASA Astrophysics Data System (ADS)

Trindade, R. I. F.; Macouin, M.; Poitou, C.; Chauvin, A.; Hill, M.

2012-04-01

Thellier's paleointensity and microwave paleointensity experiments were carried out in Early Cambrian dykes from Itabaiana (NE Brazil) dated at 525 ±5 Ma. A previous paleomagnetic study on these dykes reveals a very stable characteristic component, whose thermoremanent nature is confirmed by positive baked contact tests performed in three different dykes. The main magnetic carrier is Ti-poor to pure magnetite in the PSD to SD domain state. Hysteresis parameters and first-order reversal curve (FORC) diagrams will be presented in order to apprehend the two different behaviors that characterize the samples during paleointensity experiments. From the 96 samples (from 13 dykes) analyzed in two laboratories using slightly different Thellier's experimental protocols, we have retained 12 samples (3 dykes) for paleointensity estimates. Paleointensity values range from 18.1 up to 40 μΤ. This corresponds to equivalent VDMs of 4.3 ± 0.5, 4.4 ± 1.4 and 5.3 ± 0.9 x 1022 Am2, for the three dykes respectively. These results, the first obtained for rapidly cooled Cambrian rocks, document a moderate Earth field in the Precambrian-Cambrian transition.

Petrogenesis of peralkaline granite dykes of the Straumsvola complex, western Dronning Maud Land, Antarctica

NASA Astrophysics Data System (ADS)

Harris, Chris; Dreyer, Tanya; le Roux, Petrus

2018-01-01

Peralkaline syenite and granite dykes cut the Straumsvola nepheline syenite pluton in Western Dronning Maud Land, Antarctica. The average peralkalinity index (PI = molecular Al/[Na + K]) of the dykes is 1.20 ( n = 29) and manifests itself in the presence of the Zr silicates eudialyte, dalyite and vlasovite, and the Na-Ti silicate, narsarsukite. The dykes appear to have intruded during slow cooling of the nepheline syenite pluton, and the petrogenetic relationship of the dykes and the pluton cannot be related to closed-system processes at low pressure, given the thermal divide that exists between silica-undersaturated and oversaturated magmas. Major and trace element variations in the dykes are consistent with a combination of fractional crystallization of parental peralkaline magma of quartz trachyte composition, and internal mineral segregation prior to final solidification. The distribution of accessory minerals is consistent with late-stage crystallization of isolated melt pockets. The dykes give an Rb-Sr isochron age of 171 ± 4.4 Ma, with variable initial 87Sr/86Sr ratio (0.7075 ± 0.0032), and have an average ɛ Nd of - 12.0. Quartz phenocrysts have δ18O values of 8.4-9.2‰, which are generally in O-isotope equilibrium with bulk rock. Differences in the δ18O values of quartz and aegirine (average Δquartz-aegirine = 3.5‰) suggest aegirine formation temperatures around 500 °C, lower than expected for a felsic magma, but consistent with poikilitic aegirine that indicates subsolidus growth. The negative ɛ Nd (< - 10) and magma δ18O values averaging 8.6‰ (assuming Δquartz-magma = 0.6‰) are inconsistent with a magma produced by closed-system fractional crystallization of a mantle-derived magma. By contrast, the nepheline syenite magma had mantle-like δ18O values and much less negative ɛ Nd (average - 3.1, n = 3). The country rock has similar δ18O values to the granite dykes (average 8.0‰, n = 108); this means that models for the petrogenesis of

Davidoff-Dyke-Masson Syndrome Presenting as Childhood Schizophrenia.

ERIC Educational Resources Information Center

White, James H.; Rust, John B.

1979-01-01

The article presents a case history of a child displaying symptoms of schizophrenia, seizures, and retardation without neurological abnormalities, which were eventually diagnosed as being due to Davidoff-Dyke-Masson syndrome, a condition involving gross anatomical brain pathology. (DLS)

Fermionic Symmetry-Protected Topological Phase in a Two-Dimensional Hubbard Model

DOE PAGES

Chen, Cheng-Chien; Muechler, Lukas; Car, Roberto; ...

2016-08-25

We study the two-dimensional (2D) Hubbard model using exact diagonalization for spin-1/2 fermions on the triangular and honeycomb lattices decorated with a single hexagon per site. In certain parameter ranges, the Hubbard model maps to a quantum compass model on those lattices. On the triangular lattice, the compass model exhibits collinear stripe antiferromagnetism, implying d-density wave charge order in the original Hubbard model. On the honeycomb lattice, the compass model has a unique, quantum disordered ground state that transforms nontrivially under lattice reflection. The ground state of the Hubbard model on the decorated honeycomb lattice is thus a 2D fermionicmore » symmetry-protected topological phase. This state—protected by time-reversal and reflection symmetries—cannot be connected adiabatically to a free-fermion topological phase.« less

Mass-imbalanced ionic Hubbard chain

NASA Astrophysics Data System (ADS)

Sekania, Michael; Baeriswyl, Dionys; Jibuti, Luka; Japaridze, George I.

2017-07-01

A repulsive Hubbard model with both spin-asymmetric hopping (t↑≠t↓ ) and a staggered potential (of strength Δ ) is studied in one dimension. The model is a compound of the mass-imbalanced (t↑≠t↓ ,Δ =0 ) and ionic (t↑=t↓ ,Δ >0 ) Hubbard models, and may be realized by cold atoms in engineered optical lattices. We use mostly mean-field theory to determine the phases and phase transitions in the ground state for a half-filled band (one particle per site). We find that a period-two modulation of the particle (or charge) density and an alternating spin density coexist for arbitrary Hubbard interaction strength, U ≥0 . The amplitude of the charge modulation is largest at U =0 , decreases with increasing U and tends to zero for U →∞ . The amplitude for spin alternation increases with U and tends to saturation for U →∞ . Charge order dominates below a value Uc, whereas magnetic order dominates above. The mean-field Hamiltonian has two gap parameters, Δ↑ and Δ↓, which have to be determined self-consistently. For U Uc they have different signs, and for U =Uc one gap parameter jumps from a positive to a negative value. The weakly first-order phase transition at Uc can be interpreted in terms of an avoided criticality (or metallicity). The system is reluctant to restore a symmetry that has been broken explicitly.

Disordered Supersolids in the Extended Bose-Hubbard Model

DOE PAGES

Lin, Fei; Maier, T. A.; Scarola, V. W.

2017-10-06

The extended Bose-Hubbard model captures the essential properties of a wide variety of physical systems including ultracold atoms and molecules in optical lattices, Josephson junction arrays, and certain narrow band superconductors. It exhibits a rich phase diagram including a supersolid phase where a lattice solid coexists with a superfluid. We use quantum Monte Carlo to study the supersolid part of the phase diagram of the extended Bose-Hubbard model on the simple cubic lattice. We add disorder to the extended Bose-Hubbard model and find that the maximum critical temperature for the supersolid phase tends to be suppressed by disorder. But wemore » also find a narrow parameter window in which the supersolid critical temperature is enhanced by disorder. Our results show that supersolids survive a moderate amount of spatial disorder and thermal fluctuations in the simple cubic lattice.« less

Polycrystalline magma behaviour in dykes: Insights from high-resolution numerical models

NASA Astrophysics Data System (ADS)

Yamato, Philippe; Duretz, Thibault; Tartèse, Romain; May, Dave

2013-04-01

The presence of a crystalline load in magmas modifies their effective rheology and thus their flow behaviour. In dykes, for instance, the presence of crystals denser than the melt reduces the ascent velocity and modifies the shape of the velocity profile from a Newtonian Poiseuille flow to a Bingham type flow. Nevertheless, several unresolved issues still remain poorly understood and need to be quantified: (1) What are the mechanisms controlling crystals segregation during magma ascent in dykes? (2) How does crystals transportation within a melt depend on their concentration, geometry, size and density? (3) Do crystals evolve in isolation to each other or as a cluster? (4) What is the influence of considering inertia of the melt within the system? In this study, we present numerical models following the setup previously used in Yamato et al. (2012). Our model setup simulates an effective pressure gradient between the base and the top of a channel (representing a dyke), by pushing a rigid piston into a magmatic mush that comprised crystals and melt and perforated by a hole. The initial resolution of the models (401x1551 nodes) has been doubled in order to ensure that the smallest crystalline fractions are sufficiently well resolved. Results show that the melt phase can be squeezed out from a crystal-rich magma when subjected to a given pressure gradient range and that clustering of crystals might be an important parameter controlling their behaviour. This demonstrates that crystal-melt segregation in dykes during magma ascent constitutes a viable mechanism for magmatic differentiation of residual melts. These results also explain how isolated crystal clusters and melt pockets, with different chemistry, can be formed. In addition, we discuss the impact of taking into account inertia in our models. Reference: Yamato, P., Tartèse, R., Duretz, T., May, D.A., 2012. Numerical modelling of magma transport in dykes. Tectonophysics 526-529, 97-109.

Variscan potassic dyke magmatism of durbachitic affinity at the southern end of the Bohemian Massif (Lower Austria)

NASA Astrophysics Data System (ADS)

Zeitlhofer, Helga; Grasemann, Bernhard; Petrakakis, Konstantin

2016-06-01

Dykes in the Strudengau area (SW Moldanubian Zone, Austria) can be mineralogically divided into lamprophyres (spessartites and kersantites) and felsic dykes (granite porphyries, granitic dykes and pegmatoid dykes). Geochemical analyses of 11 lamprophyres and 7 felsic dykes show evidence of fractional crystallization. The lamprophyres are characterized by metaluminous compositions, intermediate SiO2 contents and high amounts of MgO and K2O; these rocks have high Ba (800-3000 ppm) and Sr (250-1000 ppm) contents as well as an enrichment of large-ion lithophile elements over high field strength elements, typical for enriched mantle sources with variable modifications due to fractionation and crustal contamination. This geochemical signature has been reported from durbachites (biotite- and K feldspar-rich mela-syenites particularly characteristic of the Variscan orogen in Central Europe). For most major elements, calculated fractionation trends from crystallization experiments of durbachites give an excellent match with the data from the Strudengau dykes. This suggests that the lamprophyres and felsic dykes were both products of fractional crystallization and subsequent magma mixing of durbachitic and leucogranitic melts. Rb-Sr geochronological data on biotite from five undeformed kersantites and a locally deformed granite porphyry gave cooling ages of c. 334-318 Ma, indicating synchronous intrusion of the dykes with the nearby outcropping Weinsberger granite (part of the South Bohemian Batholith, c. 330-310 Ma). Oriented matrix biotite separated from the locally deformed granite porphyry gave an Rb-Sr age of c. 318 Ma, interpreted as a deformation age during extensional tectonics. We propose a large-scale extensional regime at c. 320 Ma in the Strudengau area, accompanied by plutonism of fractionated magmas of syncollisional mantle-derived sources, mixed with crustal components. This geodynamic setting is comparable to other areas in the Variscan belt documenting an

Seismic footprints of shallow dyke propagation at Etna, Italy

PubMed Central

Falsaperla, Susanna; Neri, Marco

2015-01-01

One of the key issues in forecasting volcanic eruptions is to detect signals that can track the propagation of dykes towards the surface. Continuous monitoring of active volcanoes helps significantly in achieving this goal. The seismic data presented here are unique, as they document surface faulting processes close (tens to a few hundred meters) to their source, namely the dyke tip. They originated nearby - and under - a seismic station that was subsequently destroyed by lava flows during eruptive activity at Etna volcano, Italy, in 2013. On February 20, a ~600 m-long and ~120 m wide NW-SE fracture field opened at an altitude between 2750 and 2900 m. The consequent rock dislocation caused the station to tilt and offset the seismic signal temporarily. Data acquisition continued until the arrival of the lava flow that led to the breakdown of the transmission system. Shallow ground fracturing and repeated low-frequency oscillations occurred during two stages in which the seismic signal underwent a maximum offset ~2.57 × 104 nm/s. Bridging instrumental recordings, fieldwork and conceptual modelling, these data are interpreted as the seismic footprints of a magmatic dyke intrusion that moved at speed ~0.02 m/s (first stage) and 0.46 m/s (second stage). PMID:26173557

Effect of volcanic dykes on coastal groundwater flow and saltwater intrusion: A field-scale multiphysics approach and parameter evaluation

NASA Astrophysics Data System (ADS)

Comte, J.-C.; Wilson, C.; Ofterdinger, U.; González-Quirós, A.

2017-03-01

Volcanic dykes are common discrete heterogeneities in aquifers; however, there is a lack of field examples of, and methodologies for, comprehensive in situ characterization of their properties with respect to groundwater flow and solute transport. We have applied an integrated multiphysics approach to quantify the effect of dolerite dykes on saltwater intrusion in a coastal sandstone aquifer. The approach involved ground geophysical imaging (passive magnetics and electrical resistivity tomography), well hydraulic testing, and tidal propagation analysis, which provided constraints on the geometry of the dyke network, the subsurface saltwater distribution, and the sandstone hydrodynamic properties and connectivity. A three-dimensional variable-density groundwater model coupled with a resistivity model was further calibrated using groundwater and geophysical observations. A good agreement of model simulations with tide-induced head fluctuations, geophysically derived pore water salinities, and measured apparent resistivities was obtained when dykes' hydraulic conductivity, storativity, and effective porosity are respectively about 3, 1, and 1 orders of magnitude lower than the host aquifer. The presence of the dykes results in barrier-like alterations of groundwater flow and saltwater intrusion. Preferential flow paths occur parallel to observed dyke orientations. Freshwater inflows from upland recharge areas concentrate on the land-facing side of the dykes and saltwater penetration is higher on their sea-facing side. This has major implications for managing groundwater resources in dyke-intruded aquifers, including in coastal and island regions and provides wider insights on preferential pathways of groundwater flow and transport in highly heterogeneous aquifer systems.

Dykes as Tracers of Continental Break-up: Argon Geochronology of Mesozoic Flood Basalts of Western Dronning Maud Land, Antarctica

NASA Astrophysics Data System (ADS)

Fazel, A.; Kelley, S. P.; Leat, P. T.; Hawkesworth, C.

2003-04-01

The British Antarctic Survey MAMOG Project (Magmatism as A Monitor Of Gondwana break up processes) is investigating the mantle processes that resulted in the eruption of the Karoo-Dronning Maud Land CFB suite and its importance in our understanding of the initial stages of Gondwana break-up. One of the problems of understanding the 180Ma continental flood basalts is knowing their precise age. Since they are erupted through more ancient (1000Ma) rocks we have to use the Ar-Ar dating technique to determine whether they are related to the continental break-up or are part of some older event. In addition, we have analysed the chemistry of the dykes and can relate them to several chemical types, the challenge is to test if dykes with similar chemistry all erupted at the same time. It has been suggested that many of the Jurassic dykes in western DML fed the CFB suite that is higher in the volcanic pile. We have found dykes of different ages in the Kirwanveggen and Ahlmannryggen regions of western DML. Although more work needs to be done, we now have mounting evidence to suggest that episodes of chemically similar magmatism in DML stretched from 1000-180Ma with some events separated by hundreds of millions of years implying a lithospheric mantle control on magma composition. The precise ages for the dykes are slightly younger than the accepted ages for the South African Karoo province. In addition to determining the ages of dyke intrusions, a high spatial resolution UV laser has been used to measure argon loss from diorite host rocks adjacent to the dykes. Progressive heating of the country rock during magma emplacement causes argon loss. Thermal modelling of the dykes will allow us to differentiate between various heat loss mechanisms and give an indication of the style, volume and rapidity of magma flow through the dyke. The UV results have shown that some of the dykes were active for long periods probably feeding the surface lava eruptions.

New paleomagnetic results on ˜ ˜2367 Ma Dharwar giant dyke swarm, Dharwar craton, southern India: implications for Paleoproterozoic continental reconstruction

NASA Astrophysics Data System (ADS)

Babu, N. Ramesh; Venkateshwarlu, M.; Shankar, Ravi; Nagaraju, E.; Parashuramulu, V.

2018-02-01

Here we report new paleomagnetic results and precise paleopole position of the extensional study on ˜ 2367 Ma mafic giant radiating dyke swarm in the Dharwar craton, southern India. We have sampled 29 sites on 12 dykes from NE-SW Karimnagar-Hyderabad dykes and Dhone-Gooty sector dykes, eastern Dharwar craton to provide unambiguous paleomagnetism evidence on the spectacular radiating dyke swarm and thereby strengthening the presence of single magmatic event at ˜ 2367 Ma. A total of 158 samples were subjected to detailed alternating field and thermal demagnetization techniques and the results are presented here along with previously reported data on the same dyke swarm. The remanent magnetic directions are showing two components, viz., seven sites representing four dykes show component (A) with mean declination of 94{{}°} and mean inclination of - 70{{}°} (k=87, α_{95}=10{{}°}) and corresponding paleopole at 16{{}°}N, 41{{}°}E (dp=15{{}°} and dm=17{{}°}) and 22 sites representing 8 dykes yielded a component (B) with mean declination of 41{{}°} and mean inclination of - 21{{}°} (k=41, α_{95}=9{{}°}) with a paleopole at 41{{}°}N, 200{{}°}E (dp=5{{}°} and dm=10{{}°}). Component (A) results are similar to the previously reported directions from the ˜ 2367 Ma dyke swarm, which have been confirmed fairly reliably to be of primary origin. The component (B) directions appear to be strongly overprinted by the 2080 Ma event. The grand mean for the primary component (A) combined with earlier reported studies gives mean declination of 97{{}°} and mean inclination of - 79{{}°} (k=55, α_{95}=3{{}°}) with a paleopole at 15{{}°}N, 57{{}°}E (dp=5{{}°}, dm=6{{}°}). Paleogeographical position for the Dharwar craton at ˜ 2367 Ma suggests that there may be a chance to possible spatial link between Dharwar dykes of Dharwar craton (India), Widgemooltha and Erayinia dykes of Yilgarn craton (Australia), Sebanga Poort Dykes of Zimbabwe craton (Africa) and Karelian

Capturing nonlocal interaction effects in the Hubbard model: Optimal mappings and limits of applicability

NASA Astrophysics Data System (ADS)

van Loon, E. G. C. P.; Schüler, M.; Katsnelson, M. I.; Wehling, T. O.

2016-10-01

We investigate the Peierls-Feynman-Bogoliubov variational principle to map Hubbard models with nonlocal interactions to effective models with only local interactions. We study the renormalization of the local interaction induced by nearest-neighbor interaction and assess the quality of the effective Hubbard models in reproducing observables of the corresponding extended Hubbard models. We compare the renormalization of the local interactions as obtained from numerically exact determinant quantum Monte Carlo to approximate but more generally applicable calculations using dual boson, dynamical mean field theory, and the random phase approximation. These more approximate approaches are crucial for any application with real materials in mind. Furthermore, we use the dual boson method to calculate observables of the extended Hubbard models directly and benchmark these against determinant quantum Monte Carlo simulations of the effective Hubbard model.

Collective Kondo effect in the Anderson-Hubbard lattice

NASA Astrophysics Data System (ADS)

Fazekas, P.; Itai, K.

1997-02-01

The periodic Anderson model is extended by switching on a Hubbard U for the conduction electrons. We use the Gutzwiller variational method to study the nearly integral valent limit. The lattice Kondo energy contains the U-dependent chemical potential of the Hubbard subsystem in the exponent, and the correlation-induced band narrowing in the prefactor. Both effects tend to suppress the Kondo scale, which can be understood to result from the blocking of hybridization. At half-filling, we find a Brinkman-Rice-type transition from a Kondo insulator to a Mott insulator.

Ground-state phase diagram of the repulsive fermionic t -t' Hubbard model on the square lattice from weak coupling

NASA Astrophysics Data System (ADS)

Šimkovic, Fedor; Liu, Xuan-Wen; Deng, Youjin; Kozik, Evgeny

2016-08-01

We obtain a complete and numerically exact in the weak-coupling limit (U →0 ) ground-state phase diagram of the repulsive fermionic Hubbard model on the square lattice for filling factors 0 Van Hove singularity line, joining the ferromagnetic and antiferromagnetic points, another region with high values of λ can be found at quarter filling and t'=0.5 due to the presence of a line of nesting at t'≥0.5 . The results can serve as benchmarks for controlled nonperturbative methods and guide the ongoing search for high-Tc superconductivity in the Hubbard model.

Crystallisation sequence and magma evolution of the De Beers dyke (Kimberley, South Africa)

NASA Astrophysics Data System (ADS)

Soltys, Ashton; Giuliani, Andrea; Phillips, David

2018-06-01

We present petrographic and mineral chemical data for a suite of samples derived from the De Beers dyke, a contemporaneous, composite intrusion bordering the De Beers pipe (Kimberley, South Africa). Petrographic features and mineral compositions indicate the following stages in the evolution of this dyke: (1) production of antecrystic material by kimberlite-related metasomatism in the mantle (i.e., high Cr-Ti phlogopite); (2) entrainment of wall-rock material during ascent through the lithospheric mantle, including antecrysts; (3) early magmatic crystallisation of olivine (internal zones and subsequently rims), Cr-rich spinel, rutile, and magnesian ilmenite, probably on ascent to the surface; and (4) crystallisation of groundmass phases (i.e., olivine rinds, Fe-Ti-rich spinels, perovskite, apatite, monticellite, calcite micro-phenocrysts, kinoshitalite-phlogopite, barite, and baddeleyite) and the mesostasis (calcite, dolomite, and serpentine) on emplacement in the upper crust. Groundmass and mesostasis crystallisation likely forms a continuous sequence with deuteric/hydrothermal modification. The petrographic features, mineralogy, and mineral compositions of different units within the De Beers dyke are indistinguishable from one another, indicating a common petrogenesis. The compositions of antecrysts (i.e., high Cr-Ti phlogopite) and magmatic phases (e.g., olivine rims, magnesian ilmenite, and spinel) overlap those from the root zone intrusions of the main Kimberley pipes (i.e., Wesselton, De Beers, Bultfontein). However, the composition of these magmatic phases is distinct from those in `evolved' intrusions of the Kimberley cluster (e.g., Benfontein, Wesselton water tunnel sills). Although the effects of syn-emplacement flow processes are evident (e.g., alignment of phases parallel to contacts), there is no evidence that the De Beers dyke has undergone significant pre-emplacement crystal fractionation (e.g., olivine, spinel, ilmenite). This study demonstrates the

Dynamical critical exponent of the Jaynes-Cummings-Hubbard model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hohenadler, M.; Aichhorn, M.; Schmidt, S.

2011-10-15

An array of high-Q electromagnetic resonators coupled to qubits gives rise to the Jaynes-Cummings-Hubbard model describing a superfluid to Mott-insulator transition of lattice polaritons. From mean-field and strong-coupling expansions, the critical properties of the model are expected to be identical to the scalar Bose-Hubbard model. A recent Monte Carlo study of the superfluid density on the square lattice suggested that this does not hold for the fixed-density transition through the Mott lobe tip. Instead, mean-field behavior with a dynamical critical exponent z=2 was found. We perform large-scale quantum Monte Carlo simulations to investigate the critical behavior of the superfluid densitymore » and the compressibility. We find z=1 at the tip of the insulating lobe. Hence the transition falls in the three-dimensional XY universality class, analogous to the Bose-Hubbard model.« less

Two-dimensional Anderson-Hubbard model in the DMFT + {Sigma} approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuchinskii, E. Z., E-mail: kuchinsk@iep.uran.ru; Kuleeva, N. A.; Nekrasov, I. A.

The density of states, the dynamic (optical) conductivity, and the phase diagram of the paramagnetic two-dimensional Anderson-Hubbard model with strong correlations and disorder are analyzed within the generalized dynamical mean field theory (DMFT + {Sigma} approximation). Strong correlations are accounted by the DMFT, while disorder is taken into account via the appropriate generalization of the self-consistent theory of localization. We consider the two-dimensional system with the rectangular 'bare' density of states (DOS). The DMFT effective single-impurity problem is solved by numerical renormalization group (NRG). The 'correlated metal,' Mott insulator, and correlated Anderson insulator phases are identified from the evolution ofmore » the density of states, optical conductivity, and localization length, demonstrating both Mott-Hubbard and Anderson metal-insulator transitions in two-dimensional systems of finite size, allowing us to construct the complete zero-temperature phase diagram of the paramagnetic Anderson-Hubbard model. The localization length in our approximation is practically independent of the strength of Hubbard correlations. But the divergence of the localization length in a finite-size two-dimensional system at small disorder signifies the existence of an effective Anderson transition.« less

Late Cretaceous dacitic dykes swarm from Central Iran, a trace for amphibolite melting in a subduction zone

NASA Astrophysics Data System (ADS)

Nosouhian, N.; Torabi, G.; Arai, S.

2016-05-01

Late Cretaceous Bayazeh dyke swarm is situated in the western part of the Central-East Iranian Microcontinent (CEIM). These dykes with a dominant northeast-southwest trend occur in the Eastern margin of the Yazd block. They cross cut the Lower Cretaceous sedimentary rocks. The length of the Bayazeh dykes occasionally reaches up to the 2 km. Rock forming minerals of these dykes are plagioclase (andesine and oligoclase), amphibole (magnesio-hastingsitic hornblende, magnesio-hornblende and tschermakitic hornblende), quartz, K-feldspar (orthoclase), zircon and apatite. Secondary minerals are chlorite (pycnochlorite), albite, magnetite and calcite. The main textures are porphyritic, glomeroporphyritic and poikilitic. The felsic character of the Bayazeh dacitic dykes is shown by their high SiO2 (62.70 to 64.60 wt %) and low [Fe2O3* + MgO + MnO + TiO2] (average 4.64 wt %) contents. These dykes represent the peraluminous to metaluminous nature and their Na2O and K2O values are 5.20-7.14 and 1.51-2.59 wt %, respectively, which reveal their sodic chemistry. The trace element characteristics are the LREE enrichment relative to HREE, [La/Yb]CN = 13.27-22.99, and slightly negative or positive Eu anomaly. These geochemical characteristics associated with low Nb/La (0.16-0.25), Yb/Nd (0.04-0.05) and high Zr/Sm (37.60-58.25) ratios indicate that the melting of a metamorphosed subducted oceanic crust is occurred where the residual mineral assemblage is dominated by garnet amphibolite. The chemical compositions of the Bayazeh dykes resemble those of slab-derived tonalite-trondhjemite-granodiorite (TTG) series. They were formed by subduction of Mesozoic Neo-Tethys -related Nain and Ashin oceanic crusts.

Developing Thermal Density Functional Theory Using the Asymmetric Hubbard Dimer

NASA Astrophysics Data System (ADS)

Smith, Justin Clifford

In this dissertation, I introduce both ground-state and thermal density functional theory. Throughout I use the asymmetric two-site Hubbard model, called the Hubbard dimer for short, to better understand and/or develop these theories. This model is used because it can be solved analytically and it contains all the necessary physics while still being conceptually simple enough to tease apart the various aspects of density functional theory. Ground-state density functional theory has seen broad use in many disciplines including physics, chemistry, geology, and material science and has led to a number of important physical and technological successes. In the first two chapters I elucidate the behavior of the ground-state theory using the Hubbard dimer. The simplicity of the model allows me to showcase aspects of the theory that are common points of confusion within the electronic structure community, e.g. the fundamental gap problem. The next two chapters focus on thermal density functional theory which has been coming to prominence as the study of warm dense matter has become a growing interest at the national laboratories and in the astronomical body community. The Hubbard dimer allows me to do the first ever exact thermal density functional theory calculation. In this work I am better able to understand the approximations used in thermal density functional theory and can point to why they succeed and fail. This also allows me to illustrate old conditions and derive new ones. I conclude with an overview of the work and a few different directions in which the asymmetric Hubbard dimer could be used further.

Magnetic fabric and flow direction in the Ediacaran Imider dyke swarms (Eastern Anti-Atlas, Morocco), inferred from the Anisotropy of Magnetic Susceptibility (AMS)

NASA Astrophysics Data System (ADS)

Otmane, Khadija; Errami, Ezzoura; Olivier, Philippe; Berger, Julien; Triantafyllou, Antoine; Ennih, Nasser

2018-03-01

Located in the Imiter Inlier (Eastern Saghro, Anti-Atlas, Morocco), Ediacaran volcanic dykes have been studied for their petrofabric using Anisotropy of Magnetic Susceptibility (AMS) technique. Four dykes, namely TF, TD, FF and FE show andesitic compositions and are considered to belong to the same dyke swarm. They are oriented respectively N25E, N40E, N50E, and N10E and have been emplaced during a first tectonic event. The dyke FW, oriented N90E displays a composition of alkali basalt and its emplacement is attributed to a subsequent tectonic event. These rocks are propylitized under greenschist facies conditions forming a secondary paragenesis constituted by calcite, chlorite, epidote and sericite. The dykes TF, TD, FF and FE are sub-volcanic calc-alkaline, typical of post-collisional basalts/andesites, belonging to plate margin andesites. The FW dyke shows a within-plate basalt signature; alkaline affinity reflecting a different petrogenetic process. The thermomagnetic analyses show a dominantly ferromagnetic behaviour in the TF dyke core carried by single domain Ti-poor magnetite, maghemite and pyrrhotite. The dominantly paramagnetic susceptibilities in TF dyke rims and TD, FE, FF and FW dykes are controlled by ilmenite, amphibole, pyroxene and chlorite. The magnetic fabrics of the Imider dykes, determined by our AMS study, allows us to reconstitute the tectonic conditions which prevailed during the emplacement of these two generations of volcanic dykes. The first tectonic event was characterized by a roughly NE-SW compression and the second tectonic event is characterized by an E-W shortening followed by a relaxation recording the end of the Pan-African orogeny in the eastern Anti-Atlas.

Magmatic dyking and recharge in the Asal Rift, Republic of Djibouti

NASA Astrophysics Data System (ADS)

Peltzer, G.; Harrington, J.; Doubre, C.; Tomic, J.

2012-12-01

The Asal Rift, Republic of Djibouti, has been the locus of a major magmatic event in 1978 and seems to have maintained a sustained activity in the three decade following the event. We compare the dyking event of 1978 with the magmatic activity occurring in the rift during the 1997-2008 time period. We use historical air photos and satellite images to quantify the horizontal opening on the major faults activated in 1978. These observations are combined with ground based geodetic data acquired between 1973 and 1979 across the rift to constrain a kinematic model of the 1978 rifting event, including bordering faults and mid-crustal dykes under the Asal Rift and the Ghoubbet Gulf. The model indicates that extension was concentrated between the surface and a depth of 3 km in the crust, resulting in the opening of faults, dykes and fissures between the two main faults, E and gamma, and that the structure located under the Asal Rift, below 3 km, deflated. These results suggest that, during the 1978 event, magmatic fluids transferred from a mid-crustal reservoir to the shallow structures, injecting dykes and filling faults and fissures, and reaching the surface in the Ardoukoba fissural eruption. Surface deformation observed by InSAR during the 1997-2008 decade reveals a slow, yet sustained inflation and extension across the Asal Rift combined with continuous subsidence of the rift inner floor. Modeling shows that these observations cannot be explained by visco-elastic relaxation, a process, which mostly vanishes 20 to 30 years after the 1978 event. However, the InSAR observations over this decade are well explained by a kinematic model in which an inflating body is present at mid-crustal depth, approximately under the Fieale caldera, and shallow faults accommodate both horizontal opening and down-dip slip. The total geometric moment rate, or inflation rate, due to the opening of the mid-crustal structure and the deeper parts of the opening faults is 3 106 m3yr. Such a

Radial patterns of bitumen dykes around Quaternary volcanoes, provinces of northern Neuquén and southernmost Mendoza, Argentina

NASA Astrophysics Data System (ADS)

Cobbold, Peter R.; Ruffet, Gilles; Leith, Leslie; Loseth, Helge; Rodrigues, Nuno; Leanza, Hector A.; Zanella, Alain

2014-12-01

Where the Neuquén Basin of Argentina abuts the Andes, hundreds of veins of solid hydrocarbon (bitumen) are visible at the surface. Many of these veins became mines, especially in the last century. By consensus, the bitumen has resulted from maturation of organic-rich shales, especially the Vaca Muerta Fm of Late Jurassic age, but also the Agrio Fm of Early Cretaceous age. To account for their maturation, recent authors have invoked regional subsidence, whereas early geologists invoked magmatic activity. During 12 field seasons (since 1998), we have tracked down the bitumen localities, mapped the veins and host rocks, sampled them, studied their compositions, and dated some of them. In the provinces of northern Neuquén and southernmost Mendoza, the bitumen veins are mostly sub-vertical dykes. They tend to be straight and continuous, crosscutting regional structures and strata of all ages, from Jurassic to Palaeocene. Most of the localities lie within 70 km of Tromen volcano, although four are along the Rio Colorado fault zone and another two are at the base of Auca Mahuida volcano. On both volcanic edifices, lavas are of late Pliocene to Pleistocene age. Although regionally many of the bitumen dykes tend to track the current direction of maximum horizontal tectonic stress (ENE), others do not. However, most of the dykes radiate outward from the volcanoes, especially Tromen. Thicknesses of dykes tend to be greatest close to Tromen and where the host rocks are the most resistant to fracturing. Many of the dykes occur in the exhumed hanging walls of deep thrusts, especially at the foot of Tromen. Here the bitumen is in places of high grade (impsonite), whereas further out it tends to be of medium grade (grahamite). A few bitumen dykes contain fragments of Vaca Muerta shale, so that we infer forceful expulsion of source rock. At Curacó Mine, some shale fragments contain bedding-parallel veins of fibrous calcite (beef) and these contain some bitumen, which is

Pesticides in soil and sediment of a dyke-protected area of the Red River Delta, Vietnam

NASA Astrophysics Data System (ADS)

Braun, Gianna; Bläsing, Melanie; Kruse, Jens; Amelung, Wulf; Renaud, Fabrice; Sebesvari, Zita

2017-04-01

Coastal regions are densely populated but at the same time represent important agricultural areas for food production of the growing world population. To sustain high agricultural yields, in monocultures such as permanent rice systems, pesticides are used in high quantity and frequency. While earlier studies monitored the fate of pesticides in paddy rice systems, the overall fate of these compounds is altered nowadays due to the construction of dykes, which are needed in many delta regions to protect them from high tides, storm surges and salt water intrusion such as in the Red River Delta. The dyke system regulates the discharge and water exchange inside the diked area including irrigation channels for the paddy rice production. Local authorities observed increasing pollution towards the sea (highest pollution close to the dykes) and hypothesized that the dyke system would prevent water exchange and thus lead to an accumulation of pollutants within the diked area. Hence, the purpose of this study was to investigate the effect of dykes on pesticide pollution patterns in coastal delta regions of the Red River Delta. The study was conducted in the district Giao Thuy of the Red River Delta, Vietnam. This area is surrounded by a sea and river dyke; both have several inlet and outlet gates to control the water level in the irrigation channels. We determined the pesticide pollution pattern in a diked agricultural area, as well as along salinity gradients in and outside the diked areas. Samples were taken from rice fields and sediments from irrigation channels inside the diked area as well from saline aquaculture fields located outside the dyke. Pesticide analysis was conducted by accelerated solvent extraction (ASE), followed up by the clean-up process described by Laabs et al. (2007) and analyses using gas chromatography coupled with a mass selective detector (MSD). Preliminary results suggest that out of the 26 analysed compounds chlorpyrifos, propiconazole and

Earthshots: Satellite images of environmental change – Hubbard Glacier, Alaska, USA

USGS Publications Warehouse

Adamson, Thomas

2015-01-01

These Landsat images illustrate an unusual event that was observed twice at the terminus of Hubbard Glacier. Hubbard temporarily blocked Russell Fjord (a long, narrow inlet of the sea) from the rest of Disenchantment Bay and the Gulf of Alaska. It’s even possible that the glacier could one day permanently block the fjord.

Microstructural indicators of convection in sills and dykes

NASA Astrophysics Data System (ADS)

Holness, Marian; Neufeld, Jerome; Gilbert, Andrew

2016-04-01

. In mafic sills, the average apparent aspect ratio (AR), as measured in thin-section, varies smoothly with model crystallization times (calculated assuming diffusive heat loss), consistent with in situ growth in solidification fronts. However, AR is invariant across individual mafic dykes, with decreasing values (i.e. more blocky grains) as the dyke width increases. This difference can be accounted for by the plagioclase in dykes growing as individual grains and clusters suspended in a convecting magma. Cooling at a vertical wall, as is the case for dykes, will always result in a gravitational convective instability, and therefore crystal-poor magma in dykes will always convect. As solidification proceeds, the increasing volume fraction of suspended crystals will eventually damp convection: the final stages of solidification occur in static crystal-rich magma, containing a well-mixed grain population. That the Shiant Isles Main Sill exhibits evidence for prolonged convection of sufficient vigour to suspend 5 mm olivine clusters, while other sills of comparable thickness contain plagioclase with grain shapes indicative of growth predominantly in solidification fronts, is most likely due to the composite nature of the Shiant. The 140m unit is underlain by 23m of picrite which intruded shortly before - this heat source would have acted as a strong driver for convection.

Paleomagnetic Results of the 925 Ma Mafic Dykes From the North China Craton: Implications for the Neoproterozoic Paleogeography of Rodinia

NASA Astrophysics Data System (ADS)

Zhao, X.; Peng, P.

2017-12-01

Precambrian mafic dyke swarms are useful geologic records for Neoproterozoic paleogeographic reconstruction. We present a paleomagnetic study of the 925 Ma Dashigou dyke swarm from 3 widely separated locations in the central and northern parts of the North China Craton, which are previously unsampled regions. Stepwise thermal and alternating field demagnetizations were successful in isolating two magnetic components. The lower unblocking temperature component represents the recent Earth magnetic field. The higher unblocking temperature component is the characteristic remanent magnetization and yields positive baked contact test. Results from detailed rock magnetic measurements corroborate the demagnetization behavior and show that titanomagnetites are the main magnetic carrier in these rocks. There was no regional event that has reset the remanent magnetization of all the dyke sites, as indicated by the magnetization directions of both overlying and underlying strata. The similarity of the virtual paleomagnetic poles for the 3 sampled regions also argues that the characteristic remanent magnetizations are primary magnetization when the dykes were emplaced. The paleomagnetic poles from the Dashigou dyke swarm of the North China Craton are not similar to those of the identical aged Bahia dykes from the São Francisco Craton, Brazil, indicating that these mafic dykes may be not parts of a common regional magmatic event that affected North China Craton and NE Brazil at about 925 Ma.

Petrogenesis and tectonic association of rift-related basic Panjal dykes from the northern Indian plate, North-Western Pakistan: evidence of high-Ti basalts analogous to dykes from Tibet

NASA Astrophysics Data System (ADS)

Sajid, Muhammad; Andersen, Jens; Arif, Mohammad

2017-10-01

Rift related magmatism during Permian time in the northern margin of Indian plate is represented by basic dykes in several Himalayan terranes including north western Pakistan. The field relations, mineralogy and whole rock geochemistry of these basic dykes reveal significant textural, mineralogical and chemical variation between two major types (a) dolerite and (b) amphibolite. Intra-plate tectonic settings for both rock types have been interpreted on the basis of low Zr/Nb ratios (< 10), K/Ba ratios (20-40) and Hf-Ta-Th and FeO-MgO-Al2O3 discrimination diagrams. The compositional zoning in plagioclase and clinopyroxene, variation in olivine compositions and major elements oxide trends indicate a vital role of fractional crystallization in the evolution of dolerites, which also show depletion in rare earth elements (REEs) and other incompatible elements compared to the amphibolites. The equilibrium partial melting models from primitive mantle using Dy/Yb, La/Yb, Sm/Yb and La/Sm ratios show that amphibolite formed by smaller degrees (< 5%) of partial melting than the dolerites (< 10%). The trace elements ratios suggest the origination of dolerites from the subcontinental lithospheric mantle with some crustal contamination. This is consistent with a petrogenetic relationship with Panjal trap magmatism, reported from Kashmir and other parts of north western India. The amphibolites, in contrast, show affinity towards Ocean Island basalts (OIB) with a relatively deep asthenospheric mantle source and minimal crustal contribution and are geochemically similar to the High-Ti mafic dykes of southern Qiangtang, Tibet. These similarities combined with Permian tectonic restoration of Gondwana indicate the coeval origin for both dykes from distinct mantle source during continental rifting related to formation of the Neotethys Ocean.

Petrogenesis and tectonic association of rift-related basic Panjal dykes from the northern Indian plate, North-Western Pakistan: evidence of high-Ti basalts analogous to dykes from Tibet

NASA Astrophysics Data System (ADS)

Sajid, Muhammad; Andersen, Jens; Arif, Mohammad

2018-06-01

Rift related magmatism during Permian time in the northern margin of Indian plate is represented by basic dykes in several Himalayan terranes including north western Pakistan. The field relations, mineralogy and whole rock geochemistry of these basic dykes reveal significant textural, mineralogical and chemical variation between two major types (a) dolerite and (b) amphibolite. Intra-plate tectonic settings for both rock types have been interpreted on the basis of low Zr/Nb ratios (< 10), K/Ba ratios (20-40) and Hf-Ta-Th and FeO-MgO-Al2O3 discrimination diagrams. The compositional zoning in plagioclase and clinopyroxene, variation in olivine compositions and major elements oxide trends indicate a vital role of fractional crystallization in the evolution of dolerites, which also show depletion in rare earth elements (REEs) and other incompatible elements compared to the amphibolites. The equilibrium partial melting models from primitive mantle using Dy/Yb, La/Yb, Sm/Yb and La/Sm ratios show that amphibolite formed by smaller degrees (< 5%) of partial melting than the dolerites (< 10%). The trace elements ratios suggest the origination of dolerites from the subcontinental lithospheric mantle with some crustal contamination. This is consistent with a petrogenetic relationship with Panjal trap magmatism, reported from Kashmir and other parts of north western India. The amphibolites, in contrast, show affinity towards Ocean Island basalts (OIB) with a relatively deep asthenospheric mantle source and minimal crustal contribution and are geochemically similar to the High-Ti mafic dykes of southern Qiangtang, Tibet. These similarities combined with Permian tectonic restoration of Gondwana indicate the coeval origin for both dykes from distinct mantle source during continental rifting related to formation of the Neotethys Ocean.

Origin of strong dispersion in Hubbard insulators

DOE PAGES

Wang, Y.; Wohlfeld, K.; Moritz, B.; ...

2015-08-10

Using cluster perturbation theory, we explain the origin of the strongly dispersive feature found at high binding energy in the spectral function of the Hubbard model. By comparing the Hubbard and $t₋J₋3s$ model spectra, we show that this dispersion does not originate from either coupling to spin fluctuations ($∝ J$ ) or the free hopping ($∝ t$ ). Instead, it should be attributed to a long-range, correlated hopping $∝ t²/U$ which allows an effectively free motion of the hole within the same antiferromagnetic sublattice. This origin explains both the formation of the high-energy anomaly in the single-particle spectrum and themore » sensitivity of the high-binding-energy dispersion to the next-nearest-neighbor hopping $t'$ .« less

Geodynamic Setting of Proterozoic Dyke Swarms of the Leo-Man Craton, West Africa, Based on New U-Pb Dating and Geochemistry

NASA Astrophysics Data System (ADS)

Baratoux, L.; Jessell, M.; Söderlund, U.; Ernst, R. E.; Benoit, M.; Naba, S.; Cournede, C.; Perrouty, S.; Metelka, V.; Yatte, D.; Diallo, D. P.; Ndiaye, P. M.; Dioh, E.; Baratoux, D.

2016-12-01

Over 20 sets of dolerite dykes crosscutting Paleoproterozoic basement in West Africa were distinguished via the interpretation of regional and high-resolution airborne magnetic data available over the West African Craton. Some of the dykes reach over 300 km in length and are considered parts of much larger systems of mafic dyke swarms which form the plumbing system of Large Igneous Provinces (LIPs). Five different dyke swarms in Burkina Faso, Niger, Ghana and Senegal were investigated. In terms of petrography and composition, the mafic dykes correspond to tholeiitic basalts and are typically composed of plagioclase + clinopyroxene ± orthopyroxene ± olivine. They display a doleritic texture of variable grain size. Eleven ID-TIMS U-Pb ages obtained on baddeleyite define five generations of Proterozoic age. The N10 Libiri dyke swarm, found in western Niger, yielded an age of ca. 1790 Ma. The N40 Bassari swarm in Senegal was dated at ca. 1764 Ma, and is potentially linked to the 1790 Ma Libiri swarm, 1400 km away. The 300 by 400 km Korsimoro N100 dyke swarm transects central Burkina Faso and was dated at ca. 1575 Ma. Five ca. 1520 Ma ages were obtained for dykes of the Essakane swarm, three in Burkina Faso, one from Ghana (N130 orientation) and one from Senegal (E-W orientation), and document a large extent (600 km wide and 1500 km long) and short duration of dyke emplacement. The Manso N350 dyke swarm in southern Ghana, which is about 400 km long and about 200 km wide, yields a preliminary age of ca 870 Ma. A mantle plume origin is suggested for these swarms, especially the 1790-1765 Ma Libiri-Bassari swarm and the 1520 Ma Essakane swarms (which have lithosphere-contaminated E-MORB chemistry), whose scale is similar to largest giant radiating swarms (e.g. CAMP and Mackenzie). The 870 Ma Manso swarm has composition closer to OIB, consistent with a plume/hotspot origin. The 1575 Ma Korsimoro swarm has composition between EMORB and NMORB, which suggests a rift setting.

Paleomagnetism and geochronological studies on a 450 km long 2216 Ma dyke from the Dharwar craton, southern India

NASA Astrophysics Data System (ADS)

Nagaraju, E.; Parashuramulu, V.; Kumar, Anil; Srinivas Sarma, D.

2018-01-01

Paleomagnetic and geochronological studies were carried out on a ∼ 450 km long (from 17 sites) N-S striking Paleoproterozoic dyke swarm exposed along a natural crustal cross section of about 10 km (increasing from North to South) in the Dharwar Craton, to study the characteristics of paleomagnetism and geochronology in vertical dimension. U-Pb/Pb-Pb dating on baddeleyite gives a crystallisation age of 2216.0 ± 0.9 Ma for long dyke AKLD. Paleomagnetic data from this well dated ∼ 2216 Ma dyke swarm in Dharwar Craton are of excellent quality. High coercivity and high blocking temperature components are carried by single domain magnetite and show dual polarity remanence directions. Combined normal and reverse polarity remanences on AKLD and other N-S dykes define the most reliable paleomagnetic pole for ∼ 2216 Ma at latitude 36°S and longitude 312°E (A95 = 7°). Though paleomagnetic data is unavailable on other N-S dykes below the Cuddapah basin, high precision geochronology suggest that they are of similar age within errors. Though there is a variation in the crustal depth of Dharwar craton from north to south, consistent Pb-Pb/U-Pb baddeleyite geochronology and paleomagnetic studies along the AKLD established its continuity and preservation along its entire strike length. The virtual geomagnetic poles of these sites confirm a stable remanence and are almost identical to the previously reported paleomagnetic pole and also supported by positive reversal test. Positive paleomagnetic reversal test on these dykes signify that the remanent magnetization is primary and formed during initial cooling of the intrusions. Updated apparent polar wander path of Dharwar craton indicates relatively low drift rate during 2.21-2.08 Ga interval. Magnetogranulometry and SEM studies show that remanent magnetization in this dyke was carried by single domain magnetite residing within silicate minerals.

Superconductivity in the two-dimensional Hubbard model

NASA Astrophysics Data System (ADS)

Beenen, J.; Edwards, D. M.

1995-11-01

Quasiparticle bands of the two-dimensional Hubbard model are calculated using the Roth two-pole approximation to the one-particle Green's function. Excellent agreement is obtained with recent Monte Carlo calculations, including an anomalous volume of the Fermi surface near half-filling, which can possibly be explained in terms of a breakdown of Fermi liquid theory. The calculated bands are very flat around the (π,0) points of the Brillouin zone in agreement with photoemission measurements of cuprate superconductors. With doping there is a shift in spectral weight from the upper band to the lower band. The Roth method is extended to deal with superconductivity within a four-pole approximation allowing electron-hole mixing. It is shown that triplet p-wave pairing never occurs. A self-consistent solution with singlet dx2-y2-wave pairing is found and optimal doping occurs when the van Hove singularity, corresponding to the flat band part, lies at the Fermi level. Nearest-neighbor antiferromagnetic correlations play an important role in flattening the bands near the Fermi level and in favoring superconductivity. However, the mechanism for superconductivity is a local one, in contrast to spin-fluctuation exchange models. For reasonable values of the hopping parameter the transition temperature Tc is in the range 10-100 K. The optimum doping δc lies between 0.14 and 0.25, depending on the ratio U/t. The gap equation has a BCS-like form and 2Δmax/kTc~=4.

Some applications of the Kronecker product in Hubbard representation

NASA Astrophysics Data System (ADS)

Enríquez, Marco; Rosas-Ortiz, Oscar

2014-10-01

The properties of the Kronecker product are revisited in terms of Hubbard operators. The simplest representation of a Hubbard operator Xi,jn is a square matrix of size n with an entry equal to 1 and zero elsewhere. This framework simplifies the calculation of the Kronecker product of arbitrary matrices no matter the size or the number of the involved factors. Some applications are presented, these include the algebra of permutation matrices, the Hadamard matrix, the XXX Heisenberg model and the interaction of an atom with radiation fields.

Volcanic outcrops of southeast Ethiopia and the Ogaden Dyke Swarm

NASA Astrophysics Data System (ADS)

Mège, Daniel; Purcell, Peter; Jourdan, Fred; Pochat, Stéphane

2013-04-01

A new map of Tertiary volcanics occurrences in the Ogaden region of southeast Ethiopia and adjacent areas of Somalia has been prepared. Outcrop areas, mapped using satellite images and helicopter-­-supported field work in 2008, are more widespread than previously recognized, while magnetic and drill data reveal the vast subsurface extent of the magmatism. Several spectacular 'meandering' outcrops, over 100 km long, are undoubtedly exhumed canyon-­-filling flows and magnetic data show that many other apparently isolated outcrops are actually part of similar flows, the bulk of which are now subsurface. Age dating and well intersections show several volcanic episodes, with the major outpouring occurring across a broad peneplain in the Oligocene. Geological and aeromagnetic mapping, and 40Ar/39Ar age dating, reveal a dyke swarm extending SSE from the southern Afar margin more than 600 km across the Somali Plate, and coeval with dyke injection in the Red Sea rift at ~25 Ma. The Ogaden Dyke Swarm, which occurs in an area historically considered remote from the impact of the Afro-­-Arabian rifting and volcanism, appears associated with the Marda Fault and marks a zone of crustal dilation along the Red Sea trend across the Horn of Africa. Contemporaneous rifts, also trending WNW/ESE and over 120 km long, occur in NE Somalia, confirming the predominantly NE/SW-­-directed crustal stress regime in the Ogaden and adjacent region at this time.

An Integrated Geochronological, Petrological, Geochemical and Paleomagnetic Study of Paleoproterozoic and Mesoproterozoic Mafic Dyke Swarms in the Nain Craton, Labrador

NASA Astrophysics Data System (ADS)

Sahin, Tugce

The Nain craton comprises the western, Labrador segment of the larger North Atlantic craton (NAC) which exposes Early through Late Archean gneisses. The NAC is bounded on all sides by Paleoproterozoic collisional orogens that involved either considerable structural reworking (Torngat-Nagssugtoqidian-Lewisian) or the accretion of juvenile arc magmas (Ketilidian-Makkovik). The NAC remains poorly understood compared to other Archean crustal blocks now dispersed globally. Compounding this problem is a lack of reliable paleomagnetic poles for NAC units that predate its assembly into the supercontinent Laurentia by ca. 1800 Ma, which could be used to test neighboring relationships with other cratonic fragments. In order to understand the history of the NAC as part of a possible, larger supercontinent, the record of mafic dyke swarms affecting the craton, particularly those that postdate the Late Archean terrane assembly, were examined in this study. Diabase or gabbroic dyke swarms are invaluable in such studies because their geometries offer possible locus points, they often have a punctuated emplacement and precisely datable crystallization histories, and they have cooling histories and oxide mineralogy amenable to recovering robust paleopoles. Coastal Labrador exposes a number of mafic dykes, some of which are demonstrably Paleoproterozoic (e.g. 2235 Ma Kikkertavak dykes; 2121 Ma Tikkigatsiagak dykes) or Mesoproterozoic (e.g. 1280-1270 Ma Nain and Harp dykes) in age (U-Pb; baddeleyite or zircon). The southern half of the Nain craton (Hopedale block) in particular preserves a rich array of mafic dykes. Dyke cross-cutting relationships are numerous and relatively well exposed, permitting multiple opportunities for paleomagnetic field tests (e.g. baked contact). The results presented here allow understanding of the tectonic evolution of the NAC with implications for strengthened Labrador-Greenland correlations, and testing possible Paleoproterozoic supercontinent

Syn-convergence extension in the southern Lhasa terrane: Evidence from late Cretaceous adakitic granodiorite and coeval gabbroic-dioritic dykes

NASA Astrophysics Data System (ADS)

Ma, Xuxuan; Xu, Zhiqin; Meert, Joseph G.

2017-10-01

Late Cretaceous (∼100-80 Ma) magmatism in the Gangdese magmatic belt plays a pivotal role in understanding the evolutionary history and tectonic regime of the southern Lhasa terrane. The geodynamic process for the formation of the early Late Cretaceous magmatism has long been an issue of hot debates. Here, petrology, geochronology and geochemistry of early Late Cretaceous granodiorite and coeval gabbroic-dioritic dykes in the Caina region, southern Lhasa, were investigated in an effort to ascertain their petrogenesis, age of intrusion, magma mixing and tectonic setting. Zircon U-Pb dating of granodiorite yields 206Pb/238U ages of 85.8 ± 1.7 and 86.4 ± 1.1 Ma, whilst that of the E-W trending dykes yields ages of 82.7 ± 2.6 and 83.5 ± 3.5 Ma. Within error, the crystallization ages of the dykes and the granodiorite are indistinguishable. Field observations and mineralogical microstructures are suggestive of a magma mixing process during the formation of the dykes and the granodiorite. The granodiorite exhibits geochemical features that are in agreement with those of subduction-related high-SiO2 adakites. The granodiorite and dykes have relatively constant εNd(t) values of +2.2 to +4.9 and initial 87Sr/86Sr ratios (0.7045-0.7047). These similar characteristics are herein interpreted as an evolutionary series from the dykes to granodiorite, consistent with magma mixing process. Ti-in-zircon thermometer and Al-in-hornblende barometer indicate that the granodiorite and the dioritic dyke crystallized at temperatures of ca. 750 and 800 °C, depths of ca. 6-10 and 5-9 km, respectively. Taking into account the synchronous magmatic rocks in the Gangdese Belt and the coeval rifted basin within the Lhasa terrane, the granodiorite and dykes reveal an early Late Cretaceous syn-convergence extensional regime in the southern Lhasa terrane, triggered by slab rollback of the Neotethyan oceanic lithosphere.

Lamprophyres from the Harohalli dyke swarm in the Halaguru and Mysore areas, Southern India: Implications for backarc basin magmatism

NASA Astrophysics Data System (ADS)

Lanjewar, Shubhangi; Randive, Kirtikumar

2018-05-01

The Bangalore and Harohalli dyke swarms occur in the eastern part of the Dharwar craton. The older Bangalore dyke swarm is made up of dolerites, trending east-west, and the younger contains alkaline dykes that trend approximately north-south. The lamprophyres of the Harohalli dyke swarm occur in the Halaguru and Mysore industrial areas where they are exposed as fresh porphyritic - panidiomorphic dykes, containing crustal xenoliths, and showing chilled contacts with the country rock charnokites. They are chiefly composed of amphiboles which form well-developed phenocrysts. Clinopyroxenes are present in some of the dykes. Compositional zoning is observed in clinopyroxenes and amphiboles; their zoning patterns indicate that the magma experienced cryptic variations and that fractional crystallization was a dominant process in the evolution of the Harohalli Lamprophyres (HRL). The HRL are calc-alkaline with shoshonitic affinity and exhibit a K2O/Na2O ratio of ∼1. They show primitive (MORB-like) trace-element characters. LILE and LREE both show marginally enriched patterns; whereas HFSE and HREE show strongly depleted patterns. In the regional geologic sense, HRL dykes are characterised by two major influences; namely, (i) primary source region characteristics, which are geochemically more primitive, roughly falling within fields of primitive - MORB and enriched- MORB and (ii) the continental lithosphere. The data points for the HRL distinctly show their proximity to N-MORB and scatter towards the continental crust. Moreover, features like xenolith assimilation might influence the trace-element characteristics of the HRL dykes. Such magmas with mixed characters can be formed in a backarc basin environment. Geochemical proxies such as Ba/Nb vs Nb/Yb, Ba/Th vs Th/Nb, and the water content of magmas; which have been effectively used for discriminating backarc basin magmas worldwide, also indicate that the HRL magmas were generated in a backarc environment with inputs from

Paleomagnetism of the Grenville diabase dyke swarm and implications for the mid Vendian paleolatitude of Laurentia

NASA Astrophysics Data System (ADS)

Buchan, K. L.; Ernst, R. E.; Kumarapeli, P. S.

2004-05-01

The Vendian-early Cambrian drift of Laurentia is important for theories of `Snowball Earth' and the continental breakup that formed the Iapetus Ocean. However, estimates of Laurentia's paleolatitude in this period differ widely. Some authors have proposed that Laurentia remained in low latitude throughout this period, whereas others have supported rapid drift of the continent from low to high and back to low latitude. To assist in evaluating these models, a paleomagnetic study was conducted on the mid Vendian Grenville dyke swarm of southeastern Laurentia. This 700 km long swarm was emplaced along the Ottawa graben, an aulacogen associated with rifting that preceded the opening of the Iapetus Ocean. The swarm was the subject of an early paleomagnetic study by Murthy (1971). More recently, U-Pb baddeleyite and zircon ages of ca. 590 Ma have been described for three Grenville dykes (Kamo et al. 1995). At one of these sites, on the `Mattawa' dyke, a positive paleomagnetic baked contact test was also reported (Hyodo and Dunlop 1993). In that detailed test thermoremanent overprinting in the zone of hybrid magnetization was shown to match that expected from heat conduction for a cooling dyke. Nevertheless, Hyodo and Dunlop suggested that the steep down remanence in the dyke, although primary, was likely acquired during a geomagnetic excursion because it did not appear to fit the then-available polar wander path. In our study, paleomagnetic sampling was carried out at 36 sites, including all three dated locations. A detailed analysis has been completed for the dated sites and preliminary analysis for the remaining sites. A stable steep down remanence was obtained for all samples in the Mattawa dyke, and in most samples from a second dated site. The third dated site is less stably magnetized and has not yielded a usable remanence direction. Ten additional sites yield stable steep down or occasionally steep up remanences. The presence of a steep remanence in two dated dykes

Mott metal-insulator transition in the doped Hubbard-Holstein model

NASA Astrophysics Data System (ADS)

Kurdestany, Jamshid Moradi; Satpathy, S.

2017-08-01

Motivated by the current interest in the understanding of the Mott insulators away from half-filling, observed in many perovskite oxides, we study the Mott metal-insulator transition in the doped Hubbard-Holstein model using the Hartree-Fock mean field theory. The Hubbard-Holstein model is the simplest model containing both the Coulomb and the electron-lattice interactions, which are important ingredients in the physics of the perovskite oxides. In contrast to the half-filled Hubbard model, which always results in a single phase (either metallic or insulating), our results show that away from half-filling, a mixed phase of metallic and insulating regions occurs. As the dopant concentration is increased, the metallic part progressively grows in volume, until it exceeds the percolation threshold, leading to percolative conduction. This happens above a critical dopant concentration δc, which, depending on the strength of the electron-lattice interaction, can be a significant fraction of unity. This means that the material could be insulating even for a substantial amount of doping, in contrast to the expectation that doped holes would destroy the insulating behavior of the half-filled Hubbard model. While effects of fluctuation beyond the mean field remain an open question, our results provide a starting point for the understanding of the density-driven metal-insulator transition observed in many complex oxides.

Rethinking monogamy's nature: From the truth of non/monogamy to a dyke ethics of "antimonogamy".

PubMed

Willey, Angela

2018-04-03

Following Lynne Huffer's work on queer feminism, this abridged essay centers the figure of the lesbian in order to develop a dyke ethics that engenders nuanced thinking about both monogamy and embodiment. The essay reads Alison Bechdel's comic strip, Dykes to Watch Out For, to elaborate a "dyke ethics of anti-monogamy." Grounded in notions of friendship, community, and social justice, this ethics decenters the sexual dyad in a way that polyamory does not. It also insists upon a theoretical and ethical disposition of respect for the simultaneously political and embodied nature of desire. In so doing, it offers first a way of re-thinking the story of monogamy's nature as a naturecultural tale about mononormative desire and further places that desire in a field of relationality that renders its significance as a feature of humanness and an object of scientific inquiry strange.

Magnetic Fluctuations in the Hubbard Model on Kagome-based Frustrated Lattices

NASA Astrophysics Data System (ADS)

Udagawa, Masafumi; Motome, Yukitoshi

2008-03-01

We report our results on the interplay between electron correlation and magnetic fluctuations in the geometrically-frustrated Kagome and hyper-Kagome Hubbard models at half filling. These models have two different geometrical units important in the low-energy physics: the frustrated triangle and the non-frustrated loop with even-number sites. In order to treat both of them on equal footing, we apply cluster dynamical mean-field theory to large-size clusters up to 12 sites. By calculating the spin susceptibility χ(q, φ), we have found in the Kagome system that an anomalous one-dimensional magnetic correlation previously found near the Mott transition [1] is observed even in the non-interacting case at high temperature, and its temperature range gradually suppressed by increasing electron correlation. This behavior is ascribed to the nesting property at the van-Hove singularity preserved under electron correlation. We will also present the results for hyper-Kagome system in relation to the recent experiments on Na4Ir3O8 [2]. [1] T. Ohashi et al., Phys. Rev. Lett. 97, 066401 (2006)[2] Y. Okamoto et al., Phys. Rev. Lett. 99, 137207 (2007)

Fidelity study of superconductivity in extended Hubbard models

NASA Astrophysics Data System (ADS)

Plonka, N.; Jia, C. J.; Wang, Y.; Moritz, B.; Devereaux, T. P.

2015-07-01

The Hubbard model with local on-site repulsion is generally thought to possess a superconducting ground state for appropriate parameters, but the effects of more realistic long-range Coulomb interactions have not been studied extensively. We study the influence of these interactions on superconductivity by including nearest- and next-nearest-neighbor extended Hubbard interactions in addition to the usual on-site terms. Utilizing numerical exact diagonalization, we analyze the signatures of superconductivity in the ground states through the fidelity metric of quantum information theory. We find that nearest and next-nearest neighbor interactions have thresholds above which they destabilize superconductivity regardless of whether they are attractive or repulsive, seemingly due to competing charge fluctuations.

Dyke emplacement in a Quaternary active volcano: the exposed swarm of Monte Somma-Vesuvio (Naples, Italy)

NASA Astrophysics Data System (ADS)

Marinoni, L. B.

2003-04-01

The Monte Somma-Vesuvius is a famous active stratovolcano located on the Bay of Naples (Italy). Unexpectedly, the intrusive complex of this volcano is poorly known. This work focuses on the moderate-intensity dyke swarm that crops out along the caldera wall cut in the Monte Somma (MS) and its host rock. A detailed field survey of 101 individual intrusions consisted of the recording of about 20 parameters for each intrusion according to a standardised method. The intrusions were located in the framework of a new geological map drawn for the caldera wall at a scale 1:2000. The MS intrusions that crop out from 780 to 1055 m a.s.l., are mostly monogenetic steeply-dipping segmented dykes; inclined sheets are also present, generally dipping towards the outer periphery of the volcano. Apparent crosscut due to dyke segmentation is common; true intersections show ambiguous alternation of dyke strikes. Indicators of initial intrusive flow (opening stage of the dyke-hosting fracture) often differ in direction and sense from late-stage indicators. Frequently, dykes intruded sub-horizontally in an early stage and later sub-vertically. The peak extension for MS, computed according to a standardised method, is 81.7 m in the direction N90°, based on 96 exposed sheets. Very likely, most of MS sheets intruded within ~12 ka, giving a time-averaged minimum extension rate of ~7 mm a-1. On MS, the azimuth pattern and the azimuth of peak extension are different in the two portions in which the caldera wall can be divided, east and west of Canale dell'Arena. This difference may indicate that two fault systems affecting the basement underneath the volcano exert their influence on the feeding system. On the other hand, three main dyke sets (among which the set trending NE-SW is prevalent) exist on MS, and inclined sheets form a significant portion of the intrusions. In addition, the peak extension and the percentage extension are comparable quantitatively in the two different sections of

Structural, Geochemical, and Isotopic Studies on Magmatic Dyke Swarms of the South Shetland Islands Volcanic Arc, West Antarctica - Revealing the Geodynamic History

NASA Astrophysics Data System (ADS)

Kraus, S.; Miller, H.

2003-12-01

Between 2000 and 2002 areas of up to 100,000 m2 have been mapped at several locations of the South Shetland Islands, mainly on King George and Livingston Islands. A structural analysis of the dykes and the host rocks was undertaken, and about 250 dykes were sampled for geochemical studies. On Livingston Island six different strike directions were identified, yielding a reliable relative time sequence as deduced from field-relationships. Geochemically, these dykes can be separated into five different groups, correlating with the different strike directions, one of those groups comprising two directions. Analysis of the structural data shows, that at least on Livingston Island only minor changes of the tensional situation occurred. Geochemical data reveal that all dykes of the South Shetland Islands belong to a calc-alkaline, arc-related suite, ranging from primitive basalts to highly differentiated rhyolites. Interpretation of Sr isotopic data of the dykes proves difficult, as there are indications for sea-water induced Sr-alteration. Nd isotopic analysis yield better results, revealing a three-stage development from the oldest dykes (ɛ Nd -0.2 to 0.6) on Livingston Island towards a second, younger group (ɛ Nd 2.8 to 4.2, also Livingston), terminating with a third one (ɛ Nd 5.2 to 7.6), which includes the youngest dykes on Livingston and all dykes on King George and also Penguin Island. Either two mantle sources were involved, or the amount of crustal contamination changed considerately with time. It may have been high during initial arc volcanism, because of a still unstretched crust, then decreasing continually with progressing volcanism. In any case, the pattern reflects a chronological sequence corresponding with other authors' hypothesis of a migrating arc volcanism from SW to NE, i.e. from Livingston (older dykes) towards King George Island (younger dykes). Pb isotopic data, plottet together with MORB- and sediment-samples dredged from the Drake Passage

Fidelity study of superconductivity in extended Hubbard models

DOE PAGES

Plonka, N.; Jia, C. J.; Wang, Y.; ...

2015-07-08

The Hubbard model with local on-site repulsion is generally thought to possess a superconducting ground state for appropriate parameters, but the effects of more realistic long-range Coulomb interactions have not been studied extensively. We study the influence of these interactions on superconductivity by including nearest- and next-nearest-neighbor extended Hubbard interactions in addition to the usual on-site terms. Utilizing numerical exact diagonalization, we analyze the signatures of superconductivity in the ground states through the fidelity metric of quantum information theory. Finally, we find that nearest and next-nearest neighbor interactions have thresholds above which they destabilize superconductivity regardless of whether they aremore » attractive or repulsive, seemingly due to competing charge fluctuations.« less

Doping dependence of ordered phases and emergent quasiparticles in the doped Hubbard-Holstein model

DOE PAGES

Mendl, C. B.; Nowadnick, E. A.; Huang, E. W.; ...

2017-11-15

Here, we present determinant quantum Monte Carlo simulations of the hole-doped single-band Hubbard-Holstein model on a square lattice, to investigate how quasiparticles emerge when doping a Mott insulator (MI) or a Peierls insulator (PI). The MI regime at large Hubbard interaction U and small relative e-ph coupling strength λ is quickly suppressed upon doping, by drawing spectral weight from the upper Hubbard band and shifting the lower Hubbard band towards the Fermi level, leading to a metallic state with emergent quasiparticles at the Fermi level. On the other hand, the PI regime at large λ and small U persists outmore » to relatively high doping levels. We study the evolution of the d-wave superconducting susceptibility with doping, and find that it increases with lowering temperature in a regime of intermediate values of U and λ.« less

Doping dependence of ordered phases and emergent quasiparticles in the doped Hubbard-Holstein model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mendl, C. B.; Nowadnick, E. A.; Huang, E. W.

Here, we present determinant quantum Monte Carlo simulations of the hole-doped single-band Hubbard-Holstein model on a square lattice, to investigate how quasiparticles emerge when doping a Mott insulator (MI) or a Peierls insulator (PI). The MI regime at large Hubbard interaction U and small relative e-ph coupling strength λ is quickly suppressed upon doping, by drawing spectral weight from the upper Hubbard band and shifting the lower Hubbard band towards the Fermi level, leading to a metallic state with emergent quasiparticles at the Fermi level. On the other hand, the PI regime at large λ and small U persists outmore » to relatively high doping levels. We study the evolution of the d-wave superconducting susceptibility with doping, and find that it increases with lowering temperature in a regime of intermediate values of U and λ.« less

Classical mapping for Hubbard operators: Application to the double-Anderson model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Bin; Miller, William H.; Levy, Tal J.

A classical Cartesian mapping for Hubbard operators is developed to describe the nonequilibrium transport of an open quantum system with many electrons. The mapping of the Hubbard operators representing the many-body Hamiltonian is derived by using analogies from classical mappings of boson creation and annihilation operators vis-à-vis a coherent state representation. The approach provides qualitative results for a double quantum dot array (double Anderson impurity model) coupled to fermionic leads for a range of bias voltages, Coulomb couplings, and hopping terms. While the width and height of the conduction peaks show deviations from the master equation approach considered to bemore » accurate in the limit of weak system-leads couplings and high temperatures, the Hubbard mapping captures all transport channels involving transition between many electron states, some of which are not captured by approximate nonequilibrium Green function closures.« less

Sandstone dykes in siwalik sandstone-sedimentology and basin analysis-subansiri district (NEFA), Eastern Himalaya

NASA Astrophysics Data System (ADS)

Kumar, Surendar; Singh, Trilochan

1982-11-01

Sandstone dykes (including sills) of varied thickness and with tapering ends are present either transecting or (sills) parallel to bedding in the Siwalik sandstone of Arunachal Pradesh (NEFA), Eastern Himalaya. The different sedimentary and microstructural analyses show varied conditions of deposition with changing facies from fluvial channel, to alluvial fan, to coastal plain-fan delta. The non-marine and shallow marine environments are indicated by the presence of organised and disorganised gradation and the presence of sandstone dykes in the interface regions. The orientations of the longer axes of the conglomerate along with the sand bedding indicate palaeoflow.

Does Deccan Volcanic Sequence contain more reversals than the three-Chron N-R-N flow magnetostratigraphy?- A paleomagnetic evidence from the dyke-swarm near Mumbai

NASA Astrophysics Data System (ADS)

Basavaiah, N.; Satyanarayana, KVV; Deenadayalan, K.; Prasad, JN

2018-02-01

New paleomagnetic data from a series of Deccan-age dykes cutting across the basement of lava flows along east and south of Mumbai (18°-19° N and 72°-73.5° E) have uncovered both normal (N) and reverse (R) magnetizations. Out of 33 dykes investigated, 29 dykes have yielded stable characteristic remanent magnetizations (ChRM) amenable for statistical analysis. Twenty dykes exhibit N-polarity and nine dykes show R-polarity. The tilt-corrected dyke VGPs reveal two distinct groups of dykes. Each group consists of both N- and R- polarity dykes on the Indian Apparent Polar Wander Path (APWP). The mean of N-polarity dykes is antipodal to the mean of R-polarity dykes. Group I (GI) comprises nine N-polarity dykes with their mean at Dm = 337.8°, Im = -39.4° (k = 130.7, α95 = 4.5°), and three dykes of R-polarity whose mean is at Dm = 150.7°, Im = 44.1° (k = 147.1, α95 = 10.2°). The corresponding pole positions are at 43.5° S, 102.6° E (A95 = 4.6°) and 36.6° S, 107.6° E (A95 = 8.9°) respectively. These pole positions fall close to 65 Ma old Deccan Superpole (DSP) on the APWP, and may therefore be associated with magnetic Chron 29 N for the N-polarity and 29R for the R-polarity of the three-Chron (30N - 29R -29Ν) magnetostratigraphy of the Deccan Volcanic Province (DVP) used in the computation of DSP. In Group II (GII), eleven dykes display N-polarity with mean at Dm = 312.6°, Im = -45.2° (k = 93.3, α95 = 4.8°) and six dykes show R-polarity with mean at Dm = 130.1°, Im = 48.0° (k = 176.8, α95 = 5.1°). The corresponding pole positions at 25° S, 120.1° E (A95 = 5.3°) and 22.2° S, 119.1° E (A95 = 5.2°) respectively are significantly displaced (by more than 20°) from the DSP along the older segment (˜80 -90 Ma) of the Indian APWP. Hence, the dykes of GII appear to have been emplaced in an earlier episodic Deccan activity than that represented by the DSP. The paleolatituides corresponding to GI and GII are 23.2° S ± 4.0 and 27.6° S ± 4

First-principles study of low-spin LaCoO3 with structurally consistent Hubbard U

NASA Astrophysics Data System (ADS)

Hsu, H.; Umemoto, K.; Cococcioni, M.; Wentzcovitch, R.

2008-12-01

We use the local density approximation + Hubbard U (LDA+U) method to calculate the structural and electronic properties of low-spin LaCoO3. The Hubbard U is obtained by first principles and consistent with each fully-optimized atomic structure at different pressures. With structurally consistent U, the fully-optimized atomic structure agrees with experimental data better than the calculations with fixed or vanishing U. A discussion on how the Hubbard U affects the electronic and atomic structure of LaCoO3 is also given.

Crossed cerebro-cerebellar atrophy with Dyke Davidoff Masson syndrome.

PubMed

Algahtani, Hussein A; Aldarmahi, Ahmed A; Al-Rabia, Mohammed W; Young, G Bryan

2014-01-01

Dyke Davidoff Masson syndrome (DDMS) refers to atrophy or hypoplasia of one cerebral hemisphere following a prior fetal or childhood insult. It has characteristics of clinical and radiological changes. These changes include hemiparesis, seizures, facial-asymmetry, and mental retardation. We present a 25-year-old man with crossed cerebrocerebellar atrophy and DDMS. His seizures were well controlled using a combination of antiepileptic drugs.

Equation of State of the Two-Dimensional Hubbard Model

NASA Astrophysics Data System (ADS)

Cocchi, Eugenio; Miller, Luke A.; Drewes, Jan H.; Koschorreck, Marco; Pertot, Daniel; Brennecke, Ferdinand; Köhl, Michael

2016-04-01

The subtle interplay between kinetic energy, interactions, and dimensionality challenges our comprehension of strongly correlated physics observed, for example, in the solid state. In this quest, the Hubbard model has emerged as a conceptually simple, yet rich model describing such physics. Here we present an experimental determination of the equation of state of the repulsive two-dimensional Hubbard model over a broad range of interactions 0 ≲U /t ≲20 and temperatures, down to kBT /t =0.63 (2 ) using high-resolution imaging of ultracold fermionic atoms in optical lattices. We show density profiles, compressibilities, and double occupancies over the whole doping range, and, hence, our results constitute benchmarks for state-of-the-art theoretical approaches.

Exotic superconducting states in the extended attractive Hubbard model.

PubMed

Nayak, Swagatam; Kumar, Sanjeev

2018-04-04

We show that the extended attractive Hubbard model on a square lattice allows for a variety of superconducting phases, including exotic mixed-symmetry phases with [Formula: see text] and [Formula: see text] symmetries, and a novel [Formula: see text] state. The calculations are performed within the Hartree-Fock Bardeen-Cooper-Schrieffer framework. The ground states of the mean-field Hamiltonian are obtained via a minimization scheme that relaxes the symmetry constraints on the superconducting solutions, hence allowing for a mixing of s-, p- and d-wave order parameters. The results are obtained within the assumption of uniform-density states. Our results show that extended attractive Hubbard model can serve as an effective model for investigating properties of exotic superconductors.

The role of local repulsion in superconductivity in the Hubbard-Holstein model

NASA Astrophysics Data System (ADS)

Lin, Chungwei; Wang, Bingnan; Teo, Koon Hoo

2017-01-01

We examine the superconducting solution in the Hubbard-Holstein model using Dynamical Mean Field Theory. The Holstein term introduces the site-independent Boson fields coupling to local electron density, and has two competing influences on superconductivity: The Boson field mediates the effective electron-electron attraction, which is essential for the S-wave electron pairing; the same coupling to the Boson fields also induces the polaron effect, which makes the system less metallic and thus suppresses superconductivity. The Hubbard term introduces an energy penalty U when two electrons occupy the same site, which is expected to suppress superconductivity. By solving the Hubbard-Holstein model using Dynamical Mean Field theory, we find that the Hubbard U can be beneficial to superconductivity under some circumstances. In particular, we demonstrate that when the Boson energy Ω is small, a weak local repulsion actually stabilizesthe S-wave superconducting state. This behavior can be understood as an interplay between superconductivity, the polaron effect, and the on-site repulsion: As the polaron effect is strong and suppresses superconductivity in the small Ω regime, the weak on-site repulsion reduces the polaron effect and effectively enhances superconductivity. Our calculation elucidates the role of local repulsion in the conventional S-wave superconductors.

Spectral properties near the Mott transition in the two-dimensional Hubbard model

NASA Astrophysics Data System (ADS)

Kohno, Masanori

2013-03-01

Single-particle excitations near the Mott transition in the two-dimensional (2D) Hubbard model are investigated by using cluster perturbation theory. The Mott transition is characterized by the loss of the spectral weight from the dispersing mode that leads continuously to the spin-wave excitation of the Mott insulator. The origins of the dominant modes of the 2D Hubbard model near the Mott transition can be traced back to those of the one-dimensional Hubbard model. Various anomalous spectral features observed in cuprate high-temperature superconductors, such as the pseudogap, Fermi arc, flat band, doping-induced states, hole pockets, and spinon-like and holon-like branches, as well as giant kink and waterfall in the dispersion relation, are explained in a unified manner as properties near the Mott transition in a 2D system.

Does Deccan Volcanic Sequence contain more reversals than the three-Chron N-R-N flow magnetostratigraphy?—a palaeomagnetic evidence from the dyke-swarm near Mumbai

NASA Astrophysics Data System (ADS)

Basavaiah, N.; Satyanarayana, K. VV; Deenadayalan, K.; Prasad, J. N.

2018-06-01

New palaeomagnetic data from a series of Deccan-age dykes cutting across the basement of lava flows along east and south of Mumbai (18°-19°N and 72°-73.5°E) have uncovered both normal (N) and reverse (R) magnetizations. Out of 33 dykes investigated, 29 dykes have yielded stable characteristic remanent magnetizations (ChRM) amenable for statistical analysis. Twenty dykes exhibit N-polarity and nine dykes show R-polarity. The tilt-corrected dyke virtual geomagnetic poles reveal two distinct groups of dykes. Each group consists of both N- and R-polarity dykes on the Indian apparent polar wander path (APWP). The mean of N-polarity dykes is antipodal to the mean of R-polarity dykes. Group I (GI) comprises nine N-polarity dykes with their mean at Dm = 337.8°, Im = -39.4° (k = 130.7, α95 = 4.5°), and three dykes of R-polarity whose mean is at Dm = 150.7°, Im = 44.1° (k = 147.1, α95 = 10.2°). The corresponding pole positions are at 43.5°S, 102.6°E (A95 = 4.6°) and 36.6°S, 107.6°E (A95 = 8.9°) respectively. These pole positions fall close to 65 Ma old Deccan Superpole (DSP) on the APWP, and may therefore be associated with magnetic Chron 29N for the N-polarity and 29R for the R-polarity of the three-Chron (30N-29R-29Ν) magnetostratigraphy of the Deccan Volcanic Province (DVP) used in the computation of DSP. In Group II (GII), eleven dykes display N-polarity with mean at Dm = 312.6°, Im = -45.2° (k = 93.3, α95 = 4.8°) and six dykes show R-polarity with mean at Dm = 130.1°, Im = 48.0° (k = 176.8, α95 = 5.1°). The corresponding pole positions at 25°S, 120.1°E (A95 = 5.3°) and 22.2°S, 119.1°E (A95 = 5.2°) respectively are significantly displaced (by more than 20°) from the DSP along the older segment (˜80-90 Ma) of the Indian APWP. Hence, the dykes of GII appear to have been emplaced in an earlier episodic Deccan activity than that represented by the DSP. The palaeolatituides corresponding to GI and GII are 23.2°S ± 4.0 and 27.6°S ± 4

Locating the quantum critical point of the Bose-Hubbard model through singularities of simple observables.

PubMed

Łącki, Mateusz; Damski, Bogdan; Zakrzewski, Jakub

2016-12-02

We show that the critical point of the two-dimensional Bose-Hubbard model can be easily found through studies of either on-site atom number fluctuations or the nearest-neighbor two-point correlation function (the expectation value of the tunnelling operator). Our strategy to locate the critical point is based on the observation that the derivatives of these observables with respect to the parameter that drives the superfluid-Mott insulator transition are singular at the critical point in the thermodynamic limit. Performing the quantum Monte Carlo simulations of the two-dimensional Bose-Hubbard model, we show that this technique leads to the accurate determination of the position of its critical point. Our results can be easily extended to the three-dimensional Bose-Hubbard model and different Hubbard-like models. They provide a simple experimentally-relevant way of locating critical points in various cold atomic lattice systems.

Early Jurassic mafic dykes from the Aigao uranium ore deposit in South China: Geochronology, petrogenesis and relationship with uranium mineralization

NASA Astrophysics Data System (ADS)

Zhang, Di; Zhao, Kui-Dong; Chen, Wei; Jiang, Shao-Yong

2018-05-01

Mafic dykes are abundant and widely distributed in many granite-hosted uranium ore deposits in South China. However, their geochronology, petrogenesis and relationship with uranium mineralization were poorly constrained. In this study, apatite U-Pb dating, whole-rock major and trace element and Sr-Nd-Pb isotope analysis were conducted for the dolerite dykes from the Aigao uranium ore deposit. Apatite U-Pb isotopic data indicate that the mafic dykes were emplaced at Early Jurassic (189 ± 4 Ma), which provides new evidence for the rarely identified Early Jurassic magmatism in South China. Pyroxene from the dykes is mainly augite, and plagioclase belongs to albite. The dolerite samples have relatively low SiO2 contents (45.33-46.79 wt%), relatively high total alkali contents (K2O + Na2O = 4.11-4.58 wt%) and Al2O3 contents (13.39-13.80 wt%), and medium MgO contents (4.29-5.16 wt%). They are enriched in Nb, Ta, Ti, rare earth elements and depleted in Rb, K, Sr, Th, showing the typical OIB-like geochemical affinity. All the dolerite samples show homogeneous Sr-Nd-Pb isotopic compositions, with (87Sr/86Sr)i varying from 0.706049 to 0.707137, εNd(t) from +4.6 to +5.2, 206Pb/204Pb from 19.032 to 19.126 and 207Pb/204Pb from 15.641 to 15.653. The mafic dykes in the Aigao deposit should be derived from the partial melting of the asthenospheric mantle and formed in a within-plate extensional environment. The emplacement age of the mafic dykes is older than the uranium mineralization age. Therefore, CO2 in ore-forming fluids couldn't originate from the basaltic magma as suggested by previous studies. The dolerite dykes might only provide a favorable reducing environment to promote the precipitation of uraninite from oxidize hydrothermal fluids.

Impacts of dyke development in flood prone areas in the Vietnamese Mekong Delta to downstream flood hazard

NASA Astrophysics Data System (ADS)

Khanh Triet Nguyen, Van; Dung Nguyen, Viet; Fujii, Hideto; Kummu, Matti; Merz, Bruno; Apel, Heiko

2017-04-01

Flooding in the Mekong Delta is an annual phenomenon causing inundation of large parts of the delta. This flooding is vital for the geomorphological stability of the delta, but is also the backbone of the highly productive agro-economy. However, extraordinary high floods are on the other hand a major hazard for the millions of people living in the delta. Therefore large scale developments of hydraulic structures took place in the Vietnamese part of the delta in the last decades. Particularly in the areas prone to deep and long lasting inundations many flood protection structures, mainly dykes, were built. These structures enable a blocking of inundation in large parts of these areas and by this the cropping of a third crop per year during the flood season. However, these structures are frequently blamed for increasing water levels in the areas downstream. Thus this study aimed at the investigation and attribution of changes in flood hazard in the Vietnamese Mekong Delta (VMD) due to high-dyke construction in deep flood prone areas, mainly in An Giang and Dong Thap provinces. This analysis started with the estimation of monotonic trends at key gauging stations in the delta: Kratie at the apex of the Mekong delta; Tan Chau and Chau Doc in the VMD just upstream of the areas with high-dyke construction; and Can Tho and My Thuan, located downstream of the high-dyke areas. The tests were undertaken assuming different magnitudes of errors in the data using historical records from 1978 - 2015, using the Mann-Kendall test and Sen's slope estimation. The obtained trends were thus tested for robustness against data errors. In order to obtain a better understanding of trends in the flood dynamics, the tests are performed on both flood peak and flood duration. In addition, the Pettitt test was applied to identify step changes in the water level data at 4 gauge stations located in the VMD. After the trend analysis, the impacts of high-dyke development were quantified with the

Les dykes basiques du massif ancien de l'Ourika (Atlas de Marrakech, Maroc): géochimie et significationThe basic dykes of the Ourika old massif (High Atlas of Marrakech): Geochemistry and significance

NASA Astrophysics Data System (ADS)

Barakat, Ahmed; Marignac, Christian; Bouabdelli, Mohamed

The Precambrian massif of Ourika is crosscut by two systems of basic dykes, striking N40°E and N90-120°E. Using incompatible trace elements, the two systems form two distinct chemical groups, displaying a continental tholeiitic affinity. The composition variations between the two defined groups can be due to heterogeneities of mantle sources and to contamination, during the magma ascent, by the continental crust. The emplacement of these basic dykes, before the late-PIII formations, can be related to the Neoproterozoic distension generalised to the Anti-Atlas chain. To cite this article: A. Barakat et al., C. R. Geoscience 334 (2002) 827-833.

Exotic superconducting states in the extended attractive Hubbard model

NASA Astrophysics Data System (ADS)

Nayak, Swagatam; Kumar, Sanjeev

2018-04-01

We show that the extended attractive Hubbard model on a square lattice allows for a variety of superconducting phases, including exotic mixed-symmetry phases with dx^2-y^2 + i [s + s^*] and dx^2-y^2 + px symmetries, and a novel px + i py state. The calculations are performed within the Hartree-Fock Bardeen-Cooper-Schrieffer framework. The ground states of the mean-field Hamiltonian are obtained via a minimization scheme that relaxes the symmetry constraints on the superconducting solutions, hence allowing for a mixing of s-, p- and d-wave order parameters. The results are obtained within the assumption of uniform-density states. Our results show that extended attractive Hubbard model can serve as an effective model for investigating properties of exotic superconductors.

Preliminary Geochemical Data for the Diabase Dykes from the Izmir-Ankara-Erzincan Suture Belt, Central Anatolia

NASA Astrophysics Data System (ADS)

Balcı, Uǧur; Sayıt, Kaan

2017-04-01

The Izmir-Ankara-Erzincan Suture Belt preserves oceanic and continental fragments originated from the closure of the northern branch of Neotethys. In the Bogazkale area (Central Anatolia), the pieces of the Neotethyan oceanic lithosphere exist in a chaotic manner, forming an ophiolitic mélange. Within the mélange, diabase dykes occur, which are found to cut various types of oceanic lithospheric rocks, including pillow basalts, gabbros and serpentinized ultramafics. We here present the preliminary geochemical results obtained from the diabase dykes and put some constraints on their petrogenesis. The investigated diabase dykes are chiefly composed of plagioclase and a mafic phase, which is clinopyroxene and/or hornblende. A detailed examination reveals two petrographic types on the basis of predominating mafic mineral phase, namely clinopyroxene-dominated Type 1, and hornblende-dominated Type 2. Ophitic to sub-ophitic textures, where lath-shaped plagioclase crystals are enclosed by clinopyroxene, can be observed in almost all Type 1 dykes. In Type 2 samples, altered mafic phases can be seen enclosed within plagioclase crystals, forming poikilitic texture. Polysynthetic twinning is common in plagioclase. Hornblende occasionally displays simple twinning. Both types appear to have been variably affected by low-grade hydrothermal alteration as reflected by the presence of secondary mineral phases, such as chlorite, epidote, prehnite, and actinolite. The whole-rock geochemistry appear to be consistent with the petrographical grouping, revealing distinct immobile trace element systematics for the two types. Both types have basaltic composition with sub-alkaline characteristics (Nb/Y=0.2-0.3 for Type 1; Nb/Y=0.02-0.08 for Type 2). The relatively low MgO contents of the dykes suggest that they do not represent primary magmas, but evolved through fractionation of mafic phases. In the N-MORB normalized diagrams, Type 2 diabases exhibit marked negative Nb anomalies, with HFSE

Phase competition in a one-dimensional three-orbital Hubbard-Holstein model

NASA Astrophysics Data System (ADS)

Li, Shaozhi; Tang, Yanfei; Maier, Thomas A.; Johnston, Steven

2018-05-01

We study the interplay between the electron-phonon (e -ph) and on-site electron-electron (e-e) interactions in a three-orbital Hubbard-Holstein model on an extended one-dimensional lattice using determinant quantum Monte Carlo. For weak e-e and e -ph interactions, we observe a competition between an orbital-selective Mott phase (OSMP) and a (multicomponent) charge-density-wave (CDW) insulating phase, with an intermediate metallic phase located between them. For large e-e and e -ph couplings, the OSMP and CDW phases persist, while the metallic phase develops short-range orbital correlations and becomes insulating when both the e-e and e -ph interactions are large but comparable. Many of our conclusions are in line with those drawn from a prior dynamical mean-field theory study of the two-orbital Hubbard-Holstein model [Phys. Rev. B 95, 121112(R) (2017), 10.1103/PhysRevB.95.121112] in infinite dimension, suggesting that the competition between the e -ph and e-e interactions in multiorbital Hubbard-Holstein models leads to rich physics, regardless of the dimension of the system.

Extended Hubbard model for mesoscopic transport in donor arrays in silicon

NASA Astrophysics Data System (ADS)

Le, Nguyen H.; Fisher, Andrew J.; Ginossar, Eran

2017-12-01

Arrays of dopants in silicon are promising platforms for the quantum simulation of the Fermi-Hubbard model. We show that the simplest model with only on-site interaction is insufficient to describe the physics of an array of phosphorous donors in silicon due to the strong intersite interaction in the system. We also study the resonant tunneling transport in the array at low temperature as a mean of probing the features of the Hubbard physics, such as the Hubbard bands and the Mott gap. Two mechanisms of localization which suppresses transport in the array are investigated: The first arises from the electron-ion core attraction and is significant at low filling; the second is due to the sharp oscillation in the tunnel coupling caused by the intervalley interference of the donor electron's wave function. This disorder in the tunnel coupling leads to a steep exponential decay of conductance with channel length in one-dimensional arrays, but its effect is less prominent in two-dimensional ones. Hence, it is possible to observe resonant tunneling transport in a relatively large array in two dimensions.

Magnetic resonance imaging depiction of acquired Dyke-Davidoff-Masson syndrome with crossed cerebro-cerebellar diaschisis: Report of two cases.

PubMed

Gupta, Ranjana; Joshi, Sandeep; Mittal, Amit; Luthra, Ishita; Mittal, Puneet; Verma, Vibha

2015-01-01

Acquired Dyke-Davidoff-Masson syndrome, also known as hemispheric atrophy, is characterized by loss of volume of one cerebral hemisphere from an insult in early life. Crossed cerebellar diaschisis refers to dysfunction/atrophy of cerebellar hemisphere which is secondary to contralateral supratentorial insult. We describe magnetic resonance imaging findings in two cases of acquired Dyke-Davidoff-Masson syndrome with crossed cerebro-cerebellar diaschisis.

Steady state current fluctuations and dynamical control in a nonequilibrium single-site Bose-Hubbard system

NASA Astrophysics Data System (ADS)

Chen, Xu-Min; Wang, Chen; Sun, Ke-Wei

2018-02-01

We investigate nonequilibrium energy transfer in a single-site Bose-Hubbard model coupled to two thermal baths. By including a quantum kinetic equation combined with full counting statistics, we investigate the steady state energy flux and noise power. The influence of the nonlinear Bose-Hubbard interaction on the transfer behaviors is analyzed, and the nonmonotonic features are clearly exhibited. Particularly, in the strong on-site repulsion limit, the results become identical with the nonequilibrium spin-boson model. We also extend the quantum kinetic equation to study the geometric-phase-induced energy pump. An interesting reversal behavior is unraveled by enhancing the Bose-Hubbard repulsion strength.

Ground-state properties of the three-band Hubbard model

NASA Astrophysics Data System (ADS)

Zhang, Shiwei; Vitali, Ettore; Chiciak, Adam; Shi, Hao

The three-band Hubbard model proposed by Emery describes the CuO2 plane in cuprate superconductors by retaining both Cu and O orbitals in a minimal sense. Applying the latest developments in the auxiliary-field quantum Monte Carlo (AFQMC) method, we investigate ground-state properties of this model at half-filling and when lightly (under-)doped. The AFQMC uses generalized Hartree-Fock (GHF) trial wave functions to control the sign problem. A self-consistent constraint is applied. We also determine the unrestricted Hartree-Fock (UHF) and GHF ground states and compare their predictions with those from AFQMC. Similarities and differences between the three-band model and one-band Hubbard model will be discussed. Supported by NSF, and the Simons Foundation. Computing is carried out at the Extreme Science and Engineering Discovery Environment(XSEDE).

Spin-imbalance in a 2D Fermi-Hubbard system

NASA Astrophysics Data System (ADS)

Brown, Peter T.; Mitra, Debayan; Guardado-Sanchez, Elmer; Schauß, Peter; Kondov, Stanimir S.; Khatami, Ehsan; Paiva, Thereza; Trivedi, Nandini; Huse, David A.; Bakr, Waseem S.

2017-09-01

The interplay of strong interactions and magnetic fields gives rise to unusual forms of superconductivity and magnetism in quantum many-body systems. Here, we present an experimental study of the two-dimensional Fermi-Hubbard model—a paradigm for strongly correlated fermions on a lattice—in the presence of a Zeeman field and varying doping. Using site-resolved measurements, we revealed anisotropic antiferromagnetic correlations, a precursor to long-range canted order. We observed nonmonotonic behavior of the local polarization with doping for strong interactions, which we attribute to the evolution from an antiferromagnetic insulator to a metallic phase. Our results pave the way to experimentally mapping the low-temperature phase diagram of the Fermi-Hubbard model as a function of both doping and spin polarization, for which many open questions remain.

Superconductivity from strong repulsive interactions in the two-dimensional Hubbard model

NASA Astrophysics Data System (ADS)

Sarasua, L. G.

2011-10-01

In this work, we study superconductivity in the strong coupling limit of the two-dimensional Hubbard model using a generalization of the Hubbard-I approximation. The results are compared with those obtained by Beenen and Edwards with the two-pole method of Roth, revealing a qualitative agreement between the two approaches. The effect of the hopping parameter t' between next-nearest neighbour sites on the critical temperature is considered. It is shown that the present approach reproduces the relation between t' and the maximum Tc in high temperature superconductors reported by Pavarini et al (2001 Phys. Rev. Lett. 87 047003).

Quench dynamics and nonequilibrium phase diagram of the bose-hubbard model.

PubMed

Kollath, Corinna; Läuchli, Andreas M; Altman, Ehud

2007-05-04

We investigate the time evolution of correlations in the Bose-Hubbard model following a quench from the superfluid to the Mott insulator. For large values of the final interaction strength the system approaches a distinctly nonequilibrium steady state that bears strong memory of the initial conditions. In contrast, when the final interaction strength is comparable to the hopping, the correlations are rather well approximated by those at thermal equilibrium. The existence of two distinct nonequilibrium regimes is surprising given the nonintegrability of the Bose-Hubbard model. We relate this phenomenon to the role of quasiparticle interactions in the Mott insulator.

Can we see the distal dyke communicate with the caldera? Examples of temporal correlation analysis using seismicity from the Bárðarbunga volcano

NASA Astrophysics Data System (ADS)

Jónsdóttir, Kristín; Jónasson, Kristján; Tumi Guðmundsson, Magnús; Hensch, Martin; Hooper, Andrew; Holohan, Eoghan; Sigmundsson, Freysteinn; Halldórsson, Sæmundur Ari; Vogfjörð, Kristín; Roberts, Matthew; Barsotti, Sara; Ófeigsson, Benedikt; Hjörleifsdóttir, Vala; Magnússon, Eyjólfur; Pálsson, Finnur; Parks, Michelle; Dumont, Stephanie; Einarsson, Páll; Guðmundsson, Gunnar

2016-04-01

The Bárðarbunga volcano is composed of a large oval caldera (7x11 km) and fissures extending tens of kilometers away from the caldera along the rift zone, which marks the divergent plate boundary across Iceland. On August 16th, 2014 an intense seismic swarm started below the Bárðarbunga caldera and in the two weeks that followed a dyke migrated some 47 km laterally in the uppermost 6-10 km of the crust along the rift. The dyke propagation terminated in lava fields just north of Vatnajökull glacier, where a major (1.5 km3) six months long eruption took place. Intense earthquake activity in the caldera started in the period August 21-24 with over 70 M5 earthquakes accompanying slow caldera collapse, as verified by various geodetic measurements. The subsidence is likely due to magma withdrawal from a reservoir at depth beneath the caldera. During a five months period, October-February, the seismic activity was separated by over 30 km in two clusters; one along the caldera rims (due to piecewise caldera subsidence) and the other at the far end of the dyke (as a result of small shear movements). Here we present statistical analysis comparing the temporal behaviour of seismicity recorded in the two clusters. By comparing the earthquake rate in the dyke in temporal bins before and after caldera subsidence earthquakes to the rate away from these bins (background rate), we show posing a statistical p-value test, that the number of dyke earthquakes was significantly higher (p <0.05) in the period 0-3 hours before a large earthquake (>M4.6) in the caldera. Increased dyke seismicity was also observed 0-3 hours following a large caldera earthquake. Elevated seismicity in the dyke before a large caldera earthquake may occur when a constriction in the dyke was reduced, followed by pressure drop in the chamber. Assuming that the large caldera earthquakes occurred when chamber pressure was lowest, the subsiding caldera piston may have caused temporary higher pressure in the

Ultramafic lavas and pyroxene-spinifex high-Mg basaltic dykes from the Othris ophiolite complex, Greece

NASA Astrophysics Data System (ADS)

Baziotis, Ioannis; Economou-Eliopoulos, Maria; Asimow, Paul

2017-04-01

This study aims to constrain the physico-chemical conditions and processes associated with the origin of ultramafic lavas of the Agrilia formation and high-Mg basaltic dykes in the Pournari area within the Othris ophiolite complex, a supra-subduction zone ophiolite of Mesozoic age (Paraskevopoulos & Economou, 1986; Barth et al., 2008). Hand-sample-scale spinifex texture is lacking from the ultramafic lavas and, despite whole-rock MgO contents greater than 31 wt.%, we infer an upper bound of 17 wt.% MgO for the erupted liquid, and thus identify these lavas as picrites containing accumulated olivine. We use textural and compositional criteria to divide the crystals within the Agrilia lavas between pre-eruptive and post-eruptive growth phases. The high-Mg basaltic dyke margins display a distinctive thin-section-scale micro-spinifex texture of skeletal and plumose Al- and Fe-rich clinopyroxene surrounded by large crystals of orthopyroxene. Normally zoned clinopyroxene in the Agrilia lavas and clinopyroxene of various textures (skeletal, needle- and dendritic-like) and sizes in the Pournari dykes display anomalous enrichment in Al2O3 and FeO* with decreasing MgO that require rapid, disequilibrium growth. Quantitative characteristics of the micro-spinifex pyroxene textures (<10 μm in width and 50-100 μm in length) imply a cooling rate for the marginal parts of the Pournari dykes of at least 25 °K/hr and more likely 45-55 °K/hr (Faure et al., 2004) and rapid growth of clinopyroxene crystals at a linear rate of about 10-6 m/s (Welsch et al., 2016). MELTS models of the crystallization sequence of the Pournari dykes indicate that progressive low-pressure (500 bar) fractional crystallization of the ultramafic dyke liquid occurred under oxidized (QFM+2.0) and hydrous (at least 0.5 wt.% H2O) conditions. A hydrous magmatic parent for the Othris ophiolite as a whole is further supported by preliminary investigation of melt inclusions (5-20 μm in diameter) in fresh chromite

78 FR 37270 - Qualification of Drivers; Exemption Applications; Vision

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-20

... (IA) Thomas M. Harris (MI) Paul M. Hinkson (TN) Ellie L. Murphree (AL) Michael P. Passmore (FL) Wendell S. Sehen (OH) Gary E. Valentine (OH) Kevin W. Van Arsdol (CO) Charles Van Dyke (WI) Harlon C. Van...

6. HUBBARD TUB, SHOWING WHIRLPOOL MOTOR OUTSIDE BATH STALL. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

6. HUBBARD TUB, SHOWING WHIRLPOOL MOTOR OUTSIDE BATH STALL. - Hot Springs National Park, Bathhouse Row, Quapaw Bathhouse: Mechanical & Piping Systems, State Highway 7, 1 mile north of U.S. Highway 70, Hot Springs, Garland County, AR

Floquet prethermalization in the resonantly driven Hubbard model

NASA Astrophysics Data System (ADS)

Herrmann, Andreas; Murakami, Yuta; Eckstein, Martin; Werner, Philipp

2017-12-01

We demonstrate the existence of long-lived prethermalized states in the Mott insulating Hubbard model driven by periodic electric fields. These states, which also exist in the resonantly driven case with a large density of photo-induced doublons and holons, are characterized by a nonzero current and an effective temperature of the doublons and holons which depends sensitively on the driving condition. Focusing on the specific case of resonantly driven models whose effective time-independent Hamiltonian in the high-frequency driving limit corresponds to noninteracting fermions, we show that the time evolution of the double occupation can be reproduced by the effective Hamiltonian, and that the prethermalization plateaus at finite driving frequency are controlled by the next-to-leading-order correction in the high-frequency expansion of the effective Hamiltonian. We propose a numerical procedure to determine an effective Hubbard interaction that mimics the correlation effects induced by these higher-order terms.

9. Historic American Buildings Survey Allen L. Hubbard, Photographer December ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

9. Historic American Buildings Survey Allen L. Hubbard, Photographer December 1, 1936 FIREPLACE (Southwest corner room 1st floor) - Fort Western, Main Building, Bowman Street, Augusta, Kennebec County, ME

4. Historic American Buildings Survey Allen L. Hubbard, Photographer December ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

4. Historic American Buildings Survey Allen L. Hubbard, Photographer December 1, 1936 FIREPLACE WALL (northwest room 1st floor) - Fort Western, Main Building, Bowman Street, Augusta, Kennebec County, ME

7. Historic American Buildings Survey Cortlandt V. D. Hubbard, Photographer ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

7. Historic American Buildings Survey Cortlandt V. D. Hubbard, Photographer June 1965 DETAIL, PAINTING ON FLOOR OF SECOND FLOOR - Swain-Mitchell House, 1 Vestal Street, Nantucket, Nantucket County, MA

Mott-Hubbard transition and Anderson localization: A generalized dynamical mean-field theory approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuchinskii, E. Z.; Nekrasov, I. A.; Sadovskii, M. V.

The DOS, the dynamic (optical) conductivity, and the phase diagram of a strongly correlated and strongly disordered paramagnetic Anderson-Hubbard model are analyzed within the generalized dynamical mean field theory (DMFT + {sigma} approximation). Strong correlations are taken into account by the DMFT, and disorder is taken into account via an appropriate generalization of the self-consistent theory of localization. The DMFT effective single-impurity problem is solved by a numerical renormalization group (NRG); we consider the three-dimensional system with a semielliptic DOS. The correlated metal, Mott insulator, and correlated Anderson insulator phases are identified via the evolution of the DOS and dynamicmore » conductivity, demonstrating both the Mott-Hubbard and Anderson metal-insulator transition and allowing the construction of the complete zero-temperature phase diagram of the Anderson-Hubbard model. Rather unusual is the possibility of a disorder-induced Mott insulator-to-metal transition.« less

Valence-bond theory of linear Hubbard and Pariser-Parr-Pople models

NASA Astrophysics Data System (ADS)

Soos, Z. G.; Ramasesha, S.

1984-05-01

The ground and low-lying states of finite quantum-cell models with one state per site are obtained exactly through a real-space basis of valence-bond (VB) diagrams that explicitly conserve the total spin. Regular and alternating Hubbard and Pariser-Parr-Pople (PPP) chains and rings with Ne electrons on N(<=12) sites are extrapolated to infinite arrays. The ground-state energy and optical gap of regular U=4|t| Hubbard chains agree with exact results, suggesting comparable accuracy for alternating Hubbard and PPP models, but differ from mean-field results. Molecular PPP parameters describe well the excitations of finite polyenes, odd polyene ions, linear cyanine dyes, and slightly overestimate the absorption peaks in polyacetylene (CH)x. Molecular correlations contrast sharply with uncorrelated descriptions of topological solitons, which are modeled by regular polyene radicals and their ions for both wide and narrow alternation crossovers. Neutral solitons have no midgap absorption and negative spin densities, while the intensity of the in-gap excitation of charged solitons is not enhanced. The properties of correlated states in quantum-cell models with one valence state per site are discussed in the adiabatic limit for excited-state geometries and instabilities to dimerization.

A Quasi-Classical Model of the Hubbard Gap in Lightly Compensated Semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poklonski, N. A.; Vyrko, S. A.; Kovalev, A. I.

2016-03-15

A quasi-classical method for calculating the narrowing of the Hubbard gap between the A{sup 0} and A{sup +} acceptor bands in a hole semiconductor or the D{sup 0} and D{sup –} donor bands in an electron semiconductor is suggested. This narrowing gives rise to the phenomenon of a semiconductor transition from the insulator to metal state with an increase in doping level. The major (doping) impurity can be in one of three charge states (–1, 0, or +1), while the compensating impurity can be in states (+1) or (–1). The impurity distribution over the crystal is assumed to be randommore » and the width of Hubbard bands (levels), to be much smaller than the gap between them. It is shown that narrowing of the Hubbard gap is due to the formation of electrically neutral acceptor (donor) states of the quasicontinuous band of allowed energies for holes (electrons) from excited states. This quasicontinuous band merges with the top of the valence band (v band) for acceptors or with the bottom of the conduction band (c band) for donors. In other words, the top of the v band for a p-type semiconductor or the bottom of the c band for an n-type semiconductor is shifted into the band gap. The value of this shift is determined by the maximum radius of the Bohr orbit of the excited state of an electrically neutral major impurity atom, which is no larger than half the average distance between nearest impurity atoms. As a result of the increasing dopant concentration, the both Hubbard energy levels become shallower and the gap between them narrows. Analytical formulas are derived to describe the thermally activated hopping transition of holes (electrons) between Hubbard bands. The calculated gap narrowing with increasing doping level, which manifests itself in a reduction in the activation energy ε{sub 2} is consistent with available experimental data for lightly compensated p-Si crystals doped with boron and n-Ge crystals doped with antimony.« less

8. Historic American Buildings Survey Allen L. Hubbard, Photographer December ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

8. Historic American Buildings Survey Allen L. Hubbard, Photographer December 1, 1936 FIREPLACE (1st floor east central room) (kitchen) - Fort Western, Main Building, Bowman Street, Augusta, Kennebec County, ME

12. Historic American Buildings Survey Allen L. Hubbard, Photographer December ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

12. Historic American Buildings Survey Allen L. Hubbard, Photographer December 1, 1936 CHEST (North room 3rd floor) (SWISS FURNITURE) - Fort Western, Main Building, Bowman Street, Augusta, Kennebec County, ME

13. Historic American Buildings Survey Allen L. Hubbard, Photographer December ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

13. Historic American Buildings Survey Allen L. Hubbard, Photographer December 1, 1936 CHEST (North room 3rd floor) (SWISS FURNITURE) - Fort Western, Main Building, Bowman Street, Augusta, Kennebec County, ME

11. Historic American Buildings Survey Allen L. Hubbard, Photographer December ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

11. Historic American Buildings Survey Allen L. Hubbard, Photographer December 1, 1936 SOUTHWEST CORNER ROOM (2nd floor, east wall) - Fort Western, Main Building, Bowman Street, Augusta, Kennebec County, ME

10. Historic American Buildings Survey Allen L. Hubbard, Photographer December ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

10. Historic American Buildings Survey Allen L. Hubbard, Photographer December 1, 1936 (Northwest cor. room 2nd floor) East Wall - Fort Western, Main Building, Bowman Street, Augusta, Kennebec County, ME

Quantum simulation of a Fermi-Hubbard model using a semiconductor quantum dot array.

PubMed

Hensgens, T; Fujita, T; Janssen, L; Li, Xiao; Van Diepen, C J; Reichl, C; Wegscheider, W; Das Sarma, S; Vandersypen, L M K

2017-08-02

Interacting fermions on a lattice can develop strong quantum correlations, which are the cause of the classical intractability of many exotic phases of matter. Current efforts are directed towards the control of artificial quantum systems that can be made to emulate the underlying Fermi-Hubbard models. Electrostatically confined conduction-band electrons define interacting quantum coherent spin and charge degrees of freedom that allow all-electrical initialization of low-entropy states and readily adhere to the Fermi-Hubbard Hamiltonian. Until now, however, the substantial electrostatic disorder of the solid state has meant that only a few attempts at emulating Fermi-Hubbard physics on solid-state platforms have been made. Here we show that for gate-defined quantum dots this disorder can be suppressed in a controlled manner. Using a semi-automated and scalable set of experimental tools, we homogeneously and independently set up the electron filling and nearest-neighbour tunnel coupling in a semiconductor quantum dot array so as to simulate a Fermi-Hubbard system. With this set-up, we realize a detailed characterization of the collective Coulomb blockade transition, which is the finite-size analogue of the interaction-driven Mott metal-to-insulator transition. As automation and device fabrication of semiconductor quantum dots continue to improve, the ideas presented here will enable the investigation of the physics of ever more complex many-body states using quantum dots.

Long-period seismicity reveals magma pathways above a laterally propagating dyke during the 2014-15 Bárðarbunga rifting event, Iceland

NASA Astrophysics Data System (ADS)

Woods, Jennifer; Donaldson, Clare; White, Robert S.; Caudron, Corentin; Brandsdóttir, Bryndís; Hudson, Thomas S.; Ágústsdóttir, Thorbjörg

2018-05-01

The 2014-15 Bárðarbunga-Holuhraun rifting event comprised the best-monitored dyke intrusion to date and the largest eruption in Iceland in 230 years. A huge variety of seismicity was produced, including over 30,000 volcano-tectonic earthquakes (VTs) associated with the dyke propagation at ∼6 km depth below sea level, and large-magnitude earthquakes accompanying the collapse of Bárðarbunga caldera. We here study the long-period seismicity associated with the rifting event. We systematically detect and locate both long-period events (LPs) and tremor during the dyke propagation phase and the first week of the eruption. We identify clusters of highly similar, repetitive LPs, which have a peak frequency of ∼1 Hz and clear P and S phases followed by a long-duration coda. The source mechanisms are remarkably consistent between clusters and also fundamentally different to those of the VTs. We accurately locate LP clusters near each of three ice cauldrons (depressions formed by basal melting) that were observed on the surface of Dyngjujökull glacier above the path of the dyke. Most events are in the vicinity of the northernmost cauldron, at shallower depth than the VTs associated with lateral dyke propagation. At the two northerly cauldrons, periods of shallow seismic tremor following the clusters of LPs are also observed. Given that the LPs occur at ∼4 km depth and in swarms during times of dyke-stalling, we infer that they result from excitation of magmatic fluid-filled cavities and indicate magma ascent. We suggest that the tremor is the climax of the vertical melt movement, arising from either rapid, repeated excitation of the same LP cavities, or sub-glacial eruption processes. This long-period seismicity therefore represents magma pathways between the depth of the dyke-VT earthquakes and the surface. Notably, we do not detect tremor associated with each cauldron, despite melt reaching the base of the overlying ice cap, a concern for hazard monitoring.

Hubbard physics in the PAW GW approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Booth, J. M., E-mail: jamie.booth@rmit.edu.au; Smith, J. S.; Russo, S. P.

It is demonstrated that the signatures of the Hubbard Model in the strongly interacting regime can be simulated by modifying the screening in the limit of zero wavevector in Projector-Augmented Wave GW calculations for systems without significant nesting. This modification, when applied to the Mott insulator CuO, results in the opening of the Mott gap by the splitting of states at the Fermi level into upper and lower Hubbard bands, and exhibits a giant transfer of spectral weight upon electron doping. The method is also employed to clearly illustrate that the M{sub 1} and M{sub 2} forms of vanadium dioxidemore » are fundamentally different types of insulator. Standard GW calculations are sufficient to open a gap in M{sub 1} VO{sub 2}, which arise from the Peierls pairing filling the valence band, creating homopolar bonds. The valence band wavefunctions are stabilized with respect to the conduction band, reducing polarizability and pushing the conduction band eigenvalues to higher energy. The M{sub 2} structure, however, opens a gap from strong on-site interactions; it is a Mott insulator.« less

Improvement of 2D ERT measurements conducted along a small earth-filled dyke using 3D topographic data and 3D computation of geometric factors

NASA Astrophysics Data System (ADS)

Bièvre, Grégory; Oxarango, Laurent; Günther, Thomas; Goutaland, David; Massardi, Michael

2018-06-01

In the framework of earth-filled dykes characterization and monitoring, Electrical Resistivity Tomography (ERT) turns out to be a commonly used method. 2D sections are generally acquired along the dyke crest thus putting forward the question of 3D artefacts in the inversion process. This paper proposes a methodology based on 3D direct numerical simulations of the ERT acquisition using a realistic topography of the study site. It allows computing ad hoc geometrical factors which can be used for the inversion of experimental ERT data. The method is first evaluated on a set of synthetic dyke configurations. Then, it is applied to experimental static and time-lapse ERT data set acquired before and after repair works carried out on a leaking zone of an earth-filled canal dyke in the centre of France. The computed geometric factors are lower than the analytic geometric factors in a range between -8% and - 18% for measurements conducted on the crest of the dyke. They exhibit a maximum under-estimation for intermediate electrode spacings in the Wenner and Schlumberger configurations. In the same way, for measurements conducted on the mid-slope of the dyke, the computed geometric factors are higher for short electrode spacings (+18%) and lower for lower for large electrode spacings (-8%). The 2D inversion of the synthetic data with these computed geometric factors provides a significant improvement of the agreement with the original resistivity. Two experimental profiles conducted on the same portion of the dyke but at different elevations also reveal a better agreement using this methodology. The comparison with apparent resistivity from EM31 profiling along the stretch of the dyke also supports this evidence. In the same way, some spurious effects which affected the time-lapse data were removed and improved the global readability of the time-lapse resistivity sections. The benefit on the structural interpretation of ERT images remains moderate but allows a better

Phase diagram and re-entrant fermionic entanglement in a hybrid Ising-Hubbard ladder

NASA Astrophysics Data System (ADS)

Sousa, H. S.; Pereira, M. S. S.; de Oliveira, I. N.; Strečka, J.; Lyra, M. L.

2018-05-01

The degree of fermionic entanglement is examined in an exactly solvable Ising-Hubbard ladder, which involves interacting electrons on the ladder's rungs described by Hubbard dimers at half-filling on each rung, accounting for intrarung hopping and Coulomb terms. The coupling between neighboring Hubbard dimers is assumed to have an Ising-like nature. The ground-state phase diagram consists of four distinct regions corresponding to the saturated paramagnetic, the classical antiferromagnetic, the quantum antiferromagnetic, and the mixed classical-quantum phase. We have exactly computed the fermionic concurrence, which measures the degree of quantum entanglement between the pair of electrons on the ladder rungs. The effects of the hopping amplitude, the Coulomb term, temperature, and magnetic fields on the fermionic entanglement are explored in detail. It is shown that the fermionic concurrence displays a re-entrant behavior when quantum entanglement is being generated at moderate temperatures above the classical saturated paramagnetic ground state.

Spectral weight of excitations in Bose Hubbard model

NASA Astrophysics Data System (ADS)

Alavani, Bhargav K.; Pai, Ramesh V.

2017-05-01

We obtain excitation spectra in the superfluid and the Mott Insulator phases of Bose Hubbard model near unit filling within Random Phase Approximation (RPA) and calculate its spectral weight. This gives a transparent description of contribution of each excitation towards the total Density of States (DOS) which we calculate from these spectral weights.

5. Historic American Buildings Survey Cortlandt V. D. Hubbard, Photographer ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

5. Historic American Buildings Survey Cortlandt V. D. Hubbard, Photographer July 1966 FIRST FLOOR REAR HALL (NOTE: FLOOR PAINTED WITH A FEATHER BRUSH) - Thaddeus Coffin House, 89 Main Street, Nantucket, Nantucket County, MA

Interaction effect in the Kondo energy of the periodic Anderson-Hubbard model

NASA Astrophysics Data System (ADS)

Itai, K.; Fazekas, P.

1996-07-01

We extend the periodic Anderson model by switching on a Hubbard U for the conduction band. The nearly integral valent limit of the Anderson-Hubbard model is studied with the Gutzwiller variational method. The lattice Kondo energy shows U dependence both in the prefactor and the exponent. Switching on U reduces the Kondo scale, which can be understood to result from the blocking of hybridization. At half filling, we find a Brinkman-Rice-type transition from a Kondo insulator to a Mott insulator. Our findings should be relevant for a number of correlated two-band models of recent interest.

Magnon edge states in the hardcore- Bose-Hubbard model.

PubMed

Owerre, S A

2016-11-02

Quantum Monte Carlo (QMC) simulation has uncovered nonzero Berry curvature and bosonic edge states in the hardcore-Bose-Hubbard model on the gapped honeycomb lattice. The competition between the chemical potential and staggered onsite potential leads to an interesting quantum phase diagram comprising the superfluid phase, Mott insulator, and charge density wave insulator. In this paper, we present a semiclassical perspective of this system by mapping to a spin-1/2 quantum XY model. We give an explicit analytical origin of the quantum phase diagram, the Berry curvatures, and the edge states using semiclassical approximations. We find very good agreement between the semiclassical analyses and the QMC results. Our results show that the topological properties of the hardcore-Bose-Hubbard model are the same as those of magnon in the corresponding quantum spin system. Our results are applicable to systems of ultracold bosonic atoms trapped in honeycomb optical lattices.

Precise 40Ar/39Ar dating of basaltic dykes as an indicator of paleostress: exemple of the Icelandic rift jumps.

NASA Astrophysics Data System (ADS)

Arnaud, N. O.; Garcia, S.; Bergerat, F.

2003-04-01

Dykes constitute unique indicators of local paleostress. When compiled over a large area and over a significant time span they also underline larger changes in the global field stress and thus may be used together with the present day finite deformation to address global geodynamical problems. However, their use has often proved problematic because of their cryptic nature favouring excess argon retention or intake from the host rocks, as well as hydrothermal circulations and groundmass alteration. These flaws can be overtaken by careful sampling and specific sample preparation to get rid of “polluting” phases, reduction of the amount of used material using only hand picked glassy mesostasis, and replication of the analysis on several aliquots. This protocol allows to increase the number of significant results. In Iceland, rift zones have kept jumping for the past 20 Ma and probably even earlier as a response to the discontinuous capture of the mid-ocean ridge by the underlying Icelandic hotspot. However, direct determination of the age and location of paleorift zones has proven problematic because of rapid changes in the dipping of the lavas associated to overcasting of the oldest flows by younger ones, and also because of the retreat and discontinuity of flows associated with the severe glacial erosion. Dykes however do not suffer such problems and constitute excellent space/time indicators. About 65 dykes have systematically been dated on a 350 km long E-W cross section across the Northern Volcanic Zone, from the Vatnsnes peninsula to the east coast across the presently active Krafla rift. Excess argon proved to be rare, probably because of similar age and petrography between host rocks and intrusive dykes, although the basaltic dykes remain poor in potassium. Alteration of the groundmass was sometimes severe but replicate analysis usually helped in assessing a significant age. The final age distribution profile obtained from this important amount of data

Late Permian volcanic dykes in the crystalline basement of the Považský Inovec Mts. (Western Carpathians): U-Th-Pb zircon SHRIMP and monazite chemical dating

NASA Astrophysics Data System (ADS)

Pelech, Ondrej; Vozárová, Anna; Uher, Pavel; Petrík, Igor; Plašienka, Dušan; Šarinová, Katarína; Rodionov, Nikolay

2017-08-01

This paper presents geochronological data for the volcanic dykes located in the northern Považský Inovec Mts. The dykes are up to 5 m thick and tens to hundreds of metres long. They comprise variously inclined and oriented lenses, composed of strongly altered grey-green alkali basalts. Their age was variously interpreted and discussed in the past. Dykes were emplaced into the Tatricum metamorphic rocks, mostly consisting of mica schists and gneisses of the Variscan (early Carboniferous) age. Two different methods, zircon SHRIMP and monazite chemical dating, were applied to determine the age of these dykes. U-Pb SHRIMP dating of magmatic zircons yielded the concordia age of 260.2 ± 1.4 Ma. The Th-U-Pb monazite dating of the same dyke gave the CHIME age of 259 ± 3Ma. Both ages confirm the magmatic crystallization at the boundary of the latest Middle Permian to the Late Permian. Dyke emplacement was coeval with development of the Late Paleozoic sedimentary basin known in the northern Považský Inovec Mts. and could be correlated with other pre-Mesozoic Tethyan regions especially in the Southern Alps.

Dyke-Davidoff-Masson syndrome: case report of fetal unilateral ventriculomegaly and hypoplastic left middle cerebral artery.

PubMed

Piro, Ettore; Piccione, Maria; Marrone, Gianluca; Giuffrè, Mario; Corsello, Giovanni

2013-05-14

Prenatal ultrasonographic detection of unilateral cerebral ventriculomegaly arises suspicion of pathological condition related to cerebrospinal fluid flow obstruction or cerebral parenchimal pathology. Dyke-Davidoff-Masson syndrome is a rare condition characterized by cerebral hemiatrophy, calvarial thickening, skull and facial asymmetry, contralateral hemiparesis, cognitive impairment and seizures. Congenital and acquired types are recognized and have been described, mainly in late childhood, adolescence and adult ages. We describe a female infant with prenatal diagnosis of unilateral left ventriculomegaly in which early brain MRI and contrast enhanced-MRI angiography, showed cerebral left hemiatrophy associated with reduced caliber of the left middle cerebral artery revealing the characteristic findings of the Dyke-Davidoff-Masson syndrome. Prenatal imaging, cerebral vascular anomaly responsible for the cerebral hemiatrophy and the early clinical evolution have never been described before in such a young child and complete the acquired clinical descriptions in older children. Differential diagnosis, genetic investigations, neurophysiologic assessments, short term clinical and developmental follow up are described. Dyke-Davidoff-Masson syndrome must be ruled out in differential diagnosis of fetal unilateral ventriculomegaly. Early clinical assessment, differential diagnosis and cerebral imaging including cerebral MRI angiography allow the clinicians to diagnose also in early infancy this rare condition.

Bose-Hubbard lattice as a controllable environment for open quantum systems

NASA Astrophysics Data System (ADS)

Cosco, Francesco; Borrelli, Massimo; Mendoza-Arenas, Juan José; Plastina, Francesco; Jaksch, Dieter; Maniscalco, Sabrina

2018-04-01

We investigate the open dynamics of an atomic impurity embedded in a one-dimensional Bose-Hubbard lattice. We derive the reduced evolution equation for the impurity and show that the Bose-Hubbard lattice behaves as a tunable engineered environment allowing one to simulate both Markovian and non-Markovian dynamics in a controlled and experimentally realizable way. We demonstrate that the presence or absence of memory effects is a signature of the nature of the excitations induced by the impurity, being delocalized or localized in the two limiting cases of a superfluid and Mott insulator, respectively. Furthermore, our findings show how the excitations supported in the two phases can be characterized as information carriers.

2. Historic American Buildings Survey Cortlandt V. D. Hubbard, Photographer ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. Historic American Buildings Survey Cortlandt V. D. Hubbard, Photographer June 1965 REAR ELEVATION OF HOUSE AND SUMMER KITCHEN (c. 1850) AND STAFF QUARTERS (1933) - Swain-Mitchell House, 1 Vestal Street, Nantucket, Nantucket County, MA

A new 200 Ma paleomagnetic pole for Africa, and paleo-secular variation scatter from Central Atlantic Magmatic Province (CAMP) intrusives in Morocco (Ighrem and Foum Zguid dykes)

NASA Astrophysics Data System (ADS)

Palencia-Ortas, A.; Ruiz-Martínez, V. C.; Villalaín, J. J.; Osete, M. L.; Vegas, R.; Touil, A.; Hafid, A.; McIntosh, G.; van Hinsbergen, D. J. J.; Torsvik, T. H.

2011-06-01

Available apparent polar wander (APW) paths for the 200 Ma configuration of Pangea, just prior to the opening of the Central Atlantic Ocean, differ as much as 10o in arc length. Here, we add new data from northwest Africa for this time, obtained from the northeast-trending Foum-Zguid and Ighrem dykes (ca. 200 Ma). These dykes form part of the northern domain of the Central Atlantic Magmatic Province (CAMP), and crosscut the Anti-Atlas Ranges in Morocco, and compositionally correspond to quartz-normative tholeiites intruded in continental lithosphere shortly before the opening of the Central Atlantic Ocean. The Foum-Zguid dyke has been intensively studied, whereas the Ighrem dyke has received less scientific focus. We sampled both dykes for paleomagnetic investigation along 100 km of each dyke (12 sites for Foum-Zguid and 11 for Ighrem, 188 samples included in the final analyses). Rock magnetic experiments indicate a mixture of multidomain and single-domain magnetite and/or low-Ti titanomagnetite particles as the principal remanence carriers. In both dykes, the primary nature of the characteristic remanent magnetization is supported by positive contact tests, related to Fe-metasomatism or baked overprints of the corresponding sedimentary country rocks. The directions of the characteristic magnetization exhibit exclusively normal polarity. Site-mean virtual geomagnetic poles are differently grouped in each dyke, suggesting distinct geomagnetic secular variation records. The Foum-Zguid paleomagnetic pole (N= 12, PLat= 67.9°N, PLon= 247.9°E, κ= 125, A95= 3.9°) plots close to that of Ighrem (N= 11, PLat= 78.4°N, PLon= 238.2°E, κ= 47, A95= 6.7°), confirming those mineralogical and geochemical evidences supporting that they represent dissimilar magmatic stages. Virtual geomagnetic poles dispersion from both dykes (S= 10.5°13.0°8.1°) is in line with those obtained from recent studies of a CAMP-related dyke in Iberia and results from CAMP lavas in the Argana

6. Cortlandt V.D. Hubbard, Photographer November 1967 MAIN LOBBY, LOOKING ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

6. Cortlandt V.D. Hubbard, Photographer November 1967 MAIN LOBBY, LOOKING SOUTH, WITH STAIRCASE IN FOREGROUND - American Academy of Music, 232-246 South Broad Street, Philadelphia, Philadelphia County, PA

10. Cortlandt V.D. Hubbard, Photographer November 1967 STAGE, BOXES, ORGAN ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

10. Cortlandt V.D. Hubbard, Photographer November 1967 STAGE, BOXES, ORGAN PIPES TAKEN FROM OBLIQUE ANGLE - American Academy of Music, 232-246 South Broad Street, Philadelphia, Philadelphia County, PA

Stripe order from the perspective of the Hubbard model

DOE PAGES

Huang, Edwin W.; Mendl, Christian B.; Jiang, Hong-Chen; ...

2018-04-20

A microscopic understanding of the strongly correlated physics of the cuprates must account for the translational and rotational symmetry breaking that is present across all cuprate families, commonly in the form of stripes. Here we investigate emergence of stripes in the Hubbard model, a minimal model believed to be relevant to the cuprate superconductors, using determinant quantum Monte Carlo (DQMC) simulations at finite temperatures and density matrix renormalization group (DMRG) ground state calculations. By varying temperature, doping, and model parameters, we characterize the extent of stripes throughout the phase diagram of the Hubbard model. Our results show that including themore » often neglected next-nearest-neighbor hopping leads to the absence of spin incommensurability upon electron-doping and nearly half-filled stripes upon hole-doping. The similarities of these findings to experimental results on both electron and hole-doped cuprate families support a unified description across a large portion of the cuprate phase diagram.« less

Observation of antiferromagnetic correlations in the Fermi-Hubbard model

NASA Astrophysics Data System (ADS)

Hart, R. A.; Duarte, P. M.; Yang, T. L.; Liu, X.; Hulet, R. G.; Paiva, T. C. L.; Huse, D.; Scalettar, R. T.; Trivedi, N.

2014-05-01

The physics of high temperature superconductors is not well understood, although it is known that the undoped parent compounds of many of them are antiferromagnetic (AF) insulators. The Fermi-Hubbard model at half filling (one atom per lattice site) is known to exhibit a phase transition to an antiferromagnetic insulator at a low temperature. We realize the Fermi-Hubbard model by loading ultracold 6Li atoms into a three-dimensional red-detuned optical lattice. We have compensated the confining potential of the lattice with blue-detuned laser beams in order to evaporatively cool the atoms. We have cooled sufficiently to observe AF correlations using spin-sensitive Bragg scattering of near-resonant light. Comparison with Quantum Monte Carlo (QMC) calculations indicates that the temperature is between 2-3 TN, where short-range correlations begin to develop. Bragg scattering combined with QMC provides sensitive thermometry in a previously unexplored regime. Supported by NSF, ONR, DARPA, and the Welch Foundation.

Stripe order from the perspective of the Hubbard model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Edwin W.; Mendl, Christian B.; Jiang, Hong-Chen

A microscopic understanding of the strongly correlated physics of the cuprates must account for the translational and rotational symmetry breaking that is present across all cuprate families, commonly in the form of stripes. Here we investigate emergence of stripes in the Hubbard model, a minimal model believed to be relevant to the cuprate superconductors, using determinant quantum Monte Carlo (DQMC) simulations at finite temperatures and density matrix renormalization group (DMRG) ground state calculations. By varying temperature, doping, and model parameters, we characterize the extent of stripes throughout the phase diagram of the Hubbard model. Our results show that including themore » often neglected next-nearest-neighbor hopping leads to the absence of spin incommensurability upon electron-doping and nearly half-filled stripes upon hole-doping. The similarities of these findings to experimental results on both electron and hole-doped cuprate families support a unified description across a large portion of the cuprate phase diagram.« less

Finite-temperature dynamics of the Mott insulating Hubbard chain

NASA Astrophysics Data System (ADS)

Nocera, Alberto; Essler, Fabian H. L.; Feiguin, Adrian E.

2018-01-01

We study the dynamical response of the half-filled one-dimensional Hubbard model for a range of interaction strengths U and temperatures T by a combination of numerical and analytical techniques. Using time-dependent density matrix renormalization group computations we find that the single-particle spectral function undergoes a crossover to a spin-incoherent Luttinger liquid regime at temperatures T ˜J =4 t2/U for sufficiently large U >4 t . At smaller values of U and elevated temperatures the spectral function is found to exhibit two thermally broadened bands of excitations, reminiscent of what is found in the Hubbard-I approximation. The dynamical density-density response function is shown to exhibit a finite-temperature resonance at low frequencies inside the Mott gap, with a physical origin similar to the Villain mode in gapped quantum spin chains. We complement our numerical computations by developing an analytic strong-coupling approach to the low-temperature dynamics in the spin-incoherent regime.

Palaeoproterozoic Indian shield in the global continental assembly: Evidence from the palaeomagnetism of mafic dyke swarms

NASA Astrophysics Data System (ADS)

Radhakrishna, T.; Krishnendu, N. R.; Balasubramonian, G.

2013-11-01

Palaeomagnetic study of Palaeoproterozoic mafic dykes in the basement along the margins of the Cuddapah basin, the largest Precambrian sedimentary basin in south India, is presented in detail for a general discussion of Palaeoproterozoic igneous activity in India. The results are compared with all earlier published data on mafic dykes in India and are integrated with recently-published high-precision U-Pb baddeleyite ages to provide a comprehensive account of Palaeoproterozoic igneous activity in India. The analysis consolidates palaeomagnetic poles for six age divisions between 2.45 and 1.85 Ga with robust statistical criteria. Our best estimates of overall mean poles from 241 dykes are situated at (1) λ = 17.7°N; Φ = 106.0°E (A95 = 9.0°; 7N = 24) at c. 2.45 Ga, (2) λ = 7.1°N; Φ = 57.2°E (A95 = 4.5°; N = 69) at c. 2.37 Ga, (3) λ = 41.6°S; Φ = 5.5°E (A95 = 5.1°; N = 34) at c. 2.22 Ga, (4) λ = 4.7°N; Φ = 343.0°E (A95 = 4.4°; N = 31) at 2.18 Ga, (5) λ = 49.2°N; Φ = 332.9°E (A95 = 4.8°; N = 24) at 1.99-1.89 Ga and (6) λ = 73.7°N; Φ = 282.6°E (A95 = 2.9°; N = 39) at 1.86 Ga. The data permit us to construct an apparent polar wander path for the Indian shield for an ~ 600 Ma interval of the Palaeoproterozoic eon (2.45-1.85 Ga). Testing and evaluation of continental reconstructions for this interval, which are mostly based on geological correlations, reveal many inconsistencies. Between 2.45 and 2.37 Ga, the Indian shield was situated at higher latitudes similar to the Yilgarn craton of Australia. It was subsequently located near the equator at 2.22, 2.18, 1.99 and 1.86 Ga. Thus, an India-Australia connection is supported during these times, but a proposed Australia-Kaapvaal link in "Zimvaalbara" and a Dharwar (India)-Slave connection in "Sclavia" or a Superior-Zimbabwe-India connection in "Superia" are inconsistent with Indian data. In addition, the close palaeomagnetic comparison between the Palaeoproterozoic dykes of Dharwar

Magnetic and superconducting competition within the Hubbard dimer. Exact solution

NASA Astrophysics Data System (ADS)

Matlak, M.; Somska, T.; Grabiec, B.

2005-02-01

We express the Hubbard dimer Hamiltonian in the second quantization with theuse of the Hubbard and spin operators. We consider the case of positive and negative U. We decompose the resulting Hamiltonian into several parts collecting all the terms belonging to the same energy level. Such a decomposition visualizes explicitely all intrinsic interactions competing together and deeply hidden in the original form of the dimer Hamiltonian. Among them are competitive ferromagnetic and antiferromagnetic interactions. There are also hopping terms present which describe Cooper pairs hopping between sites 1 and 2 with positive and negative coupling constants (similar as in Kulik-Pedan, Penson-Kolb models). We show that the competition between intrinsic interactions strongly depends on the model parametrs and the averaged occupation number of electrons n [0, 4] resulting in different regimes of the model (as e.g. t-J model regime, etc.).

A Riemann-Hilbert formulation for the finite temperature Hubbard model

NASA Astrophysics Data System (ADS)

Cavaglià, Andrea; Cornagliotto, Martina; Mattelliano, Massimo; Tateo, Roberto

2015-06-01

Inspired by recent results in the context of AdS/CFT integrability, we reconsider the Thermodynamic Bethe Ansatz equations describing the 1D fermionic Hubbard model at finite temperature. We prove that the infinite set of TBA equations are equivalent to a simple nonlinear Riemann-Hilbert problem for a finite number of unknown functions. The latter can be transformed into a set of three coupled nonlinear integral equations defined over a finite support, which can be easily solved numerically. We discuss the emergence of an exact Bethe Ansatz and the link between the TBA approach and the results by Jüttner, Klümper and Suzuki based on the Quantum Transfer Matrix method. We also comment on the analytic continuation mechanism leading to excited states and on the mirror equations describing the finite-size Hubbard model with twisted boundary conditions.

Dykes and structures of the NE rift of Tenerife, Canary Islands: a record of stabilisation and destabilisation of ocean island rift zones

NASA Astrophysics Data System (ADS)

Delcamp, A.; Troll, V. R.; van Wyk de Vries, B.; Carracedo, J. C.; Petronis, M. S.; Pérez-Torrado, F. J.; Deegan, F. M.

2012-07-01

Many oceanic island rift zones are associated with lateral sector collapses, and several models have been proposed to explain this link. The North-East Rift Zone (NERZ) of Tenerife Island, Spain offers an opportunity to explore this relationship, as three successive collapses are located on both sides of the rift. We have carried out a systematic and detailed mapping campaign on the rift zone, including analysis of about 400 dykes. We recorded dyke morphology, thickness, composition, internal textural features and orientation to provide a catalogue of the characteristics of rift zone dykes. Dykes were intruded along the rift, but also radiate from several nodes along the rift and form en échelon sets along the walls of collapse scars. A striking characteristic of the dykes along the collapse scars is that they dip away from rift or embayment axes and are oblique to the collapse walls. This dyke pattern is consistent with the lateral spreading of the sectors long before the collapse events. The slump sides would create the necessary strike-slip movement to promote en échelon dyke patterns. The spreading flank would probably involve a basal decollement. Lateral flank spreading could have been generated by the intense intrusive activity along the rift but sectorial spreading in turn focused intrusive activity and allowed the development of deep intra-volcanic intrusive complexes. With continued magma supply, spreading caused temporary stabilisation of the rift by reducing slopes and relaxing stress. However, as magmatic intrusion persisted, a critical point was reached, beyond which further intrusion led to large-scale flank failure and sector collapse. During the early stages of growth, the rift could have been influenced by regional stress/strain fields and by pre-existing oceanic structures, but its later and mature development probably depended largely on the local volcanic and magmatic stress/strain fields that are effectively controlled by the rift zone growth

Elemental and Sr-Nd-Pb isotope geochemistry of the Florianópolis Dyke Swarm (Paraná Magmatic Province): crustal contamination and mantle source constraints

NASA Astrophysics Data System (ADS)

Marques, L. S.; De Min, A.; Rocha-Júnior, E. R. V.; Babinski, M.; Bellieni, G.; Figueiredo, A. M. G.

2018-04-01

The Florianópolis Dyke Swarm is located in Santa Catarina Island, comprising also the adjacent continental area, and belongs to the Paraná Magmatic Province (PMP). The dyke outcrops in the island are 0.1-70 m thick and most of them are coast-parallel (NE-SW trending), with subordinate NW-SE trending. The vast majority of the dykes has SiO2 varying from 50 to 55 wt% and relatively high-Ti (TiO2 > 3 wt%) contents and these rocks were divided using the criteria commonly used to distinguish the different magma-types identified in the volcanic rocks from the PMP. The Urubici dykes (Sr > 550 μg/g) are the most abundant and some of them experienced crustal contamination reaching to 10%, as evidenced by low P2O5/K2O (0.30-0.21), high (Rb/Ba)PM (1.0-2.2), and radiogenic Sr and Pb isotope compositions (87Sr/86Sri up to 0.70716 (back to 125 Ma) and 206Pb/204Pbm up to 19.093). The Pitanga (Sr < 550 μg/g) and the basaltic trachyandesite dykes are less abundant and almost all of them were also substantially affected by at least 15% of crustal assimilation, evidenced by high (Rb/Ba)PM (up to 2.6) and Sr (87Sr/86Sri = 0.70737-0.71758) and Pb (206Pb/204Pbm = 18.446-19.441) isotope ratios, as well as low P2O5/K2O values (0.30-0.18). The low-Ti (TiO2 < 2 wt%) dykes are scarce and show a large compositional variability (SiO2: 50.4-64.5 wt%), with similar geochemical characteristics of the low-Ti volcanic rocks (Gramado-Palmas) from southern PMP, although the most primitive dykes show hybrid characteristics of Ribeira and Esmeralda magmas. The presence of granitic xenoliths with border reactions and dykes with diffuse contacts indicate that crustal contamination probably occurred by assimilation from re-melted the host rocks. Considering only the high-Ti Urubici dykes that were not affected by crustal contamination, the Sr, Nd and Pb isotope mixing modelling indicates the participation of a heterogeneous metasomatized (refertilized) subcontinental lithospheric mantle (SCLM). This

EXPERIMENTAL ACIDIFICATION OF A STREAM TRIBUTARY TO HUBBARD BROOK

EPA Science Inventory

Long (5 mo.) and short-term (1 h to 2 days) effects of acidic pH have been measured in a poorly buffered mountain stream within the Hubbard Brook Experimental Forest, New Hampshire. Over a 5-month period aluminum, calcium, magnesium, and potassium were mobilized into the stream w...

InSAR Observations of the 2009 Harrat Lunayyir (western Saudi Arabia) Dyke Intrusion and Post-Diking Deformation

NASA Astrophysics Data System (ADS)

Jónsson, Sigurjón; Lu, Zhong; Lundgren, Paul

2010-05-01

Interferometric Satellite Radar (InSAR) observations of one of the volcanic provinces in western Saudi Arabia, Harrat Lunayyir (also known as Harrat Al-Shaqah), provide rich information about the geometry and evolution of a dyke intrusion and surface faulting that occurred in the region in April-July 2009. The first sign of activity was the start of a seismic swarm on 24 April that steadily intensified until six magnitude 4.6-5.7 earthquakes struck on 17-20 May. More than 30000 people were evacuated from the area following the activity in mid-May and stayed in the neighboring cities of Yanbu and Medina for several weeks. During the intensive activity in mid-May we sent a request for emergency satellite radar data acquisitions to the European Space Agency and later activated an International Charter to guarantee satellite data collection of the area. We have analyzed a number of Envisat, ALOS, and TerraSAR-X interferograms of the area and the results are outstanding, owing to the stable and vegetation-free surface conditions. Interferograms spanning the main seismic activity in mid-May exhibit strong deformation that extends across a large 40 km × 40 km area, with broad uplift and over a meter of WSW-ENE extension. In addition, the data show clear signs of surface faulting and graben-like subsidence in the middle of the deformed area with the graben subsidence exceeding 50 cm. Modeling of deformation strongly suggests that a near-vertical dyke intruded with a WNW-ESE orientation, parallel to the Red Sea, and that the intruded volume is ~0.13 km3. The dyke intrusion appears to have triggered faulting on graben-bounding and inward-dipping normal faults. The shallowest part of the dyke seems to have reached within only 2 km of the surface, right below where the graben is the narrowest and under an area with a number of cinder cones from previous volcanic events. While the day-to-day temporal evolution of the deformation cannot be derived from the InSAR data, the

Laser spectroscopic probing of coexisting superfluid and insulating states of an atomic Bose–Hubbard system

PubMed Central

Kato, Shinya; Inaba, Kensuke; Sugawa, Seiji; Shibata, Kosuke; Yamamoto, Ryuta; Yamashita, Makoto; Takahashi, Yoshiro

2016-01-01

A system of ultracold atoms in an optical lattice has been regarded as an ideal quantum simulator for a Hubbard model with extremely high controllability of the system parameters. While making use of the controllability, a comprehensive measurement across the weakly to strongly interacting regimes in the Hubbard model to discuss the quantum many-body state is still limited. Here we observe a great change in the excitation energy spectra across the two regimes in an atomic Bose–Hubbard system by using a spectroscopic technique, which can resolve the site occupancy in the lattice. By quantitatively comparing the observed spectra and numerical simulations based on sum rule relations and a binary fluid treatment under a finite temperature Gutzwiller approximation, we show that the spectra reflect the coexistence of a delocalized superfluid state and a localized insulating state across the two regimes. PMID:27094083

14. Cortlandt V.D. Hubbard, Photographer November 1967 DETAIL: ORCHESTRA SECTION ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

14. Cortlandt V.D. Hubbard, Photographer November 1967 DETAIL: ORCHESTRA SECTION AND TIERS SHOWING DECORATED COLUMNS, BRACKETS, MOLDINGS - American Academy of Music, 232-246 South Broad Street, Philadelphia, Philadelphia County, PA

Rationalization of Hubbard U in CeOx from first principles: Unveiling the role of local structure in screening

NASA Astrophysics Data System (ADS)

Lu, Deyu; Liu, Ping

2014-03-01

DFT+U method has been widely employed in theoretical studies on various ceria systems to correct the delocalization bias in local and semi-local DFT functionals with moderate computational cost. To rationalize the Hubbard U of Ce 4f, we employed the first principles linear response method to compute Hubbard U for Ce in ceria clusters, bulks, and surfaces. We found that in contrast to the commonly used approach treating U as a constant, the Hubbard U varies in a wide range from 4.1 eV to 6.7 eV, and exhibits a strong correlation with the Ce coordination numbers and Ce-O bond lengths, rather than the Ce 4f valence state. The variation of the Hubbard U can be explained by the changes in the strength of local screening due to O --> Ce intersite transition. Our study represents a systematic, quantitative investigation of the relationship between the Hubbard U and the local atomic arrangement, enabling a DFT+environment-dependent U scheme that can have potential impact on catalysis research of strongly correlated systems. This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.

A new classification system for lesbians: the Dyke Diagnostic Manual.

PubMed

Eliason, Michele J

2010-01-01

There has been a long-standing need for a diagnostic manual that documents the unique pathological behaviors of lesbians. The Dyke Diagnostic Manual (DDM) is meant to supplement mainstream classification systems used to identify problematic behaviors in heterosexuals. This article presents thirteen uniquely lesbian conditions that are nowhere to be found in heterosexist diagnostic systems. The DDM may help to reduce the pain and suffering found in many lesbian relationships where one or both partners are afflicted.

Interagency partnership to assess and restore a degraded urban riverine wetland: Dyke Marsh Wildlife Preserve, Virginia

USGS Publications Warehouse

Steury, Brent W.; Litwin, Ronald J.; Oberg, Erik T.; Smoot, Joseph P.; Pavich, Milan J.; Sanders, Geoffrey; Santucci, Vincent L.

2014-01-01

The narrow-leaved cattail wetland known as Dyke Marsh formally became a land holding of George Washington Memorial Parkway (GWMP, a unit of the national park system) in 1959, along with a congressional directive to honor a newly-let 30-year commercial sand and gravel dredge-mining lease at the site. Dredging continued until 1974 when Public Law 93-251 called for the National Park Service and the United States Army Corps of Engineers to “implement restoration of the historical and ecological values of Dyke Marsh.” By that time, about 83 acres of the marsh remained, and no congressional funding accompanied the passage of the law to effect any immediate conservation or restoration. Decades of dredge mining had severely altered the surface area of Dyke Marsh, the extent of its tidal creek system, and the shallow river bottom of the Potomac River abutting the marsh. Further, mining destabilized the marsh, causing persistent erosion, shoreline retreat, and tidal channel widening after mining ceased. Erosion has continued unchecked until the present; approximately 50 acres of the original marsh are now estimated to remain. The specific cause of persistent erosion had been unknown prior to this collaborative study but previously was assumed to be due to flooding by the Potomac River.

Doping evolution of charge and spin excitations in two-leg Hubbard ladders: Comparing DMRG and FLEX results [Doping evolution of charge and spin excitations in two-leg Hubbard ladders: Comparing DMRG and RPA+FLEX results

DOE PAGES

Nocera, Alberto; Wang, Yan; Patel, Niravkumar D.; ...

2018-05-31

Here, we study the magnetic and charge dynamical response of a Hubbard model in a two-leg ladder geometry using the density matrix renormalization group (DMRG) method and the random phase approximation within the fluctuation-exchange approximation (FLEX). Our calculations reveal that FLEX can capture the main features of the magnetic response from weak up to intermediate Hubbard repulsion for doped ladders, when compared with the numerically exact DMRG results. However, while at weak Hubbard repulsion both the spin and charge spectra can be understood in terms of weakly interacting electron-hole excitations across the Fermi surface, at intermediate coupling DMRG shows gappedmore » spin excitations at large momentum transfer that remain gapless within the FLEX approximation. For the charge response, FLEX can only reproduce the main features of the DMRG spectra at weak coupling and high doping levels, while it shows an incoherent character away from this limit. Overall, our analysis shows that FLEX works surprisingly well for spin excitations at weak and intermediate Hubbard U values even in the difficult low-dimensional geometry such as a two-leg ladder. Finally, we discuss the implications of our results for neutron scattering and resonant inelastic x-ray scattering experiments on two-leg ladder cuprate compounds.« less

Doping evolution of charge and spin excitations in two-leg Hubbard ladders: Comparing DMRG and FLEX results [Doping evolution of charge and spin excitations in two-leg Hubbard ladders: Comparing DMRG and RPA+FLEX results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nocera, Alberto; Wang, Yan; Patel, Niravkumar D.

Here, we study the magnetic and charge dynamical response of a Hubbard model in a two-leg ladder geometry using the density matrix renormalization group (DMRG) method and the random phase approximation within the fluctuation-exchange approximation (FLEX). Our calculations reveal that FLEX can capture the main features of the magnetic response from weak up to intermediate Hubbard repulsion for doped ladders, when compared with the numerically exact DMRG results. However, while at weak Hubbard repulsion both the spin and charge spectra can be understood in terms of weakly interacting electron-hole excitations across the Fermi surface, at intermediate coupling DMRG shows gappedmore » spin excitations at large momentum transfer that remain gapless within the FLEX approximation. For the charge response, FLEX can only reproduce the main features of the DMRG spectra at weak coupling and high doping levels, while it shows an incoherent character away from this limit. Overall, our analysis shows that FLEX works surprisingly well for spin excitations at weak and intermediate Hubbard U values even in the difficult low-dimensional geometry such as a two-leg ladder. Finally, we discuss the implications of our results for neutron scattering and resonant inelastic x-ray scattering experiments on two-leg ladder cuprate compounds.« less

Absolute Geomagnetic Paleointensity as Recorded by Mafic Dykes of the ~1.98 Ga Bundelkhand Swarm and ~0.75 Ga Malani Igneous Suite from Northern India

NASA Astrophysics Data System (ADS)

Piispa, E. J.; Smirnov, A. V.; Pandit, M. K.

2012-12-01

Determining the long-term behavior and configuration of the Precambrian geomagnetic field is crucial for understanding the origin and nature of Earth's early geodynamo. However, our knowledge about strength and morphology of the Precambrian geomagnetic field is extremely limited due to paucity of reliable data on the ancient field strength (paleointensity). Information correlating the strength and characteristics of Earth's ancient geomagnetic field can be gained by measuring the paleodirectional and paleointensity properties of Precambrian rocks. We investigated two Proterozoic mafic dyke swarms from the Indian subcontinent: the extensive NW-SE trending 1979±8 Ma (U-Pb) dyke swarm in the Bundelkhand craton and the N-S trending Malani mafic dyke swarm, the latter representing the third and final phase of magmatism in the Malani Igneous Suite. Malani rhyolites have been precisely dated at 771±2 to 751±3 Ma (U - Pb zircon ages). The Malani mafic dykes have been correlated with the ~750 Ma dolerite dykes of Seychelles based on geological and geochemical criteria. The mafic dykes of both studied swarms are vertical to sub-vertical and show little or no evidence of alteration. Detailed paleomagnetic studies, using both thermal and alternating field demagnetization, revealed the presence of stable dual-polarity magnetic component for both dyke swarms. The primary nature of the magnetization is supported by positive baked contact tests. Typically, the characteristic magnetization is single component with narrow unblocking temperature spectra between ~500°C and 550-570°C, with remanence carried by small PSD magnetite or low-Ti titanomagnetite. Absolute paleointensities of these dyke swarms were obtained by two different heating based methods: multiple specimen domain-state corrected (MSP-DSC) and Thellier double heating method with alternating infield-zerofield (IZ) and zerofield-infield (ZI) steps. The multiple sample protocol incorporated checks for alteration

Methodes d'amas quantiques a temperature finie appliquees au modele de Hubbard

NASA Astrophysics Data System (ADS)

Plouffe, Dany

Depuis leur decouverte dans les annees 80, les supraconducteurs a haute temperature critique ont suscite beaucoup d'interet en physique du solide. Comprendre l'origine des phases observees dans ces materiaux, telle la supraconductivite, est l'un des grands defis de la physique theorique du solide des 25 dernieres annees. L'un des mecanismes pressentis pour expliquer ces phenomenes est la forte interaction electron-electron. Le modele de Hubbard est l'un des modeles les plus simples pour tenir compte de ces interactions. Malgre la simplicite apparente de ce modele, certaines de ses caracteristiques, dont son diagramme de phase, ne sont toujours pas bien etablies, et ce malgre plusieurs avancements theoriques dans les dernieres annees. Cette etude se consacre a faire une analyse de methodes numeriques permettant de calculer diverses proprietes du modele de Hubbard en fonction de la temperature. Nous decrivons des methodes (la VCA et la CPT) qui permettent de calculer approximativement la fonction de Green a temperature finie sur un systeme infini a partir de la fonction de Green calculee sur un amas de taille finie. Pour calculer ces fonctions de Green, nous allons utiliser des methodes permettant de reduire considerablement les efforts numeriques necessaires pour les calculs des moyennes thermodynamiques, en reduisant considerablement l'espace des etats a considerer dans ces moyennes. Bien que cette etude vise d'abord a developper des methodes d'amas pour resoudre le modele de Hubbard a temperature finie de facon generale ainsi qu'a etudier les proprietes de base de ce modele, nous allons l'appliquer a des conditions qui s'approchent de supraconducteurs a haute temperature critique. Les methodes presentees dans cette etude permettent de tracer un diagramme de phase pour l'antiferromagnetisme et la supraconductivite qui presentent plusieurs similarites avec celui des supraconducteurs a haute temperature. Mots-cles : modele de Hubbard, thermodynamique

Formation and Origin of Metabreccia from the Parkin Offset Dyke at the Sudbury Impact Structure

NASA Astrophysics Data System (ADS)

Anders, D.; Osinski, G. R.; Grieve, R. A. F.; Péntek, A.

2015-09-01

Metabreccia is an important litholgy of the Offset Dykes of the Sudbury impact structure, however, its formation and origin is still topic of discussion. Here we present evidence that Metabreccia is a metamorphosed Footwall Breccia.

Measurement of the Equation of State of the Two-Dimensional Hubbard Model

NASA Astrophysics Data System (ADS)

Miller, Luke; Cocchi, Eugenio; Drewes, Jan; Koschorreck, Marco; Pertot, Daniel; Brennecke, Ferdinand; Koehl, Michael

2016-05-01

The subtle interplay between kinetic energy, interactions and dimensionality challenges our comprehension of strongly-correlated physics observed, for example, in the solid state. In this quest, the Hubbard model has emerged as a conceptually simple, yet rich model describing such physics. Here we present an experimental determination of the equation of state of the repulsive two-dimensional Hubbard model over a broad range of interactions, 0 <= U / t <= 20 , and temperatures, down to kB T / t = 0 . 63(2) using high-resolution imaging of ultracold fermionic atoms in optical lattices. We show density profiles, compressibilities and double occupancies over the whole doping range, and hence our results constitute benchmarks for state-of-the-art theoretical approaches.

Temporal correlation between dyke swarms and crustal extension in the middle Palaeozoic Vilyui rift basin, Siberian platform

NASA Astrophysics Data System (ADS)

Polyansky, Oleg P.; Prokopiev, Andrei V.; Koroleva, Olga V.; Tomshin, Mikhail D.; Reverdatto, Vladimir V.; Selyatitsky, Alexander Yu.; Travin, Alexei V.; Vasiliev, Dmitry A.

2017-06-01

This paper presents results from new 40Ar/39Ar isotope dating of nine mafic dykes from three large dyke swarms (Vilyui-Markha, Kontai-Dzherba, and Chara-Sinsk) of the Yakutsk-Vilyui large igneous province (LIP), in addition to a reconstruction of the subsidence history of the middle Palaeozoic Vilyui paleorift basin (eastern Siberian platform). All previously published 40Ar/39Ar and U-Pb dates are summarized. Statistical analysis of the dyke ages reveals repeated magmatic events in the study area. Two major pulses of mafic magmatism are identified: one at the Frasnian-Famennian boundary, with a main peak at ca. 374.1 Ma, and another in the latest Devonian with a peak at ca. 363.4 Ma. The time of maximum intensity of dyke intrusion coincides (within uncertainty) with rapid subsidence in the Vilyui basin. The minimum total volume of middle Palaeozoic magmatism produced in the Yakutsk-Vilyui LIP is 100-215 K km3, which is much less than earlier estimates. Most of the mafic material within the Yakutsk-Vilyui LIP is related to the Vilyui basin and associated dyke swarms. Backstripping analysis of sedimentation in depressions of the Vilyui basin was carried out. Estimates were obtained for the spatial distribution of the stretching factor of the crust and mantle lithosphere, averaging 1.17 and 1.44, respectively. The amount of extension due to dyke intrusion is estimated to be 6%. Backstripping analysis of sedimentation in the Vilyui basin was used to assess the effect of both intraplate far-field forces and upwelling magma flows initiated by a mantle plume. A numerical thermomechanical model was developed to investigate the relations between two possible mechanisms by which the Vilyui rift was initiated: intraplate extension (passive rifting) and the ascent of a mantle magmatic diapir (active rifting). A model considering both of these mechanisms shows the contribution of the far-field extension forces and the effect of convective flows around the mantle plume, assuming

Effective Hubbard model for Helium atoms adsorbed on a graphite

NASA Astrophysics Data System (ADS)

Motoyama, Yuichi; Masaki-Kato, Akiko; Kawashima, Naoki

Helium atoms adsorbed on a graphite is a two-dimensional strongly correlated quantum system and it has been an attractive subject of research for a long time. A helium atom feels Lennard-Jones like potential (Aziz potential) from another one and corrugated potential from the graphite. Therefore, this system may be described by a hardcore Bose Hubbard model with the nearest neighbor repulsion on the triangular lattice, which is the dual lattice of the honeycomb lattice formed by carbons. A Hubbard model is easier to simulate than the original problem in continuous space, but we need to know the model parameters of the effective model, hopping constant t and interaction V. In this presentation, we will present an estimation of the model parameters from ab initio quantum Monte Carlo calculation in continuous space in addition to results of quantum Monte Carlo simulation for an obtained discrete model.

Antiferromagnetism and DX2-Y2-WAVE Pairing in the Colored Hubbard Model

NASA Astrophysics Data System (ADS)

Baier, Tobias; Bick, Eike

2001-08-01

We introduce a new formulation of the 2d Hubbard model on a square lattice (the "colored" Hubbard model). In this formulation interesting physical nonlocal properties as antiferromagnetic or dx2-y2-wave superconducting behavior are included in an explicit way. Analyzing the phase diagram in a mean field approximation numerically, we show that our approach yields results which are in qualitative agreement with experiment.

3. Historic American Buildings Survey Cortlandt V. D. Hubbard, Photographer ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

3. Historic American Buildings Survey Cortlandt V. D. Hubbard, Photographer July 1966 SOUTH AND EAST (STREET) ELEVATIONS (NOTE: Chimney in gable hidden by tree at left, windows of fourth bay hidden by tree at right) - Thomas Starbuck Homestead, 11 Milk Street, Nantucket, Nantucket County, MA

2. Historic American Buildings Survey Cortlandt V. D. Hubbard, Photographer ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. Historic American Buildings Survey Cortlandt V. D. Hubbard, Photographer July 1966 SOUTH AND EAST (STREET) ELEVATIONS (NOTE: Chimney in gable hidden by tree at left, windows of fourth bay hidden by tree at right) - Thomas Starbuck Homestead, 11 Milk Street, Nantucket, Nantucket County, MA

Timing, mantle source and origin of mafic dykes within the gravity anomaly belt of the Taihang-Da Hinggan gravity lineament, central North China Craton

NASA Astrophysics Data System (ADS)

Liu, Shen; Feng, Caixia; Feng, Guangying; Xu, Mengjing; Coulson, Ian M.; Guo, Xiaolei; Guo, Zhuang; Peng, Hao; Feng, Qiang

2017-09-01

Six mafic dyke swarms crop out in Hebei Province within the Taihang-Da Hinggan gravity lineament magmatic belt, China, and were sampled. Here, we present new zircon laser ablation-inductively coupled plasma-mass spectrometry U-Pb age, whole rock geochemical, and Sr-Nd-Pb-Hf isotopic data for the six areas where these mafic dykes occur. The mafic (dolerite) dykes formed between 131.6 ± 1.6 and 121.6 ± 1.1 Ma, and are enriched in the light rare earth elements (LREE), some of the large ion lithophile elements (LILE; e.g., Rb, Ba, and Sr) and Pb, and are depleted in Th, U, Nb and Ta; some samples are also depleted in Eu. The dykes have high initial 87Sr/86Sr ratios (0.7055-0.7057), negative εNd (t) values (-12.5 to -11.9), relatively constant Pb isotopic ratios ((206Pb/204Pb)i = 16.45-16.51, (207Pb/204Pb)i = 15.44-15.51, (208Pb/204Pb)i = 36.49-36.53), negative εHf (t) values (-18.2 to -15.1), and old Nd (TNdDM2; 2.17-2.47 Ga) and Hf (THfDM2; 2.28-2.33 Ga) model ages. These geochronological, geochemical, and isotopic data indicate that the dykes were derived from magmas generated by low to moderate degree partial melting (1.0%-10%) of an EM1-like garnet lherzolite mantle source; these magmas fractionated olivine, clinopyroxene, and hornblende prior to emplacement, and assimilated minimal amounts of crustal material. Several possible models have previously been proposed to explain the origin of Mesozoic magmatism in this region. However, here we propose a foundering model for these studied mafic dykes, involving the foundering of eclogite from thickened lower crust due to the collision between the Siberian Craton and the North China Craon.

Magma-maintained rift segmentation at continental rupture in the 2005 Afar dyking episode.

PubMed

Wright, Tim J; Ebinger, Cindy; Biggs, Juliet; Ayele, Atalay; Yirgu, Gezahegn; Keir, Derek; Stork, Anna

2006-07-20

Seafloor spreading centres show a regular along-axis segmentation thought to be produced by a segmented magma supply in the passively upwelling mantle. On the other hand, continental rifts are segmented by large offset normal faults, and many lack magmatism. It is unclear how, when and where the ubiquitous segmented melt zones are emplaced during the continental rupture process. Between 14 September and 4 October 2005, 163 earthquakes (magnitudes greater than 3.9) and a volcanic eruption occurred within the approximately 60-km-long Dabbahu magmatic segment of the Afar rift, a nascent seafloor spreading centre in stretched continental lithosphere. Here we present a three-dimensional deformation field for the Dabbahu rifting episode derived from satellite radar data, which shows that the entire segment ruptured, making it the largest to have occurred on land in the era of satellite geodesy. Simple elastic modelling shows that the magmatic segment opened by up to 8 m, yet seismic rupture can account for only 8 per cent of the observed deformation. Magma was injected along a dyke between depths of 2 and 9 km, corresponding to a total intrusion volume of approximately 2.5 km3. Much of the magma appears to have originated from shallow chambers beneath Dabbahu and Gabho volcanoes at the northern end of the segment, where an explosive fissural eruption occurred on 26 September 2005. Although comparable in magnitude to the ten year (1975-84) Krafla events in Iceland, seismic data suggest that most of the Dabbahu dyke intrusion occurred in less than a week. Thus, magma intrusion via dyking, rather than segmented normal faulting, maintains and probably initiated the along-axis segmentation along this sector of the Nubia-Arabia plate boundary.

Magnetic excitation spectra of strongly correlated quasi-one-dimensional systems: Heisenberg versus Hubbard-like behavior

NASA Astrophysics Data System (ADS)

Nocera, A.; Patel, N. D.; Fernandez-Baca, J.; Dagotto, E.; Alvarez, G.

2016-11-01

We study the effects of charge degrees of freedom on the spin excitation dynamics in quasi-one-dimensional magnetic materials. Using the density matrix renormalization group method, we calculate the dynamical spin structure factor of the Hubbard model at half electronic filling on a chain and on a ladder geometry, and compare the results with those obtained using the Heisenberg model, where charge degrees of freedom are considered frozen. For both chains and two-leg ladders, we find that the Hubbard model spectrum qualitatively resembles the Heisenberg spectrum—with low-energy peaks resembling spinonic excitations—already at intermediate on-site repulsion as small as U /t ˜2 -3 , although ratios of peak intensities at different momenta continue evolving with increasing U /t converging only slowly to the Heisenberg limit. We discuss the implications of these results for neutron scattering experiments and we propose criteria to establish the values of U /t of quasi-one-dimensional systems described by one-orbital Hubbard models from experimental information.

Paleomagnetic study of 1765 Ma dyke swarm from the Singhbhum Craton: Implications to the paleogeography of India

NASA Astrophysics Data System (ADS)

Shankar, Ravi; Srinivasa Sarma, D.; Ramesh Babu, N.; Parashuramulu, V.

2018-05-01

We report the first key paleopole as a result of paleomagnetic study on a precisely dated 1765.3 ± 1.0 Ma WNW-ESE trending dyke swarm from Singhbhum Craton. This pole has been used in this study to propose the paleogeographic reconstruction of India with Baltica Craton and North China Craton. Incremental alternating field (AF) and thermal demagnetization, isolated high coercivity components with north to north-westerly declination and shallow negative inclination from 9 sampling sites which are representing different individual dykes. The primary origin of the ChRM is supported by the positive baked contact test. The WNW-ESE trending dykes yield a mean paleomagnetic direction with a declination = 329.2° and an inclination = -22.8° (k = 31.6; α95 = 9.3°). The positive bake contact test proves the primary nature of remanence. The pole position of Singhbhum Craton at 1765 Ma is 45°N, 311°E (dp = 5.2 and dm = 9.9). Paleogeographic reconstruction at ca. 1770 Ma, supported by geological, tectonic and metallogenic evidences indicate that the Baltica Craton and India linkage can be stable for at least ∼370 Ma (∼1770-1400 Ma). There is also reasonable evidence in support of India-North China Craton spatial proximity at ∼1770 Ma.

Palaeomagnetism of Precambrian dyke swarms in the North China Shield: The ˜1.8 Ga LIP event and crustal consolidation in late Palaeoproterozoic times

NASA Astrophysics Data System (ADS)

Piper, John D. A.; Jiasheng, Zhang; Huang, Baochung; Roberts, Andrew P.

2011-06-01

The North China Shield (NCS) is cut by a laterally-extensive dyke swarm emplaced at 1.78-1.76 Ga when an extensional regime succeeded regional metamorphism and completion of cratonisation by ˜1.85 Ga. Palaeomagnetic study of these dykes and adjoining metamorphic country rocks identifies a dominant shallow axis comprising a contiguous population with NE to N declinations and rare opposite polarity. Dykes with NE shallow magnetic declination (A1, D/ I = 36/-1°) recognised from previous study and emplaced in granulite terranes in the north are displaced by more northerly declinations (A2, D/ I = 8/2°) in lower grade metamorphic terranes to the south. Contact tests indicate a primary cooling-related origin to these magnetisations although tests are in part ambiguous because magnetisations in the granulite basement are comparable. Petrologic and rock magnetic considerations imply that magnetisation of the dykes occurred during uplift from depths as deep as 20 km following the peak of metamorphism at ˜1.85 Ga. A temporal migration A2 → A1 is implied by the higher crustal level and earlier acquisition of the former, and the deeper source and later acquisition of the latter. A third population of dyke magnetisations (A3, D/ I = 18/43°) is distributed towards steeper inclinations and close to the Mesozoic-Recent palaeofield. These are either partial or complete overprints of A1-A2 magnetisations with greater degrees of alteration indicated by demagnetisation and thermomagenetic spectra, or are much younger dykes of Mesozoic-Tertiary age. A minority fourth (later Precambrian but presently undated) dual polarity population has a magnetisation (11 dykes, D/ I = 108/7°) with contact tests indicating a primary cooling-related origin. The ˜1.78-1.76 Ga time of emplacement of the dominant dyke swarms in this study is widely represented by contemporaneous igneous rocks in other major shields linked to major Large Igneous Province (LIP)-related events. The new definition of

The energy spectrum and the optical absorption spectrum of C{sub 60} fullerene within the Hubbard model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silant’ev, A. V., E-mail: kvvant@rambler.ru

2015-10-15

Anticommutator Green’s functions and the energy spectrum of C{sub 60} fullerene are calculated in the approximation of static fluctuations within the Hubbard model. On the basis of this spectrum, an interpretation is proposed for the experimentally observed optical absorption bands of C{sub 60} fullerene. The parameters of C{sub 60} fullerene that characterize it within the Hubbard model are calculated by the optical absorption spectrum.

Hydrometeorological database for Hubbard Brook Experimental Forest: 1955-2000

Treesearch

Amey Schenck Bailey; James W. Hornbeck; John L. Campbell; Christopher Eagar

2003-01-01

The 3,160-ha Hubbard Brook Experimental Forest (HBEF) in New Hampshire has been a prime area of research on forest and stream ecosystems since its establishment by the USDA Forest Service in 1955. Streamflow and precipitation have been measured continuously on the HBEF, and long-term datasets exist for air and soil temperature, snow cover, soil frost, solar radiation,...

Dynamical Vertex Approximation for the Hubbard Model

NASA Astrophysics Data System (ADS)

Toschi, Alessandro

A full understanding of correlated electron systems in the physically relevant situations of three and two dimensions represents a challenge for the contemporary condensed matter theory. However, in the last years considerable progress has been achieved by means of increasingly more powerful quantum many-body algorithms, applied to the basic model for correlated electrons, the Hubbard Hamiltonian. Here, I will review the physics emerging from studies performed with the dynamical vertex approximation, which includes diagrammatic corrections to the local description of the dynamical mean field theory (DMFT). In particular, I will first discuss the phase diagram in three dimensions with a special focus on the commensurate and incommensurate magnetic phases, their (quantum) critical properties, and the impact of fluctuations on electronic lifetimes and spectral functions. In two dimensions, the effects of non-local fluctuations beyond DMFT grow enormously, determining the appearance of a low-temperature insulating behavior for all values of the interaction in the unfrustrated model: Here the prototypical features of the Mott-Hubbard metal-insulator transition, as well as the existence of magnetically ordered phases, are completely overwhelmed by antiferromagnetic fluctuations of exponentially large extension, in accordance with the Mermin-Wagner theorem. Eventually, by a fluctuation diagnostics analysis of cluster DMFT self-energies, the same magnetic fluctuations are identified as responsible for the pseudogap regime in the holed-doped frustrated case, with important implications for the theoretical modeling of the cuprate physics.

Potential Engineering of Fermi-Hubbard Systems using a Quantum Gas Microscope

NASA Astrophysics Data System (ADS)

Ji, Geoffrey; Mazurenko, Anton; Chiu, Christie; Parsons, Maxwell; Kanász-Nagy, Márton; Schmidt, Richard; Grusdt, Fabian; Demler, Eugene; Greif, Daniel; Greiner, Markus

2017-04-01

Arbitrary control of optical potentials has emerged as an important tool in manipulating ultracold atomic systems, especially when combined with the single-site addressing afforded by quantum gas microscopy. Already, experiments have used digital micromirror devices (DMDs) to initialize and control ultracold atomic systems in the context of studying quantum walks, quantum thermalization, and many-body localization. Here, we report on progress in using a DMD located in the image plane of a quantum gas microscope to explore static and dynamic properties of a 2D Fermi-Hubbard system. By projecting a large, ring-shaped anti-confining potential, we demonstrate entropy redistribution and controlled doping of the system. Moreover, we use the DMD to prepare localized holes, which upon release interact with and disrupt the surrounding spin environment. These techniques pave the way for controlled investigations of dynamics in the low-temperature phases of the Hubbard model.

Upper Triassic mafic dykes of Lake Nyos, Cameroon (West Africa) I: K-Ar age evidence within the context of Cameroon Line magmatism, and the tectonic significance

NASA Astrophysics Data System (ADS)

Aka, Festus Tongwa; Hasegawa, Takeshi; Nche, Linus Anye; Asaah, Asobo Nkengmatia Elvis; Mimba, Mumbfu Ernestine; Teitchou, Isidore; Ngwa, Caroline; Miyabuchi, Yasuo; Kobayashi, Tetsuo; Kankeu, Boniface; Yokoyama, Tetsuya; Tanyileke, Gregory; Ohba, Takeshi; Hell, Joseph Victor; Kusakabe, Minoru

2018-05-01

The hydrodynamic fragmentation that formed Lake Nyos in northwest Cameroon did not only make it the most unpopular lake in the world from a gas disaster perspective, it also opened a rare and formidable window through which much of the geology of Cameroon can be studied in a single locality. The Cambrian quartz monzonite cliff excavated by the maar-forming explosion and exposed in its northeastern shore is intruded by mafic dykes, two of which we dated. Even though close to one another, the dykes are different in composition. The alkaline dyke yields a slightly older (Carnian) K-Ar fedspar age of 231.1 ± 4.8 Ma, while the sub alkaline dyke yields an age of 224.8 ± 4.7 Ma (Norian). Based on radioisotopic age data available over the last 48 years (347 data) for the Cameroon Line magmatism comprising eruptives and volcano-plutonic complexes, the Nyos dykes are way older than the Cameroon Line, and even pre-date the Lower Cretaceous initiation of west Gondwana fragmentation in Equatorial Atlantic domain. They would therefore not have been directly linked to the formation of the Cameroon Line. Alternatively, they might be associated with the development of intra-continental rift systems in West Central Africa that pre-dated west Gondwana breakup to form the Atlantic Ocean.

Topological phase transition and the effect of Hubbard interactions on the one-dimensional topological Kondo insulator

NASA Astrophysics Data System (ADS)

Pillay, Jason C.; McCulloch, Ian P.

2018-05-01

The effect of a local Kondo coupling and Hubbard interaction on the topological phase of the one-dimensional topological Kondo insulator (TKI) is numerically investigated using the infinite matrix-product state density-matrix renormalization group algorithm. The ground state of the TKI is a symmetry-protected topological (SPT) phase protected by inversion symmetry. It is found that on its own, the Hubbard interaction that tends to force fermions into a one-charge per site order is insufficient to destroy the SPT phase. However, when the local Kondo Hamiltonian term that favors a topologically trivial ground state with a one-charge per site order is introduced, the Hubbard interaction assists in the destruction of the SPT phase. This topological phase transition occurs in the charge sector where the correlation length of the charge excitation diverges while the correlation length of the spin excitation remains finite. The critical exponents, central charge, and the phase diagram separating the SPT phase from the topologically trivial phase are presented.

Magnetic excitation spectra of strongly correlated quasi-one-dimensional systems: Heisenberg versus Hubbard-like behavior

DOE PAGES

Nocera, Alberto; Patel, Niravkumar D.; Fernandez-Baca, Jaime A.; ...

2016-11-28

In this paper, we study the effects of charge degrees of freedom on the spin excitation dynamics in quasi-one-dimensional magnetic materials. Using the density matrix renormalization group method, we calculate the dynamical spin structure factor of the Hubbard model at half electronic filling on a chain and on a ladder geometry, and compare the results with those obtained using the Heisenberg model, where charge degrees of freedom are considered frozen. For both chains and two-leg ladders, we find that the Hubbard model spectrum qualitatively resembles the Heisenberg spectrum—with low-energy peaks resembling spinonic excitations—already at intermediate on-site repulsion as small asmore » U/t ~ 2–3, although ratios of peak intensities at different momenta continue evolving with increasing U/t converging only slowly to the Heisenberg limit. Finally, we discuss the implications of these results for neutron scattering experiments and we propose criteria to establish the values of U/t of quasi-one-dimensional systems described by one-orbital Hubbard models from experimental information.« less

Magnetic excitation spectra of strongly correlated quasi-one-dimensional systems: Heisenberg versus Hubbard-like behavior

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nocera, Alberto; Patel, Niravkumar D.; Fernandez-Baca, Jaime A.

In this paper, we study the effects of charge degrees of freedom on the spin excitation dynamics in quasi-one-dimensional magnetic materials. Using the density matrix renormalization group method, we calculate the dynamical spin structure factor of the Hubbard model at half electronic filling on a chain and on a ladder geometry, and compare the results with those obtained using the Heisenberg model, where charge degrees of freedom are considered frozen. For both chains and two-leg ladders, we find that the Hubbard model spectrum qualitatively resembles the Heisenberg spectrum—with low-energy peaks resembling spinonic excitations—already at intermediate on-site repulsion as small asmore » U/t ~ 2–3, although ratios of peak intensities at different momenta continue evolving with increasing U/t converging only slowly to the Heisenberg limit. Finally, we discuss the implications of these results for neutron scattering experiments and we propose criteria to establish the values of U/t of quasi-one-dimensional systems described by one-orbital Hubbard models from experimental information.« less

Integration of geotechnical and geophysical techniques for the characterization of a small earth-filled canal dyke and the localization of water leakage

NASA Astrophysics Data System (ADS)

Bièvre, Grégory; Lacroix, Pascal; Oxarango, Laurent; Goutaland, David; Monnot, Guy; Fargier, Yannick

2017-04-01

This paper investigates the combined use of extensive geotechnical, hydrogeological and geophysical techniques to assess a small earth dyke with a permanent hydraulic head, namely a canal embankment. The experimental site was chosen because of known issues regarding internal erosion and piping phenomena. Two leakages were visually located following the emptying of the canal prior to remediation works. The results showed a good agreement between the geophysical imaging techniques (Electrical Resistivity Tomography, P- and SH-waves Tomography) and the geotechnical data to detect the depth to the bedrock and its lateral variations. It appeared that surface waves might not be fully adapted for dyke investigation because of the particular geometry of the studied dyke, non-respectful of the 1D assumption, and which induced depth and velocity discrepancies retrieved from Rayleigh and Love waves inversion. The use of these classical prospecting techniques however did not allow to directly locate the two leakages within the studied earth dyke. The analysis of ambient vibration time series with a modified beam-forming algorithm allowed to localize the most energetic water flow prior to remediation works. It was not possible to detect the leakage after remediation works, suggesting that they efficiently contributed to significantly reduce the water flow. The second leakage was not detected probably because of a non-turbulent water flow, generating few energetic vibrations.

Staff - Trent D. Hubbard | Alaska Division of Geological & Geophysical

Science.gov Websites

, R.P., Darrow, M.M., and Hubbard, T.D., 2015, Influence of catchment properties on stability of frozen : Evaluating geologic hazards and the distribution and character of geologic materials on Alaska's North Slope Professor, Department of Biology and Earth Sciences, University of Central Missouri, Warrensburg, MO 2003

Dissipative preparation of antiferromagnetic order in the Fermi-Hubbard model

NASA Astrophysics Data System (ADS)

Kaczmarczyk, J.; Weimer, H.; Lemeshko, M.

2016-09-01

The Fermi-Hubbard model is one of the key models of condensed matter physics, which holds a potential for explaining the mystery of high-temperature superconductivity. Recent progress in ultracold atoms in optical lattices has paved the way to studying the model’s phase diagram using the tools of quantum simulation, which emerged as a promising alternative to the numerical calculations plagued by the infamous sign problem. However, the temperatures achieved using elaborate laser cooling protocols so far have been too high to show the appearance of antiferromagnetic (AF) and superconducting quantum phases directly. In this work, we demonstrate that using the machinery of dissipative quantum state engineering, one can observe the emergence of the AF order in the Fermi-Hubbard model with fermions in optical lattices. The core of the approach is to add incoherent laser scattering in such a way that the AF state emerges as the dark state of the driven-dissipative dynamics. The proposed controlled dissipation channels described in this work are straightforward to add to already existing experimental setups.

Satellite-based observations of unexpected coastal changes due to the Saemangeum Dyke construction, Korea.

PubMed

Lee, Yoon-Kyung; Ryu, Joo-Hyung; Choi, Jong-Kuk; Lee, Seok; Woo, Han-Jun

2015-08-15

Spatial and temporal changes around an area of conventional coastal engineering can be easily observed from field surveys because of the clear cause-and-effect observable in the before and after stages of the project. However, it is more difficult to determine environmental changes in the vicinity of tidal flats and coastal areas that are a considerable distance from the project. To identify any unexpected environmental impacts of the construction of Saemangeum Dyke in the area, we examined morphological changes identified by satellite-based observations through a field survey on Gomso Bay tidal flats (15km from Saemangeum Dyke), and changes in the suspended sediment distribution identified by satellite-based observations through a hydrodynamic analysis in the Saemangeum and Gomso coastal area. We argue that hydrodynamic changes due to conventional coastal engineering can affect the sedimentation pattern in the vicinity of tidal flats. We suggest that the environmental impact assessment conducted before a conventional coastal engineering project should include a larger area than is currently considered. Copyright © 2015 Elsevier Ltd. All rights reserved.

REE investigation of the Motru Dyke System components from the Danubian basements (South Carpathians, Romania)

NASA Astrophysics Data System (ADS)

Campeanu, Mara; Balica, Constantin; Balintoni, Ioan; Tănăselia, Claudiu; Cadar, Oana

2017-04-01

Dragsan and Lainici-Paius groups represent the basement components of the Danubian Alpine units (South Carpathians, Romania), which consist of medium-grade metamorphic rocks. A subvolcanic system of dykes (i.e. Motru Dyke System - MDS) crosscut mostly the Lainici Paius basement as an effect of a late-Variscan termo-tectonic event. The geochemical features, frame the MDS components within a wide range of petrotypes (basaltic andesites to rhyolites), and define a wide differentiation series. Classically this subvolcanic system was inferred to be in connection to a unique mantle source [1], however, recent studies [2,3] suggest a mixed mantle-crust source, based on the interpretation of the trace elements in conjunction with Sr and Nd isotope data. Aditionally, the presence of relict zircon grains consolidates this assumption. New REE data collected from eight MDS components, generally confirm the mixed mantle-crust source hypothesis. The distribution patterns reveal two groups of samples. The first group (six samples) is moderately enriched in REE and shows moderately fractionated patterns with (La/Yb)N between 7-21 and low Eu/Eu* (0.81-0.9). The second group, strongly enriched in light REE, have high (La/Yb)N and strong negative Eu anomaly (Eu/Eu* of 0.41 and 0.38 respectively). REE vary between 107-147 ppm for the first group and 612 ppm - 907ppm for the second group. We can assume a stronger fractionation of plagioclase as well as of garnet and amphibole for the second group. With a flatter pattern, for the first group of samples, the fractionation of these minerals appears to be moderate. The emplacement age of MDS has been long disputed, since it was supposed as pre-Silurian for a long time. However, newly zircon U/Pb isotopic dating performed on two collected samples indicate a mean age of 300 My [2,3]. Owing to the croscutting relationships with the post-colisional granitoid plutons emplaced in the Danubian basement during the late Variscan, and based on

Clinopyroxenite dykes within a banded unit in the basal mantle section of the northern part of the Oman ophiolite: A record of the latest deep-seated magmatism

NASA Astrophysics Data System (ADS)

Ishimaru, Satoko; Arai, Shoji; Tamura, Akihiro

2017-11-01

We found clinopyroxenite dykes in a banded harzburgite block within the Sumeini area in the uppermost part of the metamorphic sole of the northern part of the Oman ophiolite. The dykes clearly cut the deformational structure of the harzburgite and contain its fragments, indicating dyke formation during obduction of the ophiolite. The Mg# [= Mg / (Mg + total Fe)] of clinopyroxenes in the dykes ranges from 0.81 to 0.91, and increases up to 0.93 proximal to harzburgite fragments. Mantle minerals in the harzburgite fragments were modified chemically through interaction with the magma that formed the dyke, yielding lower clinopyroxene and spinel Mg#, and spinels with higher TiO2 contents than those in the unaltered harzburgite. These geochemical features indicate that the clinopyroxenite dykes are cumulates derived from a relatively deep-seated primitive magma enriched in light rare earth elements (LREE) with an ocean island basalt (OIB)-like affinity, geochemically similar to the V3 lavas of an off-ridge origin. Combining these data with geological observations suggests that the clinopyroxenite dykes represent root system of the V3 lavas. Our analyses of the clinopyroxenite dykes testify to the external nature of the V3 magmas, which was added to the sliced oceanic lithosphere from the outside. It is likely that the V3 magma underwent deep-seated crystallization of clinopyroxene and had limited interaction with mantle peridotite en route to the surface. The mode of occurrence of the Sumeini clinopyroxenites (i.e., emplaced into a banded harzburgite block surrounded by garnet amphibolite) is consistent with the generation of OIB-like magmas (V3 lava) beneath the Oman ophiolite resulting from the break-off of the "subducting slab" and subsequent infiltration of hot asthenospheric mantle. This view is consistent with the limited distribution of V3-related rocks in the Oman ophiolite. The production of such OIB-like magmas during ophiolite obduction is not a rare event

Pairing tendencies in a two-orbital Hubbard model in one dimension

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, Niravkumar D.; Nocera, Adriana; Alvarez, Gonzalo

The recent discovery of superconductivity under high pressure in the ladder compound BaFe2S3 has opened a new field of research in iron-based superconductors with focus on quasi-one-dimensional geometries. In this publication, using the density matrix renormalization group technique, we study a two-orbital Hubbard model defined in one-dimensional chains. Our main result is the presence of hole binding tendencies at intermediate Hubbard U repulsion and robust Hund coupling JH / U = 0.25. Binding does not occur either in weak coupling or at very strong coupling. The pair-pair correlations that are dominant near half-filling, or of similar strength as the chargemore » and spin correlation channels, involve hole-pair operators that are spin singlets, use nearest-neighbor sites, and employ different orbitals for each hole. As a result, the Hund coupling strength, presence of robust magnetic moments, and antiferromagnetic correlations among them are important for the binding tendencies found here.« less

Annual cycles of soil and water temperatures at Hubbard Brook

Treesearch

C. Anthony Federer

1973-01-01

Soil temperatures in the Hubbard Brook Experimental Forest in central New Hampshire decline very slowly from December to March and are restricted from falling below OºC by insulation of snow and organic matter. Soil in the hardwood forest on a moderate south slope warms rapidly in the spring leafless period after snowmelt and reaches a maximum temperature in...

Paleomagnetism of Devonian dykes in the northern Kola Peninsula and its bearing on the apparent polar wander path of Baltica in the Precambrian

NASA Astrophysics Data System (ADS)

Veselovskiy, Roman V.; Bazhenov, Mikhail L.; Arzamastsev, Andrey A.

2016-04-01

Mafic dykes and large alkaline and carbonatite intrusions of Middle-Late Devonian age are widespread on the Kola Peninsula in NE Fennoscandia. These magmatic rocks are well characterized with petrographic, geochemical and geochronological data but no paleomagnetic results have been reported yet. We studied dolerite dykes from the northern part of the Peninsula and isolated three paleomagnetic components in these rocks. A low-temperature component is aligned along the present-day field, while a major constituent of natural remanent magnetization is an intermediate-temperature component (Decl. = 79.6°, Inc. = 78.5°, α95 = 5,9°, N = 17 sites) that is present in most Devonian dykes but is found in some baked metamorphic rocks and Proterozoic dykes too. Finally, a primary Devonian component could be reliably isolated from two dykes only. Rock-magnetic studies point to presumably primary low-Ti titanomagnetite and/or pure magnetite as the main remanence carriers but also reveal alteration of the primary minerals and the formation of new magnetic phases. The directions of a major component differ from the Middle Paleozoic reference data for Baltica but closely match those for the 190 ± 10 Ma interval recalculated from the apparent polar wander path of the craton. We assume that this Early Jurassic component is a low-temperature overprint of chemical origin. The main impact of the new results is not to mid-Paleozoic or Early Mesozoic times but to much older epochs. Analysis of paleomagnetic data shows that the directionally similar remanences are present in objects with the ages ranging from 500 Ma to 2 Ga over entire Fennoscandia. Hence we argue that an Early Jurassic remagnetization is of regional extent but cannot link it to a certain process and a certain tectonic event. If true, this hypothesis necessitates a major revision of the APWP for Baltica over a wide time interval.

New constraints on the geochronology and Sm-Nd isotopic characteristics of Bas-Drâa mafic dykes, Anti-Atlas of Morocco

NASA Astrophysics Data System (ADS)

El Bahat, Abdelhakim; Ikenne, Moha; Cousens, Brian; Söderlund, Ulf; Ernst, Richard; Klausen, Martin B.; Youbi, Nasrrddine

2017-03-01

The Precambrian inliers of the Anti-Atlas belt across the southern part of Morocco contain numerous mafic dyke and sill swarms, which are thought to represent the erosional remnants of Proterozoic Large Igneous Provinces (LIPs). As part of an extended research campaign to date and characterize these LIPs, two amphiboles from one dyke within the Bas-Drâa inlier (western Anti-Atlas) yielded consistent 40Ar-39Ar ages of 611 Ma ± 1.3; i.e., evidence of magmatic activity during the Ediacaran (635-542 Ma). Furthermore, Nd isotope ratios and model ages identifies four groups of dykes within the Bas-Drâa inlier, all of which were derived from a previously enriched mantle reservoir with very low 143Nd/144Nd ratios (0.51065-0.51170) and corresponding εNd(t) values (-16.44 to -2.45). Such low Nd-ratios arguably reflect either a contribution of crustal components, such as the Paleoproterozoïc schisto-granitic basement, or metasomatic modification of the sub-continental lithospheric mantle.

Proterozoic Diabase Dyke Swarms of Northern Ontario: Paleomagnetic Indicators of Broad-Scale Crustal Deformation of the Archean Superior Province

NASA Astrophysics Data System (ADS)

Halls, H. C.

2004-05-01

Several Proterozoic dyke swarms, all with precise U-Pb ages, (Matachewan, Senneterre, Biscotasing, Marathon and Fort Frances) occur over an area of the southern Superior Province covering more than 300,000 square kilometres. Cutting across this region is the Kapuskasing Zone, a 500 km-long fault zone along which dextral transpression at about 1.9 to 2.0 Ga has produced crustal uplift locally in excess of 20 km and lateral fault displacements of up to 70 km (Percival and West, 1994). The 2446-2473 Ma Matachewan swarm has been a subject for study throughout the last 40 years of Canadian paleomagnetism. However only in the last 20 years has the true size of the swarm been realised (Ernst and Halls, 1984; Halls et al., 1994), and the discovery made that regional variations in the direction of primary magnetization in the dykes are intimately related to the Kapuskasing Zone (KZ). The swarm is now known to span a single reversal of the Earth's magnetic field. The younger N polarity epoch, although barely recorded in the dying stages of the intrusive episode, is well preserved in dykes within uplifted crust inside the KZ. Here fine-grained magnetite, exsolved from dyke feldspars due to slow cooling of the swarm at depth, acquired a remanence of probable thermo-chemical origin prior to or during crustal uplift (Halls and Palmer, 1990; Halls et al., 1994; Halls and Zhang, 2003). The inference is that dykes intruded during the older R polarity epoch carry a near surface primary R magnetization but have been remagnetized to N at depth. Paleomagnetic data from that part of the swarm outside the KZ are therefore dominated by the older R polarity magnetization. They show that the western half of the shield has rotated counter-clockwise about 10 to 20 degrees relative to the eastern half across the KZ (Bates and Halls, 1991; Halls and Stott, 2003). This rotation is also seen in paleomagnetic data from the 2170 Ma Biscotasing swarm, which is now known to occur on both sides of the

Palaeointensity determinations on rocks from the Achaean- Paleoproterozoic dykes from the Karelian craton

NASA Astrophysics Data System (ADS)

Shcherbakov, Valera; Shcherbakova, Valentina; Lubnina, Natalia; Zhidkov, Grigory; Tsel'movich, Vladimir

2017-04-01

The Karelian craton was a fragment of either an earlier late Archean supercontinent, sometimes referred to as Kenorland. Now the craton is a large Archean composite granite-greenstone terrane in the eastern part of the Fennoscandian Shield bounded by Paleoproterozoic Svecofennian orogen in the south-west and by Lapland-Kola orogen in the north-east and Belomorian province in the east-north-east. Mafic dykes, volcanic rocks, sills, and layered intrusions with ages of ca. 2.51-2.45 Ga and ca. 2.06-1.95 Ga are widespread and well-studied in the Karelian Craton. Paleointensity (Banc) results obtained on the Shala dike (age of 2504 Ma by U-Pb, ID TIMS) tracked near vl. Shala and on the Deda island are discussed here. Eighteen block samples of gabbronotires were collected in two sites in the Shala quarry. Stepwise thermal demagnetization (≤ 20 steps, up to 600 C) and stepwise AF demagnetization were done. To monitor possible mineralogical changes during thermal cleaning, magnetic susceptibility was measured after each heating step. Intensive rock magnetic investigations and thermal palaeointensity experiments using the Thellier-Coe (with check-points) and Wilson procedures were carried out. Electronic microscopy study of two samples was made too. For the exception of a viscous component some specimens from the contact zone of the gabbronorite dyke with thin dolerite dyke show two distinct components. The first E-NE intermediate-down direction component was separated at fields up to 50-60 mT and unblocking temperatures up to 520-540 C. The other S-SE low-down direction component is separated at fields from 60 to 100 mT and unblocking temperatures from 540 to 590-600 C. Based on the positive contact tests for the gabbronorite dyke, the S-SE shallow inclination remanence (I = -5.7 degrees) is interpreted to be of primary origin. Reliable palaeointensity determinations Banc fitting a set of selection criteria were determined on 13 samples from 2 sites carrying

Chemistry of precipitation, streamwater, and lakewater from the Hubbard Brook Ecosystem Study: a record of sampling protocols and analytical procedures

Treesearch

Donald C. Buso; Gene E. Likens; John S. Eaton

2000-01-01

The Hubbard Brook Ecosystem Study (HBES), begun in 1963, is a long-term effort to understand the structure, function and change in forest watersheds and associated aquatic ecosystems at the Hubbard Brook Experimental Forest in New Hampshire. Chemical analyses of streamwater and precipitation collections began in 1963, and analyses of lakewater collections began in 1967...

The Chara-Sina dyke swarm in the structure of the Middle Paleozoic Vilyui rift system (Siberian Craton)

NASA Astrophysics Data System (ADS)

Kiselev, A. I.; Konstantinov, K. M.; Yarmolyuk, V. V.; Ivanov, A. V.

2016-11-01

The formation of the Vilyui rift system in the eastern Siberian Craton was finished with breakdown of the continent and formation of its eastern margin. A characteristic feature of this rift system is the radial distribution of dyke swarms of basic rocks. This peculiarity allows us to relate it to the breaking processes above the mantle plume, the center of which was located in the region overlain in the modern structure by the foreland of the Verkhoyan folded-thrust belt. The Chara-Sina dyke swarm is the southern part of a large area of Middle Paleozoic basaltic magmatism in the eastern Siberian Craton. The OIB-like geochemical characteristics of dolerite allow us to suggest that the melting substrate for Middle Paleozoic basaltic magmatism was represented by a relatively homogeneous, mid-depleted mantle of the plume with geochemical parameters similar to those of OIB.

Evolution of Quasiparticle Excitations in a Doped Hubbard Model

NASA Astrophysics Data System (ADS)

Hess, D. W.; Deisz, J. J.; Serene, J. W.

1997-03-01

Self-consistent calculations in the fluctuation exchange approximation for the 2D Hubbard model at half-filling show the evolution of anomalous structure in the self-energy at low energy with decreasing temperature. This structure is inconsistent with a Fermi liquid interpretation of evolving quasiparticle excitations.(J.J. Deisz, D.W. Hess, J.W. Serene, Phys. Rev. Lett. 76), 1312 (1996). Here we present calculations for a doped 2D Hubbard model with U=4t, n = 0.87 and for temperatures down to ~ 0.01t. Unlike the self-energy of the half-filled case, the slope of Re Σ(k_F, \\varepsilon) remains negative and | Im Σ(k_F, \\varepsilon)| shows no anomalous structure and is roughly parabolic at low energy with a very small magnitude at \\varepsilon = 0. In contrast to the `shadows' of antiferromagnetic order observed for half-filling, structure observed in the single-particle spectral function for momenta not on the Fermi surface are consistent with the characteristic depression at \\varepsilon =0 expected for an evolving Fermi liquid.(See e.g.) P.G. Mc Queen, D.W. Hess, J.W. Serene, Phys. Rev. Lett. 71, 129 (1993). No anomalous structure associated with incipient antiferromagnetic order is evident in the momentum distribution function.

Numerical simulations - Some results for the 2- and 3-D Hubbard models and a 2-D electron phonon model

NASA Technical Reports Server (NTRS)

Scalapino, D. J.; Sugar, R. L.; White, S. R.; Bickers, N. E.; Scalettar, R. T.

1989-01-01

Numerical simulations on the half-filled three-dimensional Hubbard model clearly show the onset of Neel order. Simulations of the two-dimensional electron-phonon Holstein model show the competition between the formation of a Peierls-CDW state and a superconducting state. However, the behavior of the partly filled two-dimensional Hubbard model is more difficult to determine. At half-filling, the antiferromagnetic correlations grow as T is reduced. Doping away from half-filling suppresses these correlations, and it is found that there is a weak attractive pairing interaction in the d-wave channel. However, the strength of the pair field susceptibility is weak at the temperatures and lattice sizes that have been simulated, and the nature of the low-temperature state of the nearly half-filled Hubbard model remains open.

Diversity of Tn1546 in vanA-positive Enterococcus faecium clinical isolates with VanA, VanB, and VanD phenotypes and susceptibility to vancomycin.

PubMed

Cha, J O; Yoo, J I; Kim, H K; Kim, H S; Yoo, J S; Lee, Y S; Jung, Y H

2013-10-01

To investigate diversity in the vanA cluster in Enterococcus faecium isolates from nontertiary hospitals. We identified 43 vanA-positive Ent. faecium isolates, including two vancomycin-susceptible isolates, from hospitals between 2003 and 2006. Of these isolates, >85% were resistant to ampicillin, erythromycin and ciprofloxacin. The vanA cluster was classified into six types using overlapping PCR, but the prototype transposon Tn1546 was not found. Most vanA-positive vancomycin-resistant Enterococcus (VRE) carried IS1216V and belonged to Type III (58·1%) or Type II (20·9%). vanY, vanZ and IS1216V were observed in the left and right ends of Type III with long-range PCR. IS1216V was also observed within vanS and vanX in the two vancomycin-susceptible isolates and in two vancomycin-resistant isolates. No VRE isolates with VanB and VanD phenotypes contained point mutations in vanS, unlike in previous reports. Sequence types (STs) of all isolates belonged to clonal complex 17, and ST78 was predominant. Insertion sequences, especially IS1216V, cause structural variation in the vanA cluster. We report the first observation of vanY and vanZ at the left end of Tn1546 in clinical isolates. This is the first report of the frequency of vancomycin resistance and diversity of Tn1546 in vanA-positive Ent. faecium isolates from nontertiary hospitals. © 2013 The Society for Applied Microbiology.

Chemical and morphological distinctions between vertical and lateral podzolization at Hubbard Brook

Treesearch

Rebecca R. Bourgault; Donald S. Ross; Scott W. Bailey

2015-01-01

Classical podzolization studies assumed vertical percolation and pedon-scale horizon development. However, hillslope-scale lateral podzolization also occurs where lateral subsurface water flux predominates. In this hydropedologic study, 99 podzols were observed in Watershed 3, Hubbard Brook Experimental Forest, New Hampshire. Soil horizon samples were extracted with...

Madelung and Hubbard interactions in polaron band model of doped organic semiconductors

PubMed Central

Png, Rui-Qi; Ang, Mervin C.Y.; Teo, Meng-How; Choo, Kim-Kian; Tang, Cindy Guanyu; Belaineh, Dagmawi; Chua, Lay-Lay; Ho, Peter K.H.

2016-01-01

The standard polaron band model of doped organic semiconductors predicts that density-of-states shift into the π–π* gap to give a partially filled polaron band that pins the Fermi level. This picture neglects both Madelung and Hubbard interactions. Here we show using ultrahigh workfunction hole-doped model triarylamine–fluorene copolymers that Hubbard interaction strongly splits the singly-occupied molecular orbital from its empty counterpart, while Madelung (Coulomb) interactions with counter-anions and other carriers markedly shift energies of the frontier orbitals. These interactions lower the singly-occupied molecular orbital band below the valence band edge and give rise to an empty low-lying counterpart band. The Fermi level, and hence workfunction, is determined by conjunction of the bottom edge of this empty band and the top edge of the valence band. Calculations are consistent with the observed Fermi-level downshift with counter-anion size and the observed dependence of workfunction on doping level in the strongly doped regime. PMID:27582355

Quench dynamics of the spin-imbalanced Fermi-Hubbard model in one dimension

NASA Astrophysics Data System (ADS)

Yin, Xiao; Radzihovsky, Leo

2016-12-01

We study a nonequilibrium dynamics of a one-dimensional spin-imbalanced Fermi-Hubbard model following a quantum quench of on-site interaction, realizable, for example, in Feshbach-resonant atomic Fermi gases. We focus on the post-quench evolution starting from the initial BCS and Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) ground states and analyze the corresponding spin-singlet, spin-triplet, density-density, and magnetization-magnetization correlation functions. We find that beyond a light-cone crossover time, rich post-quench dynamics leads to thermalized and pre-thermalized stationary states that display strong dependence on the initial ground state. For initially gapped BCS state, the long-time stationary state resembles thermalization with the effective temperature set by the initial value of the Hubbard interaction. In contrast, while the initial gapless FFLO state reaches a stationary pre-thermalized form, it remains far from equilibrium. We suggest that such post-quench dynamics can be used as a fingerprint for identification and study of the FFLO phase.

Populations of Rice Grain Bug, Paraeuscosmetus pallicomis, (Hemiptera: Lygaeidae) in Weed-free Paddy Field, Weedy Paddy Field and Paddy Dykes.

PubMed

Abdullah, Tamrin; Nasruddin, Andi; Agus, Nurariaty

2017-07-01

Research on the populations of rice grain bug Paraeuscosmetus pallicomis Dallas (Hemiptera: Lygaeidae) in paddy field ecosystems was performed with the aim to determine the populations of rice grain bug in weed-free paddy field, weedy paddy field, and paddy dykes. Experiment was carried out in the village of Paccellekang in the district of Patallasang of Gowa Regency in South Sulawesi, Indonesia. Observations were performed during the milky grain stage (85 days after planting), the mature grain stage (105 days after planting), and one day after harvest (115 days after transplanting). Results showed that 85 days after the transplanting, the populations of rice grain bug was significantly higher in the weedy paddy field compared to weed-free field and paddy dykes with total numbers of 1.75, 3.53, and 0.31 insects per 2 hills, respectively. Similarly, 105 days after the transplanting, 2.53, 5.53, and 0.11 insects per hill, respectively. However, one day after the harvest (115 days after transplanting) the number of insects in weed-free field decreased, while in the dykes increased, and the weedy plot still had the highest number of insects per 2 hills. Our results suggested that weeds played an important role in regulating the bug population by providing alternative shelter and foods for the insect.

Fidelity study of the superconducting phase diagram in the two-dimensional single-band Hubbard model

NASA Astrophysics Data System (ADS)

Jia, C. J.; Moritz, B.; Chen, C.-C.; Shastry, B. Sriram; Devereaux, T. P.

2011-09-01

Extensive numerical studies have demonstrated that the two-dimensional single-band Hubbard model contains much of the key physics in cuprate high-temperature superconductors. However, there is no definitive proof that the Hubbard model truly possesses a superconducting ground state or, if it does, of how it depends on model parameters. To answer these longstanding questions, we study an extension of the Hubbard model including an infinite-range d-wave pair field term, which precipitates a superconducting state in the d-wave channel. Using exact diagonalization on 16-site square clusters, we study the evolution of the ground state as a function of the strength of the pairing term. This is achieved by monitoring the fidelity metric of the ground state, as well as determining the ratio between the two largest eigenvalues of the d-wave pair/spin/charge-density matrices. The calculations show a d-wave superconducting ground state in doped clusters bracketed by a strong antiferromagnetic state at half filling controlled by the Coulomb repulsion U and a weak short-range checkerboard charge ordered state at larger hole doping controlled by the next-nearest-neighbor hopping t'. We also demonstrate that negative t' plays an important role in facilitating d-wave superconductivity.

Presence of the vancomycin resistance gene cluster vanC1, vanXYc, and vanT in Enterococcus casseliflavus.

PubMed

Hölzel, Christina; Bauer, Johann; Stegherr, Eva-Maria; Schwaiger, Karin

2014-04-01

The three chromosomally located clustered genes vanC1, vanXYc, and vanT confer intrinsic resistance to vancomycin and are used for species identification of Enterococcus gallinarum. In this study, 28 strains belonging to the E. gallinarum/casseliflavus group isolated from cloacal swabs from laying hens were screened for the presence of vanC1. As confirmed by species-specific multiplex PCR, 11 vanC1-positive strains were identified as E. gallinarum. Surprisingly, one yellow pigmented strain, verified as E. casseliflavus by species-specific multiplex PCR, was also vanC1 positive; vanXYc and vanT were additionally detectable in this strain. To our knowledge, this is the first report of vanC1, vanXYc, and vanT in E. casseliflavus. The minimum inhibitory concentration of vancomycin was 4 mg/L. Real-time reverse transcription-PCR revealed that none of the clustered genes was expressed in this strain. Even if the genes seem not to be active, there is a certain risk that they will be transferred to other bacteria where they might be functionally expressed. Therefore, it may be advisable to expand the search for vanC1, vanXYc, and vanT from E. gallinarum to other (enterococcal) species. This study confirms that enterococci live up to their name as being reservoir bacteria and should therefore always be closely monitored.

Universal thermodynamics of the one-dimensional attractive Hubbard model

NASA Astrophysics Data System (ADS)

Cheng, Song; Yu, Yi-Cong; Batchelor, M. T.; Guan, Xi-Wen

2018-03-01

The one-dimensional (1D) Hubbard model, describing electrons on a lattice with an on-site repulsive interaction, provides a paradigm for the physics of quantum many-body phenomena. Here, by solving the thermodynamic Bethe ansatz equations, we study the universal thermodynamics, quantum criticality, and magnetism of the 1D attractive Hubbard model. We show that the compressibility and the susceptibility of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)-like state obey simple additivity rules at low temperatures, indicating an existence of two free quantum fluids. The magnetic properties, such as magnetization and susceptibility, reveal three physical regions: quantum fluids at low temperatures, a non-Fermi liquid at high temperatures, and the quantum fluid to non-Fermi liquid crossover in between. The lattice interaction is seen to significantly influence the nature of the FFLO-like state in 1D. Furthermore, we show that the dimensionless Wilson ratio provides an ideal parameter to map out the various phase boundaries and to characterize the two free fluids of the FLLO-like state. The quantum scaling functions for the thermal and magnetic properties yield the same dynamic critical exponent z =2 and correlation critical exponent ν =1 /2 in the quantum critical region whenever a phase transition occurs. Our results provide a rigorous understanding of quantum criticality and free fluids of many-body systems on a 1D lattice.

Long-term trends from ecosystem research at the Hubbard Brook Experimental Forest

Treesearch

John L. Campbell; Charles T. Driscoll; Christopher Eagar; Gene E. Likens; Thomas G. Siccama; Chris E. Johnson; Timothy J. Fahey; Steven P. Hamburg; Richard T. Holmes; Amey S. Bailey; Donald C. Buso

2007-01-01

Summarizes 52 years of collaborative, long-term research conducted at the Hubbard Brook (NH) Experimental Forest on ecosystem response to disturbances such as air pollution, climate change, forest disturbance, and forest management practices. Also provides explanations of some of the trends and lists references from scientific literature for further reading.

Contribution of the FUTUREVOLC project to the study of segmented lateral dyke growth in the 2014 rifting event at Bárðarbunga volcanic system, Iceland

NASA Astrophysics Data System (ADS)

Sigmundsson, Freysteinn; Hooper, Andrew; Hreinsdóttir, Sigrún; Vogfjörd, Kristín S.; Ófeigsson, Benedikt; Rafn Heimisson, Elías; Dumont, Stéphanie; Parks, Michelle; Spaans, Karsten; Guðmundsson, Gunnar B.; Drouin, Vincent; Árnadóttir, Thóra; Jónsdóttir, Kristín; Gudmundsson, Magnús T.; Samsonov, Sergey; Brandsdóttir, Bryndís; White, Robert S.; Ágústsdóttir, Thorbjörg; Björnsson, Helgi; Bean, Christopher J.

2015-04-01

The FUTUREVOLC project (a 26-partner project funded by FP7 Environment Programme of the European Commission, addressing topic "Long-term monitoring experiment in geologically active regions of Europe prone to natural hazards: the Supersite concept) set aims to (i) establish an innovative volcano monitoring system and strategy, (ii) develop new methods for near real-time integration of multi-parametric datasets, (iii) apply a seamless transdisciplinary approach to further scientific understanding of magmatic processes, and (iv) to improve delivery, quality and timeliness of transdisciplinary information from monitoring scientists to civil protection. The project duration is 1 October 2012 - 31 March 2016. Unrest and volcanic activity since August 2014 at one of the focus areas of the project in Iceland, at the Bárðarbunga volcanic system, near the middle of the project duration, has offered unique opportunities for this project. On 16 August 2014 an intense seismic swarm started in Bárðarbunga, the beginning of a major volcano-tectonic rifting event forming over 45 km long dyke extending from the caldera to Holuhraun lava field outside the northern margin of Vatnajökull. A large basaltic, effusive fissure eruption began in Holuhraun on 31 August which had by January formed a lava field with a volume in excess of one cubic kilometre. We document how the FUTUREVOLC project has contributed to the study and response to the subsurface dyke formation, through increased seismic and geodetic coverage and joint interpreation of the data. The dyke intrusion in the Bárðarbunga volcanic system, grew laterally for over 45 km at a variable rate, with an influence of topography on the direction of propagation. Barriers at the ends of each segment were overcome by the build-up of pressure in the dyke end; then a new segment formed and dyke lengthening temporarily peaked. The dyke evolution, which occurred over 14 days, was revealed by propagating seismicity, ground

The slow advance of a calving glacier: Hubbard Glacier, Alaska, U.S.A

USGS Publications Warehouse

Trabant, D.C.; Krimmel, R.M.; Echelmeyer, K.A.; Zirnheld, S.L.; Elsberg, D.H.

2003-01-01

Hubbard Glacier is the largest tidewater glacier in North America. In contrast to most glaciers in Alaska and northwestern Canada, Hubbard Glacier thickened and advanced during the 20th century. This atypical behavior is an important example of how insensitive to climate a glacier can become during parts of the calving glacier cycle. As this glacier continues to advance, it will close the seaward entrance to 50 km long Russell Fjord and create a glacier-dammed, brackish-water lake. This paper describes measured changes in ice thickness, ice speed, terminus advance and fjord bathymetry of Hubbard Glacier, as determined from airborne laser altimetry, aerial photogrammetry, satellite imagery and bathymetric measurements. The data show that the lower regions of the glacier have thickened by as much as 83 m in the last 41 years, while the entire glacier increased in volume by 14.1 km3. Ice speeds are generally decreasing near the calving face from a high of 16.5 m d-1 in 1948 to 11.5 m d-1 in 2001. The calving terminus advanced at an average rate of about 16 m a-1 between 1895 and 1948 and accelerated to 32 m a-1 since 1948. However, since 1986, the advance of the part of the terminus in Disenchantment Bay has slowed to 28 m a-1. Bathymetric data from the lee slope of the submarine terminal moraine show that between 1978 and 1999 the moraine advanced at an average rate of 32 m a-1, which is the same as that of the calving face.

Collective charge excitations and the metal-insulator transition in the square lattice Hubbard-Coulomb model

DOE PAGES

Ulybyshev, Maksim; Winterowd, Christopher; Zafeiropoulos, Savvas

2017-11-09

Here in this article, we discuss the nontrivial collective charge excitations (plasmons) of the extended square lattice Hubbard model. Using a fully nonperturbative approach, we employ the hybrid Monte Carlo algorithm to simulate the system at half-filling. A modified Backus-Gilbert method is introduced to obtain the spectral functions via numerical analytic continuation. We directly compute the single-particle density of states which demonstrates the formation of Hubbard bands in the strongly correlated phase. The momentum-resolved charge susceptibility also is computed on the basis of the Euclidean charge-density-density correlator. In agreement with previous extended dynamical mean-field theory studies, we find that, atmore » high strength of the electron-electron interaction, the plasmon dispersion develops two branches.« less

Collective charge excitations and the metal-insulator transition in the square lattice Hubbard-Coulomb model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ulybyshev, Maksim; Winterowd, Christopher; Zafeiropoulos, Savvas

Here in this article, we discuss the nontrivial collective charge excitations (plasmons) of the extended square lattice Hubbard model. Using a fully nonperturbative approach, we employ the hybrid Monte Carlo algorithm to simulate the system at half-filling. A modified Backus-Gilbert method is introduced to obtain the spectral functions via numerical analytic continuation. We directly compute the single-particle density of states which demonstrates the formation of Hubbard bands in the strongly correlated phase. The momentum-resolved charge susceptibility also is computed on the basis of the Euclidean charge-density-density correlator. In agreement with previous extended dynamical mean-field theory studies, we find that, atmore » high strength of the electron-electron interaction, the plasmon dispersion develops two branches.« less

Charge and Spin Dynamics of the Hubbard Chains

NASA Technical Reports Server (NTRS)

Park, Youngho; Liang, Shoudan

1999-01-01

We calculate the local correlation functions of charge and spin for the one-chain and two-chain Hubbard model using density matrix renormalization group method and the recursion technique. Keeping only finite number of states we get good accuracy for the low energy excitations. We study the charge and spin gaps, bandwidths and weights of the spectra for various values of the on-site Coulomb interaction U and the electron filling. In the low energy part, the local correlation functions are different for the charge and spin. The bandwidths are proportional to t for the charge and J for the spin respectively.

Continuous-variable gate decomposition for the Bose-Hubbard model

NASA Astrophysics Data System (ADS)

Kalajdzievski, Timjan; Weedbrook, Christian; Rebentrost, Patrick

2018-06-01

In this work, we decompose the time evolution of the Bose-Hubbard model into a sequence of logic gates that can be implemented on a continuous-variable photonic quantum computer. We examine the structure of the circuit that represents this time evolution for one-dimensional and two-dimensional lattices. The elementary gates needed for the implementation are counted as a function of lattice size. We also include the contribution of the leading dipole interaction term which may be added to the Hamiltonian and its corresponding circuit.

Thermalization after an interaction quench in the Hubbard model.

PubMed

Eckstein, Martin; Kollar, Marcus; Werner, Philipp

2009-07-31

We use nonequilibrium dynamical mean-field theory to study the time evolution of the fermionic Hubbard model after an interaction quench. Both in the weak-coupling and in the strong-coupling regime the system is trapped in quasistationary states on intermediate time scales. These two regimes are separated by a sharp crossover at U(c)dyn=0.8 in units of the bandwidth, where fast thermalization occurs. Our results indicate a dynamical phase transition which should be observable in experiments on trapped fermionic atoms.

Unsupervised machine learning account of magnetic transitions in the Hubbard model

NASA Astrophysics Data System (ADS)

Ch'ng, Kelvin; Vazquez, Nick; Khatami, Ehsan

2018-01-01

We employ several unsupervised machine learning techniques, including autoencoders, random trees embedding, and t -distributed stochastic neighboring ensemble (t -SNE), to reduce the dimensionality of, and therefore classify, raw (auxiliary) spin configurations generated, through Monte Carlo simulations of small clusters, for the Ising and Fermi-Hubbard models at finite temperatures. Results from a convolutional autoencoder for the three-dimensional Ising model can be shown to produce the magnetization and the susceptibility as a function of temperature with a high degree of accuracy. Quantum fluctuations distort this picture and prevent us from making such connections between the output of the autoencoder and physical observables for the Hubbard model. However, we are able to define an indicator based on the output of the t -SNE algorithm that shows a near perfect agreement with the antiferromagnetic structure factor of the model in two and three spatial dimensions in the weak-coupling regime. t -SNE also predicts a transition to the canted antiferromagnetic phase for the three-dimensional model when a strong magnetic field is present. We show that these techniques cannot be expected to work away from half filling when the "sign problem" in quantum Monte Carlo simulations is present.

Populations of Rice Grain Bug, Paraeuscosmetus pallicomis, (Hemiptera: Lygaeidae) in Weed-free Paddy Field, Weedy Paddy Field and Paddy Dykes

PubMed Central

Abdullah, Tamrin; Nasruddin, Andi; Agus, Nurariaty

2017-01-01

Research on the populations of rice grain bug Paraeuscosmetus pallicomis Dallas (Hemiptera: Lygaeidae) in paddy field ecosystems was performed with the aim to determine the populations of rice grain bug in weed-free paddy field, weedy paddy field, and paddy dykes. Experiment was carried out in the village of Paccellekang in the district of Patallasang of Gowa Regency in South Sulawesi, Indonesia. Observations were performed during the milky grain stage (85 days after planting), the mature grain stage (105 days after planting), and one day after harvest (115 days after transplanting). Results showed that 85 days after the transplanting, the populations of rice grain bug was significantly higher in the weedy paddy field compared to weed-free field and paddy dykes with total numbers of 1.75, 3.53, and 0.31 insects per 2 hills, respectively. Similarly, 105 days after the transplanting, 2.53, 5.53, and 0.11 insects per hill, respectively. However, one day after the harvest (115 days after transplanting) the number of insects in weed-free field decreased, while in the dykes increased, and the weedy plot still had the highest number of insects per 2 hills. Our results suggested that weeds played an important role in regulating the bug population by providing alternative shelter and foods for the insect. PMID:28890757

Valles Marineris as a Cryokarstic Structure Formed by a Giant Dyke System: Support From New Analogue Experiments

NASA Astrophysics Data System (ADS)

Ozeren, M. S.; Sengor, A. M. C.; Acar, D.; Ülgen, S. C.; Onsel, I. E.

2014-12-01

Valles Marineris is the most significant near-linear depression on Mars. It is some 4000 km long, up to about 200 km wide and some 7 km deep. Although its margins look parallel at first sight, the entire structure has a long spindle shape with significant enlargement in its middle (Melas Chasma) caused by cuspate slope retreat mechanisms. Farther to its north is Hebes Chasma which is an entirely closed depression with a more pronounced spindle shape. Tithonium Chasma is a parallel, but much narrower depression to its northeast. All these chasmae have axes parallel with one another and such structures occur nowhere else on Mars. A scabland surface exists to the east of the Valles Marineris and the causative water mass seems to have issued from it. The great resemblance of these chasmae on mars to poljes in the karstic regions on earth have led us to assume that they owed their existence to dissolution of rock layers underlying them. We assumed that the dissolving layer consisted of water ice forming substantial layers, in fact entirely frozen seas of several km depth. We have simulated this geometry by using bentonite and flour layers (in different experiments) overlying layers of ice in which a resistant coil was used to simulate a dyke. We used different thicknesses of bentonite and flour overlying ice layers again of various thicknesses. The flour seems to simulate the Martian crust better because on Mars, g is only about 3/8ths of its value on Earth, so (for equal crustal density) the depth to which the cohesion term C remains important in the Mohr-Coulomb shear failure criterion is about 8/3 times greater. As examples we show two of those experiments in which both the rock analogue and ice layers were of 1.5 cm. thick. Perfect analogues of the Valles Marineris formed above the dyke analogue thermal source complete with the near-linear structure, overall flat spindle shape, cuspate margins, a central ridge, parallel side faults, parallel depressions resembling

Low-lying Photoexcited States of a One-Dimensional Ionic Extended Hubbard Model

NASA Astrophysics Data System (ADS)

Yokoi, Kota; Maeshima, Nobuya; Hino, Ken-ichi

2017-10-01

We investigate the properties of low-lying photoexcited states of a one-dimensional (1D) ionic extended Hubbard model at half-filling. Numerical analysis by using the full and Lanczos diagonalization methods shows that, in the ionic phase, there exist low-lying photoexcited states below the charge transfer gap. As a result of comparison with numerical data for the 1D antiferromagnetic (AF) Heisenberg model, it was found that, for a small alternating potential Δ, these low-lying photoexcited states are spin excitations, which is consistent with a previous analytical study [Katsura et al., Phys. Rev. Lett. 103, 177402 (2009)]. As Δ increases, the spectral intensity of the 1D ionic extended Hubbard model rapidly deviates from that of the 1D AF Heisenberg model and it is clarified that this deviation is due to the neutral-ionic domain wall, an elementary excitation near the neutral-ionic transition point.

Probing density and spin correlations in two-dimensional Hubbard model with ultracold fermions

NASA Astrophysics Data System (ADS)

Chan, Chun Fai; Drewes, Jan Henning; Gall, Marcell; Wurz, Nicola; Cocchi, Eugenio; Miller, Luke; Pertot, Daniel; Brennecke, Ferdinand; Koehl, Michael

2017-04-01

Quantum gases of interacting fermionic atoms in optical lattices is a promising candidate to study strongly correlated quantum phases of the Hubbard model such as the Mott-insulator, spin-ordered phases, or in particular d-wave superconductivity. We experimentally realise the two-dimensional Hubbard model by loading a quantum degenerate Fermi gas of 40 K atoms into a three-dimensional optical lattice geometry. High-resolution absorption imaging in combination with radiofrequency spectroscopy is applied to spatially resolve the atomic distribution in a single 2D layer. We investigate in local measurements of spatial correlations in both the density and spin sector as a function of filling, temperature and interaction strength. In the density sector, we compare the local density fluctuations and the global thermodynamic quantities, and in the spin sector, we observe the onset of non-local spin correlation, signalling the emergence of the anti-ferromagnetic phase. We would report our recent experimental endeavours to investigate further down in temperature in the spin sector.

Mapping and characterization from aeromagnetic data of the Foum Zguid dolerite Dyke (Anti-Atlas, Morocco) a member of the Central Atlantic Magmatic Province (CAMP)

NASA Astrophysics Data System (ADS)

Bouiflane, Mustapha; Manar, Ahmed; Medina, Fida; Youbi, Nasrrddine; Rimi, Abdelkrim

2017-06-01

A high-resolution aeromagnetic survey was carried out in the Anti- Atlas, Morocco covering the main areas traversed by the Great CAMP Foum Zguid dyke (FZD). This ;doleritic; dyke belongs to the Central Atlantic Magmatic Province (CAMP), a Large Igneous Province which is associated with the fragmentation of the supercontinent Pangaea and the initial stages of rifting of the Central Atlantic Ocean. It also coincides in time with the mass extinction of the Triassic - Jurassic boundary. Based on the study of geological maps and Google Earth satellite images, it appears that the FZD is poorly exposed and, often covered by Quaternary deposits. This work proposes aeromagnetic modelling and interpretation of the FZD in order to better constrain its structural extent. The data have allowed (i) mapping of the dyke over great distances, under the Quaternary deposits and through areas where it was poorly characterized on the geological map; (ii) identifying major tectonic lineaments interpreted as faults; (iii) recognizing magnetic anomalies related to mafic intrusive bodies; and (iv) informing about regional structural context.

Past and future effects of atmospheric deposition on the forest ecosystem at the Hubbard Brook Experimental Forest: simulations with the dynamic model ForSAFE

Treesearch

Salim Belyazid; Scott Bailey; Harald Sverdrup

2010-01-01

The Hubbard Brook Ecosystem Study presents a unique opportunity for studying long-term ecosystem responses to changes in anthropogenic factors. Following industrialisation and the intensification of agriculture, the Hubbard Brook Experimental Forest (HBEF) has been subject to increased loads of atmospheric deposition, particularly sulfur and nitrogen. The deposition of...

Integrated elemental and Sr-Nd-Pb-Hf isotopic studies of Mesozoic mafic dykes from the eastern North China Craton: implications for the dramatic transformation of lithospheric mantle

NASA Astrophysics Data System (ADS)

Liu, Shen; Feng, Caixia; Santosh, M.; Feng, Guangying; Coulson, Ian M.; Xu, Mengjing; Guo, Zhuang; Guo, Xiaolei; Peng, Hao; Feng, Qiang

2018-02-01

Evolution of the lithospheric mantle beneath the North China Craton (NCC) from its Precambrian cratonic architecture until Paleozoic, and the transformation to an oceanic realm during Mesozoic, with implications on the destruction of cratonic root have attracted global attention. Here we present geochemical and isotopic data on a suite of newly identified Mesozoic mafic dyke swarms from the Longwangmiao, Weijiazhuang, Mengjiazhuang, Jiayou, Huangmi, and Xiahonghe areas (Qianhuai Block) along the eastern NCC with an attempt to gain further insights on the lithospheric evolution of the region. The Longwangmiao dykes are alkaline with LILE (Ba and K)- and LREE-enrichment ((La/Yb) N > 4.3) and EM1-like Sr-Nd-Pb-Hf isotopic signature ((87Sr/86Sr) i > 0.706; ε Nd (t) < -6.3, (206Pb/204Pb) i > 16.6, (207Pb/204Pb) i > 15.4, (208Pb/204Pb) i > 36.8, ε Hf (t) < -22.4). The Weijiazhuang dykes are sub-alkaline with LILE (Ba and K)- and LREE-enrichment ((La/Yb) N > 3.7), and display similar EM1-like isotopic features ((87Sr/86Sr) i > 0.706; ε Nd (t) < -7.0, (206Pb/204Pb) i > 16.7, (207Pb/204Pb) i > 15.4, (208Pb/204Pb) i > 36.9, ε Hf (t) < -23.3). The Mengjiazhuang dykes are also sub-alkaline with LILE (Ba and K)- and LREE-enrichment ((La/Yb) N > 2.4) and EM1-like isotopic features((87Sr/86Sr) i > 0.706; ε Nd (t) < -18.4, (206Pb/204Pb) i > 16.7, (207Pb/204Pb) i > 15.4, (208Pb/204Pb) i > 36.9, ε Hf (t) < -8.6). The Jiayou dykes also display sub-alkaline affinity with LILE (Ba and K)- and LREE-enrichment ((La/Yb) N > 3.7) and EM1-like Sr-Nd-Pb-Hf isotopic features ((87Sr/86Sr) i > 0.706; ε Nd(t) < -15.3, (206Pb/204Pb) i > 16.7, (207Pb/204Pb) i > 15.4, (208Pb/204Pb) i > 36.9, ε Hf (t) < -18.4). The Huangmi dykes are alkaline (with Na2O + K2O ranging to more than 5.9 wt.%)) with LILE (Ba and K)- and LREE-enrichment ((La/Yb) N > 9.3) and EM1-like isotopic composition ((87Sr/86Sr) i > 0.705; ε Nd (t) < -15.1, (206Pb/204Pb) i > 16.9, (207Pb/204Pb) i > 15.5, (208Pb/204Pb) i > 36

Two-polariton bound states in the Jaynes-Cummings-Hubbard model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wong, Max T. C.; Law, C. K.

2011-05-15

We examine the eigenstates of the one-dimensional Jaynes-Cummings-Hubbard model in the two-excitation subspace. We discover that two-excitation bound states emerge when the ratio of vacuum Rabi frequency to the tunneling rate between cavities exceeds a critical value. We determine the critical value as a function of the quasimomentum quantum number, and indicate that the bound states carry a strong correlation in which the two polaritons appear to be spatially confined together.

Complicated and messy politics of inclusion: Michfest and the Boston Dyke March.

PubMed

Trigilio, Jo

2016-01-01

To illustrate the challenge of political organizing that grapples with identity politics and inclusion, I focus on two women-centered annual events with very different politics of inclusion: the Michigan Womyn's Music Festival and the Boston Dyke March. (1) arguments made by marginalized people for inclusion into established oppressed identity groups must be constructed with due care to avoid further marginalizing yet other liminal identities; (2) protesting/boycotting other oppressed groups for the purpose of achieving inclusion is often a problematic strategy; (3) the most effective strategy for honoring all people is to support organizations committed to the ideal of inclusion.

Broad accommodation of rift-related extension recorded by dyke intrusion in Saudi Arabia

USGS Publications Warehouse

Pallister, J.S.; McCausland, W.A.; Jonsson, Sigurjon; Lu, Z.; Zahran, H.M.; El, Hadidy S.; Aburukbah, A.; Stewart, I.C.F.; Lundgren, P.R.; White, R.A.; Moufti, M.R.H.

2010-01-01

The extensive harrat lava province of Arabia formed during the past 30 million years in response to Red Sea rifting and mantle upwelling. The area was regarded as seismically quiet, but between April and June 2009 a swarm of more than 30,000 earthquakes struck one of the lava fields in the province, Harrat Lunayyir, northwest Saudi Arabia. Concerned that larger damaging earthquakes might occur, the Saudi Arabian government evacuated 40,000 people from the region. Here we use geologic, geodetic and seismic data to show that the earthquake swarm resulted from magmatic dyke intrusion. We document a surface fault rupture that is 8 km long with 91 cm of offset. Surface deformation is best modelled by the shallow intrusion of a north-west trending dyke that is about 10 km long. Seismic waves generated during the earthquakes exhibit overlapping very low- and high-frequency components. We interpret the low frequencies to represent intrusion of magma and the high frequencies to represent fracturing of the crystalline basement rocks. Rather than extension being accommodated entirely by the central Red Sea rift axis, we suggest that the broad deformation observed in Harrat Lunayyir indicates that rift margins can remain as active sites of extension throughout rifting. Our analyses allowed us to forecast the likelihood of a future eruption or large earthquake in the region and informed the decisions made by the Saudi Arabian government to return the evacuees.

Interaction-induced effects on Bose-Hubbard parameters

NASA Astrophysics Data System (ADS)

Kremer, Mark; Sachdeva, Rashi; Benseny, Albert; Busch, Thomas

2017-12-01

We study the effects of repulsive on-site interactions on the broadening of the localized Wannier functions used for calculating the parameters to describe ultracold atoms in optical lattices. For this, we replace the common single-particle Wannier functions, which do not contain any information about the interactions, by two-particle Wannier functions obtained from an exact solution which takes the interactions into account. We then use these interaction-dependent basis functions to calculate the Bose-Hubbard model parameters, showing that they are substantially different both at low and high lattice depths from the ones calculated using single-particle Wannier functions. Our results suggest that density effects are not negligible for many parameter ranges and need to be taken into account in metrology experiments.

Geochemistry of a Triassic dyke swarm in the North Patagonian Massif, Argentina. Implications for a postorogenic event of the Permian Gondwanide orogeny

NASA Astrophysics Data System (ADS)

González, Santiago N.; Greco, Gerson A.; González, Pablo D.; Sato, Ana M.; Llambías, Eduardo J.; Varela, Ricardo

2016-10-01

Permo-Triassic magmatism is widespread in the eastern North Patagonian Massif and has been related to the Gondwanide orogeny. Although a magmatic arc setting is widely accepted for the Permian plutonic rocks, the origin and geotectonic setting for the Triassic plutonic and volcanic rocks are still unknown. A NW-SE Triassic dyke swarm composed of andesites and latites with minor rhyolites was previously described in the Sierra Grande - Rincon de Paileman area. The dyke swarm was associated with extensional tectonics which was linked to a postorogenic process. In this paper we present new geochemical data of the rocks that form the swarm. Trachyandesites and rhyolites were separated based on their geochemical characteristics. Both groups may be considered originated from different sources. On the other hand, the content of incompatible elements (LILE and HFSE) indicates a strong relation between the swarm and an active continental margin. The samples also show a transitional signature between continental-arc and postcollisional or anorogenic settings. The new geochemical data on the dyke swarm support the idea of a magmatism that was linked to a postorogenic extensional tectonic regime related to a continental magmatic arc. Such an extension started in the Paleopacific margin of Pangea during the Anisian and might indicate the beginning of the Pangea break-up.

Coulomb matrix elements in multi-orbital Hubbard models.

PubMed

Bünemann, Jörg; Gebhard, Florian

2017-04-26

Coulomb matrix elements are needed in all studies in solid-state theory that are based on Hubbard-type multi-orbital models. Due to symmetries, the matrix elements are not independent. We determine a set of independent Coulomb parameters for a d-shell and an f-shell and all point groups with up to 16 elements (O h , O, T d , T h , D 6h , and D 4h ). Furthermore, we express all other matrix elements as a function of the independent Coulomb parameters. Apart from the solution of the general point-group problem we investigate in detail the spherical approximation and first-order corrections to the spherical approximation.

Fidelity Study of Superconductivity in Extended Hubbard Models

NASA Astrophysics Data System (ADS)

Plonka, Nachum; Jia, Chunjing; Moritz, Brian; Wang, Yao; Devereaux, Thomas

2015-03-01

The role of strong electronic correlations on unconventional superconductivity remains an important open question. Here, we explore the influence of long-range Coulomb interactions, present in real material systems, through nearest and next-nearest neighbor extended Hubbard interactions in addition to the usual on-site terms. Utilizing large scale, numerical exact diagonalization, we analyze the signatures of superconductivity in the ground states through the fidelity metric of quantum information theory. We find that these extended interactions enhance charge fluctuations with various wave vectors. These suppress superconductivity in general, but in certain parameter regimes superconductivity is sustained. This has implications for tuning extended interactions in real materials.

Probing the Bond Order Wave Phase Transitions of the Ionic Hubbard Model by Superlattice Modulation Spectroscopy

NASA Astrophysics Data System (ADS)

Loida, Karla; Bernier, Jean-Sébastien; Citro, Roberta; Orignac, Edmond; Kollath, Corinna

2017-12-01

An exotic phase, the bond order wave, characterized by the spontaneous dimerization of the hopping, has been predicted to exist sandwiched between the band and Mott insulators in systems described by the ionic Hubbard model. Despite growing theoretical evidence, this phase still evades experimental detection. Given the recent realization of the ionic Hubbard model in ultracold atomic gases, we propose here to detect the bond order wave using superlattice modulation spectroscopy. We demonstrate, with the help of time-dependent density-matrix renormalization group and bosonization, that this spectroscopic approach reveals characteristics of both the Ising and Kosterlitz-Thouless transitions signaling the presence of the bond order wave phase. This scheme also provides insights into the excitation spectra of both the band and Mott insulators.

Lower bounds for the ground state energy for the PPP and Hubbard models of the benzene molecule

NASA Astrophysics Data System (ADS)

Číẑek, J.; Vinette, F.

1988-09-01

The optimized inner projection (OIP) technique, which is equivalent to the method of intermediate Hamiltonians (MIH), is applied to the PPP and Hubbard models of the benzene molecule. Both these methods are applicable since the electrostatic part of the PPP and Hubbard Hamiltonians is positive definite. Lower energy bounds are calculated using OIP and MIH for all values of the resonance integral β. In this study, β plays the role of a coupling constant. The deviation of the OIP results from exact ones is smaller than 7% for all values of β. The OIP results are also compared with the correlation energies obtained by other techniques. The OIP method gives surprisingly good results even for small |β| values.

Pairing phase diagram of three holes in the generalized Hubbard model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Navarro, O.; Espinosa, J.E.

Investigations of high-{Tc} superconductors suggest that the electronic correlation may play a significant role in the formation of pairs. Although the main interest is on the physic of two-dimensional highly correlated electron systems, the one-dimensional models related to high temperature superconductivity are very popular due to the conjecture that properties of the 1D and 2D variants of certain models have common aspects. Within the models for correlated electron systems, that attempt to capture the essential physics of high-temperature superconductors and parent compounds, the Hubbard model is one of the simplest. Here, the pairing problem of a three electrons system hasmore » been studied by using a real-space method and the generalized Hubbard Hamiltonian. This method includes the correlated hopping interactions as an extension of the previously proposed mapping method, and is based on mapping the correlated many body problem onto an equivalent site- and bond-impurity tight-binding one in a higher dimensional space, where the problem was solved in a non-perturbative way. In a linear chain, the authors analyzed the pairing phase diagram of three correlated holes for different values of the Hamiltonian parameters. For some value of the hopping parameters they obtain an analytical solution for all kind of interactions.« less

Dyke-Davidoff-Masson Syndrome. An unusual cause of status epilepticus.

PubMed

Zawar, Ifrah; Khan, Ashfa A; Sultan, Tipu; Rathore, Ahsan W

2015-10-01

The Dyke-Davidoff-Masson Syndrome (DDMS) results from an insult to the growing brain in utero or early infancy, which lead to loss of neurons compromising the growth of the brain. Clinical presentation includes seizures, hemiparesis, facial asymmetry, and learning disability. Radiological findings include cerebral atrophy on one side. Here, we present a case with status epilepticus who had underlying DDMS. It is a rare syndrome and uncommon cause for status epilepticus. Infections of CNS, hypoxic ischemic encephalopathy, intracranial bleed, trauma, congenital vascular malformations are the common causes of this syndrome. Diagnosis is established after clinical history, examination, and MRI. Intractable seizures can be controlled with appropriate anticonvulsants. Subsequently, these children may require physiotherapy, speech therapy, and occupational therapy in addition to the anticonvulsant medication. Outcome is better if the seizures are controlled.

Detection of Antiferromagnetic Correlations in the Fermi-Hubbard Model

NASA Astrophysics Data System (ADS)

Hulet, Randall

2014-05-01

The Hubbard model, consisting of a cubic lattice with on-site interactions and kinetic energy arising from tunneling to nearest neighbors is a ``standard model'' of strongly correlated many-body physics, and it may also contain the essential ingredients of high-temperature superconductivity. While the Hamiltonian has only two terms it cannot be numerically solved for arbitrary density of spin-1/2 fermions due to exponential growth in the basis size. At a density of one spin-1/2 particle per site, however, the Hubbard model is known to exhibit antiferromagnetism at temperatures below the Néel temperature TN, a property shared by most of the undoped parent compounds of high-Tc superconductors. The realization of antiferromagnetism in a 3D optical lattice with atomic fermions has been impeded by the inability to attain sufficiently low temperatures. We have developed a method to perform evaporative cooling in a 3D cubic lattice by compensating the confinement envelope of the infrared optical lattice beams with blue-detuned laser beams. Evaporation can be controlled by the intensity of these non-retroreflected compensating beams. We observe significantly lower temperatures of a two-spin component gas of 6Li atoms in the lattice using this method. The cooling enables us to detect the development of short-range antiferromagnetic correlations using spin-sensitive Bragg scattering of light. Comparison with quantum Monte Carlo constrains the temperature in the lattice to 2-3 TN. We will discuss the prospects of attaining even lower temperatures with this method. Supported by DARPA/ARO, ONR, and NSF.

Random phase approximation and cluster mean field studies of hard core Bose Hubbard model

NASA Astrophysics Data System (ADS)

Alavani, Bhargav K.; Gaude, Pallavi P.; Pai, Ramesh V.

2018-04-01

We investigate zero temperature and finite temperature properties of the Bose Hubbard Model in the hard core limit using Random Phase Approximation (RPA) and Cluster Mean Field Theory (CMFT). We show that our RPA calculations are able to capture quantum and thermal fluctuations significantly better than CMFT.

The self-trapping transition in the non-half-filled strongly correlated extended Holstein-Hubbard model in two-dimensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sankar, I. V., E-mail: ivshankar27@gmail.com; Chatterjee, Ashok, E-mail: ivshankar27@gmail.com

2014-04-24

The two-dimensional extended Holstein-Hubbard model (EHH) has been considered at strong correlation regime in the non-half-filled band case to understand the self-trapping transition of electrons in strongly correlated electron system. We have used the method of optimized canonical transformations to transform an EHH model into an effective extended Hubbard (EEH) model. In the strong on-site correlation limit an EH model can be transformed into a t-J model which is finally solved using Hartree-Fock approximation (HFA). We found that, for non-half-filled band case, the transition is abrupt in the adiabatic region whereas it is continuous in the anti-adiabatic region.

Determinant quantum Monte Carlo study of the two-dimensional single-band Hubbard-Holstein model

DOE PAGES

Johnston, S.; Nowadnick, E. A.; Kung, Y. F.; ...

2013-06-24

Here, we performed numerical studies of the Hubbard-Holstein model in two dimensions using determinant quantum Monte Carlo (DQMC). We also present details of the method, emphasizing the treatment of the lattice degrees of freedom, and then study the filling and behavior of the fermion sign as a function of model parameters. We find a region of parameter space with large Holstein coupling where the fermion sign recovers despite large values of the Hubbard interaction. This indicates that studies of correlated polarons at finite carrier concentrations are likely accessible to DQMC simulations. We then restrict ourselves to the half-filled model andmore » examine the evolution of the antiferromagnetic structure factor, other metrics for antiferromagnetic and charge-density-wave order, and energetics of the electronic and lattice degrees of freedom as a function of electron-phonon coupling. From this we find further evidence for a competition between charge-density-wave and antiferromagnetic order at half- filling.« less

Glaciological and marine geological controls on terminus dynamics of Hubbard Glacier, southeast Alaska

USGS Publications Warehouse

Stearns, Leigh A.; Hamilton, Gordon S.; van der Veen, C. J.; Finnegan, D. C.; O'Neel, Shad; Scheick, J. B.; Lawson, D. E.

2015-01-01

Hubbard Glacier, located in southeast Alaska, is the world's largest non-polar tidewater glacier. It has been steadily advancing since it was first mapped in 1895; occasionally, the advance creates an ice or sediment dam that blocks a tributary fjord (Russell Fiord). The sustained advance raises the probability of long-term closure in the near-future, which will strongly impact the ecosystem of Russell Fiord and the nearby community of Yakutat. Here, we examine a 43-year record of flow speeds and terminus position to understand the large-scale dynamics of Hubbard Glacier. Our long-term record shows that the rate of terminus advance has increased slightly since 1895, with the exception of a slowed advance between approximately 1972 and 1984. The short-lived closure events in 1986 and 2002 were not initiated by perturbations in ice velocity or environmental forcings, but were likely due to fluctuations in sedimentation patterns at the terminus. This study points to the significance of a coupled system where short-term velocity fluctuations and morainal shoal development control tidewater glacier terminus position.

Atomic Bose-Hubbard Systems with Single-Particle Control

NASA Astrophysics Data System (ADS)

Preiss, Philipp Moritz

Experiments with ultracold atoms in optical lattices provide outstanding opportunities to realize exotic quantum states due to a high degree of tunability and control. In this thesis, I present experiments that extend this control from global parameters to the level of individual particles. Using a quantum gas microscope for 87Rb, we have developed a single-site addressing scheme based on digital amplitude holograms. The system self-corrects for aberrations in the imaging setup and creates arbitrary beam profiles. We are thus able to shape optical potentials on the scale of single lattice sites and control the dynamics of individual atoms. We study the role of quantum statistics and interactions in the Bose-Hubbard model on the fundamental level of two particles. Bosonic quantum statistics are apparent in the Hong-Ou-Mandel interference of massive particles, which we observe in tailored double-well potentials. These underlying statistics, in combination with tunable repulsive interactions, dominate the dynamics in single- and two-particle quantum walks. We observe highly coherent position-space Bloch oscillations, bosonic bunching in Hanbury Brown-Twiss interference and the fermionization of strongly interacting bosons. Many-body states of indistinguishable quantum particles are characterized by large-scale spatial entanglement, which is difficult to detect in itinerant systems. Here, we extend the concept of Hong-Ou-Mandel interference from individual particles to many-body states to directly quantify entanglement entropy. We perform collective measurements on two copies of a quantum state and detect entanglement entropy through many-body interference. We measure the second order Renyi entropy in small Bose-Hubbard systems and detect the buildup of spatial entanglement across the superfluid-insulator transition. Our experiments open new opportunities for the single-particle-resolved preparation and characterization of many-body quantum states.

Monte Carlo calculation of dynamical properties of the two-dimensional Hubbard model

NASA Technical Reports Server (NTRS)

White, S. R.; Scalapino, D. J.; Sugar, R. L.; Bickers, N. E.

1989-01-01

A new method is introduced for analytically continuing imaginary-time data from quantum Monte Carlo calculations to the real-frequency axis. The method is based on a least-squares-fitting procedure with constraints of positivity and smoothness on the real-frequency quantities. Results are shown for the single-particle spectral-weight function and density of states for the half-filled, two-dimensional Hubbard model.

Petrology, geochronology and emplacement model of the giant 1.37 Ga arcuate Lake Victoria Dyke Swarm on the margin of a large igneous province in eastern Africa

NASA Astrophysics Data System (ADS)

Mäkitie, Hannu; Data, Gabriel; Isabirye, Edward; Mänttäri, Irmeli; Huhma, Hannu; Klausen, Martin B.; Pakkanen, Lassi; Virransalo, Petri

2014-09-01

A comprehensive description of the petrography, geochemical composition, Sm-Nd data and intrinsic field relationships of a giant arcuate Mesoproterozoic mafic dyke swarm in SW Uganda is presented for the first time. The swarm is ∼100 km wide and mainly hosted in the Palaeoproterozoic Rwenzori Belt between the Mesoproterozoic Karagwe-Ankole Belt and the Archaean Uganda Block. The dykes trend NW-SE across Uganda, but can be correlated across Lake Victoria to another set of arcuate aeromagnetic anomalies that continue southwards into Tanzania, resulting in a remarkably large semi-circular swarm with an outer diameter of ∼500 km. We propose that this unique giant dyke structure be named the Lake Victoria Dyke Swarm (LVDS). The dykes are tholeiites with Mg numbers between 0.69 and 0.44, and with inherited marked negative Nb and P anomalies in spider diagrams. Two dykes provide Sm-Nd mineral ages of 1368 ± 41 Ma and 1374 ± 42 Ma, with initial εNd values of -2.3 and -3.2, and 87Sr/86Sr ratios of ∼0.706-0.709. Geotectonic discrimination diagrams for the swarm exhibit more arc type than within-plate tectonic signatures, but this is in accordance with systematic enrichments in LREE, U and Th in the dolerites, more likely due to the involvement of the continental lithosphere during their petrogenesis. The LVDS is coeval with a regional ∼1375 Ma bimodal magmatic event across nearby Burundi, Rwanda and NW Tanzania, which can collectively be viewed as a large igneous province (LIP). It also indicates that the nearby Karagwe-Ankole Belt sequences - bracketed between 1.78 and 1.37 Ga and assumed by some to have been deposited within intracratonic basins - were capped by flood basalts that have subsequently been removed by erosion. Different geochemical signatures (e.g. LaN/SmN) suggest that most of the arcuate swarm was derived from an enriched SCLM, whereas related intrusions in the centre of this semi-circular segment have more or less enriched asthenospheric mantle

Petrogenesis of Cretaceous (133-84 Ma) intermediate dykes and host granites in southeastern China: Implications for lithospheric extension, continental crustal growth, and geodynamics of Palaeo-Pacific subduction

NASA Astrophysics Data System (ADS)

Yang, Jinbao; Zhao, Zhidan; Hou, Qingye; Niu, Yaoling; Mo, Xuanxue; Sheng, Dan; Wang, Lili

2018-01-01

This paper presents U-Pb zircon geochronology, petrology, and major and trace element, Sr-Nd and zircon Hf isotopic geochemistry of Cretaceous granites and intermediate dykes in the Quanzhou and Xiamen regions of southeastern China. These data are used to investigate igneous petrogenesis and Cretaceous tectonic evolution, and interpret the geodynamics of Palaeo-Pacific slab subduction. Granites in Quanzhou and Xiamen range in age from 133 Ma to 87 Ma, have high SiO2 and K2O contents, low abundances in P2O5, and an A/CNK index that ranges from 0.97 to 1.09, indicating that they are high-K calc-alkaline metaluminous I-type rocks. Slightly negative ɛ Nd (t) values (- 1.2 to - 4.4), young Nd model ages (0.87 Ga to 1.20 Ga) and positive ɛ Hf (t) values (- 0.5 to + 9.9) of zircon grains indicate that the granites were derived from magmas that melted amphibolite in the middle-lower crust, and which may have assimilated country rocks during emplacement in shallow chambers. The intermediate dykes have no genetic link to the granites and magma mixing was negligible. Eight dyke samples have low SiO2 and high MgO, Ni and Cr contents. Negative ε Nd (t) values (- 1.5 to - 2.7) and positive ε Hf (t) values (2.7 to 7.6) suggest that the dykes were derived from residual basic lower crust after mafic-crystal accumulation. Two samples of adakite-like dykes are characterised by high Sr/Y ratios (89 to 100) and high SiO2, low K2O, Ni, Cr contents. In combination with slightly negative ε Nd (t) values (- 1.7 to - 1.8) and positive ε Hf (t) values (2.9 to 4.3), the adakite-like dykes were derived from cumulate basic lower crust which had a mixed source between depleted mantle- and crust-derived melts. Based on our data, combined with previously published work, we suggest that extension-induced middle-lower crustal melting and underplating of mantle-derived basaltic melts were the principal driving mechanisms for Cretaceous granitic magmatism in coastal Fujian Province. Extension

Comparisons with results from the Hubbard Brook Experimental Forest in the Northern Appalachians

Treesearch

James Hornbeck; Amey S. Bailey; Christopher Eagar; John L. Campbell

2014-01-01

The Hubbard Brook Experimental Forest (HBEF) is located in central New Hampshire, in the heart of the White Mountains, toward the northern end of the Appalachian chain. HBEF was established in 1955, two decades after Coweeta Hydrologic Laboratory (CHL), but research objectives at both sites have long been similar, that is, to understand hydrologic and nutrient cycling...

Conductivite dans le modele de Hubbard bi-dimensionnel a faible couplage

NASA Astrophysics Data System (ADS)

Bergeron, Dominic

Le modele de Hubbard bi-dimensionnel (2D) est souvent considere comme le modele minimal pour les supraconducteurs a haute temperature critique a base d'oxyde de cuivre (SCHT). Sur un reseau carre, ce modele possede les phases qui sont communes a tous les SCHT, la phase antiferromagnetique, la phase supraconductrice et la phase dite du pseudogap. Il n'a pas de solution exacte, toutefois, plusieurs methodes approximatives permettent d'etudier ses proprietes de facon numerique. Les proprietes optiques et de transport sont bien connues dans les SCHT et sont donc de bonne candidates pour valider un modele theorique et aider a comprendre mieux la physique de ces materiaux. La presente these porte sur le calcul de ces proprietes pour le modele de Hubbard 2D a couplage faible ou intermediaire. La methode de calcul utilisee est l'approche auto-coherente a deux particules (ACDP), qui est non-perturbative et inclue l'effet des fluctuations de spin et de charge a toutes les longueurs d'onde. La derivation complete de l'expression de la conductivite dans l'approche ACDP est presentee. Cette expression contient ce qu'on appelle les corrections de vertex, qui tiennent compte des correlations entre quasi-particules. Pour rendre possible le calcul numerique de ces corrections, des algorithmes utilisant, entre autres, des transformees de Fourier rapides et des splines cubiques sont developpes. Les calculs sont faits pour le reseau carre avec sauts aux plus proches voisins autour du point critique antiferromagnetique. Aux dopages plus faibles que le point critique, la conductivite optique presente une bosse dans l'infrarouge moyen a basse temperature, tel qu'observe dans plusieurs SCHT. Dans la resistivite en fonction de la temperature, on trouve un comportement isolant dans le pseudogap lorsque les corrections de vertex sont negligees et metallique lorsqu'elles sont prises en compte. Pres du point critique, la resistivite est lineaire en T a basse temperature et devient

Unified one-band Hubbard model for magnetic and electronic spectra of the parent compounds of cuprate superconductors

NASA Astrophysics Data System (ADS)

Dalla Piazza, B.; Mourigal, M.; Guarise, M.; Berger, H.; Schmitt, T.; Zhou, K. J.; Grioni, M.; Rønnow, H. M.

2012-03-01

Using low-energy projection of the one-band t-t'-t'' Hubbard model we derive an effective spin Hamiltonian and its spin-wave expansion to order 1/S. We fit the spin-wave dispersion of several parent compounds to the high-temperature superconducting cuprates La2CuO4, Sr2CuO2Cl2, and Bi2Sr2YCu2O8. Our accurate quantitative determination of the one-band Hubbard model parameters allows prediction and comparison to experimental results. Among those we discuss the two-magnon Raman peak line shape, the K-edge resonant inelastic x-ray scattering 500-meV peak, and the high-energy kink in the angle-resolved photoemission spectroscopy quasiparticle dispersion, also known as the waterfall feature.

Modeling ecohydrologic processes at Hubbard Brook: Initial results for Watershed 6 stream discharge and chemistry

EPA Science Inventory

The Hubbard Brook Long Term Ecological Research site has produced some of the most extensive and long-running databases on the hydrology, biology and chemistry of forest ecosystem responses to climate and forest harvest. We used these long-term databases to calibrate and apply G...

Multimode Bose-Hubbard model for quantum dipolar gases in confined geometries

NASA Astrophysics Data System (ADS)

Cartarius, Florian; Minguzzi, Anna; Morigi, Giovanna

2017-06-01

We theoretically consider ultracold polar molecules in a wave guide. The particles are bosons: They experience a periodic potential due to an optical lattice oriented along the wave guide and are polarized by an electric field orthogonal to the guide axis. The array is mechanically unstable by opening the transverse confinement in the direction orthogonal to the polarizing electric field and can undergo a transition to a double-chain (zigzag) structure. For this geometry we derive a multimode generalized Bose-Hubbard model for determining the quantum phases of the gas at the mechanical instability, taking into account the quantum fluctuations in all directions of space. Our model limits the dimension of the numerically relevant Hilbert subspace by means of an appropriate decomposition of the field operator, which is obtained from a field theoretical model of the linear-zigzag instability. We determine the phase diagrams of small systems using exact diagonalization and find that, even for tight transverse confinement, the aspect ratio between the two transverse trap frequencies controls not only the classical but also the quantum properties of the ground state in a nontrivial way. Convergence tests at the linear-zigzag instability demonstrate that our multimode generalized Bose-Hubbard model can catch the essential features of the quantum phases of dipolar gases in confined geometries with a limited computational effort.

INTERIOR SECOND FLOOR EAST END LOOKING WEST AT NORTH ROW ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

INTERIOR SECOND FLOOR- EAST END LOOKING WEST AT NORTH ROW OF MUSHROOM COLUMNS. - Colt Fire Arms Company, South Armory Building, 36-150 Huyshope Avenue, 17-170 Van Dyke Avenue, 49 Vredendale Avenue, Hartford, Hartford County, CT

Filling-driven Mott transition in SU(N ) Hubbard models

NASA Astrophysics Data System (ADS)

Lee, Seung-Sup B.; von Delft, Jan; Weichselbaum, Andreas

2018-04-01

We study the filling-driven Mott transition involving the metallic and paramagnetic insulating phases in SU (N ) Fermi-Hubbard models, using the dynamical mean-field theory and the numerical renormalization group as its impurity solver. The compressibility shows a striking temperature dependence: near the critical end-point temperature, it is strongly enhanced in the metallic phase close to the insulating phase. We demonstrate that this compressibility enhancement is associated with the thermal suppression of the quasiparticle peak in the local spectral functions. We also explain that the asymmetric shape of the quasiparticle peak originates from the asymmetry in the dynamics of the generalized doublons and holons.

Critical slowing down in driven-dissipative Bose-Hubbard lattices

NASA Astrophysics Data System (ADS)

Vicentini, Filippo; Minganti, Fabrizio; Rota, Riccardo; Orso, Giuliano; Ciuti, Cristiano

2018-01-01

We explore theoretically the dynamical properties of a first-order dissipative phase transition in coherently driven Bose-Hubbard systems, describing, e.g., lattices of coupled nonlinear optical cavities. Via stochastic trajectory calculations based on the truncated Wigner approximation, we investigate the dynamical behavior as a function of system size for one-dimensional (1D) and 2D square lattices in the regime where mean-field theory predicts nonlinear bistability. We show that a critical slowing down emerges for increasing number of sites in 2D square lattices, while it is absent in 1D arrays. We characterize the peculiar properties of the collective phases in the critical region.

Nonlocal correlations in the orbital selective Mott phase of a one-dimensional multiorbital Hubbard model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, S.; Kaushal, N.; Wang, Y.

Here, we study nonlocal correlations in a three-orbital Hubbard model defined on an extended one-dimensional chain using determinant quantum Monte Carlo and density matrix renormalization group methods. We focus on a parameter regime with robust Hund's coupling, which produces an orbital selective Mott phase (OSMP) at intermediate values of the Hubbard U, as well as an orbitally ordered ferromagnetic insulating state at stronger coupling. An examination of the orbital- and spin-correlation functions indicates that the orbital ordering occurs before the onset of magnetic correlations in this parameter regime as a function of temperature. In the OSMP, we find that themore » self-energy for the itinerant electrons is momentum dependent, indicating a degree of nonlocal correlations while the localized electrons have largely momentum independent self-energies. These nonlocal correlations also produce relative shifts of the holelike and electronlike bands within our model. The overall momentum dependence of these quantities is strongly suppressed in the orbitally ordered insulating phase.« less

Nonlocal correlations in the orbital selective Mott phase of a one-dimensional multiorbital Hubbard model

DOE PAGES

Li, S.; Kaushal, N.; Wang, Y.; ...

2016-12-12

Here, we study nonlocal correlations in a three-orbital Hubbard model defined on an extended one-dimensional chain using determinant quantum Monte Carlo and density matrix renormalization group methods. We focus on a parameter regime with robust Hund's coupling, which produces an orbital selective Mott phase (OSMP) at intermediate values of the Hubbard U, as well as an orbitally ordered ferromagnetic insulating state at stronger coupling. An examination of the orbital- and spin-correlation functions indicates that the orbital ordering occurs before the onset of magnetic correlations in this parameter regime as a function of temperature. In the OSMP, we find that themore » self-energy for the itinerant electrons is momentum dependent, indicating a degree of nonlocal correlations while the localized electrons have largely momentum independent self-energies. These nonlocal correlations also produce relative shifts of the holelike and electronlike bands within our model. The overall momentum dependence of these quantities is strongly suppressed in the orbitally ordered insulating phase.« less

Fulde-Ferrell-Larkin-Ovchinnikov correlation and free fluids in the one-dimensional attractive Hubbard model

NASA Astrophysics Data System (ADS)

Cheng, Song; Yu, Yi-Cong; Batchelor, M. T.; Guan, Xi-Wen

2018-03-01

In this Rapid Communication, we show that low-energy macroscopic properties of the one-dimensional (1D) attractive Hubbard model exhibit two fluids of bound pairs and of unpaired fermions. Using the thermodynamic Bethe ansatz equations of the model, we first determine the low-temperature phase diagram and analytically calculate the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing correlation function for the partially polarized phase. We then show that for such an FFLO-like state in the low-density regime the effective chemical potentials of bound pairs and unpaired fermions behave like two free fluids. Consequently, the susceptibility, compressibility, and specific heat obey simple additivity rules, indicating the "free" particle nature of interacting fermions on a 1D lattice. In contrast to the continuum Fermi gases, the correlation critical exponents and thermodynamics of the attractive Hubbard model essentially depend on two lattice interacting parameters. Finally, we study scaling functions, the Wilson ratio and susceptibility, which provide universal macroscopic properties and dimensionless constants of interacting fermions at low energy.

Influence of spin and charge fluctuations on spectra of the two-dimensional Hubbard model

NASA Astrophysics Data System (ADS)

Sherman, A.

2018-05-01

The influence of spin and charge fluctuations on spectra of the two-dimensional fermionic Hubbard model is considered using the strong coupling diagram technique. Infinite sequences of diagrams containing ladder inserts, which describe the interaction of electrons with these fluctuations, are summed, and obtained equations are self-consistently solved for the ranges of Hubbard repulsions , temperatures and electron concentrations with t the intersite hopping constant. For all considered U the system exhibits a transition to the long-range antiferromagnetic order at . At the same time no indication of charge ordering is observed. Obtained solutions agree satisfactorily with results of other approaches and obey moments sum rules. In the considered region of the U-T plane, the curve separating metallic solutions passes from at the highest temperatures to U  =  2t at for half-filling. If only short-range fluctuations are allowed for the remaining part of this region is occupied by insulating solutions. Taking into account long-range fluctuations leads to strengthening of maxima tails, which transform a part of insulating solutions into bad-metal states. For low T, obtained results allow us to trace the gradual transition from the regime of strong correlations with the pronounced four-band structure and well-defined Mott gap for to the Slater regime of weak correlations with the spectral intensity having a dip along the boundary of the magnetic Brillouin zone due to an antiferromagnetic ordering for . For and doping leads to the occurrence of a pseudogap near the Fermi level, which is a consequence of the splitting out of a narrow band from a Hubbard subband. Obtained spectra feature waterfalls and Fermi arcs, which are similar to those observed in hole-doped cuprates.

Analysis of the deconstruction of Dyke Marsh, George Washington Memorial Parkway, Virginia-Progression, geologic and manmade causes, and effective restoration scenarios

USGS Publications Warehouse

Litwin, Ronald J.; Smoot, Joseph P.; Pavich, Milan J.; Markewich, Helaine W.; Oberg, Erik; Helwig, Ben; Steury, Brent; Santucci, Vincent L.; Durika, Nancy J.; Rybicki, Nancy B.; Engelhardt, Katharina M.; Sanders, Geoffrey; Verardo, Stacey; Elmore, Andrew J.; Gilmer, Joseph

2011-01-01

Photoanalysis of time-sequence aerial photographs of Dyke Marsh enabled us to calculate shoreline erosion estimates for this marsh over 19 years (1987-2006), as well as to quantify overall marsh acreage for 6 calendar years spanning an ~70 year interval (1937-2006). Photo overlay of a historic map enabled us to extend our whole-marsh acreage calculations back to 1883. Both sets of analyses were part of a geologic framework study in support of current efforts by the National Park Service (NPS) to restore this urban wetland. Two time intervals were selected for our shoreline erosion analyses, based on image quality and availability: 1987 to 2002, and 2002 to 2006. The more recent time interval shows a marked increase in erosion in the southern part of Dyke Marsh, following a wave-induced breach of a small peninsula that had protected its southern shoreline. Field observations and analyses of annual aerial imagery between 1987 and 2006 revealed a progressive increase in wave-induced erosion that presently is deconstructing Hog Island Gut, the last significant tidal creek network within the Dyke Marsh. These photo analyses documented an overall average westward shoreline loss of 6.0 to 7.8 linear feet per year along the Potomac River during this 19-year time interval. Additionally, photographic evidence documented that lateral erosion now is capturing existing higher order tributaries in the Hog Island Gut. Wave-driven stream piracy is fragmenting the remaining marsh habitat, and therefore its connectivity, relatively rapidly, causing the effective mouth of the Hog Island Gut tidal network to retreat headward visibly over the past several decades. Based on our estimates of total marsh area in the Dyke Marsh derived from 1987 aerial imagery, as much as 12 percent of the central part of the marsh has eroded in the 19 year period we studied (or ~7.5 percent of the original ~78.8 acres of 1987 marshland). Shoreline loss estimates for marsh parcels north and south of our

INTERIOR FOURTH FLOOR, SOUTH HALF, LOOKING SOUTH. NOTE MUSHROOM COLUMNS ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

INTERIOR FOURTH FLOOR, SOUTH HALF, LOOKING SOUTH. NOTE MUSHROOM COLUMNS AND CEILING HAS WOODEN NAILERS. - Colt Fire Arms Company, North Armory, 36-150 Huyshope Avenue, 17-170 Van Dyke Avenue, 49 Vredendale Avenue, Hartford, Hartford County, CT

Asymptotic correlation functions and FFLO signature for the one-dimensional attractive Hubbard model

NASA Astrophysics Data System (ADS)

Cheng, Song; Jiang, Yuzhu; Yu, Yi-Cong; Batchelor, Murray T.; Guan, Xi-Wen

2018-04-01

We study the long-distance asymptotic behavior of various correlation functions for the one-dimensional (1D) attractive Hubbard model in a partially polarized phase through the Bethe ansatz and conformal field theory approaches. We particularly find the oscillating behavior of these correlation functions with spatial power-law decay, of which the pair (spin) correlation function oscillates with a frequency ΔkF (2 ΔkF). Here ΔkF = π (n↑ -n↓) is the mismatch in the Fermi surfaces of spin-up and spin-down particles. Consequently, the pair correlation function in momentum space has peaks at the mismatch k = ΔkF, which has been observed in recent numerical work on this model. These singular peaks in momentum space together with the spatial oscillation suggest an analog of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state in the 1D Hubbard model. The parameter β representing the lattice effect becomes prominent in critical exponents which determine the power-law decay of all correlation functions. We point out that the backscattering of unpaired fermions and bound pairs within their own Fermi points gives a microscopic origin of the FFLO pairing in 1D.

Hole Transport in the Upper Hubbard Band in Ge:Cu under Uniaxial Pressure

NASA Astrophysics Data System (ADS)

Walukiewicz, W.; Dubon, O. D.; Silvestri, H. H.; Haller, E. E.

1998-03-01

We have reported recently on a uniaxial stress induced transformation of the ground state of Cu triple acceptors in Ge from highly localized 1s^3 to the much more extended 1s^22s^1 configuration (O.D. Dubon et. al., Phys Rev Lett. 78, 3519, (1997)). We find that the transformation leads to a gigantic enhancement of the low temperature conductivity. The conductivity is due to hole transport in the upper Hubbard band formed by overcharged 1s^22s^2 states. We have calculated hole mobilities in this band assuming that the states in the upper Hubbard band can be treated in the optical approximation as normal extended states with a well-defined effective mass. We find that for Cu concentrations below 10^15 cm-3 the experimentally observed mobilities approach 10^6 cm^2/Vs. These very high mobilities can be explained by hole scattering from ionized and neutral impurity centers. At higher Cu concentrations we observe an onset of Anderson localization that manifests itself in a thermally activated low temperature mobility. This work was supported by US DOE under Contract No. DE-AC03-76SF00098.

Hydrodynamics of the VanA-type VanS histidine kinase: an extended solution conformation and first evidence for interactions with vancomycin

PubMed Central

Phillips-Jones, Mary K.; Channell, Guy; Kelsall, Claire J.; Hughes, Charlotte S.; Ashcroft, Alison E.; Patching, Simon G.; Dinu, Vlad; Gillis, Richard B.; Adams, Gary G.; Harding, Stephen E.

2017-01-01

VanA-type resistance to glycopeptide antibiotics in clinical enterococci is regulated by the VanSARA two-component signal transduction system. The nature of the molecular ligand that is recognised by the VanSA sensory component has not hitherto been identified. Here we employ purified, intact and active VanSA membrane protein (henceforth referred to as VanS) in analytical ultracentrifugation experiments to study VanS oligomeric state and conformation in the absence and presence of vancomycin. A combination of sedimentation velocity and sedimentation equilibrium in the analytical ultracentrifuge (SEDFIT, SEDFIT-MSTAR and MULTISIG analysis) showed that VanS in the absence of the ligand is almost entirely monomeric (molar mass M = 45.7 kDa) in dilute aqueous solution with a trace amount of high molar mass material (M ~ 200 kDa). The sedimentation coefficient s suggests the monomer adopts an extended conformation in aqueous solution with an equivalent aspect ratio of ~(12 ± 2). In the presence of vancomycin over a 33% increase in the sedimentation coefficient is observed with the appearance of additional higher s components, demonstrating an interaction, an observation consistent with our circular dichroism measurements. The two possible causes of this increase in s – either a ligand induced dimerization and/or compaction of the monomer are considered. PMID:28397853

The carbonatite-marble dykes of Abyan Province, Yemen Republic: the mixing of mantle and crustal carbonate materials revealed by isotope and trace element analysis

NASA Astrophysics Data System (ADS)

Le Bas, M. J.; Ba-Bttat, M. A. O.; Taylor, R. N.; Milton, J. A.; Windley, B. F.; Evins, P. M.

2004-09-01

Dykes of carbonate rocks, that cut gneisses in the Lowder-Mudiah area of southern Yemen, consist of dolomite and/or calcite with or without apatite, barite and monazite. Petrographic observations, mineralogical, XRF and ICP-MS analyses reveal that some of the carbonate rocks are derived from sedimentary protoliths, whereas others are magmatic calcio- and magnesio-carbonatites some of which are mineralized with barite-monazite. The interbanded occurrence and apparent contemporary emplacement of these different rock types within individual dykes, backed by Sr Nd isotope evidence, are interpreted to show that intrusion of mantle-derived carbonatite magma was accompanied by mobilization of crustal marbles. That took place some 840 Ma ago but the REE-mineralization is dated at ca. 400 Ma.

Fast trimers in a one-dimensional extended Fermi-Hubbard model

NASA Astrophysics Data System (ADS)

Dhar, A.; Törmä, P.; Kinnunen, J. J.

2018-04-01

We consider a one-dimensional two-component extended Fermi-Hubbard model with nearest-neighbor interactions and mass imbalance between the two species. We study the binding energy of trimers, various observables for detecting them, and expansion dynamics. We generalize the definition of the trimer gap to include the formation of different types of clusters originating from nearest-neighbor interactions. Expansion dynamics reveal rapidly propagating trimers, with speeds exceeding doublon propagation in the strongly interacting regime. We present a simple model for understanding this unique feature of the movement of the trimers, and we discuss the potential for experimental realization.

Multiple mobility edges in a 1D Aubry chain with Hubbard interaction in presence of electric field: Controlled electron transport

NASA Astrophysics Data System (ADS)

Saha, Srilekha; Maiti, Santanu K.; Karmakar, S. N.

2016-09-01

Electronic behavior of a 1D Aubry chain with Hubbard interaction is critically analyzed in presence of electric field. Multiple energy bands are generated as a result of Hubbard correlation and Aubry potential, and, within these bands localized states are developed under the application of electric field. Within a tight-binding framework we compute electronic transmission probability and average density of states using Green's function approach where the interaction parameter is treated under Hartree-Fock mean field scheme. From our analysis we find that selective transmission can be obtained by tuning injecting electron energy, and thus, the present model can be utilized as a controlled switching device.

Asymptotic localization in the Bose-Hubbard model

NASA Astrophysics Data System (ADS)

Bols, Alex; De Roeck, Wojciech

2018-02-01

We consider the Bose-Hubbard model. Our focus is on many-body localization, which was described by many authors in such models, even in the absence of disorder. Since our work is rigorous, and since we believe that the localization in this type of models is not strictly valid in the infinite-time limit, we necessarily restrict our study to "asymptotic localization" also known as "quasi-localization:" We prove that transport and thermalization are small beyond perturbation theory in the limit of large particle density. Our theorem takes the form of a many-body Nekhoroshev estimate. An interesting and new aspect of this model is the following: The localization cannot be inferred from a lack of hybridization between zero-hopping eigenstates. Naively speaking, all these eigenstates appear resonant and one has to move to a dressed basis to see the absence of resonances that are responsible for (quasi-)localization.

Contemporaneous alkaline and tholeiitic magmatism in the Ponta Grossa Arch, Paraná-Etendeka Magmatic Province: Constraints from U-Pb zircon/baddeleyite and 40Ar/39Ar phlogopite dating of the José Fernandes Gabbro and mafic dykes

NASA Astrophysics Data System (ADS)

Almeida, Vidyã V.; Janasi, Valdecir A.; Heaman, Larry M.; Shaulis, Barry J.; Hollanda, Maria Helena B. M.; Renne, Paul R.

2018-04-01

We report the first high-precision ID-TIMS U-Pb baddeleyite/zircon and 40Ar/39Ar step-heating phlogopite age data for diabase and lamprophyre dykes and a mafic intrusion (José Fernandes Gabbro) located within the Ponta Grossa Arch, Brazil, in order to constrain the temporal evolution between Early Cretaceous tholeiitic and alkaline magmatism of the Paraná-Etendeka Magmatic Province. U-Pb dates from chemically abraded zircon data yielded the best estimate for the emplacement ages of a high Ti-P-Sr basaltic dyke (133.9 ± 0.2 Ma), a dyke with basaltic andesite composition (133.4 ± 0.2 Ma) and the José Fernandes Gabbro (134.5 ± 0.1 Ma). A 40Ar/39Ar phlogopite step-heating age of 133.7 ± 0.1 Ma from a lamprophyre dyke is identical within error to the U-Pb age of the diabase dykes, indicating that tholeiitic and alkaline magmatism were coeval in the Ponta Grossa Arch. Although nearly all analysed fractions are concordant and show low analytical uncertainties (± 0.3-0.9 Ma for baddeleyite; 0.1-0.4 Ma for zircon; 2σ), Pb loss is observed in all baddeleyite fractions and in some initial zircon fractions not submitted to the most extreme chemical abrasion treatment. The resulting age spread may reflect intense and continued magmatic activity in the Ponta Grossa Arch.

Trapped surfaces and emergent curved space in the Bose-Hubbard model

NASA Astrophysics Data System (ADS)

Caravelli, Francesco; Hamma, Alioscia; Markopoulou, Fotini; Riera, Arnau

2012-02-01

A Bose-Hubbard model on a dynamical lattice was introduced in previous work as a spin system analogue of emergent geometry and gravity. Graphs with regions of high connectivity in the lattice were identified as candidate analogues of spacetime geometries that contain trapped surfaces. We carry out a detailed study of these systems and show explicitly that the highly connected subgraphs trap matter. We do this by solving the model in the limit of no back-reaction of the matter on the lattice, and for states with certain symmetries that are natural for our problem. We find that in this case the problem reduces to a one-dimensional Hubbard model on a lattice with variable vertex degree and multiple edges between the same two vertices. In addition, we obtain a (discrete) differential equation for the evolution of the probability density of particles which is closed in the classical regime. This is a wave equation in which the vertex degree is related to the local speed of propagation of probability. This allows an interpretation of the probability density of particles similar to that in analogue gravity systems: matter inside this analogue system sees a curved spacetime. We verify our analytic results by numerical simulations. Finally, we analyze the dependence of localization on a gradual, rather than abrupt, falloff of the vertex degree on the boundary of the highly connected region and find that matter is localized in and around that region.

Fluid Inclusion Study of Quartz Xenocrysts in Mafic Dykes from Kawant Area, Chhota Udaipur District, Gujarat, India

NASA Astrophysics Data System (ADS)

Randive, Kirtikumar; Hurai, Vratislav

2015-09-01

Unusual mafic dykes occur in the proximity of the Ambadongar Carbonatite Complex, Lower Narmada Valley, Gujarat, India. The dykes contain dense population of quartz xenocrysts within the basaltic matrix metasomatised by carbonate-rich fluids. Plagioclase feldspars, relict pyroxenes, chlorite, barite, rutile, magnetite, Fe-Ti oxides and glass were identified in the basaltic matrix. Quartz xenocrysts occur in various shapes and sizes and form an intricate growth pattern with carbonates. The xenocrysts are fractured and contain several types of primary and secondary, single phase and two-phase fluid inclusions. The two-phase inclusions are dominated by aqueous liquid, whereas the monophase inclusions are composed of carbonic gas and the aqueous inclusions homogenize to liquid between 226°C and 361°C. Majority of the inclusions are secondary in origin and are therefore unrelated to the crystallization of quartz. Moreover, the inclusions have mixed carbonic-aqueous compositions that inhibit their direct correlation with the crustal or mantle fluids. The composition of dilute CO2-rich fluids observed in the quartz xenocrysts appear similar to those exsolved during the final stages of evolution of the Amba Dongar carbonatites. However, the carbonates are devoid of fluid inclusions and therefore their genetic relation with the quartz xenocrysts cannot be established.

Matrix-valued Boltzmann equation for the nonintegrable Hubbard chain.

PubMed

Fürst, Martin L R; Mendl, Christian B; Spohn, Herbert

2013-07-01

The standard Fermi-Hubbard chain becomes nonintegrable by adding to the nearest neighbor hopping additional longer range hopping amplitudes. We assume that the quartic interaction is weak and investigate numerically the dynamics of the chain on the level of the Boltzmann type kinetic equation. Only the spatially homogeneous case is considered. We observe that the huge degeneracy of stationary states in the case of nearest neighbor hopping is lost and the convergence to the thermal Fermi-Dirac distribution is restored. The convergence to equilibrium is exponentially fast. However for small next-nearest neighbor hopping amplitudes one has a rapid relaxation towards the manifold of quasistationary states and slow relaxation to the final equilibrium state.

Co-colonization of vanA and vanB Enterococcus faecium of clonal complex 17 in a patient with bacteremia due to vanA E. faecium.

PubMed

Seol, Chang Ahn; Park, Jeong Su; Sung, Heungsup; Kim, Mi-Na

2014-06-01

A 53-year-old Vietnamese man with liver cirrhosis was transferred from a Vietnamese hospital to our tertiary care hospital in Korea in order to undergo a liver transplantation. Bacteremia due to vanA Enterococcus faecium was diagnosed, and stool surveillance cultures for vancomycin-resistant enterococci (VRE) were positive for both vanA and vanB E. faecium. Pulsed-field gel electrophoresis analysis revealed that the 2 vanA VRE isolates from the blood and stool were clonal, but the vanB VRE was unrelated to the vanA VRE. vanA and vanB VRE were ST64 and ST18, single-allele variations of clonal complex 17, respectively. This is the first case report of vanA VRE bacteremia in a Vietnamese patient and demonstrates the reemergence of vanB VRE since a single outbreak occurred 15years ago in Korea. The reemergence of vanB VRE emphasizes the importance of VRE genotyping to prevent the spread of new VRE strains. Copyright © 2014 Elsevier Inc. All rights reserved.

Ground-state fidelity and bipartite entanglement in the Bose-Hubbard model.

PubMed

Buonsante, P; Vezzani, A

2007-03-16

We analyze the quantum phase transition in the Bose-Hubbard model borrowing two tools from quantum-information theory, i.e., the ground-state fidelity and entanglement measures. We consider systems at unitary filling comprising up to 50 sites and show for the first time that a finite-size scaling analysis of these quantities provides excellent estimates for the quantum critical point. We conclude that fidelity is particularly suited for revealing a quantum phase transition and pinning down the critical point thereof, while the success of entanglement measures depends on the mechanisms governing the transition.

U-Pb baddeleyite ages and geochemistry of dolerite dykes in the Bas Drâa Inlier of the Anti-Atlas of Morocco: Newly identified 1380 Ma event in the West African Craton

NASA Astrophysics Data System (ADS)

El Bahat, Abdelhakim; Ikenne, Moha; Söderlund, Ulf; Cousens, Brian; Youbi, Nasrrddine; Ernst, Richard; Soulaimani, Abderrahmane; El Janati, M'hamed; Hafid, Ahmid

2013-08-01

In the Bas-Drâa Inlier (Anti-Atlas, Morocco), the Paleoproterozoic basement which is cut by the Ediacaran Taourgha granite is also crosscut by numerous dykes of a variety of trends, mostly of uncertain age. Two doleritic dykes are dated by the ID-TIMS U-Pb method on baddeleyite and yield emplacement ages of 1381 ± 8 Ma (MSWD = 0.84) and 1384 ± 6 Ma (MSWD = 1.4) determined for a N135°E and a N40°E trending dyke, respectively. These dates represent the first geochronological evidence of a Mesoproterozoic magmatic event in the Anti-Atlas. This magmatic event falls in the previously considered ca 1.7-1.0 Ga (Mesoproterozoic) gap in geological activity in the Anti-Atlas. The poorly dated Taghdout and Taarotihate sequences could represent remnants of the ca. 1380 Ma magmatism and rift-related sedimentation. The Mesoproterozoic sedimentary succession of the Atar Group in the Taoudeni basin (Mauritania) could also represent a good candidate for rift-related sedimentation but it postdates the 1380 Ma magmatic event by 270 Ma. The dated 1380 Ma dykes are transitional to mildly alkaline basalts, not unlike some Hawaiian lavas. However, these dykes have a distinct negative Nb anomaly (a common features in many Large Igneous Provinces, LIPs), and this requires interaction with the lithosphere. This interaction may have occurred at the level of the lithospheric mantle or the crust. These newly dated 1380 Ma dykes may converge to the north, speculatively suggesting a magmatic center (associated with a 1380 Ma mantle plume?) along the northern margin, and possibly linked to rifting and possible breakup on that margin, and also to a regional uplift that largely removed the evidence of a 1380 Ma cover sequence. Contemporaneous 1380-1390 Ma magmatism is reported elsewhere on other crustal blocks, and that in northeastern Laurentia (northern Greenland), northern Siberia (Anabar shield), and Baltica (southern Urals) can be reconstructed with that of the Bas Drâa Inlier (Anti

Hydrogen ion input to the Hubbard Brook Experimental Forest, New Hampshire, during the last decade

Treesearch

Gene E. Likens; F. Herbert Bormann; John S. Eaton; Robert S. Pierce; Noye M. Johnson

1976-01-01

Being downwind of eastern and midwestern industrial centers, the Hubbard Brook Experimental Forest offers a prime location to monitor long-term trends in atmospheric chemistry. Continuous measurements of precipitation chemistry during the last 10 years provide a measure of recent changes in precipitation inputs of hydrogen ion. The weighted average pH of precipitation...

Twisted Hubbard model for Sr2IrO4: magnetism and possible high temperature superconductivity.

PubMed

Wang, Fa; Senthil, T

2011-04-01

Sr(2)IrO(4) has been suggested as a Mott insulator from a single J(eff)=1/2 band, similar to the cuprates. However, this picture is complicated by the measured large magnetic anisotropy and ferromagnetism. Based on a careful mapping to the J(eff)=1/2 (pseudospin-1/2) space, we propose that the low energy electronic structure of Sr(2)IrO(4) can indeed be described by a SU(2) invariant pseudospin-1/2 Hubbard model very similar to that of the cuprates, but with a twisted coupling to an external magnetic field (a g tensor with a staggered antisymmetric component). This perspective naturally explains the magnetic properties of Sr(2)IrO(4). We also derive several simple facts based on this mapping and the known results about the Hubbard model and the cuprates, which may be tested in future experiments on Sr(2)IrO(4). In particular, we propose that (electron-)doping Sr(2)IrO(4) can potentially realize high-temperature superconductivity. © 2011 American Physical Society

Water age and stream solute dynamics at the Hubbard Brook Experimental Forest (US)

NASA Astrophysics Data System (ADS)

Botter, Gianluca; Benettin, Paolo; McGuire, Kevin; Rinaldo, Andrea

2016-04-01

The contribution discusses experimental and modeling results from a headwater catchment at the Hubbard Brook Experimental Forest (New Hampshire, USA) to explore the link between stream solute dynamics and water age. A theoretical framework based on water age dynamics, which represents a general basis for characterizing solute transport at the catchment scale, is used to model both conservative and weathering-derived solutes. Based on the available information about the hydrology of the site, an integrated transport model was developed and used to estimate the relevant hydrochemical fluxes. The model was designed to reproduce the deuterium content of streamflow and allowed for the estimate of catchment water storage and dynamic travel time distributions (TTDs). Within this framework, dissolved silicon and sodium concentration in streamflow were simulated by implementing first-order chemical kinetics based explicitly on dynamic TTD, thus upscaling local geochemical processes to catchment scale. Our results highlight the key role of water stored within the subsoil glacial material in both the short-term and long-term solute circulation at Hubbard Brook. The analysis of the results provided by the calibrated model allowed a robust estimate of the emerging concentration-discharge relationship, streamflow age distributions (including the fraction of event water) and storage size, and their evolution in time due to hydrologic variability.

Effects of interaction strength, doping, and frustration on the antiferromagnetic phase of the two-dimensional Hubbard model

NASA Astrophysics Data System (ADS)

Fratino, L.; Charlebois, M.; Sémon, P.; Sordi, G.; Tremblay, A.-M. S.

2017-12-01

Recent quantum-gas microscopy of ultracold atoms and scanning tunneling microscopy of the cuprates reveal new detailed information about doped Mott antiferromagnets, which can be compared with calculations. Using cellular dynamical mean-field theory, we map out the antiferromagnetic (AF) phase of the two-dimensional Hubbard model as a function of interaction strength U , hole doping δ , and temperature T . The Néel phase boundary is nonmonotonic as a function of U and δ . Frustration induced by second-neighbor hopping reduces Néel order more effectively at small U . The doped AF is stabilized at large U by kinetic energy and at small U by potential energy. The transition between the AF insulator and the doped metallic AF is continuous. At large U , we find in-gap states similar to those observed in scanning tunneling microscopy. We predict that, contrary to the Hubbard bands, these states are only slightly spin polarized.

Influence of spin and charge fluctuations on spectra of the two-dimensional Hubbard model.

PubMed

Sherman, A

2018-05-16

The influence of spin and charge fluctuations on spectra of the two-dimensional fermionic Hubbard model is considered using the strong coupling diagram technique. Infinite sequences of diagrams containing ladder inserts, which describe the interaction of electrons with these fluctuations, are summed, and obtained equations are self-consistently solved for the ranges of Hubbard repulsions [Formula: see text], temperatures [Formula: see text] and electron concentrations [Formula: see text] with t the intersite hopping constant. For all considered U the system exhibits a transition to the long-range antiferromagnetic order at [Formula: see text]. At the same time no indication of charge ordering is observed. Obtained solutions agree satisfactorily with results of other approaches and obey moments sum rules. In the considered region of the U-T plane, the curve separating metallic solutions passes from [Formula: see text] at the highest temperatures to U  =  2t at [Formula: see text] for half-filling. If only short-range fluctuations are allowed for the remaining part of this region is occupied by insulating solutions. Taking into account long-range fluctuations leads to strengthening of maxima tails, which transform a part of insulating solutions into bad-metal states. For low T, obtained results allow us to trace the gradual transition from the regime of strong correlations with the pronounced four-band structure and well-defined Mott gap for [Formula: see text] to the Slater regime of weak correlations with the spectral intensity having a dip along the boundary of the magnetic Brillouin zone due to an antiferromagnetic ordering for [Formula: see text]. For [Formula: see text] and [Formula: see text] doping leads to the occurrence of a pseudogap near the Fermi level, which is a consequence of the splitting out of a narrow band from a Hubbard subband. Obtained spectra feature waterfalls and Fermi arcs, which are similar to those observed in hole-doped cuprates.

Sr2Ir1 -xRhxO4(x <0.5 ) : An inhomogeneous jeff=1/2 Hubbard system

NASA Astrophysics Data System (ADS)

Chikara, Shalinee; Haskel, Daniel; Sim, Jae-Hoon; Kim, Heung-Sik; Chen, Cheng-Chien; Fabbris, G.; Veiga, L. S. I.; Souza-Neto, N. M.; Terzic, J.; Butrouna, K.; Cao, G.; Han, Myung Joon; van Veenendaal, Michel

2015-08-01

In a combined experimental and theoretical study, we investigate the properties of Sr2Ir1 -xRhxO4 . From the branching ratios of the L -edge isotropic x-ray absorption spectra, we determine that the spin-orbit coupling is remarkably independent of x for both iridium and rhodium sites. DFT+U calculations show that the doping is close to isoelectronic and introduces impurity bands of predominantly rhodium character close to the lower Hubbard band. Overlap of these two bands leads to metallic behavior. Since the low-energy states for x <0.5 have predominantly jeff=1/2 character, we suggest that the electronic properties of this material can be described by an inhomogeneous Hubbard model, where the on-site energies change due to local variations in the spin-orbit interaction strength combined with additional changes in binding energy.

The Nagaoka state and its stability in the one-band Hubbard model

NASA Astrophysics Data System (ADS)

Shen, Shun-Qing; Qiu, Zhao-Ming; Tian, Guang-Shan

1993-07-01

In this article, we discuss the stability of the Nagaoka state with an infinite number of holes in the infinite- U Hubbard model. We shall rigorously show that the Nagaoka state is stable if the total number of holes Nh ≈ Nα∧ with O⩽α<2/ ( d+2) as the number of lattice sites N∧ tends to infinity. Our theorem improves greatly the previous results obtained by Barbieri et al. [Phys. Rev. B 41 (1990) 11697] and by Tian [Phys. Rev. B 44 (1991) 4444].

Amino acid substitutions in the VanS sensor of the VanA-type vancomycin-resistant Enterococcus strains result in high-level vancomycin resistance and low-level teicoplanin resistance.

PubMed

Hashimoto, Y; Tanimoto, K; Ozawa, Y; Murata, T; Ike, Y

2000-04-15

The vancomycin-resistant enterococci GV1, GV2 and GV3, which were isolated from droppings from broiler farms in Japan have been characterized as VanA-type VRE, which express high-level vancomycin resistance (256 or 512 microg ml(-1), MIC) and low-level teicoplanin resistance (1 or 2 microg ml(-1), MIC). The vancomycin resistances were encoded on plasmids. The vancomycin resistance conjugative plasmid pMG2 was isolated from the GV2 strain. The VanA determinant of pMG2 showed the same genetic organization as that of the VanA genes encoded on the representative transposon Tn1546, which comprises vanRSHAXYZ. The nucleotide sequences of all the genes, except the gene related to the vanS gene on Tn1546, were completely identical to the genes encoded on Tn1546. Three amino acid substitutions in the N-terminal region of the deduced VanS were detected in the nucleotide sequence of vanS encoded on pMG2. There were also three amino acid substitutions in the vanS gene of the GV1 and GV3 strains in the same positions as in the vanS gene of pMG2. Vancomycin induced the increased teicoplanin resistance in these strains.

Quench field sensitivity of two-particle correlation in a Hubbard model

PubMed Central

Zhang, X. Z.; Lin, S.; Song, Z.

2016-01-01

Short-range interaction can give rise to particle pairing with a short-range correlation, which may be destroyed in the presence of an external field. We study the transition between correlated and uncorrelated particle states in the framework of one- dimensional Hubbard model driven by a field. We show that the long time-scale transfer rate from an initial correlated state to final uncorrelated particle states is sensitive to the quench field strength and exhibits a periodic behavior. This process involves an irreversible energy transfer from the field to particles, leading to a quantum electrothermal effect. PMID:27250080

Effects of interaction strength, doping, and frustration on the antiferromagnetic phase of the two-dimensional Hubbard model

DOE PAGES

Fratino, L.; Charlebois, M.; Sémon, P.; ...

2017-12-19

Recent quantum-gas microscopy of ultracold atoms and scanning tunneling microscopy of the cuprates reveal new detailed information about doped Mott antiferromagnets, which can be compared with calculations. Using cellular dynamical mean-field theory, we map out the antiferromagnetic (AF) phase of the two-dimensional Hubbard model as a function of interaction strength U, hole doping δ, and temperature T . The Néel phase boundary is nonmonotonic as a function of U and δ. Frustration induced by second-neighbor hopping reduces Néel order more effectively at small U. The doped AF is stabilized at large U by kinetic energy and at small U bymore » potential energy. The transition between the AF insulator and the doped metallic AF is continuous. At large U, we find in-gap states similar to those observed in scanning tunneling microscopy. Finally, we predict that, contrary to the Hubbard bands, these states are only slightly spin polarized.« less

U-Pb geochronology and paleomagnetism of the Neoproterozoic St Simeon dolerite dykes, Quebec: an eastern Laurentian perspective of Ediacaran Rodinia breakup

NASA Astrophysics Data System (ADS)

Pisarevsky, Sergei; Murphy, Brendan; Hamilton, Mike; Söderlund, Ulf; Hodych, Joseph

2013-04-01

The St Simeon (SS) mafic dykes (150 km NE of Quebec City) are now dated at 548 ± 1 Ma (U-Pb; baddeleyite). This age is similar to a published LA-ICPMS zircon age of 550 ± 7 Ma for the Mt. St-Anselme (MS) basalts, which supports previous inferences of (i) a genetic relationship between them, (ii) the pene-contemporaneity of OIB-type mafic magmatism in East Laurentia and (iii) the existence of two late Ediacaran plumes that attended the final breakup of Rodinia and opening of the Iapetus Ocean and Tornquist Sea. Both the SS dykes and the MS basalts were sampled for paleomagnetic study. The paleomagnetic pole for SS is similar to the previously published pole for coeval basalts (Skinner Cove, SC) from Newfoundland. Unlike SC, the St Simeon pole represents rocks which are unambiguously coherent tectonically with the Laurentian Craton. This new pole is also coeval with high quality poles from the Winter Coast (Baltica) and provides paleomagnetic constraints on the history of the final breakup of Rodinia and opening of Eastern Iapetus and Tornquist Sea.

Phase diagram of the Hubbard-Holstein model on a four-leg tube system at quarter filling

NASA Astrophysics Data System (ADS)

Reja, Sahinur; Nishimoto, Satoshi

2018-06-01

We derive an effective electronic Hamiltonian for the square lattice Hubbard-Holstein model (HHM) in the strong electron-electron (e -e ) and electron-phonon (e -p h ) coupling regime and under nonadiabatic conditions (t /ω0≤1 ), t and ω0 being the electron hopping and phonon frequency respectively. Using the density matrix renormalization-group method, we simulate this effective electronic model on a four-leg cylinder system at quarter filling and present a phase diagram in the g -U plane where g and U are the e -p h coupling constant and Hubbard on-site interaction respectively. For larger g , we find that a cluster of spins, i.e., phase separation (PS), gives way to a charge density wave (CDW) phase made of nearest-neighbor singlets which abruptly goes to another CDW phase as we increase U . But for smaller g , we find a metallic phase sandwiched between PS and the singlet CDW phase. This phase is characterized by a vanishing charge gap but a finite spin gap, suggesting a singlet superconducting phase.

Major and trace element, and Sr isotope compositions of clinopyroxene phenocrysts in mafic dykes on Jiaodong Peninsula, southeastern North China Craton: Insights into magma mixing and source metasomatism

NASA Astrophysics Data System (ADS)

Liang, Yayun; Deng, Jun; Liu, Xuefei; Wang, Qingfei; Qin, Cheng; Li, Yan; Yang, Yi; Zhou, Mian; Jiang, Jieyan

2018-03-01

Early Cretaceous mafic dyke swarms are widely developed on Jiaodong Peninsula in the southeastern part of the North China Craton (NCC), but their petrogenesis remains enigmatic. We have examined the in-situ major element, trace element and Sr isotope compositions of the clinopyroxene phenocrysts in these dykes in order to evaluate the extent of magma mixing and source metasomatism. Depending on the type of mineral zoning, the clinopyroxene phenocrysts in our samples can be classified into two groups: Group I (reverse zoning) and Group II (no zoning). Based on core compositions, the Group I phenocrysts with obvious reverse zoning can be divided into two subgroups: Groups IA and IB. The cores of Group IA clinopyroxenes have low values of Mg#, low Al2O3 contents, high Na2O contents, and high 87Sr/86Sr ratios, and they were probably derived from newly accreted lower crust that formed through the underplating of basaltic magma. In contrast, the cores of Group IB clinopyroxenes have lower Mg# values and lower contents of Al2O3, ΣREE (total rare earth elements), and incompatible elements, but they have similar 87Sr/86Sr ratios; these cores crystallised from crust-derived andesitic-dacitic magma. Group IA and IB clinopyroxene phenocryst rims (Group I rims) all have similar compositions with higher values of Mg# and higher Al2O3, Cr and Ni contents than the cores. The rims have high 87Sr/86Sr ratios, are enriched in LREEs (light rare earth elements) and LILEs (large ion lithophile elements), and are depleted in HFSEs (high field strength elements); these characteristics indicate that all the high-Mg rims were derived from a similar magma, possibly a relatively primitive magma derived from lithospheric mantle. We suggest, therefore, that the reversely-zoned clinopyroxene phenocrysts (Group I) in the Jiaodong mafic dykes provide evidence of magma mixing between a magma derived from lithospheric mantle and crust-derived andesitic-dacitic melt alongside with the newly accreted

Orbital selective directional conductor in the two-orbital Hubbard model

DOE PAGES

Mukherjee, Anamitra; Patel, Niravkumar D.; Moreo, Adriana; ...

2016-02-29

Recently, we employed a developed many-body technique that allows for the incorporation of thermal effects, the rich phase diagram of a two-dimensional two-orbital (degenerate d xz and d yz) Hubbard model is presented varying temperature and the repulsion U. The main result is the finding at intermediate U of an antiferromagnetic orbital selective state where an effective dimensional reduction renders one direction insulating and the other metallic. Possible realizations of this state are discussed. Additionally, we also study nematicity above the N eel temperature. After a careful finite-size scaling analysis, the nematicity temperature window appears to survive in the bulkmore » limit, although it is very narrow.« less

Impacts of dyke development in flood prone areas in the Vietnamese Mekong Delta to downstream flood hazard

NASA Astrophysics Data System (ADS)

Khanh Triet Nguyen, Van; Dung Nguyen, Viet; Fujii, Hideto; Kummu, Matti; Merz, Bruno; Apel, Heiko

2016-04-01

The Vietnamese Mekong Delta (VMD) plays an important role in food security and socio-economic development of the country. Being a low-lying coastal region, the VMD is particularly susceptible to both riverine and tidal floods, which provide, on (the) one hand, the basis for the rich agricultural production and the livelihood of the people, but on the other hand pose a considerable hazard depending on the severity of the floods. But despite of potentially hazardous flood, the area remain active as a rice granary due to its nutrient-rich soils and sediment input, and dense waterways, canals and the long standing experience of the population living with floods. In response to both farmers' requests and governmental plans, the construction of flood protection infrastructure in the delta progressed rapidly in the last twenty years, notably at areas prone to deep flooding, i.e. the Plain of Reeds (PoR) and Long Xuyen Quadrangle (LXQ). Triple rice cropping becomes possible in farmlands enclosed by "full-dykes", i.e. dykes strong and high enough to prevent flooding of the flood plains for most of the floods. In these protected flood plains rice can be grown even during the peak flood period (September to November). However, little is known about the possibly (and already alleged) negative impacts of this fully flood protection measure to downstream areas. This study aims at quantifying how the flood regime in the lower part of the VMD (e.g. Can Tho, My Thuan, …) has been changed in the last 2 recent "big flood" events of 2000 and 2011 due to the construction of the full-dyke system in the upper part. First, an evaluation of 35 years of daily water level data was performed in order to detect trends at key gauging stations: Kratie: upper boundary of the Delta, Tan Chau and Chau Doc: areas with full-dyke construction, Can Tho and My Thuan: downstream. Results from the Mann-Kendall (MK) test show a decreasing trend of the annual maximum water level at 3 stations Kratie, Tan

BCS Theory of Time-Reversal-Symmetric Hofstadter-Hubbard Model

NASA Astrophysics Data System (ADS)

Umucalılar, R. O.; Iskin, M.

2017-08-01

The competition between the length scales associated with the periodicity of a lattice potential and the cyclotron radius of a uniform magnetic field is known to have dramatic effects on the single-particle properties of a quantum particle, e.g., the fractal spectrum is known as the Hofstadter butterfly. Having this intricate competition in mind, we consider a two-component Fermi gas on a square optical lattice with opposite synthetic magnetic fields for the components, and study its effects on the many-body BCS-pairing phenomenon. By a careful addressing of the distinct superfluid transitions from the semimetal, quantum spin-Hall insulator, or normal phases, we explore the low-temperature phase diagrams of the model, displaying lobe structures that are reminiscent of the well-known Mott-insulator transitions of the Bose-Hubbard model.

Modelling of The Dyke Emplacement Leading To The Etna July 2001 Eruption Through Continuous Tilt and GPS Data

NASA Astrophysics Data System (ADS)

Bonaccorso, A.; Aloisi, M.; Mattia, A.

During the June 2001 eruption of Mt. Etna the continuous ground deformation mon- itoring have been recorded through tilt (9 stations) and GPS (11 stations) permanent networks. The evolution of the July crisis preceding and leading to the eruption has been monitored through the tilt and GPS continuous measurements, which constrained in time the final intrusion and inferred the position and geometry of the uprising dyke. The tilt signals, which record 48 samples/day, fixed the time action of the intrusion, whose main effects are recorded during 13-15 July in concomitance with the first days of the seismic crisis. In particular, the high precision long-base mercury tiltmeter, in- stalled at Pizzi Deneri observatory in the high north-eastern flank close to the crater area, showed very well the continuous deformation during the dyke emplacement. The deformation pattern, at the entire volcano scale, was well characterised by the daily measurement sessions recorded at the GPS permanent network. The variations recorded at the permanent GPS stations started from July 13 and, in agreement with tilt recordings, were mainly cumulated in the following two days. The GPS measurements showed horizontal displacement vectors much bigger than vertical changes. The defor- mation pattern indicates the response to a tensile mechanisms that appears compatible with an intrusion in the volcano edifice along a ca. N-S direction. In this poster we show the modelling of the marked ground deformation changes recorded in the days before the eruption starting. The first results show that a tensile crack with an opening dislocation of ~3 m. and crossing the entire edifice, south-west to the crater area, can explain the recorded deformation pattern. The location of the modelled tensile source fits the seismogenetic zone characterized by epicenters aligned in a ca. N-S direction with the foci clustered in the last shallow kilometers. The ground deformation pat- tern associated with the final

19 CFR 10.41a - Lift vans, cargo vans, shipping tanks, skids, pallets, and similar instruments of international...

Code of Federal Regulations, 2011 CFR

2011-04-01

... 19 Customs Duties 1 2011-04-01 2011-04-01 false Lift vans, cargo vans, shipping tanks, skids... Traffic § 10.41a Lift vans, cargo vans, shipping tanks, skids, pallets, and similar instruments of international traffic; repair components. (a)(1) Lift vans, cargo vans, shipping tanks, skids, pallets, caul...

19 CFR 10.41a - Lift vans, cargo vans, shipping tanks, skids, pallets, and similar instruments of international...

Code of Federal Regulations, 2010 CFR

2010-04-01

... 19 Customs Duties 1 2010-04-01 2010-04-01 false Lift vans, cargo vans, shipping tanks, skids... Traffic § 10.41a Lift vans, cargo vans, shipping tanks, skids, pallets, and similar instruments of international traffic; repair components. (a)(1) Lift vans, cargo vans, shipping tanks, skids, pallets, caul...

Linking water age and solute dynamics in streamflow at the Hubbard Brook Experimental Forest, NH, USA

Treesearch

Paolo Benettin; Scott W. Bailey; John L. Campbell; Mark B. Green; Andrea Rinaldo; Gene E. Likens; Kevin J. McGuire; Gianluca Botter

2015-01-01

We combine experimental and modeling results from a headwater catchment at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA, to explore the link between stream solute dynamics and water age. A theoretical framework based on water age dynamics, which represents a general basis for characterizing solute transport at the catchment scale, is here applied to...

Elevation dependent sensitivity of northern hardwoods to Ca addition at Hubbard Brook Experimental Forest, NH USA

Treesearch

Rakesh Minocha; Stephanie Long; Palaniswamy Thangavel; Subhash C. Minocha; Christopher Eagar; Charles T. Driscoll

2010-01-01

Acidic deposition has caused a depletion of calcium (Ca) in the northeastern forest soils. Wollastonite (Ca silicate) was added to watershed 1 (WS1) at the Hubbard Brook Experimental Forest (HBEF) in 1999 to evaluate its effects on various functions of the HBEF ecosystem. The effects of Ca addition on foliar soluble (extractable in 5% HClO4) ions...

Variation in chemistry of stream water and bulk deposition across the Hubbard Brook Valley, New Hampshire, USA

Treesearch

Gene E. Likens; Donald C. Buso; James W. Hornbeck

2002-01-01

Chemistry and volume of precipitation and stream water have been measured in south-facing watersheds of the Hubbard Brook Experimental Forest (HBEF), continuously for 37 years. These long-term data have provided important insights into the bio-geochemistry of these watershed ecosystems and the region (e.g. LIKENS & BORMANN 1995).

Calculations of Hubbard U from first-principles

NASA Astrophysics Data System (ADS)

Aryasetiawan, F.; Karlsson, K.; Jepsen, O.; Schönberger, U.

2006-09-01

The Hubbard U of the 3d transition metal series as well as SrVO3 , YTiO3 , Ce, and Gd has been estimated using a recently proposed scheme based on the random-phase approximation. The values obtained are generally in good accord with the values often used in model calculations but for some cases the estimated values are somewhat smaller than those used in the literature. We have also calculated the frequency-dependent U for some of the materials. The strong frequency dependence of U in some of the cases considered in this paper suggests that the static value of U may not be the most appropriate one to use in model calculations. We have also made comparison with the constrained local density approximation (LDA) method and found some discrepancies in a number of cases. We emphasize that our scheme and the constrained local density approximation LDA method theoretically ought to give similar results and the discrepancies may be attributed to technical difficulties in performing calculations based on currently implemented constrained LDA schemes.

Extremely high sulfate reduction, sediment oxygen demand and benthic nutrient flux associated with a large-scale artificial dyke and its implication to benthic-pelagic coupling in the Yeongsan River estuary, Yellow Sea.

PubMed

Kim, Sung-Han; Lee, Jae Seong; Hyun, Jung-Ho

2017-07-15

We investigated environmental impact of large-scale dyke on the sediment geochemistry, sulfate reduction rates (SRRs), sediment oxygen demand (SOD) and potential contribution of benthic nutrient flux (BNF) to primary production in the Yeongsan River estuary, Yellow Sea. The sediment near the dyke (YE1) with high organic carbon (C org ) content (>4%, dry wt.) was characterized by extremely high SOD (327mmolm -2 d -1 ) and SRRs (91-140mmolm -2 d -1 ). The sulfate reduction accounted for 73% of C org oxidation, and was responsible for strikingly high concentrations of NH 4 + (7.7mM), PO 4 3- (67μM) and HS - (487μM) in pore water. The BNF at YE1 accounted for approximately 200% of N and P required for primary production in the water column. The results present one of the most extreme cases that the construction of an artificial dyke may have profound impacts on the biogeochemical and ecological processes in coastal ecosystems. Copyright © 2017 Elsevier Ltd. All rights reserved.

Defending commercial surrogate motherhood against Van Niekerk and Van Zyl.

PubMed Central

McLachlan, H V

1997-01-01

The arguments of Van Niekerk and Van Zyl that, on the grounds that it involves an inappropriate commodification and alienation of women's labour, commercial surrogate motherhood (CSM) is morally suspect are discussed and considered to be defective. In addition, doubt is cast on the notion that CSM should be illegal. PMID:9451602

What if the Hubbard Brook weirs had been built somewhere else? Spatial uncertainty in the application of catchment budgets

NASA Astrophysics Data System (ADS)

Bailey, S. W.

2016-12-01

Nine catchments are gaged at Hubbard Brook Experimental Forest, Woodstock, NH, USA, with weirs installed on adjacent first-order streams. These catchments have been used as unit ecosystems for analysis of chemical budgets, including evaluation of long term trends and response to disturbance. This study examines uncertainty in the representativeness of these budgets to other nearby catchments, or as representatives of the broader northern hardwood ecosystem, depending on choice of location of the stream gaging station. Within forested northern hardwood catchments across the Hubbard Brook region, there is relatively little spatial variation in amount or chemistry of precipitation inputs or in amount of streamwater outputs. For example, runoff per unit catchment area varies by less than 10% at gaging stations on first to sixth order streams. In contrast, concentrations of major solutes vary by an order of magnitude or more across stream sampling sites, with a similar range in concentrations seen within individual first order catchments as seen across the third order Hubbard Brook valley or across the White Mountain region. These spatial variations in stream chemistry are temporally persistent across a range of flow conditions. Thus first order catchment budgets vary greatly depending on very local variations in stream chemistry driven by choice of the site to develop a stream gage. For example, carbon output in dissolved organic matter varies by a factor of five depending on where the catchment output is defined at Watershed 3. I hypothesize that catchment outputs from first order streams are driven by spatially variable chemistry of shallow groundwater, reflecting local variations in the distribution of soils and vegetation. In contrast, spatial variability in stream chemistry decreases with stream order, hypothesized to reflect deeper groundwater inputs on larger streams, which are more regionally uniform. Thus, choice of a gaging site and definition of an ecosystem

Quantum behaviour of pumped and damped triangular Bose-Hubbard systems

NASA Astrophysics Data System (ADS)

Chianca, C. V.; Olsen, M. K.

2017-12-01

We propose and analyse analogs of optical cavities for atoms using three-well Bose-Hubbard models with pumping and losses. We consider triangular configurations. With one well pumped and one damped, we find that both the mean-field dynamics and the quantum statistics show a quantitative dependence on the choice of damped well. The systems we analyse remain far from equilibrium, preserving good coherence between the wells in the steady-state. We find quadrature squeezing and mode entanglement for some parameter regimes and demonstrate that the trimer with pumping and damping at the same well is the stronger option for producing non-classical states. Due to recent experimental advances, it should be possible to demonstrate the effects we investigate and predict.

On precisely modelling surface deformation due to interacting magma chambers and dykes

NASA Astrophysics Data System (ADS)

Pascal, Karen; Neuberg, Jurgen; Rivalta, Eleonora

2014-01-01

Combined data sets of InSAR and GPS allow us to observe surface deformation in volcanic settings. However, at the vast majority of volcanoes, a detailed 3-D structure that could guide the modelling of deformation sources is not available, due to the lack of tomography studies, for example. Therefore, volcano ground deformation due to magma movement in the subsurface is commonly modelled using simple point (Mogi) or dislocation (Okada) sources, embedded in a homogeneous, isotropic and elastic half-space. When data sets are too complex to be explained by a single deformation source, the magmatic system is often represented by a combination of these sources and their displacements fields are simply summed. By doing so, the assumption of homogeneity in the half-space is violated and the resulting interaction between sources is neglected. We have quantified the errors of such a simplification and investigated the limits in which the combination of analytical sources is justified. We have calculated the vertical and horizontal displacements for analytical models with adjacent deformation sources and have tested them against the solutions of corresponding 3-D finite element models, which account for the interaction between sources. We have tested various double-source configurations with either two spherical sources representing magma chambers, or a magma chamber and an adjacent dyke, modelled by a rectangular tensile dislocation or pressurized crack. For a tensile Okada source (representing an opening dyke) aligned or superposed to a Mogi source (magma chamber), we find the discrepancies with the numerical models to be insignificant (<5 per cent) independently of the source separation. However, if a Mogi source is placed side by side to an Okada source (in the strike-perpendicular direction), we find the discrepancies to become significant for a source separation less than four times the radius of the magma chamber. For horizontally or vertically aligned pressurized

Berezinskii-Kosterlitz-Thouless transition in the time-reversal-symmetric Hofstadter-Hubbard model

NASA Astrophysics Data System (ADS)

Iskin, M.

2018-01-01

Assuming that two-component Fermi gases with opposite artificial magnetic fields on a square optical lattice are well described by the so-called time-reversal-symmetric Hofstadter-Hubbard model, we explore the thermal superfluid properties along with the critical Berezinskii-Kosterlitz-Thouless (BKT) transition temperature in this model over a wide range of its parameters. In particular, since our self-consistent BCS-BKT approach takes the multiband butterfly spectrum explicitly into account, it unveils how dramatically the interband contribution to the phase stiffness dominates the intraband one with an increasing interaction strength for any given magnetic flux.

Numerically exploring the 1D-2D dimensional crossover on spin dynamics in the doped Hubbard model

DOE PAGES

Kung, Y. F.; Bazin, C.; Wohlfeld, K.; ...

2017-11-02

Using determinant quantum Monte Carlo (DQMC) simulations, we systematically study the doping dependence of the crossover from one to two dimensions and its impact on the magnetic properties of the Hubbard model. A square lattice of chains is used, in which the dimensionality can be tuned by varying the interchain coupling t ⊥. The dynamical spin structure factor and static quantities, such as the static spin susceptibility and nearest-neighbor spin correlation function, are characterized in the one- and two-dimensional limits as a benchmark. When the dimensionality is tuned between these limits, the magnetic properties, while evolving smoothly from one tomore » two dimensions, drastically change regardless of the doping level. This suggests that the spin excitations in the two-dimensional Hubbard model, even in the heavily doped case, cannot be explained using the spinon picture known from one dimension. In conclusion, the DQMC calculations are complemented by cluster perturbation theory studies to form a more complete picture of how the crossover occurs as a function of doping and how doped holes impact magnetic order.« less

Space Van system update

NASA Astrophysics Data System (ADS)

Cormier, Len

1992-07-01

The Space Van is a proposed commercial launch vehicle that is designed to carry 1150 kg to a space-station orbit for a price of $1,900,000 per flight in 1992 dollars. This price includes return on preoperational investment. Recurring costs are expected to be about $840,000 per flight. The Space Van is a fully reusable, assisted-single-stage-to orbit system. The most innovative new feature of the Space Van system is the assist-stage concept. The assist stage uses only airbreathing engines for vertical takeoff and vertical landing in the horizontal attitude and for launching the rocket-powered orbiter stage at mach 0.8 and an altitude of about 12 km. The primary version of the orbiter is designed for cargo-only without a crew. However, a passenger version of the Space Van should be able to carry a crew of two plus six passengers to a space-station orbit. Since the Space Van is nearly single-stage, performance to polar orbit drops off significantly. The cargo version should be capable of carrying 350 kg to a 400-km polar orbit. In the passenger version, the Space Van should be able to carry two crew members - or one crew member plus a passenger.

Quantum Phase Transition and Local Entanglement in Extended Hubbard Model on Anisotropic Triangular Lattices

NASA Astrophysics Data System (ADS)

Gao, Ji-Ming; Tang, Rong-An; Zhang, Zheng-Mei; Xue, Ju-Kui

2016-11-01

Using a mean-field theory based upon Hartree—Fock approximation, we theoretically investigate the competition between the metallic conductivity, spin order and charge order phases in a two-dimensional half-filled extended Hubbard model on anisotropic triangular lattice. Bond order, double occupancy, spin and charge structure factor are calculated, and the phase diagram of the extended Hubbard model is presented. It is found that the interplay of strong interaction and geometric frustration leads to exotic phases, the charge fluctuation is enhanced and three kinds of charge orders appear with the introduction of the nearest-neighbor interaction. Moreover, for different frustrations, it is also found that the antiferromagnetic insulating phase and nonmagnetic insulating phase are rapidly suppressed, and eventually disappeared as the ratio between the nearest-neighbor interaction and on-site interaction increases. This indicates that spin order is also sensitive to the nearest-neighbor interaction. Finally, the single-site entanglement is calculated and it is found that a clear discontinuous of the single-site entanglement appears at the critical points of the phase transition. Supported by National Natural Science Foundation of China under Grant Nos.11274255, 11475027 and 11305132, Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No. 20136203110001, and Technology of Northwest Normal University, China under Grants No. NWNU-LKQN-11-26

Quantum Monte Carlo study of spin correlations in the one-dimensional Hubbard model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sandvik, A.W.; Scalapino, D.J.; Singh, C.

1993-07-15

The one-dimensional Hubbard model is studied at and close to half-filling using a generalization of Handscomb's quantum Monte Carlo method. Results for spin-correlation functions and susceptibilities are presented for systems of up to 128 sites. The spin-correlation function at low temperature is well described by a recently introduced formula relating the correlation function of a finite periodic system to the corresponding [ital T]=0 correlation function of the infinite system. For the [ital T][r arrow]0 divergence of the [ital q]=2[ital k][sub [ital F

Mass-imbalanced Hubbard model in optical lattice with site-dependent interactions

NASA Astrophysics Data System (ADS)

Le, Duc-Anh; Tran, Thi-Thu-Trang; Hoang, Anh-Tuan; Nguyen, Toan-Thang; Tran, Minh-Tien

2018-03-01

We study the half-filled mass-imbalanced Hubbard model with spatially alternating interactions on an optical bipartite lattice by means of the dynamical mean-field theory. The Mott transition is investigated via the spin-dependent density of states and double occupancies. The phase diagrams for the homogeneous phases at zero temperature are constructed numerically. The boundary between metallic and insulating phases at zero temperature is analytically derived within the dynamical mean field theory using the equation of motion approach as the impurity solver. We found that the metallic region is reduced with increasing interaction anisotropy or mass imbalance. Our results are closely relevant to current researches in ultracold fermion experiments and can be verified through experimental observations.

Hierarchical relaxation dynamics in a tilted two-band Bose-Hubbard model

NASA Astrophysics Data System (ADS)

Cosme, Jayson G.

2018-04-01

We numerically examine slow and hierarchical relaxation dynamics of interacting bosons described by a tilted two-band Bose-Hubbard model. The system is found to exhibit signatures of quantum chaos within the spectrum and the validity of the eigenstate thermalization hypothesis for relevant physical observables is demonstrated for certain parameter regimes. Using the truncated Wigner representation in the semiclassical limit of the system, dynamics of relevant observables reveal hierarchical relaxation and the appearance of prethermalized states is studied from the perspective of statistics of the underlying mean-field trajectories. The observed prethermalization scenario can be attributed to different stages of glassy dynamics in the mode-time configuration space due to dynamical phase transition between ergodic and nonergodic trajectories.

Revealing hidden antiferromagnetic correlations in doped Hubbard chains via string correlators

NASA Astrophysics Data System (ADS)

Hilker, Timon A.; Salomon, Guillaume; Grusdt, Fabian; Omran, Ahmed; Boll, Martin; Demler, Eugene; Bloch, Immanuel; Gross, Christian

2017-08-01

Topological phases, like the Haldane phase in spin-1 chains, defy characterization through local order parameters. Instead, nonlocal string order parameters can be employed to reveal their hidden order. Similar diluted magnetic correlations appear in doped one-dimensional lattice systems owing to the phenomenon of spin-charge separation. Here we report on the direct observation of such hidden magnetic correlations via quantum gas microscopy of hole-doped ultracold Fermi-Hubbard chains. The measurement of nonlocal spin-density correlation functions reveals a hidden finite-range antiferromagnetic order, a direct consequence of spin-charge separation. Our technique, which measures nonlocal order directly, can be readily extended to higher dimensions to study the complex interplay between magnetic order and density fluctuations.

Quantum steering and entanglement in three-mode triangle Bose-Hubbard system

NASA Astrophysics Data System (ADS)

Kalaga, J. K.; Leoński, W.; Szczȩśniak, R.

2017-11-01

We consider the possibility of generation steerable states in Bose-Hubbard system composed of three interacting wells in the form of a triangle. We show that although our system still fulfills the monogamy relations, the presence of additional coupling which transforms a chain of wells onto triangle gives a variety of new possibilities for the generation of steerable quantum states. Deriving analytical formulas for the parameters describing steering and bipartite entanglement, we show that interplay between two couplings influences quantum correlations of various types. We compare the time evolution of steering parameters to those describing bipartite entanglement and find the relations between the appearance of maximal entanglement and disappearance of steering effect.

Carbonatitic dykes during Pangaea transtension (Pelagonian Zone, Greece)

NASA Astrophysics Data System (ADS)

Schenker, Filippo Luca; Burg, Jean-Pierre; Kostopoulos, Dimitrios; Baumgartner, Lukas P.; Bouvier, Anne-Sophie

2018-03-01

Carbonatitic dykes surrounded by K-Na-fenites were discovered in the Pelagonian Zone in Greece. Their carbonate portions have an isotopic mantle signature of δ13C and δ18O ranging from -5.18 to -5.56 (‰ vs. VPDB) and from 10.68 to 11.59 (‰ vs. VSMOW) respectively, whereas their mafic silicate portions have high Nb, Ta and ɛNd values, typical of alkaline basalts. Textural relationships hint at a cogenetic intrusion of silicate and carbonate liquids that according to antithetic REE profiles segregated at shallow depths (<0.6 GPa) from a parental melt sourced deeper in the mantle. Fenites bear similar REE abundances to mafic rocks but with high Rb-Ba and low Nb-Ta values. SHRIMP II U-Pb analyses of magmatic zircon cores (δ18O = 7.21-7.51) from a carbonate-bearing syenitic amphibolite yielded a Permian intrusion age at 278 ± 2 Ma, considerably older than a Cretaceous (118 ± 4 Ma) greenschist overprint obtained from metamorphic zircon rims (δ18O = 6.78-7.02). From 300 to 175 Ma the ɛNd of the Pelagonian magmatism rose irregularly to more primitive values attesting to a higher increment of asthenosphere-derived melts. In this context, the carbonatite formed within a transtensional regime of an intra-Pangaea dextral transform fault that signalled the forthcoming penetrating breakoff of the supercontinent, manifested in the Permo-Triassic.

Quantum behaviour of open pumped and damped Bose-Hubbard trimers

NASA Astrophysics Data System (ADS)

Chianca, C. V.; Olsen, M. K.

2018-01-01

We propose and analyse analogs of optical cavities for atoms using three-well inline Bose-Hubbard models with pumping and losses. With one well pumped and one damped, we find that both the mean-field dynamics and the quantum statistics show a qualitative dependence on the choice of damped well. The systems we analyse remain far from equilibrium, although most do enter a steady-state regime. We find quadrature squeezing, bipartite and tripartite inseparability and entanglement, and states exhibiting the EPR paradox, depending on the parameter regimes. We also discover situations where the mean-field solutions of our models are noticeably different from the quantum solutions for the mean fields. Due to recent experimental advances, it should be possible to demonstrate the effects we predict and investigate in this article.

The One-Hole, One-Dimensional Hubbard Model at U = ∞

NASA Astrophysics Data System (ADS)

Hodge, William; Holzwarth, Natalie; Kerr, William

2008-03-01

The Hubbard Hamiltonian is the simplest model that describes interacting electrons on a lattice. In this work, we use the properties of stochastic matrices to examine the ground state with an even number of lattice sites and one electron less than half-filling. We show that there exists a highly symmetric state with energy -2 (in units where t = 1) at all U. At U = ∞ this state becomes the lowest energy state, consistent with the established lower energy bound. ootnotetextS. A. Trugman, Phys. Rev. B 42, 6612 (1990) Using this result, several properties of the strongly coupled ground state are derived, including the chemical potential and momentum distribution. This method may be applicable to other models as well. Disagreements between our results and previous work are examined.

Effect of the next-nearest-neighbor hopping on the charge collective modes in the paramagnetic phase of the Hubbard model

NASA Astrophysics Data System (ADS)

Dao, Vu Hung; Frésard, Raymond

2017-10-01

The charge dynamical response function of the t-t'-U Hubbard model is investigated on the square lattice in the thermodynamical limit. The correlation function is calculated from Gaussian fluctuations around the paramagnetic saddle-point within the Kotliar and Ruckenstein slave-boson representation. The next-nearest-neighbor hopping only slightly affects the renormalization of the quasiparticle mass. In contrast a negative t'/t notably decreases (increases) their velocity, and hence the zero-sound velocity, at positive (negative) doping. For low (high) density n ≲ 0.5 (n ≳ 1.5) we find that it enhances (reduces) the damping of the zero-sound mode. Furthermore it softens (hardens) the upper-Hubbard-band collective mode at positive (negative) doping. It is also shown that our results differ markedly from the random-phase approximation in the strong-coupling limit, even at high doping, while they compare favorably with existing quantum Monte Carlo numerical simulations.

Mesoscopic Dynamical Differences from Quantum State Preparation in a Bose-Hubbard Trimer

NASA Astrophysics Data System (ADS)

Olsen, M. K.; Neely, T. W.; Bradley, A. S.

2018-06-01

Conventional wisdom is that quantum effects will tend to disappear as the number of quanta in a system increases, and the evolution of a system will become closer to that described by mean-field classical equations. In this Letter we combine newly developed theoretical and experimental techniques to propose and analyze an experiment using a Bose-Hubbard trimer where the opposite is the case. We find that differences in the preparation of a centrally evacuated trimer can lead to readily observable differences in the subsequent dynamics which increase with system size. Importantly, these differences can be detected by the simple measurements of atomic number.

Density matrix renormalization group study of a three-orbital Hubbard model with spin-orbit coupling in one dimension

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaushal, Nitin; Herbrych, Jacek W.; Nocera, Alberto

Using the density matrix renormalization group technique we study the effect of spin-orbit coupling on a three-orbital Hubbard model in the (t 2g) 4 sector and in one dimension. Fixing the Hund coupling to a robust value compatible with some multiorbital materials, we present the phase diagram varying the Hubbard U and spin-orbit coupling λ, at zero temperature. Our results are shown to be qualitatively similar to those recently reported using the dynamical mean-field theory in higher dimensions, providing a robust basis to approximate many-body techniques. Among many results, we observe an interesting transition from an orbital-selective Mott phase tomore » an excitonic insulator with increasing λ at intermediate U. In the strong U coupling limit, we find a nonmagnetic insulator with an effective angular momentum <(J eff) 2>≠0 near the excitonic phase, smoothly connected to the <(J eff) 2>=0 regime. In conclusion, we also provide a list of quasi-one-dimensional materials where the physics discussed in this paper could be realized.« less

Density matrix renormalization group study of a three-orbital Hubbard model with spin-orbit coupling in one dimension

NASA Astrophysics Data System (ADS)

Kaushal, Nitin; Herbrych, Jacek; Nocera, Alberto; Alvarez, Gonzalo; Moreo, Adriana; Reboredo, F. A.; Dagotto, Elbio

2017-10-01

Using the density matrix renormalization group technique we study the effect of spin-orbit coupling on a three-orbital Hubbard model in the (t2g) 4 sector and in one dimension. Fixing the Hund coupling to a robust value compatible with some multiorbital materials, we present the phase diagram varying the Hubbard U and spin-orbit coupling λ , at zero temperature. Our results are shown to be qualitatively similar to those recently reported using the dynamical mean-field theory in higher dimensions, providing a robust basis to approximate many-body techniques. Among many results, we observe an interesting transition from an orbital-selective Mott phase to an excitonic insulator with increasing λ at intermediate U . In the strong U coupling limit, we find a nonmagnetic insulator with an effective angular momentum 〈(Jeff)2〉≠0 near the excitonic phase, smoothly connected to the 〈(Jeff)2〉=0 regime. We also provide a list of quasi-one-dimensional materials where the physics discussed in this paper could be realized.

Density matrix renormalization group study of a three-orbital Hubbard model with spin-orbit coupling in one dimension

DOE PAGES

Kaushal, Nitin; Herbrych, Jacek W.; Nocera, Alberto; ...

2017-10-09

Using the density matrix renormalization group technique we study the effect of spin-orbit coupling on a three-orbital Hubbard model in the (t 2g) 4 sector and in one dimension. Fixing the Hund coupling to a robust value compatible with some multiorbital materials, we present the phase diagram varying the Hubbard U and spin-orbit coupling λ, at zero temperature. Our results are shown to be qualitatively similar to those recently reported using the dynamical mean-field theory in higher dimensions, providing a robust basis to approximate many-body techniques. Among many results, we observe an interesting transition from an orbital-selective Mott phase tomore » an excitonic insulator with increasing λ at intermediate U. In the strong U coupling limit, we find a nonmagnetic insulator with an effective angular momentum <(J eff) 2>≠0 near the excitonic phase, smoothly connected to the <(J eff) 2>=0 regime. In conclusion, we also provide a list of quasi-one-dimensional materials where the physics discussed in this paper could be realized.« less

Hubbard Glacier, Alaska: growing and advancing in spite of global climate change and the 1986 and 2002 Russell Lake outburst floods

USGS Publications Warehouse

Trabant, Dennis C.; March, Rod S.; Thomas, Donald S.

2003-01-01

Hubbard Glacier, the largest calving glacier on the North American Continent (25 percent larger than Rhode Island), advanced across the entrance to 35-mile-long Russell Fiord during June 2002, temporarily turning it into a lake. Hubbard Glacier has been advancing for more than 100 years and has twice closed the entrance to Russell Fiord during the last 16 years by squeezing and pushing submarine glacial sediments across the mouth of the fiord. Water flowing into the cutoff fiord from mountain streams and glacier melt causes the level of Russell Lake to rise. However, both the 1986 and 2002 dams failed before the lake altitude rose enough for water to spill over a low pass at the far end of the fiord and enter the Situk River drainage, a world-class sport and commercial fishery near Yakutat, Alaska.

Tests with DDT foliar sprays to control the California flatheaded borer

Treesearch

Robert L. Lyon

1959-01-01

The California flatheaded borer (Melanophila californica Van Dyke) kills an estimated 30 million board-feet of pine timber in California each year. The insect is especially troublesome on ponderosa and Jeffrey pines growing on dry sites, and it has caused serious losses in Jeffrey pine stands on valuable , watershed and recreational lands of...

"The City": The Rhetoric of Rhythm.

ERIC Educational Resources Information Center

Medhurst, Martin J.; Benson, Thomas W.

1981-01-01

Case study of Ralph Steiner and Willard Van Dyke's classic documentary, "The City," a work of cinematic art and a record of the problems confronting urban planners. Discusses how the film builds a rhythmic pattern through dramatic structure, image content and composition, editing, music, and narration to enhance its rhetorical appeal. (JMF)

Mentale Inzetbaarheid van Teams: Ontwikkeling van een Moden van Teamfunctioneren als Module voor SCOPE (Mental Readiness of Teams - Development of a Team Model as Module for SCOPE)

DTIC Science & Technology

2007-04-01

inzetbaarheid van teams: ontwikkeling van een model van teamfunctioneren als module voor SCOPE Datumn april 2007 Auteur (s) R. de B~ruin C’. Vervvijs A.J...Datum april 2007 Programmaleider Projectleider Auteur (s) dr. W.A. Lotens, TNO Defensie en A.]. van Vijet, TNO Defensie en R. de Bruin Veiligheid...Deelnemers verwachten wel, in lijn met de theorie , dat een lage cohesie samenhangt met een lage effectiviteit. Een hoge cohesie, daarentegen, zou

Mobile Telemetry Van Remote Control Upgrade

DTIC Science & Technology

2012-05-17

Advantages of Remote Control System Upgrade • Summary Overview • Remote control of Telemetry Mobile Ground Support ( TMGS ) Van proposed to allow...NWC) personnel provided valuable data for full-function remote control of telemetry tracking vans Background • TMGS Vans support Flight Test...control capability from main TM site at Building 5790 currently allows support via TMGS Van at nearby C- 15 Site, Plant 42 in Palmdale, and as far

Members of the Genera Paenibacillus and Rhodococcus Harbor Genes Homologous to Enterococcal Glycopeptide Resistance Genes vanA and vanB

PubMed Central

Guardabassi, L.; Christensen, H.; Hasman, H.; Dalsgaard, A.

2004-01-01

Genes homologous to enterococcal glycopeptide resistance genes vanA and vanB were found in glycopeptide-resistant Paenibacillus and Rhodococcus strains from soil. The putative d-Ala:d-Lac ligase genes in Paenibacillus thiaminolyticus PT-2B1 and Paenibacillus apiarius PA-B2B were closely related to vanA (92 and 87%) and flanked by genes homologous to vanH and vanX in vanA operons. PMID:15561881

Members of the genera Paenibacillus and Rhodococcus harbor genes homologous to enterococcal glycopeptide resistance genes vanA and vanB.

PubMed

Guardabassi, L; Christensen, H; Hasman, H; Dalsgaard, A

2004-12-01

Genes homologous to enterococcal glycopeptide resistance genes vanA and vanB were found in glycopeptide-resistant Paenibacillus and Rhodococcus strains from soil. The putative D-Ala:D-Lac ligase genes in Paenibacillus thiaminolyticus PT-2B1 and Paenibacillus apiarius PA-B2B were closely related to vanA (92 and 87%) and flanked by genes homologous to vanH and vanX in vanA operons.

Past and projected future changes in snowpack and soil frost at the Hubbard Brook Experimental Forest, New Hampshire, USA

USDA-ARS?s Scientific Manuscript database

Long-term data from the Hubbard Brook Experimental Forest in New Hampshire show that air temperature has increased by about 1 °C over the last half century. The warmer climate has caused significant declines in snow depth, snow water equivalent, and snow cover duration. Paradoxically, it has been su...

Quantum Phase Transitions in the Bose Hubbard Model and in a Bose-Fermi Mixture

NASA Astrophysics Data System (ADS)

Duchon, Eric Nicholas

Ultracold atomic gases may be the ultimate quantum simulator. These isolated systems have the lowest temperatures in the observable universe, and their properties and interactions can be precisely and accurately tuned across a full spectrum of behaviors, from few-body physics to highly-correlated many-body effects. The ability to impose potentials on and tune interactions within ultracold gases to mimic complex systems mean they could become a theorist's playground. One of their great strengths, however, is also one of the largest obstacles to this dream: isolation. This thesis touches on both of these themes. First, methods to characterize phases and quantum critical points, and to construct finite temperature phase diagrams using experimentally accessible observables in the Bose Hubbard model are discussed. Then, the transition from a weakly to a strongly interacting Bose-Fermi mixture in the continuum is analyzed using zero temperature numerical techniques. Real materials can be emulated by ultracold atomic gases loaded into optical lattice potentials. We discuss the characteristics of a single boson species trapped in an optical lattice (described by the Bose Hubbard model) and the hallmarks of the quantum critical region that separates the superfluid and the Mott insulator ground states. We propose a method to map the quantum critical region using the single, experimentally accessible, local quantity R, the ratio of compressibility to local number fluctuations. The procedure to map a phase diagram with R is easily generalized to inhomogeneous systems and generic many-body Hamiltonians. We illustrate it here using quantum Monte Carlo simulations of the 2D Bose Hubbard model. Secondly, we investigate the transition from a degenerate Fermi gas weakly coupled to a Bose Einstein condensate to the strong coupling limit of composite boson-fermion molecules. We propose a variational wave function to investigate the ground state properties of such a Bose-Fermi mixture

19 CFR 10.41a - Lift vans, cargo vans, shipping tanks, skids, pallets, and similar instruments of international...

Code of Federal Regulations, 2014 CFR

2014-04-01

... for inspection by Customs officials upon reasonable notice. (3) If the container does not exit the U.S... 19 Customs Duties 1 2014-04-01 2014-04-01 false Lift vans, cargo vans, shipping tanks, skids... Traffic § 10.41a Lift vans, cargo vans, shipping tanks, skids, pallets, and similar instruments of...

19 CFR 10.41a - Lift vans, cargo vans, shipping tanks, skids, pallets, and similar instruments of international...

Code of Federal Regulations, 2012 CFR

2012-04-01

... for inspection by Customs officials upon reasonable notice. (3) If the container does not exit the U.S... 19 Customs Duties 1 2012-04-01 2012-04-01 false Lift vans, cargo vans, shipping tanks, skids... Traffic § 10.41a Lift vans, cargo vans, shipping tanks, skids, pallets, and similar instruments of...

19 CFR 10.41a - Lift vans, cargo vans, shipping tanks, skids, pallets, and similar instruments of international...

Code of Federal Regulations, 2013 CFR

2013-04-01

... for inspection by Customs officials upon reasonable notice. (3) If the container does not exit the U.S... 19 Customs Duties 1 2013-04-01 2013-04-01 false Lift vans, cargo vans, shipping tanks, skids... Traffic § 10.41a Lift vans, cargo vans, shipping tanks, skids, pallets, and similar instruments of...

Phase Separation of Superconducting Phases in the Penson-Kolb-Hubbard Model

NASA Astrophysics Data System (ADS)

Jerzy Kapcia, Konrad; Czart, Wojciech Robert; Ptok, Andrzej

2016-04-01

In this paper, we determine the phase diagrams (for T = 0 as well as T > 0) of the Penson-Kolb-Hubbard model for two dimensional square lattice within Hartree-Fock mean-field theory focusing on an investigation of superconducting phases and on a possibility of the occurrence of the phase separation. We obtain that the phase separation, which is a state of coexistence of two different superconducting phases (with s- and η-wave symmetries), occurs in definite ranges of the electron concentration. In addition, increasing temperature can change the symmetry of the superconducting order parameter (from η-wave into s-wave). The system considered exhibits also an interesting multicritical behaviour including bicritical points. The relevance of the results to experiments for real materials is also discussed.

Ordered phases in the Holstein-Hubbard model: Interplay of strong Coulomb interaction and electron-phonon coupling

NASA Astrophysics Data System (ADS)

Murakami, Yuta; Werner, Philipp; Tsuji, Naoto; Aoki, Hideo

2013-09-01

We study the Holstein-Hubbard model at half filling to explore ordered phases including superconductivity (SC), antiferromagnetism (AF), and charge order (CO) in situations where the electron-electron and electron-phonon interactions are strong (comparable to the electronic bandwidth). The model is solved in the dynamical mean-field approximation with a continuous-time quantum Monte Carlo impurity solver. We determine the superconducting transition temperature Tc and the SC order parameter and show that the phonon-induced retardation or the strong Coulomb interaction leads to a significant reduction and shift of the Tc dome against the effective electron-electron interaction Ueff given by the Hubbard U reduced by the phonon-mediated attraction in the static limit. This behavior is analyzed by comparison to an effective static model in the polaron representation with a renormalized bandwidth. In addition, we discuss the superconducting gap Δ and 2Δ/Tc to reveal the effect of the retardation and the Coulomb interaction. We also determine the finite-temperature phase diagram including AF and CO. In the moderate-coupling regime, there is a hysteretic region of AF and CO around Ueff=0, while the two phases are separated by a paramagnetic metal in the weak-coupling regime and a paramagnetic insulator in the strong-coupling regime.

Benchmarking Density Functional Theory Based Methods To Model NiOOH Material Properties: Hubbard and van der Waals Corrections vs Hybrid Functionals.

PubMed

Zaffran, Jeremie; Caspary Toroker, Maytal

2016-08-09

NiOOH has recently been used to catalyze water oxidation by way of electrochemical water splitting. Few experimental data are available to rationalize the successful catalytic capability of NiOOH. Thus, theory has a distinctive role for studying its properties. However, the unique layered structure of NiOOH is associated with the presence of essential dispersion forces within the lattice. Hence, the choice of an appropriate exchange-correlation functional within Density Functional Theory (DFT) is not straightforward. In this work, we will show that standard DFT is sufficient to evaluate the geometry, but DFT+U and hybrid functionals are required to calculate the oxidation states. Notably, the benefit of DFT with van der Waals correction is marginal. Furthermore, only hybrid functionals succeed in opening a bandgap, and such methods are necessary to study NiOOH electronic structure. In this work, we expect to give guidelines to theoreticians dealing with this material and to present a rational approach in the choice of the DFT method of calculation.

Phase stability in the two-dimensional anisotropic boson Hubbard Hamiltonian

DOE PAGES

Ying, T.; Batrouni, G. G.; Rousseau, V. G.; ...

2013-05-15

The two dimensional square lattice hard-core boson Hubbard model with near neighbor interactions has a ‘checkerboard’ charge density wave insulating phase at half-filling and sufficiently large intersite repulsion. When doped, rather than forming a supersolid phase in which long range charge density wave correlations coexist with a condensation of superfluid defects, the system instead phase separates. However, it is known that there are other lattice geometries and interaction patterns for which such coexistence takes place. In this paper we explore the possibility that anisotropic hopping or anisotropic near neighbor repulsion might similarly stabilize the square lattice supersolid. Lastly, by consideringmore » the charge density wave structure factor and superfluid density for different ratios of interaction strength and hybridization in the ˆx and ˆy directions, we conclude that phase separation still occurs.« less

Critical behavior of the extended Hubbard model with bond dimerization

NASA Astrophysics Data System (ADS)

Ejima, Satoshi; Lange, Florian; Essler, Fabian H. L.; Fehske, Holger

2018-05-01

Exploiting the matrix-product-state based density-matrix renormalization group (DMRG) technique we study the one-dimensional extended (U-V) Hubbard model with explicit bond dimerization in the half-filled band sector. In particular we investigate the nature of the quantum phase transition, taking place with growing ratio V / U between the symmetry-protected-topological and charge-density-wave insulating states. The (weak-coupling) critical line of continuous Ising transitions with central charge c = 1 / 2 terminates at a tricritical point belonging to the universality class of the dilute Ising model with c = 7 / 10 . We demonstrate that our DMRG data perfectly match with (tricritical) Ising exponents, e.g., for the order parameter β = 1 / 8 (1/24) and correlation length ν = 1 (5/9). Beyond the tricritical Ising point, in the strong-coupling regime, the quantum phase transition becomes first order.

Mineralogy and geochemistry of picro-dolerite dykes from the central Deccan Traps flood basaltic province, India, and their geodynamic significance

NASA Astrophysics Data System (ADS)

Dongre, Ashish; Viljoen, K. S.; Rathod, A.

2018-04-01

Constituent mineral compositions and whole rock major element geochemistry of picro-dolerite dykes from the central part of the Deccan flood basalt province are presented and discussed. The dykes are characterized by an MgO content of about 13 wt%, coupled with 13-16 modal percents of olivine. A high whole rock molar Mg# value of 71 and the presence of magnesian olivine phenocrysts ( Fo78) are consistent with a primitive (i.e. unevolved) geochemistry. The nature and composition of clinopyroxene (augite and pigeonite), plagioclase feldspar (labradorite) and Fe-Ti oxides (mostly ilmenite and magnetite) are also discussed, with implications drawn with respect to the geodynamics. High MgO magmas and rocks such as picrites are generally considered to be indicative of plume magmatism, formed by high degrees of partial melting in, e.g. the high-temperature region of a plume head. Recent age data is consistent with a model in which the Deccan LIP picritic magmatism is associated with the main phase of Deccan Trap activity at 66 Ma, as a result of a syn- to post rifting phase associated with the impact of the Rèunion mantle plume. It is speculated that the differentiation of primary olivine basaltic magma of picritic composition, may have been the mechanism for the generation of alkalic basalts which occurs in the Deccan Trap basaltic sequence.

Investigation of a four-body coupling in the one-dimensional extended Penson-Kolb-Hubbard model

NASA Astrophysics Data System (ADS)

Ding, Hanqin; Ma, Xiaojuan; Zhang, Jun

2017-09-01

The experimental advances in cold fermion gases motivates the investigation of a one-dimensional (1D) correlated electronic system by incorporating a four-body coupling. Using the low-energy field theory scheme and focusing on the weak-coupling regime, we extend the 1D Penson-Kolb-Hubbard (PKH) model at half filling. It is found that the additional four-body interaction may significantly modify the quantum phase diagram, favoring the presence of the superconducting phase even in the case of two-body repulsions.

Seismic constraints on a large dyking event and initiation of a transform fault zone in Western Gulf of Aden

NASA Astrophysics Data System (ADS)

Ahmed, AbdulHakim; Doubre, Cecile; Leroy, Sylvie; Perrot, Julie; Audin, Laurence; Rolandone, Frederique; Keir, Derek; Al-Ganad, Ismael; Sholan, Jamal; Khanbari, Khaled; Mohamed, Kassim; Vergne, Jerome; Jacques, Eric; Nercessian, Alex

2013-04-01

In November 2010, a large number of events were recorded by the world seismic networks showing important activity occurring along the western part of the Aden Ridge. West of the Shulka El Sheik fracture zone, events in this large seismic swarm (magnitudes above 5) occurred in a complex area, where the change of both the ridge direction and the bathymetry suggest the propagation of the ridge into a continental lithosphere and the influence of the Afar plume. We combine several sets of data from permanent networks and temporary 3C broad stations installed after the beginning of the event along the southern and eastern coasts of Yemen and Djibouti respectively, we located more than 600 earthquakes with magnitudes ranging from 2.5 to 5.6 that occurred during the first months following the first event. The spatial distribution of the main seismicity reveals a very clear N115° -trending alignment, parallel to the mean direction of the en-echelon spreading segments that form the ridge at this longitude. Half of the events, which represent half of the total seismic energy released during the first months, are located in the central third section of the segment. Here several volcanic cones and recent lava flows observed from bathymetric and acoustic reflectivity data during the Tadjouraden cruise (Audin, 1999, Dauteuil et al., 2001) constitute the sea floor. In addition to this main activity, two small groups of events suggest the activiation of landslides into a large fan and the activity in a volcanic area 50 km due east from the main active zone. The time evolution of the seismicity shows several bursts of activity. Some of them are clearly related to sudden activities within the volcanic areas, when others exhibit horizontal migration of the events, with velocity around ˜ 1 km/h. The time-space evolution of the seismicity clearly reveals the intrusion of dykes associated with magma propagation from the crustal magmatic centres into the rift zone. Taking into account

A unique Austin Chalk reservoir, Van field, Van Zandt County, Texas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lowe, J.T.

1990-09-01

Significant shallow oil production from the Austin Chalk was established in the Van field, Van Zandt County, in East Texas in the late 1980s. The Van field structure is a complexly faulted domal anticline created by salt intrusion. The Woodbine sands, which underlie the Austin Chalk, have been and continue to be the predominant reservoir rocks in the field. Evidence indicates that faults provided vertical conduits for migration of Woodbine oil into the Austin Chalk where it was trapped along the structural crest. The most prolific Austin Chalk production is on the upthrown side of the main field fault, asmore » is the Woodbine. The Austin Chalk is a soft, white to light gray limestone composed mostly of coccoliths with some pelecypods. Unlike the Austin Chalk in the Giddings and Pearsall fields, the chalk at Van was not as deeply buried and therefore did not become brittle and susceptible to tensional or cryptic fracturing. The shallow burial in the Van field was also important in that it allowed the chalk to retain primary microporosity. The production comes entirely from this primary porosity. In addition to the structural position and underlying oil source from the Woodbine, the depositional environment and associated lithofacies are also keys to the reservoir quality in the Van field as demonstrated by cores from the upthrown and downthrown (less productive) sides of the main field fault. It appears that at the time of Austin Chalk deposition, the main field fault was active and caused the upthrown side to be a structural high and a more agreeable environment for benthonic organisms such as pelecypods and worms. The resulting bioturbation enhanced the reservoir's permeability enough to allow migration and entrapment of the oil. Future success in exploration for analogous Austin Chalk reservoirs will require the combination of a favorable environment of deposition, a nearby Woodbine oil source, and a faulted trap that will provide the conduit for migration.« less

Stable-unstable transition for a Bose-Hubbard chain coupled to an environment

NASA Astrophysics Data System (ADS)

Guo, Chu; de Vega, Ines; Schollwöck, Ulrich; Poletti, Dario

2018-05-01

Interactions in quantum systems may induce transitions to exotic correlated phases of matter which can be vulnerable to coupling to an environment. Here, we study the stability of a Bose-Hubbard chain coupled to a bosonic bath at zero and nonzero temperature. We show that only above a critical interaction the chain loses bosons and its properties are significantly affected. The transition is of a different nature than the superfluid-Mott-insulator transition and occurs at a different critical interaction. We explain such a stable-unstable transition by the opening of a global charge gap. The comparison of accurate matrix product state simulations to approximative approaches that miss this transition reveals its many-body origin.

Rényi Entropies from Random Quenches in Atomic Hubbard and Spin Models.

PubMed

Elben, A; Vermersch, B; Dalmonte, M; Cirac, J I; Zoller, P

2018-02-02

We present a scheme for measuring Rényi entropies in generic atomic Hubbard and spin models using single copies of a quantum state and for partitions in arbitrary spatial dimensions. Our approach is based on the generation of random unitaries from random quenches, implemented using engineered time-dependent disorder potentials, and standard projective measurements, as realized by quantum gas microscopes. By analyzing the properties of the generated unitaries and the role of statistical errors, with respect to the size of the partition, we show that the protocol can be realized in existing quantum simulators and used to measure, for instance, area law scaling of entanglement in two-dimensional spin models or the entanglement growth in many-body localized systems.

Rényi Entropies from Random Quenches in Atomic Hubbard and Spin Models

NASA Astrophysics Data System (ADS)

Elben, A.; Vermersch, B.; Dalmonte, M.; Cirac, J. I.; Zoller, P.

2018-02-01

We present a scheme for measuring Rényi entropies in generic atomic Hubbard and spin models using single copies of a quantum state and for partitions in arbitrary spatial dimensions. Our approach is based on the generation of random unitaries from random quenches, implemented using engineered time-dependent disorder potentials, and standard projective measurements, as realized by quantum gas microscopes. By analyzing the properties of the generated unitaries and the role of statistical errors, with respect to the size of the partition, we show that the protocol can be realized in existing quantum simulators and used to measure, for instance, area law scaling of entanglement in two-dimensional spin models or the entanglement growth in many-body localized systems.

Counting local integrals of motion in disordered spinless-fermion and Hubbard chains

NASA Astrophysics Data System (ADS)

Mierzejewski, Marcin; Kozarzewski, Maciej; Prelovšek, Peter

2018-02-01

We develop a procedure which systematically generates all conserved operators in the disordered models of interacting fermions. Among these operators, we identify and count the independent and local integrals of motion (LIOM), which represent the hallmark of the many-body localization (MBL). The method is tested first on the prototype disordered chain of interacting spinless fermions. As expected for full MBL, we find for large enough disorder NM=2M-1 independent and quasilocal LIOM with support on M consecutive sites. On the other hand, the study of the disordered Hubbard chain reveals that 3M-1

Ground-State of the Bose-Hubbard Model

NASA Astrophysics Data System (ADS)

Mancini, J. D.; Fessatidis, V.; Bowen, S. P.; Murawski, R. K.; Maly, J.

The Bose-Hubbard Model represents a s simple theoretical model to describe the physics of interacting Boson systems. In particular it has proved to be an effective description of a number of physical systems such as arrays of Josephson arrays as well as dilute alkali gases in optical lattices. Here we wish to study the ground-state of this system using two disparate but related moments calculational schemes: the Lanczos (tridiagonal) method as well as a Generalized moments approach. The Hamiltonian to be studied is given by (in second-quantized notation): H = - t ∑ < i , j > bi†bj +U/2 ∑ inini - 1 - μ ∑ ini . Here i is summed over all lattice sites, and < i , j > denotes summation over all neighbhoring sites i and j, while bi† and bi are bosonic creation and annihilation operators. ni = bi†bi gives the number of particles on site i. Parameter t is the hopping amplitude, describing mobility of bosons in the lattice. Parameter U describes the on-site interaction, repulsive, if U > 0 , and attractive for U < 0 . μ is the chemical potential. Both the ground-state energy and energy gap are evaluated as a function of t, U and μ.

Stirling Powered Van Progam overview

NASA Technical Reports Server (NTRS)

Shaltens, R. K.

1986-01-01

The Stirling Powered Van Program (SPVP) is a multiyear, multiphase program to evaluate the automotive Stirling engine (ASE) in Air Force vans under realistic conditions. The objective of the SPVP is to transfer to manufacturer and end user(s) (i.e., on the path to commercialization) the second-generation Mod 2 ASE upon completion of the Automotive Stirling Engine Program in 1987. In order to meet this objective, the SPVP must establish Stirling performance, integrity, reliability, durability and maintainability. The ASE program background leading to the van program is reviewed and plans for evaluating the kinematic Stirling engine in Air Force vans examined. Also discussed are the NASA technology transfers to industry that have been accomplished and those which are currently being developed.

Past and projected future changes in snowpack and soil frost at the Hubbard Brook Experimental Forest, New Hampshire, USA

Treesearch

John L. Campbell; Scott V. Ollinger; Gerald N. Flerchinger; Haley Wicklein; Katharine Hayhoe; Amey S. Bailey

2010-01-01

Long-term data from the Hubbard Brook Experimental Forest in New Hampshire show that air temperature has increased by about 1 °C over the last half century. The warmer climate has caused significant declines in snow depth, snow water equivalent and snow cover duration. Paradoxically, it has been suggested that warmer air temperatures may result in colder soils...

Emergent low-energy bound states in the two-orbital Hubbard model

NASA Astrophysics Data System (ADS)

Núñez-Fernández, Y.; Kotliar, G.; Hallberg, K.

2018-03-01

A repulsive Coulomb interaction between electrons in different orbitals in correlated materials can give rise to bound quasiparticle states. We study the nonhybridized two-orbital Hubbard model with intra- (inter)orbital interaction U (U12) and different bandwidths using an improved dynamical mean-field theory numerical technique which leads to reliable spectra on the real energy axis directly at zero temperature. We find that a finite density of states at the Fermi energy in one band is correlated with the emergence of well-defined quasiparticle states at excited energies Δ =U -U12 in the other band. These excitations are interband holon-doublon bound states. At the symmetric point U =U12 , the quasiparticle peaks are located at the Fermi energy, leading to a simultaneous and continuous Mott transition settling a long-standing controversy.

Ultrasoft pseudopotentials and Hubbard U values for rare-earth elements (Re=La-Lu) guided by HSE06 calculations

NASA Astrophysics Data System (ADS)

Topsakal, Mehmet; Umemoto, Koichiro; Wentzcovitch, Renata

2014-03-01

The lanthanide series of the periodic table comprises fifteen members ranging from La to Lu - the rare-earth (Re) elements. They exhibit unique (and mostly unexplored) chemical properties depending on the fillings of 4f-orbitals. Due to strong electronic correlation, 4f valence electrons are incorrectly described by standard DFT functionals. In order to cope with these inefficiencies, the DFT+U method is often employed where Hubbard-type U is introduced into the standard DFT. Another approach is to use hybrid functionals. Both improve the treatment of strongly correlated electrons. However, DFT+U suffers from ambiguity of U while hybrid functionals suffer from extremely demanding computational costs. Here we provide Vanderbilt type ultrasoft pseudopotentials for Re elements with suggested U values allowing efficient plane-wave calculations. Hubbard U values are determined according to HSE06 calculations on Re-nitrides (ReN). Generated pseudopotentials were further tested on some Re-cobaltite (Re-CoO3) perovskites. Alternative pseudopotentials with f-electrons kept frozen in the core of pseudopotential are also provided and possible outcomes are addressed. We believe that these new pseudopotentials with suggested U values will allow further studies on rare-earth materials.

Floquet Engineering of Correlated Tunneling in the Bose-Hubbard Model with Ultracold Atoms.

PubMed

Meinert, F; Mark, M J; Lauber, K; Daley, A J; Nägerl, H-C

2016-05-20

We report on the experimental implementation of tunable occupation-dependent tunneling in a Bose-Hubbard system of ultracold atoms via time-periodic modulation of the on-site interaction energy. The tunneling rate is inferred from a time-resolved measurement of the lattice site occupation after a quantum quench. We demonstrate coherent control of the tunneling dynamics in the correlated many-body system, including full suppression of tunneling as predicted within the framework of Floquet theory. We find that the tunneling rate explicitly depends on the atom number difference in neighboring lattice sites. Our results may open up ways to realize artificial gauge fields that feature density dependence with ultracold atoms.

Phase Diagram of the Bose Hubbard Model with Weak Links

NASA Astrophysics Data System (ADS)

Hettiarachchilage, Kalani; Rousseau, Valy; Tam, Ka-Ming; Moreno, Juana; Jarrell, Mark; Sheehy, Daniel

2012-02-01

We study the ground state phase diagram of strongly interacting ultracold Bose gas in a one-dimensional optical lattice with a tunable weak link, by means of Quantum Monte Carlo simulation. This model contains an on-site repulsive interaction (U) and two different near-neighbor hopping terms, J and t, for the weak link and the remainder of the chain, respectively. We show that by reducing the strength of J, a novel intermediate phase develops which is compressible and non-superfluid. This novel phase is identified as a Normal Bose Liquid (NBL) which does not appear in the phase diagram of the homogeneous bosonic Hubbard model. Further, we find a linear variation of the phase boundary of Normal Bose Liquid (NBL) to SuperFluid (SF) as a function of the strength of the weak link. These results may provide a new path to design advanced atomtronic devices in the future.

vanC Cluster of Vancomycin-Resistant Enterococcus gallinarum BM4174

PubMed Central

Arias, Cesar A.; Courvalin, Patrice; Reynolds, Peter E.

2000-01-01

Glycopeptide-resistant enterococci of the VanC type synthesize UDP-muramyl-pentapeptide[d-Ser] for cell wall assembly and prevent synthesis of peptidoglycan precursors ending in d-Ala. The vanC cluster of Enterococcus gallinarum BM4174 consists of five genes: vanC-1, vanXYC, vanT, vanRC, and vanSC. Three genes are sufficient for resistance: vanC-1 encodes a ligase that synthesizes the dipeptide d-Ala-d-Ser for addition to UDP-MurNAc-tripeptide, vanXYC encodes a d,d-dipeptidase–carboxypeptidase that hydrolyzes d-Ala-d-Ala and removes d-Ala from UDP-MurNAc-pentapeptide[d-Ala], and vanT encodes a membrane-bound serine racemase that provides d-Ser for the synthetic pathway. The three genes are clustered: the start codons of vanXYC and vanT overlap the termination codons of vanC-1 and vanXYC, respectively. Two genes which encode proteins with homology to the VanS-VanR two-component regulatory system were present downstream from the resistance genes. The predicted amino acid sequence of VanRC exhibited 50% identity to VanR and 33% identity to VanRB. VanSC had 40% identity to VanS over a region of 308 amino acids and 24% identity to VanSB over a region of 285 amino acids. All residues with important functions in response regulators and histidine kinases were conserved in VanRC and VanSC, respectively. Induction experiments based on the determination of d,d-carboxypeptidase activity in cytoplasmic extracts confirmed that the genes were expressed constitutively. Using a promoter-probing vector, regions upstream from the resistance and regulatory genes were identified that have promoter activity. PMID:10817725

Dynamics of a quantum phase transition in the Bose-Hubbard model: Kibble-Zurek mechanism and beyond

NASA Astrophysics Data System (ADS)

Shimizu, Keita; Kuno, Yoshihito; Hirano, Takahiro; Ichinose, Ikuo

2018-03-01

In this paper, we study the dynamics of the Bose-Hubbard model by using time-dependent Gutzwiller methods. In particular, we vary the parameters in the Hamiltonian as a function of time, and investigate the temporal behavior of the system from the Mott insulator to the superfluid (SF) crossing a second-order phase transition. We first solve a time-dependent Schrödinger equation for the experimental setup recently done by Braun et al. [Proc. Natl. Acad. Sci. USA 112, 3641 (2015)] and show that the numerical and experimental results are in fairly good agreement. However, these results disagree with the Kibble-Zurek scaling. From our numerical study, we reveal a possible source of the discrepancy. Next, we calculate the critical exponents of the correlation length and vortex density in addition to the SF order parameter for a Kibble-Zurek protocol. We show that beside the "freeze" time t ̂, there exists another important time, teq, at which an oscillating behavior of the SF amplitude starts. From calculations of the exponents of the correlation length and vortex density with respect to a quench time τQ, we obtain a physical picture of a coarsening process. Finally, we study how the system evolves after the quench. We give a global picture of dynamics of the Bose-Hubbard model.

Characterisation of the selective binding of antibiotics vancomycin and teicoplanin by the VanS receptor regulating type A vancomycin resistance in the enterococci.

PubMed

Hughes, C S; Longo, E; Phillips-Jones, M K; Hussain, R

2017-08-01

A-type resistance towards "last-line" glycopeptide antibiotic vancomycin in the leading hospital acquired infectious agent, the enterococci, is the most common in the UK. Resistance is regulated by the VanR A S A two-component system, comprising the histidine sensor kinase VanS A and the partner response regulator VanR A . The nature of the activating ligand for VanS A has not been identified, therefore this work sought to identify and characterise ligand(s) for VanS A . In vitro approaches were used to screen the structural and activity effects of a range of potential ligands with purified VanS A protein. Of the screened ligands (glycopeptide antibiotics vancomycin and teicoplanin, and peptidoglycan components N-acetylmuramic acid, D-Ala-D-Ala and Ala-D-y-Glu-Lys-D-Ala-D-Ala) only glycopeptide antibiotics vancomycin and teicoplanin were found to bind VanS A with different affinities (vancomycin 70μM; teicoplanin 30 and 170μM), and were proposed to bind via exposed aromatic residues tryptophan and tyrosine. Furthermore, binding of the antibiotics induced quicker, longer-lived phosphorylation states for VanS A , proposing them as activators of type A vancomycin resistance in the enterococci. Copyright © 2017 Diamond Light Source Ltd. Published by Elsevier B.V. All rights reserved.

Band gap depiction of quaternary FeMnTiAl alloy using Hubbard (U) potential

NASA Astrophysics Data System (ADS)

Bhat, Tahir Mohiuddin; Yousuf, Saleem; Khandy, Shakeel Ahmad; Gupta, Dinesh C.

2018-05-01

We have employed self-consistent ab-initio calculations to investigate new quaternary alloy FeMnTiAl by applying Hubbard potential (U). The alloy is found to be stable in ferromagnetic phase with cubic structure. The alloy shows half-metallic (HM) ferromagnet character. The values of minority band gap FeMnTiAl are found to be 0.33 eV respectively. Electronic charge density reveals that both types of bonds covalent as well as ionic are present in the alloy. Thus the new quaternary alloy can be proved as vital contender for spin valves and spin generator devices.

Signatures of the Mott transition in the antiferromagnetic state of the two-dimensional Hubbard model

DOE PAGES

Fratino, L.; Sémon, P.; Charlebois, M.; ...

2017-06-06

The properties of a phase with large correlation length can be strongly influenced by the underlying normal phase. Here, we illustrate this by studying the half-filled two-dimensional Hubbard model using cellular dynamical mean-field theory with continuous-time quantum Monte Carlo. Sharp crossovers in the mechanism that favors antiferromagnetic correlations and in the corresponding local density of states are observed. We found that these crossovers occur at values of the interaction strength U and temperature T that are controlled by the underlying normal-state Mott transition.

Hubbard pair cluster in the external fields. Studies of the magnetic properties

NASA Astrophysics Data System (ADS)

Balcerzak, T.; Szałowski, K.

2018-06-01

The magnetic properties of the two-site Hubbard cluster (dimer or pair), embedded in the external electric and magnetic fields and treated as the open system, are studied by means of the exact diagonalization of the Hamiltonian. The formalism of the grand canonical ensemble is adopted. The phase diagrams, on-site magnetizations, spin-spin correlations, mean occupation numbers and hopping energy are investigated and illustrated in figures. An influence of temperature, mean electron concentration, Coulomb U parameter and external fields on the quantities of interest is presented and discussed. In particular, the anomalous behaviour of the magnetization and correlation function vs. temperature near the critical magnetic field is found. Also, the effect of magnetization switching by the external fields is demonstrated.

Stripe order in the underdoped region of the two-dimensional Hubbard model

NASA Astrophysics Data System (ADS)

Zheng, Bo-Xiao; Chung, Chia-Min; Corboz, Philippe; Ehlers, Georg; Qin, Ming-Pu; Noack, Reinhard M.; Shi, Hao; White, Steven R.; Zhang, Shiwei; Chan, Garnet Kin-Lic

2017-12-01

Competing inhomogeneous orders are a central feature of correlated electron materials, including the high-temperature superconductors. The two-dimensional Hubbard model serves as the canonical microscopic physical model for such systems. Multiple orders have been proposed in the underdoped part of the phase diagram, which corresponds to a regime of maximum numerical difficulty. By combining the latest numerical methods in exhaustive simulations, we uncover the ordering in the underdoped ground state. We find a stripe order that has a highly compressible wavelength on an energy scale of a few kelvin, with wavelength fluctuations coupled to pairing order. The favored filled stripe order is different from that seen in real materials. Our results demonstrate the power of modern numerical methods to solve microscopic models, even in challenging settings.

On the ab initio evaluation of Hubbard parameters. II. The κ-(BEDT-TTF)2Cu[N(CN)2]Br crystal

NASA Astrophysics Data System (ADS)

Fortunelli, Alessandro; Painelli, Anna

1997-05-01

A previously proposed approach for the ab initio evaluation of Hubbard parameters is applied to BEDT-TTF dimers. The dimers are positioned according to four geometries taken as the first neighbors from the experimental data on the κ-(BEDT-TTF)2Cu[N(CN)2]Br crystal. RHF-SCF, CAS-SCF and frozen-orbital calculations using the 6-31G** basis set are performed with different values of the total charge, allowing us to derive all the relevant parameters. It is found that the electronic structure of the BEDT-TTF planes is adequately described by the standard Extended Hubbard Model, with the off-diagonal electron-electron interaction terms (X and W) of negligible size. The derived parameters are in good agreement with available experimental data. Comparison with previous theoretical estimates shows that the t values compare well with those obtained from Extended Hückel Theory (whereas the minimal basis set estimates are completely unreliable). On the other hand, the Uaeff values exhibit an appreciable dependence on the chemical environment.

Seismic constraints on a large dyking event in Western Gulf of Aden

NASA Astrophysics Data System (ADS)

Ahmed, A.; Doubre, C.; Leroy, S.; Perrot, J.; Audin, L.; Rolandone, F.; Keir, D.; Al-Ganad, I.; Khanbari, K.; Mohamed, K.; Vergne, J.; Jacques, E.; Nercessian, A.

2012-04-01

In November 2010, a large number of events were recorded by the world seismic networks showing important activity occurring along the western part of the Aden Ridge. West of the Shulka El Sheik transform zone, events in this large seismic swarm (magnitudes above 5) occurred in a complex area, where the change of both the ridge direction and the bathymetry suggest the propagation of the ridge into a continental lithosphere and the influence of the thermal anomaly of the Afar Hot Spot. We combine several sets of data from permanent networks and temporary 3C broad stations installed after the beginning of the event along the southern and eastern coasts of Yemen and Djibouti respectively, we located more than 600 earthquakes with magnitudes ranging from 2.5 to 5.6 that occurred during the first months following the first event. The spatial distribution of the main seismicity reveals a very clear N115°-trending alignment, parallel to the mean direction of the en-echelon spreading segments that form the ridge at this longitude. Half of the events, which represent half of the total seismic energy released during the first months, are located in the central third section of the segment. Here several volcanic cones and recent lava flows observed from bathymetric and acoustic reflectivity data during the Tadjouraden cruise (Audin, 1999, Dauteuil et al., 2001) constitute the sea floor. In addition to this main activity, two small groups of events suggest the activiation of landslides into a large fan and the activity in a volcanic area 50 km due east from the main active zone. The time evolution of the seismicity shows several bursts of activity. Some of them are clearly related to sudden activities within the volcanic areas, when others exhibit horizontal migration of the events, with velocity around ~ 1 km/h. The time-space evolution of the seismicity clearly reveals the intrusion of dykes associated with magma propagation from the crustal magmatic centres into the rift

Bond Order Correlations in the 2D Hubbard Model

NASA Astrophysics Data System (ADS)

Moore, Conrad; Abu Asal, Sameer; Yang, Shuxiang; Moreno, Juana; Jarrell, Mark

We use the dynamical cluster approximation to study the bond correlations in the Hubbard model with next nearest neighbor (nnn) hopping to explore the region of the phase diagram where the Fermi liquid phase is separated from the pseudogap phase by the Lifshitz line at zero temperature. We implement the Hirsch-Fye cluster solver that has the advantage of providing direct access to the computation of the bond operators via the decoupling field. In the pseudogap phase, the parallel bond order susceptibility is shown to persist at zero temperature while it vanishes for the Fermi liquid phase which allows the shape of the Lifshitz line to be mapped as a function of filling and nnn hopping. Our cluster solver implements NVIDIA's CUDA language to accelerate the linear algebra of the Quantum Monte Carlo to help alleviate the sign problem by allowing for more Monte Carlo updates to be performed in a reasonable amount of computation time. Work supported by the NSF EPSCoR Cooperative Agreement No. EPS-1003897 with additional support from the Louisiana Board of Regents.

Absence of ballistic charge transport in the half-filled 1D Hubbard model

NASA Astrophysics Data System (ADS)

Carmelo, J. M. P.; Nemati, S.; Prosen, T.

2018-05-01

Whether in the thermodynamic limit of lattice length L → ∞, hole concentration mηz = - 2 Sηz/L = 1 -ne → 0, nonzero temperature T > 0, and U / t > 0 the charge stiffness of the 1D Hubbard model with first neighbor transfer integral t and on-site repulsion U is finite or vanishes and thus whether there is or there is no ballistic charge transport, respectively, remains an unsolved and controversial issue, as different approaches yield contradictory results. (Here Sηz = - (L -Ne) / 2 is the η-spin projection and ne =Ne / L the electronic density.) In this paper we provide an upper bound on the charge stiffness and show that (similarly as at zero temperature), for T > 0 and U / t > 0 it vanishes for mηz → 0 within the canonical ensemble in the thermodynamic limit L → ∞. Moreover, we show that at high temperature T → ∞ the charge stiffness vanishes as well within the grand-canonical ensemble for L → ∞ and chemical potential μ →μu where (μ -μu) ≥ 0 and 2μu is the Mott-Hubbard gap. The lack of charge ballistic transport indicates that charge transport at finite temperatures is dominated by a diffusive contribution. Our scheme uses a suitable exact representation of the electrons in terms of rotated electrons for which the numbers of singly occupied and doubly occupied lattice sites are good quantum numbers for U / t > 0. In contrast to often less controllable numerical studies, the use of such a representation reveals the carriers that couple to the charge probes and provides useful physical information on the microscopic processes behind the exotic charge transport properties of the 1D electronic correlated system under study.

Softwaremodule voor het Simuleren van de Gevolgen van Raketonderschepping (The Dutch Program for the Simulation of Missile Intercept Effects)

DTIC Science & Technology

2007-07-01

effects (Softwaremodule voor het simuleren van de gevolgen van raketonderschepping) 11 . AUTHOR(S) Dr E. Abadjieva, MSc R.P. Sterkenburg, MSc F. Bouquet...Softwaremnodule voor het simuleren van de gevolgen van raketonderschepping D)attini Juli 2007 Auteur(s) dr. F. Abadjicva ir. R.P Sterkenburg ir. F. Bouquet ir...P.W. D)ouip Rubricering rapport O)ngerubri ceerd Vastgesteld door Maj R. 11 . Jongkinid Vastgesteld d.d. 12 juni 2007 (Deze nitining mizil-4 sict

Emergent low-energy bound states in the two-orbital Hubbard model

DOE PAGES

Nunez-Fernandez, Y.; Kotliar, G.; Hallberg, K.

2018-03-30

A repulsive Coulomb interaction between electrons in different orbitals in correlated materials can give rise to bound quasiparticle states. We study the nonhybridized two-orbital Hubbard model with intra- (inter)orbital interaction U (U 12) and different bandwidths using an improved dynamical mean-field theory numerical technique which leads to reliable spectra on the real energy axis directly at zero temperature. We find that a finite density of states at the Fermi energy in one band is correlated with the emergence of well-defined quasiparticle states at excited energies Δ = U - U 12 in the other band. These excitations are interband holon-doublonmore » bound states. At the symmetric point U = U 12, the quasiparticle peaks are located at the Fermi energy, leading to a simultaneous and continuous Mott transition settling a long-standing controversy.« less

Time evolution of the one-dimensional Jaynes-Cummings-Hubbard Hamiltonian

DOE Office of Scientific and Technical Information (OSTI.GOV)

Makin, M. I.; Hill, Charles D.; Greentree, Andrew D.

2009-10-15

The Jaynes-Cummings-Hubbard (JCH) system describes a network of single-mode photonic cavities connected via evanescent coupling. Each cavity contains a single two-level system which can be tuned in resonance with the cavity. Here, we explore the behavior of single excitations (where an excitation can be either photonic or atomic) in the linear JCH system, which describes a coupled cavity waveguide. We use direct, analytic diagonalization of the Hamiltonian to study cases where intercavity coupling is either uniform or varies parabolically along the chain. Both excitations located in a single cavity, as well as one excitation as a Gaussian pulse spread overmore » many cavities, are investigated as initial states. We predict unusual behavior of this system in the time domain, including slower than expected propagation of the excitation and also splitting of the excitation into two distinct pulses, which travel at distinct speeds. In certain limits, we show that the JCH system mimics two Heisenberg spin chains.« less

Antiferromagnetic order in the Hubbard model on the Penrose lattice

NASA Astrophysics Data System (ADS)

Koga, Akihisa; Tsunetsugu, Hirokazu

2017-12-01

We study an antiferromagnetic order in the ground state of the half-filled Hubbard model on the Penrose lattice and investigate the effects of quasiperiodic lattice structure. In the limit of infinitesimal Coulomb repulsion U →+0 , the staggered magnetizations persist to be finite, and their values are determined by confined states, which are strictly localized with thermodynamics degeneracy. The magnetizations exhibit an exotic spatial pattern, and have the same sign in each of cluster regions, the size of which ranges from 31 sites to infinity. With increasing U , they continuously evolve to those of the corresponding spin model in the U =∞ limit. In both limits of U , local magnetizations exhibit a fairly intricate spatial pattern that reflects the quasiperiodic structure, but the pattern differs between the two limits. We have analyzed this pattern change by a mode analysis by the singular value decomposition method for the fractal-like magnetization pattern projected into the perpendicular space.

Interaction quantum quenches in the one-dimensional Fermi-Hubbard model

NASA Astrophysics Data System (ADS)

Heidrich-Meisner, Fabian; Bauer, Andreas; Dorfner, Florian; Riegger, Luis; Orso, Giuliano

2016-05-01

We discuss the nonequilibrium dynamics in two interaction quantum quenches in the one-dimensional Fermi-Hubbard model. First, we study the decay of the Néel state as a function of interaction strength. We observe a fast charge dynamics over which double occupancies are built up, while the long-time decay of the staggered moment is controlled by spin excitations, corroborated by the analysis of the entanglement dynamics. Second, we investigate the formation of Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) correlations in a spin-imbalanced system in quenches from the noninteracting case to attractive interactions. Even though the quench puts the system at a finite energy density, peaks at the characteristic FFLO quasimomenta are visible in the quasi-momentum distribution function, albeit with an exponential decay of s-wave pairing correlations. We also discuss the imprinting of FFLO correlations onto repulsively bound pairs and their rapid decay in ramps. Supported by the DFG (Deutsche Forschungsgemeinschaft) via FOR 1807.

Global SO(3) x SO(3) x U(1) symmetry of the Hubbard model on bipartite lattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carmelo, J.M.P., E-mail: carmelo@fisica.uminho.p; Ostlund, Stellan; Sampaio, M.J.

2010-08-15

In this paper the global symmetry of the Hubbard model on a bipartite lattice is found to be larger than SO(4). The model is one of the most studied many-particle quantum problems, yet except in one dimension it has no exact solution, so that there remain many open questions about its properties. Symmetry plays an important role in physics and often can be used to extract useful information on unsolved non-perturbative quantum problems. Specifically, here it is found that for on-site interaction U {ne} 0 the local SU(2) x SU(2) x U(1) gauge symmetry of the Hubbard model on amore » bipartite lattice with N{sub a}{sup D} sites and vanishing transfer integral t = 0 can be lifted to a global [SU(2) x SU(2) x U(1)]/Z{sub 2}{sup 2} = SO(3) x SO(3) x U(1) symmetry in the presence of the kinetic-energy hopping term of the Hamiltonian with t > 0. (Examples of a bipartite lattice are the D-dimensional cubic lattices of lattice constant a and edge length L = N{sub a}a for which D = 1, 2, 3,... in the number N{sub a}{sup D} of sites.) The generator of the new found hidden independent charge global U(1) symmetry, which is not related to the ordinary U(1) gauge subgroup of electromagnetism, is one half the rotated-electron number of singly occupied sites operator. Although addition of chemical-potential and magnetic-field operator terms to the model Hamiltonian lowers its symmetry, such terms commute with it. Therefore, its 4{sup N}{sub a}{sup D} energy eigenstates refer to representations of the new found global [SU(2) x SU(2) x U(1)]/Z{sub 2}{sup 2} = SO(3) x SO(3) x U(1) symmetry. Consistently, we find that for the Hubbard model on a bipartite lattice the number of independent representations of the group SO(3) x SO(3) x U(1) equals the Hilbert-space dimension 4{sup N}{sub a}{sup D}. It is confirmed elsewhere that the new found symmetry has important physical consequences.« less

Beslisbevoegdheden en Verantwoordelijkheden van de Uitgestegen Soldaat. Deel A: Verplaatsen van Beslisbevoegdheden (Authority and Responsibility of the Dismounted Soldier. Part A. Empowering the Dismounted Soldier)

DTIC Science & Technology

2007-04-01

en verantwoordelijkheden van de uitgestegen soldaat Deel A: verplaatsen van beslisbevoegdheden Datumn april 2007 Auteur (s) R. de Bruin ITE. van Bernmel...Admiraal, Bureau SMP Auteur (s) R. de Bruin Program maleider Projectleider I.E. van Bemnmel dr. W.A. Lotens, A.J. van Vliet, A.J. van Vijet TNO Defensie en...Leadership Theory en wordt relevant geacht voor de ontvangers van aanvullende beslisbevoegdheden. 2.1.3 Het oogmerk van de hogere commandant Een ander

The phosphotransferase VanU represses expression of four qrr genes antagonizing VanO-mediated quorum-sensing regulation in Vibrio anguillarum

PubMed Central

Weber, Barbara; Lindell, Kristoffer; El Qaidi, Samir; Hjerde, Erik; Willassen, Nils-Peder

2011-01-01

Vibrio anguillarum utilizes quorum sensing to regulate stress responses required for survival in the aquatic environment. Like other Vibrio species, V. anguillarum contains the gene qrr1, which encodes the ancestral quorum regulatory RNA Qrr1, and phosphorelay quorum-sensing systems that modulate the expression of small regulatory RNAs (sRNAs) that destabilize mRNA encoding the transcriptional regulator VanT. In this study, three additional Qrr sRNAs were identified. All four sRNAs were positively regulated by σ54 and the σ54-dependent response regulator VanO, and showed a redundant activity. The Qrr sRNAs, together with the RNA chaperone Hfq, destabilized vanT mRNA and modulated expression of VanT-regulated genes. Unexpectedly, expression of all four qrr genes peaked at high cell density, and exogenously added N-acylhomoserine lactone molecules induced expression of the qrr genes at low cell density. The phosphotransferase VanU, which phosphorylates and activates VanO, repressed expression of the Qrr sRNAs and stabilized vanT mRNA. A model is presented proposing that VanU acts as a branch point, aiding cross-regulation between two independent phosphorelay systems that activate or repress expression of the Qrr sRNAs, giving flexibility and precision in modulating VanT expression and inducing a quorum-sensing response to stresses found in a constantly changing aquatic environment. PMID:21948044

The phosphotransferase VanU represses expression of four qrr genes antagonizing VanO-mediated quorum-sensing regulation in Vibrio anguillarum.

PubMed

Weber, Barbara; Lindell, Kristoffer; El Qaidi, Samir; Hjerde, Erik; Willassen, Nils-Peder; Milton, Debra L

2011-12-01

Vibrio anguillarum utilizes quorum sensing to regulate stress responses required for survival in the aquatic environment. Like other Vibrio species, V. anguillarum contains the gene qrr1, which encodes the ancestral quorum regulatory RNA Qrr1, and phosphorelay quorum-sensing systems that modulate the expression of small regulatory RNAs (sRNAs) that destabilize mRNA encoding the transcriptional regulator VanT. In this study, three additional Qrr sRNAs were identified. All four sRNAs were positively regulated by σ(54) and the σ(54)-dependent response regulator VanO, and showed a redundant activity. The Qrr sRNAs, together with the RNA chaperone Hfq, destabilized vanT mRNA and modulated expression of VanT-regulated genes. Unexpectedly, expression of all four qrr genes peaked at high cell density, and exogenously added N-acylhomoserine lactone molecules induced expression of the qrr genes at low cell density. The phosphotransferase VanU, which phosphorylates and activates VanO, repressed expression of the Qrr sRNAs and stabilized vanT mRNA. A model is presented proposing that VanU acts as a branch point, aiding cross-regulation between two independent phosphorelay systems that activate or repress expression of the Qrr sRNAs, giving flexibility and precision in modulating VanT expression and inducing a quorum-sensing response to stresses found in a constantly changing aquatic environment.

Hypergeometric continuation of divergent perturbation series: I. Critical exponents of the Bose-Hubbard model

NASA Astrophysics Data System (ADS)

Sanders, Sören; Holthaus, Martin

2017-10-01

We study the connection between the exponent of the order parameter of the Mott insulator-to-superfluid transition occurring in the two-dimensional Bose-Hubbard model, and the divergence exponents of its one- and two-particle correlation functions. We find that at the multicritical points all divergence exponents are related to each other, allowing us to express the critical exponent in terms of one single divergence exponent. This approach correctly reproduces the critical exponent of the three-dimensional XY universality class. Because divergence exponents can be computed in an efficient manner by hypergeometric analytic continuation, our strategy is applicable to a wide class of systems.

Synthetic Minor NSR Permit: Van Hook Crude Terminal, LLC - Van Hook Crude Terminal/Rail Loading Facility

EPA Pesticide Factsheets

This page contains the current effective synthetic minor NSR permit for the Van Hook Crude Terminal, LLC, Van Hook Crude Terminal/Rail Loading Facility, located on the Fort Berthold Indian Reservation in Mountrail County, ND.

Microstructural Indicators Of Convection In Sills And Dykes

NASA Astrophysics Data System (ADS)

Holness, M. B.; Neufeld, J. A.; Gilbert, A. J.; Macdonald, R.

2016-12-01

The question of whether or not convection occurs in crustal magma chambers is a vexed one, with some advocating vigorous convection while others argue that convection is weak and short-lived. We argue that microstructural analysis is key to determining whether crystallization took place in solidification fronts or whether crystals grew suspended in a convecting magma before settling. The 168m, composite, Shiant Isles Main Sill is dominated by a 140m unit, of which the lower 45m contains olivine phenocrysts. The phenocrysts first fine upwards, then coarsen upwards. The coarsening-upwards sequence contains clustered olivines. Both the extent of sintering and average cluster size increase upwards. The coarsening-upwards sequence is mirrored at the roof. The fining-upwards sequence formed by rapid settling of incoming cargo crystals, while the coarsening-upwards sequence represents post-emplacement growth and clustering of grains suspended in a convecting magma. Convection is also recorded by plagioclase grain shape. Well-facetted and compact plagioclase grains are platy in rapidly-cooled rocks and blocky in slowly-cooled rocks. Plagioclase grain shape varies smoothly across mafic sills, consistent with growth in solidification fronts. In contrast, grain shape is invariant across mafic dykes, consistent with growth as individual grains and clusters suspended in a convecting magma. Convection in sills occurs when the critical Rayleigh number is exceeded, but cooling at vertical walls always results in convective instabilities. That the Shiant Isles Main Sill records prolonged and vigorous convection, while other sills of comparable thickness record grain growth predominantly in solidification fronts, is most likely due to the composite nature of the Shiant. The 140m unit is underlain by 23m of picrite which intruded shortly before - the strongly asymmetric cooling and absence of a cold, stagnant basal thermal boundary layer make convection throughout the sill more

Extended Bose Hubbard model of interacting bosonic atoms in optical lattices: From superfluidity to density waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mazzarella, G.; Giampaolo, S. M.; Illuminati, F.

2006-01-15

For systems of interacting, ultracold spin-zero neutral bosonic atoms, harmonically trapped and subject to an optical lattice potential, we derive an Extended Bose Hubbard (EBH) model by developing a systematic expansion for the Hamiltonian of the system in powers of the lattice parameters and of a scale parameter, the lattice attenuation factor. We identify the dominant terms that need to be retained in realistic experimental conditions, up to nearest-neighbor interactions and nearest-neighbor hoppings conditioned by the on-site occupation numbers. In the mean field approximation, we determine the free energy of the system and study the phase diagram both at zeromore » and at finite temperature. At variance with the standard on site Bose Hubbard model, the zero-temperature phase diagram of the EBH model possesses a dual structure in the Mott insulating regime. Namely, for specific ranges of the lattice parameters, a density wave phase characterizes the system at integer fillings, with domains of alternating mean occupation numbers that are the atomic counterparts of the domains of staggered magnetizations in an antiferromagnetic phase. We show as well that in the EBH model, a zero-temperature quantum phase transition to pair superfluidity is, in principle, possible, but completely suppressed at the lowest order in the lattice attenuation factor. Finally, we determine the possible occurrence of the different phases as a function of the experimentally controllable lattice parameters.« less

Glycopeptide Resistance vanA Operons in Paenibacillus Strains Isolated from Soil

PubMed Central

Guardabassi, Luca; Perichon, Bruno; van Heijenoort, Jean; Blanot, Didier; Courvalin, Patrice

2005-01-01

The sequence and gene organization of the van operons in vancomycin (MIC of >256 μg/ml)- and teicoplanin (MIC of ≥32 μg/ml)-resistant Paenibacillus thiaminolyticus PT-2B1 and Paenibacillus apiarius PA-B2B isolated from soil were determined. Both operons had regulatory (vanR and vanS), resistance (vanH, vanA, and vanX), and accessory (vanY, vanZ, and vanW) genes homologous to the corresponding genes in enterococcal vanA and vanB operons. The vanAPT operon in P. thiaminolyticus PT-2B1 had the same gene organization as that of vanA operons whereas vanAPA in P. apiarius PA-B2B resembled vanB operons due to the presence of vanW upstream from the vanHAX cluster but was closer to vanA operons in sequence. Reference P. apiarius strains NRRL B-4299 and NRRL B-4188 were found to harbor operons indistinguishable from vanAPA by PCR mapping, restriction fragment length polymorphism, and partial sequencing, suggesting that this operon was species specific. As in enterococci, resistance was inducible by glycopeptides and associated with the synthesis of pentadepsipeptide peptidoglycan precursors ending in d-Ala-d-Lac, as demonstrated by d,d-dipeptidase activities, high-pressure liquid chromatography, and mass spectrometry. The precursors differed from those in enterococci by the presence of diaminopimelic acid instead of lysine in the peptide chain. Altogether, the results are compatible with the notion that van operons in soil Paenibacillus strains and in enterococci have evolved from a common ancestor. PMID:16189102

Glycopeptide resistance vanA operons in Paenibacillus strains isolated from soil.

PubMed

Guardabassi, Luca; Perichon, Bruno; van Heijenoort, Jean; Blanot, Didier; Courvalin, Patrice

2005-10-01

The sequence and gene organization of the van operons in vancomycin (MIC of >256 microg/ml)- and teicoplanin (MIC of > or =32 microg/ml)-resistant Paenibacillus thiaminolyticus PT-2B1 and Paenibacillus apiarius PA-B2B isolated from soil were determined. Both operons had regulatory (vanR and vanS), resistance (vanH, vanA, and vanX), and accessory (vanY, vanZ, and vanW) genes homologous to the corresponding genes in enterococcal vanA and vanB operons. The vanA(PT) operon in P. thiaminolyticus PT-2B1 had the same gene organization as that of vanA operons whereas vanA(PA) in P. apiarius PA-B2B resembled vanB operons due to the presence of vanW upstream from the vanHAX cluster but was closer to vanA operons in sequence. Reference P. apiarius strains NRRL B-4299 and NRRL B-4188 were found to harbor operons indistinguishable from vanA(PA) by PCR mapping, restriction fragment length polymorphism, and partial sequencing, suggesting that this operon was species specific. As in enterococci, resistance was inducible by glycopeptides and associated with the synthesis of pentadepsipeptide peptidoglycan precursors ending in D-Ala-D-Lac, as demonstrated by D,D-dipeptidase activities, high-pressure liquid chromatography, and mass spectrometry. The precursors differed from those in enterococci by the presence of diaminopimelic acid instead of lysine in the peptide chain. Altogether, the results are compatible with the notion that van operons in soil Paenibacillus strains and in enterococci have evolved from a common ancestor.

Physical, chemical, and isotopic data from groundwater in the watershed of Mirror Lake, and in the vicinity of Hubbard Brook, near West Thornton, New Hampshire, 1983 to 1997

USGS Publications Warehouse

LaBaugh, James W.; Harte, Philip T.; Shapiro, Allen M.; Hsieh, Paul A.; Johnson, Carole D.; Goode, Daniel J.; Wood, Warren W.; Buso, Donald C.; Likens, Gene E.; Winter, Thomas C.

2013-01-01

Research on the hydrogeologic setting of Mirror Lake near West Thornton, New Hampshire (43° 56.5’ N, 71° 41.5’ W), includes the study of the physical, chemical, and isotopic characteristics of groundwater in the vicinity of the lake and nearby Hubbard Brook. Presented here are those physical, chemical, and isotopic data for the period 1983 to 1997. Data were collected from observation wells installed in glacial drift and bedrock, as well as from one domestic well in the general area of the lake and Hubbard Brook. Also presented are data for Mirror Lake for August 1, 1993, to place groundwater data in context with chemical and isotopic characteristics of the lake.

Jao Van De Lagemaat | NREL

Science.gov Websites

Jao Van De Lagemaat Photo of Jao Vandelagemaat. Jao Van De Lagemaat Center Director: Chemistry and Lagemaat is currently the Center Director of the Chemistry and Nanoscience Center at NREL. He received his university. Education Ph.D. Physical Chemistry, University of Utrecht Featured Publications View all NREL

Orbital currents in a generalized Hubbard ladder

NASA Astrophysics Data System (ADS)

Fjaerestad, John O.

2004-03-01

We study a phase with orbital currents (d-density wave (DDW)/staggered flux phase) in a generalized Hubbard model on the two-leg ladder at zero temperature. Bosonization and perturbative renormalization-group calculations are used to identify a parameter region with long-range DDW order in the weakly interacting half-filled ladder. Finite-size density-matrix renormalization-group (DMRG) studies of ladders with up to 200 rungs, for rational hole dopings δ and intermediate-strength interactions, find that currents remain large in the doped DDW phase, with no evidence of decay.^1,2,3 Motivated by these results, we consider an effective bosonization description of the doped DDW phase in which quantum fluctuations in the total charge mode are neglected.^3 This leads to an analytically solvable Frenkel-Kontorova-like model which predicts that the staggered rung current and the rung electron density show periodic spatial oscillations with wavelengths 2/δ and 1/δ, respectively, with the density minima located at the zeros (domain walls) of the staggered rung current, in good agreement with the DMRG results. We comment on the question of the nature of the asymptotic current correlations in the doped DDW phase. ^1U. Schollwöck, S. Chakravarty, J. O. Fjaerestad, J. B. Marston, and M. Troyer, Phys. Rev. Lett. 90, 186401 (2003). ^2M. Troyer, invited talk at this meeting. ^3J. O. Fjaerestad, J. B. Marston, and U. Schollwöck, unpublished.

Summary of Research 2002

DTIC Science & Technology

2005-01-01

dissipation, nonuniformity , and nonlinearity are included. A possible future objective is to theoretically investigate nonradiating sources in two and...dissipation, nonuniformity , and nonlinearity. The presence of any of these effects causes radiation to “leak” from the driven region. This radiation was...The utility of LWIR spectral imagery for plume detection was studied. PRESENTATION: Olsen, R.C., Ganer, J. and Van Dyke, E., “Terrain

Application of Long Distance Conveyance (LDC) of Dredged Sediments to Louisiana Coastal Restoration

DTIC Science & Technology

2011-01-01

U.S. Army Engineer District, New Orleans, Laura Beldon, Louisiana Office of Coastal Protection and Restoration, Cheryl Brodnax, National...Louisiana Department of Natural Resources, Christopher Knotts , Louisiana Department of Natural Resources, Fay Lachney, MVN, Luke LeBas, Louisiana...associated with the petrochemical industry (e.g., Van Dyke et al. 1994) or backfilled canals dredged as part of the pipeline installation (e.g., Knott et al

Impact of nearest-neighbor repulsion on superconducting pairing in 2D extended Hubbard model

NASA Astrophysics Data System (ADS)

Jiang, Mi; Hahner, U. R.; Maier, T. A.; Schulthess, T. C.

Using dynamical cluster approximation (DCA) with an continuous-time QMC solver for the two-dimensional extended Hubbard model, we studied the impact of nearest-neighbor Coulomb repulsion V on d-wave superconducting pairing dynamics. By solving Bethe-Salpeter equation for particle-particle superconducting channel, we focused on the evolution of leading d-wave eigenvalue with V and the momentum and frequency dependence of the corresponding eigenfunction. The comparison with the evolution of both spin and charge susceptibilities versus V is presented showing the competition between spin and charge fluctuations. This research received generous support from the MARVEL NCCR and used resources of the Swiss National Supercomputing Center, as well as (INCITE) program in Oak Ridge Leadership Computing Facility.

Can disorder act as a chemical pressure? An optical study of the Hubbard model

NASA Astrophysics Data System (ADS)

Barman, H.; Laad, M. S.; Hassan, S. R.

2018-05-01

The optical properties have been studied using the dynamical mean-field theory on a disordered Hubbard model. Despite the fact that disorder turns a metal to an insulator in high dimensional correlated materials, we notice that it can enhance certain metallic behavior as if a chemical pressure is applied to the system resulting in an increase of the effective lattice bandwidth (BW). We study optical properties in such a scenario and compare results with experiments where the BW is changed through isovalent chemical substitution (keeping electron filling unaltered) and obtain remarkable similarities vindicating our claim. We also make the point that these similarities differ from some other forms of BW tuned optical effects.

Approximation auto-coherente a deux particules, pseudogap et supraconductivite dans le modele de Hubbard attractif

NASA Astrophysics Data System (ADS)

Allen, Steve

2000-10-01

Dans cette these nous presentons une nouvelle methode non perturbative pour le calcul des proprietes d'un systeme de fermions. Notre methode generalise l'approximation auto-coherente a deux particules proposee par Vilk et Tremblay pour le modele de Hubbard repulsif. Notre methode peut s'appliquer a l'etude du comportement pre-critique lorsque la symetrie du parametre d'ordre est suffisamment elevee. Nous appliquons la methode au probleme du pseudogap dans le modele de Hubbard attractif. Nos resultats montrent un excellent accord avec les donnees Monte Carlo pour de petits systemes. Nous observons que le regime ou apparait le pseudogap dans le poids spectral a une particule est un regime classique renormalise caracterise par une frequence caracteristique des fluctuations supraconductrices inferieure a la temperature. Une autre caracteristique est la faible densite de superfluide de cette phase demontrant que nous ne sommes pas en presence de paires preformees. Les resultats obtenus semblent montrer que la haute symetrie du parametre d'ordre et la bidimensionalite du systeme etudie elargissent le domaine de temperature pour lequel le regime pseudogap est observe. Nous argumentons que ce resultat est transposable aux supraconducteurs a haute temperature critique ou le pseudogap apparait a des' temperatures beaucoup plus grandes que la temperature critique. La forte symetrie dans ces systemes pourraient etre reliee a la theorie SO(5) de Zhang. En annexe, nous demontrons un resultat tout recent qui permettrait d'assurer l'auto-coherence entre les proprietes a une et a deux particules par l'ajout d'une dynamique au vertex irreductible. Cet ajout laisse entrevoir la possibilite d'etendre la methode au cas d'une forte interaction.

Enhancement of superexchange pairing in the periodically driven Hubbard model

NASA Astrophysics Data System (ADS)

Coulthard, J. R.; Clark, S. R.; Al-Assam, S.; Cavalleri, A.; Jaksch, D.

2017-08-01

Recent experiments performed on cuprates and alkali-doped fullerides have demonstrated that key signatures of superconductivity can be induced above the equilibrium critical temperature by optical modulation. These observations in disparate physical systems may indicate a general underlying mechanism. Multiple theories have been proposed, but these either consider specific features, such as competing instabilities, or focus on conventional BCS-type superconductivity. Here we show that periodic driving can enhance electron pairing in strongly correlated systems. Focusing on the strongly repulsive limit of the doped Hubbard model, we investigate in-gap, spatially inhomogeneous, on-site modulations. We demonstrate that such modulations substantially reduce electronic hopping, while simultaneously sustaining superexchange interactions and pair hopping via driving-induced virtual charge excitations. We calculate real-time dynamics for the one-dimensional case, starting from zero- and finite-temperature initial states, and we show that enhanced singlet-pair correlations emerge quickly and robustly in the out-of-equilibrium many-body state. Our results reveal a fundamental pairing mechanism that might underpin optically induced superconductivity in some strongly correlated quantum materials.

Platinum-group element concentrations in pyrite from the Main Sulfide Zone of the Great Dyke of Zimbabwe

NASA Astrophysics Data System (ADS)

Piña, R.; Gervilla, F.; Barnes, S.-J.; Oberthür, T.; Lunar, R.

2016-10-01

The Main Sulfide Zone (MSZ) of the Great Dyke of Zimbabwe hosts the world's second largest resource of platinum-group elements (PGE) after the Bushveld Complex in South Africa. The sulfide assemblage of the MSZ comprises pyrrhotite, pentlandite, chalcopyrite, and minor pyrite. Recently, several studies have observed in a number of Ni-Cu-PGE ore deposits that pyrite may host significant amounts of PGE, particularly Pt and Rh. In this study, we have determined PGE and other trace element contents in pyrite from the Hartley, Ngezi, Unki, and Mimosa mines of the Great Dyke by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Based on the textures and PGE contents, two types of pyrite can be differentiated. Py1 occurs as individual euhedral or subhedral grains or clusters of crystals mostly within chalcopyrite and pentlandite, in some cases in the form of symplectitic intergrowths, and is PGE rich (up to 99 ppm Pt and 61 ppm Rh; 1.7 to 47.1 ppm Ru, 0.1 to 7.8 ppm Os, and 1.2 to 20.2 ppm Ir). Py2 occurs as small individual euhedral or subhedral crystals within pyrrhotite, pentlandite, and less frequently within chalcopyrite and silicates and has low PGE contents (<0.11 ppm Pt, <0.34 ppm Rh, <2.5 ppm Ru, <0.37 ppm Ir, and <0.40 ppm Os). Py1 contains higher Os, Ir, Ru, Rh, and Pt contents than the associated pyrrhotite, pentlandite, and chalcopyrite, whereas Py2 has similar PGE contents as coexisting pyrrhotite and pentlandite. Based on the textural relationships, two different origins are attributed for each pyrite type. Py1 intergrowth with pentlandite and chalcopyrite is inferred to have formed by late, low temperature (<300 °C) decomposition of residual Ni-rich monosulfide solid solution, whereas Py2 is suggested to have formed by replacement of pyrrhotite and pentlandite caused by late magmatic/hydrothermal fluids.

Entropy perspective on the thermal crossover in a fermionic Hubbard chain

NASA Astrophysics Data System (ADS)

Bonnes, Lars; Pichler, Hannes; Läuchli, Andreas M.

2013-10-01

We study the Renyi entropy in the finite-temperature crossover regime of a Hubbard chain using quantum Monte Carlo. The ground-state entropy has characteristic features such as a logarithmic divergence with block size and 2kF oscillations that are a hallmark of its Luttinger liquid nature. The interplay between the (extensive) thermal entropy and the ground-state features is studied and we analyze the temperature-induced decay of the amplitude of the oscillations as well as the scaling of the purity. Furthermore, we show how the spin and charge velocities can be extracted from the temperature dependence of the Renyi entropy, bridging our findings to recent experimental proposals on how to implement the measurement of Renyi entropies in the cold atom system. Studying the Renyi mutual information, we also demonstrate how constraints such as particle number conservation can induce persistent correlations visible in the mutual information even at high temperature.

Ferromagnetism in the Hubbard Model with a Gapless Nearly-Flat Band

NASA Astrophysics Data System (ADS)

Tanaka, Akinori

2018-01-01

We present a version of the Hubbard model with a gapless nearly-flat lowest band which exhibits ferromagnetism in two or more dimensions. The model is defined on a lattice obtained by placing a site on each edge of the hypercubic lattice, and electron hopping is assumed to be only between nearest and next nearest neighbor sites. The lattice, where all the sites are identical, is simple, and the corresponding single-electron band structure, where two cosine-type bands touch without an energy gap, is also simple. We prove that the ground state of the model is unique and ferromagnetic at half-filling of the lower band, if the lower band is nearly flat and the strength of on-site repulsion is larger than a certain value which is independent of the lattice size. This is the first example of ferromagnetism in three dimensional non-singular models with a gapless band structure.

Characterizing the three-orbital Hubbard model with determinant quantum Monte Carlo

NASA Astrophysics Data System (ADS)

Kung, Y. F.; Chen, C.-C.; Wang, Yao; Huang, E. W.; Nowadnick, E. A.; Moritz, B.; Scalettar, R. T.; Johnston, S.; Devereaux, T. P.

2016-04-01

We characterize the three-orbital Hubbard model using state-of-the-art determinant quantum Monte Carlo (DQMC) simulations with parameters relevant to the cuprate high-temperature superconductors. The simulations find that doped holes preferentially reside on oxygen orbitals and that the (π ,π ) antiferromagnetic ordering vector dominates in the vicinity of the undoped system, as known from experiments. The orbitally-resolved spectral functions agree well with photoemission spectroscopy studies and enable identification of orbital content in the bands. A comparison of DQMC results with exact diagonalization and cluster perturbation theory studies elucidates how these different numerical techniques complement one another to produce a more complete understanding of the model and the cuprates. Interestingly, our DQMC simulations predict a charge-transfer gap that is significantly smaller than the direct (optical) gap measured in experiment. Most likely, it corresponds to the indirect gap that has recently been suggested to be on the order of 0.8 eV, and demonstrates the subtlety in identifying charge gaps.

Soil bacterial communities of a calcium-supplemented and a reference watershed at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA

Treesearch

Ganapathi Sridevi; Rakesh Minocha; Swathi A. Turlapati; Katherine C. Goldfarb; Eoin L. Brodie; Louis S. Tisa; Subhash C. Minocha

2012-01-01

Soil Ca depletion because of acidic deposition-related soil chemistry changes has led to the decline of forest productivity and carbon sequestration in the northeastern USA. In 1999, acidic watershed (WS) 1 at the Hubbard Brook Experimental Forest (HBEF), NH, USA was amended with Ca silicate to restore soil Ca pools. In 2006, soil samples were collected from the Ca-...

Spin-selective electronic reconstruction in quantum ferromagnets: A view from the spin-asymmetric Hubbard model

NASA Astrophysics Data System (ADS)

Faúndez, J.; Jorge, T. N.; Craco, L.

2018-03-01

Using the tight-binding treatment for the spin-asymmetric Hubbard model we explore the effect of electronic interactions in the ferromagnetic, partially filled Lieb lattice. As a key result we demonstrate the formation of correlation satellites in the minority spin channel. In addition, we consider the role played by transverse-field spin fluctuations in metallic ferromagnets. We quantify the degree of electronic demagnetization, showing that the half-metallic state is rather robust to local spin flips. Not being restricted to the case of a partially filled Lieb lattice, our findings are expected to advance the general understanding of spin-selective electronic reconstruction in strongly correlated quantum ferromagnets.

Mott transition in the π -flux S U (4 ) Hubbard model on a square lattice

NASA Astrophysics Data System (ADS)

Zhou, Zhichao; Wu, Congjun; Wang, Yu

2018-05-01

With increasing repulsive interaction, we show that a Mott transition occurs from the semimetal to the valence bond solid, accompanied by the Z4 discrete symmetry breaking. Our simulations demonstrate the existence of a second-order phase transition, which confirms the Ginzburg-Landau analysis. The phase transition point and the critical exponent η are also estimated. To account for the effect of a π flux on the ordering in the strong-coupling regime, we analytically derive by the perturbation theory the ring-exchange term, which is the leading-order term that can reflect the difference between the π -flux and zero-flux S U (4 ) Hubbard models.

Obituary: James Alfred Van Allen, 1914-2006

NASA Astrophysics Data System (ADS)

Ludwig, George H.; McIlwain, Carl Edwin

2006-12-01

James Alfred Van Allen, world-renowned space scientist, died 9 August 2006 at the age of ninety-one. He succumbed to heart failure after a ten-week period of declining health. Van Allen served for his entire sixty-seven-year professional career as an amazingly productive researcher, space science spokesman, inspired teacher, and valued colleague. The realization by him and his associates that charged particles are trapped by the Earth's magnetic field began a whole new field of research, magnetospheric physics. Following that initial discovery, he and his associates quickly extended their observations, first to the inner planets, and then to the rest of the planets and beyond. During his tenure at Iowa, he and his group flew instruments on more than sixty successful Earth satellites and planetary spacecraft, including the first missions to the planets Venus, Mars, Jupiter, Saturn, Uranus, and Neptune. Van Allen's lifetime publication list numbers more than 275, of which many are widely-cited, seminal papers. He was the sole author of more than 125 of those papers. Beyond the research laboratory, Van Allen worked energetically throughout his career in establishing space research as a new branch of human inquiry. He was among the most sought-after as a committee member and adviser, working at the highest levels of government, including the White House and Congress, and at all levels of the national and international research establishments. Many presentations in the non-scientific arena helped to bring the exciting discoveries and challenges of space research to the attention of the general public. James Van Allen (Van to his many friends and colleagues) was born on 7 September 1914 on a small farm near Mount Pleasant, Iowa, the second of four sons of Alfred Morris Van Allen and Alma Olney Van Allen. After high school in Mount Pleasant, he entered Iowa Wesleyan College, majoring in physics and graduating summa cum laude. While there, he was introduced to geophysics

Phase diagram of the disordered Bose-Hubbard model

NASA Astrophysics Data System (ADS)

Gurarie, V.; Pollet, L.; Prokof'Ev, N. V.; Svistunov, B. V.; Troyer, M.

2009-12-01

We establish the phase diagram of the disordered three-dimensional Bose-Hubbard model at unity filling which has been controversial for many years. The theorem of inclusions, proven by Pollet [Phys. Rev. Lett. 103, 140402 (2009)] states that the Bose-glass phase always intervenes between the Mott insulating and superfluid phases. Here, we note that assumptions on which the theorem is based exclude phase transitions between gapped (Mott insulator) and gapless phases (Bose glass). The apparent paradox is resolved through a unique mechanism: such transitions have to be of the Griffiths type when the vanishing of the gap at the critical point is due to a zero concentration of rare regions where extreme fluctuations of disorder mimic a regular gapless system. An exactly solvable random transverse field Ising model in one dimension is used to illustrate the point. A highly nontrivial overall shape of the phase diagram is revealed with the worm algorithm. The phase diagram features a long superfluid finger at strong disorder and on-site interaction. Moreover, bosonic superfluidity is extremely robust against disorder in a broad range of interaction parameters; it persists in random potentials nearly 50 (!) times larger than the particle half-bandwidth. Finally, we comment on the feasibility of obtaining this phase diagram in cold-atom experiments, which work with trapped systems at finite temperature.

Consequences of the Introduction of Insensitive Munitions on Safety, Collateral Damage and Operations (consequenties van de invoering van mkm-munitie op veiligheid, gevolgschade en (internationaal) opereren

DTIC Science & Technology

2006-06-01

van de werkzaamheden In dit rapport worden de gevolgen van initiatie van munitie door een ongewilde externe stimulus beschouwd aan de hand van reele...operationele scenario’s. Dit wordt vergeleken met de gevolgen in dezelfde scenario’s, waarin gebruik is gemaakt van Minder Kwetsbare Munitie (MKM). Naast...de historie van MKM wordt uitgelegd wat Inleiding of terroristische activiteiten, maar ook door MKM is. Vervolgens worden de gevolgen Munitie en de

Textural, mineralogical and stable isotope studies of hydrothermal alteration in the main sulfide zone of the Great Dyke, Zimbabwe and the precious metals zone of the Sonju Lake Intrusion, Minnesota, USA

USGS Publications Warehouse

Li, C.; Ripley, E.M.; Oberthur, T.; Miller, J.D.; Joslin, G.D.

2008-01-01

Stratigraphic offsets in the peak concentrations of platinum-group elements (PGE) and base-metal sulfides in the main sulfide zone of the Great Dyke and the precious metals zone of the Sonju Lake Intrusion have, in part, been attributed to the interaction between magmatic PGE-bearing base-metal sulfide assemblages and hydrothermal fluids. In this paper, we provide mineralogical and textural evidence that indicates alteration of base-metal sulfides and mobilization of metals and S during hydrothermal alteration in both mineralized intrusions. Stable isotopic data suggest that the fluids involved in the alteration were of magmatic origin in the Great Dyke but that a meteoric water component was involved in the alteration of the Sonju Lake Intrusion. The strong spatial association of platinum-group minerals, principally Pt and Pd sulfides, arsenides, and tellurides, with base-metal sulfide assemblages in the main sulfide zone of the Great Dyke is consistent with residual enrichment of Pt and Pd during hydrothermal alteration. However, such an interpretation is more tenuous for the precious metals zone of the Sonju Lake Intrusion where important Pt and Pd arsenides and antimonides occur as inclusions within individual plagioclase crystals and within alteration assemblages that are free of base-metal sulfides. Our observations suggest that Pt and Pd tellurides, antimonides, and arsenides may form during both magmatic crystallization and subsolidus hydrothermal alteration. Experimental studies of magmatic crystallization and hydrothermal transport/deposition in systems involving arsenides, tellurides, antimonides, and base metal sulfides are needed to better understand the relative importance of magmatic and hydrothermal processes in controlling the distribution of PGE in mineralized layered intrusions of this type. ?? Springer-Verlag 2007.

Sediment dynamics over multiple time scales in Dyke Marsh Preserve (Potomac River, VA)

NASA Astrophysics Data System (ADS)

Palinkas, C. M.; Walters, D.

2010-12-01

Tidal freshwater marshes are critical components of fluvial and estuarine ecosystems, yet sediment dynamics within them have not received as much attention as their saltwater counterparts. This study examines sedimentation in Dyke Marsh Preserve, located on the Potomac River (VA), focusing on understanding the spatial variability present over multiple time scales. Bimonthly sediment data were collected using ceramic tiles, and seasonal- and decadal-scale sedimentation was determined via 7Be (half-life 53.3 days) and 210Pb (half-life 22.3 years), respectively. Results were also compared to SET data collected by the National Park Service since 2006. Preliminary data indicate that sites at lower elevations have higher sedimentation rates, likely related to their close proximity to the sediment source. Mass accumulation rates generally decreased with increasing time scale, such that the seasonal rates were greater than the SET-derived accretion rates, which were in turn greater than the decadal-scale rates. However, the bimonthly rates were the lowest observed, probably because the sampling period (May-October 2010) did not include the main depositional period of the year, which would be integrated by the other techniques.

Le magmatisme basique filonien néoprotérozoïque de la boutonnière de Zenaga, Anti-Atlas central, Maroc: pétrologie, géochimie et signification géodynamiqueNeoproterozoic basic dykes of the Zenaga Inlier, central Anti-Atlas, Morocco: petrology, geochemistry and geodynamic significance

NASA Astrophysics Data System (ADS)

Hafid, A.; Sagon, J. P.; Julivert, M.; Arboleya, M. L.; Saquaque, A.; El-Boukhari, A.; Saidi, A.; Soler, J. M. F.

2001-05-01

Before the Pan-African Orogeny, the Palæoproterozoic basement and its Neoproterozoic cover (limestones and quartzites) of the Zenaga Inlier were cross-cut by a swarm of doleritic dykes. They are more or less altered. The primary mineral assemblage consists of plagioclase, clinopyroxene, very rare orthopyroxene, ilmenite, apatite, micropegmatite and sometimes hornblende and biotite. Mineralogical and geochemical studies indicate that the dolerites are continental tholeiites. Two groups of dykes have been distinguished. Accordingly, rare earth elements, P 2O 5, Zr, Th, Ba and Sr contents are higher in group I than in group II, which is richer in V. Group I comprises the north-south and northwest-southeast swarms, while group II corresponds to northeast-southwest and east-west swarms, which were emplaced later. These geochemical variations may be explained by a higher degree of melting of the mantle source for the later group II. Doleritic dykes of Zenaga had been emplaced during an extensional episode, prior to Pan-African folding.

Estimated Flood-Inundation Mapping for the Upper Blue River, Indian Creek, and Dyke Branch in Kansas City, Missouri, 2006-08

USGS Publications Warehouse

Kelly, Brian P.; Huizinga, Richard J.

2008-01-01

In the interest of improved public safety during flooding, the U.S. Geological Survey, in cooperation with the city of Kansas City, Missouri, completed a flood-inundation study of the Blue River in Kansas City, Missouri, from the U.S. Geological Survey streamflow gage at Kenneth Road to 63rd Street, of Indian Creek from the Kansas-Missouri border to its mouth, and of Dyke Branch from the Kansas-Missouri border to its mouth, to determine the estimated extent of flood inundation at selected flood stages on the Blue River, Indian Creek, and Dyke Branch. The results of this study spatially interpolate information provided by U.S. Geological Survey gages, Kansas City Automated Local Evaluation in Real Time gages, and the National Weather Service flood-peak prediction service that comprise the Blue River flood-alert system and are a valuable tool for public officials and residents to minimize flood deaths and damage in Kansas City. To provide public access to the information presented in this report, a World Wide Web site (http://mo.water.usgs.gov/indep/kelly/blueriver) was created that displays the results of two-dimensional modeling between Hickman Mills Drive and 63rd Street, estimated flood-inundation maps for 13 flood stages, the latest gage heights, and National Weather Service stage forecasts for each forecast location within the study area. The results of a previous study of flood inundation on the Blue River from 63rd Street to the mouth also are available. In addition the full text of this report, all tables and maps are available for download (http://pubs.usgs.gov/sir/2008/5068). Thirteen flood-inundation maps were produced at 2-foot intervals for water-surface elevations from 763.8 to 787.8 feet referenced to the Blue River at the 63rd Street Automated Local Evaluation in Real Time stream gage operated by the city of Kansas City, Missouri. Each map is associated with gages at Kenneth Road, Blue Ridge Boulevard, Kansas City (at Bannister Road), U.S. Highway 71

The Hubbard Dimer: A Complete DFT Solution to a Many-Body Problem

NASA Astrophysics Data System (ADS)

Smith, Justin; Carrascal, Diego; Ferrer, Jaime; Burke, Kieron

2015-03-01

In this work we explain the relationship between density functional theory and strongly correlated models using the simplest possible example, the two-site asymmetric Hubbard model. We discuss the connection between the lattice and real-space and how this is a simple model for stretched H2. We can solve this elementary example analytically, and with that we can illuminate the underlying logic and aims of DFT. While the many-body solution is analytic, the density functional is given only implicitly. We overcome this difficulty by creating a highly accurate parameterization of the exact function. We use this parameterization to perform benchmark calculations of correlation kinetic energy, the adiabatic connection, etc. We also test Hartree-Fock and the Bethe Ansatz Local Density Approximation. We also discuss and illustrate the derivative discontinuity in the exchange-correlation energy and the infamous gap problem in DFT. DGE-1321846, DE-FG02-08ER46496.

Chlorhexidine Induces VanA-Type Vancomycin Resistance Genes in Enterococci

PubMed Central

Bhardwaj, Pooja; Ziegler, Elizabeth

2016-01-01

Chlorhexidine is a bisbiguanide antiseptic used for infection control. Vancomycin-resistant E. faecium (VREfm) is among the leading causes of hospital-acquired infections. VREfm may be exposed to chlorhexidine at supra- and subinhibitory concentrations as a result of chlorhexidine bathing and chlorhexidine-impregnated central venous catheter use. We used RNA sequencing to investigate how VREfm responds to chlorhexidine gluconate exposure. Among the 35 genes upregulated ≥10-fold after 15 min of exposure to the MIC of chlorhexidine gluconate were those encoding VanA-type vancomycin resistance (vanHAX) and those associated with reduced daptomycin susceptibility (liaXYZ). We confirmed that vanA upregulation was not strain or species specific by querying other VanA-type VRE. VanB-type genes were not induced. The vanH promoter was found to be responsive to subinhibitory chlorhexidine gluconate in VREfm, as was production of the VanX protein. Using vanH reporter experiments with Bacillus subtilis and deletion analysis in VREfm, we found that this phenomenon is VanR dependent. Deletion of vanR did not result in increased chlorhexidine susceptibility, demonstrating that vanHAX induction is not protective against chlorhexidine. As expected, VanA-type VRE is more susceptible to ceftriaxone in the presence of sub-MIC chlorhexidine. Unexpectedly, VREfm is also more susceptible to vancomycin in the presence of subinhibitory chlorhexidine, suggesting that chlorhexidine-induced gene expression changes lead to additional alterations in cell wall synthesis. We conclude that chlorhexidine induces expression of VanA-type vancomycin resistance genes and genes associated with daptomycin nonsusceptibility. Overall, our results indicate that the impacts of subinhibitory chlorhexidine exposure on hospital-associated pathogens should be further investigated in laboratory studies. PMID:26810654

Emergence of vanA Enterococcus faecium in Denmark, 2005-15.

PubMed

Hammerum, Anette M; Baig, Sharmin; Kamel, Yasmin; Roer, Louise; Pinholt, Mette; Gumpert, Heidi; Holzknecht, Barbara; Røder, Bent; Justesen, Ulrik S; Samulioniené, Jurgita; Kjærsgaard, Mona; Østergaard, Claus; Holm, Anette; Dzajic, Esad; Søndergaard, Turid Snekloth; Gaini, Shahin; Edquist, Petra; Alm, Erik; Lilje, Berit; Westh, Henrik; Stegger, Marc; Hasman, Henrik

2017-08-01

To describe the changing epidemiology of vancomycin-resistant Enterococcus faecium and Enterococcus faecalis in clinical samples in Denmark 2005-15 according to species and van type, and, furthermore, to investigate the genetic relatedness of the clinical E. faecium isolates from 2015. During 2005-14, all clinical VRE isolates were tested for the presence of vanA/B/C genes by PCR. In 2015, all clinical VRE isolates were whole-genome sequenced. From the WGS data, the presence of van genes and MLST STs were extracted in silico . Core-genome MLST (cgMLST) analysis was performed for the vancomycin-resistant E. faecium isolates. During 2005-15, 1043 vanA E. faecium , 25 vanB E. faecium , 4 vanA E. faecalis and 28 vanB E. faecalis were detected. The number of VRE was <50 isolates/year until 2012 to > 200 isolates/year in 2013-15. In 2015, 368 vanA E. faecium and 1 vanB E. faecium were detected along with 1 vanA E. faecalis and 1 vanB E. faecalis . cgMLST subdivided the 368 vanA E. faecium isolates into 33 cluster types (CTs), whereas the vanB E. faecium isolate belonged to a different CT. ST203-CT859 was most prevalent (51%), followed by ST80-CT14 (22%), ST117-CT24 (6%), ST80-CT866 (4%) and ST80-CT860 (2%). Comparison with the cgMLST.org database, previous studies and personal communications with neighbouring countries revealed that the novel cluster ST203-CT859 emerged in December 2014 and spread to the south of Sweden and the Faroe Islands during 2015. VRE increased in Denmark during 2005-15 due to the emergence of several vanA E. faecium clones. © The Author 2017. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

A Conversation with William Van Til.

ERIC Educational Resources Information Center

Beineke, John A.

1989-01-01

Reports an interview with William Van Til, Coffman Distinguished Professor Emeritus of Education at Indiana State University (Terre Haute). Van Til reviews his career as a social studies teacher and his writings on curriculum and social foundations. Presents his opinions on progressive education, famous educators, educational history and reform,…

Additional Value from Road Mapping in Defense Policy Making (meerwaarde van roadmapping bij beleidsontwikkeling van de koninklijke landmacht)

DTIC Science & Technology

2006-05-01

van zogonaamde strategische reserves tot bijvaarbeeld lakaal boschikbare gevechtscapacitoit. 9 11 Joint. Do Nederlandse krijgsmacht ontwikkelt zich tot...8 2 W erkwijze van de KL tot nu toe ............................................................................... 9 2.1 O...ntwikkeling visiedocurnent ....................................................................................... 9 2.2 Opzet beleid- en deelstudies

Long-term calcium addition increases growth release, wound closure, and health of sugar maple (Acer saccharum) trees at the Hubbard Brook Experimental Forest

Treesearch

Brett A. Huggett; Paul G. Schaberg; Gary J. Hawley; Christopher Eager

2007-01-01

We surveyed and wounded forest-grown sugar maple (Acer saccharum Marsh.) trees in a long-term, replicated Ca manipulation study at the Hubbard Brook Experimental Forest in New Hampshire, USA. Plots received applications of Ca (to boost Ca availability above depleted ambient levels) or A1 (to compete with Ca uptake and further reduce Ca availability...

Spinons and holons for the one-dimensional three-band Hubbard models of high-temperature superconductors.

PubMed Central

Tahir-Kheli, J; Goddard, W A

1993-01-01

The one-dimensional three-band Hubbard Hamiltonian is shown to be equivalent to an effective Hamiltonian that has independent spinon and holon quasiparticle excitations plus a weak coupling of the two. The spinon description includes both copper sites and oxygen hole sites leading to a one-dimensional antiferromagnet incommensurate with the copper lattice. The holons are spinless noninteracting fermions in a simple cosine band. Because the oxygen sites are in the Hamiltonian, the quasiparticles are much simpler than in the exact solution of the t-J model for 2t = +/- J. If a similar description is correct for two dimensions, then the holons will attract in a p-wave potential. PMID:11607436

Transient aerodynamic characteristics of vans during the accelerated overtaking process

NASA Astrophysics Data System (ADS)

Liu, Li-ning; Wang, Xing-shen; Du, Guang-sheng; Liu, Zheng-gang; Lei, Li

2018-04-01

This paper studies the influence of the accelerated overtaking process on the vehicles' transient aerodynamic characteristics, through 3-D numerical simulations with dynamic meshes and sliding interface technique. Numerical accuracy is verified by experimental results. The aerodynamic characteristics of vehicles in the uniform overtaking process and the accelerated overtaking process are compared. It is shown that the speed variation of the overtaking van would influence the aerodynamic characteristics of the two vans, with greater influence on the overtaken van than on the overtaking van. The simulations of three different accelerated overtaking processes show that the greater the acceleration of the overtaking van, the larger the aerodynamic coefficients of the overtaken van. When the acceleration of the overtaking van increases by 1 m/s2, the maximum drag force, side force and yawing moment coefficients of the overtaken van all increase by more than 6%, to seriously affect the power performance and the stability of the vehicles. The analysis of the pressure fields under different accelerated conditions reveals the cause of variations of the aerodynamic characteristics of vehicles.

Excitonic Order and Superconductivity in the Two-Orbital Hubbard Model: Variational Cluster Approach

NASA Astrophysics Data System (ADS)

Fujiuchi, Ryo; Sugimoto, Koudai; Ohta, Yukinori

2018-06-01

Using the variational cluster approach based on the self-energy functional theory, we study the possible occurrence of excitonic order and superconductivity in the two-orbital Hubbard model with intra- and inter-orbital Coulomb interactions. It is known that an antiferromagnetic Mott insulator state appears in the regime of strong intra-orbital interaction, a band insulator state appears in the regime of strong inter-orbital interaction, and an excitonic insulator state appears between them. In addition to these states, we find that the s±-wave superconducting state appears in the small-correlation regime, and the dx2 - y2-wave superconducting state appears on the boundary of the antiferromagnetic Mott insulator state. We calculate the single-particle spectral function of the model and compare the band gap formation due to the superconducting and excitonic orders.

Energy Spectrum and Optical Absorption of Isomer No. 11 of C84 Fullerene of C 2 Symmetry Within the Hubbard Model

NASA Astrophysics Data System (ADS)

Murzashev, A. I.; Rumyantsev, I. A.

2018-05-01

Energy spectrum of isomer No. 11 of C84 fullerene of C2 symmetry is calculated within the Hubbard model. Based on the obtained energy spectrum, the optical absorption spectrum is modeled taking into account not only allowed, but also forbidden symmetry transitions. Good qualitative agreement with the experimental data is obtained. This suggests that when studying fullerenes, the intra-site Coulomb interaction of electrons must be taken into account.

Quantum noise in a transversely-pumped-cavity Bose-Hubbard model

NASA Astrophysics Data System (ADS)

Nagy, Dávid; Kónya, Gábor; Domokos, Peter; Szirmai, Gergely

2018-06-01

We investigate the quantum measurement noise effects on the dynamics of an atomic Bose lattice gas inside an optical resonator. We describe the dynamics by means of a hybrid model consisting of a Bose-Hubbard Hamiltonian for the atoms and a Heisenberg-Langevin equation for the lossy cavity-field mode. We assume that the atoms are prepared initially in the ground state of the lattice Hamiltonian and then start to interact with the cavity mode. We show that the cavity-field fluctuations originating from the dissipative outcoupling of photons from the resonator lead to vastly different effects in the different possible ground-state phases, i.e., the superfluid, the supersolid, the Mott and charge-density-wave phases. In the former two phases with the presence of a superfluid wavefunction, the quantum measurement noise appears as a driving term leading to depletion of the ground state. The timescale for the system to leave the ground state is presented in a simple analytical form. For the latter two incompressible phases, the quantum noise results in the fluctuation of the chemical potential. We derive an analytical expression for the corresponding broadening of the quasiparticle resonances.

Ising tricriticality in the extended Hubbard model with bond dimerization

NASA Astrophysics Data System (ADS)

Fehske, Holger; Ejima, Satoshi; Lange, Florian; Essler, Fabian H. L.

We explore the quantum phase transition between Peierls and charge-density-wave insulating states in the one-dimensional, half-filled, extended Hubbard model with explicit bond dimerization. We show that the critical line of the continuous Ising transition terminates at a tricritical point, belonging to the universality class of the tricritical Ising model with central charge c=7/10. Above this point, the quantum phase transition becomes first order. Employing a numerical matrix-product-state based (infinite) density-matrix renormalization group method we determine the ground-state phase diagram, the spin and two-particle charge excitations gaps, and the entanglement properties of the model with high precision. Performing a bosonization analysis we can derive a field description of the transition region in terms of a triple sine-Gordon model. This allows us to derive field theory predictions for the power-law (exponential) decay of the density-density (spin-spin) and bond-order-wave correlation functions, which are found to be in excellent agreement with our numerical results. This work was supported by Deutsche Forschungsgemeinschaft (Germany), SFB 652, project B5, and by the EPSRC under Grant No. EP/N01930X/1 (FHLE).

Phase Fluctuations and a Negative U Hubbard Model: Single-Particle and Thermodyanic Properties in a Conserving Approximation

NASA Astrophysics Data System (ADS)

Serene, J. W.; Deisz, J. J.; Hess, D. W.

1997-03-01

Calculations performed in the fluctuation exchange approximation for the single-band 2D Hubbard model on a cylinder and threaded by a flux, show the appearance of a finite superfluid density below T ~ 0.13t, for U=-4t and at three-eighths filling.(J.J. Deisz, D.W. Hess, Bull. Am. Phys. Soc. 41, 239 (1996); J.J. Deisz, D.W. Hess, and J.W. Serene, in preparation.) We show the evolution, with decreasing temperature, of the single-particle spectral function, the self-energy, the particle-particle T-matrix, and thermodynamic properties as the superfluid state is approached and entered.

Characterizing the three-orbital Hubbard model with determinant quantum Monte Carlo

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kung, Y. F.; Chen, C. -C.; Wang, Yao

Here, we characterize the three-orbital Hubbard model using state-of-the-art determinant quantum Monte Carlo (DQMC) simulations with parameters relevant to the cuprate high-temperature superconductors. The simulations find that doped holes preferentially reside on oxygen orbitals and that the (π,π) antiferromagnetic ordering vector dominates in the vicinity of the undoped system, as known from experiments. The orbitally-resolved spectral functions agree well with photoemission spectroscopy studies and enable identification of orbital content in the bands. A comparison of DQMC results with exact diagonalization and cluster perturbation theory studies elucidates how these different numerical techniques complement one another to produce a more complete understandingmore » of the model and the cuprates. Interestingly, our DQMC simulations predict a charge-transfer gap that is significantly smaller than the direct (optical) gap measured in experiment. Most likely, it corresponds to the indirect gap that has recently been suggested to be on the order of 0.8 eV, and demonstrates the subtlety in identifying charge gaps.« less

Characterizing the three-orbital Hubbard model with determinant quantum Monte Carlo

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kung, Y. F.; Chen, C. -C.; Wang, Yao

We characterize the three-orbital Hubbard model using state-of-the-art determinant quantum Monte Carlo (DQMC) simulations with parameters relevant to the cuprate high-temperature superconductors. The simulations find that doped holes preferentially reside on oxygen orbitals and that the (π,π) antiferromagnetic ordering vector dominates in the vicinity of the undoped system, as known from experiments. The orbitally-resolved spectral functions agree well with photoemission spectroscopy studies and enable identification of orbital content in the bands. A comparison of DQMC results with exact diagonalization and cluster perturbation theory studies elucidates how these different numerical techniques complement one another to produce a more complete understanding ofmore » the model and the cuprates. Interestingly, our DQMC simulations predict a charge-transfer gap that is significantly smaller than the direct (optical) gap measured in experiment. Most likely, it corresponds to the indirect gap that has recently been suggested to be on the order of 0.8 eV, and demonstrates the subtlety in identifying charge gaps.« less

Characterizing the three-orbital Hubbard model with determinant quantum Monte Carlo

DOE PAGES

Kung, Y. F.; Chen, C. -C.; Wang, Yao; ...

2016-04-29

Here, we characterize the three-orbital Hubbard model using state-of-the-art determinant quantum Monte Carlo (DQMC) simulations with parameters relevant to the cuprate high-temperature superconductors. The simulations find that doped holes preferentially reside on oxygen orbitals and that the (π,π) antiferromagnetic ordering vector dominates in the vicinity of the undoped system, as known from experiments. The orbitally-resolved spectral functions agree well with photoemission spectroscopy studies and enable identification of orbital content in the bands. A comparison of DQMC results with exact diagonalization and cluster perturbation theory studies elucidates how these different numerical techniques complement one another to produce a more complete understandingmore » of the model and the cuprates. Interestingly, our DQMC simulations predict a charge-transfer gap that is significantly smaller than the direct (optical) gap measured in experiment. Most likely, it corresponds to the indirect gap that has recently been suggested to be on the order of 0.8 eV, and demonstrates the subtlety in identifying charge gaps.« less

Doping evolution of spin and charge excitations in the Hubbard model

DOE PAGES

Kung, Y. F.; Nowadnick, E. A.; Jia, C. J.; ...

2015-11-05

We shed light on how electronic correlations vary across the phase diagram of the cuprate superconductors, examining the doping evolution of spin and charge excitations in the single-band Hubbard model using determinant quantum Monte Carlo (DQMC). In the single-particle response, we observe that the effects of correlations weaken rapidly with doping, such that one may expect the random phase approximation (RPA) to provide an adequate description of the two-particle response. In contrast, when compared to RPA, we find that significant residual correlations in the two-particle excitations persist up to 40% hole and 15% electron doping (the range of dopings achievedmore » in the cuprates). Ultimately, these fundamental differences between the doping evolution of single- and multi-particle renormalizations show that conclusions drawn from single-particle processes cannot necessarily be applied to multi-particle excitations. Eventually, the system smoothly transitions via a momentum-dependent crossover into a weakly correlated metallic state where the spin and charge excitation spectra exhibit similar behavior and where RPA provides an adequate description.« less

Des proprietes de l'etat normal du modele de Hubbard bidimensionnel

NASA Astrophysics Data System (ADS)

Lemay, Francois

Depuis leur decouverte, les etudes experimentales ont demontre que les supra-conducteurs a haute temperature ont une phase normale tres etrange. Les proprietes de ces materiaux ne sont pas bien decrites par la theorie du liquide de Fermi. Le modele de Hubbard bidimensionnel, bien qu'il ne soit pas encore resolu, est toujours considere comme un candidat pour expliquer la physique de ces composes. Dans cet ouvrage, nous mettons en evidence plusieurs proprietes electroniques du modele qui sont incompatibles avec l'existence de quasi-particules. Nous montrons notamment que la susceptibilite des electrons libres sur reseau contient des singularites logarithmiques qui influencent de facon determinante les proprietes de la self-energie a basse frequence. Ces singularites sont responsables de la destruction des quasi-particules. En l'absence de fluctuations antiferromagnetiques, elles sont aussi responsables de l'existence d'un petit pseudogap dans le poids spectral au niveau de Fermi. Les proprietes du modele sont egalement etudiees pour une surface de Fermi similaire a celle des supraconducteurs a haute temperature. Un parallele est etabli entre certaines caracteristiques du modele et celles de ces materiaux.

The Dramatic Methods of Hans van Dam.

ERIC Educational Resources Information Center

van de Water, Manon

1994-01-01

Interprets for the American reader the untranslated dramatic methods of Hans van Dam, a leading drama theorist in the Netherlands. Discusses the functions of drama as a method, closed dramatic methods, open dramatic methods, and applying van Dam's methods. (SR)

Van der Waals interaction in uniaxial anisotropic media.

PubMed

Kornilovitch, Pavel E

2013-01-23

Van der Waals interactions between flat surfaces in uniaxial anisotropic media are investigated in the nonretarded limit. The main focus is the effect of nonzero tilt between the optical axis and the surface normal on the strength of the van der Waals attraction. General expressions for the van der Waals free energy are derived using the surface mode method and the transfer-matrix formalism. To facilitate numerical calculations a temperature-dependent three-band parameterization of the dielectric tensor of the liquid crystal 5CB is developed. A solid slab immersed in a liquid crystal experiences a van der Waals torque that aligns the surface normal relative to the optical axis of the medium. The preferred orientation is different for different materials. Two solid slabs in close proximity experience a van der Waals attraction that is strongest for homeotropic alignment of the intervening liquid crystal for all the materials studied. The results have implications for the stability of plate-like colloids in liquid crystal hosts.

Margaret Cavendish's materialist critique of van Helmontian chymistry.

PubMed

Clucas, Stephen

2011-03-01

A striking omission in the scholarship on the reception of the chymical philosophy of Jan Baptista van Helmont in England in the seventeenth century is the work of the mid-seventeenth-century natural philosopher Margaret Cavendish, Duchess of Newcastle. In her Philosophical Letters (1664), Cavendish offers an extended critique of Van Helmont's work (whose Ortus Medicince had recently been translated into English by John Sadler). In this paper, I compare Cavendish's criticisms with those of Robert Boyle in his Sceptical Chymist (1661). Both Boyle and Cavendish attacked Van Helmont for the obscurity of his chymical vocabulary and concepts, and attacked his seminalism. Although their critiques had much in common, they diverged in their attitudes to Van Helmont's experiments. As an opponent of the experimental philosophy, Cavendish had little interest in the quality of Van Helmont's experimental claims, whereas Boyle was critical of their unreplicability. I also try to show that the two writers had very different polemical agendas, with Boyle defending his vision of chymistry based on a corpuscularian natural philosophy, and Cavendish being as much concerned with establishing her religious orthodoxy as with defending the truth claims of her own materialist vitalism. For Cavendish, Van Helmont was an example of the dangers of mingling theology and natural philosophy.

Van Go: A Labor of Love

ERIC Educational Resources Information Center

Williams, Jennifer

2012-01-01

Like a tapestry woven with one outstanding thread from beginning to end, the author's forty-year tenure as an art educator has its golden thread in her Van Go art outreach project. Quite literally, she takes students in a "van" and they "go," mostly on dirt roads, taking art to rural schools in Idaho, some of which have no more…

Genetics Home Reference: van der Woude syndrome

MedlinePlus

... What is the prognosis of a genetic condition? Genetic and Rare Diseases Information Center Frequency Van der Woude syndrome is believed to occur in 1 in 35,000 to 1 in 100,000 people, based on data from Europe and Asia. Van der Woude syndrome ...

PRELIM: Predictive Relevance Estimation from Linked Models

DTIC Science & Technology

2014-10-14

code ) 14-10-2014 Final Report 11-07-2014 to 14-10-2014 PRELIM: Predictive Relevance Estimation from Linked Models N00014-14-P-1185 10257H. Van Dyke...Parunak, Ph.D. Soar Technology, Inc. 1 Executive  Summary   PRELIM (Predictive Relevance Estimation from Linked Models) draws on semantic models...The central challenge in proactive decision support is to anticipate the decision and information needs of decision-makers, in the light of likely

Advances in Enterprise Control. AEC Proceedings, November 15-16, 1999/San Diego, California

DTIC Science & Technology

1999-11-16

structure of tropical termite mounds. 2.3. Mechanisms that each agent deposits one unit of pheromone per unit time and that a proportion 0 < E < 1 of the...Stubberud 137 Section 4: Distributed and Agent-Based Strategies 149 Synthetic Pheromones for Distributed Motion Control by H. Van Dyke Parunak and...Computer Engineering, June, 1994. 147 148 Section 4 Distributed and Agent-Based Strategies 149 150 Synthetic Pheromones for Distributed Motion

STS-132 Launch Tweetup

NASA Image and Video Library

2010-05-12

Kendal Van Dyke, a database professional that is followed on Twitter @twitter.com/sqldba, takes part in the two-day STS-132 Launch Tweetup at Kennedy Space Center, Thursday, May 13, 2010, in Cape Canaveral, Fla. NASA Twitter followers in attendance will have the opportunity to take a tour of NASA's Kennedy Space Center, view the space shuttle launch and speak with shuttle technicians, engineers, astronauts and managers. Photo Credit: (NASA/Paul E. Alers)

Archaeological Investigations at the Grant River Public Use Area. Volume 1. Narrative.

DTIC Science & Technology

1984-12-01

St. Paul, Minnesota 55101-1479 Ms. Patricia Emerson Impact Services, Inc. P.O. Box 3224 Mankato, Minnesota 56001 Mr. Alan Van Dyke Berg- Zimmer and...biface was recovered. It is basally thinned with very weak shoulders . No grinding occurs on either the lateral margins or on the concave base... anatomical elements (see Appendix C). A minimum number of individuals is 16, based on the most frequently occurring element, the right mandibular first molar

UPS Hybrid Electric Delivery Van Testing | Transportation Research | NREL

Science.gov Websites

conventional diesel vans. Publications The following documents provide detailed information about the study the conventional vans during the on-road portion of the study. The two vehicle groups switched route assignments during the study period to provide a balanced review of the vans on the same routes. During

Genetics Home Reference: Ellis-van Creveld syndrome

MedlinePlus

... CREVELD SYNDROME Sources for This Page Baujat G, Le Merrer M. Ellis-van Creveld syndrome. Orphanet J Rare Dis. 2007 Jun ... CB, Kochilas L, Schimmenti LA, Moller JH. Ellis-van Creveld syndrome and congenital heart defects: presentation of an additional 32 cases. Pediatr Cardiol. 2011 Oct;32( ...

Magnetic Correlations and Pairing in the 1/5-Depleted Square Lattice Hubbard Model

DOE PAGES

Khatemi, Ehsan; Singh, Rajiv R. P.; Pickett, Warren E.; ...

2014-09-04

We study the single-orbital Hubbard model on the 1/5-depleted square-lattice geometry, which arises in such diverse systems as the spin-gap magnetic insulator CaV 4O 9 and ordered-vacancy iron selenides, presenting new issues regarding the origin of both magnetic ordering and superconductivity in these materials. We find a rich phase diagram that includes a plaquette singlet phase, a dimer singlet phase, a Néel and a block-spin antiferromagnetic phase, and stripe phases. Quantum Monte Carlo simulations show that the dominant pairing correlations at half filling change character from d wave in the plaquette phase to extended s wave upon transition to themore » Néel phase. These findings have intriguing connections to iron-based superconductors, and suggest that some physics of multiorbital systems can be captured by a single-orbital model at different dopings.« less

Adequacy of Si:P chains as Fermi-Hubbard simulators

NASA Astrophysics Data System (ADS)

Dusko, Amintor; Delgado, Alain; Saraiva, André; Koiller, Belita

2018-01-01

The challenge of simulating many-body models with analogue physical systems requires both experimental precision and very low operational temperatures. Atomically precise placement of dopants in Si permits the construction of nanowires by design. We investigate the suitability of these interacting electron systems as simulators of a fermionic extended Hubbard model on demand. We describe the single-particle wavefunctions as a linear combination of dopant orbitals (LCDO). The electronic states are calculated within configuration interaction (CI). Due to the peculiar oscillatory behavior of each basis orbital, properties of these chains are strongly affected by the interdonor distance R0, in a non-monotonic way. Ground state (T = 0 K) properties such as charge and spin correlations are shown to remain robust under temperatures up to 4 K for specific values of R0. The robustness of the model against disorder is also tested, allowing some fluctuation of the placement site around the target position. We suggest that finite donor chains in Si may serve as an analog simulator for strongly correlated model Hamiltonians. This simulator is, in many ways, complementary to those based on cold atoms in optical lattices—the trade-off between the tunability achievable in the latter and the survival of correlation at higher operation temperatures for the former suggests that both technologies are applicable for different regimes.

Superfluid drag in the two-component Bose-Hubbard model

NASA Astrophysics Data System (ADS)

Sellin, Karl; Babaev, Egor

2018-03-01

In multicomponent superfluids and superconductors, co- and counterflows of components have, in general, different properties. A. F. Andreev and E. P. Bashkin [Sov. Phys. JETP 42, 164 (1975)] discussed, in the context of He3/He4 superfluid mixtures, that interparticle interactions produce a dissipationless drag. The drag can be understood as a superflow of one component induced by phase gradients of the other component. Importantly, the drag can be both positive (entrainment) and negative (counterflow). The effect is known to have crucial importance for many properties of diverse physical systems ranging from the dynamics of neutron stars and rotational responses of Bose mixtures of ultracold atoms to magnetic responses of multicomponent superconductors. Although substantial literature exists that includes the drag interaction phenomenologically, only a few regimes are covered by quantitative studies of the microscopic origin of the drag and its dependence on microscopic parameters. Here we study the microscopic origin and strength of the drag interaction in a quantum system of two-component bosons on a lattice with short-range interaction. By performing quantum Monte Carlo simulations of a two-component Bose-Hubbard model we obtain dependencies of the drag strength on the boson-boson interactions and properties of the optical lattice. Of particular interest are the strongly correlated regimes where the ratio of coflow and counterflow superfluid stiffnesses can diverge, corresponding to the case of saturated drag.

Variational Two-Particle Density Matrix Calculation for the Hubbard Model Below Half Filling Using Spin-Adapted Lifting Conditions

NASA Astrophysics Data System (ADS)

Verstichel, Brecht; van Aggelen, Helen; Poelmans, Ward; Van Neck, Dimitri

2012-05-01

The variational determination of the two-particle density matrix is an interesting, but not yet fully explored technique that allows us to obtain ground-state properties of a quantum many-body system without reference to an N-particle wave function. The one-dimensional fermionic Hubbard model has been studied before with this method, using standard two- and three-index conditions on the density matrix [J. R. Hammond , Phys. Rev. A 73, 062505 (2006)PLRAAN1050-294710.1103/PhysRevA.73.062505], while a more recent study explored so-called subsystem constraints [N. Shenvi , Phys. Rev. Lett. 105, 213003 (2010)PRLTAO0031-900710.1103/PhysRevLett.105.213003]. These studies reported good results even with only standard two-index conditions, but have always been limited to the half-filled lattice. In this Letter, we establish the fact that the two-index approach fails for other fillings. In this case, a subset of three-index conditions is absolutely needed to describe the correct physics in the strong-repulsion limit. We show that applying lifting conditions [J. R. Hammond , Phys. Rev. APLRAAN1050-2947 71, 062503 (2005)10.1103/PhysRevA.71.062503] is the most economical way to achieve this, while still avoiding the computationally much heavier three-index conditions. A further extension to spin-adapted lifting conditions leads to increased accuracy in the intermediate repulsion regime. At the same time, we establish the feasibility of such studies to the more complicated phase diagram in two-dimensional Hubbard models.

Heath Van Essen

EPA Pesticide Factsheets

The EPA is providing notice of a proposed Administrative Penalty Assessment against Heath Van Essen, Respondent, an individual who owns or operates an animal feeding operation (“Facility”) that is located in Section 27 of Township 98 North, Range 47 West,

77 FR 14583 - Notice to Manufacturers of Alternative Fuel Vans

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-12

... Alternative Fuel Vans AGENCY: Federal Aviation Administration (FAA), U.S. DOT. ACTION: Notice to Manufacturers of Alternative Fuel Vans. SUMMARY: Projects funded under the Airport Improvement Program (AIP) must... (FAA) is considering issuing waivers to foreign manufacturers of alternative fuel vans. This notice...

Relative permittivity and Hubbard U of pentacene extracted from scanning tunneling microscopy studies of p-doped films

NASA Astrophysics Data System (ADS)

Ha, Sieu D.; Qi, Yabing; Kahn, Antoine

2010-08-01

Temperature-dependent I- V measurements determine that pentacene is effectively p-doped by tetrafluoro-tetracyanoquinodimethane (F 4-TCNQ). It has been shown by scanning tunneling microscopy (STM) that the donated hole is localized by the ionized dopant counter potential, and that the hole can be visualized [4]. Here, it is argued that the effect of the localized hole on STM images should depend on distance as 1/ ɛr, as per the Coulomb potential. By fitting line profiles of localized hole features to the Coulomb potential, it is shown that approximate values for the relative permittivity and Hubbard U of pentacene can be extracted.

Role of vertex corrections in the matrix formulation of the random phase approximation for the multiorbital Hubbard model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Altmeyer, Michaela; Guterding, Daniel; Hirschfeld, P. J.

2016-12-21

In the framework of a multiorbital Hubbard model description of superconductivity, a matrix formulation of the superconducting pairing interaction that has been widely used is designed to treat spin, charge, and orbital fluctuations within a random phase approximation (RPA). In terms of Feynman diagrams, this takes into account particle-hole ladder and bubble contributions as expected. It turns out, however, that this matrix formulation also generates additional terms which have the diagrammatic structure of vertex corrections. Furthermore we examine these terms and discuss the relationship between the matrix-RPA superconducting pairing interaction and the Feynman diagrams that it sums.

Obituary: Thomas C. Van Flandern (1940-2009)

NASA Astrophysics Data System (ADS)

Dunham, David; Slabinski, Victor

2011-12-01

Dr. Thomas Charles Van Flandern, an expert in celestial mechanics and cosmology, died January 9, 2009 in Seattle, Washington, of colon cancer. He was 68. Van Flandern was an astronomer at the U.S. Naval Observatory from 1963 to 1983. He developed software to predict and analyze lunar occultations to improve lunar orbital and fundamental star catalog data. In later years he championed increasingly controversial theories. But his 1978 prediction that some asteroids have natural satellites, which was almost universally rejected, was verified when the Galileo spacecraft photographed Dactyl, a satellite of (243) Ida, during its flyby in 1993. Besides astronomy and computers, he had strong interests in biochemistry and nutrition, and he ran a business selling personal computers in the 1980s. Tom Van Flandern was born June 26, 1940 in Cleveland, Ohio, the first child of Robert F. Van Flandern and Anna Mary Haley. His father, a police officer, left the family when Tom Van Flandern was 5. His mother died when he was 16; he and his siblings then lived with their grandmother, Margery Jobe, until he went to college. Tom Van Flandern became interested in astronomy as a child. He used his first telescope, purchased with newspaper delivery earnings, to observe lunar occultations, and then learned how to predict them, sparking a life-long passion for dynamical astronomy. While attending St. Ignatius High School, Van Flandern and fellow student Thomas Petrie organized the Cleveland Moonwatch team to observe the first artificial satellites, the only team without an adult organizer. In 1958, Tom Van Flandern entered Xavier University where he led the Cincinnati Moonwatch team. He learned computer programming at a summer job with General Electric and wrote software to calculate "look angles" from orbital elements. The Cincinnati team became a top producer of observations using these predictions. Tom obtained a B.S. in mathematics from Xavier in 1962. He spent the next year at

Arnoldus Van Rhijn on aphasia: a forgotten thesis.

PubMed

Eling, Paul

2011-01-01

Aphasia formed a central topic in the discussion on localization of function in the nineteenth century, in particular in France, Germany and Great Brittain. Little is known on contributions from the Netherlands. This paper aims to discuss the contents of Arnoldus Van Rhijn's dissertation on aphasia, written in 1868 and one of the very few Dutch contributions to aphasiology in the nineteenth century. Added to this paper is a translation of the "Physiological Part" of Van Rhijn's dissertation. Van Rhijn discussed three cases with acquired aphasia. He rejected Broca's notion of a cortical center for the articulation of speech and instead regarded the cortex as the site where the will exerted its influence. He argued that there is a certain form of specialization: the will to say something is localized at a different place than the will to write. According to Van Rhijn, the highest motor centers are localized in the subcortical gray areas. Van Rhijn concluded that aphasia may result from lesions to the cortical centers involved in speaking, or from a disconnection of the cortical and subcortical centers. Very little work was done on aphasia in the 19th century in the Netherlands. Van Rhijn's thesis, from an aphasiological point of view of limited value, does show that the notions of "centers", "connections", and "disorders due to disconnections" were generally known before Wernicke, also in the Netherlands. Copyright © 2011 Elsevier Srl. All rights reserved.

Anomalous resistivity and superconductivity in the two-band Hubbard model with one narrow band (Review)

NASA Astrophysics Data System (ADS)

Kagan, M. Yu.; Valkov, V. V.

2011-01-01

We search for marginal Fermi-liquid behavior in the two-band Hubbard model with one narrow band. We consider the limit of low electron densities in the bands and strong intraband and interband Hubbard interactions. We analyze the influence of electron-polaron effects and other mechanisms for mass-enhancement (related to the momentum dependence of the self-energies) on the effective mass and scattering times of light and heavy components in the clean case (electron-electron scattering and no impurities). We find a tendency towards phase separation (towards negative partial compressibility of heavy particles) in the 3D case with a large mismatch between the densities of heavy and light bands in the strong coupling limit. We also find that for low temperatures and equal densities, the resistivity in a homogeneous state R(T )∝T2 behaves as a Fermi-liquid in both 3D and 2D. For temperatures greater than the effective bandwidth for heavy electrons T >Wh*, the coherence of the heavy component breaks down completely. The heavy particles move diffusively in the surrounding light particles. At the same time, light particles scatter on heavy particles as if on immobile (static) impurities. Under these conditions, the heavy component is marginal, while the light component is not. The resistivity approaches saturation for T >Wh* in the 3D case. In 2D the resistivity has a maximum and a localization tail owing to weak-localization corrections of the Altshuler-Aronov type. This behavior of resistivity in 3D could be relevant for some uranium-based heavy-fermion compounds such as UNi2Al3 and in 2D, for some other mixed-valence compounds, possibly including layered manganites. We also consider briefly the superconductive (SC) instability in this model. The leading instability tends to p-wave pairing and is governed by an enhanced Kohn-Luttinger mechanism for SC at low electron densities. The critical temperature corresponds to the pairing of heavy electrons via polarization of

Moment tensor inversion of recent local moderate sized Van Earthquakes: seismicity and active tectonics of the Van region : Eastern Turkey

NASA Astrophysics Data System (ADS)

Kalafat, D.; Suvarikli, M.; Ogutcu, Z.; Kekovali, K.; Ocal, M. F.; Gunes, Y.; Pinar, A.

2013-12-01

The study area of the present research, the Van Region is located at the norththern end of the collision zone between the Anatolia and Arabian plates. Therefore, the southeast border of the Anatolian plate collides with the Arabian plate along the Bitlis Suture Zone. This zone is formed by collision of Arabian and in large scale Eurasian plates at mid-Miocen age. This type of thrust generation as a result of compressional regime extends east-west. The largest recorded earthquakes have all taken place along Southern Turkey (e.g. Lice, 1971; Varto, 1966; Caldiran, 1976). On the 23th of October 2011, an earthquake shook the Van Lake, Eastern Turkey, following a seismic sequence of more than three months in an unprecedented episode for this region characterized by null or low seismicity. The October 23, 2011 Van-Ercis Earthquake (Mw=7.1) was the most devastating resulting in loss of life and destruction. In order to study the aftershocks' activity of this main event, we installed and kept a seismic network of 10 broad-band (BB) stations in the area for an interval of nearly fifteen months. We characterized the seismogenic structure of the zone by calculating a minimum 1-D local velocity model and obtaining precise hypocentre locations. We also calculated fault plane solutions for more than 200 moderate sized earthquakes based on first motion polarities and commonly Moment Tensor Inversion Methods. The seismogenic zone would be localized at aproximately 10 km depth. Generally, the distribution of the important moderate earthquakes and the aftershock distribution shows that the E-W and NE-SW oriented fault segments cause the earthquake activities. Aftershock events are located along the eastern border of Lake Van and mainly between 5 and 10 km depth and disposed in two alignments: a ~E-W-trending alignment that matches with the trace of the Van Trust fault Zone and a NE-trending which could correspond to an structure not previously seen. Selected focal mechanisms show a

Competing phases and orbital-selective behaviors in the two-orbital Hubbard-Holstein model

NASA Astrophysics Data System (ADS)

Li, Shaozhi; Khatami, Ehsan; Johnston, Steven

2017-03-01

We study the interplay between the electron-electron (e-e) and the electron-phonon (e-ph) interactions in the two-orbital Hubbard-Holstein model at half-filling using the dynamical mean-field theory. We find that the e-ph interaction, even at weak couplings, strongly modifies the phase diagram of this model and introduces an orbital-selective Peierls insulating phase (OSPI) that is analogous to the widely studied orbital-selective Mott phase (OSMP). At small e-e and e-ph couplings, we find a competition between the OSMP and the OSPI, while at large couplings, a competition occurs between Mott and charge-density-wave (CDW) insulating phases. We further demonstrate that the Hund's coupling influences the OSPI transition by lowering the energy associated with the CDW. Our results explicitly show that one must be cautious when neglecting the e-ph interaction in multiorbital systems, where multiple electronic interactions create states that are readily influenced by perturbing interactions.

Fractional statistics and quantum scaling properties of the integrable Penson-Kolb-Hubbard chain

NASA Astrophysics Data System (ADS)

Vitoriano, Carlindo; Coutinho-Filho, M. D.

2010-09-01

We investigate the ground-state and low-temperature properties of the integrable version of the Penson-Kolb-Hubbard chain. The model obeys fractional statistical properties, which give rise to fractional elementary excitations and manifest differently in the four regions of the phase diagram U/t versus n , where U is the Coulomb coupling, t is the correlated hopping amplitude, and n is the particle density. In fact, we can find local pair formation, fractionalization of the average occupation number per orbital k , or U - and n -dependent average electric charge per orbital k . We also study the scaling behavior near the U -driven quantum phase transitions and characterize their universality classes. Finally, it is shown that in the regime of parameters where local pair formation is energetically more favorable, the ground state exhibits power-law superconductivity; we also stress that above half filling the pair-hopping term stabilizes local Cooper pairs in the repulsive- U regime for U

Pseudogap and Fermi-Surface Topology in the Two-Dimensional Hubbard Model

NASA Astrophysics Data System (ADS)

Wu, Wei; Scheurer, Mathias S.; Chatterjee, Shubhayu; Sachdev, Subir; Georges, Antoine; Ferrero, Michel

2018-04-01

One of the distinctive features of hole-doped cuprate superconductors is the onset of a "pseudogap" below a temperature T* . Recent experiments suggest that there may be a connection between the existence of the pseudogap and the topology of the Fermi surface. Here, we address this issue by studying the two-dimensional Hubbard model with two distinct numerical methods. We find that the pseudogap only exists when the Fermi surface is holelike and that, for a broad range of parameters, its opening is concomitant with a Fermi-surface topology change from electronlike to holelike. We identify a common link between these observations: The polelike feature of the electronic self-energy associated with the formation of the pseudogap is found to also control the degree of particle-hole asymmetry, and hence the Fermi-surface topology transition. We interpret our results in the framework of an SU(2) gauge theory of fluctuating antiferromagnetism. We show that a mean-field treatment of this theory in a metallic state with U(1) topological order provides an explanation of this polelike feature and a good description of our numerical results. We discuss the relevance of our results to experiments on cuprates.

The MFA ground states for the extended Bose-Hubbard model with a three-body constraint

NASA Astrophysics Data System (ADS)

Panov, Yu. D.; Moskvin, A. S.; Vasinovich, E. V.; Konev, V. V.

2018-05-01

We address the intensively studied extended bosonic Hubbard model (EBHM) with truncation of the on-site Hilbert space to the three lowest occupation states n = 0 , 1 , 2 in frames of the S = 1 pseudospin formalism. Similar model was recently proposed to describe the charge degree of freedom in a model high-T c cuprate with the on-site Hilbert space reduced to the three effective valence centers, nominally Cu1+;2+;3+. With small corrections the model becomes equivalent to a strongly anisotropic S = 1 quantum magnet in an external magnetic field. We have applied a generalized mean-field approach and quantum Monte-Carlo technique for the model 2D S = 1 system with a two-particle transport to find the ground state phase with its evolution under deviation from half-filling.

[Implementation of vanA and vanB genes by PCR technique research interest in system (Xpert vanA/vanB CepheidR) closed in a laboratory of microbiology in managing an outbreak to Enterococcus faecium resistant glycopeptide (EfRG)].

PubMed

Dekeyser, S; Beclin, E; Descamps, D

2011-04-01

The closed system PCR for the rapid detection of vanA and vanB genes (Xpert vanA/vanB Cepheid(®)) was evaluated in our laboratory, to improve the rapidity of the response and thus the management of patients and isolation measures during two GRE outbreaks. From March to December2009, 565 samples were analysed by PCR associated to bacterial culture initially for all samples for 2months (n = 75), and thereafter for PCR-positive samples only. In this study, sensitivity and negative predictive values of the PCR were 100%. Specificity was evaluated in the presence and absence of outbreak: 69.3 and 76.8% respectively. The variability of false positive rates between units were lower in nonepidemic than during epidemic phase. The global false positive rate was 23.9%. This easy-to-use technology provides rapid results… four samples are tested in 1h versus 72h for culture. Despite its reagent cost, it represents an important hospital diagnostic tool: improvement of the management of cohorting areas and patient transfer between units, adaptation of isolation measures and treatments. However, culture remains necessary to confirm any positive result obtained by PCR and for epidemiological surveillance. Copyright © 2010 Elsevier Masson SAS. All rights reserved.

Comparative DMFT study of the eg-orbital Hubbard model in thin films

NASA Astrophysics Data System (ADS)

Rüegg, Andreas; Hung, Hsiang-Hsuan; Gull, Emanuel; Fiete, Gregory A.

2014-02-01

Heterostructures of transition-metal oxides have emerged as a new route to engineer electronic systems with desired functionalities. Motivated by these developments, we study a two-orbital Hubbard model in a thin-film geometry confined along the cubic [001] direction using the dynamical mean-field theory. We contrast the results of two approximate impurity solvers (exact diagonalization and one-crossing approximation) to the results of the numerically exact continuous-time quantum Monte Carlo solver. Consistent with earlier studies, we find that the one-crossing approximation performs well in the insulating regime, while the advantage of the exact-diagonalization-based solver is more pronounced in the metallic regime. We then investigate various aspects of strongly correlated eg-orbital systems in thin-film geometries. In particular, we show how the interfacial orbital polarization dies off quickly a few layers from the interface and how the film thickness affects the location of the interaction-driven Mott transition. In addition, we explore the changes in the electronic structure with varying carrier concentration and identify large variations of the orbital polarization in the strongly correlated regime.

Effective field theories for van der Waals interactions

NASA Astrophysics Data System (ADS)

Brambilla, Nora; Shtabovenko, Vladyslav; Tarrús Castellà, Jaume; Vairo, Antonio

2017-06-01

Van der Waals interactions between two neutral but polarizable systems at a separation R much larger than the typical size of the systems are at the core of a broad sweep of contemporary problems in settings ranging from atomic, molecular and condensed matter physics to strong interactions and gravity. In this paper, we reexamine the dispersive van der Waals interactions between two hydrogen atoms. The novelty of the analysis resides in the usage of nonrelativistic effective field theories of quantum electrodynamics. In this framework, the van der Waals potential acquires the meaning of a matching coefficient in an effective field theory, dubbed van der Waals effective field theory, suited to describe the low-energy dynamics of an atom pair. It may be computed systematically as a series in R times some typical atomic scale and in the fine-structure constant α . The van der Waals potential gets short-range contributions and radiative corrections, which we compute in dimensional regularization and renormalize here for the first time. Results are given in d space-time dimensions. One can distinguish among different regimes depending on the relative size between 1 /R and the typical atomic bound-state energy, which is of order m α2. Each regime is characterized by a specific hierarchy of scales and a corresponding tower of effective field theories. The short-distance regime is characterized by 1 /R ≫m α2 and the leading-order van der Waals potential is the London potential. We also compute next-to-next-to-next-to-leading-order corrections. In the long-distance regime we have 1 /R ≪m α2. In this regime, the van der Waals potential contains contact terms, which are parametrically larger than the Casimir-Polder potential that describes the potential at large distances. In the effective field theory, the Casimir-Polder potential counts as a next-to-next-to-next-to-leading-order effect. In the intermediate-distance regime, 1 /R ˜m α2, a significantly more complex

The Economics of van der Waals Force Engineering

NASA Astrophysics Data System (ADS)

Pinto, Fabrizio

2008-01-01

As micro-electro-mechanical system (MEMS) fabrication continues on an ever-decreasing scale, new technological challenges must be successfully negotiated if Moore's Law is to be an even approximately valid model of the future of device miniaturization. Among the most significant obstacles is the existence of strong surface forces related to quantum mechanical van der Waals interatomic interactions, which rapidly diverge as the distance between any two neutral boundaries decreases. The van der Waals force is a contributing factor in several device failures and limitations, including, for instance, stiction and oscillator non-linearities. In the last decade, however, it has been conclusively shown that van der Waals forces are not just a MEMS limitation but can be engineered in both magnitude and sign so as to enable classes of proprietary inventions which either deliver novel capabilities or improve upon existing ones. The evolution of van der Waals force research from an almost exclusively theoretical field in quantum-electro-dynamics to an enabling nanotechnology discipline represents a useful example of the ongoing paradigm shift from government-centered to private-capital funded R&D in cutting-edge physics leading to potentially profitable products. In this paper, we discuss the reasons van der Waals force engineering may lead to the creation of thriving markets both in the short and medium terms by highlighting technical challenges that can be competitively addressed by this novel approach. We also discuss some notable obstacles to the cultural transformation of the academic research community required for the emergence of a functional van der Waals force engineering industry worldwide.

Arthur van Gehuchten takes neurology to the movies.

PubMed

Aubert, Geneviève

2002-11-26

To present the cinematographic production of Arthur Van Gehuchten (1861-1914) and to put this collection into its medical and sociocultural context. The arrival of Edison's Kinetoscope (1891) and Lumière's Cinématographe (1895) provoked the immediate interest of neurologists who foresaw the potential of motion pictures for illustration, research, and teaching. Arthur Van Gehuchten, professor of anatomy and neurology at the Catholic University of Louvain, was trained as a microscopist and a cytologist. From neuroanatomy, he progressively broadened his interest to neurology. Van Gehuchten was an avant-garde teacher, eager to adopt new visual aids. In 1895, he attended the first cinematographic screenings. Medical cinematography was soon brought into disrepute in European academic circles, when films made by the French surgeon Doyen were copied and shown on fairgrounds. Nevertheless, in 1905, Van Gehuchten began to film neurologic patients. He used this technique extensively to demonstrate clinical signs, to illustrate neurologic diseases, and to document functional evolution following surgery. For decades, these films were screened for medical students by Van Gehuchten's successors to the chair of neurology. The original nitrate films (more than 2 hours) have been recently rediscovered. They have been restored by the Royal Belgian Film Archive, where they are the oldest Belgian films. At the beginning of the 20th century, Van Gehuchten built up a collection of moving pictures for teaching purposes. This was one of the first such undertakings. This unique set of films has miraculously survived, and serves as an important archive of nervous diseases and their manifestations prior to the advent of modern therapies.

Nodal Statistics for the Van Vleck Polynomials

NASA Astrophysics Data System (ADS)

Bourget, Alain

The Van Vleck polynomials naturally arise from the generalized Lamé equation as the polynomials of degree for which Eq. (1) has a polynomial solution of some degree k. In this paper, we compute the limiting distribution, as well as the limiting mean level spacings distribution of the zeros of any Van Vleck polynomial as N --> ∞.

Vehicle test report: Jet Industries Electra Van 600

NASA Technical Reports Server (NTRS)

Price, T. W.; Wirth, V. A., Jr.

1982-01-01

The Electra Van 600, an electric vehicle, was tested. Tests were performed to characterize parameters of the Electra Van 600 and to provide baseline data to be used for comparison of improved batteries and to which will be incorporated into the vehicle. The vehicle tests concentrated on the electrical drive subsystem, the batteries, controller, and motor; coastdowns to characterize the road load and range evaluation for cyclic and constant speed conditions; and qualitative performance was evaluated. It is found that the Electra Van 600 range performance is approximately equal to the majority of the vehicles tested previously.

Competing phases, phase separation, and coexistence in the extended one-dimensional bosonic Hubbard model

DOE PAGES

Batrouni, G. G.; Rousseau, V. G.; Scalettar, R. T.; ...

2014-11-17

Here, we study the phase diagram of the one-dimensional bosonic Hubbard model with contact (U) and near neighbor (V ) interactions focusing on the gapped Haldane insulating (HI) phase which is characterized by an exotic nonlocal order parameter. The parameter regime (U, V and μ) where this phase exists and how it competes with other phases such as the supersolid (SS) phase, is incompletely understood. We use the Stochastic Green Function quantum Monte Carlo algorithm as well as the density matrix renormalization group to map out the phase diagram. The HI exists only at = 1, the SS phase existsmore » for a very wide range of parameters (including commensurate fillings) and displays power law decay in the one body Green function were our main conclusions. Additionally, we show that at fixed integer density, the system exhibits phase separation in the (U, V ) plane.« less

Scaling laws for van der Waals interactions in nanostructured materials.

PubMed

Gobre, Vivekanand V; Tkatchenko, Alexandre

2013-01-01

Van der Waals interactions have a fundamental role in biology, physics and chemistry, in particular in the self-assembly and the ensuing function of nanostructured materials. Here we utilize an efficient microscopic method to demonstrate that van der Waals interactions in nanomaterials act at distances greater than typically assumed, and can be characterized by different scaling laws depending on the dimensionality and size of the system. Specifically, we study the behaviour of van der Waals interactions in single-layer and multilayer graphene, fullerenes of varying size, single-wall carbon nanotubes and graphene nanoribbons. As a function of nanostructure size, the van der Waals coefficients follow unusual trends for all of the considered systems, and deviate significantly from the conventionally employed pairwise-additive picture. We propose that the peculiar van der Waals interactions in nanostructured materials could be exploited to control their self-assembly.

Rater Biases in Genetically Informative Research Designs: Comment on Bartels, Boomsma, Hudziak, van Beijsterveldt, and van den Oord (2007)

ERIC Educational Resources Information Center

Hoyt, William T.

2007-01-01

Rater biases are of interest to behavior genetic researchers, who often use ratings data as a basis for studying heritability. Inclusion of multiple raters for each sibling pair (M. Bartels, D. I. Boomsma, J. J. Hudziak, T. C. E. M. van Beijsterveldt, & E. J. C. G. van den Oord, 2007) is a promising strategy for controlling bias variance and may…

RpoS induces expression of the Vibrio anguillarum quorum-sensing regulator VanT.

PubMed

Weber, Barbara; Croxatto, Antony; Chen, Chang; Milton, Debra L

2008-03-01

In vibrios, regulation of the Vibrio harveyi-like LuxR transcriptional activators occurs post-transcriptionally via small regulatory RNAs (sRNAs) that destabilize the luxR mRNA at a low cell population, eliminating expression of LuxR. Expression of the sRNAs is modulated by the vibrio quorum-sensing phosphorelay systems. However, vanT mRNA, which encodes a LuxR homologue in Vibrio anguillarum, is abundant at low and high cell density, indicating that VanT expression may be regulated via additional mechanisms. In this study, Western analyses showed that VanT was expressed throughout growth with a peak of expression during late exponential growth. VanO induced partial destabilization of vanT mRNA via activation of at least one Qrr sRNA. Interestingly, the sigma factor RpoS significantly stabilized vanT mRNA and induced VanT expression during late exponential growth. This induction was in part due to RpoS repressing expression of Hfq, an RNA chaperone. RpoS is not part of the quorum-sensing regulatory cascade since RpoS did not regulate expression or activity of VanO, and RpoS was not regulated by VanO or VanT. VanT and RpoS were needed for survival following UV irradiation and for pigment and metalloprotease production, suggesting that RpoS works with the quorum-sensing systems to modulate expression of VanT, which regulates survival and stress responses.

van Manen's method and reduction in a phenomenological hermeneutic study.

PubMed

Heinonen, Kristiina

2015-03-01

To describe van Manen's method and concept of reduction in a study that used a phenomenological hermeneutic approach. Nurse researchers have used van Manen's method in different ways. Participants' lifeworlds are described in depth, but descriptions of reduction have been brief. The literature and knowledge review and manual search of research articles. Databases Web Science, PubMed, CINAHL and PsycINFO, without applying a time period, to identify uses of van Manen's method. This paper shows how van Manen's method has been used in nursing research and gives some examples of van Manen's reduction. Reduction enables us to conduct in-depth phenomenological hermeneutic research and understand people's lifeworlds. As there are many variations in adapting reduction, it is complex and confusing. This paper contributes to the discussion of phenomenology, hermeneutic study and reduction. It opens up reduction as a method for researchers to exploit.

Quantum Bose-Hubbard model with an evolving graph as a toy model for emergent spacetime

NASA Astrophysics Data System (ADS)

Hamma, Alioscia; Markopoulou, Fotini; Lloyd, Seth; Caravelli, Francesco; Severini, Simone; Markström, Klas

2010-05-01

We present a toy model for interacting matter and geometry that explores quantum dynamics in a spin system as a precursor to a quantum theory of gravity. The model has no a priori geometric properties; instead, locality is inferred from the more fundamental notion of interaction between the matter degrees of freedom. The interaction terms are themselves quantum degrees of freedom so that the structure of interactions and hence the resulting local and causal structures are dynamical. The system is a Hubbard model where the graph of the interactions is a set of quantum evolving variables. We show entanglement between spatial and matter degrees of freedom. We study numerically the quantum system and analyze its entanglement dynamics. We analyze the asymptotic behavior of the classical model. Finally, we discuss analogues of trapped surfaces and gravitational attraction in this simple model.

``Glue" approximation for the pairing interaction in the Hubbard model with next nearest neighbor hopping

NASA Astrophysics Data System (ADS)

Khatami, Ehsan; Macridin, Alexandru; Jarrell, Mark

2008-03-01

Recently, several authors have employed the ``glue" approximation for the Cuprates in which the full pairing vertex is approximated by the spin susceptibility. We study this approximation using Quantum Monte Carlo Dynamical Cluster Approximation methods on a 2D Hubbard model. By considering a reasonable finite value for the next nearest neighbor hopping, we find that this ``glue" approximation, in the current form, does not capture the correct pairing symmetry. Here, d-wave is not the leading pairing symmetry while it is the dominant symmetry using the ``exact" QMC results. We argue that the sensitivity of this approximation to the band structure changes leads to this inconsistency and that this form of interaction may not be the appropriate description of the pairing mechanism in Cuprates. We suggest improvements to this approximation which help to capture the the essential features of the QMC data.

Origami rules for the construction of localized eigenstates of the Hubbard model in decorated lattices

NASA Astrophysics Data System (ADS)

Dias, R. G.; Gouveia, J. D.

2015-11-01

We present a method of construction of exact localized many-body eigenstates of the Hubbard model in decorated lattices, both for U = 0 and U → ∞. These states are localized in what concerns both hole and particle movement. The starting point of the method is the construction of a plaquette or a set of plaquettes with a higher symmetry than that of the whole lattice. Using a simple set of rules, the tight-binding localized state in such a plaquette can be divided, folded and unfolded to new plaquette geometries. This set of rules is also valid for the construction of a localized state for one hole in the U → ∞ limit of the same plaquette, assuming a spin configuration which is a uniform linear combination of all possible permutations of the set of spins in the plaquette.

Genomic and expression analysis of the vanG-like gene cluster of Clostridium difficile.

PubMed

Peltier, Johann; Courtin, Pascal; El Meouche, Imane; Catel-Ferreira, Manuella; Chapot-Chartier, Marie-Pierre; Lemée, Ludovic; Pons, Jean-Louis

2013-07-01

Primary antibiotic treatment of Clostridium difficile intestinal diseases requires metronidazole or vancomycin therapy. A cluster of genes homologous to enterococcal glycopeptides resistance vanG genes was found in the genome of C. difficile 630, although this strain remains sensitive to vancomycin. This vanG-like gene cluster was found to consist of five ORFs: the regulatory region consisting of vanR and vanS and the effector region consisting of vanG, vanXY and vanT. We found that 57 out of 83 C. difficile strains, representative of the main lineages of the species, harbour this vanG-like cluster. The cluster is expressed as an operon and, when present, is found at the same genomic location in all strains. The vanG, vanXY and vanT homologues in C. difficile 630 are co-transcribed and expressed to a low level throughout the growth phases in the absence of vancomycin. Conversely, the expression of these genes is strongly induced in the presence of subinhibitory concentrations of vancomycin, indicating that the vanG-like operon is functional at the transcriptional level in C. difficile. Hydrophilic interaction liquid chromatography (HILIC-HPLC) and MS analysis of cytoplasmic peptidoglycan precursors of C. difficile 630 grown without vancomycin revealed the exclusive presence of a UDP-MurNAc-pentapeptide with an alanine at the C terminus. UDP-MurNAc-pentapeptide [d-Ala] was also the only peptidoglycan precursor detected in C. difficile grown in the presence of vancomycin, corroborating the lack of vancomycin resistance. Peptidoglycan structures of a vanG-like mutant strain and of a strain lacking the vanG-like cluster did not differ from the C. difficile 630 strain, indicating that the vanG-like cluster also has no impact on cell-wall composition.

Driven Bose-Hubbard model with a parametrically modulated harmonic trap

NASA Astrophysics Data System (ADS)

Mann, N.; Bakhtiari, M. Reza; Massel, F.; Pelster, A.; Thorwart, M.

2017-04-01

We investigate a one-dimensional Bose-Hubbard model in a parametrically driven global harmonic trap. The delicate interplay of both the local interaction of the atoms in the lattice and the driving of the global trap allows us to control the dynamical stability of the trapped quantum many-body state. The impact of the atomic interaction on the dynamical stability of the driven quantum many-body state is revealed in the regime of weak interaction by analyzing a discretized Gross-Pitaevskii equation within a Gaussian variational ansatz, yielding a Mathieu equation for the condensate width. The parametric resonance condition is shown to be modified by the atom interaction strength. In particular, the effective eigenfrequency is reduced for growing interaction in the mean-field regime. For a stronger interaction, the impact of the global parametric drive is determined by the numerically exact time-evolving block decimation scheme. When the trapped bosons in the lattice are in a Mott insulating state, the absorption of energy from the driving field is suppressed due to the strongly reduced local compressibility of the quantum many-body state. In particular, we find that the width of the local Mott region shows a breathing dynamics. Finally, we observe that the global modulation also induces an effective time-independent inhomogeneous hopping strength for the atoms.

Van der waals forces on thin liquid films in capillary tubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herdt, G.C.; Swanson, L.W.

1993-10-01

A theory of the van der Waals attraction between a thin liquid films and a capillary tube is presented assuming the presence of a vapor-liquid interface. The model is based on the surface mode analysis method of van Kampen et al. Values for the van der Waals interaction energy per unit area were calculated for liquid films of pentane on a gold substrate assuming a thin liquid film. Results indicate that the effect of capillary curvature on the van der Waals interaction increases as the ratio of the liquid film thickness to the capillary radius is increased. This trend ismore » consistent with predictions based on the Hamaker theory. Deviations from results based on the Hamaker theory are easily explained in terms of retardation of the van der Waals interaction. Because the effect of capillary curvature increases in the regime where retardation effects become important, curvature effects constitute a small correction to the van der Waals forces in a capillary tube.« less

Waardering en Analyse van Simulatieresultaten (Valuation and Analysis of Simulation Results)

DTIC Science & Technology

1991-12-01

is uit de tabel van de Students T-verdeling te halen . Deze wordt aangeduid met t,(v), waarin a de overschrijdingskans en v bet aantal vrijheidsgraden...2 vrijheidsgraden. Uit de tabol van de Student’s t-verdeling zija nu de kritieke waardon R, on R2 to halen zodanig dat P(t >R2 ) = i Wordt or eon...analyse van simnulatieresultaten - TDCnaK RAPPORTE1CENTRALE Frederikkazerne, Geb. 140 AD-A25 470van den Burchlaan 31AD-A25 470Telefoon: 070-3166394

Martin Van Buren National Historic Site transportation analysis report

DOT National Transportation Integrated Search

2010-10-01

The Volpe Transportation Systems Center (Volpe Center) is providing transportation support to Martin Van Buren National Historic Site's (NHS) first General Management Plan (GMP), which will be complete in 2010 or 2011. Currently, Martin Van Buren NHS...

TRILEX and G W +EDMFT approach to d -wave superconductivity in the Hubbard model

NASA Astrophysics Data System (ADS)

Vučičević, J.; Ayral, T.; Parcollet, O.

2017-09-01

We generalize the recently introduced TRILEX approach (TRiply irreducible local EXpansion) to superconducting phases. The method treats simultaneously Mott and spin-fluctuation physics using an Eliashberg theory supplemented by local vertex corrections determined by a self-consistent quantum impurity model. We show that, in the two-dimensional Hubbard model, at strong coupling, TRILEX yields a d -wave superconducting dome as a function of doping. Contrary to the standard cluster dynamical mean field theory (DMFT) approaches, TRILEX can capture d -wave pairing using only a single-site effective impurity model. We also systematically explore the dependence of the superconducting temperature on the bare dispersion at weak coupling, which shows a clear link between strong antiferromagnetic (AF) correlations and the onset of superconductivity. We identify a combination of hopping amplitudes particularly favorable to superconductivity at intermediate doping. Finally, we study within G W +EDMFT the low-temperature d -wave superconducting phase at strong coupling in a region of parameter space with reduced AF fluctuations.

Functional renormalization group and bosonization as a solver for 2D fermionic Hubbard models

NASA Astrophysics Data System (ADS)

Schuetz, Florian; Marston, Brad

2007-03-01

The functional renormalization group (fRG) provides an unbiased framework to analyze competing instabilities in two-dimensional electron systems and has been used extensively over the past decade [1]. In order to obtain an equally unbiased tool to interprete the flow, we investigate the combination of a many-patch, one-loop calculation with higher dimensional bosonization [2] of the resulting low-energy action. Subsequently a semi-classical approximation [3] can be used to describe the resulting phases. The spinless Hubbard model on a square lattice with nearest neighbor repulsion is investigated as a test case. [1] M. Salmhofer and C. Honerkamp, Prog. Theor. Phys. 105, 1 (2001). [2] A. Houghton, H.-J. Kwon, J. B. Marston, Adv.Phys. 49, 141 (2000); P. Kopietz, Bosonization of interacting fermions in arbitrary dimensions, (Springer, Berlin, 1997). [3] H.-H. Lin, L. Balents, M. P. A. Fisher, Phys. Rev. B 56, 6569 6593 (1997); J. O. Fjaerestad, J. B. Marston, U. Schollwoeck, Ann. Phys. (N.Y.) 321, 894 (2006).

A. E. van Vogt: In Search of Meaning.

ERIC Educational Resources Information Center

Drake, H. L.

A general semantics perspective of science fiction writer A. E. van Vogt is presented in this paper. The first major section of the paper contains a biographical sketch of van Vogt and traces the influence of A. Korzybski's work on general semantics, "Science and Sanity," on his writing, while the second major section provides an…

Van Driest transformation and compressible wall-bounded flows

NASA Technical Reports Server (NTRS)

Huang, P. G.; Coleman, G. N.

1994-01-01

The transformation validity question utilizing resulting data from direct numerical simulations (DNS) of supersonic, isothermal cold wall channel flow was investigated. The DNS results stood for a wide scope of parameter and were suitable for the purpose of examining the generality of Van Driest transformation. The Van Driest law of the wall can be obtained from the inner-layer similarity arguments. It was demonstrated that the Van Driest transformation cannot be incorporated to collapse the sublayer and log-layer velocity profiles simultaneously. Velocity and temperature predictions according to the preceding composite mixing-length model were presented. Despite satisfactory congruity with the DNS data, the model must be perceived as an engineering guide and not as a rigorous analysis.

Non-Fermi Liquid Behavior and Continuously Tunable Resistivity Exponents in the Anderson-Hubbard Model at Finite Temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, Niravkumar D.; Mukherjee, Anamitra; Kaushal, Nitin

Here, we employ a recently developed computational many-body technique to study for the first time the half-filled Anderson-Hubbard model at finite temperature and arbitrary correlation U and disorder V strengths. Interestingly, the narrow zero temperature metallic range induced by disorder from the Mott insulator expands with increasing temperature in a manner resembling a quantum critical point. Our study of the resistivity temperature scaling T α for this metal reveals non-Fermi liquid characteristics. Moreover, a continuous dependence of α on U and V from linear to nearly quadratic is observed. We argue that these exotic results arise from a systematic changemore » with U and V of the “effective” disorder, a combination of quenched disorder and intrinsic localized spins.« less

Characteristics of the Mott transition and electronic states of high-temperature cuprate superconductors from the perspective of the Hubbard model

NASA Astrophysics Data System (ADS)

Kohno, Masanori

2018-04-01

A fundamental issue of the Mott transition is how electrons behaving as single particles carrying spin and charge in a metal change into those exhibiting separated spin and charge excitations (low-energy spin excitation and high-energy charge excitation) in a Mott insulator. This issue has attracted considerable attention particularly in relation to high-temperature cuprate superconductors, which exhibit electronic states near the Mott transition that are difficult to explain in conventional pictures. Here, from a new viewpoint of the Mott transition based on analyses of the Hubbard model, we review anomalous features observed in high-temperature cuprate superconductors near the Mott transition.

Unitary n -designs via random quenches in atomic Hubbard and spin models: Application to the measurement of Rényi entropies

NASA Astrophysics Data System (ADS)

Vermersch, B.; Elben, A.; Dalmonte, M.; Cirac, J. I.; Zoller, P.

2018-02-01

We present a general framework for the generation of random unitaries based on random quenches in atomic Hubbard and spin models, forming approximate unitary n -designs, and their application to the measurement of Rényi entropies. We generalize our protocol presented in Elben et al. [Phys. Rev. Lett. 120, 050406 (2018), 10.1103/PhysRevLett.120.050406] to a broad class of atomic and spin-lattice models. We further present an in-depth numerical and analytical study of experimental imperfections, including the effect of decoherence and statistical errors, and discuss connections of our approach with many-body quantum chaos.

Alternative Fuels Data Center: Natural Gas Delivery Vans Support McShan

Science.gov Websites

FloristA> Natural Gas Delivery Vans Support McShan Florist to someone by E-mail Share Alternative Natural Gas Delivery Vans Support McShan Florist Watch how a Dallas, Texas, florist reduces emissions and saves money fueling delivery vans with compressed natural gas. For information about this project

Van de Hulst Essay: Light Scattering, Aerosols, Clouds, Climate, Hendrik van de Hulst, and I

DOE PAGES

Chylek, Petr

2017-12-06

It is not often that I have the opportunity to write something that is not a scientific study, and I am thankful for this opportunity to express my thoughts with regard to pursuits that are greater than those of science. In this van de Hulst assay, to honor Hendrik van de Hulst, I briefly summarize a few points from Hendrik's life that I find especially interesting, including his interests in spiritual (or religious) aspects of life, and his decision to avoid involvement in nucleation problems, a critical and basic uncertainty of current climate models. Finally, after that, I present brieflymore » a few episodes from my own experiences as an apprentice of science and life.« less

Van de Hulst Essay: Light Scattering, Aerosols, Clouds, Climate, Hendrik van de Hulst, and I

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chylek, Petr

It is not often that I have the opportunity to write something that is not a scientific study, and I am thankful for this opportunity to express my thoughts with regard to pursuits that are greater than those of science. In this van de Hulst assay, to honor Hendrik van de Hulst, I briefly summarize a few points from Hendrik's life that I find especially interesting, including his interests in spiritual (or religious) aspects of life, and his decision to avoid involvement in nucleation problems, a critical and basic uncertainty of current climate models. Finally, after that, I present brieflymore » a few episodes from my own experiences as an apprentice of science and life.« less

Magnon Splitting Induced by Charge Transfer in the Three-Orbital Hubbard Model

NASA Astrophysics Data System (ADS)

Wang, Yao; Huang, Edwin W.; Moritz, Brian; Devereaux, Thomas P.

2018-06-01

Understanding spin excitations and their connection to unconventional superconductivity have remained central issues since the discovery of cuprates. Direct measurement of the dynamical spin structure factor in the parent compounds can provide key information on important interactions relevant in the doped regime, and variations in the magnon dispersion have been linked closely to differences in crystal structure between families of cuprate compounds. Here, we elucidate the relationship between spin excitations and various controlling factors thought to be significant in high-Tc materials by systematically evaluating the dynamical spin structure factor for the three-orbital Hubbard model, revealing differences in the spin dispersion along the Brillouin zone axis and the diagonal. Generally, we find that the absolute energy scale and momentum dependence of the excitations primarily are sensitive to the effective charge-transfer energy, while changes in the on-site Coulomb interactions have little effect on the details of the dispersion. In particular, our result highlights the splitting between spin excitations along the axial and diagonal directions in the Brillouin zone. This splitting decreases with increasing charge-transfer energy and correlates with changes in the apical oxygen position, and general structural variations, for different cuprate families.

Multiple Voices in Charles Van Riper's Desensitization Therapy

ERIC Educational Resources Information Center

Leahy, Margaret M.

2008-01-01

Background: Charles Van Riper (1905-94) author, researcher and practitioner, was one of the major contributors to the field of stuttering in the 20th century. His series of Action Therapy videotapes provide a useful model of how therapy was implemented by a master clinician. Aims: Van Riper's session with a client is analysed to reveal how voices…

Militaire Toepassingen Van Adaptieve Optiek (Military Applications of Adaptive Optics)

DTIC Science & Technology

2006-09-01

dat op dit moment met de beschikbare theorie mogelijk is. Een ander interessant aspect is de mate waarin de turbulentie effecten het jam patroon...systemen In WEAG studie JP8. 11 is aangetoond dat in theorie adaptieve technieken een verbetering van de prestaties van een DIRCM systeem kunnen...Molenaar; Theorie van de laserscintillometer; TNO repot PHL 1978-16 (1978). TNO-rapport I TNO-DV 2006 A336 35/35 6 Ondertekening Den Haag, september 2006

Evaluation of Streamflow Gain-Loss Characteristics of Hubbard Creek, in the Vicinity of a Mine-Permit Area, Delta County, Colorado, 2007

USGS Publications Warehouse

Ruddy, Barbara C.; Williams, Cory A.

2007-01-01

In 2007, the U.S. Geological Survey, in cooperation with Bowie Mining Company, initiated a study to characterize the streamflow and streamflow gain-loss in a reach of Hubbard Creek in Delta County, Colorado, in the vicinity of a mine-permit area planned for future coal mining. Premining streamflow characteristics and streamflow gain-loss variation were determined so that pre- and postmining gain-loss characteristics could be compared. This report describes the methods used in this study and the results of two streamflow-measurement sets collected during low-flow conditions. Streamflow gain-loss measurements were collected using rhodamine WT and sodium bromide tracers at four sites spanning the mine-permit area on June 26-28, 2007. Streamflows were estimated and compared between four measurement sites within three stream subreaches of the study reach. Data from two streamflow-gaging stations on Hubbard Creek upstream and downstream from the mine-permit area were evaluated. Streamflows at the stations were continuous, and flow at the upstream station nearly always exceeded the streamflow at the downstream station. Furthermore, streamflow at both stations showed similar diurnal patterns with traveltime offsets. On June 26, streamflow from the gain-loss measurements was greater at site 1 (most upstream site) than at site 4 (most downstream site); on June 27, streamflow was greater at site 4 than at site 2; and on June 27, there was no difference in streamflow between sites 2 and 3. Data from streamflow-gaging stations 09132940 and 09132960 showed diurnal variations and overall decreasing streamflow over time. The data indicate a dynamic system, and streamflow can increase or decrease depending on hydrologic conditions. The streamflow within the study reach was greater than the streamflows at either the upstream or downstream stations. A second set of gain-loss measurements was collected at sites 2 and 4 on November 8-9, 2007. On November 8, streamflow was greater at

Local entanglement entropy of fermions as a marker of quantum phase transition in the one-dimensional Hubbard model

NASA Astrophysics Data System (ADS)

Cha, Min-Chul; Chung, Myung-Hoon

2018-05-01

We study quantum phase transition of interacting fermions by measuring the local entanglement entropy in the one-dimensional Hubbard model. The reduced density matrices for blocks of a few sites are constructed from the ground state wave function in infinite systems by adopting the matrix product state representation where time-evolving block decimations are performed to obtain the lowest energy states. The local entanglement entropy, constructed from the reduced density matrices, as a function of the chemical potential shows clear signatures of the Mott transition. The value of the central charge, numerically determined from the universal properties of the local entanglement entropy, confirms that the transition is caused by the suppression of the charge degrees of freedom.

Van Gogh from Space

NASA Image and Video Library

2017-12-08

Van Gogh from Space - July 13th, 2005 Description: In the style of Van Gogh's painting "Starry Night," massive congregations of greenish phytoplankton swirl in the dark water around Gotland, a Swedish island in the Baltic Sea. Phytoplankton are microscopic marine plants that form the first link in nearly all ocean food chains. Population explosions, or blooms, of phytoplankton, like the one shown here, occur when deep currents bring nutrients up to sunlit surface waters, fueling the growth and reproduction of these tiny plants. Credit: USGS/NASA/Landsat 7 To learn more about the Landsat satellite go to: landsat.gsfc.nasa.gov/ NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Join us on Facebook

Multilevel population genetic analysis of vanA and vanB Enterococcus faecium causing nosocomial outbreaks in 27 countries (1986-2012).

PubMed

Freitas, Ana R; Tedim, Ana P; Francia, Maria V; Jensen, Lars B; Novais, Carla; Peixe, Luísa; Sánchez-Valenzuela, Antonio; Sundsfjord, Arnfinn; Hegstad, Kristin; Werner, Guido; Sadowy, Ewa; Hammerum, Anette M; Garcia-Migura, Lourdes; Willems, Rob J; Baquero, Fernando; Coque, Teresa M

2016-12-01

Vancomycin-resistant Enterococcus faecium (VREfm) have been increasingly reported since the 1980s. Despite the high number of published studies about VRE epidemiology, the dynamics and evolvability of these microorganisms are still not fully understood. A multilevel population genetic analysis of VREfm outbreak strains since 1986, representing the first comprehensive characterization of plasmid content in E. faecium, was performed to provide a detailed view of potential transmissible units. From a comprehensive MeSH search, we identified VREfm strains causing hospital outbreaks (1986-2012). In total, 53 VanA and 18 VanB isolates (27 countries, 5 continents) were analysed and 82 vancomycin-susceptible E. faecium (VSEfm) were included for comparison. Clonal relatedness was established by PFGE and MLST (goeBURST/Bayesian Analysis of Population Structure, BAPS). Characterization of van transposons (PCR mapping, RFLP, sequencing), plasmids (transfer, ClaI-RFLP, PCR typing of relaxases, replication-initiation proteins and toxin-antitoxin systems, hybridization, sequencing), bacteriocins and virulence determinants (PCR, hybridization, sequencing) was performed. VREfm were mainly associated with major human lineages ST17, ST18 and ST78. VREfm and VSEfm harboured plasmids of different families [RCR, small theta plasmids, RepA_N (pRUM/pLG1) and Inc18] able to yield mosaic elements. Tn1546-vanA was mainly located on pRUM/Axe-Txe (USA) and Inc18-pIP186 (Europe) plasmids. The VanB2 type (Tn5382/Tn1549) was predominant among VanB strains (chromosome and plasmids). Both strains and plasmids contributed to the spread and persistence of vancomycin resistance among E. faecium. Horizontal gene transfer events among genetic elements from different clonal lineages (same or different species) result in chimeras with different stability and host range, complicating the surveillance of epidemic plasmids. © The Author 2016. Published by Oxford University Press on behalf of the British

MATE (Mentale Aspecten van Team Effectiviteit) (MATE (Mental Aspects of Team Effectiveness))

DTIC Science & Technology

2008-05-01

0 Auteur (s) drs. J.P. van Meer drs. MI. 1 ’ IIart0 drs. 1. van der 16. Rubricering rapport Ongerubriceerd Vastgesteld door Ikol drs. L.A. de Vos...team Auteur (s) Teamntraining drs. J.P. van Meer drs. M.H.E. I Hart Programmanummer Projectnummer drs. 1. van der Beijl V406 015.34095 Rubricering...Murphy & Cleveland (1995) geven inzicht in de tearngedragingen die meetbaar zijn en de theorie over Shared Mental Models (Espevik et al, 2006) laat zien

Isotope separation by photodissociation of Van der Waal's molecules

DOEpatents

Lee, Yuan T.

1977-01-01

A method of separating isotopes based on the dissociation of a Van der Waal's complex. A beam of molecules of a Van der Waal's complex containing, as one partner of the complex, a molecular species in which an element is present in a plurality of isotopes is subjected to radiation from a source tuned to a frequency which will selectively excite vibrational motion by a vibrational transition or through electronic transition of those complexed molecules of the molecular species which contain a desired isotope. Since the Van der Waal's binding energy is much smaller than the excitational energy of vibrational motion, the thus excited Van der Waal's complex dissociate into molecular components enriched in the desired isotope. The recoil velocity associated with vibrational to translational and rotational relaxation will send the separated molecules away from the beam whereupon the product enriched in the desired isotope can be separated from the constituents of the beam.

De Ontwikkeling van een PBPK Model voor VX; Stand van Zaken V013-813 en 207C (The Development of a PBPK Model for VX: Status Report)

DTIC Science & Technology

2006-02-01

ing. H.C. Trap, dr. ir. M.J. van der werd zes maal gesproken over de Schans, ing. L.F. Chau, B.). Lander, invulling en de voortgang van het I.A. Cordia ...dr. ir. M.J. van der Schans, ing. L.F. Chau, J.P. Oostdijk, B.J. Lander, l.A. Cordia 25 TNO Defensie en Veiligheid, vestiging Rijswijk, Marketing en

Electrons in the Inner Van Allen Belt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reeves, Geoff

A recent study shows that the inner Van Allen belt has less radiation than previously believed. Observations from NASA’s Van Allen probes show the fastest, most energetic electrons in the inner radiation belt are actually much rarer and harder to find than scientists expected. This is good news for spacecraft that are orbiting in the region and can be damaged by high levels of radiation. The results will also help scientists better understand—and detect—effects from high-altitude nuclear explosions.

Effects of geometrical frustration on ferromagnetism in the Hubbard model on the generalised Shastry-Sutherland lattice

NASA Astrophysics Data System (ADS)

Farkašovský, Pavol

2018-05-01

The small-cluster exact-diagonalization calculations and the projector quantum Monte Carlo method are used to examine the competing effects of geometrical frustration and interaction on ferromagnetism in the Hubbard model on the generalised Shastry-Sutherland lattice. It is shown that the geometrical frustration stabilizes the ferromagnetic state at high electron concentrations ( n ≳ 7/4), where strong correlations between ferromagnetism and the shape of the noninteracting density of states are observed. In particular, it is found that ferromagnetism is stabilized for these values of frustration parameters, which lead to the single-peaked noninterating density of states at the band edge. Once, two or more peaks appear in the noninteracting density of states at the band edge the ferromagnetic state is suppressed. This opens a new route towards the understanding of ferromagnetism in strongly correlated systems.

Relating Seismicity to Dike Emplacement, and the Conundrum of Dyke-Parallel Faulting

NASA Astrophysics Data System (ADS)

Dering, G.; Micklethwaite, S.; Cruden, A. R.; Barnes, S. J.; Fiorentini, M. L.

2016-12-01

Seismic monitoring shows that faulting and fracturing precede and accompany magma emplacement on timescales of hours and days. One outstanding problem is that the precision of earthquake hypocentre locations is typically limited to tens or hundreds of meters and cannot resolve whether the hypocentres relate to strain of wall rock fragments within the dikes, in a process zone around the intrusion or peripherally in the country rock. We examine a swarm of 19 dolerite dikes, near Albany, Western Australia using an unmanned aerial vehicle and Structure-from-Motion photogrammetry to obtain accurate, high resolution 3D reconstructions of outcrop and to digitally extract structural data. We find rare overprinting relationships indicate dike emplacement and faulting was coeval and that the number of faults/fractures increase into the dike swarm (2.2 ± 0.7 more fractures, per unit length in host rocks intruded by dikes relative to the background value). The faults are cataclasite-bearing and parallel to the dikes but intriguingly dike emplacement appears to have been accommodated by mode 1 extension. We further provide the first evidence that dike-parallel shear failure occurs in a damage zone associated with the dike swarm. These results support seismological observations of dike-parallel shear failure associated with some intrusion events, which contradict Mohr-Coulomb theory and numerical modelling of dike propagation in brittle-elastic rock, where shear failure is predicted to occur on faults oriented approximately 30° to the dyke plane. We suggest the dike swarm occupies a network of joints and fractures formed prior to swarm emplacement but then reactivated ahead of propagating dikes and remaining active during the early stages of emplacement.

Energy Sources for Soldier Modernisation Programme Systems (Overzicht van Ontwikkelingen op het Gebied van Draagbare Energieopslag en Energieopwekking)

DTIC Science & Technology

1999-12-01

9 . http://home.earthlink.net/-fradella/homepage.htm 10. http ://web.mit.edu/aeroastro/www/labs/GTL/research/micro/micro.html 11 . http://www.ecr.co.il...Meijer 7 LAS/DB&P/BO/OB&T taxv. aooi Jansen 8 LAS/DB&PIBO/OB 9 LAS/DB&P/BO/CIV 10 OGMAN/Externe plannen Infanterie 11 DM/C31 12 DM/COM 13 KPU-bedrijf 14...detailed specifications mentioned before. TNO-rapport TNO-MEP - R 99/490 9 van 51 Samenvatting In dit rapport wordt een eerste globale selectie gemaakt: van

The research contributions of Dr. Paul Van Deusen

Treesearch

Thomas B. Lynch; Francis A. Roesch; John Paul McTague; Jeffrey H. Gove; Gregory A. Reams; Aaron R. Weiskittel

2015-01-01

Dr. Paul Van Deusen’s recent passing concluded a rich 30+-year research career dedicated to development and implementation of quantitative methods for forestry and natural resources. Since the early part of his career as a biometrician with the USDA Forest Service Southern Research Station in the 1980s-1990s and continuing with his later employment at NCASI, Dr. Van...

Mapping Van

NASA Technical Reports Server (NTRS)

1994-01-01

A NASA Center for the Commercial Development of Space (CCDS) - developed system for satellite mapping has been commercialized for the first time. Global Visions, Inc. maps an area while driving along a road in a sophisticated mapping van equipped with satellite signal receivers, video cameras and computer systems for collecting and storing mapping data. Data is fed into a computerized geographic information system (GIS). The resulting amps can be used for tax assessment purposes, emergency dispatch vehicles and fleet delivery companies as well as other applications.

Novel type of VanB2 teicoplanin-resistant hospital-associated Enterococcus faecium.

PubMed

Santona, Antonella; Paglietti, Bianca; Al-Qahtani, Ahmed A; Bohol, Marie Fe F; Senok, Abiola; Deligios, Massimo; Rubino, Salvatore; Al-Ahdal, Mohammed N

2014-08-01

Seven high-risk clones of vancomycin-resistant Enterococcus faecium (VREF) belonging to clonal complex 17 were identified using multilocus sequence typing (MLST) among clinical isolates from Saudi Arabia. Among these isolates, a new hospital-associated sequence type (ST795), VanB(2)-type teicoplanin-resistant strain was detected. Its unusual phenotype resulted from a new combination of mutations in the ddl, vanS and vanW genes, which confirmed the trend of evolution in VanB-type resistance. Furthermore, characteristics of adaptation and persistence in the hospital environment of ST795 were emphasised by the presence of genes and clusters recognised to be specific for hospital-associated VREF. Copyright © 2014 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

The influence of heterogeneity on coastal groundwater flow - physical and numerical modeling of fringing reefs, dykes and structured conductivity fields

NASA Astrophysics Data System (ADS)

Houben, Georg J.; Stoeckl, Leonard; Mariner, Katrina E.; Choudhury, Anis S.

2018-03-01

Geological heterogeneity of the subsurface, caused by both discrete features and spatially distributed hydraulic conductivity fields, affects the flow of coastal groundwater. It influences the shape and the position of the interface between saltwater and freshwater, as well as the location and flux rate of freshwater discharge to the ocean. Fringing reefs lead to a bimodal regime of freshwater discharge, with discharge at the beach face and through deeper, submarine springs. Impermeable vertical flow barriers (dykes) lead to an impoundment of fresh groundwater and a compartmentalization of the aquifer but also to a delayed expulsion of saline water. Spatially distributed conductivity fields affect the shape of the interface and the geometry of the saltwater wedge. Higher effective conductivities lead to a further landward intrusion of the wedge toe. These flow characteristics can be important for groundwater extraction, the delineation of protection zones and the assessment of contaminant transport to coastal ecosystems.

Materials perspective on Casimir and van der Waals interactions

NASA Astrophysics Data System (ADS)

Woods, L. M.; Dalvit, D. A. R.; Tkatchenko, A.; Rodriguez-Lopez, P.; Rodriguez, A. W.; Podgornik, R.

2016-10-01

Interactions induced by electromagnetic fluctuations, such as van der Waals and Casimir forces, are of universal nature present at any length scale between any types of systems. Such interactions are important not only for the fundamental science of materials behavior, but also for the design and improvement of micro- and nanostructured devices. In the past decade, many new materials have become available, which has stimulated the need for understanding their dispersive interactions. The field of van der Waals and Casimir forces has experienced an impetus in terms of developing novel theoretical and computational methods to provide new insights into related phenomena. The understanding of such forces has far reaching consequences as it bridges concepts in materials, atomic and molecular physics, condensed-matter physics, high-energy physics, chemistry, and biology. This review summarizes major breakthroughs and emphasizes the common origin of van der Waals and Casimir interactions. Progress related to novel ab initio modeling approaches and their application in various systems, interactions in materials with Dirac-like spectra, force manipulations through nontrivial boundary conditions, and applications of van der Waals forces in organic and biological matter are examined. The outlook of the review is to give the scientific community a materials perspective of van der Waals and Casimir phenomena and stimulate the development of experimental techniques and applications.